根據文獻的記載，92%的工廠設備停機的問題與電壓驟降有關。當電壓驟降發生，使工廠內的生產設備停擺，會造成巨額的經濟損失。為了建立高品質的電源，電壓驟降補償器因此被廣泛使用。以反流器為基礎利用偶合變壓器串聯線路的串聯式電壓驟降補償器是保護敏感性負載之最符合經濟效益的解決方法。
文獻中採用閉迴路控制系統來增加系統的主動式阻尼值和提高系統穩定度。常見的閉迴路控制器直接執行控制或在靜止框下做運算。非在同步框下的閉迴路控制器有較差的強健性和較差的準確度。本文提出的狀態回授控制器有很高的擾動抑制能力，能有效提高電壓驟降補償器的效能。
多數的工業設備前端會加上負載變壓器將市電端與負載端隔離，可保護設備運作和人員的安全。當發生電壓驟降時，會造成負載變壓器磁通鏈偏移，在電壓回復瞬間容易因磁飽和而發生湧浪電流。瞬間的湧浪電流對於電壓驟降補償器造成很大的負擔。本文提出的磁通偏移補償機制可有效的抑制負載變壓器的湧浪電流。
本文將提出較好特性的控制器和磁通偏移補償器。將會詳細介紹控制器設計原理並討論系統對於負載電流的擾動抑制特性，利用模擬和實驗結果印證理論觀點。

Survey results suggest that 92% of the break at industrial equipment is voltage sag related. When voltage sag happens, the shuts down of situation in factories will result in substantial economic loss. To build a high quality of power supply, the voltage sag compensator is applied. The compensator based on transformer-coupled series-connected voltage source inverter, is among the most cost-effective solution to protect sensitive loads.
In previous studies, closed loop controllers are used to improve active damping and to get better stability of system. These common controllers operate directly in the time domain or in stationary frame. Without transform into the synchronous frame, the controllers have less robustness and less accuracy. This thesis proposes a state feedback controller has very high disturbance rejection capability to improve the performance of the voltage sag compensator.
The load transformers which protects the plant operation and staff’s safety are usually series connected to sensitive equipments for isolating the power supply. When voltage fault happened, a DC offset will occur in the flux linkage of load transformer. The core saturates at the voltage restored and then the inrush current happened. As a result, voltage sag compensator will suffer from the significant the inrush current. The flux offset compensation mechanism is also proposed to mitigate the inrush current of the load transformer.
This thesis proposed better performance controller and flux offset compensator. The operation principles and the disturbance rejection capability of the controller are presented in detail. Simulations and experimental results validate the proposed approach.

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