本篇論文在串聯型△接的系統架構上，提出一種新的電壓平衡控制。核心想法是從功率的觀點分析電路系統，釐清不平衡功率形成的原因，並進而產生零序電流命令去平衡掉這些使得電壓發散的不平衡功率。
此外，串聯型△接全橋轉換器通常應用於電弧爐補償，針對電弧爐補償，主要需要三種補償控制，分別是虛功補償、負序電流補償、低頻實功補償。因此本篇論文在補償負序電流的設定上，去探討串聯型全橋轉換器在電壓平衡控制上的表現。
不僅如此，本篇論文也把串聯型Ｙ接全橋轉換器，在補償負序電流的情況下，去探討對電壓平衡控制上的影響，並釐清在補償負序電流的情況下，最需考量的因素成分，進而設計出針對此情況下，所需的電壓命令值，最終達成補償負序電流的情況下，同時能完成電壓平衡控制的目標。

This thesis propose a new dc bus voltage balancing control towards the modular multilevel cascaded converter (MMCC) with the circuit configuration of singe-delta bridge cells (SDBC). The core idea is to generate a zero-sequence current (ZSC) command from the perspective of power flow analysis to balance the unbalanced clustered power.
In addition, the MMCC-SDBC usually serves in the application of flicker compensation towards electrical arc furnace (EAF). For the flicker compensation of EAF, it usually requires compensating reactive power, negative-sequence current, and low-frequency active power. As a result, this thesis research the dc bus voltage balancing control towards MMCC under the condition of compensating negative-sequence current.
Furthermore, this thesis also analyzes the influences of negative-sequence current on the MMCC with the circuit configuration of singe-star bridge cells (SSBC). It takes these influences of negative-sequence current into consideration, then it designs a dc bus voltage command to make the MMCC-SSBC can achieve the goal of balancing dc bus voltages and compensating negative sequence current at the same time.

摘要 i
Abstract ii
誌謝 iii
Contents iv
List of Tables vii
List of Figures ix
Chapter 1 Introduction 1
1.1 Background 1
1.2 Organization of the Thesis 3
Chapter 2 Literature Review 4
2.1 Introduction 4
2.2 Modulation Technique 5
2.3 DC buses Voltage Balancing Control in SDBC & SSBC 7
2.3.1 Akagi’s DC Bus Voltage Balancing Control in SDBC 7
2.3.2 Laboratory’s DC Bus Voltage Balancing Control in SSBC 12
2.4 Summary 18
Chapter 3 Operation Principles 19
3.1 Introduction 19
3.2 Power Flow Analysis 20
3.2.1 Overall Active power Control 21
3.2.2 Reactive Power Control 23
3.2.3 Clustered Voltage Balancing Control Based on ZSC in SDBC 24
3.2.4 Individual Voltage Balancing Control in SDBC 29
3.3 The Design of DC Bus Voltage Command under NSC Compensation 32
3.3.1 The Design of DC Bus Voltage Command towards SSBC 32
3.3.2 The Design of DC Bus Voltage Command towards SDBC 35
Chapter 4 Simulation Results 38
4.1 Introduction 38
4.1.1 Environment Set Up of SDBC 38
4.1.2 Environment Set Up of SSBC 40
4.2 Comparison of Proposed ZSC method and Akagi’s ZSC method 42
4.3 Comparison of Proposed ZSC in SDBC and the Laboratory’s ZSV in SSBC 44
4.4 Comparison of Proposed ZSC With and Without Feed-forward Term 47
4.5 Verrify the Designed Methods of DC Bus Voltage Command…..……………..
under NSC Compensation 48
4.5.1 Verrify the Designed method of DC Bus Voltage towards SSBC 49
4.5.2 Verrify the Designed method of DC Bus Voltage towards SDBC 52
4.6 Summary 55
Chapter 5 Laboratory Test Results 56
5.1 Introduction 56
5.2 Comparison of Proposed ZSC method and Akagi’s ZSC method 56
5.3 Comparison of Proposed ZSC in SDBC and the Laboratory’s ZSV in SSBC 60
5.4 Comparison of Proposed ZSC With and Without Feed-forward Term 64
5.5 Verrify the Designed Methods of DC Bus Voltage Command…..……………..
under NSC Compensation 65
5.5.1 Verrify the Designed method of DC Bus Voltage towards SSBC 66
5.5.2 Verrify the Designed method of DC Bus Voltage towards SDBC 68
5.6 Summary 69
Chapter 6 Conclusion and Future Work 70
6.1 Conclusion 70
6.2 Future work 71
Reference 72

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