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Electric Vehicle
Charging
Infrastructure

XXXXX

From Grid to Battery

E
lectrification has been a transportation sector, and it is ex-
SEBASTIAN RIVERA, key component of techno- panding at a rapid pace. In 2020, the
SAMIR KOURO, logical progress and eco- global electric vehicle (EV) fleet was
SERGIO VAZQUEZ, nomic development since expected to exceed 8.5 million, with
STEFAN M. GOETZ, the industrial revolution. almost 2 million new sales, reaching
RICARDO LIZANA, and It has improved living the same market value as in 2019. Cur-
ENRIQUE ROMERO-CADAVAL conditions, spurred innovation, and rently, China remains the world’s larg-
increased efficiency across all sec- est EV market, followed by Europe and
tors of our economy and all aspects of the United States. Norway is the global
our lives. During the coming decades, leader in terms of the EV market share
electrification is expected to reach among all vehicles [1], [2]. Despite
further and deeper into the transpor- this, EVs accounted for only 2.6% of
tation, building, and industry sectors, global new car sales during 2019, or
mainly motivated by the energy transi- 1% of the worldwide fleet [1]. Never-
tion to a zero-carbon-emission-based theless, there are clear signs that the
economy to mitigate climate change. pace of adoption will increase, with
Digital Object Identifier 10.1109/MIE.2020.3039039 Electric mobility is at the fore- projections indicating that 58% of ve-
Date of current version: 9 February 2021 front of the energy transition in the hicles will be EVs by 2040 [2].

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This substantial growth is the re- is still work to be done to increase a conventional outlet. These times can
sult of joint efforts of governments, charging speeds to fulfill consumer be reduced by installing faster home
the automotive industry, and other expectations, and substantial cost chargers but at an additional cost of
stakeholders, leading to an increasing reductions must be made to increase US$2,000–US$4,000 [6].
number of EVs on the streets during global deployment. Therefore, the On the other hand, the growing
the past 10 years [3]. The industry main motivation of this article is to interest in EV architectures in the
keeps evolving in ways that facilitate provide an in-depth overview of EV 450–920-V range require modifications
the migration to cleaner and envi- charging infrastructure, covering ev- in existing regulations. The promotion
ronmentally friendlier transportation ery type of charging mode and how of 800-V configurations would be ben-
[4], [5]. Every aspect of the EV eco- it relates to updated standards and eficial because it could theoretically
system has been improved: cheaper power levels. In addition, the state of double the charging power while keep-
and better battery packs, a growing the art in mainstream industrial solu- ing the same cable cross section, en-
public charging infrastructure, the tions for onboard slow ac chargers, tailing a substantial weight reduction
collaborative development of charg- fast ac integrated chargers, and fast within a vehicle [11]. However, the rel-
ing standards toward interoperabil- offboard dc charging power converter evant standards have not considered
ity, and a wider assortment of EVs, to topologies are presented. The article this voltage range, given that most
name a few [6]–[8]. To fulfill consumer aims to provide a comprehensive ref- EV technology was enabled by 600-V
expectations that charging times will erence for researchers and practicing semiconductors [11].
be equivalent to the time it takes to engineers for established and emerg-
fuel conventional vehicles, EV supply ing technology trends in this dynamic EV Architecture
equipment (EVSE) networks are ex- industry. Most modern plug-in vehicles share
panding, with increasing power levels. a similar electric powertrain, which
Charging times have been cut to as Latest Developments in the EV is composed of the following parts:
few as 20–30 min for roughly 400 km Industry the battery, which typically has a
of range, with further reductions ex- In the period from 2010 to 2020, battery relatively high voltage to keep the
pected. technology and manufacturing made currents moderate; a battery man-
While these improvements are par- great advances. Today’s batteries of- agement system (BMS); an onboard
tially attributed to advances in bat- fer higher power and energy densities charger (OBC); various dc–dc con-
tery technology, strides made with at a fraction of the 2010 price per kilo- verters to provide the appropriate
the dc fast charger are key to driving watt hour [6], falling from more than voltage levels for auxiliary units; drive
down the charging times. The two de- US$1,100 to US$156 [1], [2]. In addition, inverters; high-voltage loads, such as
velopments that contributed heavily the average EV battery is guaranteed heaters and chillers; and nonelectric
toward faster charging have focused for at least eight years or 160,000 km parts, including the cooling system,
on controlling the connector pin tem- [1]. As a result, most of the available which is typically water based, with
perature at high current levels (using mass market EVs have ranges of more different temperature loops—a low-
liquid-cooled cables and pins) and than 320 km, with an average capacity temperature loop that is at or below
reducing the current draw by increas- of 44 kWh [1], [4]. However, this capac- the ambient temperature for the bat-
ing the battery pack voltage (800-V ity growth has imposed substantial tery and one or two loops at higher
architectures) [9]–[12]. These break- challenges related to battery chargers temperature levels for the rest of the
throughs enabled an increase in the and charging rates, as today’s EVs do components [13], [14].
charging power from 50 kW to more not charge as fast as expected when In particular, dc chargers are de-
than 400 kW [10], and further improve- conventional 50-kW charging stations signed to communicate and operate
ments in the charger may support are used. with a vehicle and its architecture
even greater charging time reductions Consequently, improvements in [Figure 1(a)]. Both ac and dc charging
while limiting ohmic losses. battery technology prompted updates require only a share of the available
Despite the developments in charg- to charging standards since larger units; all others can be turned off. In
ing infrastructure technology, glob- battery capacities confuse the mar- modern vehicles, if no power-saving
ally, there were only 598,000 publicly keting jargon used to label existing dc means are used, the average load of
accessible slow chargers (with 50% of charging infrastructure. For instance, the 12-V auxiliaries can exceed 1 kW,
them in China and 38% concentrated a conventional 50-kW charger is able with peaks of several kilowatts. The
in 7 other countries) [1] and 264,000 to bring a 40-kWh Nissan Leaf to an cooling system often also claims sev-
publicly accessible fast chargers (with 80% state of charge (SoC) in roughly eral kilowatts and must be turned off
81% of them in China and 14% in 6 oth- 30 min, while a 62-kWh Chevrolet when it is not needed (including the
er countries) as of 2019 [1]. This is why Bolt will take approximately 1.6 times refrigerating compressor of the low-
accessible public charging infrastruc- longer. This also translates to home temperature chiller and passenger
ture remains one of the major barriers charging, as a 60-kWh pack would air conditioning). Note that with the
for EV adoption by customers. There take more than 32 h to recharge using increasing charging power, cooling

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1:2 dc-dc Auxiliary

BMS
Dedicated Converter dc–dc
Pump OBC (Optional) Converter
Low-Voltage Battery
Drive Unit
Inverter/
Machine
Pump
High-Voltage Bus
Low-Voltage Bus
Communications Bus (PLC or CAN)
Heater High-Temperature Thermal Loop
Radiator Low-Temperature Thermal Loop Integrated OBC
ac Bus (Single- or Three-Phase)
(Optional)
Chiller
High-Voltage Battery

(a)

Offboard
Charger

dc Fast Charging
ac Integrated Charger/
Onboard Motor Drive
dc Charger
ac dc ac
dc
Power Generation dc
dc dc dc

BMS
Battery Pack
Wind

Fast Charging
Station

Photovoltaic
on
ssi Three
smi Phase
ran
rT tio
n
we
Po ibu
Coal/Gas Single Distr Onboard Integrated Charger/

w er Charger Motor Drive

Phase Po ac Fast Charging ac
dc
dc
dc
ac
dc

BMS
Battery Pack

Onboard Integrated Charger/

charger Motor Drive
Home Charging
ac dc ac
ac Slow Charging dc dc dc

BMS
Battery Pack

(b)

FIGURE 1 – The power flow from the source to the wheel. (a) The EV powertrain. (b) The generation, transmission, distribution, and charging infra-
structure. CAN: controller area network; PLC: power line communication.

during and even before charging be- battery unit incorporates both a con- The BMS is normally the unit that
comes mandatory to limit battery ag- tactor and a fuse, which collaborative- communicates with chargers—inter-
ing. This energy, which can easily ex- ly protect the battery against overcur- nal and external—commands them,
ceed the output of an OBC, has to be rent and ensure that the battery can and manages voltage and current
branched from the charging power. interrupt fault currents of any level profiles. In most modern plug-in ve-
In several aspects, the battery is [15]. Chargers typically follow only the hicles, the BMS is responsible for any
the focus of chargers; it is highly sen- commands provided by the BMS, act interaction with the battery [16], and
sitive and, therefore, carefully protect- widely as electronically controlled dc it electrically monitors the battery’s
ed, and it usually takes priority over voltage and current sources, and de- cells with respect to the SoC, current
all charging processes and involved liver the requested current and volt- and charge inflows and outflows, ag-
units. Generally, every output of the age with minimal deviations. ing, and heat levels. Additionally, it

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continuously updates the limits for Alternatively, splitting the battery into the Combined Charging System (CCS),
maximum outflowing and inflowing subsections that have a sub-400-V promoted by the CharIn organization,
(recuperation and charging) currents voltage and charging them in a bal- tried to deal with these incompat-
based on the cells’ temperature, his- anced fashion, either interleaved or in ibilities. The CCS proposes a univer-
tory, and expected future condition, parallel, has been proposed [21]–[24]. sal solution that covers single- and
and it communicates this informa- three-phase ac [International Electro-
tion to the other units so that they Charging Standards Updates technical Commission (IEC) 61851-22
adjust their operation and potentially As shown in Figure 1(b), the charg- and Society of Automotive Engineers
throttle their power share. The BMS ing ecosystem is composed of three (SAE) J1772] as well as dc high-power
controls all contactors that allow ac- fundamental alternatives to conduc- charging in the United States (type 1)
cess to the battery. It can disconnect tively recharge a battery pack: single- (SAE J1772) and Europe (type 2) (IEC
any charger within milliseconds if it phase (and split-phase) slow charging 61851-23). In 2016, this system was de-
detects standards violations, discrep- during long vehicle idle times, which fined for chargers up to 200 kW and
ancies between the requested and de- includes charging at homes and work- voltages in the range of 200–1,000 V. Now,
tected current and voltage, and qual- places through an OBC; three-phase the CCS supports a maximum power
ity issues, such as ripple, as well as if ac charging for medium power levels, of 400 kW for midsize EVs and covers
it predicts any other source of harm typically via the same OBC used for a 1.5-kV and 3-kA range intended for
to the battery. Because the BMS is fa- slow charging and by using parts of heavy-duty EVs.
miliar with its own OBC, the monitor- the idling drive unit; and dc fast charg- Chinese and Indian EV manufac-
ing and protection function is particu- ing, where most of the power conver- turers operate with dc fast chargers
larly important for offboard chargers, sion takes place outside a vehicle. A specified in the Guobiao/recom-
which the BMS does not know. deeper categorization of the charging mended (GB/T) 20234.3-2015 stan-
The battery voltage of EVs in- options is presented in Figure 2, show- dard published by the China Electric-
creased from fewer than 200 V in early ing how standards classify the alter- ity Council in 2011 and updated in
EVs to more than 800 V in the latest natives differently, while the overall 2015. This standard supports the dc
models [11]. OBCs are purpose de- picture still converges to a common charging of batteries that have maxi-
signed for a specific vehicle platform, scheme: ac charging solutions cover mum ratings of 950 V and 250 A, with
implementing circuit topologies that the lower end of the spectrum, up to a controller area network (CAN) bus
may be scaled up to such voltages, approximately 25 kW, while dc op- communication interface similar to
using already implemented active- tions handle the remaining part, up CHAdeMO’s. This CAN communica-
boosting front ends or (power-factor- to roughly 400 kW, with projections as tion platform was maintained in the
correcting) boost stages. However, high as 900 kW. Additionally, wireless 2018 version of the standard (code-
most already installed dc chargers are charging and battery swapping com- veloped with CHAdeMO) and used
for 400-V vehicles. Thus, newer cars plete the charging ecosystem but are in the ChaoJi charging standard
with a higher battery voltage would beyond the scope of this work. of 2020, with a maximum rating of
not be fully charged or not charged at “Charge de Move” (“CHAdeMO”), 900 kW, 1.5 kV, and 600 A, guarantee-
all. As a consequence, manufacturers the standard promoted by Japanese ing compatibility with legacy char-
equip such cars with an internal dc– automakers and industry, began with gers from both CHAdeMO and GB/T
dc boost stage or offer an upgrade op- a maximum power of 50 kW, which was standards [7].
tion [11], [17]. enough for quickly recharging 24-kWh A fifth charging standard is propri-
Integrated solutions to adjust the batteries but became inconvenient for etary, promoted by Tesla and its su-
dc charging voltage use the available charging batteries of 40 kWh or more. percharging network. The high-profile
drive inverter and motor inductance For these reasons, the consortium up- EV manufacturer decided to avoid the
[18]–[20], and bypass circuits can en- dated its specification to continuously standardization divisions and devel-
able direct charging at stations, which provide 100 kW, in 2017, and it further oped a charging standard dedicated
report a sufficiently high maximum expanded the stipulation to 400 kW in to its vehicles. The company deployed
voltage to the BMS after plugging in. CHAdeMO 2.0, in 2018. Additionally, a a fast-charging network in 2012, which
To avoid interaction with the control third version was released in 2020, was the first sizable system of fast
of charging stations, which have un- enabling an unprecedented rate of chargers worldwide, reaching more
known and currently not further stan- 900 kW to further reduce charging times than 1,500 stations in 2019 [25]. Based
dardized dynamics, these booster and accommodate larger vehicles. on Tesla’s OBC, the current version of
stages typically do not use tight feed- The incompatibilities between the charging stalls is capable of sup-
back for their own controller but wide- vehicles in 2011, mostly associated plying 250-kW peak; upcoming ver-
ly operate with feed-forward behav- with an initial lack of hardware stan- sions will supply 350 kW [25]. The
ior and in an open-loop mode, while dardization, have faded through the company uses a proprietary connec-
any feedback preferably proceeds years. In 2014, the emergence of the tor that might be updated to include
slowly with minimum bandwidth. first and only open charging system, cooling features [26]. For increasing

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EV Charging
Infrastructure

Onboard Offboard
Chargers Chargers

Dedicated Integrated Auxiliary

Others
ac Chargers Chargers dc Chargers

Battery Swapping

Wireless Charging
ac Chargers dc Chargers

ac Charging Standards dc Charging Standards

Specification 1.0 Specification 2.0 3.0/ChaoJi CHAdeMO
SAE J1772 ac Level 1 ac Level 2 dc Level 2 SAE J1772 (CCS-1)
IEC 61851 Mode 1 Mode 2 and Mode 3 Mode 4 IEC 61851 (CCS-2)
GB/T 20334 ac Charging GB/T 20234.2 dc Charging GB/T 20234.3 New GB/T/ChaoJi GB/T 20334
Tesla Mobile Connector and Wall Connector Versions 1–2 Version 3 Version 3 Tesla Supercharger

0 1 2 3
10 10 10 10
Charging Power (kW)

FIGURE 2 – EV infrastructure charging classification. Society of Automotive Engineers (SAE) J1772 and the Combined Charging System (CCS) also
define low-power dc levels (i.e., DC1, DC5, DC10, and DC20) and are mainly used for dc destination charging. They were omitted from the diagram
for clarity purposes. Currently, the third generation of Tesla Superchargers features a maximum power of 250 kW; however, a future expansion to
350 kW is planned. IEC: International Electrotechnical Commission; CHAdeMO: Charge de Move; GB/T: Guobiao/recommended.

compatibility, it includes the type 2 will vary from EV to EV, or, to be the power level from early single-phase
connector, or CCS-2, in Europe and the more precise, from battery to bat- 1 kW and 3.6 kW via 7.2 kW to three-
GB/T version in China. tery and from BMS to BMS. Table 3 phase, 11-kW chargers. It is expected
These updates can be observed summarizes several commercially that the next generation will reach
in Tables 1 and 2. Conventional available EV models to relate the 22 kW (three-phase, 400-V ac, and 32 A).
ac charging, summarized in Ta- discussed charging levels to ac- The dependence on available out-
ble 1, has remained practically tual vehicles. It includes a wide lets and the incompatibility of ground-
unchanged for several reasons, spectrum, from buses and SUVs to referenced, voltage-controlled ac power
among them, the extra on-board premium sedans and compact cars, with the dc current-controlled, voltage-
weight/size and the limited avail- listing battery voltages and capaci- limited needs of vehicle batteries are
able power in houses, depending on ties, charging options, and driving key issues related to OBCs [27], [28].
the voltage and the region. On the ranges. OBCs are constrained by available
other hand, dc chargers, presented power levels, which can be as low as
in Table 2, have experienced impor- Dedicated OBCs 1.8 or 3.6 kVA for many single-phase
tant changes during the past four outlets and as high as 45 kVA for homes
years, with an increased voltage Overview with an excellent grid connection.
range and higher charging rates, in The prevailing method of recharging an Higher power levels might benefit from
response to the availability of lon- EV, including plug-in hybrids, is through medium-voltage access (for which no
ger-range battery packs. Regard- a dedicated OBC. OBCs resulted from standardized interfaces and connec-
less of the maximum power allowed a lack of offboard chargers and from tors exist), which would require exten-
by the various charging standards, small battery capacities, particularly sive safety concepts and is unthinkable
each vehicle ultimately determines during the early days, when plug-in for OBCs right now. Furthermore, the
its actual maximum charging rate, vehicles needed to charge exclusively weight and size of the charger have to
both the overall maximum that the through domestic outlets. The electron- be incorporated into cars, which are
battery accepts and the instant ics, which convert and condition the already crowded with components and
level, which is given by the battery power, are carried along and resemble highly package sensitive, besides af-
state, temperature, and related as- other battery chargers, such as those fecting mileage. For overnight charging
pects. Hence, the charging time of laptops. There is a trend to increase and limiting the stress on batteries and

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TABLE 1 – AC CHARGING STANDARDS.

SAE J1772 GB/T 20234-2 TESLA

IEC 61851

MODES MOBILE WALL

AC LEVEL 1 AC LEVEL 2 MODES 1 2–3 GB/T CONNECTION CONNECTION
Maximum power 1.9 kW 19.2 kW 4 kW (13.3 kW) 8 kW 7 kW (12.8 kW) 1.9 kW (7.7 kW) 2.8 kW (11.5 kW)
(22 kW)
Input voltage 120 V, single 240 V, split 250 V, single 250 V, 250 V, single phase (400 V, 120 V, single 208 V, single phase
phase phase phase (480 V, single phase single phase) phase (240 V, (250 V, single
three phase) (480 V, single phase) phase)
three
phase)
Maximum 16 A 80 A 16 A 32 A 32 A 16/32 A 48 A
current
Communication PLC PLC None PLC CAN CAN CAN
Region United States, Japan, South Europe, Australia China, India Global Global
Korea
Related • IEC 61851-22/23 • IEC 61851-22/23 • GB/T 20234-2 • IEC 62196-2 • IEC 62196-2
standards • IEC 62196-2 • IEC 62196-2 • IEC 62196-2
• SAE J1772-2017
Vehicle to device Under development Under development Under development No No
Plug type

Example  Blink level 2,  Siemens  ByD EVA

wall mount: VersiCharge: 080KG/01:
208–240 V, 230 V, three 440 V,
single phase, phase, three
30 A, 7.2 kW 32/22 kW phase,
126 A,
80 kW

PLC: power line communication.

the grid, however, OBCs might be here topologies, these constraints produce a a subsequent dc–dc converter. The
to stay. need for a relatively large dc link capaci- latter feeds the battery and is usually
tance to decouple both sides. Topolo- galvanically isolated for safety, mini-
Requirements gies should also provide the flexibility mizing touch currents [3], [5]. The
Key OBC targets include high maximum to deal with practically any ac condi- dc–dc stage is now almost exclusively
power, small size, and light weight. Ef- tions worldwide, i.e., a voltage range of resonant, typically an inductor–induc-
ficiency is also important, as it affects at least 110–240 V for single- and three- tor capacitor (LLC) with two or four
the charging duration, cost of recharg- phase supplies. switches [29], [30], which provides
ing, and cooling requirements. For effi- high efficiency as well as transformer
ciencies above 90%, however, a further Topologies utilization, which is important for the
reduction of cooling becomes more rel- The majority of the commercially trend toward higher powers and volt-
evant to vehicle manufacturers. Modern available OBCs uses two-stage topolo- ages for 800-V architectures [11].
OBCs face grid and battery constraints gies (Figure 3). Typically, a grid-side Such is the case for the second
to achieve sufficient power quality (IEC passive rectifier feeds a boost con- generation of OBCs used by General
61000); in particular, chargers that reach verter operated as a power factor cor- Motors in the Volt [Figure 3(a)]. A PFC
higher power levels have to limit cur- rector (PFC), which supplies a dc link stage formed by a passive diode bridge
rent ripples and consequently mini- large enough to absorb power fluctua- and a two-channel-interleaved boost
mize effects on battery health. In many tions and decouple the first stage from perform the grid connection. These

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TABLE 2 – DC CHARGING STANDARDS.

GB/T TESLA
CHAdeMO CCS-1 CCS-2

Maximum 400 kW 350 kW 350 kW 237.5 kW 350 kW

power*
Typical power † 50 kW 312 kW 350 kW 60 kW 250 kW
Output voltage 50–1,000 V 200–1,000 V 200–1,000 V 250–950 V 300–480 V
Maximum 400 A 500 A 500 A 250–400 A 800 A
current
Communication CAN PLC PLC CAN CAN
Region Global United States, South Korea Europe, Australia China, India Global
Related • IEC 61851-23/4 • IEC 61851-23/24 • IEC 61851-23/24 • GB/T 20234-3-2015 • IEC 62196-3
standards • IEC 62196-3 • IEC 62196-3 • IEC 62196-3 • IEC 62196-3
• JEVS G105-1993 • SAE J1772-2017
Vehicle to device Yes Under development Under development Under development No
Plug type

Time/100 km‡ 13.73 min 4.4 min 1.96 min 11.44 min 2.74 min
Range/5 min§ 36.4 km 113.54 km 254.73 km 43.67 km 181.95 km

Examples  Delta Ultra  Charge Point  ABB Terra HP:  ABB Terra  V3 Supercharger:
Fast Charger: Express Plus: 150–920 V, GB 184MVZ: 450 V, 250 kW
50–550 V, 200–1,000 V, 500 A, 200–750 V,
125 A 390 A, 156 kW 350 kW 300 A, 3 × 60 kW
(CHAdeMO);
170–1,000 V,
300 A (CCS);
150 kW
maximum
*Based on the maximum rating specified in the standard.
†
Maximum power in the market.
‡
The calculation is an approximation assuming the power is kept constant during the charging process using the commercial example.
§
The comparison is made considering the 50-kWh usable battery capacity of the Tesla Model 3 Standard Range Plus, its 409 km WLTP range, and the rated
power of the commercial example.
JEVS: Japanese Electric Vehicle Standard.

converters enable an intermediate from single- and three-phase inputs, Further improvements reduce the
400-V dc voltage, which is subsequent- depending on the country, reaching number of stages to lower losses and,
ly adjusted through a resonant dc–dc 7.5 and 11.5 kW, respectively. This especially, costs. Replacing the pas-
stage to recharge the battery pack. structure is also used as a power elec- sive diode rectifier and boost-stage PFC
In the case of Figure 3(a), this dc–dc tronics building block (PEBB) for the with a bridgeless PFC topology [32]
stage is a resonant four-switch LLC newer generation of the company’s can increase efficiency because there
full-bridge converter, which, through 250-kW V3 Superchargers. Other mar- are fewer diode forward voltage drops
the introduction of a resonant tank kets are aiming for bidirectional OBCs and a lower semiconductor count in
and a variable switching operation, to support upcoming vehicle-to-de- single-phase topologies. Bridgeless al-
can lead to substantial reductions in vice (V2D) applications, as shown in ternatives, though, lead to the common-
conversion losses [30], with reports of the proprietary OBC from Hyundai mode floating of the dc link ground ver-
95% efficiency at the rated 3.6 kW. [31] [Figure 3(c)], where the grid con- sus the grid neutral point, impacting the
A similar trend was adopted by nection is performed through a single- electromagnetic interference, filtering,
Tesla in the new version of the com- phase active front end, followed by a and sensor signal amplification [33].
pany’s OBC [Figure 3(b)], which dual active bridge to adjust the volt- Active front ends, which are more
features higher efficiency and a full- age to different architectures. This bi- prominent at higher power levels and
bridge resonant LLC as the dc–dc directional grid connection enables a in offboard chargers (described in the
stage. The converter is composed of driver to use limited battery capacity following) are uncommon due to their
three identical channels and has an to power devices and to employ the cost [34]. Matrix converters to turn the
active front end, which can source car as a generator. 50/60-Hz input into an intermediate

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(a) (e)

ac EMI ac
Grid Filter Grid
RB-IGBT e-Machine Traction EV Battery
Single-Phase Two-Channel LLC resonant Full Bridge EV Battery EMI Filter Rectifier Windings Inverter Pack
Passive Boost PFC Pack
Rectifier
(b) (f)

dc
dc
ac EMI ac EMI
Grid Filter Grid Filter
EV Battery e-Machine Triple H-Bridge Matching EV Battery
Single-Phase/ LLC resonant Full Bridge Pack Windings Inverter/Charger dc-dc Converter Pack
Three-Phase Active Rectifier
(c)
(g)

dc
ac EMI dc
Grid Filter
ac EMI
Single-Phase Bidirectional Dual Active Bridge Converter EV Battery Grid Filter
Active Rectifier Buck/boost Pack Passive e-Machine Traction Matching dc EV Battery
Rectifier Windings Inverter Transformer Pack
(d)
kW
22 (h)
d Int
–

te
1.9

eg
a
Dedic

rated
ac EMI
Grid Filter Charging
Converters
Indirect Matrix Converter GaN HEMT EV Battery ac EMI e-Machine Traction EV Battery
(Si-Based Unfolding Rectifier Output Full Bridge Pack Grid Filter Windings Inverter Pack
GaN HEMTs Full Bridge) O ff b a r d
o
W

k
0
50–40

5 × 3 PEBBs to Reach 50 kW for Terra 53/54 Three PEBBs to Reach 150 kW for Terra HP150
(i) (j)

Sc
ac EMI MVac Isolation
Grid Filter Grid Transformer
EV Battery Input Filter Active Rectifier Three-Channel EV Battery
Single-Phase LLC Resonant Half Bridge
Pack Interleaved Buck Pack
Passive Rectifier with Reconfigurable Output
(Full Bridge/Doubler)
13 × 3 PEBBs to Reach 150 kW for Supercharger V2
(k)
(l)

MVac Input
MVac Input Distribution Grid Filter
Phase-Shifting EV Battery
Grid Filter transformer
Transformer Three-Phase Boost Buck Switching Pack
EV Battery
Single-Phase Boost Phase-Shifted Full Bridge Passive PFC dc-dc Matrix
Pack
Passive Rectifier PFC Rectifier

(m) (n)

MVAC Input
ac Grid
Grid Filter
Phase-Shifting EV Battery Grid Filter
Transformer Pack Three-Phase Galvanically Isolated dc-dc Switching EV Battery
Vienna Rectifier Three-Level Switching Active rectifier Matrix Pack
Buck Matrix

FIGURE 3 – Power electronics for EV charging infrastructure. Dedicated OBCs: the (a) OBC for the second-generation Volt, (b) Tesla Model 3/Y OBC,
(c) Hyundai vehicle-to-device OBC concept, and (d) Hella Electronics/GaN Systems high-efficiency OBC. Onboard integrated chargers: the
(e) Renault Chameleon, (f) Valeo dual-inverter charger, (g) Continental AllCharge System, and (h) galvanically isolated traction integrated charger
concept. Offboard high-power chargers: the (i) ABB Terra 53/54 50-kW fast charger, (j) ABB Terra HP 150-kW high-power charger, (k) Tesla V2
Supercharger, (l) Porsche Modular Fast Charging Park A, (m) Porsche Modular Fast Charging Park B, and (n) ENERCON E-charger 600. EMI: elec-
tromagnetic interference; LLC: inductor–inductor capacitor; Si: silicon; GaN: gallium nitride; HEMT: high-electron mobility transistor; RB: reverse
blocking switching device; IGBT: insulated-gate bipolar transistor; PEBB: power electronics building block; MVAC: medium-voltage ac; PFC: power
factor corrector.

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high frequency for the transformer safety issues. In addition, most in- detailed in Figure 3(h), based on six
primary side promise a further elimi- tegrated chargers inversely use the stator winding strands, which are nor-
nation of stages but suffer from a high drive inverter as a boost stage, lead- mally connected in series to constitute
semiconductor count if single- and ing to significant current ripple on a three-phase set, while a relay recon-
three-phase inputs are required [35]. the dc side. Whereas the ripple may figures them for charging [42]–[44].
Furthermore, they suffer from the be negligible at low power levels, the The inverter operates as an active
need to concurrently fulfill the grid use of the (high-power) inverter might front end and generates high-quality
code and provide ripple-free battery promote faster charging and suggest currents on the ac side. The use of re-
current. Instead, so-called indirect ma- additional filtering, e.g., through in- lay-based switching devices and a me-
trix converters, which resemble active creased dc-link capacitance [38]. Nev- chanical clutch temporarily turns the
front ends but perform the power fac- ertheless, these chargers are gaining machine into an isolation transformer
tor correction at the dc–dc input stage, attention in the industry, with the one connected to the grid, while the trac-
have been proposed and evaluated. pioneered in a production vehicle by tion components operate as a battery
A team from Hella Electronics, Ket- Renault being the most representative charger. Several similar concepts use
tering University, and GaN Systems [39], [40]. machines with six or more windings
implemented a gallium nitride ver- The circuit diagram in Figure 3(e) to provide galvanic isolation and im-
sion, which—avoiding rectifier loss— illustrates the addition of a current prove the current filtering [38], [45].
achieved a maximum 98% efficiency source rectifier based on reverse-
for single-phase 7.2-kW operation [36]. blocking insulated-gate bipolar tran- High-Power Offboard
This topology, shown in Figure 3(d), sistors and corresponding filtering Charging Stations
still requires a relatively large dc fil- elements to enable a grid connection
ter stage to avoid producing second- that is suitable for single- and three- Technology of Latest
order harmonics on the battery side. phase ac grids; it can also act as a dc Charging Stations
A three-phase version uses three sin- interface. The scheme reconfigures the Recent breakthroughs enabled the
gle-phase modules and increases the traction system as a charger through an birth of high-power fast chargers,
power density from 3.3 to 5 kW/L, for accessible motor neutral point. The cir- also known as ultra- and extremely
an overall power of 20 kW [37]. The cuit employs the windings of the motor fast chargers. These are designed to
second harmonic of the single-phase as the dc link element and the traction be future-proof, as they are able to de-
version accordingly turns into a small- inverter to adjust the current injected liver more than 350 kW to the battery
er sixth-order harmonic. into the battery. This power conver- pack, although currently available EVs
sion system enables a power range have not reached that charging power
Traction-Integrated OBCs from 3 to 44 kW and is complemented level, as shown in Table 3. In addition,
An interesting area in the EV industry by a bidirectional variant for future this family of chargers aims for com-
concerns high-power integrated OBCs V2D implementation [40]. An alterna- patibility with future 800-V vehicles
to optimally trade off cost, volume, tive architecture that avoids the re- while maintaining compatibility with
and weight restrictions [3]. This is quirement of an accessible machine legacy 400-V systems. Most manufac-
motivated by the fact that most mod- neutral is discussed in [41]. turers have achieved this update by
ern EV traction systems are rated at Similar designs have been devel- modularizing their designs. Modular-
more than 50 kW and are idling during oped by other automotive manufactur- ity benefits from economy-of-scale
charging. These power ratings enable ers. The circuit patented by Valeo [19] effects and offers different shares of
using the systems as components of [Figure 3(f)] is based on two traction current and voltage for the same pow-
high-power traction-integrated OBCs inverters connected to split windings er through reconfiguration; thus, 400-
[5] that directly compete with state- in a permanent-magnet synchronous and 800-V vehicles can be charged
of-the-art offboard dc fast chargers motor, and it facilitates generating with high power and higher efficiency
in terms of charging speeds. Such a high-voltage intermediate dc link, at a partial load.
integrated OBCs do not involve the which is later adjusted to the battery ABB has set a benchmark with its
substantial investment in dc chargers voltage through a matching dc–dc Terra 53/54 series [Figure 3(i)], its
that is often not easily redeemed [6]. stage. The high-power OBC by Conti- best-selling generation of chargers
This approach can enable higher nental [Figure 3(g)] includes addition- based on PEBBs. The modular system
charging power levels without add- al components in the traction unit: a is built by replicating the same circuit
ing many additional elements, but it passive rectifier and a line filter are several times. Depending on the out-
still depends on the available power connected to the accessible ground of put requirements, the number of ac-
sources, namely single- and three- the induction machine [20] in addition tive stages changes accordingly. To
phase power outlets. Consequently, to a matching dc–dc converter to in- meet the isolation requirements and
to maintain minimal complexity, these terface 400- and 800-V batteries. feature higher power levels in addition
chargers often lack galvanic isolation, Alternatively, a galvanically iso- to compactness, an alternative struc-
which can lead to touch current and lated traction-integrated charger is ture features an isolated dc–dc stage

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TABLE 3 – THE CHARGING SPECIFICATIONS OF SOME COMMERCIALLY AVAILABLE EVs.

BATTERY RATED ENERGY ONBOARD CHARGING MAXIMUM CHARGING DRIVING

MODEL MANUFACTURER VOLTAGE (USABLE) POWER (TIME)* POWER (TIME)* RANGE‡
eCitaro (bus) Mercedes-Benz 400 V 182 kWh N/A †
300 kW (OPP ) (29 min) N/A

7900 Electric (bus) Volvo 600 V 150 kWh 11 kW (10.9 h) †

300 kW (OPP ) (24 min) N/A

Model S, long range Tesla 400 V 100 kWh (95 kWh) 11.5 kW (10.25 h) 250 kW (38 min) 624 km
E-tron 55 Quattro Audi 396 V 95 kWh (86.5 Wh) 11 kW (9.25 h) 150 kW (26 min) 436 km
EQC 400 4Matic Mercedes-Benz 405 V 85 kWh (80 kWh) 7.4 kW (10.5 h) 150 kW (31 min) 417 km
Taycan 4S Porsche 800 V 79.2 kWh (71 kWh) 11 kW (9 h); 9.6 kW 270 kW (21 min) 407 km
(9.5 h) United States
Model 3, long range Tesla 360 V 75 kWh (72.5 Wh) 11.5 kW (7.75 h) 250 kW (22 min) 560 km
Polestar 2 Polestar (Volvo) 450 V 75 kWh (72.5 Wh) 11 kW (7.75 h) 150 kW (31 min) 470 km
Bolt Chevrolet 350 V 62.2 kWh (58 kWh) 7.4 kW (8.3 h) 50 kW (66 min) 423 km
Leaf e+ Nissan 360 V 62 kWh (56 kWh) 6.6 kW (11.5 h) 100 kW (35 min) 385 km
Zoe ZE50 Renault 400 V 54.7 kWh (52 kWh) 22 kW (3 h) 50 kW (56 min) 395 km
Ioniq Hyundai 320 V 40.4 kWh (38.3 kWh) 7.2 kW (6.25 h) 100 kW (20.6 min) 294 km
Leaf Nissan 360 V 40 kWh (36 kWh) 6.6 kW (6.5 h) 50 kW (40 min) 270 km
*
The charging times and power levels are based on information published by the manufacturers. Conventional charging considers the time from 0 to 100%
charged, while fast charging considers 10–80%.
†
OPP: Opportunity Charging Standard, a pantograph-based solution used for buses and other heavy-duty vehicles.
‡
Official driving range according to the Worldwide Harmonized Light-Duty Vehicle Test Procedure.

based on a proprietary half-bridge battery. This structure, used in the buck stages that ensure a low current
LLC converter, as displayed in Fig- first two versions of the supercharg- ripple, in contrast to other topolo-
ure 3(i) [46]. The three-channel LLC ing network, facilitates single- and gies. Depending on the ripple require-
includes a reconfigurable secondary three-phase ac inputs with their cor- ments, several dc–dc channels can be
rectifier, which enables interfacing responding charging rates. A combi- included.
with 400- and 800-V vehicles since it nation of 13 units in a single cabinet is The structure appears to be flex-
operates as a regular full bridge and able to charge one vehicle with up to ible for further developments, and it
as a voltage doubler by closing switch 150 kW, at a documented efficiency of eventually might shift the isolation
Sc in the 54 series, which features a 92% [10]. The third supercharger gen- to the dc–dc stage or combine both
95% peak efficiency. Another example eration is based on the PEBB shown in structures, depending on volume/
of this modular approach appears in Figure 3(b) and reaches 250 kW. space requirements [48]. Alternative-
Figure 3(j), where the Terra high-pow- Another company that decided ly, implementations using a Vienna
er series is presented. These chargers to promote this trend is Porsche rectifier have been reported to adapt
reach 150 kW per cabinet, while each [Figure 3(l) and (m)], with its 800-V ar- the charging stations depending on
cabinet is based on the regenerative chitecture that risked incompatibility site requirements [49]. This alterna-
motor drives’ 50-kW modules, featur- with many other dc charging stations tive structure is given in Figure 3(m),
ing low-frequency galvanic isolation when it was introduced but presented where the different structure of the
and a reported efficiency of 94% at a a modular fast-charging infrastruc- dc link enables modifying the battery
full load. To reach higher power levels, ture [48], [49] that could be scaled by charging converter for an interleaved
this unit is replicated several times to increasing the number of PEBBs. The three-leg buck, further improving the
reach a maximum of 600 kW for buses charger implements the galvanic iso- output current ripple. The manufac-
and larger vehicles. lation at the input side through a grid turer further offers a battery-support-
Modularity can also be considered transformer, which can be fed from a ed charger particularly for sites with a
the key for the success of Tesla’s super- medium-voltage grid, exploiting the weak grid or otherwise limited power
charging network, as the company’s relatively low price of cast-resin grid that could nevertheless provide up to
offboard charging stations are based transformers, at the cost of larger 320 kW for charging [50]. The system
on the Model S and Model X OBCs [47]. size. A phase-shifting transformer can has high-frequency galvanic isolation
The two-stage power conversion cir- improve the power quality on the grid to ensure compactness, which also
cuit [Figure 3(k)] involves one passive side. Subsequent rectifiers with suffi- ground-lifts the internal battery to the
single-phase bridge per channel with cient power factor correction generate same electric potential as the vehicle,
a boost PFC, followed by a phase-shift- an isolated dc bus at a high voltage, and reportedly has a peak efficiency
ed full bridge to adequately supply the which is stepped down by the output of 98%. An active front end gives the

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hardware bidirectionality and pre- cost and a high robustness [48]. How- voltages, currents, and, consequently,
pares it for a range of grid services. ever, higher-frequency isolation, e.g., ac input power. The most relevant
An interesting high-power charg- through LLCs and dual active bridge standardization items and standards
ing approach developed by Enercon, converters, facilitates substantial size are summarized in Table 4.
otherwise known for wind turbines, reductions. Size particularly matters
is shown in Figure 3(n). The topology when chargers are to be installed on Metering for dc Charging
also features a high degree of modu- sidewalks. Solid-state transformers Energy metering is another impor-
larity: The active rectifier stages are as a modular assembly of galvani- tant practical aspect of dc chargers.
built using 60-kW modules from wind cally isolated dc–dc converters would Electricity retailing has to comply
energy converters, while the dc–dc continue this trend and may enable a with countries’ diverse weights-and-
stage includes six to 12 galvanically compact medium-voltage grid inter- measures regulations and typically
isolated channels based on a reso- face [10]. pass certified calibration through an
nant full bridge [51], [52]. By means accredited body (which, in turn, usu-
of a switching matrix, the E-Charger System-Level and Practical Aspects: ally has to comply with International
600 is able to feed up to four charging Standardization Organization for Standardization/IEC
points of 350 kW each, with a cumula- As for many industrial systems, the 17025). The future might bring transla-
tive power of 600 kW. One of the main circuit topology of the power train is tional harmonization, for which some
features of this concept concerns the an important aspect, but the majority early examples exist, such as the Euro-
grid service functionality of the rec- of the development effort is typically pean Measuring Instruments Directive.
tifier, inherited from wind turbines, concentrated on peripheral devices, However, calibrated dc meters
enabling a sophisticated EV charging which ensure the required perfor- that fulfill legal requirements (accu-
solution while contributing to grid sta- mance, quality, and safety. Whereas racy, repeatability, reproducibility,
bility, with up to 500 kVA of reactive OBCs are generally purpose designed measurement right at the connector,
power in addition to other ancillary for a specific car or platform, charging and so on) have just recently become
services [51]; the design has a 94% re- stations are an interfacing technology available. These meters have to ex-
ported efficiency. that has to interact with systems that actly measure the energy released to
are beyond the control of manufactur- the car at the connector, guarantee-
Topology Aspects ers. Thus, standardization plays an ing that offboard power losses are
Interestingly, high-power charging essential role. For historical reasons, not charged to the user. Therefore,
stations have not converged into one standardizing charging stations began the user must have access to rather
topology. The variety is reflected by at the national level, and various lo- detailed measurement data, verifica-
the grid interface [53]. As outlined in cal industry consortia subsequently tion methods, and secure storage for
Figure 3, the options range from bidi- formed and were to some degree har- charging history documentation. To
rectional active front ends with two- monized in IEC 61851. Individual parts avoid this problem, early operators
and three-level topologies [51], [54] to of IEC 61851 are still under develop- typically sold parking with a charg-
unidirectional passive rectifiers with ment. New additions reveal trends ing option instead of power. Currently,
boost-type PFCs [47], bridgeless PFC that include bidirectional power flow, metering is considered a task of the
stages [55], and Vienna rectifiers [49]. methods to implement isolation, and charging station. However, the ongo-
Bridgeless PFC stages are mostly used multioutlet chargers. ing discussion includes the alternative
for lower power levels in single-phase Particularly in the United States, with onboard energy metering as a
configurations [56]. Delta-wye trans- Society of Automotive Engineers J1772 potentially better solution, where, for
former configurations can further en- takes the role of IEC 61851, but it is instance, all history and usage data
able improving grid-side power quality already widely in harmony with the could remain with a car’s owner.
and the omission of additional power latter. These standards list connec-
factor correction [48]. Bidirectional tor types and specify the required Safety
grid interfaces would be paramount quality of the voltage and the cur- Charging stations and any kind of off-
for vehicle-to-grid and vehicle-for-grid rent; the common safety concepts board chargers are unknown black
concepts, but they are not currently of a charger connected to a vehicle; boxes to an EV. Functionally, an EV op-
in use. Therefore, they seem most in- charging modes and ranges; the en- erates the dc charger as a high-power,
teresting for battery-backed chargers, tire procedure for connecting, hand- high-voltage energy supply, regularly
which support and could locally stabi- shake signals, contactor states, and sending (on the order of seconds) up-
lize sites that have weak grids [50]. communication; and test procedures. dated current and voltage commands
High-power chargers almost exclu- Electromagnetic compatibility and based on the electrical and thermal
sively implement galvanic isolation grid codes are challenging for charg- state of the vehicle’s battery; the char-
between vehicles and the grid. Grid ing stations since no charging station ger follows the directives within 1 s.
transformers with a ground-lifted component can be operated at its ide- With respect to safety, the vehicle en-
secondary side promise the lowest al load point but must cover a range of trusts itself to the black-box charging

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station and turns off its own isolation

monitoring when it closes its charging
TABLE 4 – EVSE-RELATED STANDARDS.
contactors at the end of the precharg-
STANDARDIZATION
ing phase. The relevant industry stan- ASPECT STANDARD DESCRIPTION
dards, therefore, specify the interfaces EV conductive charging IEC 61581 Part 1: general aspects
and the communication between an system Part 3-3: charging and battery swapping for light EVs
EV and a charger, and they establish Part 21: OBC, electromagnetic compatibility compliance,
and so on
a combined safety system to protect Part 22: ac EV charging stations
users and equipment. In this sense, Part 23: dc EV charging stations (currently being updated)
Part 24: further communication aspects of dc charging
important aspects are that both the
charging station and the vehicle moni- Grounding and safety IEC 61581-23, UL 2231, IEC 61581-23 contains three so-called systems, A, B,
measures IEC 61557, IEC 609050 and C, specified in normative annexes, representing the
tor the charging current, the current CHAdeMO, GB/T, and CCS.
quality, overcurrent and short cir- UL 2231 covers personal protection systems for EVSE.
IEC 61557 specifies electrical safety in low-voltage
cuits, the correct plug connection distribution systems.
and interlocking, isolation, the integ- IEC 60950-23: information technology equipment safety
rity of their controller, and contactor Connectors and inlets IEC 62196 Part 1: general aspects
failures. Both the EV and the charger Part 2: ac vehicle couplers
Part 3: dc and ac–dc vehicle couplers
can report errors to the other side
through the control signals in the Cables IEC 62893 Charging cables for EVs
charging cable.
Electromagnetic IEC 61000, CISPR 32 CISPR 25 and CISPR 16 also apply if vehicle electronics
In case of critical failures, a station compatibility should operate flawlessly (including the radio tuner).
has to rapidly react and isolate the fault Grid codes IEC 61000 Partly covered
by opening contactors on the output
side and/or the grid side. In some cas- Medium-voltage IEC 61581, UL J1772, IEC The connection to medium-voltage grids requires
connection 61508/ISO 26262, IEC compliance with the individual conditions of the grid
es, the station must discharge the high 60364 operator, which can differ from site to site.
voltage that is below the safe extralow IEC 61851 and UL J1772 contain several basic safety
voltage (SELV) level of 60 V and the requirements.
IEC 61508/ISO 26262 covers generic functional safety,
residual energy levels below 20 J (typi- requiring formal risk assessment and mitigation.
cally within 5 s, as given in IEC 60950). IEC 60364 deals with general aspects of electrical devices
(the United States uses the domestic National Electrical
For several more specific failures, such Code).
as interruption of the control pilot, the
Inductive charging IEC 61980, SAE J1773 Part 1: general aspects
current has to be turned down within Part 2: communication between EVs and EVSE
milliseconds (e.g., fewer than 5 A in Part 3: requirements for magnetic fields in wireless power
transfer
30 ms, with the subsequent opening of
the contactors within 100 ms). Battery swapping IEC 62840 Part 1: general overview
Part 2: safety requirements
During charging, a vehicle and a
Vehicle to grid ISO/IEC 15118, IEC ISO 15118: vehicle-to-grid communication interface
driver are highly vulnerable. Most 61850-90-8 IEC 61850-90-8: communication networks and systems
modern cars use several hundred for e-mobility
volts in their battery and therefore UL: Underwriters Laboratories; CISPR: International Special Committee on Radio Interference.
maintain an isolated high-voltage
drive train (IT system) for safety, and
they monitor the resistance and the touchable conductive parts must be for capacitive isolation exist [57].
capacitance between the IT system connected to a ground, which in some There are commercially available
and the chassis. Practically all dc countries must be a protective earth charging stations that have various
charging stations use galvanically iso- that must be monitored for continu- sites for the isolation barrier, such
lated dc outputs (IEC 61851-23 and Un- ity. Accordingly, the vehicle chassis is as on the low-frequency ac side; in
derwriters Laboratories 2231), which connected to the ground through the an intermediate dc–dc converter be-
isolate the charged vehicle battery charging cable to protect the operator tween the ac interface and the output
from the ground and from other vehi- against electric shock in case of any dc stage, which is typically resonant
cles to facilitate a single insulation fail- insulation breakdown and similar fail- and without more sophisticated con-
ure in the high-voltage circuit without ures. If the dc charger has a plug on trol; and, rarer, in the output stage. In
harm and to minimize touch currents. its ac side, IEC 61851-23 mandates the addition, EVs supervise the auxiliary
This isolation should be continuously inclusion of a ground fault current in- supply voltages below the SELV level
monitored (e.g., with isolation moni- terrupter, also known as residual cur- via an isolation monitoring device. As
tors per IEC 61557) for the protection rent device. soon as an EV is charging, it delegates
of the user, and the touch current Isolation is almost exclusively of an such tasks to the charger. Connec-
must be kept to fewer than 3.5 mA. All inductive nature, although concepts tors, on the other hand, are typically

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designed in such a way that the ground (ANID/FONDAP/15110019), ANID/EQM/ systems and the modeling, modula-
would connect first during plugging-in 180215 and ANID/REDES/190108 proj- tion, and control of power electron-
and detach last when disconnecting. ects; the FIAEC01-2019UCSC project; ics converters applied to renewable
On the other hand, the protective con- the Duke University Energy Initiative; energy technologies. He is a Senior
trol signals, e.g., the control pilot (CP) and National Science Foundation proj- Member of IEEE.
and the proximity pilot (PP) for CCS, ect 1608929. Financial support was Stefan M. Goetz (smg84@cam
connect last and disconnect first, as provided by the Horizon 2020 Spartan .ac.uk) earned his Ph.D. degree in medi-
they can initiate energizing the cable project (grant 821381) and the Con- cal applications of power electronics
upon the proper handshake with the sejeria de Economia, Conocimiento, from the Technical University of Mu-
car (CP) and the proper connection of Empresas, y Universidad, Secretaria nich, Germany, and Columbia Univer-
the plug (PP). General de Universidades, Inves- sity, New York, in 2012. He is a faculty
tigacion y Tecnologia, under project member at Duke University, Durham,
Conclusion P18-RT-1340. These contributions are North Carolina, 27708, USA, and the Uni-
As we enter another decade of EVs gratefully acknowledged. versity of Cambridge, Cambridge, CB2
in the mainstream car market, tech- 1TN, UK. His research interests include
nological developments and coordi- Biographies precise high-power pulse synthesizers
nated efforts from private and public Sebastian Rivera (s.rivera.i@ieee for neuroscience and medicine, inte-
sectors are shaping a healthy ecosys- .org) earned his Ph.D. degree in elec- grative power electronics solutions for
tem. The main objective of this article trical and computer engineering from microgrids and electrical vehicles, and
is to provide a detailed view of the Ryerson University, Toronto, Canada, high-power charging. He is a Member of
charging standards updates so as to in 2015. He is an assistant professor IEEE.
highlight the advances in EV charg- of engineering and applied sciences Ricardo Lizana (ricardolizana@
ing and motivate the conception of at Universidad de los Andes, Santia- ucsc.cl) earned his D.Sc. degree in
new breakthroughs. Additionally, an go, 7620086 Chile, and an associate electronic engineering from Univer-
industry overview of the leading tech- researcher at Advanced Center for sidad Tecnica Federico Santa Maria,
nologies highlights that there is not a Electrical and Electronic Engineering Chile, in 2015. He is an assistant pro-
single dominant technology, given the (AC3E) at Universidad Tecnica Federi- fessor in the Department of Electrical
many factors involved in the charging co Santa Maria, Valparaiso, 2390123, Engineering, Universidad Catolica de
process, depending on the specific Chile, and the Solar Energy Research la Santisima Concepcion, Concepcion,
charging situation. In this sense, the Center, Santiago, 8370451, Chile. His 4090541, Chile. His research interests
idea was to study the differences in research interests include dc distribu- include high-power converters, high-
the market and provide an insightful tion systems, electric vehicle charg- voltage dc transmission systems, and
discussion. ing infrastructure, and high-efficiency renewable energy systems. He is a
Finally, modularity appears to be power conversion. He is a Senior Mem- Member of IEEE.
the key to success to solve the differ- ber of IEEE. Enrique Romero-Cadaval (ercadaval@
ences among charging standards and Samir Kouro (samir.kouro@ieee ieee.org) earned his Ph.D. degree
to enable versatility in the various .org) earned his Ph.D. degree in elec- in industrial electronic engineering
power electronics solutions that are tronics engineering from Universidad from the Universidad de Extremadura,
available. In terms of grid support, as Técnica Federico Santa Maria (UT- Badajoz, Spain, in 2004. He teaches
we advance to the second decade of FSM), Chile, in 2008. He is a profes- power electronics and conducts re-
the EV market, we can finally see com- sor in the Department of Electronic search in the Power Electrical and
mercial products aiming to develop bi- Engineering and serves as director Electronic Systems R&D Group,
directional OBCs to diversify the use of innovation and technology trans- School of Industrial Engineering, Uni-
of the EV battery and to develop high- fer at UTFSM, Valparaiso, 2390123, versidad de Extremadura, Badajoz,
power chargers that, instead of only Chile. His research interests include 06006, Spain. He is a past president of
loading the grid, are able to support power electronics, renewable energy the IEEE Power Electronics Society/
and contribute to grid stability, e.g., (photovoltaic and wind), and energy IEEE Industrial Electronics Society
through solutions from other power transition technologies. He is a Senior Joint Spanish Chapter and the current
sectors. In addition, newer charging Member of IEEE. IEEE Spanish Section Chapter coordi-
stations include stationary batteries Sergio Vazquez (sergi@us.es) nator. He is a Senior Member of IEEE.
to further support grid integrity, shift earned his Ph.D. degree in industrial
demand, and reduce peak power con- engineering from the University of Se- References
[1] “Global EV Outlook 2020,” International En-
sumption. ville, Spain, in 2010. He is an associate ergy Agency (IEA), Paris, France, Tech. Rep.,
professor in the Department of Elec- 2020. [Online]. Available: https://www.iea.org/
reports/global-ev-outlook-2020
Acknowledgments tronic Engineering, University of Se- [2] “Electric Vehicle Outlook 2020,” Bloomberg
This work was supported, in part, by ville, Seville, 41004 Spain. His research NEF, New York, NY, Tech. Rep. Accessed: Oct.
2020. [Online]. Available: https://about.bnef.
the AC3E (ANID/Basal/FB0008), SERC interests include power electronics com/electric-vehicle-outlook/

14 IEEE INDUSTRIAL ELECTRONICS MAGAZINE ■ MONTH 2021

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[3] M. Yilmaz and P. T. Krein, “Review of battery Veh. J., vol. 8, no. 1, pp. 237–248, 2016. doi: ger using e-mode GaN HEMTs for electric ve-
charger topologies, charging power levels, 10.3390/wevj8010237. hicles,” SAE Int. J. Alt. Powertrains, vol. 5, no. 1,
and infrastructure for plug-in electric and [21] M. Jaensch, J. Kacetl, T. Kacetl, and S. Götz, Apr. 2016. doi: 10.4271/2016-01-1219.
hybrid vehicles,” IEEE Trans. Power Electron., “DC charging of an intelligent battery,” U.S. [37] H. Bai, A. Brown, M. McAmmond, and J. Lu, “A
vol. 28, no. 5, pp. 2151–2169, 2013. doi: 10.1109/ Patent Appl. US2019/0288527A1, Sept. 19 2019. modular designed three-phase 98%-efficiency
TPEL.2012.2212917. [Online]. Available: https://patents.google 5kW/L On-board fast charger for electric vehi-
[4] D. Bowermaster, M. Alexander, and M. Duvall, .com/patent/US20190288527A1 cles using paralleled e-mode GaN HEMTs,” in
“The need for charging: Evaluating utility in- [22] Charging systems and methods for electric ve- Proc. WCXTM 17: SAE World Congr. Experience,
frastructures for electric vehicles while pro- hicles, by M. Shen, P. Chen, and F. Guo. (2020, Mar. 2017. doi: 10.4271/2017-01-1697.
viding customer support,” IEEE Electrific. Mag., Apr. 21). U.S. Patent 10,625,626 B2 [Online]. [38] A. S. Abdel-Khalik, A. Massoud, and S. Ahmed,
vol. 5, no. 1, pp. 59–67, Mar. 2017. doi: 10.1109/ Available: https://patents.google.com/patent/ “Interior permanent magnet motor-based iso-
MELE.2016.2644559. US10625626B2 lated on-board integrated battery charger for
[5] A. Khaligh and M. D’Antonio, “Global trends [23] Battery system, by S. Götz, R. Bauer, H. Schoef- electric vehicles,” IET Electr. Power Appl., vol.
in high-power on-board chargers for electric fler, and J. Mittnacht. (2019, Feb. 19). U.S. Pat- 12, no. 1, pp. 124–134, 2018. doi: 10.1049/iet-
vehicles,” IEEE Trans. Veh. Technol., vol. 68, ent 10,211,485 B2 [Online]. Available: https:// epa.2017.0319.
no. 4, pp. 3306–3324, Apr. 2019. doi: 10.1109/ patents.google.com/patent/US10211485B2 [39] Fast charging device for an electric vehicle,
TVT.2019.2897050. [24] S. Götz, R. Bauer, H. Schoeffler, and J. by S. Loudot, B. Briane, O. Ploix, and A. Ville-
[6] L. Henry and A. Clark, “Charging the future: Mittnacht, “Battery system with battery con- neuve. (2014, Sept. 30). U.S. Patent 8,847,555B2
Challenges and opportunities for electric vehi- trol,” U.S. Patent Appl. US2016/0318411A1, Nov. [Online]. Available: https://patents.google.com
cle adoption,” Harvard Kennedy School, Cam- 3, 2016. [Online]. Available: https://patents /patent/US8847555
bridge, MA, HKS Working Paper No. RWP18- .google.com/patent/US20160318411A1 [40] Rapid reversible charging device for an elec-
026, Sept. 2018. [25] J. Voelcker, “Porsche’s fast-charge power play: tric vehicle, by B. Briane and S. Loudot. (2014,
[7] J. Boyd, “China and Japan drive a global EV The new, all-electric Taycan will come with a Dec. 23). U.S. Patent 8,917,046B2 [Online].
charging effort: The new standard will be mighty thirst. This charging technology will Available: https://patents.google.com/patent/
backward compatible with select charging sta- slake it,” IEEE Spectr., vol. 56, no. 9, pp. 30–37, US8917046B2
tions,” IEEE Spectr., vol. 56, no. 2, pp. 12–13, Feb. Sept. 2019. doi: 10.1109/MSPEC.2019.8818589. [41] C. Shi, Y. Tang, and A. Khaligh, “A three-phase
2019. doi: 10.1109/MSPEC.2019.8635804. [26] C. Chou and P.-A. Fortin, “Liquid-cooled charg- integrated onboard charger for plug-in electric
[8] P. Weiss, “Charger collaborations power glob- ing connector,” U.S. Patent Appl. US20190 vehicles,” IEEE Trans. Power Electron., vol. 33,
al electric vehicle expansion,” Engineering, 291588A1, International Patent Appl. PCT/ no. 6, pp. 4716–4725, June 2018. doi: 10.1109/
vol. 5, no. 6, pp. 991–992, 2019. doi: 10.1016/j. IB2019/052239, Mar. 22, 2018. [Online]. Avail- TPEL.2017.2727398.
eng.2019.10.010. able: https://patents.google.com/patent/US2019 [42] S. Haghbin, S. Lundmark, M. Alakula, and
[9] A. Burnham et al., “Enabling fast charging – In- 0291588A1 O. Carlson, “An isolated high-power inte-
frastructure and economic considerations,” J. [27] M. Bertoluzzo, G. Buja, and G. Pede, “Design grated charger in electrified-vehicle appli-
Power Sources, vol. 367, pp. 237–249, Nov. 2017. considerations for fast ac battery chargers,” cations,” IEEE Trans. Veh. Technol., vol. 60,
doi: 10.1016/j.jpowsour.2017.06.079. World Electr. Veh. J., vol. 6, no. 1, pp. 147–154, no. 9, pp. 4115–4126, Nov. 2011. doi: 10.1109/
[10] S. Srdic and S. Lukic, “Toward extreme fast 2013. doi: 10.3390/wevj6010147. TVT.2011.2162258.
charging: Challenges and opportunities [28] W. Wu, Y. Liu, Y. He, H. S. Chung, M. Liserre, [43] S. Haghbin, K. Khan, S. Zhao, M. Alakula, S.
in directly connecting to medium-voltage line,” and F. Blaabjerg, “Damping methods for reso- Lundmark, and O. Carlson, “An integrated 20-
IEEE Electrific. Mag., vol. 7, no. 1, pp. 22–31, nances caused by LCL-filter-based current- kW motor drive and isolated battery charger
Mar. 2019. doi: 10.1109/MELE.2018.2889547. controlled grid-tied power inverters: An for plug-in vehicles,” IEEE Trans. Power Elec-
[11] C. Jung, “Power up with 800-V systems: The overview,” IEEE Trans. Ind. Electron., vol. tron., vol. 28, no. 8, pp. 4013–4029, Aug. 2013.
benefits of upgrading voltage power for bat- 64, no. 9, pp. 7402–7413, 2017. doi: 10.1109/ doi: 10.1109/TPEL.2012.2230274.
tery-electric passenger vehicles,” IEEE Elec- TIE.2017.2714143. [44] M. Alaküla and S. Haghbin, “Electrical appa-
trific. Mag., vol. 5, no. 1, pp. 53–58, Mar. 2017. [29] G. Yang, E. Draugedalen, T. Sorsdahl, H. Liu, ratus comprising drive system and electrical
doi: 10.1109/MELE.2016.2644560. and R. Lindseth, “Design of high efficiency machine with reconnectable stator winding,”
[12] A. Meintz et al., “Enabling fast charging vehi- high power density 10.5kW three phase on- WO Patent Appl. PCT/SE2011/050,745, Dec. 22,
cle considerations,” J. Power Sources, vol. 367, board-charger for electric/hybrid vehicles,” in 2011. [Online]. Available: http://www.google.
pp. 216–227, Nov. 2017. doi: 10.1016/j.jpow- Proc. PCIM Europe 2016; Int. Exhib. Conf. Power com/patents/WO2011159241A1?cl=de
sour.2017.07.093. Electron., Intell. Motion, Renew. Energy and En- [45] I. Subotic, N. Bodo, E. Levi, M. Jones, and V.
[13] R. Parrish et al., “Voltec battery design and ergy Manage., 2016, pp. 1–7. Levi, “Isolated chargers for EVs incorporating
manufacturing,” in Proc. SAE 2011 World Congr. [30] D. Cesiel and C. Zhu, “A closer look at the on- six-phase machines,” IEEE Trans. Ind. Electron.,
Exhib., Apr. 2011. doi: 10.4271/2011-01-1360. board charger: The development of the sec- vol. 63, no. 1, pp. 653–664, 2016. doi: 10.1109/
[14] Method and system for thermal management of ond-generation module for the Chevrolet Volt,” TIE.2015.2412516.
a high voltage battery for a vehicle, by A. Kum- IEEE Electrific. Mag., vol. 5, no. 1, pp. 36–42, [46] Battery charger for electric vehicles, by M.
mer, S. Wojtkowicz, B. Gillespey, J. R. Grimes, Mar. 2017. doi: 10.1109/MELE.2016.2644265. Kardolus, J. Schijffelen, M. Gröninger, and V.
K. King, and N. R. Burrows. (2013, Dec. 31). U.S. [31] Bidirectional powering on-board charger, ve- Casteren. (2019, Jan. 1). U.S. Patent 10,166,873
Patent 8,620,506 B2 [Online]. Available: https:// hicle power supply system including the same, B2 [Online]. Available: https://patents.google
patents.google.com/patent/US8620506B2 and control method thereof, by J. H. Kim, J. .com/patent/US10166873B2
[15] T. Sakuraba, R. Ouaida, S. Chen, and T. Chail- Y. Park, J. Lee, K. Choi, and J. J. Lee. (2018, [47] Charging efficiency using variable isolation,
loux, “Evaluation of novel hybrid protection Aug. 14). U.S. Patent 10,046,656B2 [Online]. by J.-P. Krauer. (2015, Dec. 29). U.S. Patent
based on pyroswitch and fuse technologies,” Available: https://patents.google.com/patent/ 9,225,197B2 [Online]. Available: https://
in Proc. Int. Power Electron. Conf. (IPEC-Niigata US10046656B2 patents.google.com/patent/US9225197B2
2018 – ECCE Asia), 2018, pp. 2153–2157. [32] L. Huber, Y. Jang, and M. M. Jovanovic, “Per- [48] S. Götz and V. Reber, “Modular power electron-
[16] H. Rahimi-Eichi, U. Ojha, F. Baronti, and M. formance evaluation of bridgeless PFC boost ics system for charging an electrically operated
Chow, “Battery management system: An over- rectifiers,” IEEE Trans. Power Electron., vol. 23, vehicle,” U.S. Patent Appl. US2018/0162229A1,
view of its application in the smart grid and no. 3, pp. 1381–1390, 2008. June 14, 2018. [Online]. Available: https://
electric vehicles,” IEEE Ind. Electron. Mag., [33] D. Cesiel and C. Zhu, “Next generation “voltec” patents.google.com/patent/US20180162229
vol. 7, no. 2, pp. 4–16, 2013. doi: 10.1109/ charging system,” in Proc. SAE 2016 World [49] K. Hähre, R. Heyne, M. Jankovic, and C.
MIE.2013.2250351. Congr. Exhib., Apr. 2016. doi: 10.4271/2016-01- Metzger, “Power electronic module for a
[17] Method for charging a direct current traction 1229. charging station and corresponding charging
battery at a direct current charging pillar, by D. [34] B. Li, Q. Li, and F. C. Lee, “A novel PCB winding station and electricity charging station,” U.S.
Herke and D. Spesser. (2019, Nov. 12). U.S. Pat- transformer with controllable leakage integration Patent Appl. US2019/0190390A1, Dec. 19, 2018.
ent 10,471,837 B2 [Online]. Available: https:// for a 6.6kW 500kHz high efficiency high density [Online]. Available: https://patents.google.
patents.google.com/patent/US10471837B2 bi-directional on-board charger,” in Proc. IEEE com/patent/US20190190390A1
[18] Inverter for an electric automobile, by S. Appl. Power Electron. Conf. Expo. (APEC), 2017, [50] Galvanic isolation in the power electronics
Götz and T. Lütje. (2019, Dec. 10). U.S. Pat- pp. 2917–2924. doi: 10.1109/APEC.2017.7931111. system in a charging station or electricity
ent 10,505,439 B2 [Online]. Available: https:// [35] J. Lu, K. Bai, A. R. Taylor, G. Liu, A. Brown, P. charging station, by R. Heyne, F. Joslowski,
patents.google.com/patent/US10505439B2 M. Johnson, and M. McAmmond, “A modular- M. Kiefer, T. Speidel, and A. Natour. (2020,
[19] Combined electric device for powering and designed three-phase high-efficiency high- Sept. 1). U.S. Patent 10,759,293B2 [Online].
charging, by L. D. Sousa and B. Bouchez. (2013, power-density EV battery charger using dual/ Available: https://patents.google.com/patent/
Dec. 17). U.S. Patent 8,610,383 B2 [Online]. triple-phase-shift control,” IEEE Trans. Power US10759293B2
Available: https://patents.google.com/patent/ Electron., vol. 33, no. 9, pp. 8091–8100, Sept. [51] J. Brombach, J. Winkler, F. Mayer, A. Beek-
US8610383B2 2018. doi: 10.1109/TPEL.2017.2769661. mann, and C. Strafiel, “Grid-integration of
[20] M. Bruell, P. Brockerhoff, F. Pfeilschifter, H.- [36] H. Bai, M. McAmmond, J. Lu, Q. Tian, H. Teng, high power charging infrastructure,” in Proc.
P. Feustel, and W. Hackmann, “Bidirectional and A. Brown, “Design and optimization of a 1st E-Mobility Power Syst. Integr. Symp., 2017,
charge- and traction-system,” World Electr. 98%-efficiency on-board level-2 battery char- pp. P.1–P.6.

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[52] J. Selle and J. Brombach, “Required technolo- for electric automobiles,” U.S. Patent Appl. electric vehicle battery chargers,” IEEE Trans.
gies for grid integration of charging infrastruc- US2020/0039378A1, July 30, 2019. [Online]. Ind. Appl., vol. 47, no. 4, pp. 1833–1843, 2011.
ture,” in Proc. 2nd E-Mobility Power Syst. Integr. Available: https://patents.google.com/patent/ doi: 10.1109/TIA.2011.2156753.
Symp., 2018, pp. P.1–P.6. US20200039378A1 [57] C. Yao, X. Zhang, Y. Zhang, P. Yang, H. Li, and
[53] A. V. J. S. Praneeth and S. S. Williamson, “A [55] M. M. U. Alam, “Hybrid resonant bridgeless J. Wang, “Semiconductor-based galvanic isola-
review of front end ac-dc topologies in uni- AC-DC power factor correction converter,” tion: Touch current suppression,” IEEE Trans.
versal battery charger for electric transpor- U.S. Patent 9,490,694 B2, Nov. 8, 2016. [Online]. Power Electron., vol. 35, no. 1, pp. 48–58, 2020.
tation,” in Proc. IEEE Transp. Electrif. Conf. Available: https://patents.google.com/patent/ doi: 10.1109/TPEL.2019.2910596.
Expo (ITEC), 2018, pp. 293–298. doi: 10.1109/ US9490694B2/
ITEC.2018.8450186. [56] F. Musavi, W. Eberle, and W. G. Dunford, “A
[54] R. Heyne, F. Joslowski, M. Kiefer, T. Speidel, high-performance single-phase bridgeless 
A. Natour, and M. Bohner, “Charging station interleaved PFC converter for plug-in hybrid

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