Development of an integrated power converter for fast charging and efficiency enhancement in electric vehicles

Development of an Integrated Power Converter For Fast Charging and Efficiency Enhancement In
Electric Vehicles, Mr.Jeby Thomas Jacob, Dr.D.Kirubakaran, Journal Impact Factor (2015): 7.7385
(Calculated by GISI) www.jifactor.com
www.iaeme.com/ijeet.asp 1 editor@iaeme.com
1
Research Scholar, EEE Department,
Sathyabama University, Chennai, Tamilnadu,India
2
HOD, EEE Department,
St.Joseph’s Institute of Technology, Chennai, Tamilnadu, India
ABSTRACT
Electric Vehicle (EV) industry is booming from the last two decades due to the foreseen
reduction in fossil fuels. The main hindrance confronted by the EVs is the low reliable storage
capacity and reduced conversion efficiencies. Major studies are going on in the field of power
density improvement in power electronics used in electric vehicles leading to the development of
highly efficient EVs. Reduced size of the converters, storage system, response of tight speed
controllers are the major challenges in Electric vehicle designing segment. The charging solutions
for different segments of Electric vehicles are the other areas posing challenges. In this paper a new
method of charging technique is proposed for Low, Medium and High power Electric vehicles. The
charging topology increases the efficiency of the EVs by harvesting the energy dissipated during the
braking period and further utilising it for the propulsion with the aid of high efficient light weight
storage devices like Ultra capacitors. By this system the size of batteries and charging time can be
drastically reduced.
Keywords: Component; Integrated Power Converters, Ultra Capacitors , Electric Vehicles
I. INTRODUCTION
By the increasing demand of Electric Vehicles the drive train technology has to be modified
for a logner period . Both Plug in electric chargers and contact less chargers are finding distinct
place in the electric vehicle topologies. The main challenges of electric vehicle charging systems are
the speed of charging , the size of the charger, storage device size and cost, reliability.
With the new generation technology batteries the need of more on-board battery capacity for
all electric vehicles is fastly accepted.
But the main disadvantage of most of the systems are low speed charger[1]. In case of high
current charging the life of battery also will get decreased. Siemens , Tesla introduced new on road
plug in charging mechanism in the late 21st century.
DEVELOPMENT OF AN INTEGRATED POWER CONVERTER
FOR FAST CHARGING AND EFFICIENCY ENHANCEMENT IN
ELECTRIC VEHICLES
Mr.Jeby Thomas Jacob1
, Dr.D.Kirubakaran2
Volume 6, Issue 6, June (2015), Pp. 01-09
Article ID: 40220150606001
International Journal of Electrical Engineering & Technology (IJEET)
© IAEME: www.iaeme.com/IJEET.asp
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
IJEET
© I A E M E

II. PROPOSED SYTEM
Block diagrammatic Representation of the proposed topology is shown in figure 1
Figure: 1 Block diagram of the proposed topology
The system consists of an Integrated Power Controller which is explained in the later sections,
will allow the impulse high energy produced at the time of braking to be utilized effectively for the
driving mode .
The Integrated power controller is a modified controller explained in [2] which integrates the
charging operation for a plug in electric vehicle, driving mode operation with minimum stress on the
batteries, energy harvesting during the braking mode and power saving during idling mode which is
the constant speed operation as the vehicle doesn’t need a high electrical energy input during a
constant speed running.
A.Capacitor Charging (UCCC)
The high energy obtained during the regenerative period is utilized in an efficient manner for
the propulsion mode after a braking mode. A special circuit topology has been designed for this
purpose UCCC (Ultra capacitor charging circuit), as the switching components has to withstand high
current and voltage during this phase of operation. The rating of the UC is selected according to the
energy requirement it has to supply during the driving mode. i.e., the driving mode after a braking
mode will increase the load on the battery and battery will not be able to give an immediate energy
required for overcoming the inertia of the system and continuous overloading of the battery bank will
reduce the life of the battery.
The operation during the regenerative power harvesting is divided into three modes first is the
charging mode where the capacitor is charged from an initial voltage to the final rated voltage [2].
This duration of charging is depended by the UC of the bank and the other is the refresh mode or
standby mode where the stored energy is maintained and the third mode is discharge mode as shown
in figure 2. The discharge mode will happen when the battery output voltage is dropped below a
predetermined value the UC has to deliver the stored energy for the propulsion mode operation.
Figure :2 Ultra capacitor charging cycle

The Ultra capacitor charging during the regenerative period is done using a series pulsed
charger topology. The series pulsed charger topology helps the UC to charge without increasing the
peak current. The UC capacitor is charged with a train of pulses instead of the direct charging from
the High power obtained at the time of braking.
The energy of the UC can be generalized by the equation:
KJ/s= (1)
Where is the energy delivered to the load per charging cycle and T is the repetition rate of the
UC Soft switching technique is also employed in the converter for increased efficiency during the
operation[3]. The width of the pulse train is controlled with a pulse width modulated strategy
III. PROPOSED CONVERTER TOPOLOGY
Figure 3: Circuit diagram of the proposed Integrated Power converter
A. Circuit operation and theoretical analysis
The topology consists of five IGBT switches for its complete operation. Switches S1,
Depending on the storage battery and capacitor voltages a bidirectional dc/dc converter is designed
and integrated into the circuits. The circuit integrated here is the modified two quadrant luo converter
for the two modes of the operation mainly the propulsion mode and regenerating mode [4] [5].
Operation Modes
The modes of operation of the converter is divided into four:
1) Charging operation
2) Driving operation
3) Braking operation
4) Idling operation

a) Charging operation
The charging mode of the converter involves the operation of mainly three switches. The
integration of the circuit removes the drawbacks possessed by other circuits for electric vehicles like
more number of switches, complex switching strategy and increased weight and volume due to the
switches.
The proposed charger can be utilized for level 1 and level 2 types of chargers where level one
chargers can charge the battery from a single phase at 120Vac up to 1.92KW, Level two chargers can
chargers are rated at 240Vac at 19.2KW
The charging circuit comprises of two circuits with different polarity of the grid voltage in the
charging operation.
(i)Switch Ig1 kept on during the charging operation and Ig3 is based on the output voltage and
current ratings required. During the on time Ig3 the inductor charges up and the current path is D2-L
–S3
(ii) When the Switch Ig1 is turned off inductor current discharges as the battery load is connected to
the circuit. When the line voltage becomes negative Ig2 is switched at a frequency rate preset and the
current flows from the power supply to D2-L –Ig2 and to the battery the charging happens through
L- D1-D2.
B. Driving operation
In the driving mode operation the electrical energy obtained from the battery and UC is given
to the drive train [6]
Figure 4: Driving mode equivalent circuit
Figure 4 shows the equivalent circuits of the Driving mode equivalent circuit.
In the driving operation we have the output current is found from analysis is:
= (2)
And
=
( )/ )
( ) !"
(3)
Where Input source voltage that is the charging mode output voltage is V1 and the ultra
capacitor voltage is V2. Switches Ig1 and Ig2 are IGBTs and they are driven by the PWM switching
frequency designed according to the circuit operation with a repeating frequency ‘f’ and conduction
duty ‘k’.[7]

Switch repeating period T= 1/f, and the switch on period is kT, switch off period (1-k)T.
The minimum conduction duty k corresponds to
#$%& =
(
(4)
Efficiency of the system is η =
)
)
=
*
*
=
(( ))/ ( ) ( * / [
( )
,
(5)
The variation ratio of capacitor voltage -., Inductor current ( / and / ) and the variation of
diode current are all found out
Figure 5: The waveforms of Driving and braking mode
C.Braking operation
The equivalent circuit for the braking operation is show in figure6. Typical output voltage
and current waveform are shown in figure 5
In this mode the output current is given by the equation
Figure 6: Braking mode operation equivalent circuit
= (6)
Also
=
( )( )
!" ( )
(7)

The minimum conduction duty cycle k corresponding to = 0 is given by
1$%& = (
(8)
IV MATLAB SIMULINK MODEL OF THE PROPOSED INTEGRATED CONVERTER
Figure 7: Simulation Circuit of the Integrated Power Converter
D.Idling mode
During this mode the S1 switches on and charges the UC when extra energy is being feeded
to the drive train. Then during the period of Driving the energy is pumped out from the UC first and
after the initial inertial is attained. The system switches over to normal mode of operation in Battery.
IV.SIMULATION MODEL OF THE PROPOSED SYSTEM and RESULTS
The simulation mode is designed using Matlab simulink software as shown in figure 7. The
four operation modes were simulated separately using switch conditions as shown in figure 8 [8]
Figure 8: Switching strategy for charging operation

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Switching wave form during the Driving
Figure 9: Switching Wave form for
The simulation results clearly shows the capability of the charging section to maintain a high
power factor and to charge the battery fast compared to other Converting topologies.
current follows the waveform of voltage
system in this case, the distortion in wave form is minute
The input side power equals to the output side power so the battery side current can be
expressed as.
234(5)= 6
789 :
(1 < cos(2A5))
Where -$ is the maximum instantaneous input voltage of the charging
battery voltage and BC is the variable circuit impedance.
Simulation Results for Charging operation with an input voltage of 230 Voltage
Figure 10:
n Integrated Power Converter For Fast Charging and Efficiency Enhancement In
Mr.Jeby Thomas Jacob, Dr.D.Kirubakaran, Journal Impact Factor (2015): 7.7385
www.iaeme.com/ijeet.asp 7
the Driving, Braking and Idling modes are shown in
Switching Wave form for Drive, Braking and Idling Mode.
power factor and to charge the battery fast compared to other Converting topologies.
of voltage. Even with an RL load which is considered to be the drive
ion in wave form is minute. [9][10]
) (9)
is the maximum instantaneous input voltage of the charging
is the variable circuit impedance.
ure 10: Simulated results for the charging operation
n Integrated Power Converter For Fast Charging and Efficiency Enhancement In
Mr.Jeby Thomas Jacob, Dr.D.Kirubakaran, Journal Impact Factor (2015): 7.7385
editor@iaeme.com
modes are shown in Figure: 9
Braking and Idling Mode.
power factor and to charge the battery fast compared to other Converting topologies. The input
h is considered to be the drive
is the maximum instantaneous input voltage of the charging supply, -DEF is the
Simulated results for the charging operation

In Figure 10 the simulated results output shows that the Power factor is high. The first profile
is the voltage and the second one is current (charging current of the battery) follows the same
waveform during charging operation
Figure 11: Simulated results for the Braking operation
This simulated results shows the voltage across the Ultra capacitor is in a pulsed form and
thus reducing the continuous stress on the capacitor. The first graph of figure: 11 is the voltage
across the UC, the second one is the current wave form during in a pulse form. The energy obtained
during braking mode is stored and is reused in an efficient manner by this topology rather than the
direct supply of power from the energy storage elements.
V.CONCLUSION
A new method of charging technique is proposed and simulated for Low, Medium and High
power Electric vehicles. The systems output is found to have increased efficiency and faster charging
responses. The efficiency of the EVs is increased by harvesting the energy dissipated during the
braking period and further utilitsing it for the propulsion period with the aid of high efficient light
weight storage devices like Ultra capacitors.
REFERENCES
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Single Stage Integrated Power Electronics Interface for Automotive Applications,” IEEE
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