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Abstract—This work deals with the development of a multi- chargers have to be light weight and small in size so that they
functional power electronic converter (PEC) utilizing dual power can easily fit inside EVs. Further, the on-board chargers are
sources (grid and solar photovoltaic (PV)) for charging phe- more attractive for EVs because this types of charger is always
nomenon of plug-in electric vehicles (PEVs). The developed config-
uration accomplished all modes of vehicles (charging, propulsion available with vehicles.
(PP) and regenerative braking (RB)). In standstill condition of The on-board chargers are further classified as single-
vehicle, the battery is either charged by grid or simultaneously by stage charger and two-stage charger. Moreover, in two-stage
both grid and solar PV system. In running mode, the battery can charger [3]–[5], a number of components are employed; there-
also be charged through RB operation by utilizing kinetic energy fore, two-stage charging solution is not much appealing for
of vehicle wheels. The proposed converter operates as an isolated
SEPIC in plug-in charging (PIC) mode and as a non-isolated SEPIC on-board implementation of charging system. While a single-
in solar PV charging mode. Further, in PP and RB modes, oper- stage charging system employs fewer number of components
ation of the proposed PEC as a conventional boost converter and than two-stage charging system; therefore, it is more attractive
conventional buck converter, respectively. Both the simulation and for on-board application of EVs. In conventional single-stage
experimental validations for all modes of the proposed converter charging system, a bidirectional DC-DC converter is connected
have been presented.
between DC-link of inverter and battery for power flow during
Index Terms—Electric vehicles, on-board chargers, solar PV PP and RB modes [6]. To eliminate this bidirectional DC-DC
system, DC-DC converter, power factor correction. converter from single-stage charging system, power electronics
researchers have proposed integrated type of chargers [6]–[10].
I. INTRODUCTION In the integrated charger, the bidirectional DC-DC converter of
conventional single-stage system connected between battery and
SUALLY, the electric vehicles (EVs) battery chargers are
U classified as off-board chargers and on-board chargers [1].
In off-board charging system, the charger is placed outside the
DC-link is integrated with front-end converter at the cost of some
additional switches. The overall integrated system has fewer
number of total components compared to single-stage charging
vehicle premises at a charging station and provides a dc output system.
which is directly plugged to the battery. This type of charger In the available literature integrated charging system utilizes
is not responsible for the vehicle weight; therefore, weight of non-isolated type of converters [11]. Moreover, magnetic iso-
these chargers is very high. As a result, it can be rated for high lation is desirable for vehicle application for safety of vehicle
power and thus the EV battery can be charged within a few users as well as protection of charging circuit. Further reported
minutes. However, an impeding factor for the development of integrated chargers use grid as main source for battery charging
these chargers is the cost. Therefore, number of these chargers and alternatively battery is also charged with RB modes. The
is limited and they are not ubiquitous. chargers [12]–[14] utilize only solar PV power source for battery
In on-board chargers, the battery can be directly charged from charging and have the limitation of power indeterminacy; there-
ac mains, which are widely available everywhere. This kind of fore, reliability of charger is sacrificed. However, recently a solar
charger does not require expensive infrastructure and vehicle PV and grid based isolated 10-kW charger has been proposed
can be charged anywhere, which is a clear advantage. They are in [15], which utilizes a large number of component as well as
further classified as conductive charging or inductive charging. it does not operate in PP and RB modes.
In conductive charging system, the whole charging system is Based on the above literature review, this paper proposes a
placed inside the vehicle. In inductive charging system, a part new grid and solar PV based single-stage integrated charging
of the charger is placed outside of the vehicle [2]. The on-board solution for on-board applications, as shown in Fig. 1. The
main features of the proposed PEC are summarized as (a) dual
Manuscript received October 4, 2019; revised December 14, 2019; accepted sources for charging operation, which enhances reliability of
February 2, 2020. Date of publication February 6, 2020; date of current version the charger, (b) galvanic isolation for better safety of vehicle
April 16, 2020. The review of this article was coordinated by Dr. B. Akin.
(Corresponding author: Ankit Kumar Singh.) users and charging circuit, (c) cost of conventional fuel sources
The authors are with the Department of Electrical and Instrumentation based electricity per charge reduces, (d) achieves all modes of
Engineering, India Thapar Institute of Engineering and Technology, Patiala- vehicle. Apart from above advantages of solar PV and grid based
147001, India (e-mail: asingh10@ee.iitr.ac.in; manoj.badoni@thapar.edu;
ytatte@gmail.com). charging system, there are few additional advantages for baterry
Digital Object Identifier 10.1109/TVT.2020.2971971 charging with solar PV power, which are summarized as: (i)
0018-9545 © 2020 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.
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3718 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 69, NO. 4, APRIL 2020
TABLE I
ANALYSIS OF THE PROPOSED PEC WITH REPORTED METHODS
Fig. 1. Configuration of the proposed PEC. Fig. 2. Operation of the proposed PEC during PIC mode.
EV battery is act as energy storage for solar PV system and on switching devices; therefore, these chargers have higher
reduces the adverse impact of large scale of solar PV power operational efficiency in each mode. The charger [10] has very
integration to the conventional grid system, (ii) long duration high efficiency in PP and RB modes because in these two modes
of parking at workplaces or at home results in low charging the converter has low stresses on switching devices and fewer
power requirement, which enables implementation of vehicle- number of devices encounters in the current path. The major
to-grid (V2G) operation (for V2G operation, diode rectifier will limitation of integrated charger [15] is the presence of large
be replaced by active rectifier), where EV act as controllable number of components and does not operate in PP and RB
power sources, (iii) power demands for battery charging from modes.
grid reduces as solar PV power is generated locally [15], [16]. Rest of the sections are organized as follows: section II
The proposed solution is developed from conventional isolated discusses the converter operation in each mode. In Section III,
and non-isolated SEPIC, which operates as an isolated SEPIC stress analysis and selection of switching devices are discussed.
for plug-in charging (PIC) mode and as non-isolated SEPIC Section IV discusses about design and selection of passive
during solar PV charging. Further, in PP and RB modes, the components. The control algorithms for different modes are
proposed integrated converter operates as boost converter and discussed in section V. The simulation and experimental results
buck converter, respectively. have been presented in section VI. Finally, concluding remarks
A detailed analysis of the proposed PEC with reported meth- drawn from the study are given in Section VII.
ods is investigated in the following paragraph using Table I.
The comparison is carried with respect to galvanic isolation, II. OPERATING MODES OF THE CONVERTER
availability of solar PV charging, number passive components In this section, operating modes of the proposed PEC are
and semiconductor devices, and buck/boost capabilities. discussed in detail. States of the switching devices are shown in
From Table I, the existing integrated chargers [7]–[10] do not Table II.
have magnetic isolation between battery and grid as well as solar
PV charging capability. Moreover, integrated charger reported
A. Grid Mode
in [7] has the capability of buck-boost operation in all modes
but this charger has lower efficiency in all modes because it When solar power is not available, the battery is charged
utilizes a number of components in the current path. The reported through grid power. When switch Sa1 turns ON, the rectified grid
integrated chargers [8], [9] can not be effectively used for battery voltage is applied to inductor L1 and current through it builds
charging when peak grid voltage is more than the battery voltage up and L1 stores magnetic energy. The path of current through
(at low state of charge (SOC)) because these converters operate inductor L1 is shown by solid lines in Fig. 2. Moreover, the
only in boost mode. However, integrated chargers [8], [9] have capacitor Cs transfers its stored energy to magnetizing inductor
low component counts and lower voltage and current stresses Lm of high frequency transformer (HFT). In this duration,
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SINGH et al.: MULTIFUNCTIONAL SOLAR PV AND GRID BASED ON-BOARD CONVERTER FOR ELECTRIC VEHICLES 3719
TABLE II
SWITCHING STATES OF SEMICONDUCTOR DEVICES AND MECHANICAL SWITCHES IN ALL MODES
Fig. 3. Operation of the proposed PEC during solar PV mode. Fig. 4. Operation of the proposed PEC during PIC and solar PV modes
(simultaneously).
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3720 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 69, NO. 4, APRIL 2020
TABLE III
PEAK VOLTAGE AND CURRENT STRESS ON SWITCHING DEVICES IN ALL MODES
where NC = Not conducting, NIL = 0 V, iL1,pp = inductor L1 current in PP mode, iL1,RB = inductor L1 current in RB mode, iLm,grid = magnetizing inductor Lm current
in PIC mode, ipv,max = peak solar PV current.
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SINGH et al.: MULTIFUNCTIONAL SOLAR PV AND GRID BASED ON-BOARD CONVERTER FOR ELECTRIC VEHICLES 3721
Vb (1 − d3 )
L1RB = (5)
η fs
where d3 is equal to VVhv
b
. For 10% ripple current, the value L1RB
is calculated as 1.63 mH.
The final value of inductor L1 is selected as
L1 = max(L1P IC , L1P P , L1RB ) = max(1.78, 1.65, 1.63)
(6)
Therefore, the final of L1 is 1.78 mH and selected value for
simulation experimentation studies.
The value of magnetizing inductance Lm for ripple ξ% of the Fig. 7. Control strategy for PP and RB modes.
grid (ig ) is expressed as [19]
(1 − d1 (t)) Vg2 1 Vb where δ represents the voltage ripple in (%) across capacitor Cb ,
Lm = V b = (7) ω = 2πfL and fL is the grid frequency (50 Hz). For 5% voltage
ΔILm (t)fs Pg ξfs vg (t) + Vb
ripple in Cb , the size of capacitor Cb using (10) is chosen as
where ΔILm (t) = ξ% of the gird current (ig ). The turn ratio of 1200 μF for simulation and experimentation studies.
HFT is selected as unity for this design. The value of Lm for a The DC-link capacitor Chv is determined by PP mode, which
permitted current ripple (10% grid current) is calculated as 2.1 is given as [18]
mH and selected as 2 mH for simulation and experimentation
d2
studies. Chv = (11)
The value of middle capacitor Cs for voltage ripple k% of vcs Rfs Δv
Vhv
hv
is given as [6] where Δvhv is the ripple voltage in capacitor Chv . From (11),
Vb d1 (t) the value of Chv is calculated as 83.5 μF for Δvhv = 1% of Vhv .
Cs = (8) The selected value of Chv is 100 μF.
kvcs (t)fs RL
The design of MPPT converter (non-isolated SEPIC) is car-
where vcs is the voltage across capacitor Cs by substituting ried out in similar way as isolated SEPIC.
d1 (t), vcs (t)= |vg (t)| and equivalent load resistance RL =
Vb2 /Pb in (8), we can get V. CONTROL ALGORITHM
Vb Vb In this section, control techniques for each mode of vehicle
Cs =
k|(vg (t)|fs Pbb | vg (t) | +Vb
V2 operation are discussed using Figs. 6 and 7.
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3722 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 69, NO. 4, APRIL 2020
TABLE IV TABLE V
CIRCUIT PARAMETERS FOR SIMULATION AND EXPERIMENTATION PARAMETERS OF SOLAR PV SYSTEM
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SINGH et al.: MULTIFUNCTIONAL SOLAR PV AND GRID BASED ON-BOARD CONVERTER FOR ELECTRIC VEHICLES 3723
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3724 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 69, NO. 4, APRIL 2020
TABLE VI
COMPONENT LIST USED FOR DEVELOPMENT OF EXPERIMENTAL SETUP
Fig. 17. Voltage waveform across switch Sa1 and diode D6 in plug-in mode.
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SINGH et al.: MULTIFUNCTIONAL SOLAR PV AND GRID BASED ON-BOARD CONVERTER FOR ELECTRIC VEHICLES 3725
Fig. 21. Voltage waveform across switch Sa1 and diode D7 in PP mode.
Fig. 18. Waveforms during PIC and solar PV modes (simultaneously) (a)
waveforms of grid voltage, grid current, and solar PV current and voltage (b)
waveforms of solar PV power, battery voltage and battery current.
of any variations in the system either input side or output side. In application, usually PP mode has highest power rating than any
this study, DC-link voltage is selected as 150 V for 48 V battery. other mode [8].
To verify the effectiveness of closed loop control system, the RB modes, kinetic energy of wheels is converted into electric
load power is varied in step manner from 450 W to 550 W. The energy by regeneration process. In this study, this mode is
variation in the battery current at step load changes is shown in tested by manually varying the DC-link voltage through the help
Fig. 20 at CH3. The DC-link voltage is regulated at 150 V for of auto-transformer and rectifier arrangement because DC-link
the load change in Fig. 20 at CH1. The measured battery side voltage changes in accordance with speed of motor in real
current is around 9.8 A hence, and calculated power at battery system. The battery is charged with 10 A of current through
side is 472. 36 W. The efficiency of the converter at 450 W is regeneration process by varying the DC-link voltage from 150 V
approximately 95%. The waveform of voltage across switch Sa1 to 100 V, which is shown in Fig. 22. The waveform of voltage
and diode D7 in PP mode is shown in Fig. 21. In this mode, both across switch Sa2 and diode D5 in RB mode is shown in Fig. 23.
switch and diode experience output voltage i.e.,vhv . Moreover, In this mode, both switch and diode experience input voltage,
low voltage stress (only vhv ) in PP mode is desirable for vehicle i.e., vhv .
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3726 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 69, NO. 4, APRIL 2020
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SINGH et al.: MULTIFUNCTIONAL SOLAR PV AND GRID BASED ON-BOARD CONVERTER FOR ELECTRIC VEHICLES 3727
Manoj Badoni (Member, IEEE) received the Yogesh N. Tatte was born in India, in 1988. He
B. Tech. degree in instrumentation engineering from received the B.E. degree in electrical engineering
the University Science and Instrumentation Centre, from Nagpur University, Nagpur, India, in 2010, the
HNB Garhwal University, Srinagar Garhwal, India, M. Tech. degree in electrical engineering from the G.
in 2006, the M.E. degree in electronics engineering H. Raisoni College of Engineering, Nagpur, India, in
from Punjab Engineering College, Chandigarh, India, 2013, and the Ph.D. degree from the Visveswaraya
in 2008, and the Ph.D. degree in electrical engineering National Institute of Technology, Nagpur, India, in
from Delhi Technological University, Delhi, India, in july 2017. He is currently working as an Assistant
2016. In 2017, he joined the Department of Electrical Professor with the Thapar Institute of Engineering
and Instrumentation Engineering, Thapar Institute of and Technology, Patiala, India. His current research
Engineering and Technology, Patiala, India, as an interests include power electronics, drives and digital-
Assistant Professor. His areas of research interest include power electronics, signal-processing-based control applications.
power quality, and grid integration of renewable energy sources.
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