Elimination of voltage harmonics in a stand-alone DFIG using a PI-R controller in the fundamental reference frame

This paper develops a harmonic compensation approach for the stator output voltage of a stand-alone doubly fed induction generator (DFIG) feeding a nonlinear (diode rectifier) load. This load type is characterized by a nonsinusoidal stator voltage consisting of severe harmonic components, fifth and seventh ones, which deteriorate the performance of other loads connected to the DFIG. The aim of the proposed compensation method is to eliminate these harmonics in order for the DFIG to deliver a pure sinusoidal stator voltage. To this end, the proposed compensation method is investigated in the fundamental synchronous rotating reference frame based on a proportional integral (PI) plus a resonant current controller, which is tuned at sixth resonant frequency. Therefore, the proposed control scheme has capability of eliminating both fifth and seventh harmonics without decomposing 5^th negative sequence and 7^th positive sequence components of the measured rotor current. The whole control scheme is implemented in the rotor-side converter (RSC). The proposed method was tested by simulations and experiments with 2.2kW DFIG feeding a nonlinear load to verify the feasibility and effectiveness in terms of harmonic compensation performance.