energies

Article
Application of a Bidirectional DC/DC Converter to Control the
Power Distribution in the Battery–Ultracapacitor System
Adrian Chmielewski 1, * , Piotr Piórkowski 1 , Krzysztof Bogdziński 1 and Jakub Możaryn 2

1 Institute of Vehicles and Construction Machinery Engineering, Warsaw University of Technology,

Narbutta 84 Str., 02-524 Warsaw, Poland
2 Institute of Automatic Control and Robotics, Warsaw University of Technology, Sw. A. Boboli 8,
02-525 Warsaw, Poland
* Correspondence: adrian.chmielewski@pw.edu.pl; Tel.: +48-22-234-8118

Abstract: The article presents the use of the Texas Instruments LM5170EVM-BIDIR bidirectional
DC/DC converter to control power distribution in a hybrid energy storage system based on a
battery–ultracapacitor system. The paper describes typical topologies of connecting a battery with
an ultracapacitor. The results of tests for calibration and identification of converter parameters are
presented. The main innovation of the solution presented in this paper is the appropriate selection of
the nominal voltage of the ultracapacitor so that the converter can be operated only in the constant
current mode, in a cascade connection, excluding the low-efficiency constant voltage mode. This
article demonstrated that such control allows for high efficiency and reduction of losses in the DC/DC
converter, which is necessary in the case of mobile solutions. The amount of losses was determined
depending on the control voltage in the operation modes of the converter: in the Step Up mode by
increasing the voltage from 12 V to 24 V, from 12 V to 36 V, and from 12 V to 48 V and in the Step
Down mode by decreasing the voltage from 48 V to 12 V, from 36 V to 12 V, and from 24 V to 12 V).
For a calibrated converter in a semi-active topology, bench tests were carried out in a cycle with
pulsating load. The tests were carried out using LiFePO4 cells with a voltage of 12 V and Maxwell
ultracapacitors with a package voltage of 48 V. Power distribution in the range of 10% to 90% was
Citation: Chmielewski, A.; achieved using the myRIO platform, which controlled the operation of the DC/DC converter based
Piórkowski, P.; Bogdziński, K.; on an external current profile.
Możaryn, J. Application of a
Bidirectional DC/DC Converter to Keywords: bidirectional DC/DC converter; semi-active topology; LiFePO4; ultracapacitor
Control the Power Distribution in the
Battery–Ultracapacitor System.
Energies 2023, 16, 3687. https://
doi.org/10.3390/en16093687
1. Introduction
Academic Editor: Ramon 1.1. Literature Review
Costa-Castelló Currently, in order to counteract progressive climate change, the European Green
Received: 29 March 2023 Deal [1] was established, which assumes in 2050 to achieve net-zero greenhouse gas
Revised: 18 April 2023 emissions through the development of, i.a., sustainable and intelligent mobility [1]. It is
Accepted: 23 April 2023 assumed that by 2030 there will be at least 30 million electric vehicles in the EU that will be
Published: 26 April 2023 charged at three million public ultra-fast charging points in the DC CHAdeMO 3.0 (ChaoJi)
standard [2,3], 900 kW power value in accordance with IEC 61851-23:2014 [4]. It is worth
emphasizing that in the EU region, the transport sector is responsible for nearly 25% of
greenhouse gas emissions, of which 71% are road transport [5].
Copyright: © 2023 by the authors. Another key element supporting the achievement of climate neutrality is the sustain-
Licensee MDPI, Basel, Switzerland. able development of renewable energy sources (RES). EU countries have agreed on specific
This article is an open access article
targets regarding total share of RES in final energy consumption mix in the coming years,
distributed under the terms and
achieving 32% by 2030 [6] or up to 45% [7]. These values include renewable energy used
conditions of the Creative Commons
for heating and cooling, transport, and electricity production, among others.
Attribution (CC BY) license (https://
It should be mentioned that the regulations oblige the EU member states to simul-
creativecommons.org/licenses/by/
taneous development of facilities and techniques for electricity storage, mainly for the
4.0/).

Energies 2023, 16, 3687. https://doi.org/10.3390/en16093687 https://www.mdpi.com/journal/energies

Energies 2023, 16, 3687 2 of 40

purposes of stabilization of the power system [7], development of prosumer systems [8],
development of alternative fuel infrastructure for vehicles (in particular, those with electric
drive [9], and connection of RES with the main power grid [7].
Considering the above, particular attention should be paid to electricity storage fa-
cilities [10] with high volumetric energy (batteries [11]) and power density (ultracapaci-
tors [12]).
Ultracapacitors and batteries are used in trucks [13] as well as vehicles with purely
electric drives, i.e., components of the drive system of ChariotMotors battery electric
buses [13] and ultracapacitor buses [14]. They are also key elements for Gemamex Motion
Co. Bulgaria Sofia charging stations (power range up to 250 kW [13]).
In a certain group of devices and energy receivers, especially for means of transport,
the load is strongly dynamic/pulsating and variable in time, which was pointed out in [10].
As a result, the peak power of the load is much higher than the average load [15]. In [12], it
was shown that this is a key problem from the point of view of the selection of the energy
source because, on the one hand, the source must provide temporarily high peak load
power, and, on the other hand, it must provide the right amount of energy. The simplest
solution, presented in [12], in this case is the use of a sufficiently large energy storage—a
large storage capacity ensures both the appropriate peak power and sufficient energy
reserve. Unfortunately, such a solution is large, expensive, and heavy, and in the case of
mobile solutions, it is often impossible to use.
As described in [12,16], an alternative is the use of hybrid energy storage (HES). It
usually consists of two components—a high power source, the so-called “high power”,
which is an ultracapacitor, and energy sources, the so-called “high energy”, which is an
electrochemical battery. In this way, the optimized hybrid energy source is much lighter
than a large energy storage while performing the same tasks [17,18].
Another example of the need to use an HES based on a battery and an ultracapacitor
may be starting an internal combustion engine in difficult conditions [19].
Examples of such conditions are low ambient temperature [20], long breaks in engine
operation [12], pulsed load [19], significant battery load at standstill to power on-board elec-
trical devices (including the dashboard [12]), and in the start/stop systems [21] of vehicles.
In the case of the latter for the electrochemical battery technology [22], the high frequency
of system operation—frequent engine starts and short battery charging periods—mean
that the battery discharges faster in such dynamic conditions [23], and its usable capacity
and lifetime decrease [12]. Moreover, the battery parameters significantly deteriorate [24],
i.a., the internal resistance of the battery increases [25] (in particular the electrolyte resis-
tance [26]), the open circuit voltage [27], and the voltage at the terminals decreases [28].
During the start-up of internal combustion engines in such conditions, the mechanical
resistance associated with increased density of engine oil also increases significantly [12],
while the power and energy availability are reduced, which translates into a higher battery
load and reduces its service life [29] and state of health [30–38]. The other disadvantages
of batteries include self-discharge [31] and difficulty in early detection of impending bat-
tery discharge (often the battery is completely discharged suddenly [39] without warning
signs [40]). Elimination of the described battery disadvantages can be achieved by parallel
connection of the battery and ultracapacitor [41]. The properties of ultracapacitors [42]
and electrochemical batteries [43] are complementary. By connecting these components in
parallel, a system that combines the benefits of both of these energy stores can be achieved.
It should be emphasized that a set of parallel connected ultracapacitors and electrochemical
batteries features high energy [44] at the same time, which is caused by the battery. Such a
set also features high power [12], which is caused by the influence of ultracapacitors [44].
Thanks to the use of ultracapacitors, the available power range is also increased, including
at low temperatures [40] and at low charge levels [39].
The use of a parallel connection of the battery and the ultracapacitor makes it possible
to increase the availability of the stored energy [12], even in the case of a voltage drop of the
hybrid system to a value indicating complete discharge of the battery, which corresponds
Energies 2023, 16, 3687 3 of 40

to SoC = 0 [45]. It is worth emphasizing that the amount of energy stored at this voltage in
the ultracapacitor still allows starting the internal combustion engine [12]. The presented
situation may occur in the case of vehicles used infrequently, occasionally, or in cold
climates [40]; in particular, official, special vehicles [46]; as well as vehicles with increased
load [47] on the DC electrical system [48], such as city buses [13]. In Poland, city buses [13],
usually at the end of the line [14], must remain stationary with the engine switched
off [49] while there is still a significant energy load inside them through such receivers
as information boards and LCD boards, interior lighting, passenger space heating, or
air conditioning.
When the vehicle is not used for a long time, the self-discharge [12] occurring in both
ultracapacitors and traction batteries plays an important role, according to the subject data,
amounting to several percent per month for a battery [31] and up to 30% per month for an
ultracapacitor [20,50], respectively. This is of particular importance within the drive system
of an electric vehicle [51].
An example is the fifth-generation BMW drive system with bidirectional DC/DC
converter [52], in which the 12 V low-voltage system is responsible for switching on the
400 V high-voltage system. In the event of self-discharge of the low-voltage system, in
extreme cases, when the vehicle is not used for a long time, for a year or more, it is necessary
to recharge the low-voltage side battery and high-voltage side battery pack from an external
charger or from a PV module. It is worth mentioning that the self-discharge process [31]
can be reduced by adding PV modules to the system [53–55].
The next example where there is a need to use batteries and supercapacitors to store
electricity are the decks of innovative electric airplanes, presented in [56–60]. Additional
storage devices such as supercapacitors and batteries have been widely sought in the
innovative field of aircraft electrification in recent decades. In [56], a topology similar to
that shown in Section 1.2, parallel active hybrid BES-UC connection was adopted to achieve
a dual objective: to enforce a power-sharing policy between the aircraft’s main generator
and the auxiliary battery and to preserve the condition of the aircraft’s mechanical parts
of the generator by using a supercapacitor to absorb/provide power peaks in the main
power grid. In addition, as shown in this work, the supercapacitor can also work as an
energy storage system, supplying constant power to the grid. In reference [57], similar to
the topology shown in scheme of the DC/DC converter test stand, with measurements in
Step Down mode, the supercapacitor is connected to the power peak absorption/supply
grid by a bidirectional DC/DC converter controlled by a SubOptimal second-order sliding-
mode controller.
However, in the HES there is a new problem of proper power distribution [61] between
the high-power source (ultracapacitor) and the high-energy source (electrochemical battery).
Power distribution is carried out by a suitably controlled DC/DC converter [62,63]. To
protect the batteries against deep discharge [64], a bidirectional DC/DC converter [65] is
required to raise the output voltage of the ultracapacitor to a level safe for the battery [66].
In typical applications, the high power source supplies power directly to the receiver,
and its charge is then replenished over a longer period of time from the high energy source
via the converter [67]. In this way, the high energy source is loaded with a lower current
value, but for a longer time, which has a very positive effect on its durability [68], especially
in the case of Li-ion batteries [69].
As was shown in [70,71], in an HES, the efficiency of not only the high energy and high
power sources but also the component connecting both sources, i.e., the DC/DC converter,
should be considered.
In several works [61,66,68,70–73], it was shown that the DC/DC converter cannot be
too large and oversized, but, at the same time, its power should be sufficiently high to be
able to effectively and relatively quickly balance the charge level of the high power source.
Insufficient power of the DC/DC converter does not allow it to effectively recharge the
high power source within the specified time limit. On the other hand, a converter with too
much power is heavy, expensive, and requires additional cooling, which was pointed out
 In several works [61,66,68,70–73], it was shown that the DC/DC converter cannot be
too large and oversized, but, at the same time, its power should be sufficiently high to be
able to effectively and relatively quickly balance the charge level of the high power source.
Insufficient power of the DC/DC converter does not allow it to effectively recharge the
Energies 2023, 16, 3687 high power source within the specified time limit. On the other hand, a converter with4 too of 40
much power is heavy, expensive, and requires additional cooling, which was pointed out
in [70]. At the same time, excessive current from an oversized converter may adversely
affect theAt
in [70]. durability
the sameoftime,
the high-energy sourcefrom
excessive current [44,70]. From thisconverter
an oversized point of view,
may the selec-
adversely
tion of the
affect a DC/DC converter
durability of the is not a trivialsource
high-energy task and should
[44,70]. Frombe this
made on the
point basis the
of view, of in-depth
selection
analyses
of a DC/DC of a specific
converterapplication.
is not a trivial task and should be made on the basis of in-depth
analyses of a specific
The primary application.
objective of the research presented in this paper is to investigate the
The primary
feasibility of using objective of the DC/DC
a bi-directional researchconverter
presentedtoinmanage
this paper
power is to investigateinthe
distribution a
feasibility of using a bi-directional DC/DC converter to manage power
hybrid energy storage system that utilizes a battery–ultracapacitor setup for mobile ap- distribution in
a hybrid energy
plications. storagesolution
The proposed system comprises
that utilizestwo a components:
battery–ultracapacitor setup forand
topology selection mobile
cal-
applications.
ibration The proposed
methodology. solutionselection
The topology comprises two
aims to components:
determine thetopology selectionvolt-
optimal nominal and
calibration
age methodology.toThe
of the ultracapacitor topology
enable selectiontoaims
the converter to determine
operate solely in thethe constant
optimal nominal
current
voltage
mode and ofaccommodate
the ultracapacitor to enable
the current the converter
external to operate
profile (ECP). solely in cascade
The semi-active the constant
con-
current mode and accommodate the current external profile (ECP). The
nection described in this solution eliminates the need for the low-efficiency constant volt-semi-active cascade
connection
age described
mode, resulting in in this solution
greater efficiency eliminates
and reducedthe need
lossesfor
in the
the low-efficiency
DC/DC converter. constant
Ad-
voltage mode, resulting in greater efficiency and reduced losses in the DC/DC
ditionally, the study endeavors to identify the level of losses based on the control voltage converter.
Additionally,
in the study
the converter’s endeavors
operational to identify
modes the levelbench
and conduct of losses based
tests withonpulsating
the control voltage
loads to
in the converter’s
achieve operational
power distribution modes10%
between andand
conduct
90%. bench tests with
The DC/DC pulsating
converter’s loads to
operation
achievebepower
should distribution
regulated based onbetween
the ECP 10% and 90%.
designated Thethe
during DC/DC converter’s
calibration phase. operation
should be regulated based on the ECP designated during the calibration phase.
1.2. Contribution of the Paper
1.2. Contribution of the Paper
In the conducted research presented in this article in Section 2, it was shown that the
In the conducted research presented in this article in Section 2, it was shown that
efficiency of the converter strongly depends on its load. The efficiency of the DC/DC con-
the efficiency of the converter strongly depends on its load. The efficiency of the DC/DC
verter is higher for power close to the nominal value. At the same time, the efficiency of
converter is higher for power close to the nominal value. At the same time, the efficiency
the converter is very low for fractional power. Hence, the important conclusion is that the
of the converter is very low for fractional power. Hence, the important conclusion is that
converter should work as much as possible with the highest power, i.e., in the constant
the converter should work as much as possible with the highest power, i.e., in the constant
current
current(CC)
(CC)charging
charging mode,
mode, which
which has
has been
been demonstrated
demonstrated in in this
this article.
article.
This article is structured as follows. Section 2 presents the
This article is structured as follows. Section 2 presents the procedureprocedure forfor calibrating
calibrating the
the
bidirectional DC/DC converter for later use in power distribution control in an in
bidirectional DC/DC converter for later use in power distribution control HESan based
HES
based on a battery
on a battery and an and an ultracapacitor.
ultracapacitor. This This section
section also also presents
presents powerpower
lossloss character-
characteristics
istics in different
in different controlcontrol modes.
modes. The The configuration
configuration andand description
description of the
of the testtest stand
stand with
with the
the DC/DC converter, which was placed between the ultracapacitor and the
DC/DC converter, which was placed between the ultracapacitor and the battery in the semi- battery in the
semi-active topology,
active topology, is alsoispresented
also presented (see Figure
(see Figure 1d). Section
1d). Section 3 presents
3 presents theof
the results results of
research
research on different values of power distribution in an HES based on a battery
on different values of power distribution in an HES based on a battery and an ultracapacitor and an
ultracapacitor
in a semi-active intopology
a semi-active
with atopology with a DC/DC
DC/DC converter. converter.
Finally, Section 4Finally,
provides Section 4 pro-
the synthetic
vides
view the synthetic
of the view of the conclusions.
conclusions.

(a) (b) (c) (d)

Figure 1. (a) Physical model of BES-UC system (topology of parallel passive connection), (b) topol-
Figure 1. (a) Physical model of BES-UC system (topology of parallel passive connection), (b) topology
ogy of semi-active connection with DC/DC converter located directly in front of the battery, (c)
of semi-active connection with DC/DC converter located directly in front of the battery, (c) topology of
topology of semi-active connection with DC/DC converter located directly in front of ultracapaci-
semi-active
tor, connection
(d) topology with DC/DC
of semi-active converter
cascade located
connection withdirectly
DC/DC inconverter
front of ultracapacitor, (d) topology
between the ultracapac-
of semi-active cascade
itor and the battery. connection with DC/DC converter between the ultracapacitor and the battery.

2. Materials and Methods

2.1. Battery and Ultracapacitor Connection Topologies
This subsection presents the battery–ultracapacitor connection topologies [18,74,75].
As indicated in scientific papers [18,44,48,51,66,70,71], the following connection topologies
of both components are most common: passive, semi-active, and active. Such topologies
are presented in Figure 1.
Energies 2023, 16, 3687 5 of 40

The easiest to implement is the parallel connection in the passive topology (Figure 1a),
where the battery and the ultracapacitor are physically connected in parallel with each
other [44]. In such a connection [75], there is no control of the power distribution between
the battery and the ultracapacitor, and the voltage that is set at the terminals of the HES
system is the resultant [18].
As presented in [44,48,61,64], the semi-active topology means that one energy storage
is connected directly to the energy source/receiver, while the other energy storage can
partially participate in the energy expenditure through an adjustable DC/DC converter.
Mostly, in the scientific literature [18,44,61], there are semi-active solutions with one
converter located in front of the ultracapacitor (Figure 1b) or the battery (Figure 1c). When
the converter is placed in front of the ultracapacitor (Figure 1b), the battery is directly
connected to the DC bus. One of the main disadvantages of such a solution is greater
voltage oscillation at the battery terminals due to higher current loads, which directly
affects the life of the cells. During high current loads, electrodynamic forces appear on the
cells, which affect the change of stresses inside the cell and faster degradation of the active
material [76]. In the second case, when the battery is separated from the DC bus by the
DC/DC converter (Figure 1c), it operates in optimal ranges (currents do not exceed the
limit values [44]), while the uninsulated ultracapacitor takes over voltage and frequency
fluctuations in the DC bus [64]. In order to eliminate voltage fluctuations, it is necessary to
use ultracapacitors with higher capacitances in the system, which directly translates into
higher system costs.
This paper presents a semi-active topology where a DC/DC converter is placed
between an ultracapacitor connected directly to the DC line and a battery (see Figure 1d).
The topology shown in Figure 1d was used to carry out the experimental studies in Section 3.
In this topology, the converter should work with the highest power as far as possible,
i.e., in the constant current (CC) charging mode. Operation in the constant voltage (CV)
charging mode by definition limits the value of the charging current and consequently
reduces the efficiency of the converter and increases energy losses. Therefore, the CV mode
should be limited and preferably not used at all. The conducted tests have shown that the
condition for limiting losses and high efficiency of the converter operation is its operation
only in the CC mode, bypassing the CV mode (see Section 2.2). A similar advantage for the
semi-active topology was pointed out in [62,68,77], where the ultracapacitor is connected
directly to the DC bus.
The consequence of using only the CC mode is the risk of undercharging the high
power source, which was pointed out in [68]. The laboratory tests presented in this article
show that this problem can be solved by appropriate selection of the nominal voltage of the
high power source to the voltage in the DC bus line (see Figure 1d). In a situation where
the nominal voltage of the high power source is sufficiently higher than the voltage in the
DC bus line, then the high power source can be easily recharged with full power only in
the CC mode, bypassing the CV mode. In this way, the DC/DC converter works with the
highest efficiency all the time, which was pointed out in [68,77]. The topology shown in
Figure 1d was used to carry out the experimental studies in Section 3.
Another approach is a parallel active connection topology via bidirectional DC/DC
converters (Figure 2a). In such a system, it is possible to assign active power distribution
using a specific control strategy, e.g., in the areas of the highest battery efficiency in the
SoC range from 0.2 to 0.9 (possible power distribution from 0% to 100% between both
components), as shown in the works [18,70,78]. Two DC/DC converters have been used in
network applications. In this configuration, the converter can be programmed in such a way
that the ultracapacitor reacts to short-term and high voltage spikes with high frequency [75]
while regulating the voltage on the DC/DC bus [44]. The battery can provide energy for
low frequencies with small voltage amplitudes for small values of current loads, e.g., up
to several C, which is described in the works [65,70,75]. In the active cascade connection
topology (Figure 2b), two DC/DC converters are used, which isolate the ultracapacitor and
the battery from the DC bus.
 suming. It is particularly important during intermittent operation when connecte
newable sources, e.g., wind farms or photovoltaic modules, which has been high
in the works [55,77,79]). The second converter, which isolates the ultracapacitor (U
the DC bus, is voltage controlled. Its purpose is to stabilize the voltage in the DC
absorb high frequencies in the network. As a result of the use of two converters, th
Energies 2023, 16, 3687 6 of 40
higher power losses in the system associated with multiple energy conversion, wh
pointed out in [64,70].

(a) (b)
Figure
Figure 2. (a) Topology of 2. (a) Topology
parallel of parallel
active hybrid activeconnection,
BES-UC hybrid BES-UC connection,
(b) topology (b) topology
of cascade active of cascad
connection
connection of BES-UC system. of BES-UC system.

2.2.which
The converter, DC/DCisConverter
located inCalibration
front of the battery, is usually current controlled to
ensure a smooth exchange
The main purpose ofthe
of energy with thebattery [44].
research wasSuch control
to select theallows
controlformethod
resigna-and the n
tion from the complicated charging process (especially in the case of Li-ion batteries
voltage of the ultracapacitor module so that the converter could operate [34,35]),in the C
where various charging
with theconditions should beIn
highest efficiency. taken into[68,77,79–81],
papers account in order to fully
it was charge the
emphasized that the lo
cell. Normally, the charging process takes place in two phases: I—constant current CC, and
affected not only by the current but also by the voltage difference at the input and
II—constant voltage
of theCV. In the CV
converter. charging
When phasean
designing application
HES with of the voltage
a DC/DC equalizing
converter, these charac
is required, carried out through passive or active balancing, which is time-consuming.
of power losses should be taken into account to decide when there are benefits from
It is particularlythe
important
converterduring intermittent
(despite the losses)operation
and when when connected
it is more to renewable
effective to cover the entire
sources, e.g., wind
demand without the use of the converter, as shown in [70,77,80,81]. in
farms or photovoltaic modules, which has been highlighted Forthe
this purpo
works [55,77,79]). The second converter, which isolates the ultracapacitor (UC) from the
power prototype systems are built with the demonstrative use of DC/DC converte
DC bus, is voltage controlled. Its purpose is to stabilize the voltage in the DC bus and
Table 1 shows the parameters of bidirectional DC/DC converters in low-pow
absorb high frequencies in the network. As a result of the use of two converters, there are
tems and prototype systems presented in [77,80–90] as well as the parameters of th
higher power losses in the system associated with multiple energy conversion, which was
Instruments LM5170EVM-BIDIR DC/DC converter [91] analyzed in this article.
pointed out in [64,70].

2.2. DC/DC Converter Calibration

The main purpose of the research was to select the control method and the nominal
voltage of the ultracapacitor module so that the converter could operate in the CC mode
with the highest efficiency. In papers [68,77,79–81], it was emphasized that the losses are
affected not only by the current but also by the voltage difference at the input and output
of the converter. When designing an HES with a DC/DC converter, these characteristics of
power losses should be taken into account to decide when there are benefits from using
the converter (despite the losses) and when it is more effective to cover the entire energy
demand without the use of the converter, as shown in [70,77,80,81]. For this purpose,
low-power prototype systems are built with the demonstrative use of DC/DC converters.
Table 1 shows the parameters of bidirectional DC/DC converters in low-power sys-
tems and prototype systems presented in [77,80–90] as well as the parameters of the Texas
Instruments LM5170EVM-BIDIR DC/DC converter [91] analyzed in this article.
The power of the bidirectional DC/DC converters presented in Table 1 does not
exceed 1 kW, while the efficiency is above 90% both in the Step Up and Step Down modes.
Additionally, for the converter analyzed in this paper, the value of power losses does not
exceed 10%, which has been analyzed in detail and shown in Sections 2.2.1 and 2.2.2.
Energies 2023, 16, 3687 7 of 40

Table 1. Technical data comparison of low power bidirectional DC/DC converters presented in papers [80–90] and DC/DC converter presented in this paper [91].

DC/DC DC/DC DC/DC DC/DC DC/DC DC/DC DC/DC DC/DC DC/DC DC/DC DC/DC
This Paper
Parameter Converter in Converter in Converter in Converter in Converter in Converter in Converter in Converter in Converter in Converter in Converter in
[91]
[80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90]
The number
of 6 4 2 4 10 4 6 3 6 4 4 4
switches
The number
0 - - 0 0 0 0 0 0 3 4 2
of diodes
The number
4 2 3 6 3 2 3 1 4 3 4 2
of capacitors
Number of
1 2 2 1 1 1 1 1 1 2 2 1
inductors
Input voltage from 6 V to
24–58 V 24 V 12–20 V 24–48 V 35–50 V 40 V 24–55 V 48 V 48 V 48 V 35 V
Vin 75 V
Output
400 V 200 V 60–70 V 360 V 400 V 400 V 400 V 380 V 384 V 400 V 285 V 12–48 V
voltage Vout
Bidirectional yes yes Yes yes yes yes yes yes yes yes yes Yes
Efficiency of
Presented in
Step Down 95% 94% 94.2% 93% 94% 94% 94% 95% 96% 95% 90%
this paper
mode [%]
Efficiency of
Presented in
Step Up 96% 95% 94.2% 94% 94% 94% 96% 94% 96% 95% 90%
this paper
mode [%]
Boost or
buck yes yes yes yes yes yes yes yes yes yes yes yes
operation
Up to 750 W
Rated power
1000 W 500 W 120 W 250 W 1000 W 300 W 500 W 300 W 250 W 400 W 140 W or 500 W per
[W]
channel
Switching
700 kHz 350
frequency 40 kHz 50 kHz 50 kHz 100–145 kHz 50 kHz 40 kHz 100 kHz 50 kHz 100–180 kHz 30 kHz 50–500 kHz
kHz–1 MHz
[kHz]
PWM control
normal normal normal normal complex normal normal normal normal complex normal normal
signals
 Energies 2023, 16, 3687 8 of 40

The aim of the measurements was to determine the operating characteristics and to
define the rules and operating procedures for the Texas Instruments DC/DC converter
module, model LM5170EVM-BIDIR (Figure 3). The calibrated converter was used on a
ergies 2023, 16, x FOR PEER REVIEW dedicated laboratory stand which is described in detail in Section 2.2.1, Section
8 of 40 2.2.2, and
Section 2.3.

Figure 3. Texas Instruments DC/DC converter, LM5170EVM-BIDIR model [91].

Figure 3. Texas Instruments DC/DC converter, LM5170EVM-BIDIR model [91].

Initial identification tests weretests

Initial identification carried
wereout on aout
carried testonstand
a testenabling powerpower
stand enabling supply,
supply, with
with load and measurement of current and voltage values on the high- and low-voltage
load and measurement of current and voltage values on the high- and low-voltage side of
side of the the
DC/DC
DC/DCconverter. The The
converter. test test
stand was was
stand equipped with:
equipped with:
 TTI CPX400DP
• programmable
TTI CPX400DP DC power DC
programmable supply
power (PSU);
supply (PSU);
 TTI LD400P
• programmable DC load (LOAD);
TTI LD400P programmable DC load (LOAD);
 National
• Instruments CompactDAQ
National Instruments 9174 recording
CompactDAQ 9174 device,
recordingequipped
device,with an analog
equipped with an analog
input card input
NI 9206
card(cDAQ);
NI 9206 (cDAQ);
 National
• Instruments myRIO controller
National Instruments myRIO to control the
controller operation
to control the of the DC/DC
operation con-
of the DC/DC con-
verter; verter;
 Texas •Instruments bidirectional
Texas Instruments DC/DC converter
bidirectional DC/DC module,
convertermodel
module, LM5170EVM-
model LM5170EVM-
BIDIR; BIDIR;
 PICO •TA018 current-voltage
PICO convertersconverters
TA018 current-voltage (current clamps).
(current clamps).
CalibrationCalibration
of the DC/DC converter
of the DC/DCwas necessary
converter wastonecessary
determine to the characteristics
determine of
the characteristics of
its losses (different
its lossescurrents
(different and different
currents andinput and output
different voltages).
input and output As a consequence,
voltages). As a consequence,
the controltheof the converter
control of theoperation
converterwas selected,was
operation reducing these
selected, losses. During
reducing the cal-During the
these losses.
ibration ofcalibration
the converter, presented
of the converter,inpresented
Sections 2.2.1 and 2.2.2,
in Sections 2.2.1Maxwell
and 2.2.2,ultracapacitors
Maxwell ultracapacitors
were used.were used. Thedata
The technical technical data of ultracapacitors
of ultracapacitors and batteryandarebattery are in
presented presented
Table 2. in Table 2.

Table 2. Technical data

Table 2. of the LiFePO4
Technical battery
data of the and battery
LiFePO4 Maxwell ultracapacitor
and module. module.
Maxwell ultracapacitor

Battery[92]
Battery LiFePO4 LiFePO4 [92] Ultracapacitor BMOD0058
Ultracapacitor BMOD0058 E016E016
B02B02
[93][93]
Parameter NameParameter Name Value Value ParameterName
Parameter Name ValueValue
Nominal voltage 3.3 V Maximum rated voltage 16 V
Nominal voltage 3.3 V Maximum rated voltage 16 V
Minimum voltage Minimum voltage 2V 2V Minimum voltage
Minimum voltage 0V 0V
Maximum voltage Maximum voltage 3.6 V 3.6 V Absolute maximumvoltage
Absolute maximum voltage 17 V 17 V
Capacity Capacity 2.5 Ah 2.5 Ah Capacity
Capacity 58 F 58 F
Internal resistance 6 mΩ Initial equivalent series resistance 22 mΩ
Initial equivalent series re-
Internal resistance
Maximum discharge current 6 mΩ
70 A(cont.)/120 A Maximum continuous current 22 mΩ
23 A (cont.)/190 A
Dimensions (L × W × H, [mm]) Ø26 × 65 Dimensions (L sistance
× W × H, [mm]) 226.5 × 49.5 × 75.9
Maximum discharge cur-
Cycle life 70 A(cont.)/120
>1000 23 A
~5,000,000
Maximum continuous current
Weight rent 0.076 kg A Weight (cont.)/1900.63Akg
Dimensions (L × W × H, 226.5 × 49.5 ×
Ø26 × 65 Dimensions (L × W × H, [mm])
[mm]) 75.9
Cycle life >1000 ~5,000,000
Weight 0.076 kg Weight 0.63 kg

The acquired signals included voltage values on the low- and high-voltage sides of
the DC/DC converter, current values on the low- and high-voltage sides of the DC/DC
Energies 2023, 16, 3687 9 of 40

Energies 2023, 16, x FOR PEER REVIEW 9 of 40

The acquired signals included voltage values on the low- and high-voltage sides of
the DC/DC converter, current values on the low- and high-voltage sides of the DC/DC
converter, current consumed by the programmable load, and the control voltage of the
DC/DC converter.
DC/DC converter. Waveforms
Waveformsgenerated
generateddirectly from
directly fromTDMS
TDMS measurement
measurement filesfiles
are are
de-
scribed as follows:
described as follows:
• 12 12V V Voltage—voltage
Voltage—voltage onon the DC/DC
DC/DCconverter
converteron onthe
thelow-voltage
low-voltage side (nominal
side (nominal 12
V);V);
12
• 12 12VVCurrent—current
Current—currentflowing
flowingthrough
throughthe theDC/DC
DC/DCconverter
converteron onthe
thelow-voltage
low-voltageside side
(nominal12
(nominal 12V);
V);
• 48 48VV Voltage—voltage
Voltage—voltage on on the DC/DC
DC/DCconverter
converteron onthe
thehigh-voltage
high-voltage side (nominal
side (nominal 48
48
V);V);
• 48 48VVCurrent—current
Current—current flowing through
flowing throughthe the
DC/DC
DC/DC converter on the
converter onhigh-voltage
the high-voltageside
(48 V (48
side nominal);
V nominal);
• Total
TotalLOAD
LOADCurrent—value
Current—valueofofthe thecurrent
currentconsumed
consumedby bythe
theprogrammable
programmableload; load;
• DC DCControl
ControlVoltage—control
Voltage—controlvoltage
voltageofofthe theDC/DC
DC/DCconverter.
converter.
The
Thecalculated
calculated waveforms
waveforms ofof current,
current, power
power andand losses
losses as
as aa function
function of
ofthe
thecontrol
control
voltage
voltageofofthe
theDC/DC
DC/DC converter
converter have
have descriptions
descriptions consistent
consistent with
with the
the nominal
nominalvoltage
voltage
values
valuesfor
foraagiven
givenmeasurement
measurement(48 (48V,V,36
36V,V,and
and2424V).
V).

2.2.1.
2.2.1.Step
StepDown
DownMeasurements
Measurements(Buck
(BuckMode)
Mode)
This subsection describes the measurements
This subsection describes the measurementsof the
ofinverter in StepinDown
the inverter Step (Buck
DownMode).
(Buck
Figure 4 shows a diagram of the DC/DC converter test stand; the measurements were
Mode). Figure 4 shows a diagram of the DC/DC converter test stand; the measurements
carried out in the Step Down mode.
were carried out in the Step Down mode.

Figure4.4.Scheme
Figure Schemeof
ofthe
theDC/DC
DC/DC converter
converter test
test stand,
stand, with
with measurements
measurements in
in Step
Step Down
Down mode.
mode.

Measurementsfor
Measurements forthe
theoperation
operationofofthe theDC/DC
DC/DCconverter
converterininStep
StepDown/Buck
Down/BuckMode Mode
were
wereperformed
performedusingusingaaprogrammable
programmableload load(LOAD)
(LOAD)set setin
inconstant
constantvoltage
voltage(CV)(CV)mode
mode
holding 12 V on the low-voltage side of the DC/DC
holding 12 V on the low-voltage side of the DC/DC converter. converter.
During
During thethe preliminary tests,tests, the
thestart-up
start-upofofthethe system
system from
from thethe state
state of aoffully
a fully
dis-
discharged ultracapacitorwas
charged ultracapacitor wastaken
takeninto
intoaccount
accountforforthe
thedevelopment
development of of appropriate
appropriate proce-
proce-
dures
duresfor
forstarting
startingthetheconverter
converterand and estimating
estimating thethe
power
powerconsumption
consumption of the converter
of the in
converter
the idleidle
in the state. Figure
state. 5 shows
Figure the ultracapacitor
5 shows voltage
the ultracapacitor of the of
voltage 12 the
V side.
12 VThe voltage
side. equals
The voltage
0equals
V. To determine the measurement
0 V. To determine offset atoffset
the measurement the beginning of the calibration
at the beginning procedure,
of the calibration pro-
acedure,
preliminary
a preliminary measurement without load called “zero measurement” was Deter-
measurement without load called “zero measurement” was made. made.
mining the offset
Determining the in this in
offset step is particularly
this important
step is particularly for the current
important for the values
currentthat change
values that
the sign.the sign.
change
Energies 2023, 16, x FOR PEER REVIEW 10 of 40

Energies 2023, 16, x FOR PEER REVIEW 10 of 40

Energies 2023, 16, 3687 10 of 40

VHigh=48V
VLow=12V
[V] voltage [V]

V High [V]
V Low [V]

Voltage Side
Side
voltagecontol

Side VHigh=48V
VLow=12V
Voltage V LowVoltage

Voltage V HighVoltage
Side Voltage

[V]
[V]
DC/DC contolDC/DC

High VoltageHigh
Low Voltage Low

VHigh=48V
VLow=12V
[A] Current [A]

[A]
[A]

High
Low

Voltage Side
Side

Side VHigh=48V
I

I
VLow=12V
Current ILow Current

Current IHigh Current

Total Load

Side Voltage

[A]
[A]
Total Load Current

High VoltageHigh
Low Voltage Low

Figure 5. Waveforms of measured values—zero measurement.

In the
Figure next step,ofthe
5. Waveforms systemvalues—zero
measured was started, which is shown in Figure 6. The power sup-
measurement.
Figure 5. Waveforms of measured values—zero measurement.
ply to the system was started. The 48 V side of the converter was switched on, i.e., the
myRIO In the next step,
controller powerthe supply
system was
andstarted, which converter
the DC/DC is shown inmicroprocessor
Figure 6. The power supply
system power
to the system was started. The 48 V side of the converter was switched on, i.e., the myRIO sup-
In the next step, the system was started, which is shown in Figure 6. The power
supply (10 V power left off). The 48 V power supply indicated a current consumption of
ply controller
to the system
powerwas started.
supply The
and the 48 V converter
DC/DC side of the converter was
microprocessor switched
system power on, i.e., the
supply
0.02(10
A.V power left off). The 48 V power supply indicated a current consumption of 0.02 A.
myRIO controller power supply and the DC/DC converter microprocessor system power
supply (10 V power left off). The 48 V power supply indicated a current consumption of
0.02 A.
VHigh=48V
VLow=12V
[V] voltage [V]

[V]
V Low [V]

High
Side
Side
voltagecontol

V
VHigh=48V
VLow=12V
Voltage V LowVoltage

Voltage V HighVoltage
Side Voltage
Side Voltage

[V]
[V]
DC/DC contolDC/DC

High VoltageHigh
Low Voltage Low

VHigh=48V
VLow=12V
[A] Current [A]

[A]
[A]

High
Low

Side
Side

VHigh=48V
I

I
VLow=12V
Current ILow Current

Current IHigh Current

Total Load

Side Voltage
Side Voltage

[A]
[A]
Total Load Current

High VoltageHigh
Low Voltage Low

Figure 6. Waveforms of measured values—Step Down mode activating the 48 V side.

Figure 6. Waveforms of measured values—Step Down mode activating the 48 V side.
Then, the 10 V power supply of the converter logic was turned on (Figure 7). No
Then,inthe
change 10 V
power power supply
consumption of the converter logic was turned on (Figure 7). No
was observed.
Figure 6. Waveforms of measured values—Step Down mode activating the 48 V side.
change in power consumption was observed.
Then, the 10 V power supply of the converter logic was turned on (Figure 7). No
change in power consumption was observed.
Energies 2023, 16, x FOR PEER REVIEW 11 of 40
Energies 2023, 16, 3687 11 of 40

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Figure 7. Waveforms of measured values—Step Down mode starting the 10 V logic system.
Figure 7. Waveforms of measured values—Step Down mode starting the 10 V logic system.
The converter starts up in Step Up (Boost Mode) by default. Therefore, the myRIO
The converter
controller starts upand
was launched in Step Up (Boost
the operating Mode)
mode byconverter
of the default. was
Therefore,
changedthe myRIO
to Step
controller was launched and the operating mode of the converter was changed
Down at the control voltage of 0 V (Figure 8). Current consumption increased to about to Step
Down atA–0.12
0.06 the control
A at 48voltage of 0 V on
V. The voltage (Figure
the 12 8). Current
V side consumption
also increased, from 0increased
V to 4.63 V,tothen
about
decreased
0.06 A–0.12 and
A at 48stabilized at 4.53 V.
V. The voltage on the 12 V side also increased, from 0 V to 4.63 V, then
decreased and stabilized at 4.53 V.
Energies 2023, 16, x FOR PEER REVIEW 12 of 40

Energies 2023, 16, x FOR PEER REVIEW 12 of 40

Energies 2023, 16, 3687 12 of 40

Voltage Side VHigh=48V

Low Voltage Side VLow=12V
[V] contol voltage [V]

Voltage V High [V] Voltage V High [V]

Voltage V Low [V] Voltage V Low [V]

VHigh=48V
Low Voltage Side VLow=12V
DC/DC
DC/DC contol voltage

High Voltage Side High

Voltage Side VHigh=48V
Low Voltage Side VLow=12V
[A] Load Current [A]

[A]
Current ILow [A] Current ILow [A]

High
Current I
VHigh=48V
Low Voltage Side VLow=12V
Total Load CurrentTotal

High Voltage Side High

Current I [A] High
Figure 8. Waveforms of measured values—Step Down mode, myRIO launch.

The system was then started up again. The ultracapacitor of the low-voltage side was
charged
Figureto8. aWaveforms
nominalofvoltage ofvalues—Step
measured 12 V with Down
the DC/DC converter
mode, myRIO controlled for a current
launch.
Figure 8. Waveforms of measured values—Step Down mode, myRIO launch.
flow of about 0.4 A and then 1.4 A. After charging, a stable state was obtained with a power
supply of The system
12.09 was athen
V and started
current ofup again.
1.39 The ultracapacitor
A. The reading was of the low-voltage
taken side was
from the LOAD panel
The system
charged was then
to a nominal started
voltage upVagain.
of 12 The
with the ultracapacitor
DC/DC converterofcontrolled
the low-voltage side was
for a current
(Figure 9).
charged
flow oftoabout
a nominal voltage
0.4 A and ofA.
then 1.4 12After
V with the DC/DC
charging, a stable converter controlled
state was obtained withfor a current
a power
flowsupply
of aboutof 12.09
0.4 AVand
andthen
a current
1.4 A.ofAfter
1.39 charging,
A. The reading wasstate
a stable takenwas
from the LOAD
obtained panel
with a power
(Figure 9).
supply of 12.09 V and a current of 1.39 A. The reading was taken from the LOAD panel
(Figure 9).
DC/DC control voltage Voltage V Voltage V High
Low
Step Down: 12V charging
0.06 14 Step Down: 12V charging Step Down: 12V charging

12
0.04 47.6
10
DC/DC control voltage Voltage V Voltage V High
Low
Step Down: 12V charging
0.06 14
8 Step Down: 12V charging Step Down: 12V charging
0.02 47.55
12
6
0.04 47.6
0 10
4 47.5
0 100 200 300 0 100 200 300 0 100 200 300
Time [s] 8 Time [s] Time [s]
0.02 47.55
Total Load Current Current I Low Current I High
1.5 Step Down: 12V charging 6 Step Down: 12V charging
Step Down: 12V charging
0 0.5
0 4 47.5
0 100 200 300 0 100 200 300 0.4 0 100 200 300
1 − 0.5
Time [s] Time [s] Time [s]
0.3
Total Load Current Current I Low Current I High
1.5 Step Down: 12V charging −1 0.2
Step Down: 12V charging Step Down: 12V charging
0.5
0 0.1
0.5
− 1.5
0
0.4
1 − 0.5
0 −2 0.3
0 100 200 300 0 100 200 300 0 100 200 300
Time [s] −1 Time [s] 0.2 Time [s]
0.5
0.1
− 1.5
Figure 9. Waveforms of measured values, Step Down mode,
0 12 V charging.
Figure 9. Waveforms of measured values, Step Down mode, 12 V charging.
0 −2
0 100 200
In the300
next step,0the control
100 200
voltage 300the converter
of 0 100 changed
was 200 to300
0 V in order to
Time [s] Time [s] Time [s]
observe the behavior of the system. The voltage on the low-voltage sidetodropped,
In the next step, the control voltage of the converter was changed 0 V in order
the to
observe theconsumption
current behavior of recorded
the system. by the Theclamps
voltage on on
thethe
12 V low-voltage
side was about side0.01
dropped,
A, whilethe
on cur-
Figure 9. Waveforms of measured values, Step Down mode, 12 V charging.
rentthe
consumption recorded
48 V side it was 0.02 A. by
Thethe clamps
values wereon
readthefrom
12 Vtheside wassupply.
power about The 0.01measurement
A, while on the
48 Vwas
sidecompleted
it was 0.02manually
A. The at a low-voltage
values were read side andthe
from it rendered
power supply.the reading of 11.65 V
The measurement
In the10). manually at a low-voltage side and it rendered the reading of V
next step, the control voltage of the converter was changed to 0 in order to
was(Figure
completed 11.65 V (Fig-
observe the behavior of the system. The voltage on the low-voltage side dropped, the cur-
ure 10).
rent consumption recorded by the clamps on the 12 V side was about 0.01 A, while on the
48 V side it was 0.02 A. The values were read from the power supply. The measurement
was completed manually at a low-voltage side and it rendered the reading of 11.65 V (Fig-
ure 10).
Energies 2023, 16, x FOR PEER REVIEW 13 of 40

Energies 2023, 16, x FOR PEER REVIEW 13 of 40

Energies 2023, 16, 3687 13 of 40
0.06 12.2 47.62
DC/DC control voltage Voltage V Low Voltage V High
Step Down: 0V control Step Down: 0V control Step Down: 0V control
47.61
0.04 12
0.06 12.2 47.62
47.6
DC/DC control voltage Voltage V Low Voltage V High
Step Down: 0V control Step Down: 0V control Step Down: 0V control
47.61
47.59
0.02 11.8
0.04 12
47.6
47.58

0 11.6 47.59
47.57
0.020 200 400 600 11.80 200 400 600 0 200 400 600
Time [s] Time [s] 47.58 Time [s]

1.5 0 11.6
1 47.57
0.5
0 200 400Current 600
Total Load 0 200 Current400
I Low 600 0 200 Current400
I High 600
Time [s] 0V control
Step Down:
0.8 Time [s] 0V control
Step Down: 0.4 Time [s] 0V control
Step Down:

1
1.5 0.6 1 0.5
0.3
Total Load Current Current I Low Current I High
Step Down: 0V control 0.4
0.8 Step Down: 0V control 0.4
0.2 Step Down: 0V control
0.5
1
0.2
0.6 0.3
0.1

0 0
0.4 0.2
0.5 0
0 200 400 600 0 200 400 600 0 200 400 600
Time [s] 0.2 Time [s] Time [s]
0.1

0 0
0
0 200
Figure 400 600
10. Waveforms 0 200 values,
of measured 400 600 Down mode,
Step 0 200control.
0V 400 600
Time [s] Time [s] Time [s]

The10.parameters
Figure
Figure Waveforms of
10. Waveforms ofthe converter
measured
of measured were
values,
values,
Stepmeasured
Down mode,by
Step Down mode,
0 Vincreasing
0 V control. the control voltage of
control.
the DC/DC converter from 0.025 V, in steps of 0.025 V, in order to determine the control
The parameters of the converter were measured by increasing the control voltage of
characteristics
The
the DC/DC
of
parametersthe DC/DC
of the
converter from
converter
converter in theofStep
0.025 V, inwere
stepsmeasured
Down
0.025 V,by
mode 48 the
increasing
in order
V–12
to determine
V. The
control control
voltage
the control of
voltage was increased
the characteristics
DC/DC converter every 30
from 0.025
of the DC/DC s (each time
V, in in
converter steps the control
of 0.025
the Step voltage
DownV,mode
in order was
48–12to changed,
V. determine the
the steady
control
The control voltage
state wasincreased
was reached).
characteristics TheDC/DC
ofevery
the measurement
30 s (eachconverterwas
time the incompleted
control
thevoltage after reaching
was changed,
Step Down mode 48 the
the control
steady
V–12 voltage
V.state
The was of
control
0.5 V (Figure
reached). 11).
The measurement was completed after reaching the control
voltage was increased every 30 s (each time the control voltage was changed, the steady voltage of 0.5 V
(Figure
state 11).
was reached). The measurement was completed after reaching the control voltage of
0.5 V (Figure 11).
High Voltage Side VHigh=48V VHigh=48V
Low Voltage Side VLow=12V VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side

Low Voltage Side
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V VHigh=48V

Low Voltage Side VLow=12V VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

High Voltage Side

Low Voltage Side
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Figure 11. Waveforms of measured values, Step Down mode, control test.
Figure 11. Waveforms of measured values, Step Down mode, control test.
The system was disconnected in order to read the zero shift from the current clamps.
The
Figure 11.system
Then, the was disconnected
ultracapacitors
Waveforms of the 12
of measured in order
V side
values, toDown
were
Step read the zero
discharged
mode, shift
with from of
a current
control test. the
1Acurrent
(Figureclamps.
12).
Then, the ultracapacitors of the 12 V side were discharged with a current of 1 A (Figure
12). The system was disconnected in order to read the zero shift from the current clamps.
Then, the ultracapacitors of the 12 V side were discharged with a current of 1 A (Figure
12).
 Energies 2023, 16, x FOR PEER REVIEW 14 of 40

2023, 16, x FOR PEER REVIEW 14 of 40

Energies 2023, 16, 3687 14 of 40

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Figure 12. Waveforms of measured values, Step Down mode, disconnection of the system.

The initial
Figure voltageof of
12. Waveforms the ultracapacitors
measured before
values, Step Down mode,the
V. The measurements
disconnection was 0.21
of the system.
Figure 12. Waveforms of measured values, Step Down mode, disconnection of the system.
ultracapacitors were charged to 12 V. During their charging, a change in the converter
The initial voltage of the ultracapacitors before the measurements was 0.21 V. The
Thecurrent
initial value
voltage from
ultracapacitors
4 Aultracapacitors
of were
the to 2 A was observed
charged to 12 V.before
without
Duringthe
changing thewas
measurements
their
setting,
charging, a change 0.21
in the
after exceeding
V.converter
The
the voltage
ultracapacitors were
current ofcharged
value 4 V.
fromThe Avoltage
4to 122V.
to on the
During
A was high-voltage
their without
observed side
charging, wasthe
changed
a change
changing in thefrom
setting, 48 V to 36 V.
converter
after exceeding
The measurement
thefrom
current value voltage was
4 Aofto4 2V.AThemade
was voltagefrom the control
on thewithout
observed voltage
high-voltage of
side was
changing 0.025 V
thechanged with
setting, from a
after48 step
V to of
exceeding 36 0.025
V. TheV to
the control
the voltage of voltage
measurement
4 V. The was ofmade
voltage 0.5
onV,the
as high-voltage
fromshown in Figure
the control side13.
voltage ofThe
was step
0.025 time
V with
changed awas
from 4830
step s.to 36VV.
ofV0.025 to the
control was
The measurement voltage of 0.5
made V, asthe
from shown in Figure
control 13. of
voltage The step V
0.025 time wasa 30
with s. of 0.025 V to
step
the control voltage of 0.5 V,12.8
0.8
as shown in Figure 13. The step time was 30 s.
DC/DC control voltage Voltage V Low Voltage V High
Step Down: 36V control test Step Down: 36V control test 35.8 Step Down: 36V control test
12.6
0.6

0.8 12.8 12.4 35.7

DC/DC control voltage Voltage V Low Voltage V High
0.4
Step Down: 36V control test 35.8
Step Down: 36V control test Step Down: 36V control test
12.6 12.2 35.6
0.6
0.2 35.7
12.4 12
0.4 35.5
0 12.2 11.8 35.6
0 200 400 600 800 0 200 400 600 800 0 200 400 600 800
0.2 Time [s] Time [s] Time [s]
12
35.5
0 25 11.8 10 10
0 200 400 Total Load
600Current800 0 200 400 Current600
I Low
800 0 200 400 Current600
I
High 800
Step Down: 36V control test Step Down: 36V control test
20 Time [s] 8 Time [s]
Step Down: 36V control test
8 Time [s]
6
25 15 10 10 6
Total Load Current Current I Low Current I
Step Down: 36V control test 4 High
8 Step Down: 36V control test Step Down: 36V control test
20 10 8 4
2
6
15 5 6 2
0
4
10 0 -2 4 0
0 200 400 600 2
800 0 200 400 600 800 0 200 400 600 800
5 Time [s] Time [s] 2 Time [s]
0
0 Figure 13. -2Waveforms of measured values, Step
0 Down mode, 36 V control test.
0 200 400 Figure
600 80013. Waveforms
0 200 of measured
400 600 values,
800 Step0 Down
200 mode,
400 36600
V control
800 test.
Time [s] Time [s] Time [s]
Subsequently, the high-side voltage was changed from 36 V to 24 V. The measurement
Subsequently,
was carried the high-side
out from the control voltage was changed from 36 V to 24 V. The measure-
Figure 13. Waveforms of measured values, Stepvoltage of 0.025
Down mode, 36 V
V with a step
control test.of 0.025 V to the control
ment was carried
voltage out from
of 0.5 V (Figure 14).the
Stepcontrol
time 30voltage
s. of 0.025 V with a step of 0.025 V to the
control voltage
Subsequently, of 0.5 V (Figure
the high-side 14).
voltage Step
was time 30from
changed s. 36 V to 24 V. The measure-
ment was carried out from the control voltage of 0.025 V with a step of 0.025 V to the
control voltage of 0.5 V (Figure 14). Step time 30 s.
 Energies 2023, 16, x FOR PEER REVIEW 15 of 40

16, x FOR PEER REVIEW 15 of 40

Energies 2023, 16, 3687 15 of 40

0.8 12.8
DC/DC control voltage Voltage V Voltage V High

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Low
35.8

DC/DC contol voltage [V]

Step Down: 36V control test Step Down: 36V control test Step Down: 36V control test
12.6
0.6

Voltage V High [V]

Voltage V Low [V]
0.8 12.8
DC/DC control voltage Voltage V Voltage V High

High Voltage Side VHigh=48V

35.7

Low Voltage Side VLow=12V

Low
12.4 35.8
DC/DC contol voltage [V]

Step Down: 36V control test Step Down: 36V control test Step Down: 36V control test
0.4 12.6
0.6

Voltage V High [V]

Voltage V Low [V]
12.2 35.6
12.4 35.7
0.4 0.2
12
12.2 35.6 35.5

0.2 0 11.8
0 200 400 12 600 800 0 200 400 600 800 0 200 400 600 800
Time [s] Time 35.5
[s] Time [s]
0 11.8
0 200 400 25600 800 0 200 400 10600 800 0 200 400 10600 800
Time [s] Total Load Current Time [s] Current I Time [s] Current I High

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Low
Step Down: 36V control test Step Down: 36V control test
8 Step Down: 36V control test
Total Load Current [A]

20 8

Current IHigh [A]

25 10 10

Current ILow [A]

Total Load Current Current I 6 Current I High

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Low
Step Down: 36V control15
test Step Down: 36V control test
6
8 Step Down: 36V control test
Total Load Current [A]

20 4 8

Current IHigh [A]

10 Current ILow [A] 4
6
15 2 6
5 4 2
0
10 4
0 2
-2 0
5 0 200 400 600 800 0 200 400 2 600 800 0 200 400 600 800
0
Time [s] Time [s] Time [s]
0 -2 0
0 200 400 600 800 0 200 400 600 800 0 200 400 600 800
Time [s] Time [s] Time [s]
Figure 14. Waveforms of measured values, Step Down mode, 24 V control test.
Figure 14. Waveforms of measured values, Step Down mode, 24 V control test.
Figure 14. WaveformsThe
of measured values,
operation of theStep Downconverter
DC/DC mode, 24 V
incontrol test.
the Step Down mode for the high-side volt-
age for The operation
voltage of the
values DC/DC
lower than converter
24 V was in thechecked.
also Step Down Themode for the
behavior high-side
of the converter in
The operation of
voltagethe
forDC/DC
voltage converter
values lowerin the
than Step
24 V Down
was alsomode
checked.
the Step Down mode for voltages below 24 V on the high-voltage side was for the
The high-side
behavior volt-
of the converter
checked. The
age for voltage voltage values lower
in the Step Downthanmode
was regulated 24 Vforwas also checked.
voltages
manually
below 24 The
V onbehavior
on the power
the high-voltage
supply in of steps
the converter
of aboutin1 V. The setting
side was checked. The
the Step Downwas voltage
mode was regulated
for voltages manually
below on
24 V onthe power supply
the high-voltage in steps of about 1 V. The setting was
approx.
approx. 4.5 A.
4.5 A.inverter
The
The inverter
stopped
stopped
working
working
at 16 V.
atside
Returning
16 was checked. to
V.toReturning
24 V voltage
The 24 V voltage re-
restored the
voltage was regulated manually
stored the of operation on the power supply
of the converter in steps of about 1 V. The setting
15). (Figure 15).
was approx. 4.5 operation A. The inverterthe converter
stopped(Figure
working at 16 V. Returning to 24 V voltage re-
stored the operation of the converter Voltage
DC/DC control voltage
(Figure
V
15). Voltage V
Low High
0.15 Step Down: test for voltage values below 24V 12.25 Step Down: test for voltage values below 24V 25 Step Down: test for voltage values below 24V
High Voltage Side VHigh=48V
Low Voltage Side VLow=12V
DC/DC contol voltage [V]

DC/DC control voltage Voltage V Low Voltage V High

12.2
Voltage V High [V]
Voltage V Low [V]

0.15 Step Down: test for voltage values below 24V 12.25 Step Down: test for voltage values below 24V 25 Step Down: test for voltage values below 24V
0.1 20
High Voltage Side VHigh=48V
Low Voltage Side VLow=12V
DC/DC contol voltage [V]

12.2 12.15
Voltage V High [V]
Voltage V Low [V]

0.1 20
0.05 15
12.15 12.1

0.05 15
0 12.1 12.05 10
0 50 100 150 0 50 100 150 0 50 100 150
Time [s] Time [s] Time [s]
0 Total Load Current
12.05 10
Current I Current I
0 50 1006 150 0 50
Step Down: test for voltage values below 24V
100 150 Low 0 50 1005 150 High

Time [s] Time [s] Step Down: test for voltage values below 24V
Time [s] Step Down: test for voltage values below 24V
High Voltage Side VHigh=48V
Low Voltage Side VLow=12V

1
Total Load Current [A]

Total Load Current Current I Current I 4

Low High
Current IHigh [A]

6 5
Current ILow [A]

Step Down: test for voltage values below 24V

4 Step Down: test for voltage values below 24V Step Down: test for voltage values below 24V
High Voltage Side VHigh=48V

3
Low Voltage Side VLow=12V

1
Total Load Current [A]

0.5 4
Current IHigh [A]
Current ILow [A]

4 2
2 3
0.5 1
0 2
2 0
0
0 50 100 150 0 50 1
100 150 0 50 100 150
0
Time [s] Time [s] Time [s]
0 0
0 50 100 150 0 50 100 150 0 50 100 150
Time [s] Figure 15. Waveforms of measured values, Step Down mode, test for voltage values below 24 V.
Time [s] Time [s]
Figure 15. Waveforms of measured values, Step Down mode, test for voltage values below 24 V.
The test was also repeated with the low side target voltage changed from 12 V to 10 V
Figure 15. WaveformsThe
of measured
testThe
was values, Step Down
also repeated mode,
the test for voltage values below 24 V.
(Figure 16). converter stoppedwith
working low side target
at a voltage voltage
of about 14 V.changed from 12 V to 10
V (Figure 16). The converter stopped working at a voltage of about 14 V.
The test was also repeated with the low side target voltage changed from 12 V to 10
V (Figure 16). The converter stopped working at a voltage of about 14 V.
Energies 2023, 16, x FOR PEER REVIEW 16 of 40
Energies 2023, 16, x FOR PEER REVIEW 16 of 40
Energies 2023, 16, 3687 16 of 40

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

[V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V Low [V]Low

Voltage V High [V]

Voltage V

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

[A]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current ILow [A]Low

Current IHigh [A]

Current I

Figure 16. Measured value waveforms, Step Down mode, test for voltage values below 24 V (test
with Figure
low Measured
16.target
side value waveforms,
voltage Step Down mode,
V). test for voltage values below 24 V (test
Figure 16. Measured value changed from
waveforms, 12 V
Step to 10 mode,
Down test for voltage values below 24 V (test
with low side target voltage changed from 12 V to 10 V).
with low side target voltage changed from 12 V to 10 V).
We repeated the test with the low-side voltage changed from 10 V to 14 V. The oper-
We repeated the test with the low-side voltage changed from 10 V to 14 V. The operation
ationofof
We the converter
therepeated
converterthe
was was
test disturbed
with
disturbed the at a voltage
at low-side
a voltage aboutof19
voltage
of about
V. The19
changed V. The
from converter
10 V
converter to 14 V.
stopped stopped
The
workingoper-
working of completely
ationcompletely at awas
the converter voltage
at a voltage of18about
ofdisturbed
about V at a18voltage
(FigureV17).
(Figure 17). 19 V. The converter stopped
of about
working completely at a voltage of about 18 V (Figure 17).
High Voltage Side VHigh=48V
Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

[V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V Low [V]Low

Voltage V High [V]

Voltage V

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

[A]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current ILow [A]Low

Current IHigh [A]

Current I

Figure 17. Measured value waveforms, Step Down mode, test for voltage values below 24 V (test for
Figure 17. Measured value waveforms, Step Down mode, test for voltage values below 24 V (test for
low side voltage changed from 10 V to 14 V).
low side17.
Figure voltage changed
Measured from
value 10 V to 14
waveforms, V).Down mode, test for voltage values below 24 V (test for
Step
The next
low side voltage step presents
changed from 10theVdetermined
to 14 V). characteristics of the current, power, and losses
The next stepthe
for controlling presents
DC/DCthe determined
converter characteristics
in the Step of themode
Down operating current,
with power,
a voltageand
lossesreduction
for controlling
The nextfrom the
V toDC/DC
step48presents12 V.the converter
Figure 18 shows
determined in the
the Step
valueDown operating
of the current
characteristics mode
of theflowing with
through
current, athe
power, volt-
and
age low-voltage
reduction side.
from 48 V to 12 V. Figure 18 shows the value of the current
losses for controlling the DC/DC converter in the Step Down operating mode with a volt-flowing through
the
agelow-voltage side.48 V to 12 V. Figure 18 shows the value of the current flowing through
reduction from
the low-voltage side.
Energies 2023, 16, x FOR PEER REVIEW 17 of 40

Energies 2023, 16, 3687 17 of 40

Figure 18. Plot of the load current as a function of the control voltage of the DC/DC converter.

Figure 19 shows the input power and output power for Step Down operation from
48
FigureV to 1218.V.Plot of the load current as a function of the control voltage of the DC/DC converter.
Figure
18. Plot of the load current as a function of the control voltage of the DC/DC converter.
Figure 19 shows the input power and output power for Step Down operation from
48Figure
V to 1219
V. shows the input power and output power for Step Down operation from
48 V to 12 V.

Figure 19. Plot of the value of the power measured on the high- and low-voltage sides as a function
Figure 19.DC/DC
of the Plot ofconverter’s
the value of the power
control measured on the high- and low-voltage sides as a function
voltage.
of the DC/DC converter’s control voltage.
Figure 20 shows the losses of the converter configured in Step Down mode from 48 V
toFigure
12 V. 20 shows the losses of the converter configured in Step Down mode from 48
Figure 19. Plot of the value of the power measured on the high- and low-voltage sides as a function
V to
of the12 V. converter’s control voltage.
DC/DC

Figure 20 shows the losses of the converter configured in Step Down mode from 48
V to 12 V.
Energies 2023, 16, x FOR PEER REVIEW 18 of 40

Energies 2023, 16, 3687 18 of 40

Figure 20. Power losses as a function of the control voltage of the DC/DC converter.

The next step presents the determined characteristics of current, power, and losses
for Figure
controlling the
20. Power DC/DC
losses converter
as a function of thein the Step
control voltageDown operating
of the DC/DC mode with a voltage
converter.
Figure 20. Power losses as a function of the control voltage of the DC/DC converter.
reduction from 36 V to 12 V. Figure 21 shows the value of the current flowing through the
The next step presents the determined characteristics of current, power, and losses
low-voltage side.
forThe
controlling
next stepthepresents
DC/DC the converter in the Step
determined Down operating
characteristics mode with
of current, power,a voltage
and losses
reduction from 36 V to 12 V. Figure 21 shows the value of the current flowing through the
for controlling the DC/DC converter in the Step Down operating mode with a voltage
low-voltage side.
reduction from 36 V to 12 V. Figure 21 shows the value of the current flowing through the
low-voltage side.

Figure 21. Plot of the load current as a function of the control voltage of the DC/DC converter (36 V
Figure 21. Plot of the load current as a function of the control voltage of the DC/DC converter (36 V
to 12 V).
to 12 V).
Figure 22 shows the characteristics of the input power and output power—Step Down
Figure from
operation 22 shows
36 V tothe characteristics of the input power and output power—Step
12 V.
Figure
Down 21. Plot of the
operation load36
from current as V.
V to 12 a function of the control voltage of the DC/DC converter (36 V
to 12 V).

Figure 22 shows the characteristics of the input power and output power—Step
Down operation from 36 V to 12 V.
Energies 2023, 16, x FOR PEER REVIEW 19 of 40

Energies 2023, 16, 3687 19 of 40

Figure 22. Plot of the value of power measured on the high and low-voltage side as a function of the
DC/DC converter control voltage (36 V to 12 V).

Figure 22. Plot

Figure 23 of the value
shows theoflosses
power of
measured on the high
the converter in and
thelow-voltage
Step Down side as a function
mode at the of the
control
Figure 22. Plot
DC/DC of the value of power measured on the high and low-voltage side as a function of the
from 36 Vconverter
to 12 V.control voltage (36 V to 12 V).
DC/DC converter control voltage (36 V to 12 V).
Figure 23 shows the losses of the converter in the Step Down mode at the control from
36Figure
V to 12 23
V. shows the losses of the converter in the Step Down mode at the control
from 36 V to 12 V.

Figure 23. Plot of power losses as a function of the control voltage of the DC/DC converter (36 V to
Figure
12 V).23. Plot of power losses as a function of the control voltage of the DC/DC converter (36 V to
12 V).
The last step presents the determined characteristics of current, power, and losses
for The last stepthe
controlling presents
DC/DC the determined
converter characteristics
in the of current,
Step Down operating power,
mode withand losses for
a voltage
reduction from
controlling 24 V toconverter
the DC/DC 12 V. Figure
in 24
theshows the value
Step Down of the current
operating mode flowing throughreduc-
with a voltage the
Figure
tion from 24 V to 12 V. Figure 24 shows the value of the current flowing through the (36
23. Plot
low-voltage of power
side. losses as a function of the control voltage of the DC/DC converter low-V to
12voltage
V). side.

The last step presents the determined characteristics of current, power, and losses for
controlling the DC/DC converter in the Step Down operating mode with a voltage reduc-
tion from 24 V to 12 V. Figure 24 shows the value of the current flowing through the low-
voltage side.
Energies 2023, 16, x FOR PEER REVIEW 20 of 40

Energies 2023, 16, 3687 20 of 40

Figure 24. Plot of the load current as a function of the control voltage of the DC/DC converter (24 V
to 12 V).

Figure
Figure 25 shows
24. Plot thecurrent
of the load input as
power andofoutput
a function power
the control in of
voltage Step
the Down
DC/DCoperation
converter (24from
V 24
Figure 24. Plot of the load current as a function of the control voltage of the DC/DC converter (24 V
V to
to 12 V.
12 V).
to 12 V).
Figure 25 shows the input power and output power in Step Down operation from 24
V toFigure
12 V. 25 shows the input power and output power in Step Down operation from 24
V to 12 V.

Energies 2023, 16, x FOR PEER REVIEW 21 of 40

Figure 25. Plot of the value of power measured on the high- and low-voltage side as a function of the
Figure 25. Plot
DC/DC of thecontrol
converter valuevoltage
of power measured
(24 V to 12 V). on the high- and low-voltage side as a function of
the DC/DC converter control voltage (24 V to 12 V).
Figure 26 shows the losses of the Step Down converter from 24 V to 12 V.
Figure 25. Plot of the value of power measured on the high- and low-voltage side as a function of
Figure 26 shows the losses of the Step Down converter from 24 V to 12 V.
the DC/DC converter control voltage (24 V to 12 V).

Figure 26 shows the losses of the Step Down converter from 24 V to 12 V.

Figure 26. Power losses as a function of the control voltage of the DC/DC converter (24 V to 12 V).
Figure 26. Power losses as a function of the control voltage of the DC/DC converter (24 V to 12 V).

Knowledge of the efficiency and operating losses of the converter under various con-
ditions (Figures 18–26) is important when designing the target control algorithm. Param-
 Energies 2023, 16, 3687 21 of 40
Figure 26. Power losses as a function of the control voltage of the DC/DC converter (24 V to 12 V).

Knowledge of the efficiency and operating losses of the converter under various con-
Knowledge of the efficiency and operating losses of the converter under various condi-
ditions (Figures 18–26) is important when designing the target control algorithm. Param-
tions (Figures 18–26) is important when designing the target control algorithm. Parameter
eter values were selected in such a way that the value of R2 was as large as possible.
values were selected in such a way that the value of R2 was as large as possible.
Based on
Based on characteristics
characteristics presented
presented inin Figures
Figures 18,
18, 21
21,and
and24,
24,the
thefinal
finalvalues
values used
used inin
linear equation
linear equation for
for calculating
calculating the
the control
control voltage
voltage output
output in
in controller
controller software
software inin Step
Step
Down mode
Down mode was was

Output VStep Down = (Desired I + 0.844)/40.288,

Output VStep Down = (Desired I + 0.844)/40.288,

2.2.2.
2.2.2. Step
Step Up
Up Measurements
Measurements (Boost(BoostMode)
Mode)
In
In the
the further configuration, the
further configuration, the system
systemwas wasset
setfor
fortests
testsininthe
the Step
Step Up
Up mode
mode from
from 12
12
VV to to
4848VV (Figure
(Figure 27).
27). After
After starting
starting thethe converter
converter ininthetheStep
StepUp Upmode
modeandandcontrolling
controlling0
0V,V,the
thepower
powerconsumption
consumptionfrom fromthe
the 12
12 VV side
side would
would be be about
about 0.01
0.01 AA (below
(below the
the power
power
supply
supply indication). Load was set to constant voltage (CV) mode with target setpoint of of
indication). Load was set to constant voltage (CV) mode with target setpoint 48
48
V. V. Three
Three Maxwell16.2
Maxwell 16.2VVcapacitors
capacitorsare areconnected
connectedin in series
series on
on the
the high-voltage
high-voltage side.
side. A
A
slight
slightcharge
chargeofof the
the capacitors
capacitors was
was noted,
noted, from
from 0.21
0.21 to
to 0.32
0.32 VV at
at the
the 00 V
V setting
setting (Figure
(Figure 28).
28).

Energies 2023, 16, x FOR PEER REVIEW 22 of 40

Figure27.
Figure 27. Scheme
Scheme of
of the
the DC/DC
DC/DC converter
converter test
test stand
stand and
and measurements in Step
measurements in Step Up
Up mode.
mode.

10-3 DC/DC control voltage Voltage V Low Voltage V High

10 Step Up: zero measurement
0.34
15 Step Up: zero measurement Step Up: zero measurement
0.32
8
0.3
10
6 0.28

5 0.26
4
0.24

2 0 0.22
0 100 200 300 400 0 100 200 300 400 0 100 200 300 400
Time [s] Time [s] Time [s]

0 Total Load Current 0.5 Current I Low 12 Current I High

Step Up: zero measurement Step Up: zero measurement Step Up: zero measurement
− 0.01 0 10

8
− 0.02 − 0.5
6
− 0.03 −1
4
− 0.04 − 1.5 2

− 0.05 −2 0
0 100 200 300 400 0 100 200 300 400 0 100 200 300 400
Time [s] Time [s] Time [s]

Figure 28. Waveforms of measured values—zero measurement.

Figure 28. Waveforms of measured values—zero measurement.
The system was disconnected and the current clamps were reset again. We performed
10The system
V logic was disconnected
inclusion followed by 12and the current
V power (Figureclamps
29). were reset again. We performed
10 V logic inclusion followed by 12 V power (Figure 29).
VHigh=48V
VLow=12V
ltage [V]

[V]
[V]

h
 Time [s] Time [s] Time [s]

Figure 28. Waveforms of measured values—zero measurement.

Energies 2023, 16, 3687

The system was disconnected and the current clamps were reset again. We performed
22 of 40
10 V logic inclusion followed by 12 V power (Figure 29).

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Figure 29. Waveforms of measured values and second zero measurement.

Figure 29. Waveforms of measured values and second zero measurement.

Energies 2023, 16, x FOR PEER REVIEW

Then the high-voltage side was charged to 48 V with a current setting between 4 23 A of 40
Then
and 5 A.the high-voltage
There side from
was no response was the
charged
systemto 48 V 30).
(Figure withThe
a current setting
measurement of between
voltages 4 A
andfrom
5 A.the
There was no
internal response
circuit of the from the system
converter showed(Figure 30).
0 on the Theand
high- measurement
low-voltageof voltages
sides.
Logic
from thewas reset 2circuit
internal times. of the converter showed 0 on the high- and low-voltage sides.
Logic was reset 2 times.

Figure 30. Waveforms of measured values and Step Up mode (logic reset).
Figure 30. Waveforms of measured values and Step Up mode (logic reset).
Next, the ultracapacitors of the high-voltage side were manually charged to 12 V
andNext, the ultracapacitors
the system was connected. of An
the attempt
high-voltage side to
was made were manually
charge the 48 Vcharged to 12
side using theV and
theconverter.
system wasAfterconnected.
switching onAn(without
attemptsetting—Figure
was made to 31), the current
charge the 48 consumption
V side usingfrom the con-
the 12 V power supply is approx. 0.08 A. Initial current consumption from the
verter. After switching on (without setting—Figure 31), the current consumption from the 12 V line was
12 6.5 A. The supply
V power converterissetting
approx.was 0.125
0.08 A.V.Initial
After current
charging,consumption
the setting wasfrom
removed.
the 12Current
V line was
consumption from the 12 V line without setting was approx. 0.34 A. The voltage of the 48 V
6.5 A. The converter setting was 0.125 V. After charging, the setting was removed. Current
line dropped. The system was disconnected and the current clamps on the high-voltage
consumption from the 12 V line without setting was approx. 0.34 A. The voltage of the 48
side were reset. A consumption of approx. 0.5 A from the high-voltage side was recorded,
V line dropped.
without settingThe
and system
with thewas
12 Vdisconnected
power supply and the current
switched off. Withclamps onpower
the 12 V the high-voltage
supply
side were reset. A consumption of approx. 0.5 A from the high-voltage side was recorded,
without setting and with the 12 V power supply switched off. With the 12 V power supply
restored, consumption from the 12 V line was approx. 0.35, and consumption from the 48
V line was approx. 0.44 A.
 12 V power supply is approx. 0.08 A. Initial current consumption from the 12 V line was
6.5 A. The converter setting was 0.125 V. After charging, the setting was removed. Current
consumption from the 12 V line without setting was approx. 0.34 A. The voltage of the 48
V line dropped. The system was disconnected and the current clamps on the high-voltage
Energies 2023, 16, 3687 23 of 40
side were reset. A consumption of approx. 0.5 A from the high-voltage side was recorded,
without setting and with the 12 V power supply switched off. With the 12 V power supply
restored, consumption from the 12 V line was approx. 0.35, and consumption from the 48
restored, consumption from the 12 V line was approx. 0.35, and consumption from the 48 V
V line was approx. 0.44 A.
line was approx. 0.44 A.

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Energies 2023, 16, x FOR PEER REVIEW 24 of 40

Figure 31. Waveforms of measured values, Step Up mode, 48 V charge.
Figure 31. Waveforms of measured values, Step Up mode, 48 V charge.
In the next step, the operating characteristics of the converter in the Step Up mode
range of the
In
were thenext
testedpower
from supply
step,
the 12voltage
V, max
the operating
control 20 A);V see
withFigure
characteristics
of 0.025 a of of32.
the
step TheV step
converter
0.025 intime
to 0.475the was 30
Step Upsmode
V (maximum and
started
were with
tested
range a
of thecharged
frompower system
the control and
supply voltagea stabilized
12 V, maxof 20
0.025
A); V system.
seewith a step
Figure 32. of 0.025
The stepVtime
to 0.475
was V 30(maximum
s and
started with a charged system and a stabilized system.
High Voltage Side VHigh=48V
Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Figure 32. Waveforms of measured values, Step Up mode, 48 V control test.

Figure 32. Waveforms of measured values, Step Up mode, 48 V control test.
Then the load voltage setting was changed from 48 V to 36 V (Figure 33). The operating
Then the loadofvoltage
characteristics settinginwas
the converter the changed from from
Step Up mode 48 V the
to 36 V (Figure
control 33).
voltage ofThe operat-
0.025 V
ing characteristics of the
with a step of 0.025 V toconverter in the Step
0.475 V (maximum Up
range of mode from
the power the control
supply 12 V, maxvoltage of 0.025
20 A) were
tested.
V with Theof
a step step timeVwas
0.025 30 s and
to 0.475 started withrange
V (maximum a charged system
of the powerandsupply
a stabilized
12 V,system.
max 20 A)
were tested. The step time was 30 s and started with a charged system and a stabilized
system.
High=48V
Low=12V
age [V]

[V]
[V]
 Then the load voltage setting was changed from 48 V to 36 V (Figure 33). The operat-
ing characteristics of the converter in the Step Up mode from the control voltage of 0.025
V with a step of 0.025 V to 0.475 V (maximum range of the power supply 12 V, max 20 A)
were tested. The step time was 30 s and started with a charged system and a stabilized
Energies 2023, 16, 3687 system. 24 of 40

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Figure 33. Waveforms of measured values, Step Up mode, 36 V control test.

Figure 33. Waveforms of measured values, Step Up mode, 36 V control test.
Subsequently, the load voltage setting was changed from 36 V to 24 V (Figure 34). The
Subsequently,
operating the loadofvoltage
characteristics settinginwas
the converter changed
the Step fromfrom
Up mode 36 Vthe
tocontrol
24 V (Figure
voltage 34).
Energies 2023, 16, x FOR PEER REVIEW
The of
operating characteristics
0.025 V with of the
a step of 0.025 V toconverter in the Step
0.475 V (maximum Up mode
range from the
of the power 1225V,volt-
control
supply of 40

age max 20 A)
of 0.025 Vwere
withtested.
a step The step time
of 0.025 V to was
0.47530Vs and started with
(maximum a charged
range systemsupply
of the power and a 12
stabilized system.
V, max 20 A) were tested. The step time was 30 s and started with a charged system and a
stabilized system.
High Voltage Side VHigh=48V
Low Voltage Side VLow=12V
DC/DC contol voltage [V]

Voltage V High [V]

Voltage V Low [V]

High Voltage Side VHigh=48V

Low Voltage Side VLow=12V
Total Load Current [A]

Current IHigh [A]

Current ILow [A]

Figure 34. Waveforms of measured values, Step Up mode, 24 V control test.

Figure 34. Waveforms of measured values, Step Up mode, 24 V control test.
The next step presents the determined characteristics of the current, power, and
The next
losses step presents
for controlling the determined
the DC/DC characteristics
converter in the of themode
Step Up operating current,
with apower,
voltage and
losses for controlling
reduction from 12 Vthe DC/DC
to 48 converter
V. Figure inthe
35 shows thevalue
Step of
Up operating
the mode through
current flowing with a voltage
the
low-voltage side.
reduction from 12 V to 48 V. Figure 35 shows the value of the current flowing through the
low-voltage side.
 The next step presents the determined characteristics of the current, power, and
losses for controlling the DC/DC converter in the Step Up operating mode with a voltage
reduction from 12 V to 48 V. Figure 35 shows the value of the current flowing through the
Energies 2023, 16, 3687 low-voltage side. 25 of 40

Energies 2023, 16, x FOR PEER REVIEWFigure35.

Figure Plot of
35. Plot of the
theload
loadcurrent
currentand thethe
and current drawn
current fromfrom
drawn the low-voltage side asside
the low-voltage a function of26 of 40
as a function of
the control voltage of the DC/DC converter.
the control voltage of the DC/DC converter.
Figure 36 shows the input power and output power for Step Up operation from 12 V
to 48Figure
V. 36 shows the input power and output power for Step Up operation from 12 V
to 48 V.

Figure 36. Plot of the value of power measured on the high- and low-voltage sides as a function of
Figure 36. Plot
the DC/DC of the value
converter’s of power
control voltage.measured on the high- and low-voltage sides as a function of
the DC/DC converter’s control voltage.
Figure 37 presents the losses of the converter configured in Step Up mode from 12 V
to 48Figure
V. 37 presents the losses of the converter configured in Step Up mode from 12 V
to 48 V.
 Figure 36. Plot of the value of power measured on the high- and low-voltage sides as a function of
the DC/DC converter’s control voltage.

Figure 37 presents the losses of the converter configured in Step Up mode from 12 V
Energies 2023, 16, 3687 to 48 V. 26 of 40

Figure 37.37.Plot
Figure Plotofofthe
thepower lossesas
power losses asaafunction
functionof of
thethe control
control voltage
voltage ofDC/DC
of the the DC/DC converter.
converter.

Energies 2023, 16, x FOR PEER REVIEW Thenpresented

Then presented are
arethe
thedetermined
determinedcharacteristics of theof
characteristics current, power, and
the current, losses
power, andfor
27 losses
of 40
controlling the DC/DC converter in the Step Up operating mode with a voltage reduction
for controlling the DC/DC converter in the Step Up operating mode with a voltage reduc-
from 12 V to 36 V. Figure 38 shows the value of the current flowing through the low-
tion from 12 V to 36 V. Figure 38 shows the value of the current flowing through the low-
voltage side.
voltage side.

Figure 38.38.
Figure Plot of of
Plot thetheload
loadcurrent
current and the current
and the currentdrawn
drawn from
from thethe low-voltage
low-voltage side side as a function
as a function of of
the the
control voltage
control voltageofofthe
theDC/DC
DC/DCconverter.
converter.

Figure
Figure 3939presents
presents the
the input
inputpower
powerand
andoutput power
output for Step
power Up operation
for Step from 12from
Up operation V 12
to 36 V.
V to 36 V.
 Figure 38. Plot of the load current and the current drawn from the low-voltage side as a function of
the control voltage of the DC/DC converter.

Figure 39 presents the input power and output power for Step Up operation from 12
Energies 2023, 16, 3687 V to 36 V. 27 of 40

Figure
Energies 2023, 16, x FOR PEER REVIEWFigure Plotofofthe
39.Plot
39. thepower
power measured
measuredononthe high-
the andand
high- low-voltage sidessides
low-voltage as a function of the DC/DC
as a function of the
28 DC/DC
of 40
converter’s control voltage.
converter’s control voltage.
Figure 40 shows the losses of the converter configured in Step Up mode from 12 V to
Figure 40 shows the losses of the converter configured in Step Up mode from 12 V to
36 V.
36 V.

Figure
Figure 40. Plot
40. Plot of power
of power lossesasasaafunction
losses function of
of the
the control
controlvoltage
voltageof of
thethe
DC/DC converter.
DC/DC converter.
The last step presents the determined characteristics of the current, power, and losses
The last step presents the determined characteristics of the current, power, and losses
for controlling the DC/DC converter in the Step Up operating mode with a voltage re-
for controlling
duction fromthe12 DC/DC converter
V to 24 V. Figure 41in the Step
shows Up operating
the value mode
of the current with athrough
flowing voltagethe
reduc-
tionlow-voltage
from 12 V side.
to 24 V. Figure 41 shows the value of the current flowing through the low-
voltage side.
 The last step presents the determined characteristics of the current, power, and losses
for controlling the DC/DC converter in the Step Up operating mode with a voltage reduc-
tion from 12 V to 24 V. Figure 41 shows the value of the current flowing through the low-
Energies 2023, 16, 3687 voltage side. 28 of 40

Figure
Energies 2023, 16, x FOR PEER REVIEW 41.41.
Figure Plot of of
Plot the load
the loadcurrent
current and the current
and the currentdrawn
drawn from
from thethe low-voltage
low-voltage side side as a function
as a function 29 of of
of 40
the the
control voltage
control voltageofofthe
theDC/DC
DC/DCconverter.
converter.

Figure
Figure 4242presents
presents the
the input
inputpower
powerand
andoutput power
output for Step
power Up operation
for Step from 12from
Up operation V 12
to 24 V.
V to 24 V.

Figure
Figure 42.42. Plot
Plot ofofthe
thevalue
valueofof the
the power
powermeasured
measuredonon
thethe
high- andand
high- low-voltage sidessides
low-voltage as a function
as a function
of the control voltage of the DC/DC converter.
of the control voltage of the DC/DC converter.

Figure 43 shows the losses of the converter configured in Step Up mode from 12 V to
Figure 43 shows the losses of the converter configured in Step Up mode from 12 V to
24 V.
24 V. Based on characteristics presented in Figures 35, 38 and 41, the final values used in
linear equation for calculating the control voltage output in controller software in Step Up
mode were:
Output VStep Up = (Desired I + 0.25)/41.817,
The calibrated DC/DC converter was used to carry out bench tests of the battery and
ultracapacitor, which is presented in Section 2.3.
 Figure 42. Plot of the value of the power measured on the high- and low-voltage sides as a function
of the control voltage of the DC/DC converter.

Figure 43 shows the losses of the converter configured in Step Up mode from 12 V to
24 V.
Energies 2023, 16, 3687 29 of 40

Figure 43. Plot of power losses as a function of the control voltage of the DC/DC converter.
Figure 43. Plot of power losses as a function of the control voltage of the DC/DC converter.
2.3. Test Bench
Based onstand
The test characteristics presented
enables control of theinpower
Figures 35, 38, andbetween
distribution 41, the final values used
the battery in
and the
linear equation the
ultracapacitor, for calculating theof
technical data control
whichvoltage output in
are presented in controller software
Table 2. The in Step Up
Texas Instrument
mode were:
LM5170EVM-BIDIR 12 V/48 V converter was used for the system, the calibration of which
is discussed in Section 2.2. For the purposes of the conducted research, four LiFePO4 type
cells [92] (nominal voltage Output
13.2 V,Vin
Step Up = (Desired I + 0.25)/41.817,
4s1p configuration) were connected in series to the
low-voltage side, while a package of
The calibrated DC/DC converter was used three ultracapacitors
to carry outBMOD0058 E016
bench tests B02battery
of the [93] with
anda
capacity of 58 F and a voltage of 16 V each
ultracapacitor, which is presented in Section 2.3. was connected to the high-voltage side (total
voltage of the ultracapacitor package at full charge was ~48 V). Figure 44 shows a picture of
a system
2.3. in which the battery and the ultracapacitor have been connected together in a semi-
Test Bench
active topology. The photo also shows the monitoring and control application prepared in
The test
LabVIEW. Thestand
test enables controlrecording
stand enables of the power distributionofbetween
the parameters the HESthe andbattery and the
programming
ultracapacitor,
the loading and theloading
technical dataofofthe
cycles which are presented
storage. in Table
The charging and2.load
Thecurrent
Texas Instrument
values are
controlled by connecting to the Ethernet network with the TTI LD400 programmable power
supply. The system enables the recording of the following values: voltage (battery and
ultracapacitor), current (battery, ultracapacitor and total current loading the system). In
addition, the temperatures at the terminals, the housing and the ambient temperature
are recorded using thermocouples of J type. The use of the NI LabVIEW programming
environment and the CompactDAQ measurement interface allows for a quick adjustment
and expansion of the number of station registration channels for specific measurement tasks.
Measurement data are saved in the form of TDMS files convertible to formats acceptable
by Excel or Matlab software.
The bidirectional converter (Figure 3) makes it possible to connect sources with dif-
ferent voltage values. The use of an external controller in the open loop to control the
operation of the converter enables greater flexibility in connecting sources. The operation
of the converter was controlled by means of a directional signal (work in Step Up or Step
Down mode) and an analog voltage signal setting the value of the current sent in a given
direction. The converter also has the option of digital PWM signal control.
The National Instruments myRIO programmable controller was used to control the
operation of the converter. The myRIO controller is equipped with FPGA and real-time
(RT) circuits, programmable in the LabVIEW environment.
The presented converter control system is based on proportional controller in the open
loop with additional conditions limiting the minimum set current (the converter is inactive
until the calculated set current exceeds 0.5 A). In addition, the system has a minimum and
maximum voltage limitation of the low-voltage side (LiFePO4 battery side), limiting the
set current in order to protect the battery against deep discharge and overcharging. The
value of the set current flowing through the converter is calculated in proportion to the
 gramming the loading and loading cycles of the storage. The charging and load current
values are controlled by connecting to the Ethernet network with the TTI LD400 program-
mable power supply. The system enables the recording of the following values: voltage
(battery and ultracapacitor), current (battery, ultracapacitor and total current loading the
system). In addition, the temperatures at the terminals, the housing and the ambient tem-
Energies 2023, 16, 3687 30 of 40
perature are recorded using thermocouples of J type. The use of the NI LabVIEW pro-
gramming environment and the CompactDAQ measurement interface allows for a quick
adjustment and expansion of the number of station registration channels for specific meas-
difference between
urement tasks. the measured
Measurement voltage
data on the
are saved in high-voltage side (ultracapacitor
the form of TDMS side)
files convertible toand
for-
the specified threshold voltage of the ultracapacitor.
mats acceptable by Excel or Matlab software.

Figure44.
Figure 44.Photo
Photoofofthe
the test
test stand
stand andand
thethe monitoring
monitoring and and control
control application
application developed
developed in Lab-
in LabVIEW.
VIEW.
The DC/DC converter control system is completely independent of the system and
The bidirectional
measurement converter
and control software(Figure
of the 3) makes
energy it possible
storage to connect sources with dif-
test stand.
ferent voltage
The values. The
programmable FPGAuse of an
the external in the open
myRIO controller enables loop to control the
the implementation of
operation
various of the converter
standard types of enables
control greater flexibility
(e.g., PID in connecting
controller) as well assources. The operation
other, more complex
control algorithms
of the converter wasusing, among
controlled byothers,
meansthe of aextended
directional Kalman
signalfilter.
(workThe control
in Step canStep
Up or be
performed
Down mode) using
andregistered
an analog voltages
voltageorsignal
by measuring
setting the thevalue
current flow
of the (after connecting
current the
sent in a given
additional current
direction. The sensorsalso
converter to myRIO).
has the option of digital PWM signal control.
The developed stand was used to carry out tests at different power distribution values,
as presented in Section 3.1.

3. Results
3.1. Experimental Research of Battery–Ultracapacitor System in a Semi-Active Topology with a
DC/DC Converter
This subsection presents bench tests for the battery–ultracapacitor system, in a semi-
active, cascade topology with a DC/DC converter configured in 12 V/32 V mode.
The innovation presented in the article is the appropriate selection of the nominal
voltage UC, appropriately higher than the voltage of the DC bus (see Figure 1d), so that the
converter works only in the high-efficiency CC mode with full power, bypassing the CV
mode in which the power is deficient, and efficiency decreases.
In order to limit the reduction of losses, the nominal input and output voltages from
the converter were selected so that the difference was not too large, as it usually translates
into a decrease in efficiency, which was shown in works [82–90].
The power distribution was determined on the basis of the current value set from the
electronic load (discharging current) and from the power supply (charging current). The
Energies 2023, 16, 3687 31 of 40

myRIO controller controlling the operation of the DC/DC converter monitored the current
flowing in and out of the cell.
The control between the input of the DC/DC converter and myRIO was carried out by
means of two signals (signal 1 digital TTL—0–5 V responsible for selecting the operating
state of the converter Step Up/Step Down, signal 2 analog voltage where the voltage was
Energies 2023, 16, x FOR PEER REVIEW 32 of 40
proportional to the current consumed/transmitted by the converters), which is presented
in the schematic diagram in Figure 45.

Figure
Figure45.
45.Scheme
Schemeofofpower
powerdistribution
distributioncontrol
controlimplemented
implementedusing
usingthe
themyRIO
myRIOplatform.
platform.

The tests were

Utilization of carried
UC should out with power
be aimed at distribution
reducing thefrom stress10%
on to 90%.
BES. TheFigure 46 the
further shows
SoC
selected graphs of voltage and current values for the power
of BES deviates from the efficient middle range (20–80% SoC), the more the usage of UC distribution: 20%
(BES)/80%(UC)—Figure
should be increased. Given 46a, the
50%(BES)/50% (UC)—Figure
characteristics of the DC/DC 46b,converter,
and 80%(BES)/20% (UC)—
the UC utilization
Figure
at low46c. As expected,
currents should bemore voltage
limited oscillations
due to decreasedare seen with
efficiency, increasing
which was also battery
noted load,
in the
work
9.3 [77].VFurthermore,
V–14.9 utilization of UC in specific
(e.g., for 80%BES/20%UC—Figure 46c). exploitation
From the point conditions
of viewshould also be
of durability
ofconsidered,
LiFePO4 cells,i.e., intentional chargingshould
the ultracapacitor the UCact to as
itsafull,
bufferif high electric load
at pulsating is expected
current next
loads [94].
In(for example,
this a vehicle
configuration, thecoming to a stop, then
20%BES/80%UC splitstarting).
is preferable. In Figure 46a, the pulse cur-
rent for Thethetests were
battery carried
does out with
not exceed power
5.5 A, distribution
and the from 10% are
voltage oscillations to 90%. Figure
low, from 46
12.4
Vshows
to 14 V.selected
Batterygraphs
life canofbevoltage
extendedand current
with values for thewhich
this configuration, powerhas distribution:
been shown20% in
(BES)/80%(UC)—Figure
the work [95]. The studies46a, were 50%(BES)/50%
carried out for(UC)—Figure
an approximately 46b, and 80%(BES)/20%
constant SoC value(UC)—
(SoC
=Figure
0.5). In46c. As expected,
addition, more voltage
the maximum voltageoscillations
values (for are seen cell
a single withnot
increasing
more than battery
3.6 V,load,
for
a9.3–14.9
packageVin(e.g., for 80%BES/20%UC—Figure
the 4s1p configuration not more than 46c).
15From
V) and the point
the of viewvoltage
minimum of durability
(for a
of LiFePO4
single cell notcells, the ultracapacitor
less than 2 V, for a packageshould act4s1p
in the as a configuration
buffer at pulsating current
not less than 8loads [94].
V) were
In
set. this configuration, the 20%BES/80%UC split is preferable. In Figure 46a, the pulse
current for the battery does not exceed 5.5 A, and the voltage oscillations are low, from
12.4 V to 14 V. Battery life can be extended with this configuration, which has been shown
DC/DCin- mode
the12V/36V
work [95]. The studies were carried out for an approximately constant SoC value
14 39
Voltage BES|DC DCpower distribution 20%
(SoC = 0.5). In addition, the maximum voltage values (for a single cell not more than 3.6 V,
Voltage UC|DC DCpower distribution 80%

for a package in the 4s1p 38 configuration not more than 15 V) and the minimum voltage (for
Voltage BES [V]

13.5
Voltage UC [V]

a single cell not less than 2 V, for a package in the 4s1p configuration not less than 8 V)
Current [A]

37
were set.
13
36

12.5
35
0 50 100 150 200 250 300 350
Time [s]
 V to 14 V. Battery life can be extended with this configuration, which has been shown in
the work [95]. The studies were carried out for an approximately constant SoC value (SoC
= 0.5). In addition, the maximum voltage values (for a single cell not more than 3.6 V, for
a package in the 4s1p configuration not more than 15 V) and the minimum voltage (for a
Energies 2023, 16, 3687
single cell not less than 2 V, for a package in the 4s1p configuration not less than 8 V)32were
of 40
set.

DC/DC - mode 12V/36V

14 39
Voltage BES|DC DCpower distribution 20%
Voltage UC|DC DCpower distribution 80%

38
Voltage BES [V]

13.5

Voltage UC [V]

Current [A]
37

13
36

Energies 2023, 16,

12.5x FOR PEER REVIEW 33 of 40
35
0 50 100 150 200 250 300 350
Time [s]

(a)
DC/DC - mode 12V/36V
15 38
Voltage BES|DC DCpower distribution 50%
Voltage UC|DC DCpower distribution 50%
37.5
14
37
Voltage BES [V]

Voltage UC [V]
36.5

Current [A]
13
36

35.5
12
35

11 34.5
0 50 100 150 200 250 300 350 400
Time [s]

(b)

DC/DC - mode 12V/36V

15 35
Voltage BES|DC DCpower distribution 80%
Voltage UC|DC DCpower distribution 20%
14 34.5
Voltage BES [V]

Voltage UC [V]

13 34
Current [A]

12 33.5

11 33

10 32.5

9 32
0 50 100 150 200 250
Time [s]

(c)
Figure 46.
Figure 46. Plots
Plotsofofvoltage
voltageand
andcurrent
currentvalues
valuesfor
forthe power
the distribution:
power (a) (a)
distribution: 20%BES/80%UC, (b)
20%BES/80%UC,
50%BES/50%UC, (c) 80%BES/20%UC, mode 12 V/36 V.
(b) 50%BES/50%UC, (c) 80%BES/20%UC, mode 12 V/36 V.

The system
The system configured
configured inin this
this way
way offers
offers large
large amounts of energy
amounts of energy in
in the
the voltage
voltage range
range
from 12 V (battery) to 36 V (supplied by an ultracapacitor).
from 12 V (battery) to 36 V (supplied by an ultracapacitor).

3.2. Results Regarding Current Values in Future Research

In the CC charging mode currently discussed in Sections 2.1–2.3 and 3.1, where an
ultracapacitor
ultracapacitor module
module is connected
connected directly
directly toto the DC bus in a semi-active connection with
the DC/DC converter and the battery (Figure
DC/DC converter and the battery (Figure 1d), 1d), the
the processes
processes related
related to the change of
battery temperature and changes in state of health that affect affect the internal resistance of the
battery are not taken into account. Accounting for these processes requires corrections to
the CC mode control. In order to reduce losses within the entire system and maintain a
sufficiently
sufficiently high
high efficiency
efficiency ofof the
the DC/DC converter, an
DC/DC converter, an appropriate
appropriate algorithm
algorithm should
should be
be
used that takes into account the above degradation processes. Conventional
used that takes into account the above degradation processes. Conventional models based models based
on
on equivalent schemes [30,31],
equivalent schemes [30,31], learning methods [35,36],
learning methods [35,36], and
and adaptive
adaptive methods [96] will
methods [96] will
be used to develop an appropriate algorithm.
be used to develop an appropriate algorithm.
The experimental data
The experimental data obtained
obtained inin this
this work
work will
will be used in
be used in the
the future
future in
in the
the process
process
of identifying the parameters of models based on equivalent resistance-capacitance
of identifying the parameters of models based on equivalent resistance-capacitance (RC) (RC)
schemes [97–99] which describe the dynamics of
schemes [97–99] which describe the dynamics of the cell. the cell.
Based on the change in parameters describing the change in battery dynamics [32]
(i.e., activation polarization, concentration polarization, change in internal resistance, the
change in temperature, and the total heat flux released [100]) as well as the change in
charge over time and the change in state of health (SoH), the status will be estimated [35].
With the use of resistive-capacitive (RC) and inductive elements, the parameters of the
ultracapacitor will be identified based on the equivalent diagram of the ultracapacitor. In
Energies 2023, 16, 3687 33 of 40

Based on the change in parameters describing the change in battery dynamics [32] (i.e.,
activation polarization, concentration polarization, change in internal resistance, the change
in temperature, and the total heat flux released [100]) as well as the change in charge over
time and the change in state of health (SoH), the status will be estimated [35]. With the use
of resistive-capacitive (RC) and inductive elements, the parameters of the ultracapacitor
will be identified based on the equivalent diagram of the ultracapacitor. In [41], the authors
demonstrated that RC models are useful for modeling ultracapacitors and HES based
on battery and ultracapacitors. In the process of identifying the parameters to find the
minimum of the objective function, which is the minimization of the mean square error
values (MSE), as presented in [101], constituting the difference between the experimental
data and the vector of unknown parameters from the equivalent scheme, the following
algorithms will be used: Levenberg–Marquardt [102,103], Kalman filter [96,102,103] and
algorithms using neural networks [101,104,105]. Among the adaptive methods, special at-
tention should be paid to the non-linear, extended Kalman filter (EKF), used as an observer
for state estimation [96]). As far as the neural networks are concerned, particular focus
should be directed to recursive neural networks (RNN), i.e., nonlinear autoregressive exoge-
nous/nonlinear autoregressive moving average with exogenous (NARX/NARMAX) [101],
long short-term memory (LSTM) [106], and convolutional neural networks (CNN) [35,36]
for SoH estimation).
On the basis of experimental data, in addition to the correction of the CC charging
mode for the DC/DC converter in an HES for the model described by the equations of
state, as presented in [96], operating parameters will also be estimated, such as open-circuit
voltage (OCV), internal resistance, as well as state of charge (SoC) and state of health
(SoH). The state vector will be estimated and updated online on a regular basis from a
multidimensional system of state equations, based on the knowledge of the current input
values, including the value of the total load current and outputs, charging current in CC
mode, terminal and housing temperature of the cell, voltage, and model of the tested
system (the model approach based on the equivalent scheme, the so-called RC, from the
group of conventional models will be used for this purpose). In the case of parametric
models, models based on recurrent neural networks (e.g., NARMAX/NARX, LSTM) will
be used. Prediction of degradation changes will come from the fusion of data from the
identified parameters of analytical and parametric models for different SoC charge levels,
using a non-linear, extended Kalman filter (EKF); similar data fusion for predictive control
was carried out in works [34–36,38,97,98]. The advantage of using the extended Kalman
filter is that the average error value of the measured values and those calculated on the
basis of the model should be zero. In future studies, the average error value will be used as
the input of the adaptive procedure, correcting the model parameters in order to minimize
this error. Thanks to this procedure, the up-to-date information on the current values of
model parameters will also be available (identification of model parameters, online), which
in the next steps will be used to determine the non-linear characteristics of the model
parameters identified in real time on the basis of the previously adopted equivalent scheme,
which was presented in [101,107]. The extended Kalman filter will be implemented in the
measurement and control circuits as an algorithm in the application for monitoring and
controlling the DC/DC converter, prepared in the LabVIEW environment, in a cascade,
semi-active topology (Figure 1d).
It is worth noting that research is currently being conducted around the world on
the fusion of data from various models for HES. The work [108] presents the use of
analytical models together with genetic algorithms for modeling and controlling the power
distribution in the battery–ultracapacitor system through a bidirectional DC/DC converter
in a semi-active connection in a dynamic cycle, e.g., Worldwide Harmonized Light Vehicle
Test Procedure (WLTP). Further, in [94] the use of fractional order derivatives for estimation
of parameters in an HES based on a battery and an ultracapacitor represented in the
equivalent circuit as constant-phase elements (CPE) based on the Nyquist spectroscopic
impedance characteristic was presented. A metaheuristic swarm algorithm—particle
Energies 2023, 16, 3687 34 of 40

swarm optimization (PSO)—was used to identify the parameters of the equations of state.
For the verification and analysis of the obtained results, e.g., mean squared error (MSE) and
root mean square error (RMSE) indices, similar to the assumptions in this project with the
difference that in this proposal, the decision was taken to normalize RMSE with respect to 1,
i.e., normalized root mean square error (NRMSE). Previous studies presented in [101] have
shown that this indicator is more representative for the purposes of conducting analyses.
The work [95] presents the operational tests of 124 LFP electrochemical cells, which were
aimed at determining the possibility of predicting the change of state of health (SoH) up
to 2300 cycles. Similar tests in the Votsch climatic chamber are planned to be performed,
with one difference, which is that a group of several LFP batteries and ultracapacitors are
to be used in future tests. Paper [109] presents the optimization of power distribution
control in a semi-active battery-ultracapacitor system with the hardware implementation
for the NI myRIO-1900 controller with PWM signal control of the converter. It should be
added that a similar approach to the construction of the control architecture and hardware
implementation was assumed in this article, with the difference that the control of the
bidirectional DC/DC converter in the CC mode will be based on the CAN/Ethernet
network. The National Instruments myRIO programmable controller, equipped with
FPGA and real-time (RT) circuits and programmable in the LabVIEW environment will
be used to control the operation of the converter. The programmable FPGA of the myRIO
controller will enable efficient implementation of the extended Kalman filter. The control
will take place using registered voltages and by measuring the current flow (after connecting
additional current sensors to the myRIO controller). The proposed structures of non-linear
models will be transformed into structural models of state variables, applicable in control
systems and algorithms (including predictive control, as presented in [96,107]) with a
DC/DC converter in combination with semi-active charging for correction of the CC mode,
which is considered in this article.

4. Conclusions
4.1. Conclusions from the Calibration of the DC/DC Converter
Conclusions on the efficiency of the DC/DC converter:
• In the Step Down operating mode, the control voltage of the converter translates
directly into the value of the current transferred to the low-voltage side. The value of
the voltage on the high-voltage side has no effect on the value of the current transferred
to the low-voltage side.
• In the Step Up operating mode, the control voltage of the converter also translates
directly into the current value on the low-voltage side (consumed current). The value
of the voltage on the high-voltage side does not affect the value of the current drawn
on the low-voltage side.
• Step Down losses decrease exponentially as the DC/DC converter set-up voltage
increases. The value of losses slightly increases with the increase of the voltage
difference between the sides of the converter.
• Inverter losses in Step Up mode are more than twice as high as in Step Down mode.
• Idle power consumption is less than 0.5 A.
Conclusions on the operation of the DC/DC converter:
• Step Down mode—it is possible to start the converter when the voltage on the low-
voltage side is zero; it is recommended that the voltage on the low-voltage side is not
lower than 4 V.
• In Step Down mode, the voltage difference between the low and high-voltage sides
must be at least 4 V.
• Step Up mode—it is not possible to start the system when the high side voltage is zero;
a voltage equal to at least the low side voltage is required to start the system.
 Energies 2023, 16, 3687 35 of 40

• The current consumption of the converter in the idle state, both from the low- and
high-voltage side, was observed to be as low as 0.5 A. In the case of energy storage
measurements in relaxation, it is recommended to completely disconnect the converter
from the circuit.

4.2. Conclusions from the Experimental Research of Battery–Ultracapacitor System in a

Semi-Active Topology with a DC/DC Converter

Energies 2023, 16, x FOR PEER REVIEW

The paper highlights the essential advantages of BES-UC system with DC/DC con-
36 of 40
verter, such as:
• Higher volumetric power density of the HES in comparison to the battery compo-
nent only.
 Possibility of smooth power distribution from 0% to 100% between the battery and
• Possibility of smooth power distribution from 0% to 100% between the battery and the
the ultracapacitor.
ultracapacitor.
 Successful limitation of unfavorable battery operating states for pulsed currents ex-
• Successful limitation of unfavorable battery operating states for pulsed currents ex-
ceeding 2.5 C and, as a result, extending the life of the cell, reducing the costs associ-
ceeding 2.5 C and, as a result, extending the life of the cell, reducing the costs associated
atedwith
withreplacing
replacing the
the entire
entire package,
package, e.g.,
e.g., inin electric
electric vehicles
vehicles [10,110,111].
[10,110,111].
 • Increasing
Increasingthe range of energy
the range use (possible
of energy supply
use (possible of energy
supply to the system
of energy when the
to the system when
battery is completely discharged, the only limitation is the range of input/output
the battery is completely discharged, the only limitation is the range of input/output volt-
agesvoltages
of the DC/DC converter).
of the DC/DC converter).
 • Reduction of ultracapacitor
Reduction of ultracapacitor self-discharge
self-discharge(the(the
raterate
of self-discharge is about
of self-discharge 80%80%
is about per per
yearyear
[50]). For batteries, self-discharge does not exceed 30% per year [31].
[50]). For batteries, self-discharge does not exceed 30% per year [31]. The self- The self-
discharge
discharge value forfor
value thethebattery
batteryand
andultracapacitor
ultracapacitor considered
considered in inthis
thispaper
paperis is pre-
presented
sented below, in Figure 47. Self-discharge measurements were
below, in Figure 47. Self-discharge measurements were performed twice a month performed twice a for
month for 18 consecutive
18 consecutive months. months.
Selfdischarge [-]

Figure 47. Self-discharge

Figure of the
47. Self-discharge of battery and and
the battery ultracapacitor module
ultracapacitor (value
module 1: fully
(value charged
1: fully to 16toV;16 V;
charged
ultracapacitor, 3.3 V LiFePO4 cell) from the authors’ study.
ultracapacitor, 3.3 V LiFePO4 cell) from the authors’ study.

Author Contributions: Conceptualization: A.C.; Data curation, A.C. and K.B.; Formal analysis, A.C.;
Investigation, A.C. and K.B; Conceptualization:
Author Contributions: Methodology, A.C.; Software,
A.C.; DataA.C. and K.B.;
curation, Supervision,
A.C. A.C.; Visual-
and K.B.; Formal analysis,
ization, A.C. and K.B.; Writing—original draft, A.C. and K.B.; Writing—review & editing, A.C., K.B.,A.C.;
A.C.; Investigation, A.C. and K.B.; Methodology, A.C.; Software, A.C. and K.B.; Supervision,
P.P.,Visualization,
and J.M. All authors
A.C. andhave
K.B.;read and agreed to draft,
Writing—original the published
A.C. andversion of the manuscript.
K.B.; Writing—review & editing, A.C.,
K.B., P.P.
Funding: and J.M.
Studies wereAll authors
funded byhave read and agreed
ENERGYTECH-1 to the
project published
granted versionUniversity
by Warsaw of the manuscript.
of Tech-
nology under the program Excellence Initiative: Research University (ID-UB),
Funding: Studies were funded by ENERGYTECH-1 project granted by Warsaw University of No.Tech-
504/04496/1155/45.010700.
nology under the program Excellence Initiative: Research University (ID-UB), No. 504/04496/1155/
Data45.010700.
Availability Statement: Data will be made available on request.
Data Availability
Conflicts authors Data
Statement:
of Interest: The willnobeconflict
declare made available on request.
of interest.
Conflicts of Interest: The authors declare no conflict of interest.
References
1. The European Green Deal COM(2019) 640 Final—European Commision. Available online: https://eur-lex.europa.eu/re-
source.html?uri=cellar:b828d165-1c22-11ea-8c1f-01aa75ed71a1.0002.02/DOC_1&format=PDF (accessed on 28 March 2023).
2. ChaoJi 3.0 Standard. Available online: https://www.vector.com/int/en/know-how/protocols/gbt-27930/#c204146 (accessed on 26
March 2023).
3. White Paper of ChaoJi EV Charging Technology. In State Grid Corporation of China China Electricity Council Jointly Released June
2020; China Electricity Council: Beijiing, China, 2020.
4. IEC 61851‐23:2014; Electric Vehicle Conductive Charging System—Part 23: DC Electric Vehicle Charging Station. International
Electrotechnical Commission: Geneva, Switzerland, 1906.
Energies 2023, 16, 3687 36 of 40

References
1. The European Green Deal COM(2019) 640 Final—European Commision. Available online: https://eur-lex.europa.eu/resource.
html?uri=cellar:b828d165-1c22-11ea-8c1f-01aa75ed71a1.0002.02/DOC_1&format=PDF (accessed on 28 March 2023).
2. ChaoJi 3.0 Standard. Available online: https://www.vector.com/int/en/know-how/protocols/gbt-27930/#c204146 (accessed on
26 March 2023).
3. White Paper of ChaoJi EV Charging Technology. In State Grid Corporation of China China Electricity Council Jointly Released June
2020; China Electricity Council: Beijiing, China, 2020.
4. IEC 61851-23:2014; Electric Vehicle Conductive Charging System—Part 23: DC Electric Vehicle Charging Station. International
Electrotechnical Commission: Geneva, Switzerland, 1906.
5. Transport GHG Emission in EU. Available online: https://www.consilium.europa.eu/en/infographics/fit-for-55-afir-alternative-
fuels-infrastructure-regulation/ (accessed on 25 March 2023).
6. Directive (EU) 2018/2001 of the European Parliament and of the Council of 11 December 2018 on the Promotion of the Use
of Energy from Renewable Sources. Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:
32018L2001&from=EN (accessed on 24 March 2023).
7. Revision of the Renewable Energy Directive: Fit for 55 Package. Available online: https://www.europarl.europa.eu/RegData/
etudes/BRIE/2021/698781/EPRS_BRI(2021)698781_EN.pdf (accessed on 24 March 2023).
8. Chmielewski, A.; Gumiński, R.; Maczak,
˛ J.; Radkowski, S.; Szulim, P. Aspects of balanced development of RES and distributed
micro-cogeneration use in Poland: Case study of mCHP with Stirling engine. Renew. Sustain. Energy Rev. 2016, 60, 930–952.
[CrossRef]
9. Regulation of the European Parliament and of the Council on the Deployment of Alternative Fuels Infrastructure, and Repealing
Directive 2014/94/EU of the European Parliament and of the Council. Available online: https://eur-lex.europa.eu/resource.
html?uri=cellar:dbb134db-e575-11eb-a1a5-01aa75ed71a1.0001.02/DOC_1&format=PDF (accessed on 24 March 2023).
10. Wasim, M.S.; Habib, S.; Amjad, M.; Bhatti, A.R.; Ahmed, E.M.; Qureshi, M.A. Battery-Ultracapacitor Hybrid Energy Storage
System to Increase Battery Life Under Pulse Loads. IEEE Access 2022, 10, 62173–62182. [CrossRef]
11. Jankowska, E.; Kopciuch, K.; Błażejczyk, M.; Majchrzycki, W.; Piórkowski, P.; Chmielewski, A.; Bogdziński, K. Hybrid energy
storage based on ultracapacitor and lead acid battery: Case study. In Automation 2018; Springer: Berlin/Heidelberg, Germany,
2018; Volume 743, pp. 339–349.
12. Piórkowski, P.; Chmielewski, A.; Bogdziński, K.; Możaryn, J.; Mydłowski, T. Research on Ultracapacitors in Hybrid systems: Case
Study. Energies 2018, 11, 2551. [CrossRef]
13. Chariot, Electric Buses. Available online: https://chariot-electricbus.com/cmproduct/battery-electric-buses/ (accessed on
24 March 2023).
14. Chariot, Ultracapacitor E-Bus. Available online: https://chariot-electricbus.com/cmproduct/12m-ultracapacitor-chariot-e-bus/
(accessed on 24 March 2023).
15. Lee, S.; Kim, J. Power capability analysis of lithium battery and supercapacitor by pulse duration. Electronics 2019, 8, 1395.
[CrossRef]
16. Podder, A.K.; Chakraborty, O.; Islam, S.; Kumar, N.M.; Alhelou, A.H.H. Control Strategies of Different Hybrid Energy Storage
Systems for Electric Vehicles Applications. IEEE Access 2021, 9, 51865–51895. [CrossRef]
17. Hu, S.; Liang, Z.; He, X. Ultracapacitor-battery hybrid energy storage system based on the asymmetric bidirectional Z-source
topology for EV. Trans. Power Electron. 2016, 11, 7489–7498. [CrossRef]
18. Wang, J.; Wang, B.; Zhang, L.; Wang, J.; Shchurov, N.I.; Malozyomov, B.V. Review of bidirectional DC–DC converter topologies
for hybrid energy storage system of new energy vehicles. Green Energy Intell. Transp. 2022, 1, 100010. [CrossRef]
19. Yuhimenko, V.; Lerman, C.; Kuperman, A. DC active power filter-based hybrid energy source for pulsed power loads. IEEE J.
Emerg. Sel. Top. Power Electron. 2015, 3, 1001–1010. [CrossRef]
20. Demircalı, A.P.; Sergeant, S.; Koroglu, K.S.; Oztürk, E.; Tumbek, M. Influence of the temperature on energy management in
battery–ultracapacitor electric vehicles. J. Clean. Prod. 2018, 176, 716–725. [CrossRef]
21. Hung, N.B.; Jaewon, S.; Lim, O. A study of the effects of input parameters on the dynamics and required power of an electric
bicycle. Appl. Energy 2017, 204, 1347–1362. [CrossRef]
22. Akar, F.; Tavlasoglu, Y.; Vural, B. An Energy Management Strategy for a Concept Battery/Ultracapacitor Electric Vehicle With
Improved Battery Life. IEEE Trans. Transp. Electrif. 2017, 3, 191–200. [CrossRef]
23. Kollmeyer, P.K.; Jahns, T.M. Aging and performance comparison of absorbed glass matte, enhanced flooded, PbC, NiZn, and
LiFePO4 12V start stop vehicle batteries. J. Power Sources 2019, 441, 227139. [CrossRef]
24. Esfandyaria, A.B.; Nortona, M.; Conlona, M.C.; Cormack, S.J. Performance of a campus photovoltaic electric vehicle charging
station in a temperate climate. Sol. Energy 2019, 177, 762–771. [CrossRef]
25. Hu, J.S.; Lu, F.; Zhu, C.; Cheng, C.Y.; Chen, S.L.; Ren, T.J.; Mi, C.C. Hybrid Energy Storage System of an Electric Scooter Based on
Wireless Power Transfer. IEEE Trans. Ind. Inform. 2018, 8, 4169–4178. [CrossRef]
26. Park, J.; Appiah, W.A.; Byun, S.; Jin, D.; Ryou, M.H.; Lee, Y.M. Semi-empirical long-term cycle life model coupled with an
electrolyte depletion function for large-format graphite/LiFePO4 lithium-ion batteries. J. Power Sources 2017, 365, 257–265.
[CrossRef]
Energies 2023, 16, 3687 37 of 40

27. Pattipati, B.; Balasingam, B.; Avvari, G.V.; Pattipati, K.R.; Bar-Shalom, Y. Open circuit voltage characterization of lithium–ion
batteries. J. Power Sources 2014, 269, 317–333. [CrossRef]
28. Chmielewski, A.; Bogdziński, K.; Gumiński, R.; Szulim, P.; Piórkowski, P.; Możaryn, J.; Maczak,
˛ J. Operational research of VRLA
battery. Advances in Intelligent Systems and Computing. In Automation 2018; Springer: Berlin/Heidelberg, Germany, 2018;
Volume 743, pp. 783–791.
29. Czerwiński, A. Akumulatory, Baterie, Ogniwa; Wyd. WKŁ: Warszawa, Poland, 2012.
30. Sarasketa-Zabala, E.; Gandiaga, I.; Martinez-Laserna, E.; Rodriguez-Martinez, L.M.; Villarreal, I. Cycle ageing analysis of a
LiFePO4 /graphite cell with dynamic model validations: Towards realistic lifetime predictions. J. Power Sources 2015, 275, 573–587.
[CrossRef]
31. Wang, J.; Gan, Y.; Yao, M.; Li, Y. Cycle-life model for graphite-LiFePO4 cells. J. Power Sources 2011, 196, 3942–3948. [CrossRef]
32. Liang, J.; Gan, Y.; Yao, M.; Li, Y. Numerical analysis of capacity fading for a LiFePO4 battery under different current rates and
ambient temperatures. Int. J. Heat Mass Transf. 2021, 165, 120615. [CrossRef]
33. Li, J.; Adewuyi, K.; Lotfi, N.; Landers, R.G.; Park, J. A single particle model with chemical/mechanical degradation physics for
lithium ion battery State of Health (SOH) estimation. Appl. Energy 2018, 212, 1178–1190. [CrossRef]
34. Xiong, R.; Li, L.; Tian, J. Towards a smarter battery management system: A critical review on battery state of health monitoring
methods. J. Power Sources 2018, 405, 18–29. [CrossRef]
35. Tian, J.; Xiong, R.; Shen, W.; Lu, J.; Sun, F. Flexible battery state of health and state of charge estimation using partial charging
data and deep learning. Energy Storage Mater. 2022, 51, 372–381. [CrossRef]
36. Lu, J.; Xiong, R.; Tian, J.; Wang, C.; Hsu, C.W.; Tsou, N.T.; Sun, F.; Li, J. Battery degradation prediction against uncertain future
conditions with recurrent neural network enabled deep learning. Energy Storage Mater. 2022, 50, 139–151. [CrossRef]
37. Tian, J.; Xiong, R.; Shen, W. State-of-Health Estimation Based on Differential Temperature for Lithium Ion Batteries. IEEE Trans.
Power Electron. 2020, 35, 10363–10373. [CrossRef]
38. Tian, J.; Xiong, R.; Lu, J.; Chen, C.; Shen, W. Battery state-of-charge estimation amid dynamic usage with physics-informed deep
learning. Energy Storage Mater. 2022, 50, 718–729. [CrossRef]
39. Yang, R.; Xiong, R.; Ma, S.; Lin, X. Characterization of external short circuit faults in electric vehicle Li-ion battery packs and
prediction using artificial neural networks. Appl. Energy 2020, 260, 114253. [CrossRef]
40. Wu, S.; Xiong, R.; Li, H.; Nian, V.; Ma, S. The state of the art on preheating lithium-ion batteries in cold weather. J. Energy Storage
2020, 27, 101059. [CrossRef]
41. Chmielewski, A.; Piórkowski, P.; Bogdzinski, K.; Szulim, P.; Guminski, R. Test bench and model research of hybrid energy storage.
J. Power Technol. 2017, 97, 406–415.
42. Shen, J.; Khaligh, A. A supervisory energy management control strategy in a battery/ultracapacitor hybrid energy storage system.
IEEE Trans. Transp. Electrif. 2015, 1, 223–231. [CrossRef]
43. Kuperman, A.; Aharon, I.; Malki, S.; Kara, A. Design of a semiactive battery-ultracapacitor hybrid energy source. IEEE Trans.
Power Electron. 2013, 28, 806–815. [CrossRef]
44. Lin, X.; Zamora, R. Controls of hybrid energy storage systems in microgrids: Critical review, case study and future trends, Journal
of Energy Storage. J. Energy Storage 2022, 47, 103884. [CrossRef]
45. Chen, C.; Xiong, R.; Yang, R.; Shen, W.; Sun, F. State-of-charge estimation of lithium-ion battery using an improved neural network
model and extended Kalman filter. J. Clean. Prod. 2019, 234, 1153–1164. [CrossRef]
46. Mamun, A.A.; Liu, Z.; Rizzi, D.M.; Onori, S. An Integrated Design and Control Optimization Framework for Hybrid Military
Vehicle Using Lithium-Ion Battery and Supercapacitor as Energy Storage Devices. IEEE Trans. Transp. Electrif. 2019, 5, 239–251.
[CrossRef]
47. Blasius, E.; Wang, Z. Effects of charging battery electric vehicles on local grid regarding standardized load profile in administration
sector. Appl. Energy 2018, 224, 330–339. [CrossRef]
48. Reddy, K.J.; Natarajan, S. Energy sources and multi-input DC-DC converters used in hybrid electric vehicle applications—A
review. Int. J. Hydrog. Energy 2018, 43, 17387–17408. [CrossRef]
49. The Act on Road Traffic in Poland. Available online: https://prawooruchudrogowym.pl/ (accessed on 12 February 2023).
(In Polish).
50. Kowal, J.; Avaroglu, E.; Chamekh, F.; Šenfelds, A.; Thien, T.; Wijaya, D.; Sauer, D.U. Detailed analysis of the self-discharge of
supercapacitors. J. Power Sources 2011, 196, 573–579. [CrossRef]
51. Hossain Lipu, M.S.; Hannan, M.A.; Hussain, A.; Hoque, M.M.; Pin, J.K.; Saad, M.H.M.; Ayob, A. A review of state of health and
remaining useful life estimation methods for lithium–ion battery in electric vehicles: Challenges and recommendations. J. Clean.
Prod. 2018, 205, 115–133. [CrossRef]
52. Miluski, T. BMW Group Poland Training Course for Teachers of Technical Schools. BMW Electric Drive Systems. Generation 5.0”,
16 September 2022, Warsaw, Poland. Available online: https://aos.bmwgroup.com/web/oss/start (accessed on 28 February
2023).
53. Chmielewski, A.; Szulim, P.; Gregorczyk, M.; Gumi’nski, R.; Mydłowski, T.; Maczak, J. Model of an electric vehicle powered by a
PV cell—A case study. In Proceedings of the 2017 22nd International Conference on Methods and Models in Automation and
Robotics (MMAR), Miedzyzdroje, Poland, 28–31 August 2017.
Energies 2023, 16, 3687 38 of 40

54. Chen, H.; Sui, Y.; Shang, W.; Sun, R.; Chen, Z.; Wang, C.; Han, C.; Zhang, Y.; Zhang, H. Towards renewable public transport:
Mining the performance of electric buses using solar-radiation as an auxiliary power source. Appl. Energy 2022, 325, 119863.
[CrossRef]
55. Argyrou, M.C.; Marouchos, C.C.; Kalogirou, S.A.; Christodoulides, P. A novel power management algorithm for a residential
grid-connected PV system with battery-supercapacitor storage for increased self-consumption and self-sufficiency. Energy Convers.
Manag. 2021, 246, 114671. [CrossRef]
56. Sumsurooah, S.; He, Y.; Torchio, M.; Kouramas, K.; Guida, B.; Cuomo, F.; Atkin, J.; Bozhko, S.; Renzetti, A.; Russo, A.; et al.
ENIGMA—A Centralised Supervisory Controller for Enhanced Onboard Electrical Energy Management with Model in the Loop
Demonstration. Energies 2021, 14, 5518. [CrossRef]
57. Cavallo, A.; Russo, A.; Canciello, G. Control of Supercapacitors for smooth EMA Operations in Aeronautical Applications. In
Proceedings of the 2019 American Control Conference (ACC), Philadelphia, PA, USA, 10–12 July 2019; pp. 4948–4954.
58. Russo, A.; Cavallo, A. Stability and Control for Buck–Boost Converter for Aeronautic Power Management. Energies 2023, 16, 988.
[CrossRef]
59. Cavallo, A.; Canciello, G.; Russo, A. Integrated supervised adaptive control for the more Electric Aircraft. Automatica
2020, 117, 108956. [CrossRef]
60. Cavallo, A.; Canciello, G.; Russo, A. Buck-Boost Converter Control for Constant Power Loads in Aeronautical Applications.
In Proceedings of the 2018 IEEE Conference on Decision and Control (CDC), Miami Beach, FL, USA, 17–19 December 2018;
pp. 6741–6747.
61. Zhao, C.; Yin, H.; Yang, Z.; Ma, C. Equivalent series resistance based energy loss analysis of a battery semiactive hybrid energy
storage system. Trans. Energy Convers. 2015, 30, 1081–1091. [CrossRef]
62. Cabrane, Z.; Kim, J.; Yoo, K.; Ouassaid, M. HESS-based photovoltaic/batteries/supercapacitors: Energy management strategy
and DC bus voltage stabilization. Sol. Energy 2021, 216, 551–563. [CrossRef]
63. Hredzak, B.; Agelidis, V.G.; Jang, M. A model predictive control system for a hybrid battery-ultracapacitor power source. Trans.
Power Electron. 2014, 29, 1469–1479. [CrossRef]
64. Lencwe, M.J.; Chowdhury, S.P.D.; Olwal, T.O. Hybrid energy storage system topology approaches for use in transport vehicles: A
review. Energy Sci. Eng. 2022, 10, 1449–1477. [CrossRef]
65. Sinha, S.; Bajpai, P. Power management of hybrid energy storage system in a standalone DC microgrid. J. Energy Storage
2020, 30, 101523. [CrossRef]
66. Kurm, S.; Agarwal, V. Interfacing Standalone Loads with Renewable Energy Source and Hybrid Energy Storage System Using a
Dual Active Bridge Based Multi-Port Converter. IEEE J. Emerg. Sel. Top. Power Electron. 2020, 10, 4738–4748. [CrossRef]
67. Song, Z.; Li, J.; Han, X.; Xu, L.; Lu, L.; Ouyang, M. Multi-objective optimization of a semi-active battery/supercapacitor energy
storage system for electric vehicles. Appl. Energy 2014, 135, 212–224. [CrossRef]
68. Kumar, K.; Bae, S. Dynamic power management based on model predictive control for hybrid-energy-storage-based grid-
connected microgrids. Electr. Power Energy Syst. 2022, 143, 108384. [CrossRef]
69. Linxiao, G.; Denecke, M.E.; Foley, S.B.; Dong, H.; Qi, Z.; Koenig, G.M., Jr. Electrochemical characterization of lithium cobalt
oxide within aqueous flow suspensions as an indicator of rate capability in lithiumion battery electrodes. Electrochim. Acta
2018, 281, 822–830.
70. Xiong, R.; Chen, H.; Wang, C.; Sun, F. Towards a smarter hybrid energy storage system based on battery and ultracapacitor—A
critical review on topology and energy management. J. Clean. Prod. 2018, 202, 1228–1240. [CrossRef]
71. Mohamed, M.M.; Zoghby, H.M.E.; Sharaf, S.M.; Mosa, M.A. Optimal virtual synchronous generator control of bat-
tery/supercapacitor hybrid energy storage system for frequency response enhancement of photovoltaic/diesel microgrid.
J. Energy Storage 2022, 51, 104317. [CrossRef]
72. Arjanaki, A.A.; Kolagar, A.D.; Pahlavani, M.R.A. A two-level power management strategy in a DC-coupled hybrid microgrid
powered by fuel cell and energy storage systems with model predictive controlled interface converter. J. Energy Storage
2022, 52, 104861. [CrossRef]
73. Capasso, C.; Lauria, D.; Veneri, O. Experimental evaluation of model-based control strategies of sodium-nickel chloride battery
plus supercapacitor hybrid storage systems for urban electric vehicles. Appl. Energy 2018, 228, 2478–2489. [CrossRef]
74. Guo, F.; Sharma, R. A modular multilevel converter with half-bridge submodules for hybrid energy storage systems integrating
battery and ultracapacitor. In Proceedings of the 2015 IEEE Applied Power Electronics Conference and Exposition (APEC),
Charlotte, NC, USA, 15–19 March 2015.
75. Jing, W.; Lai, C.H.; Wong, S.H.W.; Wong, M.L.D. Battery supercapacitor hybrid energy storage system in standalone dc microgrids:
A review. IET Renew. Power Gener. 2016, 11, 461–469. [CrossRef]
76. Beuse, T.; Fingerle, M.; Wagner, C.; Winter, M.; Börner, M. Comprehensive Insights into the Porosity of Lithium-Ion Battery
Electrodes: A Comparative Study on Positive Electrodes Based on LiNi0.6 Mn0.2 Co0.2 O2 (NMC622). Batteries 2021, 7, 70. [CrossRef]
77. Qi, N.; Yin, Y.; Dai, K.; Wu, C.; Wang, X.; You, Z. Comprehensive optimized hybrid energy storage system for long-life
solar-powered wireless sensor network nodes. Appl. Energy 2021, 290, 116780. [CrossRef]
78. Ke, M.Y.; Chiu, Y.H.; Wu, C.Y. Battery Modelling and SOC Estimation of a LiFePO4 Battery. In Proceedings of the 2016 International
Symposium on Computer, Consumer and Control, Xi’an, China, 4–6 July 2016; pp. 208–211.
Energies 2023, 16, 3687 39 of 40

79. Guo, F.; Ye, Y.; Sharma, R. A Modular multilevel converter based battery-ultracapacitor hybrid energy storage system for
photovoltaic applications. In Proceedings of the 2015 Clemson University Power Systems Conference (PSC), Clemson, SC, USA,
10–13 March 2015.
80. Wu, Y.-U.; Tai, C.-H. Novel Bidirectional Isolated DC/DC Converter with High Gain Ratio and Wide Input Voltage for Electric
Vehicle Storage Systems. Batteries 2022, 240, 240. [CrossRef]
81. Liao, H.; Chen, Y.-T.; Chen, J.-F. Development of a Bidirectional DC–DC Converter with Rapid Energy Bidirectional Transition
Technology. Energies 2022, 15, 4583. [CrossRef]
82. Yi, W.; Ma, H.; Peng, S.; Dali, Z.M.L.; Dampage, U.; Hajjiah, A. Analysis and implementation of multi-port bidirectional converter
for hybrid energy systems. Energy Rep. 2022, 8, 1538–1549. [CrossRef]
83. Tomar, P.S.; Srivastava, M.; Verma, A. An Improved Current-Fed Bidirectional DC–DC Converter for Reconfigurable Split Battery
in EVs. IEEE Trans. Ind. Appl. 2020, 56, 6957–6967. [CrossRef]
84. Liu, Y.-C.; K-DSyu, Y.-L.C.; Dung, N.A. High-Frequency and High-Efficiency Isolated Two-Stage Bidirectional DC–DC Converter
for Residential Energy Storage Systems. IEEE J. Emerg. Sel. Top. Power Electron. 2020, 8, 1994–2006. [CrossRef]
85. Shreelakshmi, M.P.; Das, M.; Agarwal, V. Design and Development of a Novel High Voltage Gain, High-Efficiency Bidirectional
DC–DC Converter for Storage Interface. IEEE Trans. Ind. Electron. 2019, 66, 4490–4501.
86. Wu, Y.-E.; Ke, Y.-T. A Novel Bidirectional Isolated DC-DC Converter with High Voltage Gain and Wide Input Voltage. IEEE Trans.
Power Electron. 2021, 36, 7973–7985. [CrossRef]
87. Packnezhad, M.; Farzanehfard, H. Soft-Switching High Step-Up/Down Converter Using Coupled Inductors with Minimum
Number of Components. IEEE Trans. Ind. Electron. 2021, 68, 7938–7945. [CrossRef]
88. Santra, S.B.; Liang, T.-J. High Gain and High-Efficiency Bidirectional DC–DC Converter With Current Sharing Characteristics
Using Coupled Inductor. IEEE Trans. Power Electron. 2021, 36, 12819–12833. [CrossRef]
89. Mohammadi, M.R.; Amoorezaei, A.; Khajehoddin, S.A.; Moez, K. A High Step-Up/Step-Down LVS-Parallel HVS-Series ZVS
Bidirectional Converter with Coupled Inductors. IEEE Trans. Power Electron. 2022, 37, 1945–1961.
90. Kardan, F.; Alizadeh, R.; Banaei, M.R. A New Three Input DC/DC Converter for Hybrid PV/FC/Battery Applications. IEEE J.
Emerg. Sel. Top. Power Electron. 2017, 5, 1771–1778. [CrossRef]
91. Texas Instruments LM5170EVM-BIDIR Manual. Available online: https://www.ti.com/tool/LM5170EVM-BIDIR (accessed on
28 January 2023).
92. LiFePO4 ANR26650M1-B Technical Data. Available online: https://www.bto.pl/pdf/04579/MD100113-01-ANR26650M1B.pdf
(accessed on 28 January 2023).
93. Maxwell BMOD0058 E016 B02 Technical Data. Available online: https://maxwell.com/wp-content/uploads/2021/08/3003212.
2_Datasheet_BMOD0058-E016-C02.pdf (accessed on 28 January 2023).
94. Wang, Y.; Gao, G.; Li, X.; Chen, Z. A Fractional–Order Model–Based State Estimation Approach for Lithium–Ion Battery and
Ultra–Capacitor Hybrid Power Source System Considering Load Trajectory. J. Power Sources 2020, 449, 227543. [CrossRef]
95. Kristen, A.S.; Attia, P.M.; Jin, N.; Perkins, N.; Jiang, B.; Yang, Z.; Chen, M.H.; Aykol, M.; Herring, P.K.; Fraggedakis, D.; et al.
Data–Driven Prediction of Battery Cycle Life Before Capacity Degradation. Nat. Energy 2019, 4, 383–391.
96. Tan, B.; Li, H.; Zhao, D.; Liang, Z.; Ma, R.; Huangfu, Y. Finite-control-set model predictive control of interleaved DC-DC boost
converter Based on Kalman observer. eTransportation 2022, 11, 100158. [CrossRef]
97. He, H.; Xiong, R.; Fan, J. Evaluation of Lithium–Ion Battery Equivalent Circuit Models for State of Charge Estimation by an
Experimental Approach. Energies 2011, 4, 582–598. [CrossRef]
98. Zhang, C.; Allafi, W.; Dinh, Q.; Ascencio, P.; Marco, J. Online Estimation of Battery Equivalent Circuit Model Parameters and
State of Charge Using Decoupled Least Squares Technique. Energy 2018, 142, 678–688. [CrossRef]
99. Guo, W.; Sun, Z.; Vilsen, S.B.; Meng, J.; Stroe, D.I. Review of “grey box” lifetime modeling for lithium-ion battery: Combining
physics and data-driven methods. J. Energy Storage 2022, 56, 105992. [CrossRef]
100. Lai, Y.; Du, S.; Ai, L.; Cheng, Y.; Ji, M. Insight into Heat Generation of Lithium–Ion Batteries Based on the Electrochemical–Thermal
Model at High Discharge Rates. Int. J. Hydrog. Energy 2015, 40, 13039–13049. [CrossRef]
101. Chmielewski, A.; Możaryn, J.; Piórkowski, P.; Bogdziński, K. Comparison of NARX and Dual Polarization Models for Estimation
of the VRLA Battery Charging/Discharging Dynamics in Pulse Cycle. Energies 2018, 11, 3160. [CrossRef]
102. Ramadan, H.S.; Becherif, M.; Claude, F. Extended kalman filter for accurate state of charge estimation of lithium-based batteries:
A comparative analysis. Int. J. Hydrog. Energy 2017, 42, 29033–29046. [CrossRef]
103. He, H.; Xiong, R.; Zhang, X.; Sun, F.; Fan, J.X. State-of-Charge Estimation of the Lithium-Ion, Battery Using an Adaptive Extended
Kalman Filter Based on an Improved Thevenin Model. IEEE Trans. Veh. Technol. 2011, 60, 1461–1469.
104. Chia, Y.Y.; Lee, L.H.; Shafiabady, N.; Isa, D. A load predictive energy management system for supercapacitor–battery hybrid
energy storage system in solar application using the Support Vector Machine. Appl. Energy 2015, 137, 588–602. [CrossRef]
105. Bordes, A.; Danilov, D.; Desprez, P.; Lecocq, A.; Marlair, G.; Truchot, B.; Dahmani, M.; Siret, C.; Laurent, S.; Herreyre, S.; et al.
A holistic contribution to fast innovation in electric vehicles: An overview of the DEMOBASE research project. eTransportation
2022, 11, 100144. [CrossRef]
106. Chmielewski, A.; Możaryn, J.; Piórkowski, P.; Dybała, J. Comparison of hybrid recurrent neural networks and dual polarization
models of valve regulated lead acid battery. Int. J. Energy Res. 2021, 45, 2560–2580. [CrossRef]
Energies 2023, 16, 3687 40 of 40

107. Sun, J.; Tang, C.; Li, X.; Wang, T.; Jiang, T.; Tang, Y.; Chen, S.; Qiu, S.; Zhu, C. A remaining charging electric quantity based pack
available capacity optimization method considering aging inconsistency. eTransportation 2022, 11, 100149. [CrossRef]
108. Chang, L.; Yujie, W.; Li, W.; Zonghai, C. Load–Adaptive Real–Time Energy Management Strategy for Battery/ Ultracapacitor
Hybrid Energy Storage System Using Dynamic Programming Optimization. J. Power Sources 2019, 438, 227024.
109. Lu, X.; Chen, Y.; Fu, M.; Wang, H. Multi–Objective Optimization–Based Real–Time Control Strategy for Battery/Ultracapacitor
Hybrid Energy Management Systems. IEEE Access 2019, 7, 11640–11650. [CrossRef]
110. Piao, N.; Gao, X.; Yang, H.; Guo, Z.; Hu, G.; Cheng, H.-M.; Li, F. Challenges and development of lithium-ion batteries for low
temperature environments. eTransportation 2022, 11, 100145. [CrossRef]
111. Li, X.; Yuan, C.; Wang, Z.; He, J.; Yu, S. Lithium battery state-of-health estimation and remaining useful lifetime prediction based
on non-parametric aging model and particle filter algorithm. eTransportation 2022, 11, 100156. [CrossRef]

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