Single-Phase Single-Stage PWM AC-AC Converters with Bipolar Voltage Gain and Versatile Modes of Operation : 바이폴라 전압 이득 및 다양한 동작 모드를 갖춘 단상 단일-스테이지 PWM AC-AC 컨버터

다국어 초록 (Multilingual Abstract)

There are three commonly used PWM ac-ac power converter topologies, namely: 1) Indirect ac-dc-ac converters with dc-link capacitor. 2) Matrix converters. 3) Direct pulse width modulated (PWM) ac-ac converters. The first two topologies can provide ac output voltage with variable amplitude and frequency, owing to their symmetric bipolar voltage gain capability, with both non-inverting and inverting voltage operations. Whereas, the third one can only provide voltage regulation, as they usually suffer from unipolar voltage gain range. The bipolar voltage gain capability is necessary to provide variable frequency operation, which is required for applications such as variable speed drives, and induction heating, etc. In addition, the non-inverting and inverting output voltages are required in utility voltage compensation applications, to mitigate both voltage sags and swells. Despite their bipolar voltage gain capability, the indirect ac-dc-ac converters require two-stage power conversion with bulky and short-life dc-link capacitors, whereas the matrix converters require large number of active switches.
The new simple topologies of single-phase single-stage ac-ac and matrix converters are proposed in this dissertation, with bipolar voltage gain range, and with/without high-frequency transformer (HFT) isolation. The proposed topologies can provide the versatile modes of operation with both non-inverting and inverting output voltages, without using bulky dc-link capacitor or large number of active switches, as required in the case of indirect ac-dc-ac converters and matrix converters, respectively.
In the first part of the dissertation, a single-phase single-stage non-isolated buck-boost ac-ac or matrix converter is proposed, which can operate as traditional non-inverting buck and boost converters, and non-inverting/inverting buck-boost converters as well. Whereas it uses smaller number of active switches and passive components. It combines the functions of basic conventional ac-ac buck, boost and buck-boost converters, with additional benefits of no shoot-through or commutation problem, and no reverse recovery problem of body diodes when MOSFETs are used as switching devices. Therefore, it can be used to replace its conventional counterparts in ac-ac applications.
The second part of the dissertation deals with a single-phase single-stage buck ac-ac or matrix converter with symmetric bipolar voltage gain and high-frequency transformer (HFT) isolation. It can be used in ac-ac applications with electrical isolation requirements such as utility voltage compensation, etc., with the benefit of eliminating bulky and costly line frequency transformer.
In the third part of the dissertation, a class of high-frequency transformer (HFT) isolated single-phase Z-source ac-ac converters is proposed. The proposed converters retain all the benefits of existing non-isolated Z-source converters such as; buck-boost voltage capability with reversing or maintain phase-angle, reducing the in-rush and harmonic currents, and improving reliability. Moreover, the HFT isolation eliminate the need for bulky line frequency transformer, which is otherwise required in their applications as dynamic voltage restorer (DVR) to compensate voltage sag/swell, and static volt-ampere reactive (VAR) compensator, etc.
The switching strategies for various operations of the proposed topologies are developed, and detailed analysis, design guidelines and appropriate comparisons are presented. The laboratory prototypes of the proposed converters are also fabricated, and experimental results are provided to confirm their operation.

국문 초록 (Abstract)

본 논문은 바이폴라 전압 이득 및 다양한 동작 모드를 가진 새로운 단상 단일-스테이지 AC-AC 및 매트릭스 컨버터를 제안한다. 간접적인 ac-dc-ac 컨버터 및 매트릭스 컨버터가 요구될 경우 제안된 토폴로지는 큰 DC 커패시터와 많은 추가적인 스위치 없이 반전 및 비 반전 출력 전압을 가진 동작모드를 제공할 수 있다.
논문의 첫 파트에서는 단상 단일-스테이지 비 절연 벅-부스트 AC-AC 또는 매트릭스 컨버터가 제안된다. 이 컨버터는 기존의 비 반전 벅 혹은 부스트 컨버터처럼 동작 할 수 있다. 또한 이는 비 반전 및 반전 벅-부스트 동작을 제공 할 수 있다. 또한 이것은 스위치 및 기타 소자를 적게 사용합니다. 이는 슛-스루 문제와 커뮤테이션 문제를 가지지 않는다. 또한, MOSFET을 스위치로 사용하더라도, 이 회로는 바디 다이오드의 역 회복 문제가 생기지 않는다. 따라서 이는 기존의 AC-AC 애플리케이션을 대체하여 사용할 수 있다.
논문의 두 번째 파트는 바이폴라 전압 이득 및 고주파 변압기 (HFT) 절연을 갖춘 단상 단일 스테이지 벅 AC-AC 또는 매트릭스 컨버터를 다룬다. 이것은 전압 보상기 같은 크고 비싼 변압기를 제거 가능하며 전기적 절연이 필요한 AC-AC 어플리케이션에 사용 될 수 있다.
논문의 세 번째 파트에서는 고주파 변압기(HFT)로 절연한 단상 Z-소스 AC-AC 컨버터를 제안한다. 제안된 컨버터는 기존의 비 절연 Z-소스 컨버터의 모든 이점을 가지고 있다. 이 이점들은 위상 각을 반전 혹은 유지하며 인 러시 및 고조파 전류를 줄이고 신뢰성을 향상시키는 벅-부스트 전압 특징을 포함한다. 또한 HFT 절연은 전압 강하 / 팽창을 보상하기 위한 동적 전압 복원 장치 (DVR)와 같은 애플리케이션에서 요구되는 부피가 큰 라인 주파수 변압기의 필요성을 제거한다.

목차 (Table of Contents)

• List of Figures viii
• List of Tables xiii
• Chapter I Introduction 1
• 1. Background 1
• 2. Example Applications Requiring Bipolar Voltage Gain 2
• 2.1. Field upgradable transformer (FUT) 2
• 2.2. Dynamic voltage restorers (DVRs) 3
• 3. Literature Review and Contributions of This Thesis 4
• 3.1. Proposed six-switch buck-boost ac-ac converter 5
• 3.2. Proposed high-frequency isolated buck matrix converter 7
• 3.3. Proposed high-frequency isolated Z-source ac-ac converters 9
• 4. Outline of This Thesis 11
• Chapter II Six-Switch Buck-Boost AC-AC Converter 14
• 1. Conventional AC-AC Converter Topologies 14
• 2. Proposed AC-AC Converter 16
• 2.1. Commutation study of the proposed converter 17
• 2.2. Non-inverting buck mode operation 19
• 2.3. Non-inverting boost mode operation 21
• 2.4. Inverting buck-boost mode operation 24
• 2.5. Comparison with conventional non-inverting buck-boost converter 27
• 2.6. Comparison with conventional inverting buck-boost converter 30
• 3. Parameter Design of the Proposed AC-AC Converter 34
• 3.1. Design for non-inverting buck and boost mode operations 34
• 3.2. Design for inverting buck-boost operation 36
• 4. Experimental Results 37
• 5. Conclusions 50
• Six-Switch Buck-Boost Matrix Converter 51
• 6. Conventional single-phase matrix converters 51
• 7. Proposed Single-Phase Buck-Boost Matrix Converter 53
• 8. Circuit Operation and Switching Strategies for Variable Frequency Operation 53
• 8.1. 60 Hz (same frequency, ) non-inverting buck-boost operation 54
• 8.2. 60 Hz (same frequency, ) inverting buck-boost operation 56
• 8.3. 30 Hz (step-down frequency, ) buck-boost operation 57
• 8.4. 20 Hz (step-down frequency, ) buck-boost operation 58
• 8.5. 120 Hz (step-up frequency, ) buck-boost operation 59
• 8.6. 180 Hz (step-up frequency, ) buck-boost operation 60
• 9. Comparison of Proposed and Z-Source Buck-Boost MCs 60
• 10. Experimental Results 63
• 11. Summary 71
• Chapter III High-Frequency Isolated Buck Matrix Converter 72
• 1. Proposed High-Frequency Transformer Isolated Buck Matrix Converter 72
• 1.1. In-phase mode operation 75
• 1.2. Out-of-phase mode operation 80
• 1.3. Rectifier operation 84
• 1.4. Step-down frequency operation ( ) 84
• 1.5. Step-up frequency operation ( ) 85
• 2. Component Design/Selection of the Proposed HFTI Buck MC 87
• 3. Efficiency Consideration 89
• 4. Experimental Results 91
• 5. Summary 96
• Chapter IV High-Frequency Isolated Z-Source AC-AC Converters 97
• 1. Proposed Single-Phase HFT Isolated Quasi-Z-Source AC-AC Converter 97
• 2. Circuit Analysis and Operating Modes 100
• 2.1. Boost mode operation 100
• 2.2. Buck mode operation 103
• 3.Component Design/Selection of the Proposed HFT Isolated qZS AC-AC Converter 109
• 3.1. Magnetic components design 110
• 3.2. Capacitors selection 111
• 3.3. Switches selection 112
• 4. Comparison of the proposed and existing HFTI qZS ac-ac converters 116
• 5. Experimental Results 118
• 6. Conclusions 125
• Chapter V Comparison and DVR Application of the Proposed AC-AC Converters 126
• 1. Comparison of the Proposed AC-AC Converters 126
• 1.1. Operating modes and voltage gain 126
• 1.2. Step-changed frequency operation 128
• 1.3. Commutation problem and reliability 128
• 1.4. Switching devices requirement 128
• 1.5. Capacitors requirement 129
• 1.6. Magnetics requirement 129
• 2. DVR application of the proposed ac-ac converters 130
• 2.1. Six-switch buck-boost ac-ac converter based DVR 130
• 2.2. HFT Isolated buck MC based DVR 132
• 2.3. HFT Isolated qZS ac-ac converter based DVR 134
• 3. Summary 137
• Chapter VI Conclusions 138
• References 141