并联换流器直流输电中换流器区故障分析及处理策略

Analysis and Clearing Action of Converter Area Fault in HVDC Transmission System with Parallel Converters

并联换流器直流输电是实现超大容量输送电能的方式之一,其要求单换流器内故障不影响到非故障换流器的正常运行。在详细分析并联换流器直流输电整流站和逆变站单个换流器区各种位置接地等故障的故障特征基础上,提出了保护动作后请求整流站换流器移相的处理策略,在有效隔离故障换流器的基础上,保持并联的非故障换流器继续运行;另外作为整流站因故无法完成换流器移相的后备,建议调整直流线路低电压保护动作延时定值为50ms。逆变站交流系统故障时,存在双换流器均发生换相失败、分担故障电流的情况,换流器过流小于直流系统参数相近的常规并联型多端直流输电系统的同类情况。

As one of the huge power transmission modes,high voltage direct current（HVDC）transmission system with parallel converters（HVDC_PC）requires that faults in one converter do not influence another non-fault converter to operate.Based on an analysis of the fault features in different fault positions and types of converter area in HVDC_PC,a clearing action requiring rectifier to retard is proposed to isolate the fault converter while maintaining the non-fault converter operation.As a backup of rectifier not to retard for some reason or other,it is suggested that the trip delay-time of direct current line undervoltage protection be set to about 50 ms.For a grounded fault on alternating current system in the inverter,it is possible for two parallel converters to share the fault current due to commutation failure.The current is less than that for multi-terminals HVDC with parallel type under the condition of similar direct current transmission system parameters.