Direct power control of DFIGs connected to harmonically grid voltage conditions

This paper presents an improved direct power control (DPC) strategy of a wind turbine driven doubly fed induction generators (DFIGs) connected to distorted grid voltage conditions. A coordinated control strategy of the grid side converter (GSC) and rotor side converter (RSC) of the DFIG is designed based on DPC to improve the overall scheme performance. The RSC is controlled to eliminate the electromagnetic torque and stator reactive power oscillations, meanwhile, the total active and reactive power oscillations are compensated by the GSC controller to achieve constant active and reactive powers from the overall DFIG system. The proposed control scheme removes control loops and decomposition processes of both the rotor and GSC currents. Neither proportional-integral controller nor resonant compensator is required for RSC or GSC control. The feasibility of the proposed DPC scheme is validated by simulation studies on a 1.5 MW wind power generation system under harmonically distorted grid voltage conditions. To illustrate its effectiveness, the performance of the proposed and conventional DPC schemes is compared under fixed and variable wind speed, active and reactive power values. The proposed scheme results show significant improvements in the overall scheme performance.