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AN ADVANCED POWER ELECTRONICS INTERFACE
FOR PHOTOVOLTAIC POWERED INDUCTION MOTOR
BASED ELECTRIC VEHICLE
P.Tulasi Rao 1,
CH.Krishna Rao2,
K.B.Madhu Sahu3
1
P.G Student, Dept. of EEE, AITAM Engineering College, Andhra Pradesh, India,
Associate Professor, Dept.of EEE, AITAM Engineering College, Andhra Pradesh, India,
3
Professor, Principal Dept.of EEE, AITAM Engineering College, Andhra Pradesh, India,
2
ABSTRACT
Interfacing of power electronics is the key concept for clean electrical vehicle technology. In
this paper a new integrated power electronics interface (IPEI) with battery electric vehicles (BEVs) is
proposed to improve the performance of vehicle, to manage the power-flow for each operating mode
and to realize the amalgamation of the DC-DC converter, battery charger, and an inverter in the BEV.
In this paper lithium ion battery is used. The efficiency and reliability of the system are improved
with this proposed idea and also can effectively reduce the current ripples and voltage ripples. With
this proposed model the components (active and passive) size is reduced therefore cost is reduced and
also this technique reduces the stress in switching devices.The proposed model and its controlling
strategy are analyzed and designed by using MATLAB/Simulink.
Index Terms: Battery Electric Vehicles (Bevs), Dc/Dc Boost Converter, Induction Motor, PI
Controller, Power Train Control Strategies, Power Train Modeling, Small-Signal Model.
I. INTRODUCTION
The climate changes due to rising environmental pollution, therefore automobile
manufacturers are pay attention toward pollution free electrical vehicle technologies. Due to several
advances of battery technology with power electronics interfaces (PEIs), and control strategies, these
Battery electric vehicles (BEVs) can replace the IC engines. In general, the BEVs are needs to be
recharged. It reduces dependency on energy because of stumpy energy consumption and zero local
emissions therefore BEVs are called zero-emission vehicles. However, the challenges of BEVs still
have to be solved are driving range is limited, it takes long time to charge, battery should be replaced
over the lifetime, the performance depends on power electronics equipments, and finally high initial
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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 295-309 © IAEME
cost. The major components which are used in EV vehicle system are motor, power source,
controller, charger and drive train. So far the majority of EV system is developed based on dc
machines but due to the disadvantages of dc machines, EV developers explore various types of ac
machines. The induction motor is one which requires less maintenance, low cost; simple in
construction and ruggedness therefore it attracts developers in EV system. [22]. Fig. 2 illustrates the
schematic diagram of the BEV power train.
A. Proposed model of battery electrical vehicle
Fig.1 battery vehicle
Fig.2. illustrates the schematic diagram of the BEV power train.
B. DC-DC Boost Converter
The boost converter converts the available fixed DC supply into variable DC voltage. Usually
the dc-d converters are used to step up the voltage therefore these converters also called boost
converters. These boost converters are under the category of non-isolated converters. The reason for
versatile use of boost converters is because of its continuous current high output voltage mode of
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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 295-309 © IAEME
operations. In this paper DC-DC boost converter is used [17]. The operation of boost converter
Operates either in charging mode or in discharging mode depends on switching controlling i,e ON
and OFF of switches. Boost Circuit consists of inductor, high frequency switch MOSFET, diode and
a filter across load as depicted in below fig.3
The relation between load voltage and source voltage is given as
VS
(1 − D )
t
D = on
T
V0 =
MPPT panel array voltage is the input voltage to the Boost converter. The boost converter
output voltage (Vo) depends on the source voltage (Vi), the duty cycle (D) [17].Where, D = duty
cycle, ton = total time interval.
The DC-DC Boost converter is shown in the below figure.3
a)
Boost converter circuit
b) Operating phases
c)
Fig. 3. DC-DC Boost converter Circuit
C. Space-Vector Pulse Width Modulation (SVPWM)
SVWPM technique is the idea to generate the PWM signals to increase the output voltage of
inverter. This technique was first proposed in -1980s.Now it has become the most essential PWM
method for three-phase inverters [9]. In this paper SVPWM technique is used to control the inverter
to maximize the performance of drive and minimize the power losses. Microprocessor technology
helps to implement Several SVPWM schemes. The switching losses are reduced, harmonic content is
lessened, and finally controlling is very precise. SVPWM technique utilizes the DC bus voltage
effectively when compared with the SPWM technique, generates less THD [10]. SVPWM inverter
capacity is Peak fundamental magnitude is 90.6%. Maximum voltage increased by SVPWM is 15.5%
[10]. A reference vector is rotating around the state diagram there by SVPWM is accomplished. A
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ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 295-309 © IAEME
circle can be created inside the state map by touching all the maximum points of vectors. There are
two regions in the representation of SVPWM, under- modulation region and over-modulation region,
these regions depends on modulation the index.
Fig.4. Space Vector Representation
D. DC-AC Three-Phase Inverter
DC to AC converter is called as an Inverter. Inverter generates required voltage or frequency
by operate it at proper switching control technique. For high power applications three-phase inverters
are commonly used [9]. Three half-bridge units makes this inverter and consists of switching devices
like IGBTs, BJTs, GTOs etc. the switching control depends on the power level and desired
frequency. The switches on the same leg should not turn on at a time [11]. Gating pulses in 3-ph
inverterare delayed by 120 degrees. Six possible modes of operation in each cycle and has time
period of 60 degrees. Therefore 3-ph voltages are lag by 120 degrees. The output of inverter is a
square waveform when it is not connected to a transformer. This square waveform can be converted
to sine waveform by using LC low pass filter.
E. Control Strategy of Induction Motor
In this literature control techniques of Induction motor drives are proposed. The most popular
and advanced one is vector control technique used in automotive applications. In this case, the torque
control is extended to transient state and allows better dynamic performances. In this paper DTC is
proposed for EV applications due to its simplicity [7]. Speed or position encoders do not involved in
DTC and it only measures current to estimate flux, torque. Reference speed as the input to the motor
controller, this reference speed is directly applied with pedal of the vehicle. In this model PI
controller is used in a closed loop to regulate the speed of the motor and also reduce the steady state
error. The error signal is generated in a closed loop system by comparing actual speed of the motor
with the reference speed. Difference between the actual and desired speed gives the amplitude and
polarity of the error signal. To overcome this generated error signal, the PI controller generates the
corrected stator frequency of IM [14]. In DTC the switching loss and torque ripples are high because
of the use of hysteresis band. SVPWM technique is used to reduce the ripple and also to control the
induction motor in a closed loop manner. The advantage of this closed loop controlling is based on
output speed, the frequency and amplitude of the reference signals will change [5]-[8].
II.DYNAMIC MODELING OF POWER TRAIN
A. Dynamic Modeling of the Battery System
The battery is a device which stores energy in the form of electrochemical form. All EV
systems widely use this storage device. In this literature lithium-Ion batteries used as an optimal
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choice for storage of energy in EV applications [17-18]. The mathematical modeling of the Li-Ion
battery is used in this paper, Thevenin battery model is defined in simulation program. The Thevenin
battery model has an internal resistance Rint, over voltage resistance (Rp, polarization resistance),
polarization capacitance Cp, and open circuit voltage Voc[21].The elements which are modeled are
the functions of the battery state of charge (SoC). Fig. 5 shows the model of Thevenin battery. In this
modelNbatts cells are connected in series and Nbattp cells are connected in parallel. By using look-up
tables the parameters of Li-Ion battery are determined based on experimental data. Here VBatt is the
terminal voltage of the battery pack.
Fig.5. Thevenin battery model.
B. Dynamic Modeling of EM
IM is the most suitable choice in automotive industry for EV systems, due to their,
ruggedness, reliability and low cost. Stator current of induction motor is decoupled into flux and
torque by using field-oriented control (FOC) and it gives independent commands on the motor
torque, speed control is more accurate, this controlling is similar to that of a separately excited DC
motor [4]-[7].
The main use of the IFOC is that it completely decouples the direct and quadrature currents.
That is any change in torque may change the quadrature current and any change in direct current will
affect the magnitude of flux linkages. Thereby, to realize the concept of the FOC, the dq model of the
IM is required in synchronous reference frame.
In induction motor the distribution of mmf is sinusoidal along the air gap. The dq model of 3ph IM in a synchronous reference frame is used in this paper, for a dynamic analysis. As shown in
Fig. 6, dq model is considered with core losses and is represented as core resistance Rf [5]–[8]. All
machine variables transform into the synchronous reference frame. The synchronous reference frame
stator and rotor voltage equations can be written asin this fashion [26]:
Fig. 6. The dq equivalent circuit of the induction motor in synchronous reference frame.
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ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 295-309 © IAEME
e
qs
e
s qs
v = R i + Lls
diqse
dt
vdse = Rs idse + Lls
e
qr
+ Lm
e
diqm
dt
(
e
+ we Llsidse + Lmidm
)
didse
die
e
+ Lm dm − we Llsiqse + Lmiqm
dt
dt
e
r qr
v = 0 = R i + Llr
vdre = 0 = Rr idre + Llr
(
(5)
)
(6)
)
(7)
didre
die
e
+ Lm dm − wsl Llriqre + Lmiqm
dt
dt
(8)
diqre
dt
+ Lm
e
diqm
dt
(
e
+ wsl Llridre + Lmidm
(
)
where the magnetizing currents can be given as
e
e
iqm
= iqse + iqre − iqfe
(9)
e
e
idm
= idse + idre − idfe
(10)
The electrical torque equation can be expressed as
3 p Lm e e
iqs idr − idre i qre
2 2 Lr
where:
P = number of poles of the machine;
Vds ,Vqs = dq axes of the stator voltages;
idr ,iqr = rotor currents;
idm ,iqm = dq axes magnetizing currents;
Rs ,Rr = stator and rotor resistances;
Lls ,Llr = self-inductance of the stator and rotor
[
Te =
]
(11)
III. SMALL-SIGNAL MODEL OF BMDIC (SSM)
To analyze the nonlinear systems such as dc/dc converters, SSM is best method. SSM is
essential in manipulating of the closed-loop control for PWM dc/dc converters to attain a definite
performance [19], [28]. SSM is derived in continuous current mode (CCM) to model the proper
controller using bode plot. The transfer function of the duty cycle and the inductor current has been
proposed and also the transfer function of the duty cycle and the output voltage is also presented in
this paper. The small-signal transfer functions in CCM are derived as follows:

s 
s 
1 +
1 −

w
v
w
z 1 
z v2 
Gvd (s ) = ∧
= Gdv 
∆(s )
d (s )
∧
(12)
V0 (s )

s 
 1 +

w z 1 

G id (s ) = ∧
= G di
∆ (s )
d (s )
(13)
∧
i L (s )
Here is the assumption that the parameters are ideally the same values to simplify the analysis. That
is L1 = L2 = L,RL1 = RL2 = RL, and IL1 = IL2 = IL . Therefore
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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 295-309 © IAEME
Gdv =
v0
(14)
 − 2RL + 2(1 − 2D)2 R0 

δRL + 2(1 − 2D)2 R0 
(1 − D ) 
ω zv1 =
1
CRC
(15)
ω zv 2 =
2(1 − 2 D )2 R0 − 2 RL
2L
(16)
∆ (s ) =
ς=
s2
ω02
+
(17)
s
+1
Qω 0
δL + C (δRL (R0 + RC ) + 2(1 − 2 D )2 R0 RC )
2
(18)
δLC (R0 + RC )[δRL + 2(1 − 2 D ) R0 ]
2
1
2ξ
(19)
 1 − 2D 

 1− D 
(20)
Q=
δ =
Gdi =
ω zi =
IL =
Vo (2 + δ )
δRL + 2(1 − 2 D )2 R0
(21)
1

δR0 
C  RC +

(2 + δ ) 

(22)
V2
V0
, Ro = 0
P0
2(1 − 2 D )R0
(23)
Where,
L is the inductance, Vo is output voltage, C is the capacitance, RC is the internal resistance of the
capacitor, RL is the internal resistance of the inductor, m is the number of the parallel switches per
phase, n is the number of phases, Vin is input voltage, Ro is the resistance of the load, Po is the
output power andD is the duty ratio.
Fig.7. Speed control system.
IV. RESULTS AND DISCUSSION
The proposed system, advanced power electronics interface for solar powered induction
motor drive for electrical vehicle applications, is analyzed on MATLAB Simulink platform; involves
modelling of solar modules, design of DC-DC converter with MPPT algorithm, and inverter fed
speed control of induction motor. After successful completion of all the above mentioned
subsections, results have been captured and presented below.
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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 295-309 © IAEME
Ambient Irradiation of solar PV modules in W/m2
Irradiation(W/m 2 )
1000
Irradiation
800
600
400
200
0
0
0.05
0.1
Time(sec)
0.15
0.2
Fig 8. Ambient irradiation of solar PV modules
The irradiation shown in fig8 is fed to solar modules, modelled in matlab, produced dc power.
This dc natured power supply is fed to dc-dc boost converter, which employed with MPPT algorithm
to track maximum power from PV modules, output parameters are presented in figs. 9 and 10
respecively.
Fig 9. MPPT based dc-dc converter output voltage
MPPT based DC-DC Converter Current
3
2.5
IDC(A)
I
dc
2
1.5
1
0.5
0
0
0.05
0.1
Time(sec)
0.15
0.2
Fig 10. MPPT based dc-dc converter output current
To analyze stability of MPPT based dc-dc converter bode plot is drawn in matlab, found its
PM=57.5 and GM=3.92 respectively, revealed that designed converter is fully satble.
Fig 11. Bode plot of DC-DC converter
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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 12, December (2014), pp. 295-309 © IAEME
This DC power coming from DC-DC converter is fed to inverter fed induction motor, which
operating in closed loop to control the speed. Inverter fed induction motor drive is tested under
different loading conditions and its output for 100% loading is presented below. Inverter output
currents are shown in Fig 12.
Stator Currents
100
Ia
Ib
Iph(A)
50
Ic
0
-50
-100
0
0.05
0.1
Time(sec)
0.15
0.2
Fig 12. Inverter output currents
Actual and Reference Speeds of Induction motor drive
200
W Reference
Speed(rad/sec)
150
W Actual
100
50
0
-50
0
0.05
0.1
Time(Sec)
0.15
0.2
Fig 13. Speed of induction motor drive
From fig.13, it can be observed that proposed system is driving the induction motor at
specified speed.
V. CONCLUSION
Matlab based simulation reveals that, Modelled solar modules process dc natured power
supply fed dc-dc converter with MPPT algorithm tracks maximum power from modules. Bode plot
based analysis helped to judge stability of dc-dc converter, found that designed dc-dc converter is
fully stable. Based on MATLAB based simulations, it is found that proposed advanced power
electronics based interface is suitable to drive the induction motor at different reference speeds under
different loading conditions.
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ISSN Print: 0976- 6464, ISSN Online: 0976 –6472
AUTHORS DETAILS
Mr.P.Tulasi Rao received the B.Tech Degree in Electrical & Electronics
Engineering from Aditya Institute of Technology Management,Tekkali,
Srikakulam,India in 2012. Currently persuing M.tech in Aditya Institute of
Technology & Management,Tekkali, Srikakulam,India. His research interests
include power quality, power systems , Power electronics.
Sri.CH.KrishnaRao obtained B.Tech Degree in Electrical and Electronics
Engineering from College of Engineering, GMRIT Rajam and Srikakulam Dt. He
also obtained M.Tech in Power Electronics and Electric Drives from ASTIET
Garividi, Vizayanagaram. He has 12 Years of Teaching Experience. Presently he is
working as associate professor in the Department of Electrical & Electronics
Engineering, A.I.T.A.M, Tekkali, and SrikakulamDt Andhra Pradesh. He has
published number of papers in journals, national and international conferences. His
main areas of interest are power electronics, switched mode power supplies,
electrical drives and renewable energy sources
Dr.K.B.Madhu sahu received the B.E. Degree in Electrical Engineering from
college of Engineering. Gandhi Institute of Technology &Management,
Vicakhapatnam, India in 1985 and the M.E Degree in power systems from college
of Engineering, Andhra University and Visakhapatnam in 1998. He obtained his
Ph.D from Jawaharlal Nehru Technological university .Hyderabad. He has 26 years
of Experience. Currently he is working as a professor & Principal in the
Department of Electrical & Electronics Engineering, AITAM, Tekkali, and
Srikakulam. Dt.Andhra Pradesh. His research interests include gas insulated
substations, high voltage engineering and power systems. He has published
research papers in national and conferences.
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