电网电压不对称跌落下双馈风电机组转子电压分析

Rotor Voltage Analysis of Doubly Fed Induction Generator Under Unsymmetrical Grid Voltage Dips

在实现低电压穿越的过程中,双馈感应发电机(DFIG)定子始终与电网相连,电机在电网电压跌落和恢复作用下的磁链动态响应会引起转子过电压,威胁转子变流器的安全,导致低电压穿越失败。文中基于DFIG动态模型,针对电网电压三相不对称跌落,提出了根据正序和负序电网电压分别求解电机定子磁链和转子电压动态响应的方法,采用电机定子磁链和转子电压矢量轨迹图直观地描述了电机动态响应过程,并给出了转子电压在不对称跌落期间的稳态值、不同跌落和恢复时刻下的最大值和最小值。相应的DFIG仿真结果验证了所述理论分析的正确性。最后,提出了一种转子有源Crowbar电阻的设计方法。

The stator of doubly fed induction generator （DFIG） should be kept connection to the grid during the low voltage ride-through （LVRT） period. The flux dynamic response and rotor overvoltage induced by the grid voltage dip and recovery threaten to damage the vulnerable rotor converter, even cause LVRT failure. This paper uses dynamic model of DFIG, and proposes a method to analyze the motor dynamic responses respectively by use of positive and negative components under unsymmetrical grid voltage dips. The motor dynamic response is described by the stator flux vector locus and rotor voltage vector locus. The steady rotor overvoltage under unsymmetrical grid voltage is given. The maximum and minimum rotor overvoltage induced by the different time of grid voltage dip and recovery are well represented. The results of simulation to a DFIG system validate the proposed theoretical analysis. At last, a design method of the active Crowbar resistor is proposed.