弱电网下双馈发电机输入导纳建模及稳定性分析

Input Admittance Modeling and Stability Analysis of DFIG Under Weak Grid Condition

弱电网条件下双馈风电机组控制系统与电网的交互影响目前得到了广泛的关注,传统的双馈电机变流器控制系统设计中并没有考虑电网阻抗的影响,因此该文采用阻抗分析方法分析了双馈风电变流器控制系统特性对双馈发电机并网稳定性的影响。首次在同步旋转坐标系下建立了考虑锁相环影响的双馈发电机输入导纳模型,建模过程中同时考虑了双馈发电机的电磁暂态特性和转子电流环控制器的影响。在此基础上,详细分析了锁相环和电流环控制器参数变化对双馈发电机输入导纳矩阵的影响。在所建模型的基础上对弱电网连接情况下的双馈发电机稳定性进行分析,利用广义奈圭斯特稳定判据分析电流环以及锁相环PI参数对于系统稳定性的影响,仿真结果验证了所建立模型和理论分析的正确性。

The interaction between the double fed induction generator （DFIG） control system and the grid has been paid great attention in weak grid connection condition. Traditional DFIG converter control system is normally designed without considering the impact of grid impedance. The impedance-based method is used to analyze the relationship between the converter control system and the stability of DFIG grid connected system. The model of DFIG equivalent input admittance in synchronous frame with PLL dynamics considered is given for the first time. The electromagnetic transients of DFIG and current controller are also included in the input admittance model. Specific analysis is presented on how controller parameter variations affect the input admittance matrix. By applying the Generalized Nyqusit Stability Criterion（GNC）, stability of the DFIG system connected to weak grid can be predicted with the proposed input admittance model. Impact of the current loop and PLL proportional and integral parameters on system Stability is discussed and demonstrated with the Nyquist map. Simulation results verify the validity of the proposed input admittance model and theoretical analysis.