MULTIPULSE AC-DC CONVERTERS FOR POWER QUALITY IMPROVEMENT
By
SANJAY GAIROLA Department of Electrical Engineering
Submitted In fulfillment of the requirements of the degree of
DOCTOR OF. PHILOSOPHY
to the
INDIAN INSTITUTE OF TECHNOLOGY, DELHI
JUNE 2008
(Prof. BRIM SINGH) Department of Electrical Engineering Indian Institute of Technology Delhi New Delhi — 110 016, INDIA
CERTIFICATE
It is certified that the thesis entitled "Multipulse AC-DC Converters for Power
Quality Improvement," being submitted by Mr. Sanjay Gairola for the award of the
degree of Doctor of Philosophy in the Department of Electrical Engineering, Indian
Institute of Technology Delhi, is a record of the student's own work carried out by him
under my supervision and guidance. The matter embodied in this thesis has not been
submitted for the award of any other degree or diploma.
Dated: -,1i)„7-te i , 2008
ACKNOWLEDGEMENTS I wish to express profound gratitude and indebt ness to my supervisor Prof. Bhim
Singh for providing invaluable guidance, support and encouragement during the course
of this research work. His sagacity and vision have played a very important role, not only
in guiding me throughout this study but also teaching me lessons of happy life. I am also
grateful to the members of the research committee, namely, Prof. P. R. Bijwe, Prof. T.
S. Bhatti and Dr. (Mrs.) G. Bhuvaneshwari for their valuable suggestions and critical
comments throughout the course of this research work.
I am thankful to Mr. Gurucharan Singh, Mr. Meharban Singh, Mr. Srichand,
Mr. Jagbeer Singh and Mr. Puran Singh and other staff members of the P.G. Machines
and Drives Laboratory, at I.I.T. Delhi for their sustained help and cooperation for
experimentation work. Mr. Jagbeer Singh had been very instrumental in fabrication of
number of transformers that have been used in different configurations of converters.
I extend my special thanks to the fellow research scholars Mr. Gaurav Kasal, Mr.
Madhan Mohan, Mr. Sanjeev Singh, Mr. Jai Prakash, Mr. Perumal, Mr. Sudhakar
and Ms. Kiranmayi. My thanks are also due to Dr. Sanjeet Dwivedi, Dr. Vipin Garg,
Dr. Vishal Verma, Dr. Mukesh Pathak, Dr. Sushma Gupta, Dr. S. Ghatak
Choudhary and Mr.Sachin Jain who have been with me for some time during this
period and have shown exemplary attitude and dedication for research. I am also thankful
to M. Tech Scholars Mr. Devendra Goyal, Mr. Ravi, Mr. Praveen, Mr. Jitendra
Solanki, and Mr. Hemanth for their help and cooperation.
The study leave provided by the parent institute, Krishna Institute of Engineering
and Technology(KIET), Ghaziabad (U.P.) is also gratefully acknowledged. I must
thank Dr. Ajay Sharma, Director General of K.I.E.T., for his appreciation and keen
iii
interest in my research activities. My thanks are also due to Galgotias College of
Engineering and Technology (GCET), Greater Noida, for appreciation of my research
work.
I am indebted for the encouragement and support received from my parents, my
sister Suman, brothers Vinod and Ashok. My thanks are also due to my brother in law,
Mr. Mukesh. I gratefully acknowledge the unconditional support of my wife Poonam
and thank her for all the patience, cooperation and help, without which this work would
not have been possible. Finally, I thank my daughter Divya, and son Megh who missed
me a lot during this period, their sacrifice is unexplainable in words.
Once again, I bow to all those who directly or indirectly helped me but their name is
missed.
l'i)ie.11, 2008
(Sanjay Gairola)
New Delhi
2003EEZ0012
iv
ABSTRACT The revolution in power electronics has opened an era for widespread use of power
converters of different power rating from few Watts to Mega-Watts. AC-DC converters
are most widely used power converters as the distributed electric power is AC supply,
while the applications based on DC supply as well as variable frequency AC supply, need
conversion of AC supply into DC supply.
Large current harmonics and poor power factor in the utility interface are common
problems in AC-DC converters. These AC-DC converters are used invariably at the front
end in numerous applications which may or may not be electrically isolated from the AC
supply system depending on the rating and nature of the load and also the prevalent
`Standards' requirements. The applications such as electrochemical, electrometallurgical
and electrical heating processes, HVDC systems, adjustable speed drives, battery
charging, aerospace and naval equipments, uninterruptible power supplies (UPS) etc., use
AC-DC conversion at the front end. These processing industries and adjustable speed
drives are main applications where large amount of power is involved in AC-DC
converters. These AC-DC converters are generally diode based, thyristor based or self
commutating device based converters depending on applications, size and cost.
The simplicity in design and popularity of AC-DC converters have been considered as
the reasons for them to be most neglected converters. The wide spread use of AC-DC
converters for various applications has resulted in power pollution leading to failure of
sensitive equipments, reduced efficiency, etc. This has led to development of power
quality standards and hence attracted attention of many researchers for improving the
power quality at AC mains. This research work aims at classifying and investigating
different multipulse AC-DC converters that employ either diodes or thyristors.
v
To comply with the stringent harmonic requirements set by various standards such as
IEEE-519, 1992, three-phase multipulse AC-DC converters are becoming popular in
number of applications. These multipulse converters consist of mainly bridge and full-
wave rectifiers (controlled or uncontrolled) for AC-DC conversion. The main feature of „I
multi-pulse AC-DC converters is its ability to reduce current harmonics distortion which
is synonymous to power quality improvement. In multipulse AC-DC converters the
number of pulses (voltage ripples at output of AC-DC converters in one cycle of AC
supply voltage or steps in the current at input of AC mains) is increased by using phase
staggering (or phase shifting), multiphase (or phase multiplication), DC ripple-reinjection
(or pulse multiplication) and hybrid of these techniques. The application of multipulse
techniques in AC-DC converters also results in eliminating and reducing the need of
tuned passive filters, active filters and hybrid filters, which are bulky and lossy, complex
and expensive.
This research work aims at employing multipulse techniques for mitigating the power
quality problems at the AC mains in AC-DC converters. The investigations on different
types of multipulse AC-DC converters have been carried out covering a wide range of
applications that use three phase AC supply at front end for converting it to DC power,
These converters involve use of autowound or double wound transformers (windings
connected in configurations such as star, delta, zigzag, polygon, fork, T, hexagon, etc.),
DC interphase reactors, line interphase reactors, zero-sequence blocking transformers
(ZSBT), diodes or thyristors connected in full-wave and bridge configurations. For
visualizing the different advantages of conventional and modern AC-DC converters, the
modeling and simulation of these converters are carried out in MATLAB using its
Simulink and Power System Blockset (PSB) toolboxes. The main emphasis of these
vi
investigations has been on compactness of configurations, simplicity and reduction in
ratings of components to reduce the overall cost of these multipulse AC-DC converters.
With a focus on these aspects, classification of AC-DC converters is made and these
converters have been designed and developed in each category for mitigating power
quality problems. The detailed investigations are aimed to provide various power quality
mitigating options to design engineers for a number of applications employing three-
phase AC-DC converters.
In this work, AC-DC converters are mainly classified on the basis of transformer
configuration, and type of diode and thyristor arrangement used. This has led to
classification as isolated and non-isolated, controlled and uncontrolled, full-wave and
bridge type AC-DC converters. The detailed investigation in these categories is carried
out based on the different pulse number configurations and technique employed in them.
The classification has led to formation of some new AC-DC converter configurations that
are investigated for their power quality improvement capability.
A high speed digital processor namely dSPACE DS1104, that has Texas instruments
DSP TMS320F240 with it as slave DSP, is used to implement a voltage source inverter
fed variable frequency induction motor drive (VFIMD) system as a load on three-phase
AC-DC converters. Conventionally a six-pulse diode bridge AC-DC converter is used at
the front end of this VFIMD system to demonstrate the power quality issues. In this
investigation different multipulse AC-DC converters are used at its front end to validate
the power quality improvement. This processor has reduced the hardware requirement for
control of the drive system and given flexibility for quick implementation.
The thyristor controllers are also developed for non-isolated and isolated AC-DC
converters. These bi-directional power flow AC-DC converters are designed and
vii
simulated for adjustable speed drive systems. Moreover, for high power applications the
investigations are carried out using specific load models to demonstrate power quality
improvements in multipulse AC-DC converters at varying firing angles.
It is observed that non-isolated full-wave converters, which are not reported anywhere
in the literature, have specific advantages in certain applications. These are designed and
developed for multiphase AC-DC conversion to be implemented in low-voltage
applications. Altogether three new classes of non-isolated full-wave AC-DC converters
based on star, zigzag and T-connected transformers are designed and modeled and their
performance is evaluated in terms of power quality indices. The laboratory prototypes of
some of these full-wave AC-DC converters are also developed to validate the design and
model of these new converters.
Isolated full-wave AC-DC converters are useful for very low voltage and high current
applications. These full-wave isolated converters are investigated in this work for their
improved power quality performance and new configurations based on fork, zigzag and T
connections are developed to validate their design and simulation models.
The unconventional pulse number AC-DC converters are also investigated that result
in an improvement in power quality and have less number of devices. The
unconventional pulse number AC-DC converters having pulse number of 20, 28, 40, 44,
56 and 88 are designed, modeled and developed to improve the power quality at AC
mains.
It is observed in this research work that the power quality indices in 12-pulse isolated
AC-DC converters are within IEEE standard limits only in certain configurations. The
configurations that do not meet the standard requirements can be modified to higher pulse
number by DC ripple re-injection which needs few additional components to improve
viii
power quality. Accordingly different configurations employing ripple re-injection are
designed and developed for various uncontrolled and controlled AC-DC converters. It is
observed that these controlled converters having pulse number of 24 or 36 need a very
low rating high-pass filter for power factor improvement over wide range of firing angle.
These configurations and techniques have resulted in improved power quality indices
with overall reduced rating and reduction in number of components used in front end
isolated/non-isolated and controlled/uncontrolled AC-DC converters involving full-wave/
bridge arrangement of semiconductor devices to feed various DC loads.
ix
TABLE OF CONTENTS
Page No. Certificate i Acknowledgements iii Abstract v Table of Contents xi List of Figures xxiii List of Tables lvii List of Symbols lxiii
CHAPTER I INTRODUCTION 1-20 1.1 General
1.1.1 Features of Multipulse AC-DC Converters l 1.1.2 Problems in AC-DC Converters 2
1.2 State of Art on Multipulse AC-DC Converters 6 1.3 Power Quality Aspects and Standards 9
1.3.1 Power Quality Considerations 9 1.3.2 Power Quality Standards 11
1.4 Objectives and Scope of the Study 12 1.4.1 Analysis, Design and Development of Non-Isolated
Uncontrolled Multipulse AC-DC Converters 13 1.4.2 Analysis, Design and Development of Isolated Uncontrolled
Multipulse AC-DC Converters 14 1.4.3 Analysis, Design and Development of Non-Isolated Controlled
Multipulse AC-DC Converters 14 1.4.4 Analysis, Design and Development of Isolated Controlled
Multipulse AC-DC Converters 15 1.4.5 Analysis, Design and Development of Non-Isolated Full-Wave
AC-DC Converters 15 1.4.6 Analysis, Design and Development of Isolated Full-Wave AC-
DC Converters 16 1.4.7 Analysis, Design and Development of Unconventional AC-DC
Converters 16 1.5 Outline of Chapters 17
CHAPTER II LITERATURE REVIEW 21-41 2.1 General 21 2.2 Significant Developments in Multipulse AC-DC Converters 22 2.3 Performance Parameters of Multi-Pulse AC-DC Converters 23 2.4 Literature Review on Multipulse AC-DC Converters 26
2.4.1 Non-Isolated Uncontrolled AC-DC Converters 27 2.4.2 Isolated Uncontrolled AC-DC Converters 30 2.4.3 Non-Isolated Controlled AC-DC Converters 33 2.4.4 Isolated Controlled AC-DC Converters 35 2.4.5 Full-Wave Isolated AC-DC Converters 39 2.4.6 Unconventional AC-DC Converters 39
xi
2.5 Identified Research Areas 40 2.6 Conclusions 40
CHAPTER III CLASSIFICATION AND TECHNIQUES OF MULTIPULSE AC-DC CONVERTERS 42-72
3.1 General 43 3.2 Potential Applications of Multipulse AC-DC Converters 44
3.2.1 Non-Isolated AC-DC Converters 44 3.2.2 Isolated AC-DC Converters 45 3.2.3 Uncontrolled AC-DC Converters 46 3.2.4 Controlled AC-DC Converters 46
3.3 Classification of Multipulse AC-DC Converters 48 3.3.1 Uncontrolled and Controlled AC-DC Converters 49 3.3.2 Non-Isolated and Isolated AC-DC Converters 51 3.3.3 Full-Wave and Bridge AC-DC Converters 52 3.3.4 Transformer Winding Connections Based Classification 53 3.3.5 Number of Pulses Based Classification 53
3.4 Techniques Employed in Multipulse AC-DC Converters 54 3.4.1 Phase Staggering Technique 54 3.4.2 Multiphase Technique 56 3.4.3 Ripple Reinjection Technique 57 3.4.4 Hybrid of Phase Staggering, Multiphase and Ripple
Reinjection Techniques 59 3.5 Performance of Multipulse Converters 60 3.6 Conclusions 61
CHAPTER IV ANALYSIS, DESIGN AND CLASSIFICATION OF TYPICAL LOADS ON MULTIPULSE AC-DC CONVERTERS 73-127
4.1 General 73 4.2 Classification of Typical Loads on Multipulse AC-DC Converters 74
4.2.1 Loads Fed from Non-Isolated Uncontrolled AC-DC Converters 74 4.2.1.1 Variable Frequency Induction Motor Drives 75 4.2.1.2 Switch Mode Power Supplies 76 4.2.1.3 Electronic Load Controller (ELC) for Stand-Alone
Renewable Power Generators 77 4.2.2 Loads on Isolated Uncontrolled AC-DC Converters 78
4.2.2.1 Electrowinning 78 4.2.2.2 Sintering 80 4.2.2.3 Induction Heating and Welding Equipments Working
on High Frequency 81 4.2.2.4 Electroplating 82 4.2.2.5 Welding 84 4.2.2.6 Traction Systems Working on DC Supply 84 4.2.2.7 Plasma Torch 85
4.2.3 Loads on Non-Isolated Controlled AC-DC Converters 86 4.2.3.1 DC Motor Drives 86 4.2.3.2 Current Source Inverter Fed Drives 86
xii
4.2.4
4.2.3.3 Field Excitation of Large Alternators Loads on Isolated Controlled AC-DC Converters
4.2.4.1 Arc Furnaces
4.2.4.2 Steel Rolling Mills
4.2.4.3 Line Commuted Inverter Fed Synchronous Motor Drives
86 87 88 89
89 4.3 Design of a Typical Load on Multipulse AC-DC Converters 90
4.3.1 Components of Direct Torque Controlled Induction Motor Drive 90 4.3.2 Components of Vector Controlled Induction Motor Drive System 90
4.4 Modeling of a Load on Multipulse AC-DC Converters 91 4.4.1 Modeling of Direct Torque Controlled Induction Motor Drive 92 4.4.2 Modeling of Vector Controlled Induction Motor Drive 96
4.5 Hardware Development of VFIMD Fed from Different AC-DC Converters 98 4.5.1 DSP dSPACE DS1104 Controller 99
4.5.1.1 Current Sensing and Scaling Circuit 99 4.5.1.2 Speed Sensing and Scaling Circuit 101 4.5.1.3 Voltage Source Inverter 101 4.5.1.4 Gating Signal Isolation and Amplification Circuit 102
4.5.2 Direct Torque Controlled Induction Motor Drive System 103 4.6 Results and Discussion 103
4.6.1 Performance of Vector Controlled Induction Motor Drive Fed from 6-pulse AC-DC converters 110 4.6.1.1 Starting 110 4.6.1.2 Steady State Response 110 4.6.1.3 Load Application 111 4.6.1.4 Load Removal 111
4.6.2 Performance of Direct Torque Controlled Induction Motor Drive 112 4.6.3 Power Quality Improvements in VFIMDs 112
4.6.3.1 Performance of Vector Controlled Induction Motor Drive Fed from 12-Pulse AC-DC Converters 116
4.6.3.2 Performance of Vector Controlled Induction Motor Drive Fed from 24-pulse AC-DC converters 117
4.6.3.3 Performance of Vector Controlled Induction Motor Drive Fed from 40-Pulse AC-DC converters 122
4.7 Conclusions 125
CHAPTER V NON-ISOLATED UNCONTROLLED MULTIPULSE AC-DC CONVERTERS 128-192
5.1 General 128 5.2 Classification of Non-Isolated Uncontrolled Multipulse AC-DC
Converters 128 5.2.1 AC-DC Converters Based on Phase Staggering Technique 129
5.2.1.1 Polygon Connected Autotransformer Based MPCs 130 5.2.1.2 Fork Connected Autotransformer Based MPCs 130 5.2.1.3 T-Connected Autotransformer Based MPCs 131
5.2.2 AC-DC Converters Based on Multiphase Technique 132 5.2.2.1 Polygon Connected Autotransformer Based MPCs 132
5.2.2.2 Fork Connected Autotransformer Based MPCs 133 5.2.2.3 T-Connected Autotransformer Based MPCs 133
5.2.3 AC-DC Converters Based on Ripple Reinjection Technique 133 5.2.3.1 Polygon Connected Autotransformer Based MPCs 134 5.2.3.2 Fork connected Autotransformer Based MPCs 134 5.2.3.3 T-Connected Autotransformer Based MPCs 134
5.2.4 AC-DC Converters Based on Hybrid of Phase Staggering, Multiphase and Ripple Reinjection Techniques 134 5.2.4.1 Polygon Connected Autotransformer Based MPCs 135 5.2.4.2 Fork Connected Autotransformer Based MPCs 140 5.2.4.3 T-Connected Autotransformer Based MPCs 141
5.3 Design of Multipulse AC-DC Converters 141 5.3.1 Design of Zigzag Autotransformer for Direct 24-Pulse AC-DC
Converter Employing Phase Staggering and Ripple Reinjection Technique 144
5.3.2 Design of Polygon Connected Autotransformer Based 18-Pulse AC-DC Converter Employing Multiphase Technique 146
5.3.3 Zigzag Connected Autotransformers Based Twelve and Twenty Four-Pulse AC-DC Converter Employing Ripple Reinjection 147 5.3.3.1 Design of the Zigzag Autotransformer for a 24-Pulse
AC-DC Converter employing Ripple Reinjection for Pulse Doubling 147
5.3.3.2 Design of the Interphase Transformer (IPT) for Pulse Doubling 148
5.3.3.3 Design of the Autotransformer 149 5.3.3.4 Derivation for KVA Ratings of the Zigzag Connected
Autotransformers 151 5.3.4 Design of a Polygon Autotransformer Based Thirty Six-Pulse
AC-DC Converter Employing Hybrid Technique5.28 5.3.4.1 Design of autotransformer for 36-pulse AC-DC
converter 155 5.4 MATLAB Based Modeling and Simulation 158
5.4.1 Modeling of Zigzag Autotransformer Based AC-DC Converters Employing Phase Staggering Technique, Multiphase Technique and Ripple Reinjection Technique 158
5.4.2 MATLAB Model of Polygon Connected Autotransformer Based 36-Pulse AC-DC Converter Employing Hybrid Technique5.34
5.5 Hardware Implementation of Multipulse AC-DC Converters 163 5.5.1 Hardware Development of Differential-Delta and Polygon
Wound 12-Pulse AC-DC Converter and 24-Pulse AC-DC Converter Employing Pulse-Doubling 163
5.5.2 Hardware Development of Zigzag Connected Autotransformer for Twelve-Pulse and Twenty Four-Pulse AC-DC Converters 167
5.5.3 Hardware for Polygon Autotransformer Based AC-DC Converter Employing Hybrid Technique 168
5.6 Results and Discussion 172
xiv
5.6.1 Performance of AC-DC Converters Based on Zigzag Connected Transformers Employing Phase Staggering and Ripple Reinjection Technique 173
5.6.2 Performance of AC-DC Converters Based on Fork-Connected Autotransformers Employing Phase Staggering, Ripple Reinjection and Hybrid Technique 180
5.6.3 Performance of AC-DC Converters Based on Polygon- Connected Autotransformer Employing Phase Staggering, Multiphase and Hybrid Technique 181
5.6.4 Performance of AC-DC Converters Employing Polygon and Differential Delta Connected Autotransformers 186
5.6.5 Comparative Study of Different Multipulse AC-DC Converters 188 5.7 Conclusions 191
CHAPTER VI ISOLATED UNCONTROLLED MULTIPULSE AC-DC CONVERTERS
6.1 General 6.2 Classification of Isolated Uncontrolled Multipulse AC-DC Converters
6.2.1 AC-DC Converters Based on Phase Staggering Technique 6.2.1.1 Polygon Connected Transformer 6.2.1.2 Fork Connected Transformer 6.2.1.3 T-Connected Transformer
6.2.2 AC-DC Converters Based on Multiphase Technique 6.2.2.1 Polygon Connected Transformer 6.2.2.2 Fork Connected Transformer 6.2.2.3 T-Connected Transformer
6.2.3 AC-DC Converters Based on Ripple Reinjection Technique 6.2.3.1 Polygon Connected Transformer 6.2.3.2 Fork Connected Transformer 6.2.3.3 T-Connected Transformer
6.2.4 AC-DC Converters Based on Hybrid of Phase Staggering, Multiphase and Ripple Reinjection Techniques 6.2.4.1 Polygon Connected Transformer 6.2.4.2 Fork Connected Transformer 6.2.4.3 T-Connected Transformer
6.3 Design of Isolated Multipulse AC-DC Converters 6.3.1 Design of Fork Transformers
6.3.1.1 Design of Fork Transformers for 12-Pulse and 24-Pulse AC-DC Converters
6.3.1.2 Design of delta/fork transformer suitable for 36-pulse AC-DC rectification employing multiphase and phase staggering technique
6.3.2 Design of T-Connected Transformers Employing Phase Staggering Technique and Hybrid Technique 6.3.2.1 Design of T-Connected Six-Pulse AC-DC Converter
Transformer 6.3.2.2 Design of T-connected Twelve-Pulse AC-DC Converter
193-259 193 194 195 196 196 196 196 196 197 197 197 197 198 198
198 198 205 205 206 206
206
208
210
210 211
XV
6.3.2.3 Design of T-Connected Multiphase Eighteen-Pulse AC- DC Converter
6.3.2.4 Design of T-connected, Hybrid Technique Based Thirty Six-Pulse AC-DC Converter
214
215 6.3.3 Design of Polygon Based AC-DC Converter employing Ripple
Reinjection Technique 215 6.3.3.1 Delta/Triple Delta-Polygon Transformer for 18-pulse
converter 216 6.3.3.2 Operation of the Tapped Inter-Phase Reactor (IPR) 217
6.4 MATLAB Based Modeling and Simulation 222 6.4.1 Fork Connections Based on Phase Staggering Technique and
Hybrid Technique 222 6.4.2 T-Connection Based AC-DC Converter 224 6.4.3 Polygon Based AC-DC Converter 224
6.5 Hardware Implementation of Multipulse AC-DC Converters 226 6.5.1 AC-DC Converters Based on Phase Staggering Technique 229 6.5.2 AC-DC Converters Based on Multiphase Technique 229 6.5.3 AC-DC Converters Based on Ripple Reinjection Technique 231
6.6 Results and Discussion 231 6.6.1 Performance of 12-Pulse AC-DC Converters Based on Phase
Staggering Technique 231 6.6.2 Performance of Various Fork Connected AC-DC converters 234 6.6.3 Performance of AC-DC Converters Based on Hybrid of Phase
Staggering, Multiphase and Ripple Reinjection.Techniques 237 6.6.4 Performance of T-Connected 36-Pulse AC-DC Converter Based on
Multiphase and Hybrid Techniques 242 6.6.5 Performance of Hybrid Technique Based AC-DC Converters 245
6.6.5.1 Performance of delta/fork connected 36-pulse AC-DC converter employing hybrid of phase staggering and multiphase techniques 245
6.6.5.2 Performance of Delta/Triple-Delta-Polygon Connected 36-Pulse Ac-Dc Converter Employing Hybrid of Phase Staggering, Multiphase Techniques and Pulse Multiplication Technique 245
6.7 Conclusions 257
CHAPTER VII NON-ISOLATED CONTROLLED MULTIPULSE AC-DC CONVERTERS 260-305
7.1 General 260 7.2 Classification of Non-Isolated Controlled Multipulse AC-DC
Converters 261 7.2.1 AC-DC Converters Based on Phase Staggering Technique 261
7.2.1.1 Polygon Connected Autotransformer 264 7.2.1.2 Fork Connected Autotransformer 262 7.2.1.3 T-Connected Transformer 263
7.2.2 AC-DC Converters Based on Multiphase Technique 263 7.2.2.1 Polygon Connected Autotransformer 264 7.2.2.2 Fork Connected Autotransformer 264
xvi
7.2.2.3 T-Connected Transformer 264 7.2.3 AC-DC Converters Based on Ripple Reinjection Technique 267
7.2.3.1 Polygon Connected Autotransformer Based AC-DC Converter Employing Ripple Reinjection Technique 267
7.2.3.2 Fork Connected Autotransformer Based AC-DC Converter Employing Ripple Reinjection Technique 268
7.2.3.3 T-Connected Autotransformer Based AC-DC Converter Employing Ripple Reinjection Technique 268
7.2.4 AC-DC Converters Based on Hybrid Technique 268 7.2.4.1 Polygon Connected Autotransformer 268 7.2.4.2 Fork Connected Autotransformer 269 7.2.4.3 T-Connected Autotransformer 269
7.3 Design of Non-isolated Multipulse AC-DC Converters 272 7.3.1 Design of Polygon Wound Autotransformer for 12-Pulse AC-
DC Rectification 273 7.3.2 Design of Interphase Reactor (IPR) and Control Strategy for
the Polygon-Autotransformer Based Controlled AC-DC Converter 274
7.3.3 Design of High Pass Filter 276 7.3.4 Zigzag Connected Autotransformer Based 36-Pusle AC-DC
Converter 280 7.3.5 Design of Zigzag Connected Autotransformer for 12-Pulse
Controlled AC-DC Converter 281 7.4 MATLAB Based Modeling and Simulation 282
7.4.1 MATLAB based simulation of polygon wound 36-pulse controlled AC-DC converter 283
7.4.2 MATLAB based simulation of zigzag wound 36-pulse controlled AC-DC converter 283
7.5 Hardware Implementation 284 7.6 Results and Discussion 287
7.6.1 Performance of AC-DC Converters Based on Polygon Wound Autotransformers 287
7.6.2 Performance of AC-DC Converters Based on Zigzag Wound Autotransformers 287
7.6.3 Experimental Performance of Zigzag Based Controlled AC-DC converters 292
7.7 Conclusions 304
CHAPTER VIII ISOLATED CONTROLLED MULTIPULSE AC-DC CONVERTERS 306-351
8.1 General 306 8.2 Classification of Isolated Controlled Multipulse AC-DC Converters 307
8.2.1 AC-DC Converters Based on Controlled AC-DC Converters employing Phase Staggering Technique 308 8.2.1.1 AC-DC Converters Based on Isolated Secondary
Winding Based Transformers in Controlled AC-DC Converters employing Phase Staggering Technique 308
8.2.1.2 Transformers with Delta Primary Windings 309
xvii
8.2.1.3 Transformer with Star Primary 309 8.2.1.4 AC-DC Converters Based on Single Secondary
Transformer Based Converters Employing Phase Staggering Technique 311
8.2.2 AC-DC Converters Based on Multiphase Technique 313 8.2.2.1 Polygon Connected Secondary Transformer Based
Multiphase AC-DC Converter 313 8.2.2.2 Fork Connected Secondary Transformer Based
Multiphase AC-DC Converter 313 8.2.2.3 T Connected Secondary Transformer Based
Multiphase AC-DC Converter 314 8.2.3 AC-DC Converters Based on Ripple Reinjection Technique 315
8.2.3.1 AC-DC Converters Based on Polygon Transformer Employing Ripple Reinjection Technique 316
8.2.3.2 AC-DC Converters Based on Delta/Fork transformer employing Ripple Reinjection Technique 316
8.2.3.3 AC-DC Converters Based on T/T Transformer Employing Ripple Reinjection Technique 316
8.2.4 AC-DC Converters Based on Hybrid of Phase Staggering, Multiphase and Ripple Reinjection Techniques 319 8.2.4.1 Polygon Connected Secondary Transformer Based
controlled AC-DC Converter employing hybrid technique 320
8.2.4.2 Fork Connected Secondary Transformer Based controlled AC-DC Converter Employing Hybrid Technique 320
8.2.4.3 T Connected Secondary Transformer Based controlled AC-DC Converter employing hybrid technique 320
8.3 Design of Multipulse AC-DC Converters 321 8.3.1 Design of Parallel Converters with Pulse-Multiplication 322 8.3.2 Derivation of the Current Waveforms 323 8.3.3 Derivation of the modified load voltage waveform 324
8.4 MATLAB Based Modeling and Simulation 324 8.5 Hardware Implementation of Isolated Controlled Multipulse AC-DC
Converters 327 8.5.1 Twelve-Pulse AC-DC Converter 330 8.5.2 Twelve-Pulse AC-DC Converters with High-Pass Filter 330
8.6 Results and Discussion 330 8.6.1 Performance of 12-Pulse AC-DC Converters 330 8.6.2 Performance of AC-DC Converters Based on Ripple Re-
injection Technique 331 8.6.3 Experimental Performance of 12-Pulse AC-DC Converters
with and without High-Pass Filter 332 8.7 Conclusions 350
xviii
CHAPTER IX NON-ISOLATED FULL-WAVE MULTIPULSE AC-DC CONVERTERS
9.1 General
9.2 Classification of Non-Isolated Full-Wave Multipulse AC-DC Converters
352-394 352
353 9.2.1 Full-Wave AC-DC converters Based on Star Connection 354 9.2.2 Full-Wave AC-DC converters Based on Zig-Zag- Polygon
Connection 355 9.2.3 Full-Wave AC-DC converters Based on T-Connection 355
9.3 Design of Non-Isolated Full-Wave Multipulse AC-DC Converters 356 9.3.1 Full-Wave AC-DC Converters Based on Star Connection 356 9.3.2 Full-Wave AC-DC Converters Based on Zig-Zag Connection 358 9.3.3 Full-Wave AC-DC converters Based on T-Connection 359
9.4 MATLAB Based Modeling and Simulation 370 9.4.1 Six-pulse full-wave AC-DC converters 370 9.4.2 Twelve-pulse full-wave AC-DC converters 370 9.4.3 Eighteen-Pulse Full-Wave AC-DC Converters 371 9.4.4 Twenty Four-Pulse Full-Wave AC-DC Converters 371
9.5 Hardware Implementation 371 9.5.1 Full-Wave 18-pulse AC-DC Converters Based on Star
Connection 371 9.5.2 Full-Wave AC-DC Converters Based on Zig-Zag Connection 375
9.6 Results and Discussion 377 9.6.1 Performance of Full-Wave AC-DC Converters Based on Star
Connection 377 9.6.2 Performance of Full-Wave AC-DC Converters Based on Zig-
Zag Connection 379 9.6.3 Performance of Full-Wave AC-DC Converters Based on T-
Connection 380 9.7 Conclusions 393
CHAPTER X ISOLATED FULL-WAVE MULTIPULSE AC-DC CONVERTERS 395-431
10.1 General 395 10.2 Classification of Isolated Multipulse Full-Wave AC-DC Converters 397
10.2.1 Full-Wave AC-DC Converters Based on Star Connection 397 10.2.1.1 6-Pulse Full-Wave AC-DC Converters 398 10.2.1.2 12-Pulse Full-Wave AC-DC Converter 398 10.2.1.3 18-Pulse Full-Wave AC-DC Converters 399 10.2.1.4 24-Pulse Full-Wave AC-DC Converters 399
10.2.2 Full-Wave AC-DC Converters Based on Zig-Zag Connection 401 10.2.2.1 6-Pulse Full-Wave AC-DC Converters 402 10.2.2.2 12-Pulse Full-Wave AC-DC Converter 402 10.2.2.3 18-Pulse Full-Wave AC-DC Converters 402 10.2.2.4 24-Pulse Full-Wave AC-DC Converters 402
10.2.3 Full-Wave AC-DC Converters Based on T-Connection 404 10.2.3.1 6-Pulse Full-Wave AC-DC Converters 404 10.2.3.2 12-Pulse Full-Wave AC-DC Converter 404
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10.2.3.3 18-Pulse Full-Wave AC-DC Converters 405 10.2.3.4 24-Pulse Full-Wave AC-DC Converters 405
10.3 Design of Multipulse Full-Wave AC-DC Converters 407 10.3.1 Design of Delta/Fork Transformer Suitable for 18-Pulse AC-
DC Conversion 407 10.3.2 Transformer Rating for 18-Pulse AC-DC Converter 409
10.4 MATLAB Based Modeling and Simulation 411 10.4.1 Full-Wave AC-DC Converters Based on Star Connection 412 10.4.2 Full-Wave AC-DC Converters Based on zigzag Connection 412 10.4.3 Full-Wave AC-DC Converters Based on T Connection 413
10.5 Hardware Implementation 417 10.6 Results and Discussion 418
10.6.1 Performance of Full-Wave AC-DC Converters Based on Star Connection 418
10.6.2 Performance of Full-Wave AC-DC Converters Based on Zigzag Connection 419
10.6.3 Performance of Full-Wave AC-DC Converters Based on T- Connection 420
10.7 Conclusions 430
CHAPTER XI UNCONVENTIONAL MULTIPULSE AC-DC CONVERTERS 432-470
11.1 General 432 11.2 Classification of Unconventional Multipulse AC-DC Converters 433
11.2.1 AC-DC Converters Based on Hybrid of Phase Staggering and Multiphase Technique 434 11.2.1.1 Autotransformer Connections for 20/28/44 Pulse
Converters 434 11.2.1.2 Isolated Transformer Connections for 20/28/44 Pulse
Converters 435 11.2.2 AC-DC Converters Based on Hybrid of Phase Staggering,
Multiphase and Ripple Reinjection Technique 436 11.2.2.1 Autotransformer Connections for 40/56/88 Pulse
Converters 437 11.2.2.2 Isolated Transformer Connections for 40/56/88 Pulse
Converters 437 11.3 Design of Unconventional Multipulse AC-DC Converters 437
11.3.1 Design of Autotransformer for 20-Pulse and 40-Pulse AC-DC Converters 437
11.3.2 Design of transformer for 28-Pulse and 56-Pulse AC-DC Converters 440
11.3.3 Design of transformer for 44-Pulse and 88-Pulse AC-DC Converters 442
11.4 MATLAB Based Modeling and Simulation 444 11.5 Hardware Implementation of Multipulse AC-DC Converters 448
11.5.1 AC-DC Converters Based on Hybrid of Phase Staggering and Multiphase Techniques 449
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11.5.2 AC-DC Converters Based on Hybrid of Phase Staggering, Multiphase and Ripple Re-injection Techniques 450
11.6 Results and Discussion 452 11.6.1 Performance of 20, 22 and 44-pulse AC-DC Converters Based
on Phase Staggering, and Multiphase Techniques 453 11.6.2 Performance of 40, 56 and 88-pulse AC-DC Converters AC-
DC Converters Based on Phase Staggering, Multiphase and Ripple Reinjection Techniques 455
11.7 Conclusions 469
CHAPTER XII MAIN CONCLUSIONS AND SUGGESTIONS FOR FURTHER WORK 471-478
12.1 General 471 12.2 Main Conclusions 471 12.3 Suggestions for Further Work 478
REFERENCES 479-505
APPENDICES 506-537
LIST OF PUBLICATIONS 538-540
BIO-DATA 541
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