基于电压相位比较的双馈风电场输电线路单相接地距离保护

基于双dq坐标系的双馈感应发电机(DFIG)暂态模型,推导了DFIG正、负序突变量阻抗表达式并研究其相角变化特征。针对DFIG突变量阻抗角变化,提出一种单相接地时故障点序电流与保护安装处序电流之间相位差的计算方法,从而得到以保护安装处电压为参考值的故障点电压和补偿电压的相角。以区内外故障时故障点电压和补偿电压之间的相位关系为依据,提出适用于双馈风电场输电线路的电压相位比较距离保护方案。仿真结果表明,所提方法不受过渡电阻、故障位置及系统运行方式的影响,能够准确判别区内外故障。

Distance protection based on voltage phase comparison for line to ground fault of transmission line connecting wind farm with DFIGs

Based on the dynamic model of the Doubly-Fed Induction Generator (DFIG) under double dq synchronous reference frames, the analytical expressions of equivalent positive and negative sequence superimposed impedances of the DFIG are derived, and their phase angle characteristics are studied. With the variable impedance angles of DFIG, the sequence currents angle difference between fault location and measurement location is described when a line to ground fault occurs, thus the phase angles of the fault voltage and the compensation voltage referred to the measured voltage are derived. Based on the phase difference between fault voltage and the compensation voltage during internal and external fault, a distance protection scheme based on voltage phase comparison is proposed for the transmission line connecting wind farm with DFIGs. The proposed scheme is validated by the simulation results, which show that it is insensitive to the grounding resistance, the fault location and the operation conditions of the wind farm, and can distinguish the internal and external fault accurately. This work is supported by National Natural Science Foundation of China (No. 51637004).