A Novel Battery Charger for Plug-in Hybrid Electric

Proceeding of the IEEE
International Conference on Information and Automation
Shenyang, China, June 2012
A Novel Battery Charger for Plug-in Hybrid Electric
Vehicles
Liangrong Wang1,2,4, Jianing Liang1,2, Guoqing Xu2,3, Kun Xu1,2,4, Zhibin Song1,2,4
1
Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences Shenzhen 518055,China
2
The Chinese University of Hong Kong Shatin, Hong Kong, China
3
Department of Electrical Engineering, Tongji University, Shanghai 200092, China
4Graduate University of Chinese Academy of Sciences Beijing 100049,China
{wang.lr, jn.liang, kun.xu,zb.song}@siat.ac.cn, [email protected]
charger it should be light in weight and should occupy less
space as it should be on the vehicle all the time, so the smaller
the better and of course, it is very important to minimize the
cost of the charger [2].
Thus, it is normally not practical to have a high-power
level on-board chargers having galvanic isolation. Despite the
isolation is the best choice for charging circuit safety but
sometimes the charger often lacks isolation, as isolation
affects the total cost of the system.
If the traction and charging are not simultaneous, it is
possible to use the components of the traction system, such as
inverter and motor, to reconfigure the charger circuit to
constitute an integrated charger with reduced weight, space,
and total cost [3].
Different types of integrated chargers have been reported
by academia and industry [4]–[14].
An integrated motor drive and charger based on an
induction machine was patented in 1994 by AC Propulsion
Inc. [4] and it has been applied into the automotive industry
[5]. The main idea of the patent is to use the motor as an
inductor during charging time and constitute a boost converter
with an inverter to have unity power factor operation.
Another U.S patent, has been trying to use the motor as
an inverter and the capacitor part of the charging system. All
of these solutions are bidirectional, non-isolated charger with
unit power factor operation and single-phase ac supply. In [6]
two solutions have been proposed by Rippel in 1990.
Rippel and Cocconi proposed another solution in 1992, it
uses the same idea of integration, but there are two
independent inverters in the system [7]. They proposed two
available methods one with two induction motors and another
one with one induction motor with double stator windings.
Also in 1994 Seung-Ki Sul and Sang-Joon Lee proposed
an integral battery charger for a four wheel driven EV[8].The
propulsion system includes four induction motors and four
three-leg inverters with a battery on the system dc bus. By the
use of an extra transfer switch the whole system will be
reconfigured to a single-phase battery charger.
An integrated drive/charger system has been reported in
2005 for a fork lift truck [9].In charging mode, the motor is
used as a low frequency step-down transformer. A woundtype rotor is used in the drive system and for the charging
mode the rotor winding is used as a primary side of the
transformer with the secondary side connected to the grid.
Naturally, there is a galvanic insulation between the grid and
the battery by the means of this transformer.
Abstract - Battery charger plays an important role in the
battery and electric vehicle technology. Due to on-board type of
charger it should be light in weight and should occupy less space
as it should be on the vehicle all the time, so the smaller the
better and of course, it is very important to minimize the cost of
the charger. For a plug-in hybrid electric vehicle (PHEV), when
the battery is charging from the grid, the vehicle should be
parked. The traction system components are normally not
engaged during the charging time, thus it is possible to
reconfigure these components for the battery charger system. In
this paper, an innovative integrated battery charger is presented.
The operation mode of charger can be divided into three modes:
boosting drive motor mode, directly drive motor mode and
charging mode. The analysis of these three modes has been
explained in detail and the control scheme is also introduced in
this paper. The simulation model is built using Matlab/Simulink
software, and simulation results have been presented to verify
the operation for battery charger, showing the system has good
operation performance.
Index Terms - Electric Vehicle (EV). Plug-in Hybrid Electric
Vehicle (PHEV). Integrated Chargers. Battery Charger.
I. INTRODUCTION
The electric vehicles first appeared in the beginning of the
last century .In recent years, where energy conservation and
environmental protection are growing concerns of the world,
the development of electric vehicle technology has taken on
an accelerated pace, that makes people consider electric
vehicles as the main mode of transportation . Since electrical
energy can be transformed from a lot of energy, electric
vehicles will be the most convenient car [1].
After extensive study of electric vehicles we will be able
to adjust the energy structure. Electric vehicles will play a
significant role in energy conservation.
The battery is an important part in the EV and PHEV.
The performance of the battery model is not only dependent
on the design of the model, but also depends on how to use it
and how to charge it. In this case, the battery charger plays an
important role in the battery and electric vehicle technology.
Generally, the charger is divided into two types: on-board
type and off-board type. On one hand, on-board charger can
be used to charge from the household utility outlet in the
evening or at the workplace or malls during the day time or
for emergency charging where no off-board charger is
available. On the other hand, the off-board charger is like a
gas station used for an internal combustion engine vehicle
thus its purpose is charging fast. Due to on-board type of
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168
Battery
Differential
COUPLER
Transmission
Series-parallel
bidirectional
converter
Inverter
Electric
Motor
Grid
Connector
Fig. 3 Block diagram of a novel battery charger for PHEV
is composed of power electronics switching devices, power
diodes, capacitors, inductors, a motor and a grid connector.
Three-phase full-bridge motor drive circuit (motor inverter) is
mainly composed of six power electronic switching devices
and six power diodes. Two other power electronic switching
devices and power diodes forms a series-parallel bidirectional
converter.
Fig. 1 Typical schematic diagram of the parallel configuration PHEV
Fig. 1 shows a typical schematic diagram of the parallel
configuration PHEV. The electrical part includes the gridconnected battery charger, a battery, an inverter, a motor, and
the control system. The main idea [10] is to propose a
multiport device called integrated motor / generator work, as a
motor in the traction mode and an isolated three-phase power
source in the charging mode. With this idea, a standalone
battery charger can be eliminated from the system .Fig. 2
shows the schematic diagram of an integrated charger.
Differential
Transmission
COUPLER
Fig. 4 circuit diagram of a novel battery charger for PHEV
Finally, all components connected together are shown in
Figure 4, as a novel battery charger system for plug-in hybrid
electric vehicles. Charger system is controlled by charger
control drive system which receives current, voltage,
temperature and other signals from the vehicle controller
along with the torque signals, charging signal and the precharge signals. Charger control drive system and vehicle
controller communicate with CAN bus.
Fig. 2 Schematic diagram of integrated charger
In this paper, an innovative integrated battery charger is
presented. The operation mode of charger can be divided into
three modes: boosting drive motor mode, directly drive motor
mode and charging mode. The analysis of these three modes
has been explained in detail and the control scheme is also
introduced in this paper. The simulation model is built using
Matlab/Simulink software, and simulation results have been
presented to verify the operation for battery charger, showing
the system has good operation performance.
III. SYSTEM MODES OF OPERATION
The operation mode of charger can be divided into three
modes: boosting drive motor mode, directly drive motor mode
and charging mode. Depending on the desired mode of
operation, the system hardware is reconfigured.
A. When the system is running in the boosting drive motor
mode:
1) The vehicle controller sends a bus boost instruction to
charger control drive system, and then charger control drive
system sends control signals to the charger system.
2)Series-parallel
bidirectional
converter
execute
switching operation, which consists of two modes: when
transistor T1 diode D1 and D2 are in off-state and transistor T2
is in on-state, the series-parallel bidirectional converter is in
mode 1 ,as shown in Fig. 5a, the current from the battery
II. A NOVEL BATTERY CHARGER CIRCUITS
The system block diagram of a novel battery charger for
plug-in hybrid electric vehicles is showed in Fig. 3.The whole
system constitutes of five parts: a battery, a series-parallel
bidirectional converter, a motor inverter, a motor, and a grid
connector respectively.
Fig. 4 shows the circuit diagram of a novel battery
charger for plug-in hybrid electric vehicles. The whole system
169
flows through the inductor and transistor T2. And when diode
D1 is in on-state and transistor T1, T2 and diode D2 are in offstate, bidirectional converter is in mode 2, as shown in Fig.
5b, The current flows through the inductor and diode D1,
Energy is stored in capacitor, then bus voltage will be raised
to about 400 volts or even more.
B. When the system is running in the directly drive motor
mode:
1) The vehicle controller sends a directly drive instruction
to charger control drive system, then charger control drive
system sends control signals to the charger system.
2) Series-parallel bidirectional converter execute
switching operation, as shown in Fig. 6, diode D1 is in onstate and transistor T1, T2 and diode D2 are in off-state, the
current flows through the inductor and diode D1, then bus
voltage will rise to the battery voltage.
3) In the vehicle controller, charger control drive system
will drive motor to generate the required torque, just like the
boosting drive motor mode.
C. When the system is running in the charging mode and the
vehicle is parked, then:
1)The vehicle controller send charging instructions to the
charger control drive system, charger control drive system
sends power instructions to the charger system, and bus
voltage will rise to about 400 volts or even more.
2) When the relay connection with the grid is closed, the
charger control drive system sends control signals to control
the series-parallel bidirectional converter.
a) Mode 1
b) Mode 2
Fig. 5 The boosting drive motor mode
a) Mode 1
3) The vehicle controller will send a positive (or negative)
torque signal based on the state of car gear. After charger
control drive system receives the instruction of the vehicle
controller, it will drive motor to generate the required torque
by controlling three-phase full-bridge motor drive circuit
(motor inverter).
b) Mode 2
Fig. 7 The charging mode
3)The series-parallel bidirectional converter executes
switching operation, A switching operation consists of two
modes; when transistor T1 is in on-state and transistor T2 ,
diode D1 and D2 are in off-state ,series-parallel bidirectional
converter is in mode 1 ,as shown in Fig. 7a, the current from
capacitor flows through the inductor and transistor T1. And
Fig. 6 The directly drive motor mode
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a) Voltage and current of grid and Dc-link
a) Voltage and current of grid and Dc-link
b) Phase current and motor torque
Fig. 9 Results of the directly drive motor mode.
b) Phase current and motor torque
Fig. 8 Results of the boosting drive motor mode.
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when the transistor T1, T2, and diode D1 are in off-state and
diode D2 is in on-state, series-parallel bidirectional converter
is in mode 2, as shown in Fig. 7b, The current flows through
the inductor and diode D2. By this way, the feedback energy is
transferred to the battery.
IV. SIMULATION AND RESULTS
The whole system has been simulated using
Matlab/Simulink software based on an ideal PMSM and a
converter .
Simulation results are shown in the following figures .In
the figures, Line Voltage, Line Current, DC-link Voltage,
Charging current, PhA, PhB, PhC,Torque are grid voltage,
grid current, bus voltage, battery current, phase A current,
phase B current, phase C current and torque respectively.
A. When the system is running in the boosting drive motor
mode:
In this mode, as shown in Fig. 8, the battery charger is not
connected with grid, so the Line Current is zero and the
series-parallel bidirectional converter raises bus voltage to
about 400 volts. Battery current and motor torque are related,
constant and increases as the load increases .Phase currents
are sine wave ,and the phase difference is 120 degrees. Also
battery current and phase currents are related.
B. When the system is running in the directly drive motor
mode:
In this mode, as shown in Fig. 9, the Line Current is also
zero. And the bus voltage equals to the battery voltage that is
300 volts. Battery current and motor torque is related,
constant and increases as the load increases. Phase currents
are sine wave, and the phase difference is 120 degrees. Also
battery current and phase currents are related.
C. When the system is running in the charging mode:
In this mode, as shown in Fig. 10, the battery charger is
connected with grid, so the Line Current and Line Voltage are
sine wave. The motor is stopped, and only the three inductors
are connected as star, so the torque is zero and Phase currents
are the same. Bus voltage will rise to about 400 volts or more.
Battery current and Line Current are related.
a) Voltage and current of grid and Dc-link
V. CONCLUSION
In this paper, a novel battery charger for plug-in hybrid
electric vehicles has been proposed. The traction system
components are reconfigured for the battery charger system,
because the traction system components are normally not
engaged during the charging time. A simple simulation
experiment results have been presented to verify the operation
for battery charger, showing the system has good operation
performance.
ACKNOWLEDGMENT
This work was supported by the National Natural Science
Foundation of China (Grant No. 51107142). And Basic
Research Project of Shenzhen (Grant No.JC200903170433A).
b) Phase current and motor torque
Fig. 10 Results of the charging mode.
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