双馈风电机组多机并联运行的短路电流特征及其机理

Characteristics and Mechanism of Short-circuit Currents Contributed by Doubly-fed Wind Turbines Under Parallel Operation

双馈感应发电机(DFIG)输出短路电流在组成、大小和衰减时间上与同步发电机区别较大,使得目前DFIG的故障暂态分析已成为风电并网研究的热点。然而,现有研究多以DFIG的单机并网系统为对象,由于风电场、风电机群集电系统的网络化特征,单个DFIG的暂态特性并不足以表征大量机组共同作用的整体性特征。对多个DFIG并联运行时短路电流较单机并网运行时的区别及其产生机理进行研究。基于三相电路空间矢量的基尔霍夫定律和元件特性方程的分析,通过推导DFIG的短路暂态过程,构建了DFIG单机和多机并联运行时工频、直流和转速频率分量的矢量等效电路,进而推导了DFIG短路电流及其相关性的解析式,分析了DFIG多机并联运行下短路电流的变异规律,并通过仿真验证了理论分析的正确性。

The composition,magnitude and damping time of short-circuit current（SCC）contributed by doubly-fed induction generator（DFIG）is very different from those of synchronous generator.The transient analysis of DFIG thus becomes a focus of research.However,the existing studies aim at a single DFIG.Because the internal system of wind farm has the networked characteristic,the characteristics of a single DFIG cannot cover the overall features caused by a large amount of turbines.This study focuses on the difference of SCC contributed by paralleled DFIGs and a single DFIG.The Kirchhoff law and characteristic equation of circuit component of the space vectors are firstly analyzed.The fundamental frequency,direct-current and speedfrequency vector circuits of DFIG operated alone and with other DFIGs are constructed through deducing the transient process of DFIG under the grid fault.Then the analytic expressions of the SCC and its correlation are proposed,and the variation pattern of the SCC contributed by DFIG under parallel operation is obtained.The effectiveness of the theoretical analysis is proved by simulations.