基于转子电流补偿的DFIG低频振荡抑制策略

Low Frequency Oscillation Suppression Strategy for DFIG Based on Rotor Current Compensation

双馈感应发电机(DFIG)中锁相环(PLL)的使用会引入频率耦合及低频负阻特性,导致DFIG与交流弱电网互联的振荡失稳问题。首先,建立了DFIG的多输入多输出阻抗模型,根据不同简化条件下DFIG并网系统的广义奈奎斯特曲线,揭示了不同PLL关联阻抗的影响;然后,提出了一种基于转子电流补偿的DFIG低频振荡抑制策略及其简化实施方案,所提策略可将转子电流中包含的PLL动态进行补偿,极大地减小PLL引入的频率耦合及负阻特性,从而提高DFIG在弱电网下的并网稳定性;最后,在Matlab/Simulink中建立了DFIG并网系统的电磁暂态仿真模型,仿真结果验证了理论分析的正确性及所提策略的有效性。

The phase locked loop(PLL)used in doubly fed induction generator(DFIG)system can cause frequency coupling phenomena and give negative resistance characteristics in low frequency,which leads to instability issues,especially in weak grid conditions.Firstly,the multi-input multi-output(MIMO)impedance model for DFIG system is established.And then,based on the generalized Nyquist curves of DFIG interconnected system with different simplified conditions,the influence of different PLL-related matrices is revealed,and a low freqnency oscillation suppression strategy based on rotor current compensation is proposed,which can greatly reduce the frequency coupling and negative resistance characteristics introduced by PLL,thus improving the grid-connected stability of DFIG under weak grid conditions.Finally,an electromagnetic transient model of DFIG grid-connected system is established in Matlab/Simulink,and the simulation results verify the correctness of theoretical analysis and the effectiveness of the proposed method.