Improved Additional Damping Control for Synchronisation Stability Enhancement of Grid‐Following Converters Under Multi‐Loop Couplings Effects

ABSTRACT In the small‐signal synchronisation stability analysis of grid‐following converters (GFL), the detailed interactions among multi‐loop control mechanisms are often oversimplified or neglected, leading to significant modelling inaccuracies and potential stability assessment failures. To address this issue, this paper presents a motion‐equation‐based model for GFL converter that comprehensively incorporates multi‐loop control dynamics, including the current control loop, AC voltage control loop, DC‐link voltage control loop and PLL. Based on the proposed model, the coupling characteristics of multi‐loop control are explicitly analysed and visualised in terms of system damping. The analysis reveals that low‐frequency oscillations in GFL converters can be attributed to unintended negative damping induced by multi‐loop control couplings. To mitigate this issue, an improved additional damping control (IADC) strategy is proposed, which enhances the synchronisation stability via effectively compensating for the negative damping caused by multi‐loop interactions. Finally, the simulation and experiment studies are presented to validate the proposed analysis results and the effectiveness of the IADC strategy.