有效地诊断出特高压直流输电(UHVDC)系统中的换相失败故障,对故障后采取适当的控制措施以及避免交流系统保护装置的误动作具有重要意义.在云广±800 kV UHVDC系统中,对不同故障条件下的直流线路短路故障和换相失败故障进行仿真,利用改进的形态滤波器对不同故障条件下电流的线模分量进行6尺度分解,并提取各尺度下的形态谱.结合形态能谱熵和奇异谱熵提取故障特征,定义两个故障诊断指标作为判别系统运行状态的判据,然后针对这两个指标分别设置4个阈值HE0、HE1、HS0、HS1来诊断直流系统运行状态,即正常运行、线路短路故障、换相失败故障.对不同故障条件下的线路接地短路故障和换相失败故障进行大量仿真,仿真结果表明,该方法能准确地诊断出线路接地短路和换相失败故障.%The effective diagnosis of commutation failure in UHVDC is of significance to the appropriate control mea?sures taken after failure and the avoidance of malfunction of AC system protection equipment. Based on Yunnan-Guang?dong ±800 kV UHVDC system,the short-circuit fault in DC line and the commutation failures under different faults are simulated. The aerial mode component of DC bus current is decomposed into six scales based on a modified morphologi?cal filter,and the spectral form on each scale is extracted. With the combination of energy spectrum entropy and singu?lar spectrum entropy,two fault diagnosis indexes are defined as criteria for judging the system operation state. Accord?ing to the two indexes,four thresholds of HE0 ,HE1 ,HS0 and HS1 are set to diagnose the DC system operation states,i. e.,normal operation,DC line short circuit fault and commutation failure. The DC line short circuit fault and commuta?tion failures under different faults are simulated for many times,and the simulation results indicate that the proposed method can diagnose the DC line short circuit fault and commutation failure accurately.
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