Direct power control of DFIGs based wind energy generation systems under distorted 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 coordinate control strategy of the grid side converter (GSC) and rotor side converter (RSC) of the DFIG is designed to improve the overall scheme performance. The RSC is controlled based on a DPC principle to eliminate the electromagnetic torque and stator reactive power oscillations. The total active and reactive power oscillations are compensated by the GSC control to achieve constant active and reactive powers from the overall DFIG system. A current control scheme consisting of a proportional integral controller and a resonant compensator tuned at six the grid frequency is proposed to provide accurate control of the GSC current. The proposed control scheme removes rotor current regulators and the decomposition process of the rotor and GSC currents. In addition, the proposed scheme preserves the advantages of the classical DPC. 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. The performance of the proposed and conventional DPC schemes is compared under the same operating conditions. The proposed scheme results show significant improvements in the scheme performance.