Low Power AC-DC and DC-DC Multilevel Converters

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Electronic Thesis and Dissertation Repository
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Mehdi Narimani, The University of Western Ontario
Supervisor: Dr. Gerry Moschopoulos, The University of Western Ontario
A thesis submitted in partial fulfillment of the requirements for the Doctor of Philosophy degree
in Electrical and Computer Engineering
© Mehdi Narimani 2012
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Low Power AC-DC and DC-DC
Multilevel Converters

By

Mehdi Narimani

Graduate Program in Engineering Science
Department of Electrical and Computer Engineering

A Thesis Submitted in Partial Fulfillment
of the Requirements for the Degree of
Doctor of Philosophy

School of Graduate and Postdoctoral Studies
The University of Western Ontario
London, Ontario, Canada

© Mehdi Narimani 2012

i
THE UNIVERSITY OF WESTERN ONTARIO
SCHOOL OF GRADUATE AND POSTDOCTORAL STUDIES

CERTIFICATE OF EXAMINATION

Supervisor: Examiners:

Dr. Gerry Moschopoulos Dr. Mohammad Dadash Zadeh

Dr. Jayshri Sabarinathan

Dr. James Wisner

Dr. Alireza Bakhshai

The thesis by

Mehdi Narimani

entitled:

Low Power AC-DC and DC-DC Multilevel Converters

is accepted in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy

Date:
Chair of thesis Examination Board

ii
Abstract
AC-DC power electronic converters are widely used for electrical power
conversion in many industrial applications such as for telecom equipment, information
technology equipment, electric vehicles, space power systems and power systems based
on renewable energy resources. Conventional AC-DC converters generally have two
conversion stages – an AC-DC front-end stage that operates with some sort of power
factor correction to ensure good power quality at the input, and a DC-DC conversion
stage that takes the DC output of the front-end converter and converts it to the desired
output DC voltage. Due to the cost of having two separate and independent converters,
there has been considerable research on so-called single-stage converters – converters
that can simultaneously perform AC-DC and DC-DC conversion with only a single
converter stage. In spite of the research that has been done on AC-DC single-stage, there
is still a need for further research to improve their performance.
The main focus of this thesis is on development of new and improved AC-DC
single-stage converters that are based on multilevel circuit structures (topologies) and
principles instead of conventional two-level ones. The development of a new DC-DC
multilevel converter is a secondary focus of this thesis. In this thesis, a literature survey
of state of the art AC-DC and DC-DC converters is performed and the drawbacks of
previous proposed converters are reviewed. A variety of new power electronic converters
including new single-phase and three-phase converters and a new DC-DC converter are
then proposed. The steady-state characteristics of each new converter is determined by
mathematical analysis, and, once determined, these characteristics are used to develop a
procedure for the design of key converter components. The feasibility of all new
converters is confirmed by experimental results obtained from proof-of-concept
prototype converters. Finally, the contents of the thesis are summarized and conclusions
about the effectiveness of using multilevel converter principles to improve the
performance of AC-DC and DC-DC converters are made.
KEY WORDS: Single-Phase AC-DC Rectifiers, Three-Phase AC-DC Rectifiers,
Power Factor Correction, Single-Stage Converters, DC-DC Converters, Multilevel
Converters.
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Acknowledgements

I would like to express my sincere gratitude to my supervisor, Dr. Gerry
Moschopoulos, for his invaluable supervision, encouragement, and financial support
throughout my Ph.D. studies.
Furthermore, I should acknowledge great efforts of the entire Ph.D. exam
committee: Dr. Mohammad Dadash Zadeh, Dr. Jayshri Sabarinathan, Dr. James Wisner
and Dr. Alireza Bakhshai for their review of this thesis, discussions and comments.
I would also like to express special thanks to Mrs. Melissa Harris, the
Administrative Officer and Mr. Christopher Marriott, the graduate coordinator at the
Department of Electrical and Computer Engineering at University of Western Ontario for
their great help with all the procedural and paper work throughout my time in the Ph.D.
program.
Last but not least I would like to thank my wife and my parents for their love and
support without which I could not have been able to make it through the frustrations of
the past few years.

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To my lovely wife
and
my parents

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Table of Contents

CERTIFICATE OF EXAMINATION ……………….……………………… ii
Abstract ……………………………………………………………………. iii
Acknowledgements ………………………………………………………… iv
Table of Content …………………………………………………………….. vi
List of Figures ……………………………………………………………… xi
Acronyms ………………………………………………………………….. xvi
Abbreviations ……………………………………………………………… xvii
1 Introduction 1
1.1. Single-Phase AC-DC Converters (Rectifiers) ………………………………. 1
1.1.1. Power Factor Correction Techniques …………………………….. 2
1.1.1.1. Passive Power Factor Correction ……………………. 2
1.1.1.2. Active Power Factor Correction ……………………… 3
1.1.2. Review of Single-Phase Single-Stage PFC Converters 4
1.2. Three-Phase AC-DC Converters (Rectifiers) ………………………………. 8
1.2.1. Review of Three-Phase Single-Stage PFC Converters 8
1.3. DC-DC Converters ……………………………………………………………………. 12
1.3.1. Review of DC-DC Converters …………………………………….. 13
1.3.1.1. Light Load Efficiency ………………………………………. 13
1.3.1.2. Circulating Current ………………………………………….. 14
1.4. Thesis Objectives ………………………………………………………………………. 15
1.5. Thesis Outline ….............................................................................. 16
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2. Single-Phase Single-Stage Three-Level Power Factor Correction AC-
18
DC Converters
2.1. Introduction ……………………………………………………………………………………... 18
2.2. A New Single-Phase Single-Stage Three-Level Power Factor
19
Correction AC-DC Converter …………………………………………………………
2.3. Operation of the Proposed Converter …………………………………….……… 19
2.4. Features of the Proposed Converter ……………………………………..…..….. 27
2.5. Steady State Analysis …………………………………………………………………….. 27
2.6. Balancing of DC Bus Capacitors ………………………………………………….. 33
2.7. Converter Design ……………………………………………………………………………. 36
2.8. Experimental Results …………………………………………….…………………..…... 41
2.9. Conclusion …………………………………………………………………………….………… 49

3. Modified Single-Phase Single-Stage Three-Level Power Factor
Correction AC-DC Converters 50
3.1. Introduction ……………………………………..……………………………………..…….. 50
3.2. A Single-Phase Single-Stage Three-Level Power Factor
50
Correction AC-DC Converter with Auxiliary Circuit ……….………
3.2.1. Effect of Output Inductor on DC Bus and Output Ripple 51
3.2.2. Operation of the Auxiliary Circuit in SSPFC Three-
52
Level Converter ……………………………………..……………………...
3.2.3. Experimental Results ……………………………………..…………..… 55
3.3. Single-Phase Single-Stage Three-Level Power Factor Correction
vii
AC-DC Converter with Phase-Shift Modulation (PSM) ……..…… 58
3.3.1. Phase-Shift Technique for Three-Level Single-Stage
Converters ……………………………………………………………………… 58
3.3.2. Experimental Results ………………………………………………….… 63
3.4. Conclusion ………………………………………………………………………………………… 67

4. A Single-Stage Three-Level AC-DC Converter with Two
68
Controllers
4.1. Introduction ……………………………………………………………………………………..… 68
4.2. Converter Operation ……………………………………………………………………….… 68
4.3. Converter Design ……………………………………………………………………..……..… 76
4.4. Experimental Results …………………………………………………………………..…… 78
4.5. Conclusion ………………………………………………………………………………………… 82

5. Three-Phase Single-Stage Three-Level Power Factor Correction
84
AC-DC Converters
5.1. Introduction ………………………………………………..……………………………………… 84
5.2. New Three-Phase Single-Stage Three-Level Power Factor
85
Correction AC-DC Converters ………………………….……………………………
5.2.1. Converter Operation ………………………………………………………… 86
5.2.2. Steady State Analysis ……………………………………………………… 93
5.2.3. Converter Design ………………………………………………..…………… 100
5.2.4. Experimental Results ……………………………………………….……… 107
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5.3. A New Interleaved Three-Phase Single-Stage Three-Level Power
Factor Correction AC-DC Converter ……………………….…………………... 113
5.3.1. Converter Operation …………………………………..………………….… 114
5.3.2. Converter Characteristics …………………………….……………….… 121
5.3.3. Converter Design …………………………………………….…………….… 125
5.3.4. Experimental Results and Converter Analysis ……………… 128
5.4. Conclusion …………………………………………………………………………………………. 134

6. Multilevel DC-DC Converters 136
6.1. Introduction ………………………………………………………….…………………………….… 136
6.2. Three-Level DC-DC Converters for Switch-Mode Power Supplies 136
6.2.1. Modes of Operation …………………………………………………………………… 138
6.2.2. Comparison of Two-Level and Three-Level DC-DC Converter 141
6.2.3. Experimental Results ………………………………………………………………… 145
6.3. A New DC-DC Converter with Wide-Range ZVS and Zero
Circulating Current ……………………………………………………………………………… 149
6.3.1. Basic Principles …………………………….…………………………………………… 151
6.3.2. Converter Operation …………………………………………………………………. 155
6.3.3. Design Procedure …………………………………………………………….………… 165
6.3.4. Experimental Results …………….…………………………………………………. 170
6.4. Conclusion …………………………………………………………………………………………… 175

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