Impedance Modelling and Stability of Grid‐Connected Inverters Based on Lyapunov Function Control

ABSTRACT

Impedance‐based approaches can be employed to address harmonic stability issues in inverter grid‐connected systems. The system stability can be analysed and improved by constructing an impedance model for the inverter and then performing impedance reshaping. The Lyapunov‐Function‐based Control (LFC) strategy ensures global stability of the inverter grid‐connected system under large‐signal transient conditions. However, research on the impedance modelling and stability analysis for inverters using this method remains insufficient. To address the harmonic stability issue of the inverter based on LFC under weak grid conditions, this article first establishes a mathematical model for the inverter's output impedance. Then the influence of various parameters on the stability of the inverter grid‐connected system is analysed based on the impedance model. Furthermore, a method for impedance reshaping is proposed to improve system stability by tuning the active damping coefficient. Finally, simulations and experiments are conducted to validate the theoretical output impedance model and the proposed stability enhancement approach.