基于故障电流积分比的直流配电网极间短路选线方案

A Method of Pole-to-Pole Fault Selection for DC Distribution Networks Based on the Ratio of Fault Current Integral

柔性直流配电系统发生极间短路故障后,系统短路电流大,对系统安全稳定运行产生威胁,同时考虑到电力电子器件的耐受能力,换流器将会闭锁,导致故障信息量减少,对保护方案的速动性和可靠性提出了很高的要求。针对此问题,文章首先分析了直流线路极间短路故障电流特性,然后揭示了故障时区内外故障电流曲线的积分差异,最后提出基于线路故障电流积分比的极间短路选线方案。在实时数字仿真器(real time digital simulator,RTDS)上搭建基于模块化多电平换流器的直流配电网仿真模型,验证了所述方案的有效性与适用性,具有较好的耐受过渡电阻和抗噪能力。

When a pole-to-pole short-circuit fault occurs to the DC distribution system,the short-circuit current is high instantly,which threatens the safe and stable operation of the system.Meanwhile,given the tolerance ability of power electronic devices,the converter will be locked,which leads to reduction of the fault information.The protection scheme becomes an important factor restricting the development of DC distribution network.To solve this problem,firstly,the characteristics of the fault current curve of the flexible direct line after the pole-to-pole short-circuit fault are analyzed,and then the integral difference of the fault current curve inside and outside the fault time zone is revealed.Finally,a scheme of pole-to-pole short-circuit line selection based on the integral ratio of line fault current is proposed.The simulation model of the DC distribution system based on modular multilevel converter(MMC)is built on the real time digital simulator(RTDS)to verify the effectiveness of the scheme.