逆变侧交流系统三相短路时直流系统贡献短路电流的机理和计算方法研究

Mechanism and Calculation Method Study of DC System Contributed Short-Circuit Current With Three-Phase Short-Circuit Fault on Inverter Side

随着直流输电系统的迅速发展,能否忽略直流系统对短路电流的贡献成为一个亟待解决的问题,国际电工委员会把研究三相交流系统短路故障时直流输电系统对短路电流的贡献列入了5年工作计划。针对这一问题,研究了交直流混联系统中逆变侧交流三相短路故障后,直流系统发生换相失败的暂态过程;分析了直流系统向交流侧贡献短路电流的机理和特性;得出了当直流输送功率较大时不能忽略直流贡献短路电流,且只影响短路电流峰值的结论;给出了一种基于分段函数的直流系统贡献短路电流的实用计算方法。最后通过仿真计算验证了文中所给出的机理和计算方法的正确性。

With rapid development of HVDC systems,it becomes important to determine whether DC system contribution can be ignored in short circuit（SC） current calculation.Study of DC system contributed SC current for AC-side fault is included in five-year work plan of International Electrotechnical Commission.This paper investigates transient process of inverter commutation failure with inverter-side three-phase fault and analyzes mechanism of DC system contributed SC current.It is concluded that if DC transmission capacity is large enough,then DC system contributed SC current cannot be ignored and it only affects SC peak current.A practical calculation method is proposed.Simulation results verify validity of the proposed mechanism and calculation method.