Decentralized Control Using Wireless Signal
Communication for Multi-Port EV Charger
with Multiple Cells
Keita Ohata1, Hiroki Watanabe2, Jun-ichi Itoh1, Keisuke Kusaka2
1 Department of Science of Technology Innovation, Nagaoka University of Technology, Nagaoka, Japan
2 Department of Electrical, Electronics, and Information Engineering, Nagaoka University of Technology, Nagaoka, Japan*E-mail: keita_ohata@stn.nagaokaut.ac.jp, hwatanabe@vos.nagaokaut.ac.jp,
itoh@vos.nagaokaut.ac.jp, kusaka@vos.nagaokaut.ac.jp
Abstract— This paper proposes a decentralized control
scheme of a multi-cell AC/DC converter for electric vehicle(EV) charger applications. The multi-cell topology effectively
achieves high scalability by connecting cells in series andparallel. Generally, the multi-cell topology requires a lot ofsignal lines between the master control and slave controllers
in order to control the power-sharing between the cellconverters. Thus, the maintainability of the power converters
is restricted with these wires. The proposed control schemewith a wireless communication for the EV charger requires
no signal wires between master and slave controllers. The
features of the proposed decentralized scheme are; 1)it allows
communication delay of several hundred milliseconds, 2)each
unit, which consists of three single-phase AC/DC converters,
has an independent the slave controller. The proposed
method is verified by with six units. The power-sharing isdemonstrated by the the 7.2-kW prototype. The imbalance
rate of the input current is suppressed by 7% or less.
Keywords— battery charger, decentralized
wireless signal communication, multi-port converterI.

control,

INTRODUCTION

Electric Vehicle (EV) chargers have been important interms of the growth of EV markets [1]. The EV chargers
consist of an isolated AC/DC converter, which has thecapability of the Power Factor Correction (PFC) and the
DC-DC converter fot the output control. An LLC
converter and a Dual Active Bridge (DAB) converter havebeen commonly employed for the isolated DC/DC
converters because of their high conversion efficiency by
the soft-switching operation [2]-[7]. Recently, the power
capacity of the EV batteries and EV chargers has
drastically increased in order to extend the cruising
distance of EVs. Furthermore, the use scene of EVs andsmart micro-grids based on renewable energy sources withenergy storage systems are expanding. Thus, the EV
charger must widely accept the battery capacity and utilize
the energy effectively such as a multi-port converter [8]-[9].
The high-power converter for the EV charger requiresa large voltage and current rating for each component of
the main circuit. A multi-cell power converter is suitable
for the high power converter application because thecircuit configuration is flexibly designed for many system
ratings by changing the connection of the cell converters.
Especially, the Input-Parallel-Output-Parallel(IPOP)
configuration is the typical solution to increase the systemcurrent rating for the high-power converters [10]-[12].
However, the multi-cell converter requires many wirings
to connect each cell converter. Especially, a lot of signal
wiring is necessary in order to control many cell converters
by the centralized control. These wiring decreases thesystem reliability, flexibly and it may become a cause ofcomplicated systems.
The decentralized control for the multi-cell converters
has been considered in order to solve those problems [13].
Reference [13] indicates one of the methods, which lowcost communication between the master controller andslave controllers. The system integrates the 5 Mbps opticalfiber as the communication line. Thus, It is easy to
implement decentralized control. Note that thisdecentralized control employs the master-slave control inorder to regulate all slave controllers which is placed ineach cell converter. Hence, the wiring between the master
controller and the slave controller is still necessary.
The using wireless communication is suitable to reduce
the singnal line between master and slave controller. The
delay time caused by a wireless communication is several
milliseconds to several hundred milliseconds due toqueuing and collision avoidance processes if a generalpurpose wireless communication module such as Zigbee
or Bluetooth is implemented in power converters. Thus, it
is not possible to introduce a low-speed control using
wireless communication at the inner loop of the voltage orcurrent control into the power converter due to thecommunication delay of wireless communication.
This paper proposes a decentralized control with thewireless communication, which is suitable for a multi-port
EV charger. The originality of this paper is thedecentralized control that includes a delay time caused by
the wireless communication with the several thousand
times larger than the control period. These controls areplaced in the outer loop of the fast feedback control, whichis each input current control. Therefore, the control allows

a delay of several seconds caused by wirelesscommunication. The validity of the proposed method isdemonstrated with a 7.2-kW prototype. Fromexperimented results, the input current imbalance rate issuppressed by 7 % or less.

Rapidcharging
Batt. Batt.

Proposedbattery charger
Unit #1

Cell U

Cell V
Cell W
Slave controller
Unit #2

3f 200 V

Batt.

Cell U

Cell V
Cell W
Slave controller
Unit #NBatt.

Cell V
Cell W

Multiplecharging

Slave controller

Master：Wirelesscontroller
communication
Cell @1.2 kW
PFC converter Resonant DC-DC converter
fsw = 85 kHz
fsw = 45 kHz
i
cell

L

+

Cs Ls

Cout +

Cdc

Vout

Lm

Fig. 1. Multi-port charger system for electric vehicle withmultiple cells.
TABLE I
Experimental Conditions.
Quantity

Symbolvalue

Input voltage

Vin

200 Vrms

Rated output powerP

7.2 kW

DC-link capacitanceCconv( H = 35 ms )Output capacitanceCout( H = 35 ms )Input inductanceL(%Z = 2.8%)

Switching frequency (PFC)

fsw(PFC)

45 kHzSwitching frequency (Res. DC-DC)

fsw(DC -DC)

85 kHzAngular frequency of PI controller
for input current
Angular frequency of PI controller
for output voltage

wACR

10000 rad/s

wAVR

50 rad/s

1080 mF

1080 mF
3 mH

H: Unit capacitance consta nt of output ca pac itancebase d on conve rter capacity

SYSTEM CONFIGURATION AND CIRCUIT TOPOLOGY

Figure 1 shows the system configuration and cell
controller. The cell consists of a boost converter to operate
PFC and a resonant DC-DC converter. Each phase isconnected to three cells in parallel. The resonant DC-DC
converter achieves the soft switching with the series
resonance between the leakage inductance Ls in the highfrequency transformer and the resonant capacitor Cs
connected to the primary side of the transformer. Note thatthe switching frequency of the DC-DC converter is set to
85 kHz to switch MOS-FETs according to the resonauce
frequency. Then, the DC-DC converter roles a DCtransformer with a constant boost ratio achieving galvanic
isolation. The switch on the output side roles the switching
between Mode I: Rapid charging and Mode II Multiple
charging.
Table I lists the experimental conditions. This paper
discusses a case of two units (N=2) and the rated power ofthe cell is designed 1.2 kW. Thus, the rated power of thesystem is 7.2 kW in this paper.
III.

Cell Uvin

II.

PROPOSED DECENTRALIZED CONTROL SCHEME

Figure 2 (a) shows the control layer diagram of the
proposed decentralized control scheme. The master
controller manages the system output by communicatingwith N slave controllers. The master controller transmits
the output voltage reference Vout* to slave controllers.
Moreover, the averaged input current reference Iin_avg* istransmitted in mode II: rapid charging. Whereas, the slave
controllers transmit the input current reference of cell Iin_x*
to the master controller.
Figure 2 (b) shows the block diagram of the proposed
decentralized control. Each input current (Iin_x) is
controlled by the PI controller to follow the input current
reference obtained by the multiplying of the amplitude
which is decided by the output voltage controller, and thephase angle that is synchronized with the input voltage.
The output voltage is controlled by the PI controller, whichis placed on the outer loop of the input current control.
A. Mode I: Multiple charging
The control of mode I: the multiple charging is
implemented in a double-loop configuration of the generalvoltage and current control. In this mode, each slave
controller independently controls the input current and theoutput voltage based on the output voltage reference fromthe master controller. Then, the output port of each unit isindependent of other units. Thus, there is no interferencein the output voltage control, and no additional control isrequired.
B. Mode II: Rapid charging
The output port of the system at mode II is connected inparallel in order to increase the rated capacity of charging
to one battery. The slave controllers individually control
each output voltage of the cell, thus the control
interference between each output voltage controller iscaused by the detection error of the output voltage due tothe thermal drift characteristics of the detection circuit, andso on. In order to suppress the interference and an

Master
controller

Iload
*

IcellN*

Vout ,I0Comm
moduleComm module:
MH920-Mod(Oki Electric Industry)

Iout1

Vout1

Iout2

Vout2

Comm module

Slave Controller

Slave Controller

U1-cellV1-cell
Converter Converter

W 1-cellConverter

Rload

Rd :Virtual re sistance

Unit #N

Comm module

Vout

VoutN

Wireless communication

Unit #1

IoutN

(a)

without output voltage control.
Iload

Rd

UN - cell
VN - cell W N - cell
Converter Converter Converter

Iout1

Vout1

Rd

Rd
Iout2

Vout2

IoutN

Vout

Rload

VoutN
RK :Virtual re sistance(b) with output voltage control.
Fig.3 Equivalent circuit of DC side at mode II: rapid charging.

OutputIunit 1*
Iunit 2*Control layer.

Iunit N*

Iavg*

1
N

+

Vout*

Iunit N*

Iavg*

Vout*

+

Mode 2: Rapid charging++++ Vba la+nce
Vdroop
VdroopPI
Iavg*+
Iunit*Vout*
B. Inputcurrent control

A. Output
voltage control

Mode 1: Multiple charging

PI

×

Vout

+

|sinqu v|

×Vo ut (c omp )*

ZK
Vin
Vout*
Iunit*

D. Balance control
for input current
C. Droop control
for output voltage

Thus, the control suppresses the interference between each
output voltage control.

Master controller

Iunit1*

PI
iLu1

×

+

|sinqwu|
ABS ABS ABS
sin

sin

PI

|sinqvw| iLv1

PI
iLw1

PWM signals

(a)

sin

PLL PLL PLL

vuv

vvw vwu
Slave controller #1#2#N(b) Block diagram.
Fig.2 Proposed decentralized control scheme.

imbalance of the power-sharing between each unit, theoutput voltage droop control (Section B-1) and the input
current balance control (Section B-2) are adopted.
B-1. Output voltage droop control
Figure 3 (a) shows the equivalent circuit of the DC sideat mode II. The output of cells is connected in parallel. The
output voltage of each cell is controlled by each slave
controller. The output voltage is equivalent to a constantvoltage source controlled by a feedback controller. Then,the output voltage controller is interference with themismatched detected output voltage, which is caused by
the gain error of the detection or thermal drift of detectors.
In order to adapt to this problem, the output voltage droop
control is adopted as the non-interference control between
the parallel-connected converters.
Figure 3(b) shows the equivalent circuit of the DC side,which is adapted to output voltage droop control. The
droop control acts as the series-connected resistance toconstant voltage source controlled by each slave controller.

B-2. Input current balance control
The role of the input current balance control is theprevention of the current deviation between the input
current of unit converters. For example, the detected
output voltage of unit #1 has positive error, the output
voltage of unit #1 is controlled to lower voltage thananother unit. Thus, the input current of unit #1 is controlled
to small than another unit. It indicates the imbalance ofpower sharing between unit.
The control compensates the output voltage reference
using a PI controller based on the difference which is the
input current reference Iin_x and the averaged input current
reference Iin_avg.
B-3. Wireless signal communication between master andslave controllers
The master controller transmits the output voltage
reference Vout* and the averaged input current reference
Iin_avg* to slave controllers. Moreover, the master controller
receives the input current reference Iin_x* from the slave
controllers at mode II. The averaged input current
reference Iin_avg* is given by
I in _ avg * =1 N
 ( Iin _ x* )N x =1(1)

The slave controller corrects the output voltage
reference based on the above wireless communication by
the output voltage droop control. the input current balance
control in order to achieve the power-sharing and noninterference.
IV. CHARACTERISTIC OF PROPOSED DECENTRALIZEDCONTROL SCHEME
A. Communication period between master and slave
controller Tcomm
The minimum communication period between themaster and slave controller Tcomm(min) is limited by thecommunication delay time of the communication module.
Moreover, the maximum communication period Tcomm(max)is limited by the allowable settling time to compensate theimbalance of the input current. The settling time becomes
longer as the communication delay time increases. Wellknown the wireless communication (e.g., Zigbee,
Bluetooth) has from several milliseconds to several
hundred of milliseconds delay as a communication delay
due to queuing processing, and so on. Thus, the settling
time may reach up from several hundred milliseconds toseveral seconds when these wireless module is employed.
However, the long settling time of the input current is nota significant problem from the point of view of a rapid
charger for EVs because of the relatively stable load.
B. Virtual droop resistance RdThis chapter discusses the effect of increasing or
decreasing the virtual droop resistance on the preventionof the control interference between the output voltage
controllers. The non-interference is easily achieved whenthe virtual droop resistance Rd which is in series with eachvoltage source increases, whereas the error between the
output voltage and the output voltage reference increases.
Thus, the droop resistance should be as small as possible.
The condition for the prevention of the interference ineach voltage control system is given by
Vout _ x*  Vout(2)
where Vout_x*is output voltage reference of each slave
controller, x is unit number (x = 1 ~ N), Vout is output
voltage. That is when the output voltage reference value
Vout_x* of each cell unit exceeds the output voltage Vout, noninterference of the output voltage control system isachieved.
In this paper, an acceptable output voltage error of up to ±5% is specified, and the droop resistance Rd is set to 5% ofrated impedance to satisfy this specification.
The input current balance control is placed on the outerof the PI controller of the output voltage. Hence, thebandwidth of the input current balance control is designedwith slower than the output voltage PI controller. Thebalance control uses the averaged input current reference
Iin-avg* obtained by low-speed wireless communication, it
is necessary to design the system with the communication
cycle Tcomm in mind. Thus, by the integral time constant Ti
is set to 1.5 second and the proportional gain Kp is set to
1.0 using the ultimate sensitivity method.

V.

EXPERIMENTAL RESULTS

Table II lists the specification of the wirelesscommunication module. A wireless communication
module MH920 (Oki Electric Industry) is employed. The
data length of the output voltage reference and theaveraged input current reference is set to 2 bytes. Note thatthe header and footer packets are added to thecommunication data according to the protocol of thewireless communication module. Figure 4 (a) shows thecell converters. The charger system consists of six cells.
Figure 4 (b) shows the master/slave controller and wirelessmodule.
The
MCU(Microcontroller
Unit)
is
TMS320F28379D (Texas Instruments). The MCU
communicates the wireless module using UART
(Universal Asynchronous Receiver/Transmitter) with
115,200 bps. In this case, due to the constraints of thecontrol program and wireless module, The communication
period is set to 1.0 sec to prevent hang-up due tocommunication congestion.
A. Communication delay caused by wireless module
Figure 5 shows the communication waveform between
master and slave. The master controller transmits output
voltage reference and input current reference to slave
controllers #1 through #N in sequence. Each output
voltage command value is transmitted with a timedifference of milliseconds and updated every seconds.
Systems that include Zig-bee, Bluetooth, and othergeneral-purpose wireless communications generally havecommunication delays of several tens of milliseconds or
TABLE IISPECIFICATION OF WIRELESS COMMUNICATION MODULE

Manufacture

Oki Electric Industry

Frequency band

920 MHz

Product nameCoordinator: MH920-Mod<1><0S>
Router:MH920-Mod<1><0W>

Module size

23.9 mm × 40.9 mm × 5 mm

Maximum numberof connection

100

MH920
(Oki Electric Industry)
TMDSCNCD28379D(Texas Ins truments )(a) Cell converter.

(b) Master/slave controller and wireless module.
Fig. 4 Photograph of electric vehicle charger system.

5 s/div
Fig. 5 (b) Fig. 5 (c)(a)

Outline.

Required time for wirelesscommunication: 139.7 ms

20 ms/div(b) Extended Fig. 5(a): Transmission of the data in the master controller to the slave controller #2.

Required time for wirelesscommunication: 181.3 ms

20 ms/div(c) Extended Fig. 5(a): Reception of the data in the slave controller #1 to the master controller.
Fig. 5 Waveform of wireless communication in the proposed method.
Response:
Data transmit/ received

Reques t

Tx Data read/write

30

MasterResponse:
Dat a transmit/ received

Tx
Slave
Reques t
Dat a read/write

Time

Communication delay
Fig.6 Procedure of wireless communication. the communication delaycaused by wireless communication is defined as shown the figure.

more due to queuing processing, congestion processing,
etc. Moreover, the communication delay is variable asshown in Fig.5(b), (c), and Fig.7.
Figures 5(b) shows a measured communication delay
time according to the definition in Fig. 6, when thetransmission of the data in the master controller MCU tothe slave controller #2 MCU is processing. The data

Probability [%]Rx

Rx

Number of measurements : 50 times

25
20
15
10
5

0

Communication delay [ms]Fig.7 Distribution of wireless communication delay in the communicating
sequence, which is reception of the data in slave controllers to the master
controller.

trasnmit command arrives at the Rx (receive) of Slave #2
MCU after 10 milliseconds which the signal is output fromthe Tx (transmit) of the master MCU. The requested data
is sent back to the master controller in about 60
milliseconds. Thus, the sequence of the transmission of
the data in the master controller to slave is required at139.7 milliseconds in this case.
Figure 5(c) shows a measured communication delay
time according, when the reception of the data in the slave
controller #1 to the master controller is processing. The
data trasnmit command arrives at the Rx (receive) of
Slave #2 MCU after 10 milliseconds which the signal is
output from the Tx (transmit) of the master MCU. The
requested data is sent back to the master controller inabout 70 milliseconds. Thus, the sequence of the data
request command from slave to master takes 181.3
milliseconds.
Figure 7 shows the histogram of the delay time caused
by wireless communication obrained by 50
measurements in the experimental condition. The mode
value of the histogram is from 125 milliseconds to 130
milliseconds and 135 milliseconds to 140 milliseconds.
Moreover, the minimum/maximum of the delay is
122/181 milliseconds under the experimental conditions.
Note that, this histogram is only example, as it varies
depending on the wireless communication standard, thecongestion of the transmission line, the kind of wirelessmodule. Thus, a design of the controller for power
converters using wireless communication must be keep
in mind that the variation in communication delay time islarge.
B. Mode I: Multiple charging
Figure 8 shows the input current and output voltage
waveforms at a steady state. At this time, the two chargers
are controlled to output voltage independently, and themaster controller transmits only output voltage reference
350 V. The output voltage follows the reference value of
350V. The output power is uniformly supplied from eachcell according to the load to each unit.
C. Mode II: Rapid charging
Figure 9 shows the input current and output voltage
waveforms at 4.3 kW (0.6p.u.). The detected output
voltage of cell #1 adds + 2% detected error. In contrast tomode I, mode II adds the output voltage droop control
because the output ends are connected in parallel. In
addition, input current balance control is added to prevent
power imbalance between units due to output voltage
detection errors. The input current amplitude of units #1
equals with #2, despite the error in the detected voltage
of unit #1. The imbalance rate of the input current iin isdefined by (3).

iu1, iv1, iw1 : 10 A/div
0
iu2, iv2, iw2 : 10 A/div0
Vout1, Vout2 : 200 V/div0(x = 1 ~ N )(3)where Icell_x is each input current, Iin-avg is averaged input
current. The imbalance ratio is 7% and the current
deviation between cells was kept below 1 A, and each input
current of cell is balanced.

4 ms/div

Fig. 8 Input current and output voltage at steady state in mode I: multiple
charging.

Vout * = 350 V, 4.3 kW (0.6 p.u.) output

iu1, iv1, iw1 : 10 A/div

0

iu2, iv2, iw2 : 10 A/div
0

Vout : 200 V/div
iu1 = 0.55 A , iv1= 0.70 A , iw1 = 0.66 A
iu2 = 7.3 A, iv2= 7.6 A, iw2 = 7.3 A

0iin = 89 %4 ms/div
Without input current balance and without output voltage droop
control.

(a)Vout * = 350 V, 4.3 kW (0.6 p.u.) output

iu1, iv1, iw1 : 10 A/div

0
iu2, iv2, iw2 : 10 A/div
0

Vout : 200 V/div
iu1 = 3.1 A, iv1= 3.4 A, iw1 = 3.4 A
iu2 = 5.8 A, iv2= 5.9 A, iw2 = 5.7 A

0(b)iin = 32 %4 ms/div
Without input current balance and with output voltage droop control.

Vout * = 350 V, 4.3 kW (0.6 p.u.) output

iu1, iv1, iw1 : 10 A/div

0
iu2, iv2, iw2 : 10 A/div
0

Vout : 200 V/div
0
(c)

*
 I

−I
 iin [%] = max  cell _ x in*−avg  100
I in−avg

Vo ut 1** = 300 V, Pout 1 = 3.6 kW
Vo ut 2 = 400 V, Pout 2 = 1.8 kW

iu1 = 3.7 A, iv1= 4.0 A, iw1 = 3.9 A
iu2 = 4.0 A, iv2= 4.2 A, iw2 = 4.0 A

iin = 6.7 %4 ms/div
With input current balance and with output voltage droop control.
Fig. 9 Input current and output voltage at steady state in mode II. The
detected output voltage of cell #1 adds +2 % detected error.

Figure 9 (a) shows the input current and the output
voltage without proposed input current balance control andwithout output voltage droop control. The input currents iu1,
iv1, and iw1 of unit #1 are almost zero, and the imbalance of
the input current occurs.

iu1, iv1, iw1 : 10 A/div

0

iu1, iv1, iw1 : 10 A/div

0
iu2, iv2, iw2 : 10 A/div

0

iu2, iv2, iw2 : 10 A/div
0

Vout = 358 V
0Vout : 200 V/div

4 ms/div(a)

Vout : 200 V/div

Vout = 349 V

0

4 ms/div

0.333  (p.u.)

(b) 0.83  (p.u.)

iu1, iv1, iw1 : 10 A/div

iu1, iv1, iw1 : 10 A/div

00iu2, iv2, iw2 : 10 A/div

iu2, iv2, iw2 : 10 A/div
0

0

0

Vout = 332 V

Vout : 200 V/div
4 ms/div

Vout : 200 V/div

Vout = 304 V0

4 ms/div(c) 1.67  (p.u.)

(c) 3.33  (p.u.)

Fig.10 Input current and output voltage when droop resistance is changed from 0.01p.u. to 0.1p.u. Vout* = 350 V.

Figure 9 (b) shows the input current and the output
voltage without proposed input current balance control andwith output voltage droop control. The input currents areaveraged by the droop control, the input currents iu1, iv1,
and iw1 of unit #1 are controlled smaller than the input
currents of unit #2 iu2, iv2, and iw2 due to the positive error
in the output voltage detection value of unit #1. Thus the
input current is imbalanced. The control results in adecrease from iin = 89 % to iin = 32 %.
Figure 9 (c) shows the the input current and the output
voltage waveform with proposed input current balance
control and output voltage droop control. The imbalance of
input current caused by output voltage error iscompensated by input current balance control. The control
results in a decrease from iin = 32 % to iin = 6.7 %.
D. Characteristics of proposed decentralized control.
Figure 10 shows the input current and output voltage
waveform when droop resistance Rd is changed from
0.01p.u. to 0.1p.u. The output voltage reference is set to350 V. the output voltage error increases with the increaseof the droop resistance increases. The minimum droop
resistance is determined by the allowable output voltage
error. Thus, the design of tolerance for the error of detected
output voltage is better which is lower.
Figure 11 and Figure 12 shows the input current andoutput voltage waveform when Tcomm is changed. In Fig.11,
Tcomm is set to 5 seconds, and in Fig.12, Tcomm is set to 10
seconds. The output voltage reference is set to 350 V. The
transient response is not related when the communication
delay time is varied because input current balance control,
which uses wireless communication parameters, is used
only in order to compensate for the imbalance of input
current caused by output voltage errors, whereas thetransient load variations are controlled only by the output
voltage droop control, which does not use wirelesscommunication. Thus, the balanced state is continued
which has an output voltage detection error.
VI.

CONCLU SION

This paper proposed the decentralized control scheme,
which is included low-speed communication from 100
milliseconds to one seconds using wirelesscommunication. The proposed scheme is characterized by
the output voltage droop control and the input current
balance control, which adapt wireless signal
communication. The proposed scheme requires no signallines between the master controller and slave controllers.
These characterized controls are placed in the outer loopof the fast feedback control of input current and voltage
controller. Therefore, the control allows several hundredof milliseconds delay of wireless communication.
Moreover, the signal communication The proposed
scheme is verified by experiments with the 7.2-kW
prototype. From experimental results, the imbalance rateof input current iin is suppressed by 7 % or less with low
communication period.
In the future work, the response evaluation bycommunication delay time and design method of droop
gain is going to be studied in more detail.
REFERENCES
[1]
[2]

[3]

International Energy Agency, “Global EV Outlook 2021”, 2021
Y. Yan, H. Bai, C. Yang and W. Wang, "Securing Full-load-range
Zero Voltage Switching for A Dual Active Bridge Based Electric
Vehicle Charger," 2020 IEEE Applied Power Electronics
Conference and Exposition (APEC), pp. 2067-2072, 2020.
Yuki Kinoshita, Hitoshi Haga, “Wide-Range Voltage Gain andHigh-Efficiency of Isolated LLC Converter using Six-Switch andbiu1, iv1, iw1 : 10 A/div000iu2, iv2, iw2:10 A/div

iu2, iv2, iw2:10 A/div

iu2, iv2, iw2:10 A/div

0

0

0

d iu1, iv1, iw1:10 A/div

iu1, iv1, iw1:10 A/div

00iu2, iv2, iw2 : 10 A/divciu1, iv1, iw1:10 A/div

Vout : 200 V/div

Vout 200 V/div
0

250 ms/div
Fig.11 (b)Fig.11 (c)(a) Outline.

0

Fig.11 (d)5 ms/div

Vout 200 V/div

Vout 200 V/div0(b) 3.6 kW (0.50p.u.).

5 ms/div0(c) Transient.

5 ms/div(d) 7.2 kW (1.0p.u.).

*

Fig.11 Input current and output voltage when load is changed from 3.6 kW (0.50p.u.) to 7.2 kW (1.0p.u.). Vout = 350 V, Tcomm = 5 sec.

b

iu1, iv1, iw1 : 10 A/div
0

0

0

0

0

iu2, iv2, iw2 : 10 A/div

iu2, iv2, iw2:10 A/div

iu2, iv2, iw2:10 A/div

iu2, iv2, iw2:10 A/div0

d iu1, iv1, iw1:10 A/div

c i i i :10 A/div
u1, v1, w1

iu1, iv1, iw1:10 A/div

0

0

Vout : 200 V/div
Vout 200 V/div

0

250 ms/div
Fig.12 (b)Fig.12 (c)0

5 ms/div

Vout 200 V/div

Vout 200 V/div0

5 ms/div0

5 ms/div

Fig.12 (d)(b) 3.6 kW (0.50p.u.).

(c) Transient.

(d) 7.2 kW (1.0p.u.).

*

Fig.12 Input current and output voltage when load is changed from 3.6 kW (0.50p.u.) to 7.2 kW (1.0p.u.). Vout = 350 V, Tcomm = 10 sec.

[4]

[5]

[6]

[7]

[8]

Two Asymmetric Transformers”, IEEJ J. Industry Applications,
vol.9, no.6, pp.703-712, 2020.
Hwa-Pyeong Park, Yesung Kang, Seokhyeong Kang, Jee-Hoon
Jung, "FPGA Controller Design for High-Frequency LLC Resonant
Converters", IEEJ J. Industry Applications, vol.9, no.5, pp.523-529,
2020.
Sandeep Kumar Chowdhury, Hiroyasu Kobayashi, Keiichiro
Kondo, “Design Optimization of Power Electronic Transformers inTraction Applications”, IEEJ J. Industry Applications, vol.9, no.6,
pp.674-684, 2020.
Yutaro Tashiro, Hitoshi Haga, Improvement of Light-Load
Efficiency by using a Six-Arm Converter with Series-Parallel
Switching, IEEJ J. of Industry Applications, vol.10 no.2, pp.273281, 2021.
H. Bai and C. Mi, “Eliminate Reactive Power and Increase System
Efficiency of Isolated Bidirectional Dual-Active-Bridge DC–DC
Converters Using Novel Dual-Phase-Shift Control”, IEEE
Transactions on Power Electronics, vol. 23, no. 6, pp. 2905-2914,
2008.
S. A. Khan, M. R. Islam, Y. Guo and J. Zhu, “A New Isolated
Multi-Port Converter With Multi-Directional Power Flow
Capabilities for Smart Electric Vehicle Charging Stations”, IEEE
Transactions on Applied Superconductivity, vol. 29, no. 2, pp. 1-4,
2019.

[9]

K. Suresh et al., “A Multifunctional Non-Isolated Dual Input-Dual
Output Converter for Electric Vehicle Applications”, IEEE Access,vol. 9, pp. 64445-64460, 2021.
[10] Y. Xia, M. Yu, Y. Zhang, Z. Lv and W. Wei, "Decentralized
Suppression Strategy of Circulating Currents Among IPOP SinglePhase DC/AC Converters," in IEEE Journal of Emerging and
Selected Topics in Power Electronics, vol. 8, no. 2, pp. 1571-1583,
2020.
[11] J. Shi, L. Zhou and X. He, "Common-Duty-Ratio Control of InputParallel Output-Parallel (IPOP) Connected DC–DC Converter
Modules With Automatic Sharing of Currents," in IEEE
Transactions on Power Electronics, vol. 27, no. 7, pp. 3277-3291,
2012.
[12] Y. Xia, M. Yu, Y. Zhang, Z. Lv and W. Wei, "Decentralized
Suppression Strategy of Circulating Currents Among IPOP SinglePhase DC/AC Converters," in IEEE Journal of Emerging and
Selected Topics in Power Electronics, vol. 8, no. 2, pp. 1571-1583,
2020.
[13] J. Nie, L. Yuan, Q. Gu, J. Sun and Z. Zhao, "A Coordinate andDistributed Control Scheme for Multilevel and Multi-Stage
Medium Voltage Solid State Transformer," 2018 International
Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia),
pp. 2963-2968, 2018.