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MODELING, SIMULATION AND DESIGN OF AN IMPROVED HIGH POWER
FACTOR BRIDGELESS SEPIC CONVERTER
IZNI BINTI MUSTAFAR
UNIVERSITI TEKNOLOGI MALAYSIA
MODELING, SIMULATION AND DESIGN OF AN IMPROVED HIGH POWER
FACTOR BRIDGELESS SEPIC CONVERTER
IZNI BINTI MUSTAFAR
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Electrical – Power)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
JANUARY 2015
iii
ACKNOWLEDGEMENT
First and foremost, “ Syukur Alhamdulillah” to Allah, the Most Gracious and
Most Merciful for ensuring myself to be healthy to carry out my study and to complete
this project.
Secondly, I would like to express my warmest gratitude to my supervisor, Dr.
Mohd Rodhi bin Sahid who has provided immeasurable support and guidance toward
the completion of my research project. His ideas and suggestions is much appreciated
My sincere appreciation also goes to my parents who has been so supportive
in all years. Thanks for giving me continuous encouragement, love and emotional
supports that they had given to me.
I also would like to give a special thanks to Dr. Naziha, Ika, Tie, Kong, Kak
Mira and Abdul Rahman for helping me throughout this procces. Last but not least I
would like to gratefully thank to all my lecturer and all my friends who had given me
helps technically and mentally throughout my journey in completing my project.
Thank You.
Wassalam
iv
ABSTRACT
Switch Mode Power Supply (SMPS) designs are normally have a power
quality issues due to the harmonic distortion produce in the system. Therefore it is
essential to incorporate a power factor correction (PFC) circuit in SMPS design.
Although, the boost converter is more popular to use with PFC circuit, SEPIC
converter can produce an input current with lower ripple value. However, since it
involved with 4 energy storage component, a bridgeless SEPIC converter were
used as the bridgeless circuit reduce the component conducted in ech switching
cycle compared to conventional SEPIC. Therefore this thesis focuses on designing
the bridgeless PFC SEPIC converter that operate in CCM with two types of
controller. The controllers are Average Current Control Mode and Peak Current
Control Mode. Simulation of the bridgeless SEPIC PFC circuit were done using
MATLAB Simulink software. The results show that the Average Current Mode
Control produce high power factor with low harmonic distortion compared to Peak
Current Mode Control. At the end of this thesis, a suitable recommendation and
suggestion were made to improve the project design.
v
ABSTRAK
Rekaan Suis Mod Bekalan Kuasa (SMPS) biasanya mempunyai isu dalam
membekalkan kuasa yg berkualiti kerana ia sering menghasilkan herotan harmonik
di dalam sistem. Oleh itu, adalh penting untuk mengaplikasikan litar pembetulan
faktor kuasa (PFC) di dalam rekaan SMPS. Walaupun penukar Boost adalah lebih
popular dalam proses mengimplemtasikan litar PFC, namun penukar SEPIC boleh
menghasilkan arus input dengan nilai riak yang lebih rendah. Walaubagaimanapun,
oleh kerana penukar SEPIC terdiri daripada 4 komponen pemyimpan tenaga,
penukar SEPIC tanpa jambatan telah digunakan kerana didalam setiap kitaran litar,
komponen yg digunakan adalah lebih sedikit. Dengan itu, tesis ini tertumpu kepada
merekabentuk penukar PFC SEPIC tanpa jambatan yg beroperasi dalam keadaan
arus berterusan (SSM) dengan due jenis pengawal litar. Jenis-jenis pengawal litar
adalah kawalan secara purata dan kawalan secara puncak. Simulasi litar SEPIC
PFC tanpa jambatan telah dijalankan mengggunakan perisian MATLAB Simulink.
Hasil kajian menunjukkan bahawa faktor kuasa yang tinggi hasil daripada
penggunaan kawalan secara purata dengan herotan harmonik yang rendah.
vi
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
ACKNOWLEDGEMENT iii
ABSTRACT iv
ABSTRAK v
TABLE OF CONTENTS vi
LIST OF TABLES ix
LIST OF FIGURES x
LIST OF ABBREVIATIONS xiii
LIST OF SYMBOLS xiv
LIST OF APPENDICES xv
1 INTRODUCTION 1
1.1 Introduction and Background 1
1.2 Problem Statements 2
1.3 Objectives of Project 3
1.4 Scope of Project
3
2 LITERATURE REVIEW 5
2.1 Conventional Sepic Converter 5
2.1.1 Operation of SEPIC Converter 6
2.1.2 Circuit Operation for SEPIC PFC Circuit
with Full-Bridge Rectifier
7
vii
2.1.2.1 SEPIC PFC Converter Operation
Mode
7
2.2 Bridgeless SEPIC PFC Circuit 10
2.3 Controller Design 12
2.3.1 Average Current Mode Control 13
2.3.2 Peak Current Mode Control 14
2.4 State Space Averaged Model for SEPIC
Converter
16
3 METHODOLOGY 20
3.1 Introduction 20
3.2 Bridgeless PFC SEPIC Converter Design
Specification
23
3.3 Average Current Mode Conntrol Design 24
3.3.1 Multiplication and Dividing Block 25
3.3.2 PI Controller as Current Compensator 26
3.3.3 PI Controller as Voltage Compensator 28
3.4 Peak Current Mode Control 30
3.4.1 PI Controller for Voltage Compensator 30
3.5 True Power Factor
32
4 RESULT AND DISCUSSION 35
4.1 Open Loop System 35
4.2 Closed Loop System 36
4.2.1 Average Current Mode Control Scheme 37
4.2.2 Peak Current Mode Control Scheme 41
4.3 True Power Factor
46
5 CONCLUSION AND RECOMMENDATION 48
5.1 Conclusion 48
5.2 Recommendation 49
viii
REFERENCES 50
Appendix A 53
ix
LIST OF TABLES
TABLE NO. TITLE PAGE
4.1 The power factor value measured for input
voltage of 240V
46
4.2 The power factor value measured for input
voltage of 115V
47
x
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Operation of SEPIC converter 6
2.2 Circuit Operation for SEPIC PFC Circuit with Full-Bridge
Rectifier
7
2.3 Bridgeless SEPIC PFC Circuit[10] 10
2.4 Bridgeless SEPIC PFC Circuit during Positive Half Line
Cycle[10]
11
2.5 Bridgeless SEPIC PFC Circuit during Negative Half Line
Cycle[10]
11
2.6 Block Diagram for General Controller Design 12
2.7 Block Diagram for Average Current Mode Control 13
2.8 Multiplication and Dividing Block 14
2.9 Block Diagram for Average Current Mode Control 15
3.1 Flow Chart of Methodology Process 21
3.2 The open loop PFC SEPIC Converter simulated using
Matlab/Simulink
22
3.3 Simulation of SEPIC Converter 22
3.4 PFC SEPIC using Average Mode Current Control 24
3.5 The Multiplication and Dividing Block 25
3.6 The PI controller for Current Compensator 26
3.7 Bode Diagram for Current Compensator 27
3.8 Tracking Signal of PI controller 27
xi
3.9 The PI controller for Voltage Compensator 28
3.10 Bode Diagram for Voltage Compensator 29
3.11 Tracking Signal of PI controller 29
3.12 SEPIC PFC using Peak Mode Current Control 30
3.13 The PI controller for Voltage Compensator 31
3.14 Bode Diagram for Voltage Compensator 32
3.15 Displament PF block in Matlab Simulink 33
3.16 Distortion PF block in Matlab Simulink 33
4.1 Open Loop Design for SEPIC PFC Converter 35
4.2 PFC SEPIC using Average Mode Current Control 36
4.3 PFC SEPIC using Peak Mode Current Control 36
4.4 Voltage Output vs. Time for Vin =240V, which the load
changed from 240 W to 120 W.
38
4.5 Voltage Output vs. Time for Vin =115V, which the load
changed from 240 W to 120 W.
38
4.6 Inductor Current waveform for Vin = 240 V 39
4.7 Inductor Current waveform for Vin = 115 V 39
4.8 Inductor Current vs. Time for Vin = 240 V with load
variation from 240 W to 120 W
40
4.9 Inductor Current vs. Time for Vin = 115 V with load
variation from 240 W to 120 W
40
4.10 Input Current in Phase with Input Voltage 41
4.11 Voltage Output vs. Time for Vin =240V, which the load
changed from 240 W to 120 W
42
4.12 Voltage Output vs. Time for Vin =115V, which the load
changed from 240 W to 120 W
42
4.13 Inductor Current waveform for Vin = 240 V 43
4.14 Inductor Current waveform for Vin = 115 V 43
xii
4.15 Inductor Current vs. Time for Vin = 240 V with with load
variation from 240 W to 120 W
44
4.16 Inductor Current vs. Time for Vin = 115 V with with load
variation from 240 W to 120 W
45
4.17 Input Current in Phase with Input Voltage 45
xiii
LIST OF ABBREVIATIONS
AC - Asychrounous Current
DC - Direct Current
PFC - Power Factor Correction
SMPS - Switch Mode Power Supplies
SEPIC - Single-Ended Primary Inductor Converter
CCM - Continuous Conduction Mode
MDB - Multiplication And Dividing Block
PF - Power Factor
THD - Total Harmonic Distortion
DF - Distortion Power Factor
PWM - Pulse Width Modulation
xiv
LIST OF SYMBOLS
VL - Voltage across inductor
VCS - Voltage across series capacitor
VCO - Voltage across capacitor output
S - Switch
Q - Power Switch
D - duty ratio
L - inductance
C - capacitance
R - load
D - diode
xv
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Calculation of Transfer Function 54
CHAPTER 1
INTRODUCTION
1.1 Introduction and Background
Nowadays, the input of power supplies often to be an AC sources, and therefore
the use of full wave rectifier is very important to convert the AC input to a DC output
since many of electronic equipment use DC voltage as a power supplies. With the
extensive use of electrical and electronic equipment, there is a large demand for a
power supplies that draw current with low harmonic content and also have high power
factor value [1].
Thus, it can be said that the AC mains utility supply is supposed to be free from
high voltage spikes and harmonics. However with the use of rectifier, the resulting
input current is highly non-sinusoidal which produce a high value of total harmonic
distortion which leads to a disturbance that can have a bad impact on electrical and
electronic circuit [2].
2
The large value of total harmonic distortion can be mitigated using power
factor correction (PFC) circuit. There are two types of power factor correction circuits,
which are active PFC and passive PFC [3]. Passive PFC consists of reactive elements
that will correct output impedance at a given frequency [3]. Thus, it will only mitigate
at one specific frequency and if the disturbance occurs out of the expected range, the
harmonic distortion will not be corrected [3]. Differ from passive PFC, the active PFC
circuit have been designed to detects the actual output impedance of the circuit and
dynamically re-adjust the power factor [3]. As a result, the active PFC can mitigate
the harmonic better than the passive PFC circuit.
Therefore, the active PFC circuits are preferable compared to the passive PFC
circuit. Most active PFC circuit consists of a front-end full bridge rectifier followed
with a DC to DC converter. Apart from that since the full bridge rectifier contribute
to a high value of conduction losses, therefore the efficiency value is decrease. Hence,
there are lots of effort to design and control the bridgeless power factor correction
circuit in order to cater this issue. Thus, the bridgeless PFC circuit will be studied in
this project and discussed in this thesis.
1.2 Problem Statements
Switch Mode Power Supplies (SMPS) is an electronic device that is widely use
to convert electrical power. However it have harmonic distortions produce by main
switch and leads to a disturbance. For this reason, it is desirable to design an SMPS
with a unity power factor. In order to solve this problem, a power factor correction
circuit is incorporated in the converter system.
There are several well-known topologies for PFC converter such as buck,
boost and buck-boost converter. However a SEPIC converter is less popular topology
3
for PFC converter design due to the complex control part where it reaches the 4th order
[4].
In spite of that, the PFC SEPIC converter offer an advantage compared to 2nd
order converter which it have two inductors on the same wound [4]. Consequently, it
has a lower input current ripple compared to other converter topology. Thus, the
bridgeless SEPIC PFC converter with a closed-loop control will be studied in this
project to observe the total harmonic produce by SEPIC PFC circuit [5].
1.3 Objectives of Project
There are two objectives in this project, which are as follow:
1. To study and design bridgeless SEPIC power factor circuit (PFC)
converter with a close loop controller in Continuous Conduction Mode
(CCM).
2. To compare the performance of controller by using two methods which are
the average mode control method and peak mode control method.
1.4 Scope of Project
The scopes for this project are as follows:
1. Study on the conventional and bridgeless SEPIC PFC converter.
4
2. Understand the performance of controller especially the current mode
control
3. Design the closed loop compensator such that the converter operates
within the desired operating condition using Matlab/Simulink.
4. Identify the effect and performance of bridgeless SEPIC PFC converter
with two commonly used current control method.
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Mc Graw Hill.
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Improving Power Factor Correction In Distributed Power Supply Systems
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Electronics Specialists Conference. 24-27 Jun, Cambridge, MA: IEEE, 780-
791
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Computation of Power, Energy, Information and Communication (ICCPEIC)
Conference. 17-18 April, Chennai. 28-30.
56
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Proceedings of the Telecommunications Energy Conference. 14-18
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