低电压穿越期间双馈风电机组稳定性分析与电流分配方法

Stability analysis and current distribution method of DFIG during low voltage ride-through

在弱电网情况下,双馈风电机组(DFIG)与电网阻抗之间会发生复杂的交互作用,若在低电压穿越期间有功、无功电流设置不当,则系统将面临失稳风险。为此,建立DFIG的小信号导纳模型,分析系统失稳机理,尤其是厘清输电线路阻抗、锁相环等因素对稳定性的影响规律。提出满足无功电流响应准则、变换器容量限制和系统稳定性约束的DFIG有功、无功电流分配原则,推导DFIG稳定运行范围,从而为弱电网下DFIG的电流指令设置提供参考。实验结果表明:有功、无功电流对稳定性的影响规律不同,与无功电流相比,有功电流对稳定性的影响更为显著,验证了理论分析的正确性,且进一步验证了所提电流分配方法的有效性。

In the condition of weak grid,complex interaction between DFIG(Doubly-Fed Induction Generator)and grid impendance may occur,if the active and reactive currents are set improperly during low voltage ridethrough,the system will face the risk of instability,for which,a small signal admittance model of DFIG is established,the instability mechanism of the system is analyzed,especially the influence rule of transmission line impedance,phase locked loop and other factors on stability is clarified.The active and reactive current distribution principle of DFIG is proposed,which satisfies the response criterion of reactive current,capacity limit of the converter and stability constraint of the system,the stable operation range of the system is derived to provide guideline for the current setting of DFIG under weak grid.Experimental results show that the influence rules of active and reactive currents on stability are different,compared with the reactive current,the influence of active current on stability is more significant,which verifies the correctness of theoretical analysis,and the effectiveness of the proposed current distribution method is further verified.