考虑直流电流变化的HVDC系统不对称故障换相失败分析

目前高压直流输电系统逆变侧发生不对称故障时,采用最小关断角判别法判别换相失败,其研究仅考虑电压因素,预测效果不理想.针对此问题,通过对换相失败机理和影响因素的分析,认为直流电流上升与交流电压下降均会使关断角减小,将直流电流与交流电压解耦,得到一个仅含电压变化率的逆变侧关断角表达式作为判据.该判据可依据对直流线路和逆变侧...

Analysis of asymmetric fault commutation failure in an HVDC system with DC current variation

At present,when an asymmetric fault occurs on the inverter side of an HVDC transmission system,prediction is not that effective using the minimum turn-off angle discrimination method,which only considers the voltage factor.To solve this problem,based on the analysis of the mechanism and the influencing factors of commutation failure,it is shown that both the rise of DC current and the reduction of AC voltage can make the turn-off angle decrease.Therefore,by decoupling the DC current and the AC voltage,an expression of the inverter side turn-off angle only related to the changing rate of voltage is obtained.This is taken as the criterion.This criterion can be used to calculate the critical voltage changing rate that leads to commutation failure based on the operational parameters of the DC line and the inverter side.In the process of commutation,when the changing rate of the system voltage is less than that of the critical voltage,the system has a greater risk of commutation failure.A CIGRE HVDC model is built based on the PSCAD/EMTDC software,and the simulation experiments of single phase ground fault with different transition resistance are carried out.The test results verify the validity of the proposed method.