Stability Improvement Method of Inverter Based on Dynamic Decoupling of Grid Impedance

The interaction between the AC weak grid and photovoltaic inverters may introduce disturbance branches into the system. This paper establishes a small-signal model of the grid-connected system and derives the impedance model and synchronous loop model, revealing the dynamic disturbance branches and instability mechanisms caused by grid impedance. Different from traditional methods, this paper proposes a stability enhancement method based on dynamic decoupling of grid impedance using the constructed synchronous loop model. This method can decouple the dynamics of grid impedance from those of the inverter, ensuring stable operation of the grid-connected system even under wide variations in grid impedance and in extremely weak grid conditions, without transient oscillations during the transient process, and demonstrating robustness against parameter deviations. Finally, a simulation platform was built in MATLAB/Simulink to validate the effectiveness of the proposed method and to test its robustness.