Control strategy of an active crowbar for DFIG based wind turbine under grid voltage dips

This paper proposes a novel crowbar control technique and a stator voltage oriented direct power control (SVODPC strategy for the doubly fed induction generator (DFIG) used in wind power generation systems. The main difficulty for a DFIG to ride through a severe symmetrical grid voltage dip is the big transient currents induced in the rotor windings, which may damage the AC excitation converter. The proposed SVODPC is capable of suppressing the transient oscillations of the fault currents and electromagnetic torque. The crowbar protection is able to limit the peak values of the rotor currents under a preset threshold. Moreover, reactive current is injected in good time to assist the recovery of the grid voltage. Simulation results prove that with this control scheme the DFIG is able to ride through the severe grid voltage dips.