计及不同电网电压跌落程度的双馈风电机组定子电流分析

Stator current analysis of doubly-fed induction generators considering different grid voltage dip levels

双馈风电机组在机端电压跌落程度不同的情况下会表现出不同的暂态特性,随着风电机组的大规模并网,其故障暂态特性对于电网的安全稳定运行具有重要意义。以对称故障为例,基于双馈感应发电机的转子电压方程,采用统一方法分析了电网故障导致的不同机端电压跌落程度下双馈风电机组的定子电流。在机端电压严重跌落时。分析并推导了投入撬棒保护电路情况下双馈感应发电机定子电流的表达式。而在机端电压非严重跌落时,在考虑转子侧变流器控制系统对定子电流的影响的基础上,定性地分析了双馈感应发电机定子电流动态变化过程。通过仿真进一步分析了机端电压不同跌落情况下定子电流的变化规律并且验证了所推导表达式的正确性。

Doubly-fed induction generators （DFIG） has different transient characteristics under different generator terminals voltage dip levels. The analysis of the fault transient characteristics is very important to the grid security and stability against the background of large-scale wind generation on power grid. This paper takes asymmetrical voltage sag occurred at the terminal as an example. Based on the rotor voltage equations, the doubly-fed wind power generator fault current is analyzed under different generators terminal voltage drop levels in unified method. In the case of severe voltage drops in generator terminals, the transient characteristics are analyzed considering the crowbar protection insertion. If the terminal voltage drops mildly, the solution of limiting and calculating the short-current has to consider the influence of the control system and the stator current dynamic process is analyzed qualitatively based on the control system. Finally the paper further analyses stator current variation under different terminals voltage dip levels and validates the short-circuit expressions by simulations.