Mechanism and elimination of harmonic current injection from single-phase grid-connected PWM converters

The mechanism of harmonic current injection from single-phase grid-connected converters is comprehensively investigated. The measurable impacts from grid voltage, converter commutation, power factor, PWM modulation and control strategy are demonstrated on the harmonic current injection. According to the mechanism, a tailor-made control solution which employs a low pass voltage-loop filter and internal model principle-based hybrid current controller, is proposed to eliminate the harmonic current injection from the single-phase grid-connected converters. Experiments are performed to verify the validity of the mechanism and the proposed control method. It not only presents an effective tailor-made solution to the elimination of harmonic current injection from grid-connected power converters, but also provides a mechanism-based benchmark tool to further develop rational grid requirements on the harmonic injection levels in the grid integration of distributed generation units.