双馈风电场的频率特性对距离保护的影响

Impact of Frequency Characteristics in Wind Farms Based on Doubly-fed Induction Generators Wind Farm on Distance Protection

基于双馈的风力发电场送出线路发生故障时,风力发电机的短路电流的特性与常规电力系统短路电流特性有明显的差别,主要表现在短路电流可能非工频,这种特性使得利用工频傅式算法进行信号的基频相量的提取和计算不正确。为了深入分析双馈风电场短路电流的这种特性,文中将结合双馈风电场的等效电路,从理论上分析送出线路故障时,风电场侧电流、电压的频率主要成分,并通过频谱分析进行验证。根据风电场侧电流、电压的频率不一致的特性,在PSCAD中仿真分析该种特性对送出线路上传统距离保护的影响。通过对某地区风电场仿真的实验结果可知,短路电流偏移工频,使得基于傅里叶工频算法的传统距离保护不能准确地测得阻抗,从而造成距离元件的误动作。

When a fault occurs in wind farms based on doubly fed induction generators（DFIG）, the characteristics of DFIG short-circuit current is differences from conventional power system, which is mainly not power frequency, and makes pitch extraction and calculation incorrect in constant frequency-fourier method.For understanding of the characteristic of short circuit current for doubly-fed wind farm, the paper is combined with the equal circuit of DFIG wind farm, which analyses the frequency components of short circuit voltage and current with the fault, which the result is validated by the pectrum analysis technique. Following the frequency＇s feature of voltage and current, simulations based on PSCAD is made to verify the adaptive failings of distance protection in wind farms. Through the simulation of wind farms in actual situation, the short-circuit current offsetting constant frequency, which makes traditional distance protection based on Fourier power frequency algorithm does not accurately measure the impedance resulting in the malfunction of the component.