基于转子串电阻的DFIG低电压穿越优化控制策略

Optimal Control Strategy for Low Voltage Ride-through of Doubly-fed Induction Generator Based on Rotor Series Resistance Circuit

针对双馈感应风力发电机组(DFIG)的低电压穿越(LVRT)问题,在分析现有转子串电阻电路基础上,考虑限流电阻阻值对低电压穿越期间DFIG瞬态性能的影响,权衡转子电流、转子电压、无功功率、电磁转矩间的关系,对限流电阻阻值的选取原则进行了优化;转子串电阻电路退出但电网电压未恢复时转子侧变流器的功率协调控制策略得到改善;在此基础上,利用变流器对DFIG的控制灵活性,提出一种无需定子磁链观测且控制算法简单的换流器改进控制策略。本文所提的LVRT优化控制策略在提高DFIG瞬态性能的同时兼顾了系统暂态稳定性。

Aiming at the low voltage ride through problem of doubly fed induction generator(DFIG),based on the analysis of the existing rotor series resistance circuit,considering the influence of the resistance of the current-limiting resistor on the transient performance of DFIG during low voltage ride-through,the principle of selecting the resistance of the current-limiting resistor was optimized by weighing the relationship between rotor current,rotor voltage,reactive power and electromagnetic torque;The power coordination control strategy of rotor side converter was improved when the rotor series resistance circuit was out of operation but the power grid voltage had not been restored.On this basis,by using the control flexibility of converter,an improved control strategy was proposed,which didn’t not need stator flux observation and the control algorithm was simple.The simulation results verified the correctness of the theoretical analysis.The proposed low voltage ride-through optimization control strategy improves the transient performance of DFIG and balances the transient stability of the system.