近幾年由於電力系統的穩定度的考量，併網型轉換器的低電壓渡過能力已被高度重視。作為其中一種併網型的轉換器，這些用作靜態同步補償器，提供虛功補償的的串接型橋式轉換器必須遵守低電壓渡過的相關規範。而轉換器中各相與各單一直流鏈之間的電壓平衡控制也是必須被妥善解決的。本論文提出一個以零序電壓注入為基礎的控制方法，有能力讓系統在嚴重的市電故障中達成電壓的平衡與維持系統的穩定。控制法是由平均功率潮流的分析推導而得，並經由實驗平台的建立與測試結果驗證轉換器在嚴重市電故障中低電壓渡過的能力。

Due to the issue of power grid stability, the low voltage rides through capabilities of grid-connected converters are highly concerned nowadays. As a kind of grid connected converter, the cascaded H-bridge converter acts as STATCOM which provides var compensation to the grid must follow the requirements. The voltage balancing between each cluster and individual cell are also critical issue that should be well solved. This thesis proposes control method which has ablilty to achieve voltage balancing and remain stable under grid fault conditions based on zero-sequence voltage injection. The control method has been derived by average power flow analysis. Experiment testbench and laboratory test results are done to verify the low voltage ride through capability of converters under severe grid faults.

Chapter 1 Introduction
Chapter 2 Literature Review
Chapter 3 Operation Principles
Chapter 4 Laboratory Test Results
Chapter 5 Conclusion and Future Work
Reference

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