傳統風力發電系統多未針對風力發電機輸出端執行功率因數修正，導致風力發電機輸出端功率因數較低之缺點。為改善此一缺點，本文提出具三相功因修正風力發電轉換系統，藉由提高風力發電機輸出端功率因數，達到提高風力發電效率及減少風力發電機機械應力之目的。
系統包含三相功因修正電路、雙向充放電電路及全橋變流器。系統前級架構為昇壓型三相功因修正轉換器，轉換器輸入側對風力發電機輸出三相電源執行功因修正，同時將風力發電機輸出電壓昇壓以供後級全橋變流器進行市電併聯。雙向充放電電路於本文作為備用電源，風力發電機電能足夠且電池沒電時，對電池以兩階段式充電法進行充電；當市電端異常，系統與市電端切離，風力發電機電能不足時，雙向充放電電路以放電模式持續供電至交流負載端，提高系統供電穩定度。系統後級全橋變流器，將前端三相功因修正轉換器所擷取之風力發電電能轉為交流饋入單相市電，同時以擾動觀察法作為系統最大功率追蹤轉換器。
硬體實作本文以1.2kW風力發電模擬系統作為輸入源，於不同風力發電機輸出電壓頻率下三相功率因數值可由原來0.71修正至0.94~0.96；全橋變流器與單相110Vrms,60Hz市電併聯，市電端功率因數0.991，電流諧波因數8.64%，系統整體最高效率85.5%。實作結果驗證本文提出之三相功因修正轉換器確可有效提高風力發電機輸出端功率因數值，所建構之全橋變流器與雙向充放電轉換器亦可正常操作於風力發電機最大功率輸出點附近。

Most of the traditional small wind generation conversion systems do not possess the function of power factor correction (PFC) on the generator output side. As a result, the power factor at the generator output is much lower. To ameliorate the problem, this thesis proposes a three-phase wind power conversion system with the function of PFC. The power factor of the wind generator output can thus be improved to increase the efficiency the wind generator and reduce the mechanical stress on the wind generator.
The system consists of three-phase PFC converters, a bi-directional charge/discharge converter, and a full-bridge inverter. The front stage includes three Boost converters for each of three phases, respectively, to raise the generator output voltage from a full-bridge diode rectifier and conduct the PFC od each phase, simultaneously. The boosted DC voltage is then used for the input of the full-bridge inverter for grid connection. Bi-directional charge/discharge converter works as a standby power source. When the power of the wind generator is sufficient and the energy of battery is low, the battery will be charged via a two-step charge scheme. As the system is disconnected from the grid and the wind generator power is low, the bi-directional converter will discharge to supply AC power to the load to improve the reliability of power supply. The full-bridge inverter transfers the DC voltage of the three-phase Boost converters into the single-phase AC grid. In the meantime, the perturbation and observation method is used for the maximal power tracking (MPPT).
To verify the approach proposed in this thesis, a motor-driven 1.2kW wind generation simulation system is adopted. The simulated and experimental results show that under different wind speeds, the power factors of the three phases of the generator can be corrected into 0.94-0.96 from the original 0.71 without PFC. As the full-bridge inverter is connected to the 110Vrms, 60Hz grid, achieved are the power factor of 0.991, current total harmonic distortion (THD) of 8.64% and the highest overall system efficiency of 85.5% for the wind-generation system. The proposed three-phase PFC converters have been verified through the experimental results that the power factors of the wind generator can be effectively and the full-bridge inverter and bi-directional charge/discharge converter can also be operated close to the maximum power point of the wind generator.

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