Research on High-frequency Oscillation Suppression Strategy for Three-Phase Grid-forming Inverter Based on Impedance Reshaping

Analogous to the grid - connected inverter, in the utilization of a digital control system, the three - phase grid -connected inverter's output impedance will exhibit negative damping characteristics within the high - frequency band. This is attributable to the cumulative delay in the control loop resulting from sampling, calculation, communication, and other related links. This characteristic may cause high-frequency oscillation of the grid-connected system and pose a potential threat to the stable operation of the power system. In order to solve this problem, this paper first establishes the output impedance model of the three-phase grid-connected inverter considering the complete control link and delay effect. Then, based on the characteristics of the impedance model, an active damping additional link integrating capacitor current feedback and series lead correction technology is designed to realize the active reshaping of the high-frequency impedance characteristics of the inverter and effectively improve the high-frequency stability of the grid-connected system. Finally, the correctness and feasibility of the high frequency oscillation suppression strategy are verified by simulation.