以串聯式補償器為基礎的故障電流抑制技術

A Series-Compensator Based Fault Current Reduction Technique

李冠毅(Guan-Yi Lee)

指導教授 ： 鄭博泰

國立清華大學/電機資訊學院/電機工程學系/碩士(2011年)

摘要

電壓驟降發生時，經常導致敏感性設備跳機，造成嚴重的經濟損失。為了有效的改善電力品質，渡過電壓驟降事故，用戶端經常採用串聯式電壓驟降補償器進行電壓補償。但若於受保護的敏感性負載發生接地故障，為了避免串聯補償器損毀，所以不能採用傳統電壓回復的補償方式。有研究提出利用串聯補償器來做故障電流抑制策略。當敏感性負載發生故障時，將串聯補償器操作為虛擬電感。除了故障電流被有效抑制外，且其他饋線也將不會發生電壓驟降的問題。
基於以上原因本文提出利用虛擬電感限制故障電流抑制策略。當故障被偵測後，串聯補償器投入正序與負序的虛擬電感，可抑制正序與負序的故障電流。並討論正序與負序電抗對於故障電流的影響，且可根據補償器的額定，計算正序與負序電感命令。除此之外，分別在單相故障與兩相故障的情況下利用數學軟體MATLAB分析最佳化電感的投入值，以達到利用有限的輸出電壓做出最有效的故障電流抑制效果。
本論文將先詳細介紹虛擬電感的控制方法，並說明如何利用虛擬電感抑制故障電流，且分別在單相故障與兩相故障情況下，推導投入虛擬電感後對故障電流的抑制效果。最後，再利用模擬結果與實際電路操作驗證本文所提出的故障電流抑制策略。

關鍵字

串聯式補償器 ； 故障電流抑制 ； 虛擬電感

並列摘要

When voltage sag occur, the sensitive equipment with unexpected shut-downs often result in substantial economic losses, so series compensator are usually used to restore voltage during sag for improving power quality and riding through voltage sag. However, voltage restorer cannot protect sensitive loads when short circuit fault occurs at load side. A fault current mitigation strategy based on the structure of series compensator has been proposed. When the compensator is activated, it acts like a virtual inductor in the system. Not only the fault current can be mitigated effectively, but also the voltage sag problem will not occur at other feeders.
In this thesis, a fault current mitigation technique is proposed based on the concept of virtual inductor, whereas both positive and negative sequence inductor are used to mitigate fault current. When grounding fault is detected, positive and negative fault current can be mitigated by virtual inductors which is put in the system by series compensator. The selection on the value of positive and negative sequence inductors are based on the rating of converter. Additionally, the value of optimal virtual inductor are designed respectively under one phase and two phase fault. And using the value of inductor to effectively limit fault current with finite rating of converter.
In this thesis, first of all the principles of operation of the proposed that fault current mitigation technique is presented in detail, and the influence of virtual inductor on fault current is derived. Finally, the proposed fault current mitigation algorithm has been tested in simulation and is validated by experiments in laboratory.

參考文獻

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