Research on Harmonic Suppression Method of Terminal Grid Based on Virtual Impedance

Active filters are widely employed as effective tools for suppressing harmonic components caused by non-linear loads in terminal grid power systems. However, the efficacy of these filters is limited, resulting in increased operational expenses. Based on Virtual Impedance Harmonic Suppression (VIHS), this paper proposes a novel control method for addressing harmonic issues in terminal grids. By adopting a dq-axis control structure, the grid-connected system using the VIHS control method and the working principle are given. Furthermore, the voltage harmonic suppression coefficient at the point of common coupling (PCC) is defined to evaluate the harmonic suppression capability of VIHS method. Due to the existence of low-order harmonics and inductive loads, the Resistive-Inductive Virtual Impedance (RIVI) is identified as the optimal combination for actual working conditions, and the impact of RIVI control parameters on harmonic suppression is analyzed. Finally, the proposed VIHS method is evaluated through simulations and experiments, and the experimental results indicate that the VIHS control method effectively reduces harmonic components of the PCC voltage.