风电接入对继电保护的影响(六)——风电场送出线路距离保护影响分析

Impact of wind farm integration on relay protection(6):analysis of distance protection for wind farm outgoing transmission line

从感应发电机基本原理出发,在转子转速旋转磁场坐标下,建立感应发电机简化三阶动态模型。从电路角度分析了风电场送出线电压、电流主频不同的机理,因此依据工频傅氏算法的相量距离保护元件的动作性能受到严重影响。利用Prony等算法分别提取保护安装处电压、电流工频及转速频率分量,可以准确测量出故障线路阻抗;基于线路时域微分方程模型的解微分方程算法距离元件不受信号频率影响。PSCAD/EMTDC仿真结果验证了分析的正确性。

Based on the basic principle of induction generator,a simplified three-order dynamic model of induction generator is established in dq rotating coordinates.The mechanism of main frequency inconsistency between voltage and current of wind farm outgoing transmission line is analyzed from the perspective of electric circuit,which affects severely the action performance of phasor distance protection element based on power frequency Fourier algorithm.Prony algorithm and some others are used to extract the power frequency component of measured voltage / current by protection and the rotor speed frequency component for accurately detecting the fault line impedance.The distance element,which employs the differential equation algorithm based on the time-domain differential equation model of transmission line,is not affected by the signal frequency.Simulative results with PSCAD / EMTDC show the correctness of analysis.