逆变站交流出线保护近区故障方向判别方法

逆变站作为交直流混合电网的核心枢纽，其故障特性相较于传统同步机更加复杂。逆变站交流出线发生故障时，受逆变站故障特性影响，传统基于工频量的保护无法正确动作。通过分析逆变站交流出线两端系统故障特性差异，基于R-L模型时域微分方程算法，提出了一种新型方向元件。当逆变站交流出线发生短路故障时，直流系统侧提供的故障电流和受端交流系统提供的故障电流特性差异极大，通过计算测量电压降落和计算电压降落变化趋势的相关系数，所提方向元件可正确判断故障方向。分析表明，所提出的方向元件适用于逆变站交流出线线路保护，且在逆变站仅有一条出线的情况下仍能正确动作。仿真结果表明，该方向元件具有良好的保护性能，不受雷击、故障类型、逆变站换相失败等因素的影响。

Fault direction identification for AC line near converter at the inverter side of HVDC

The converter station is a crucial node in the AC/DC hybrid power grid and has complex fault characteristics. Traditional protection methods based on power frequency components may not respond accurately to faults on the converter station''s AC outlet, owing to converter station fault characteristics. This paper proposes a new directional element based on the R-L model time-domain differential equation algorithm and the difference in fault current characteristics between both ends of the AC outlet of the converter station. In the case of a short-circuit fault on the AC line out of the inverter station, there is a significant difference in the fault current characteristics supplied by the DC system side and the receiving AC system. By calculating the correlation between the measured and calculated voltage drop, the proposed directional element can accurately discern the fault direction. Analysis indicates that the proposed directional element is applicable to the line protection of the AC line out of the inverter station and can function correctly even when the converter station only has one line out. Simulation results reveal that this directional element exhibits excellent protection performance, unaffected by factors such as lightning strikes, fault types, and phase-change failures at the inverter station.