低电压穿越控制下双馈风电机组短路电流特性与计算方法

双馈风电机组(DFIG)的规模化应用使得电力系统的故障特性发生了变化,极大制约了电力系统继电保护的实施。针对现有研究未计及低电压穿越(LVRT)措施对DFIG故障特性的影响问题,对低电压穿越控制下DFIG的短路电流进行研究,重点考虑DFIG无功功率输出通过改变机端电压对机组故障输出特性的影响。着眼于DFIG定转子绕组反应、变换器LVRT控制的相互耦合,通过构建LVRT控制下的DFIG矢量模型,导出了LVRT控制启动前和启动后的DFIG短路电流表达式,从无功功率输出和LVRT控制启动延时两个方面分析LVRT控制对DFIG短路电流的影响,建立LVRT控制启动前和启动后的DFIG故障等效模型,提出考虑LVRT控制影响的DFIG并网系统短路电流的计算方法。

Characteristics and Calculation Method of Short-Circuit Current of Doubly Fed Wind Generator under Lower Voltage Ride Through

The fault characteristics of power system is being changed by the large-scale application of doubly fed induction generator (DFIG) in wind generation. Thus, the relay protection of power system is restricted. Many researches on fault characteristics of DFIG have been conducted, but the influence of low voltage ride through (LVRT) was excluded. This paper studies the short-circuit current contributed by DFIG under LVRT control, with the emphasis on the effects of reactive power on terminal voltage. The coupling mechanism between the winding reaction and LVRT control is taken into account. The expressions of short-circuit currents before and after the LVRT control were presented by constructing the vector model of DFIG operated with LVRT control. The influence on short-circuit caused by the reactive power and its trigger time under LVRT control was analyzed. The equivalent models of DFIG before and after LVRT control were then built. Finally, the calculation method of short-circuit current of a doubly-fed wind power system was proposed.