DFIG风机於电力系统冲击影响之动态模拟-台北科技大学.docVIP

高壓直流系統常見事故之研究 A Study of Common Accidents in HVDC Transmission System 陳昭榮 Chao-Rong Chen Yong-Chang Chen 台北科技大學 電機工程系(所) 台北科技大學 電機工程系(所) 台灣 台北市 台灣 台北市 Department of Electrical Engineering Department of Electrical Engineering National Taipei University of Technology National Taipei University of Technology Taipei, TAIWAN Taipei, TAIWAN 摘要 換相失敗為在每一個單橋中，當處於同一半橋中的兩個橋臂之間的換相結束後，剛退出運行的閥在反向電壓作用的一段時間內，如果未能恢復正向阻斷能力，或者在反向電壓期間換相過程一直未能完整地進行完成，在閥電壓轉變為正向時，該閥將會不經觸發而再次導通，與剛觸發導通的閥發生反換相，這個過程就是換相失敗。經由模擬結果顯示，當事故發生交流側單相短路經電阻接地和三相短路經電阻接地並不會發生換相失敗，而單相短路直接接地、相間短路、三相短路直接接地或直流側換流器內部閥體故障，則將會使換相失敗發生， 換相失敗將使得直流系統在一段時間內直流電流增大，直流電壓下降，直流輸送功率降低甚至中斷。因此分析各種故障下的電壓、電流、觸發角、熄滅角之暫態響應及調變能力，確認系統是否安全，以避免造成更嚴重之情況具有重要的意義。 關鍵詞：高壓直流系統、電力系統故障、閥體故障、換相失敗。 Abstract Commutation failures mean that in each single bridge, after commutation between two bridges which are in the same half bridge, valve which is out of motion is in reverse voltage effect for a period of time, if it can’t recovery the ability of obverse leaving off, or it can’t be completely finished during the commutation process in reverse voltage, when the valve voltage becomes into obverse, the valve will be conducted again without firing, occurs reverse commutation with the valve which is just conducted by pulse, this process is commutation failure. By the result of simulation, it won’t occur commutation failures when faults happen single phase short circuit grounded with resistance and three phases short circuit grounded with resistance, but it will make commutation failures happen when single phase short circuit grounded directly, phase to phase short circuit, three phases short circuit grounded directly or internal faults on the thyristor valve on the dc side, commutation failures make HVDC’s dc current increase, dc voltage decrease, dc power delivery decrease or even blocked during a specific time. So it has a profound significance to analyze