本論文介紹了傳統被動、主動式孤島偵測方法，並推導其非檢測地帶(NDZ)，被動法雖然檢測方便但其NDZ過大，而大部分主動法以注入各種形式的擾動訊號為原則，將造成系統諧波失真，因此提出基於正回授原理的孤島偵測方法，在系統進入孤島時放大其電壓、頻率的飄移量，使共同耦合點的電壓、頻率突破偵測條件,系統由電流控制自主切換至電壓模式。在加入正回授孤島偵測架構的系統中，無論是否進入孤島，偵測機制都試圖擾動系統，如果偵測架構中的增益太大反而會破壞系統穩定度，造成誤偵測；反之，如果正回授孤島偵測架構中的增益太小，故障發生將導致時孤島偵測失敗或偵測時間過長，因此本文透過動態方程式建立系統小信號模型，分析在加入正回授孤島偵測架構時系統的穩定度，以權衡孤島偵測性能與系統穩定度，進一步討論系統在固定輸出功率下，調整偵測架構中的增益值，觀察系統根軌跡求出增益臨界值。最後，以Simulink模擬孤島事故發生，實驗設計在轉換器輸出功率等於負載功率的情況下，討論未加入偵測架構與加入偵測架構的例子，並在時域下分析正回授偵測架構增益的臨界值，再與頻域分析出的臨界值做對比，驗證穩定度分析的正確性。

The thesis introduces passive island detection methods and active island detection methods, and further derives their non-detection zone (NDZ). The advantage of passive island detection methods are convenient to perform; however, they have the larger NDZ. As for active island detection methods, it is usually performed by injecting different kinds of disturbance signals which can make harmonics distorted. Based on the positive feedback principle of the island detection, amplifying the offset of voltage and frequency when the islanding event happened so that the voltage and frequency of point of common point can be up to the detection condition and then enables the system to automatically switch from current control to voltage control. Noted that the disturbance signal would continuously inject to the system so that ill-designed positive gain easily makes the system switch accidentally. In contrast, if the positive gain is too small, the system can not switch at the proper timing since it would take much time to fulfill the detection. Therefore, in order to make the positive gain well designed, analyze the small signal model through the dynamic equation and then find out the boundary of the positive gain by root locus. At the end of the thesis, simulate respectively the system with island event happening with detection structure and without detection structure by Simulink under the situation that the converter delivers the whole power to the load. Analyze the boundary of the positive gain in real time and then compare with the boundary of the positive gain in frequency domain to verify the stability.

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