In view of the problems that traditional crowbar protection is difficult to simultaneously suppress rotor current and DC bus voltage as well as absorb reactive power during low-voltage ride-through. This paper proposes a control strategy of multi-stage crowbar switching and reactive power compensation. During the fault period, the crowbar resistance is adjusted in real time by grading the crowbar, so as to achieve the purpose of suppressing the rotor overcurrent and DC bus overvoltage. At the same time as the multi-stage crowbar is put into operation, the GSC adopts the reactive power compensation strategy, so that the fan can provide certain reactive power support to the power grid. On this basis, the change of rotor flux linkage after the crowbars at all levels are put into operation is analyzed, analytical expressions for the stator and rotor short-circuit currents upon the activation of each crowbar stage are derived, and the resistance value for each stage is subsequently set. Then, the short-circuit current of GSC is analyzed according to the reactive power compensation strategy, and then the influence of multi-stage crowbar protection access and GSC additional reactive power compensation strategy on DFIG reactive power characteristics is further analyzed. Finally, the effectiveness of the proposed control strategy and the correctness of the short-circuit current expression are verified by simulation.

wind power  /  double fed induction generator  /  short circuit current  /  low voltage ride through  /  multi-stage crowbar  /  reactive power compensation