双馈风力发电机机端三相短路电流分析

Analysis of terminal three-phase short-circuit current of doubly-fed induction wind generator

为研究双馈风力发电机的低电压穿越问题以及风电场的继电保护问题,分析了双馈风力发电机在空载同步转速下机端发生三相短路时定、转子短路电流的近似表达式。在此基础上,从双馈风力发电机内部的电磁关系出发,分析了电压跌落程度、无功功率、转速等运行状态对双馈发电机短路电流的影响,并以0.85 MW双馈风力发电机直接接入电网为例进行仿真研究,其结果验证了双馈机机端发生三相短路时定、转子电流的暂态特性,由此也为研究双馈机低电压穿越能力及风电场继电保护问题提供了理论依据。

In order to study low voltage ride through of doubly-fed induction wind generator and relay protection of wind farm, this paper analyzes the approximate expression of short-circuit current of stator and rotor when terminal three-phase short-circuit occurs at the no-load synchronous speed. On the basis of the analysis, the paper analyzes the influence of voltage sag, reactive power and speed on short-circuit current from the electromagnetic relation in- side generator, and simulates the generator taking the example of 0. 85 MW doubly-fed induction wind generator par- alleled in the grid. The result verifies that the transient characteristics of stator, rotor current when terminal three- phase short-circuit occurs and thereby provides theoretical evidence for low voltage ride through of doubly-fed in- duction wind generator and relay protection of wind farm.