Frequency-Adaptive Repetitive Voltage Control for Virtual Synchronous Generator Inverters

Virtual Synchronous Generator (VSG)-based grid-forming inverters are widely employed to provide voltage and frequency support for enhancing power system stability in renewable-rich grids. However, their Point of Common Coupling (PCC) voltage quality deteriorates under harmonic perturbations caused by nonlinear loads, grid voltage distortions, and so on. In this paper, an adaptive repetitive voltage control strategy is proposed for VSG inverters to eliminate harmonic perturbations. The proposed method integrates a frequency-adaptive repetitive controller into the state-feedback voltage control loop to ensure accurate harmonic compensation in the presence of nonlinear loads, grid voltage distortions, and grid frequency variations. A plug-in design preserves the VSG’s inherent grid-forming capabilities while avoiding control loop redesign. Experimental results demonstrate that the proposed voltage control strategy can achieve fast, accurate, and robust PCC voltage regulation to offer voltage support and grid frequency support and provide accurate elimination of harmonic distortions under nonlinear rectifier loads, grid voltage distortions, and grid frequency variations.