Oscillation Suppression Strategy for Multi-Parallel Grid-Forming Converter Systems Considering Decentralized Transient Damping
Parameter disparities in inertia and damping among parallel grid-forming converters (GFM-VSCs) induce power-frequency oscillations under varying operating conditions, potentially triggering protection misoperations and cascading disconnections. This study establishes an impedance-based small-signal model of a multi-parallel GFM-VSC system and identifies the dominant oscillation mechanisms through root locus and Bode analyses. A decentralized transient damping control strategy is proposed based on state feedback theory, incorporating angular frequency compensation and electromagnetic power compensation to enhance individual converter damping and introduce supplementary mutual damping torque. The strategy reduces angular frequency deviations across parallel units and improves system cooperativity. Lyapunov function analysis proves the correctness of the control strategy. Simulation and experimental validation confirm the feasibility and effectiveness of the proposed method. The approach addresses the limitations of centralized state-space modeling for high-dimensional systems and provides a scalable solution for multi-area decentralized control, maintaining steady-state characteristics while regulating transient behavior through parameter optimization.