基于行波电流极性差异的交直流混联系统纵联方向保护方法

交直流混联系统中逆变站的换相失败使交流线路发生频率偏移,导致工频量纵联方向保护的可靠性受到影响。本文提出一种基于行波电流极性差异的交直流混联系统纵联方向保护方法,利用线路区内、外故障时,传播到两端保护的电流故障初始行波波头之间极性差异构成纵联保护。该方法仅利用电流初始行波极性差异进行方向判别,消除了电容式电压互感器无法准确传输宽频带电压信息导致保护的低可靠性问题,且利用高频电流进行计算,避免了交直流混联系统频率偏移的影响。仿真结果显示,基于行波电流极性差异的纵联方向保护方法能够准确、快速地识别单相故障和多相故障,适用于交直流混联系统。

Longitudinal direction protection method of AC/DC hybrid system based on the difference in polarity of traveling wave current

The commutation failure of the inverter station in the AC/DC hybrid system causes the frequency deviation of the AC line, which affects the reliability of the longitudinal direction protection of the power frequency quantity. A longitudinal direction protection method of AC/DC hybrid system based on the difference in polarity of traveling wave current is proposed. The polarity difference between the initial traveling wave fronts of the current fault propagating to both ends of the protection constitutes the longitudinal protection when the internal and external faults occur. This method only uses the polarity difference of the initial traveling wave of the current to determine the direction, which eliminates the low reliability of the protection caused by the inability of the capacitive voltage transformer to accurately transmit broadband voltage information. And this method uses high-frequency current to calculate, which avoids the influence of frequency offset of AC / DC hybrid system. The simulation results show that the longitudinal direction protection based on the polarity difference of traveling wave current can accurately and quickly identify single-phase faults and multi-phase faults, which is suitable for AC / DC hybrid system.