Power Quality Enhancement of DFIG based Wind Turbine by Active Filter Implementation

Doubly fed induction generator (DFIG) is one of the most preferred wind energy conversion system (WECS). Under grid connected DFIG system operation, the non-linear loads connected to the system draw harmonic currents which distorts the grid injected currents. This paper proposes an active filtering technique so as to compensate the harmonic currents drawn by these non-linear loads. The proposed method produces harmonic currents which neutralizes the harmonic currents required by the non-linear load. A new vector control strategy is proposed for the grid side converter which produces the additional harmonic currents in addition to the transfer of slip power. This results in distortion of the grid converter current but the grid current remains undistorted and total harmonic distortion (THD) is reduced. The harmonic isolation of the load currents as required in the proposed vector control strategy is achieved by self-tuning filters (STF). The DFIG model along with the control strategy is designed using MATLAB/Simulink environment and the results validates the proposed control strategy.