台灣的配電系統供電給三相負載，為了節省成本而採用兩個單相變壓器繞組以U-V連接或V-V連接，以及三相負載分配不平衡等因素，導致系統產生嚴重的三相電壓不平衡，會造成額外的線路損失及降低交流馬達的運轉效率，對設備正常運轉的影響甚劇，也會使中性線電流增加導致接地電驛誤動作引起跳脫，因此本論文提出採用多階串級H橋式靜態同步補償器來改善配電系統三相電壓不平衡的特性。本論文系統架構一係以含風/太陽能再生能源之IEEE四節點之測試饋線，採用多階串級H橋式靜態同步補償器改善系統電壓不平衡，並與多種靜態同步補償器之效能比較。本論文系統架構二係以含風/太陽能再生能源之IEEE十三匯流排系統，採用多階串級H橋式靜態同步補償器改善系統電壓不平衡，並觀察對系統中再生能源所造成的影響。本論文由模擬結果驗證提出採用多階串級H橋式靜態同步補償器於改善配電系統三相電壓不平衡的可行性。

The distribution systems in Taiwan generally use two single-phase transformers with the windings of U-V connection or V-V connection to supply three-phase loads due to cost savings. Such special winding connections can cause serious three-phase voltage imbalance that can also lead to the problems of the trip of ground relay, extra power losses of distribution lines, efficiency reduction of induction motors, etc. This thesis proposes a multilevel cascaded h-bridge static synchronous compensator (MLCHB-STATCOM) to improve the three-phase voltage unbalance in distribution systems. System configuration 1 is based on the IEEE 4-node test feeder under U-V winding connection of two single-phase transformers, unbalance of three-phase loads, and changes of transmission line ratio. System configuration 2 is based on the IEEE 13-bus feeder with PV/wind renewables under unequal loading on three phases and different winding connections of transformers. The MLCHB-STATCOM is proposed to reduce three-phase voltage unbalance and/or the power fluctuations caused by PV/wind renewables in the two studied systems. The simulation results show that the MLCHB-STATCOM can be used to effectively improve the three-phase voltage unbalance of the studied distribution systems.

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