由於風速不穩定之特性，風力發電機在擷取風能時，必須具有調速功能以達到高輸出效率，從而衍生出最大功率追蹤之需求。然而當系統處於高風速狀態時，其風能極為可觀，若超過額定風速以上，系統須具備過載保護功能，以避免元件損壞。
本論文所提出之永磁式可變繞組發電機具高效率及高功率密度等優點，利用切換繞組改變發電機特性，無須藉由葉片旋角調整或電力控制，即可在額定風速以下達成準最大功率輸出、額定風速以上以定功率或定電壓輸出，故可用於系統之保護。基於容量及安全因素，一般風力發電機操作範圍有限，例如僅涵蓋最大功率控制區段，以及極小或無定功率控制區段。因此本論文利用變繞組調整發電機特性，在機械結構強度允許下，可延伸其定功率區段之範圍，且維持發電機於額定功率附近操作。本論文重點在於探討變繞組發電機之特性、適當之繞組匝數比、發電機感應電動勢常數計算法則，及繞組切換對輸出影響與特性。最後，透過實驗驗證變結構發電機之性能，包含準最大功率控制、定功率、定電壓輸出。

Due to the unstable nature of wind power, it is necessary for wind turbines to regulate speed for better generation efficiency. Therefore, the maximum power point tracking ability is required. For high wind speed carrying large power beyond rating, the power absorbed by the system should be limited to avoid component failure. This implies that system protection is needed at high wind speed.
In this thesis, a high efficiency and high power density permanent- magnet generator with winding changeover is applied to wind turbines. The generator can regulate its own characteristics to match the required operating point for a wide wind speed range without the need of blade pitch control or complex power electronics. The maximum power point tracking under rated wind speed and the constant power/voltage output beyond can be achieved by the proposed technique. Due to the capacity and safety concern, the operation range is generally limited for common wind turbines; e.g., very small or even no constant power region. The proposed method can extend the constant power region for a wide speed range as long as the mechanical strength is sufficient. Therefore, the generator characteristics, winding design, generator design criteria and windings witching effect are discussed in this thesis. Experiments are conducted to verify the capability of maximum power control and the constant power/voltage control.

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