Inverter harmonic perturbations rejection in renewable energy conversion systems applying a super-twisting algorithm

Grid background and dead-time harmonic perturbations pose challenges in maintaining power quality and stability in the grid integration of renewable energy conversion systems. Therefore, a super-twisting algorithm with the ability to reject harmonic perturbations on three-phase grid-tied inverters is proposed. The algorithm design is related to dead-time and grid background harmonics so that robust performance is achieved under these perturbations. To highlight the advantages of the proposed algorithm, it is compared against proportional-integral (PI) control in several dead-time and grid background harmonic sweeps. The maximum inverter current distortion obtained with PI control in simulation is 15.53%. However, by using the proposed algorithm instead, the maximum current distortion is reduced to 1.8%. Dead-time is experimentally swept by using a permanent magnet motor as a harmonic-free grid. Experimental results of grid background harmonics are obtained by injecting reactive energy into a grid with 2.19% voltage distortion. When PI control is used in the experimental setup, the maximum inverter current distortion obtained is 11.4%. However, with the proposed algorithm, the maximum current distortion is reduced to 1.5%, which complies with the standard IEEE 1547-2018.