Improvement of current performance for grid connected converter under distorted grid condition

This paper proposes an improved current controller to achieve a high current performance in grid connected converter under distorted grid voltage condition. The proposed control scheme is employed in synchronously rotating reference frame that consists of a conventional proportional-integral (PI) controller plus a resonant (R) controller tuned at six times of grid frequency. The complexity of the proposed control algorithm is greatly reduced because a single resonant controller is enough to eliminate effectively both negative fifth and positive seventh harmonic components in current, which are caused by distorted grid voltage. The control strategy is analyzed and design of resonant controller in discrete form will also be presented. Simulation and experimental results are presented to validate the feasibility of the proposed control algorithm.