Design and Experimental Results of Universal Electric Vehicle Charger Using DSP

TELKOMNIKA, Vol.16, No.4, August 2018, pp. 1435~1444
ISSN: 1693-6930, accredited First Grade by Kemenristekdikti, Decree No: 21/E/KPT/2018
DOI: 10.12928/TELKOMNIKA.v16i4.7308  1435
Received September 15, 2017; Revised June 8, 2018; Accepted June 29, 2018
Design and Experimental Results of Universal Electric
Vehicle Charger Using DSP
Ali Saadon Al-Ogaili*, IshakAris, Mohammad Lutfi Othman, Norhafiz Azis, Dino Isa, Yap
Hoon
Universiti Putra Malaysia, Malaysia
Abstract
Owing to the growing concerns over energy depletion and environmental issues around the
world, more and more attention is given on replacing the fuel-based automobiles with electric vehicles
(EVs) which have the characteristics of zero-emission and low noise. As a result, various countries have
taken specific initiatives to de-carbonize their transport sectors by developing their own EV industry.
Regardless ofthe environmental and economic benefits,substantial scales of grid-connected EVs impose
incredible difficulties to the power grid. The main issues caused by EV charging to the power grid include
harmonics, voltage drop, system instability, system losses and grid overloading. Therefore, this paper
presents design and developmentofa novel method, which is by applying voltage-oriented control (VOC)
algorithm in battery charging of electric bus.The power system of this work consists of three-phase PWM
rectifier. The proposed method is based on mathematical analysis. Simulation and experimental works are
performed to investigate behavior and performance ofthe proposed algorithm.This paperclearly described
implementation of low and medium power laboratory prototype and operation of digital signal processor
(DSP) via MATLAB / Simulink for the proposed method.
Keywords:Dq-theory;electric vehicle (EV); power factor; total harmonic distortion (THD);voltage-oriented
control (VOC)
Copyright © 2018 Universitas Ahmad Dahlan. All rights reserved.
1. Introduction
ELECTRIC vehicles (EVs) are basically controlled by using an electric motor, which is
usually powered up by a rechargeable battery. Presently, strong desire on implementing EVs
with high performance quality has posted significant challenges and stresses on the capabilities
of traditional battery systems. Unfortunately, as technology of battery advances, battery
charging becomes exceptionally complicated due to involvement of high voltages and currents
in the system. Hence, it requires complex charging techniques [1-3] to ensure effective and
efficient charging. This further imposes great distortions in the operating ac power system and
thus an efficient and low-distortion charger is highly needed.
Owing to the issues stated above, battery charging technology faces great deal of
challenges. For instance, how to steadily and efficiently charge the battery, lengthen its
operational life and so on, has tormented the researchers, designers and engineers all the time.
The technology of battery varies differently. Nevertheless, the two commonly applied charging
techniques are known as the constant-pressure and constant-current charging techniques.
Basically, for battery charging, a tributary constant-current power supply (simply known as
constant-current charger) is commonly adopted as external ac voltage which is supplied to the
charger fluctuates continuously. Besides, by using the constant-current charging technique, the
charging efficiency of the battery can be further increased. Moreover, the technique is also
capable of deciding whether to conveniently terminate the charging process based on charging
time and change the numbers of battery [4-7].
On the other hand, constant-pressure charging is another widely applied charging
technique where the idea is to maintain a constant battery voltage between the poles. The main
benefit is that it can automatically adjust the charging current according to the changes occurred
in the battery state-of-charge. For instance, when the voltage has constantly been maintained at
a suitable level, it is not only able to guarantee that the battery is fully charged, but it is also
capable of minimizing the gas chromatography and desiccation. Moreover, various approaches
are available for battery charging such as phase charging and float filling modes [8-13].

 ISSN: 1693-6930
TELKOMNIKA Vol. 16, No. 4, August 2018: 1435–1444
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Based on the input supply of the national grid, this paper presents detailed modeling
and design of a nearly optimum ac current and dc voltage controllers of the voltage-oriented
controlled (VOC) grid connected rectifiers as shown in Figure 1. The design takes into
consideration all practical aspects. Additionally, the effect of controller’s parameters on the
performance of the rectifier is also clearly described. Design concept and effectiveness of the
VOC algorithm are confirmed through extensive simulations and experiments.
θ
S1a
S2a
S1b
S2b
S1c
S2c
Battery
R
+
_
Three-phase
voltage
supply
abc
to
dq
abc
to
dq
ADC ADC
PLL
Decoupled
controller
PWM
generator
dq to abc
ADC
Cdc
VdcLfRf
VOC control system
( DSP TMS320F28335 )
θ Vdc(k)
vabc iabc
vdq(k)
idq(k)
vabc(k)
iabc(k)
v dq_ref (k)
vabc_ref (k)
S12_abc
Rectifier
Carrier
Signal
Gate Drive
Circuit
Gate switching pulses
Voltage
Sensor
Voltage
Sensor
Current
Sensor
Figure 1. Three-phase PWM bridge rectifier of the proposed battery charger with VOC control
algorithm
2. Modeling the System by Using Voltage-Oriented Control (VOC) Algorithm
Highly developed control techniques for grid-connected rectifiers apply the theory of
decoupled active power and reactive power control which is performed in the synchronous
reference direct-quadrature (dq) frame. By using this approach, which is also called the VOC,
the required three-phase ac current is first transformed and decoupled into active (direct) i_d
and reactive(quadrature) i_q component respectively.
The decoupled active and reactive components are then controlledin such a way that
the errors between the desired reference and measured values of the active and reactive
powers are removed. Generally, the active current component i_d is regulated by using a dc-link
voltage control approach which aims to achieve active power flow balance in the system, and
meanwhile the reactive component i_q, is regulated to zero level to ensure unity power factor
operation. The VOC technique applied for grid-connected rectifiers has widely been reported in
its theoretical aspects. In this paper, three proportional-integral (PI) controllers for controlling the
current components i_d, i_qand dc-link voltage V_dcare presented.
3. Decoupled Controller of the First Stage Using Voltage-Oriented Control (VOC)
Presently, three types of controllers have been modeled which includes hysteresis,
proportional-integral (PI) and predictive dead-beat controllers. Most of control techniques have
been proposed, they have high performance, but they still show some obstacles not presenting
the decoupling of the active and reactive current components (not allowing the independent
control of the active and reactive power).
The modules can further be classified into stationary and synchronous dq reference
frame implementations based on the theory of ac machine in rotating field.The controller of

TELKOMNIKA ISSN: 1693-6930 
Design and Experimental Results of Universal Electric Vehicle … (Ali Saadon Al-Ogaili)
1437
PWM rectifier is a useful solution through the application of synchronous frame controller. In this
paper, the controller of PWM rectifier has been modeled in the rotating dq reference frame as
shown in Figure 2. This type of controller is called voltage-oriented control (VOC) and it has high
performance as the synchronous frame controller can effectively reduce steady-state error and
provides quick transient reaction by decoupling control.
id (k)
iq (k)
vdc(k)
+
+
_
_
+
_
2 fLπ
×
+
_
+
_
+
_
+
Kp1
Ki1
+
Kp2
Ki2
×
+
Kp3
Ki3
0
v d (k)
vq (k)
vdc_ref (k)
i q_ref (k)
i d_ref (k)
PI Voltage Controller
PI Current Controller
PI Current Controller
Decoupled
Controller
vd_ref (k)
vq_ref (k)
Figure 2. Decoupled controller
Based on Figure 3, the voltage equations based on Kirchhoff's voltage law (KVL) can be
obtained. To mathematically derive the equation, we start from Figure 3 that shows three-phase
PWM bridge rectifier connection to a grid.Based on Figure 3 v_a, v_band v_c are the input
voltages v_in of the grid and v_ag, v_bgand v_cg are the voltages of the rectifier side. The input
filter implemented by simple L and R elements is the leakage reactance and resistance that
connected between the grid and the rectifier. By applying KVL, the following relationship can be
obtained:
Utility Grid
aV
bV
cV
Grid Filter Grid Side Inverter
agV
bgV
cgV
dcV
Figure 3. Modeling circuit of the grid-connected to the rectifier
𝑣𝑖𝑛 = 𝑖 𝑖𝑛 𝑅 + 𝐿
𝑑𝑖 𝑖𝑛
𝑑𝑡
+ 𝑣𝑖𝑛𝑔
(1)
𝑣𝑎 = 𝑖 𝑎 𝑅 + 𝐿
𝑑𝑖 𝑎
𝑑𝑡
+ 𝑣𝑎𝑔
(2)
𝑣 𝑏 = 𝑖 𝑏 𝑅 + 𝐿
𝑑𝑖 𝑏
𝑑𝑡
+ 𝑣 𝑏𝑔
(3)

 ISSN: 1693-6930
1438
𝑣𝑐 = 𝑖 𝑐 𝑅 + 𝐿
𝑑𝑖 𝑐
𝑑𝑡
+ 𝑣𝑐𝑔
(4)
Next, by applying the theory of Park transformation as shown in Figure 4, voltages and currents
can be transformed from abc system to dq frame as shown in Figure 5.
abc αβ dq
Figure 4. Park transformation βu
αu
du
qu
sU
ωt A axis
B axis
C axis
d axisq axis
β axis
α axis
Figure 5. Phasor diagram of Park
transformation
[
𝑣 𝛼
𝑣 𝛽
𝑣0
] = √
2
3
[
1
−1
2
−1
2
0
√3
2
−
√3
2
1
√2
1
√2
1
√2 ]
[
𝑣𝑎
𝑣 𝑏
𝑣𝑐
] (5)
[
𝑣 𝑑
𝑣𝑞
𝑣0
] = [
𝑐𝑜𝑠 𝜃 𝑠𝑖𝑛 𝜃 0
−𝑠𝑖𝑛 𝜃 𝑐𝑜𝑠 𝜃 0
0 0 1
][
𝑣 𝛼
𝑣 𝛽
𝑣0
] (6)
where v indicates voltage. Hence, by applying the Park transformation in the stationary
referenceframe to (1), the following relation holds
𝑣⃗𝑖𝑛𝛼𝛽 − 𝑣𝑔𝛼𝛽 = 𝐿
𝑑
𝑑𝑡
𝑖⃗𝛼𝛽 + 𝑅𝑖⃗𝛼𝛽 (7)
By considering 𝑥⃗⃗⃗ 𝛼𝛽 = 𝑥⃗
𝑑𝑞 𝑒 𝑗𝜔𝑡, (7) can be rewritten as (8)
𝑣⃗𝑖𝑛𝑑𝑞 − 𝑣𝑔𝑑𝑞 = 𝐿
𝑑
𝑑𝑡
𝑖⃗𝑑𝑞 + ( 𝑅 + 𝑗𝐿𝜔) 𝑖⃗𝑑𝑞 (8)
The voltage equations in dq synchronous reference framearegiven by:
𝑣 𝑑 = 𝑖 𝑑𝑔 𝑅𝑔 + 𝐿 𝑔
𝑑𝑖 𝑑𝑔
𝑑𝑡
− 2𝜋𝑓𝐿 𝑔 𝑖 𝑞𝑔+𝑣 𝑑𝑔 (9)
𝑣𝑞 = 𝑖 𝑞𝑔 𝑅𝑔 + 𝐿 𝑔
𝑑𝑖 𝑞𝑔
𝑑𝑡
+ 2𝜋𝑓𝐿 𝑔 𝑖 𝑑𝑔+𝑣𝑞𝑔 (10)
The power balance equations are:

1439
𝑃 =
3
2
𝑅𝑒{ 𝑣 𝑑𝑞 (𝑖 𝑑𝑞 )∗ } =
3
2
( 𝑣 𝑑 𝑖 𝑑 + 𝑣𝑞 𝑖 𝑞) =
3
2
( 𝐸𝑑 𝑖 𝑑 + 𝐸𝑞 𝑖 𝑞) (11)
𝑄 =
3
2
𝐼𝑚{ 𝑣 𝑑𝑞 (𝑖 𝑑𝑞 )∗ } =
3
2
( 𝑣𝑞 𝑖 𝑑 + 𝑣 𝑑 𝑖 𝑞) =
3
2
( 𝐸𝑞 𝑖 𝑑 + 𝐸𝑑 𝑖 𝑞) (12)
where 𝑃is active power and 𝑄 is reactive power. Since the d-axis rotating reference is aligned
with grid voltage vector, hence𝐸𝑞 can be set at zero and q-axis current is set at zero under
normal conditions tomaintain unity power factor (PF) at grid side converter. With this the power
balance equation becomes:
𝑃 =
3
2
𝐸𝑑 𝑖 𝑑
(13)
𝑄 = 0 (14)
This decoupling makes active and reactive power to control independently by controllingthe
d-axis and q-axis currents as shown in Figure 6.
Load
AC main
PLL
Address
Generator
Clock
Reset
sin_cos
EPROMS
A(0-14)
Voltage
Sense
Current
Sense
Clarke
Park
transform
sin cos
Active and
reactive
power
calculator
(P,Q)
P
Q
dV
qV
dI
qI
aV
bV
cV
aI
bI
cI
Figure 6. Circuit configuration of the active power P and reactive powerQ based on Clarke and
Park transform.
4. Simulation Results
The proposed rectifier system with VOC control algorithm as shown previously in
Figure 1 is simulated and evaluated in MATLAB/Simulink. All the design and test parameters
applied for the simulation work is summarized in Table 1.
Table 1. Parameters for Simulation and Experimental Work
Parameter Value
Resistor load 𝑅𝑙𝑜𝑎𝑑 250 Ω
Input inductance filter 𝐿𝑓 5 mH
Dc-linkcapacitor 𝐶 2200 μF
Dc-link reference voltage 𝑉𝑑𝑐_𝑟𝑒𝑓 100 V
Supply voltage frequency 𝑓 50 Hz
Sw itching frequency 𝑓𝑠 12 kHz
Input resistance filter 𝑅𝑓 1 Ω
Figure 7 shows a sinusoidal reference voltages v_(a_ref) which is used to generate
PWM switching pulses based on intersections with triangular carriersignal. The idea is to directly

 ISSN: 1693-6930
1440
compare the three sinusoidal reference voltages v_(a_ref),v_(b_ref)and v_(c_ref)with the
triangular carrier signal. As a result of the comparative process, the desired switching pulses
S_1abc and S_2abc for controlling the operation of eachpower transistor of the rectifier,
aregenerated.
By accurately control thereference voltage and maintaining its peak value at constant
value of 1V, the magnitude of the generated modulating signal will continuously be maintained
at a level which is lower than the peak of the triangle carrier signal. In other words, the
modulation process will always be maintained at linear modulation zone. This is crucial for
ensuring proper generation of switching pulses. At any instance if the modulating signal is
greater than the carrier signal, the upper switch of the rectifier will be turned “on” and the lower
switch is “off”. In contrast, if the modulating signal is less than the carrier signal, the upper
switch will be turned“off” and the lower switch is “on”. This shows that the operation of upper
and lower switches of the rectifier is always complementing to each other.
Figure 8 shows the input voltage of phase A (110 V) and meanwhile Figure 9 shows the
regulated output dc-link voltage. It is clear from Figures 8 and 9 that by using 110 V as input, the
proposed control algorithm has accurately regulated and maintained the output dc-link voltage
at desired level of 100 V. At the same time, by referring to Figure 10, it can be observed that a
sinusoidal input current of phase A with minimum switching noises and total harmonic distortion
(THD=3.36%) and a unity power factor (i_q=0) is produced. Finally, Figure 11 shows the output
dc current with 0.01 ripples, this value of ripples do not cause any harms to the battery in case
of charging a battery of electric bus. Therefore, it is clear that the proposed control algorithm
performs effectively in providing a constant output voltage and current for battery charging with
minimal disturbance to the operating power system.
Figure 1. Reference voltage of phase A. Figure 2. Input voltage (Vin= 110 V) of
phase A.
Figure 3. Outputdc-link voltage with reference
voltage(𝑉𝑑𝑐 _𝑟𝑒𝑓 =100 V).
Figure 4. Input current of phase A.
Figure 5. Outputdc current(Vdc_ref =100 V, Rload =250Ω).

1441
Figure 12 and Figure 13 show the simulation result of the input voltage and current of
the proposed circuit which can fulfill the requirements of third level charging for Electric
Bus/Lorry (fast charging).. The physical aspect of these results show almost pure sinusoidal
waveform of the input voltage and the THD for the input current is recorded at 4.11 %. Next,
Figure 14 demonstrates how the proposed control system can effectively present an accurate
regulation of dc-link voltage at the dc reference voltage of 650 V. By using three-phase input
supply voltage of 700 V and resistive load of 250 Ω, regulated dc voltage as shown in
Figure 14 (a) and dc current as shown in Figure 14 (b)
Figure 6. Input voltage (700V) of phase A
.
Figure 7. Input current of phase A.
Figure 8. The dcoutput of VOC: (a) regulated voltage and (b) current respectively.
5. Experimental Results
Laboratory prototype is developed to validate practically effectiveness of the proposed
VOC algorithm. Experimental setup for the proposed rectifier with VOCalgorithm is shown in
Figure 15. Meanwhile, Figure 16 shows the VOC algorithm which is downloaded into
a TMS320F28335 digital signal processor (DSP) from TexasInstruments (TI). The design and

 ISSN: 1693-6930
1442
test parameters applied for experiment work is similar to the one applied in simulation work, as
summarized in Table 1.
The performance demonstrated by the proposed control algorithm in response to step
changes of dc voltage reference is shown in Figures 17and 18. According to these figures, the
ac current is working in the samephase with the ac voltage. Besides, it achieves almost unity
power factor rectifier and thus fulfilling the requirements of the battery charger. Meanwhile, the
output voltage and current are constant, and thus the battery charging of electric vehicle (EV) is
stable.
Figure 9. Experimental setup for rectifier with VOC control
Figure 10. VOC control algorithm for DSP implementation

1443
Figure 17. Input voltage of phase A(CH1),
output dc voltage (CH2) and input current of
phase A (CH3)
Figure 18. Reference voltage of phase A
(CH1), input voltage of phase A (CH2), output
dc-link voltage (CH4) and output dc voltage
(CH3)
6. Conclusion
This paper has clearly demonstratedaVOC control algorithm for effective operation of
three-phase PWM rectifier in generating constant output dc voltage and current. From the
findings, it is clear that the control algorithm accurately regulatesthe dc-link voltage at desired
level and at thesame time, it ensures sinusoidal input current with minimumswitching ripples and
distortions, where THD of the input current is maintained at 4.11 %with an almost unity power
factor.
7. Highlights:
a. This paper addresses the design and development of vehicle (EV) charger which is
appropriate Level 3 charging.
b. VOC control algorithm and SPWM switching algorithm are applied to effectively control the
charging process. The algorithms are successfully implemented digitally on TMS320F28335
digital signal processor (DSP) board.
c. The simulation and experimental results demonstrated effectiveness of the proposed
algorithms in providing constant DC output voltage and current for stable and secure battery
charging.
d. The power factor of the input is almost unity, and the total harmonic distortion (THD) for the
input current is less than 5 %.The overall efficiency based on simulation results is more than
97%.
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Design and Experimental Results of Universal Electric Vehicle Charger Using DSP

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Design and Experimental Results of Universal Electric Vehicle Charger Using DSP