Research on Stability Enhancement Control Strategies for Grid‐Forming Inverters Under Strong Electric Grid Conditions Based on LADRC

ABSTRACT Grid‐forming inverters are essential components linking renewable energy sources to the grid, and their stability is crucial for the reliable operation of the system. Grid‐forming inverters based on traditional proportional‐integral (PI) control demonstrate good small‐signal stability in weak grids characterized by low short‐circuit ratios (SCR). However, when connected to strong grids, it often leads to sub/super‐synchronous oscillations, causing instability in the system. To enhance the grid‐forming inverter's stability under strong grid conditions, this paper employing the linear active disturbance rejection control (LADRC) strategy in place of traditional dual PI voltage‐current control loops. This study establishes positive and negative sequence impedance models of grid‐forming inverters under traditional dual PI voltage‐current control and LADRC voltage loop control using harmonic linearization methods. Based on the established sequence impedance models and Nyquist criterion, the paper identifies the reasons behind sub/supersynchronous oscillations induced by dual PI control under strong grid conditions. Stability comparisons are provided between dual PI control and LADRC control of grid‐forming inverters under different grid strengths. The comparative results demonstrate that grid‐connected inverters with LADRC exhibit superior adaptability to strong grids, demonstrating enhanced capability to suppress sub/super‐synchronous oscillations. Simulation and experimental validations confirm the effectiveness of the LADRC control strategy.