Vehicle Power and Propulsion Conference VPPC Coimbra, Portugal, 27-30 October 2014

A Fast On-Board Integrated Battery Charger for

EVs Using an Asymmetrical Six-Phase Machine

I. Subotic, E. Levi, N. Bodo

Liverpool John Moores University
School of Engineering, Technology and Maritime Operations
Liverpool L3 3AF, U.K.
i.subotic@2011.ljmu.ac.uk, e.levi@ljmu.ac.uk, n.bodo@2009.ljmu.ac.uk

AbstractThe paper considers a novel fast charging topology a few configurations capable of fast charging incorporating
for electric vehicles (EVs). Instead of being made as a separate these types of machines have been reported [4-12]. Moreover,
unit, the proposed on-board charger utilizes power electronics most solutions require mechanical locking of the machine’s
components that already exist inside the vehicle, namely an rotor, since a torque gets developed in the machine during the
asymmetrical six-phase propulsion motor and a six-phase charging mode, leading to low efficiency, increased wear and
inverter. The charger can operate at unity power factor, and is
capable of vehicle-to-grid (V2G) operation as well. Additional
noise. Only five of the configurations [8-12] allow three-phase
degrees of freedom of the six-phase machine are employed in (fast) charging without a torque production in the machine.
order to transfer a part of excitation from the torque producing A configuration which in propulsion mode consists of a
to non-torque/flux producing plane of the machine. three-phase machine in an open-winging configuration,
Consequently, electromagnetic torque is not produced in the
supplied from a triple H-bridge inverter, is considered for
machine during the charging/V2G process, so that the rotor does
not have to be mechanically locked. A theoretical analysis of the integration into the charging process in [8]. In the charging
operating principles is reported, and simulation results are given mode grid is connected to the mid-points of the machine’s
for both charging and V2G mode of operation. phase windings. By simultaneous switching of converter legs
connected to the same grid phase, equal spreading of the grid
Keywordsbattery chargers; electric vehicles; integrated on- phase current through each two half-windings in spatial
board chargers; multiphase machines. opposition is achieved. Since these half-windings cancel each
other’s effect, there is no rotating field production in the rotor.
I. INTRODUCTION However, the machine has to be custom made in order to
allow access to the phase windings’ mid-points (in essence,
Nowadays, two types of battery chargers for EVs are used: the machine has to be a symmetrical six-phase machine). The
fast off-board dc chargers and slow on-board ac chargers. configuration has an advantage that it does not require any
Although the former have a great advantage that they can hardware reconfiguration between the charging and propulsion
charge a battery in up to 15 minutes, their drawback is that the mode and it is currently considered for use in future electric
drivers have to search for charging stations that are sparsely vehicles by Valeo [13].
distributed, and plan their route according to their disposition.
On the other hand, on-board chargers provide certain A configuration with the same advantages as the previous
flexibility to charging, since ac mains are widely available. one, but based on utilization of a nine-phase machine with
However, on-board chargers are typically only capable of slow three isolated neutral points, is presented in [9]. In the
charging, since they rely on utilization of the single-phase charging mode three-phase grid is directly connected to the
grid. three isolated neutral points of the machine. By using proper
converter control, it is ensured that the same currents flow
It has to be noted that, during the charging process, the through all three machine’s phases that are connected to the
most of the elements of EVs that have a function in the same grid phase, thus cancelling each other’s effect. There is
propulsion mode, e.g. an inverter and a propulsion motor, are again no field production in the rotor, and no need for any
idle. The idea of reusing some of these elements for the hardware reconfiguration between the operating modes.
charging mode has been introduced more than thirty years ago
[1]. By reusing the existing components, fewer new Renault ZOE is the first commercial vehicle that employs
components are required to be placed on-board, and an integrated fast charger [10]. In addition to the integrated
consequently savings in cost, weight and spare space are elements, which are the inverter and a three-phase propulsion
made. These advantages of integrated chargers have made the motor, the charger requires a junction box. It manages the
topic an interesting area for research. Numerous proposals for charging process, converts the ac current into dc current (thus
integration have been made until now [2], mostly for single- requiring additional power electronics) and communicates
phase (slow) charging. with the charging station. The charging process is without
torque production. However, total converter installed power is
The preferred types of propulsion machines in EVs are increased due to the addition of the charging rectifier.
induction and permanent magnet machines [3]. However, only

The authors would like to acknowledge the Engineering and Physical

Sciences Research Council (EPSRC) for supporting the Vehicle Electrical
Systems Integration (VESI) project (EP/I038543/1).

Pre-print. Final version of this paper appears in IEEE Xplore Digital Library (http://ieeexplore.ieee.org/Xplore/guesthome.jsp).
Vehicle Power and Propulsion Conference VPPC Coimbra, Portugal, 27-30 October 2014

idc iL
grid hardware six-phase
(off-board) reconfig. machine
ic
vag iag iag/2 L, R i a1 v
a1
+
vbg ibg ibg/2 S1 L, R i b1 v b1
+
vcg icg icg/2 S2 L, R i c1 vc1
+ C BAT
iag/2 L, R i a2 v a2 vdc
icg/2 S3 L, R i b2 v b2
ibg/2 S4 L, R ic2 v c2

Fig. 1. Topology of the asymmetrical six-phase integrated fast battery charging system.

Configurations with a symmetrical and an asymmetrical capable of producing an average torque; thus the rotor does
six-phase machine were considered in [11]-[12]. They employ not have to be mechanically locked.
the principle of phase transposition [14] in order to avoid
torque production during the charging mode. However, they Machine’s behaviour in the charging mode can be assessed
require a transformer with dual secondary, which is a non- by examining the 2D space vectors of the asymmetrical six-
integrated element, to realise the six-phase supply. phase system [15]. These can be formulated as (f stands for
any variable that is transformed, e.g. voltage, current, etc.):

 
A novel charger, employing an asymmetrical six-phase
machine, is proposed in this paper. It has a distinct advantage f  2 6 f a1  a 4 f b1  a 8 f c1  a f a2  a 5 f b2  a 9 f c2


2 6f 
over the one introduced in [12] since it does not require a (1)
transformer. Hence it connects to the three-phase supply f  a1  a 8 f b1  a16 f c1  a 5 f a2  a f b2  a 9 f c2
xy
directly and can be entirely integrated on-board the vehicle.
The paper is organised as follows. In section II a where a  exp  j   cos   j sin  and    / 6 . The grid
theoretical analysis of the proposed configuration is currents can be given as
performed. Section III provides a control algorithm for the
i kg  2 I cos( t  l 2  / 3 ) l  0 , 1, 2 k  a ,b ,c (2)
charging/V2G mode. In section IV simulations are performed
for both charging and V2G mode of operation in order to
The relationship between machine and grid phase currents
validate the theoretical results. Section V outlines conclusions
is, according to Fig. 1, given with
of the paper.
i ag i bg i cg
II. OPERATING PRINCIPLES OF THE PROPOSED i a1  i a 2  ; ib 1  i c 2  ; ic 1  i b 2  (3)
CHARGING SYSTEM 2 2 2
The considered topology is shown in Fig. 1. In the By substituting (2) and (3) into (1), the following two
propulsion mode switches S1-S4 are closed, the six-phase space vectors are obtained:
machine has two isolated neutral points, and mains are
disconnected. For the charging mode the topology requires i   3 / 8  I (exp( jt )  exp(  jt )  exp( j / 6 ))
(4)
reconfiguration. The switches have to be opened, leaving the  3 / 2 I cos( t   / 12 )  ( 0.966  j  0.259 )
machine in an open-end winding (OeW) configuration. The
three-phase grid is connected to the machine terminals as i xy  3 / 8  I (exp( jt )  exp( j 5  / 6 )  exp(  jt ))
follows. The connection to the first set of machine windings (5)
follows the phase order of the machine. (i.e. ag-a1, bg-b1 and  3 / 2 I cos( t  5  / 12 )  ( 0.259  j 0.966 )
cg-c1). However, the order of connections to the second set
differs from the phase order of the machine’s windings. Grid Zero-sequence components are both equal to zero.
phases ag, bg and cg are now connected to machine phases a2, It can be seen from (4) that the β-component is 3.73 times
c2 and b2 respectively (Fig. 1). smaller than the α-component. Since these two components
During the charging process, when three-phase currents are proportional they form a straight line if represented in the
flow through the set of three-phase machine windings, the set complex plane. The graphical representation of equation (4) is
develops a rotating field. However, by using the specific order given in Fig. 3. As can be seen, the excitation in the torque
of grid connections to the second set, it is achieved that the producing (α-β) plane is pulsating, since a part of the
second set produces a rotating field that rotates in the opposite excitation is transferred into the non-torque producing (x-y)
direction compared to the one produced by the first set (Fig. plane (5). The excitation that is left in α-β plane is not capable
2). Since the speed and magnitude of these rotating fields are of producing a starting torque in the machine; thus the rotor
the same, the overall resultant field is pulsating, and hence not stays at standstill during the charging process.

Pre-print. Final version of this paper appears in IEEE Xplore Digital Library (http://ieeexplore.ieee.org/Xplore/guesthome.jsp).
Vehicle Power and Propulsion Conference VPPC Coimbra, Portugal, 27-30 October 2014

β voltage controller
Vdc* + idg* coordinate
PI transformation
b1 - iqg*
0 + vd* dq
vdc [v]* [ton]
b2 a2 current *
abc idg controllers + vq PWM
15˚ [ig] abc
15˚ α iqg
a1 dq

coordinate vdc
transformation
∡ θg
c1 [vg] feed-
PLL back
c2 vdg
Fig. 2. Spatial representation of the two winding sets and their rotating fields. [ig]
0.4

0.2 Fig. 5. Grid VOC algorithm for the charging mode of operation.
0


α = 1.183 grid currents into the reference frame that is grid voltage
-0.2
β = 0.317 oriented. In this reference frame current components appear as
-0.4
-1.5 -1 -0.5 0 0.5 1 1.5 dc quantities. However, the components that are in phase and
 out of phase with grid voltage are separated. The d-component
is in phase with the grid voltage and this component can be
Fig. 3. Graphical representation of (4). used for energy transfer. The q-component is out of phase with
idc iL the voltage; thus it should be controlled to zero in order to
3-phase 6-phase achieve unity power factor. Since both components are dc
grid machine quantities, they can be controlled with PI controllers.
ic
vag Laf, Raf iag va The charging process consists of two modes: constant
+ current (CC) and constant voltage (CV) mode. In CC mode the
vbg Lbf, Rbf ibg vb C
+ vdc BAT battery is charged with a constant current, and the reference
vcg Lcf, Rcf icg vc for d-current component is a constant. In CV mode the voltage
+
that is applied to the battery is constant and the reference for
the d-current component is the output of a voltage controller.
The voltage controller is shown in Fig. 5 as the outer control
loop.
Fig. 4. Equivalent scheme of Fig. 1 for the charging/V2G mode of operation.
Current controllers are presented in Fig. 6. As can be seen,
PI controllers control the d- and q-components as in a standard
III. CONTROL ALGORITHM FOR THE CHARGING/V2G voltage source rectifier. However, since the three pairs of R-L
MODE OF OPERATION parameters of Fig. 4 are not mutually equal, they introduce
It was shown in the previous section that the machine will asymmetry into the system. The reason for the asymmetry is
stay at standstill during the charging process. Since the torque that the field in the machine is pulsating during the charging
is not produced, the rest of the system sees the machine as a process. The field from rotor causes different induced voltages
passive network, consisting of a resistance and an inductance in different phases, since they are spatially shifted by different
in each phase. Pairs of phases are controlled in parallel, thus angles from the direction of the pulsating field (e.g. phase a1
the same currents flow through two phases that make a pair by 15˚, b1 by 105˚, c1 by 225˚). Thus the equivalent per-phase
(e.g. a1-a2, see Fig. 1), and each pair can be represented with R-L parameters of Fig. 4 contain unequal portions of rotor
an equivalent resistive-inductive circuit and an inverter leg. leakage inductance and resistance.
Machine phases a1-a2 are represented with Laf, Raf, phases b1-
The asymmetry is reflected through the second harmonic
c2 with Lbf, Rbf, and c1-b2 with Lcf, Rcf. The resulting equivalent
in the d-q reference frame. The harmonic rotates in anti-
scheme for the charging/V2G process is given in Fig. 4, and it
synchronous direction. One way of achieving symmetrical
can be seen that this configuration corresponds to a standard
currents is to transform the second harmonic (as seen from the
three-phase voltage source converter.
d-q reference frame) into a reference frame in which it is seen
In order to comply with grid regulations, near unity power as a dc quantity, and then to control it by a PI controller. The
factor has to be achieved. Hence, the grid voltage oriented reference frame has to rotate two times faster than the
control (VOC) is utilized for controlling the configuration of synchronous speed in the opposite direction. The additional
Fig. 4. The control algorithm is given in Fig. 5. controller that is used for asymmetry control is depicted in the
lower part of Fig. 6.
At first, the grid voltage position has to be determined. In
order to achieve this, grid voltages have to be measured, and The outputs of current controllers are reference voltage
the position determined by phase-locked loop (PLL). Once the signals for the inverter. A simple carrier-based PWM with the
information on grid position is obtained, it is used to transform zero-sequence injection is used as the modulation strategy.

Pre-print. Final version of this paper appears in IEEE Xplore Digital Library (http://ieeexplore.ieee.org/Xplore/guesthome.jsp).
Vehicle Power and Propulsion Conference VPPC Coimbra, Portugal, 27-30 October 2014

idg* 15
-
+ vd’* 10
iag Waveformibg icg
5

(A)
idg

i (A)
+ PI + vq* 5

currents
iqg +

a
0

current
+
coordinate coordinate -5
0

MachineGrid
transformation transformation -10
-15
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.5
j2ωgt -j2ωgt -5
e PI e 0.48 0.482 0.484 0.486 0.488 Time (s) 0.492 0.494 0.496 0.498
0.49 0.5
a) (s)
Time
FFT of waveform (THD=0.03466)
asymmetry control 1

Harmonic rms (p.u.)

Fig. 6. Current controllers. 0.015
0.01
Although V2G is a different mode of operation, the control 0.5 0.005
differs insignificantly from the charging mode. The algorithm 0
of Fig. 5 is still valid. The only difference is that the reference 0 100 200 300 400

for the d- current component is a constant with a negative 0

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
value. The q-component should be again controlled to zero. Harmonic frequency (Hz)
Currents are then in phase opposition with the grid voltages, b)

(A)
and unity power factor is achieved.

(A)
14 10
idg

dg

qg
12

Grid current component i

Grid current component i

For the propulsion mode switches S1-S4 have to be closed, 10
and the machine operates with two isolated neutral points 5
8 iqg
according to the field oriented control (FOC) principles. This
6
mode of operation is well known for asymmetrical six-phase 0
4
machines and will not be considered here.
2
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.5
0.48 0.482 0.484 0.486 0.488 Time
0.49(s) 0.492 0.494 0.496 0.498 0.5
IV. SIMULATION RESULTS Time
Time(s)
(s)
c)
Matlab/Simulink simulation results of the proposed fast Fig. 7. Charging mode: (a) Grid phase currents, (b) spectrum of grid phase
charger are presented in this section, for both charging and current iag, (c) grid current components.
V2G modes of operation. The three-phase grid is taken as
perfectly sinusoidal with phase voltage of 240Vrms and 50Hz effect is amplified by the fact that rotor leakage inductance is
frequency. The switching frequency of the converter is 10kHz, two times higher than the stator’s in this machine.
and the dead-time effect is neglected. The dc-bus capacitance The spectrum of the phase a current is given in Fig. 7b. It
is taken as 1.5mF. Battery is modelled with an ideal voltage contains only small low order harmonics. The third harmonic
source E in series with a resistor RL=0.5Ω, which represents (1.3%) is introduced by a pulsating output of the dc-bus
battery’s internal resistance. Asymmetrical six-phase voltage controller, as will be shown later. Grid current
induction machine parameters, used in the simulation, are the components are shown in Fig. 7c. The q- current component is
following: Rs =12.5 Ω, Rr = 6Ω, Lγs =5.5mH, Lγr = 11mH, Lm = kept at zero, which shows that the charging is with the unity
590mH, three pole pairs, J = 0.1kgm2. The charging mode is power factor. The complete energy transfer is achieved by the
considered first. d-component, which is the grid current component that is in
phase with the grid voltage. The grid phase voltage and
A. Charging Mode machine phase current ia1 are shown in Fig. 8a. It is again
For this mode of operation the reference for the dc-bus obvious that the charging process is with the unity power
voltage is set to 600V, and the ideal voltage source of the factor. The machine’s ia1 current is exactly two times smaller
battery is taken as E = 597V. It should be noted that this value than the grid current iag at all times. Machine current
does not have to be the same for all modes of operation. In components are given in Fig. 9. The first (α-β) plane is
fact it is quite common that EVs have a dc-dc converter excited. However, the α and β components have the same
between the battery and the dc-bus capacitor, so that various phase, thus producing a pulsating field in the machine. Since a
values can be achieved. In the next subsection a different pulsating field cannot provide an average torque to start the
value is considered for E. machine, it stays at standstill. Current components in the non-
torque producing plane are shown in Fig. 9b. The excitations
Fig. 7a illustrates the grid currents. Although the in both planes are in accordance with theoretical results given
machine’s equivalent R-L parameters in Fig. 4 are different for with (4) and (5).
each grid phase, the currents are symmetrical due to the added
asymmetry control (the lower part of Fig. 6). However, it can Converter phase voltage and spectrum are given in Fig. 10.
be seen that the phase a has the smallest current ripple among Since the dead-time effect is neglected, the spectrum contains
the three phases. The rotor winding’s influence is the most only very small low-order harmonics. The machine’s torque
prominent in this phase since it is spatially shifted by the and speed during the charging process are shown in Fig. 11a.
smallest angle (±15˚) form the rotor’s pulsating field. The It is obvious that zero torque results during the whole charging

Pre-print. Final version of this paper appears in IEEE Xplore Digital Library (http://ieeexplore.ieee.org/Xplore/guesthome.jsp).
Vehicle Power and Propulsion Conference VPPC Coimbra, Portugal, 27-30 October 2014
10
400 vag 0.01 3
Grid voltage v (V)

(A)
5 Torque 2

Torque (Nm)
200
ag

Speed (rpm)
1
Waveform

a
ia

Grid current i
5 1
Machine current i (A)

0 0 1
-0.01
a

Speed
-200 0
-5
0
-0.02
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5-1
-400 0 0.05 0.1 0.15 0.2 Time
0.25(s) 0.3 0.35 0.4 0.45 0.5
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.5-10
0.48 0.482 0.484 0.486 0.488 Time
0.49(s) 0.492 0.494 0.496 0.498 0.5 Time(s)
Time (s)
-5 Time0.49
(s) 0.492 0.494 0.496 0.498 a)
0.48 0.482 0.484 0.486 0.488 0.5
a) (s)
Time 601 14

(A)
vdc

(V)
FFT of waveform (THD=0.03466)

L
12

Battery charging current i

dc
1 600

Dc bus voltage v
Harmonic rms (p.u.)

0.015 10

0.01 599
8
iL
0.5 0.005 598 6
0 4
0 100 200 300 400
597
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.52
0
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0.48 0.482 0.484 0.486 0.488 Time
0.49(s) 0.492 0.494 0.496 0.498 0.5
Harmonic frequency (Hz) Time (s)
b) b)
Fig. 8. (a) Grid phase voltage and machine phase current ia1 , (b) spectrum of Fig. 11. (a) Machine’s torque and speed, (b) dc-bus voltage and battery
machine phase current ia1. charging current.
(A)

(A)

10
i process, and the speed is consequently kept at zero.


10
Machine current component i


Machine current component i

5
5 i The dc-bus voltage and battery charging current are shown
in Fig. 11b. The average value of the dc-bus voltage follows
0 0
the reference without any steady-state error. However, a slight
-5 -5
pulsation around the reference is evident. The pulsation is
caused by time-dependant losses in the machine. The machine
-10
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.5-10 equivalent scheme has different parameters in different phases
0.48 0.482 0.484 0.486 0.488 Time
0.49(s) 0.492 0.494 0.496 0.498 0.5
Time
Time(s)
(s)
and, since symmetrical currents flow through these phases, the
a) complete losses are the greatest when the current in the phase
with the highest impedance (phase a) is at its peak.
(A)

(A)

iy 10
Considering the fixed power drawn from the grid, the useful
x

10
Machine current component i

y
Machine current component i

5 5 energy after the losses is also slightly pulsating. The battery

ix charging current follows the shape of the voltage and has an
0 0 average value of 6A.
-5
-5
Since the dc-bus voltage is pulsating, the voltage controller
tries to compensate this and gives a slightly pulsating
-10
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.5-10 reference for the d- current component. This manifests itself
0.48 0.482 0.484 0.486 0.488 Time
0.49(s) 0.492 0.494 0.496 0.498 0.5
with a small third harmonic in the current spectrum (Fig. 7b).
Time (s)
b) It should be noted that this harmonic is different in different
Fig. 9. Machine’s current components: (a) iα and iβ, (b) ix and iy. grid phases, with the sum being always equal to zero.
Waveform
Converter phase voltage (V)

500
B. V2G Mode
V2G mode of operation is examined in this subsection. A
0
different value for the ideal voltage source of the battery,
E = 753V, is now considered, as explained in the previous
subsection. The reference for the dc-bus voltage is set to
-500
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.5 750V.
Time (s)
x 10
-3 FFT of waveform (THD=0.8219) Grid currents, phase a current spectrum, and current
1 8 components are given in Fig. 12. The same conclusions as for
Harmonic rms (p.u.)

6 the charging mode are valid. However, it can be seen that the
4
0.5
d-component now has a negative value, which demonstrates
2
that the grid current is in phase opposition with the grid
0
0 100 200 300 400 voltage. The absolute value for this current component is
0 smaller than during the charging mode (Fig. 7c) since the
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Harmonic frequency (Hz)
power that is injected into the grid is now what is left from the
Fig. 10. Converter phase voltage and spectrum. battery discharging power after the filter (i.e. machine) losses.

Pre-print. Final version of this paper appears in IEEE Xplore Digital Library (http://ieeexplore.ieee.org/Xplore/guesthome.jsp).
Vehicle Power and Propulsion Conference VPPC Coimbra, Portugal, 27-30 October 2014

15 V. CONCLUSION
Waveform
10 A novel fast charger for EVs is proposed in the paper. The
(A)

5
i (A)

5
charging is from a standard three-phase grid, and the charger
currents
a

0 is completely integrated on-board. Asymmetrical six-phase

current

-5
0 machine with two isolated neutral points and a six-phase
MachineGrid

-10 iag ibg icg

inverter are incorporated into the charging process, avoiding
-15 the cost of additional power electronics components.
0.48 0.482 0.484 0.486 0.488 0.49 0.492 0.494 0.496 0.498 0.5
-5
0.48 0.482 0.484 0.486 0.488 Time (s) 0.492 0.494 0.496 0.498
0.49 0.5 Simulations with a full asymmetrical six-phase machine model
a) (s)
Time are performed for both charging and V2G modes of operation
-3 FFT of waveform (THD=0.05238)
8
x 10 in order to validate the theoretical results and ascertain the
1
torque-free operation.
Harmonic rms (p.u.)

6
4
0.5 2 REFERENCES
0
0 100 200 300 400
[1] J.M. Slicker, “Pulse width modulation inverter with battery charger,” US
Patent 4,491,768, 1985.
0
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 [2] S. Haghbin, S. Lundmark, M. Alakula, and O. Carlson, “Grid-connected
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b) solution,” IEEE Trans. on Industrial Electronics, vol. 60, no. 2, pp. 459-
473, 2013.
(A)

0 4

(A)
iqg
[3] J. de Santiago, H. Bernhoff, B. Ekergård, S. Eriksson, S. Ferhatovic, R.
dg

qg
-2 2
Waters, and M. Leijon, “Electrical motor drivelines in commercial all-
Grid current component i

Grid current component i

-4 0 electric vehicles: A review,” IEEE Trans. on Vehicular Technology, vol.
-6 -2 61, no. 2, pp. 475-484, 2012.
idg
-8
-4 [4] S. Kinoshita, “Electric system of electric vehicle,” US Patent No.
-6 5,629,603, 1997.
-10
-8 [5] F. Lacressonniere and B. Cassoret, “Converter used as a battery charger
-12
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Pre-print. Final version of this paper appears in IEEE Xplore Digital Library (http://ieeexplore.ieee.org/Xplore/guesthome.jsp).