AN OPTIMIZED DC-DC CONVERTER FOR ELECTRIC VEHICLE … · 2017-09-25 · KY Boost Converter, a modern invention in the field of non-isolated DC-DC boost converter which is identified

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 9, September 2017, pp. 173–182, Article ID: IJMET_08_09_018

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=9

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

AN OPTIMIZED DC-DC CONVERTER FOR

ELECTRIC VEHICLE APPLICATION

Prithivi K and Sathyapriya M

Department of Electrical and Electronics Engineering,

Kongu Engineering College, Tamilnadu, India

Ashok Kumar L

Department of Electrical and Electronics Engineering,

PSG College of Technology, Tamilnadu, India

ABSTRACT:

KY Boost Converter, a modern invention in the field of non-isolated DC-DC boost

converter which is identified for minimum voltage ripple. KY Boost Converter is the

combination of KY Converter and traditional Boost Converter. Such a converter has

continuous input and output inductor current, different from the traditional boost

converter. And hence this converter is very suitable for very low-ripple applications.

The open loop controller and Optimization techniques based closed loop controller

are designed in MATLAB/Simulink model and the simulated results show the high

output voltage ripple reduction from open loop controller to closed loop controller

using various optimization techniques.

Keywords: KY Boost converter, Optimization techniques, Output Voltage Ripple (OVR)

reduction

Cite this Article: Prithivi K, Sathyapriya M and Ashok Kumar L, An Optimized DC-

DC Converter for Electric Vehicle Application, International Journal of Mechanical

Engineering and Technology 8(9), 2017, pp. 173–182.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=9

1. INTRODUCTION

For the function of the power supply using the low voltage battery such as radio-frequency

(RF) amplifier, audio amplifier, often need very high voltage to obtain enough output power.

This is done by boosting the minimum voltage to the required high voltage. For such

applications, the output voltage ripple must be taken into account purposefully. Regarding the

conventional boost converter, their output currents are pulsating; thereby the corresponding

output voltage ripple tends to be large. As generally approved, to overcome this problem, one

way is the usage of low equivalent series resistance (ESR). In [1], the interleaved control

scheme is employed in the dual buck-boost converters. In the literature [2]-[4], the voltage-lift

technique is utilized to boost the output voltage. But these converters [2]-[4] have one right -

Prithivi K, Sathyapriya M and Ashok Kumar L

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half plane zero in CCM mode. So it is not easy to achieve required boosted output voltage.

And hence the KY boost converter [5] is presented to overcome this problem. In the literature

[6], FUZZY logic controller is used to reduce the output voltage ripple of KY boost converter.

The detailed illustration of the proposed converter is described herein, along with some

experimental results using various optimization techniques to justify the effectiveness of such

a converter and the effectiveness of the optimization techniques also justified.

2. KY BOOST CONVERTER

Fig. 1 shows the proposed positive-voltage KY boost converter composed of the KY

converter combined with the traditional boost converter, which is described as follows. The

KY converter consists of the switches�� an���, the diod���, the energy-transferring

capacito�, the output inductor�� and the output capacito�. The input of the KY

converter is retrieved by the buffer capacitor . On the other hand, the traditional boost

converter consists of the switches�� and��, the input inductor��. The output of the

conventional boost converter is replaced by the buffer capacito . The buffer capacitor

is a buffer between the KY converter and the traditional boost converter.

Figure 1 KY Boost Converter

Mode 1 operation of KY boost converter

Figure 2 Power flow of Mode 1 operation

In Fig. 2, ��is turned off and�� is turned on. In this case, the negative terminal of � is

pulled to the ground and hence �� is forward biased and turned on. During this mode, is

discharged whereas � is charged. Therefore, the voltage across �� is��, thereby causing �� to

be magnetized, whereas the voltage across �� is �� subtracted from���, thereby causing �� to

be demagnetized. Also, the current flowing through � is equal to ��� minus the current

flowing through��. And hence, the corresponding differential equations are

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�� ������ � ��� (1)

�� ����� � ��� � �� (2)

������ � ���� � ��� (3)

� ����� � ��� � �� � (4)

Mode 2 operation of KY boost converter

Figure 3 Power flow of Mode 2 operation

In Fig. 3, �� is turned on and �� is turned off. In this case, �� is in the on-state and hence

�� is reverse biased and turned off. During this mode, is charged whereas � is

discharged. Therefore, the voltage across �� is �� subtracted from��, thereby causing �� to

be demagnetized, whereas the voltage across �� is subtracted from sum of �� and���,

thereby causing �� to be magnetized. Also, the current flowing through � is equal to

���minus the current flowing through���. And hence, the corresponding differential equations

are

�� ������ � �� � �� (5)

�� ������ � 2�� � �� (6)

������ � ��� � ��� (7)

� ����� � ��� � �� � (8)

The average equations which are obtained from equation (1) to equation (8),�� ������ � "��# � "1 � �#"�% # (9)

� ����� � "���# � &�� �' (10)

�� ������ � "2 � �#"�� # � "��# (11)

�"���#�� � "����# ( "1 � �#"���# � �"���# (12)

)*)+ �

,&-.// '"012#3,4&-.// '"012#5016"�47#4"012#3

(13)

Prithivi K, Sathyapriya M and Ashok Kumar L

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According to the small-ripple approximation and the voltage-second balance, the voltage

ratio can be obtained to be

8�86 �

�47�47 (14)

Where,

d = Duty cycle,

9:= Output voltage in Volts

9; = Input voltage in Volts.

KY Boost Converter Specifications

Table 1 specifications adopted for KY boost converter

Parameter Symbol Value Unit

Input voltage V0 12 V

Rated output voltage V= 36 V

Rated load current i� 10.36 A

Output inductance L= 3.623 mH

Buffer capacitance CA 31.24 mF

Energy transferring

capacitor CB 62.2 mF

Output capacitance C� 470 μF

Switching

frequency fD 195 kHz

Load Separately

excited motor 0.5 hp

Input inductance L0 0.402 mH

3. SIMULINK MODELING OF KY BOOST CONVERTER

The KY boost converter realized in Simulink model is represented by Fig. 4. in which

switches are represented by �� and ��with interrelated body diodes ��and �� . Li represents

input inductor; �� represent output inductor; represent buffer capacitance; � represent

energy transferring capacitor; � is output diode; �� is forward diode. The switching signal is

fed through the connector M and the output voltage taken to Matlab workspace by

connector ��.

3.1 Modeling of fuzzy

Fuzzy controller is formed to diminish the output voltage ripple of the KY boost converter

which is shown in Fig. 5. The input to the Fuzzy controller is error (e) and change in error

(ce), where the error (e) is the deviation of output voltage �� and reference voltage �EFG. The

output of Fuzzy controller is duty cycle (d). To generate the switching signal for KY boost

converter, the duty cycle (d) is given to a PWM generator. Fig. 5 shows the Simulink model

of the proposed Fuzzy controller for KY boost converter which subsists of Fuzzy controller,

PWM generator block with KY boost converter block with reference output voltage of 36 V.

The switching frequency is generated by the PWM generator block is 195 kHz which is fed to

the KY boost converter.

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3.2 Modeling of PSO

Particle Swarm Optimization (PSO) comes from the research on the bird and fish flock

progress behavior which is used to find the global minimum of the proposed objective

function [21]. In this method a swarm of particles describe a candidate solution move in the

search space. Each particle position represents the objective function which is depending on

the variables defined by the optimization problem. It is very simple and easy to implement. It

does not require any specific information about the converter model as well as the system

parameters. And the calculation is very simple but the steps for the calculation are high. It is

used in travelling salesman problem, maximum power point tracking in solar panel,

optimization of hydrocarbon field development planning.

3.3 PSO Controller Simulink Modeling

The aim of the present work is to find out the optimized vector of the switching angles, for

which the ripple components are limited to acceptable low level or even to be eliminated. On

the other side the obtained average value has to be equal or closer to the reference or desired

output voltage. To fulfill these requirements an objective function which has to be minimized

is proposed as follows:

f(d) = e (15)

Where,

e = �EFG - �HIJ (16)

�EFG = 36 (17)

This function contains two terms, the error between the desired average voltage and the

obtained output average voltage and the output voltage ripple which is to be eliminated. For

reducing the output voltage ripple the output voltage should satisfy the following Constrain.

d = 0 to 1 (18)

3.4 Modeling of ACO

Ant Colony Optimization is a technique for solving problems which can be expressed as

finding good paths through graphs, Ant Colony is swarm of ants. Each ant tries to find a route

between its nest and a food source. The first ant search randomly until it finds the food source,

and then it returns to the nest, laying a pheromone trail. Other ants follow one of the paths at

random, also set the position of pheromone trails. Since the ants on the shortest path lay trails

faster, this path gets supplement with more pheromone, making it more appealing to future

ants. The ants become increasing likely to follow the shortened path since it is constantly

reinforced with a larger amount of pheromones. The pheromone trails of the longer paths

vaporize. When one ant finds a good path from the colony to a food source, other ants are

more likely to follow that good path, and positive feedback eventually leads to all the ants

following a single path. It is used in Traveling salesman problem, Vehicle routing (school

buses, deliveries, waste collection), Tracking maximum power in solar panel.

ACO Controller Simulink Modeling

The aim of the work is to find out the switching pulse for the switches for reducing the output

voltage ripple and increasing the input voltage to the required voltage range. To fulfill these

requirements an objective function which has to be minimized is proposed as follows:

f(d) = e (15)

Where,

e = �EFG - �HIJ (16)

Prithivi K, Sathyapriya M and Ashok Kumar L

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�EFG = 36 (17)

4. SIMULATION RESULTS AND DISCUSSION

The simulated results of the KY boost converter with input voltage 12V and the rated output

voltage of 36V for a separately excited motor load is simulated with Matlab/Simulink R2013a

is shown by the following figures Fig. 8, Fig.9, Fig. 10 and Fig11.

Fig.8 shows the output voltage for 12V input voltage in open loop condition of KY boost

converter. It clearly shows that the output voltage ripple for an output voltage of 32.18V in

open loop condition is about 1.18V.

Fig. 9 shows the output voltage for 12V input voltage in closed loop condition of KY

boost converter using FUZZY controller. It clearly shows that the voltage ripple for an output

voltage of 36V is about 0.54V.

Fig. 10 shows the output voltage for 12V input voltage in closed loop condition of KY

boost converter using PSO based controller. It clearly shows that the voltage ripple for an

output voltage of 36V is about 0.275V.

Fig. 11 shows the output voltage for 12V input voltage in closed loop condition of KY

boost converter using ACO based controller. It clearly shows that the voltage ripple for an

output voltage of 36V is about 0.14V.

Table 2 comparison of existing and proposed technique output

System type

(Open/Closed loop) Output voltage

Output voltage

ripple

Open loop system 32.18V 1.18V

Closed loop using FUZZY 36V 0.54V

Closed loop using PSO 36V 0.275V

Closed loop using ACO 36V 0.14V

Figure 4 KY boost Converter Simulink Model

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Figure 5 KY Fuzzy Controller Simulink Model

Figure 6 KY PSO Controller Simulink Model

Figure 7 KY ACO Controller Simulink Model

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Figure 8 Output Voltage Waveform of open loop KY Boost Converter

Figure 9 Output Voltage Waveform of closed loop KY Boost Converter using FUZZY logic

controller

Figure 10 Output Voltage Waveform of closed loop KY Boost Converter using PSO based controller

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Figure 11 Output Voltage Waveform of closed loop KY Boost Converter using ACO based controller

5. CONCLUSION

The problem of the KY Boost converter output voltage ripple is presented in this paper.

Various optimization techniques are used to solve this problem using an objective function.

This objective function is containing a defined number of switching angles pattern depending

on the degree of ripple reduction. The resulting output values of the closed loop ACO

Controller are compared with the closed loop PSO controller, closed loop FUZZY controller

and open loop system. The reduction of output voltage ripple is proved by the simulation

results.

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