双馈型风电场并网短路电流特性研究

Research on Characteristics of Short-Circuit Current of DFIG Based Wind Farm

摘要: 以双馈型风力发电机为主的风电场在电力供应中占有越来越大的比重。双馈感应发电机输出的短路电流特性与同步发电机具有较大区别，目前双馈风电的故障暂态分析已成为风电并网的研究热点，但主要集中于单个机组并网系统方面。本文首先基于复频域分析了单台双馈风电机组的短路暂态过程，建立双馈型风电场暂态期间的工频、直流和转速频率分量的等效电路，对双馈型风电场的短路电流变化规律进行研究。推导出风电场中单台风电机组的短路电流增量表达式，基于短路电流的增量利用补偿增量的方法推导出双馈风电场的短路电流计算式。仿真验证了风电场内部的短路电流变化规律和解析表达式的准确性。

Abstract: Wind farms consisting mainly of doubly-fed induction generators occupy more and more proportion in power supply. There do exist big differences of output short-circuit current characteristic between the doubly-fed induction generator and the synchronous generator. Research about the fault transient analysis of doubly-fed induction generators has become a hotspot; however, current research mainly focuses on the grid-connected system with single generator. This paper analyzes the short-circuit transient process of single doubly-fed induction generator in complex frequency domain and establishes the equivalent circuits of fundamental frequency, DC and rotor- speed frequency components in transient process respectively to study the changing regularity of short-circuit current of doubly-fed wind farms. Then this paper deduces the expression of short- circuit current increment of single generator in wind farm, and based on this, this paper further uses the improved weighted method to deduce the calculation formula of doubly-fed wind farm. Accuracy of the changing regularity of short-circuit current and the calculation formula is verified through simulation.