Collaborative Control Strategy of Dynamic Frequency Modulation and Impedance Reshaping for Islanded Microgrid Cluster Systems

This paper aims to address the stability issues caused by the absence of frequency reference for a large power grid in isolated microgrid clusters, including the accumulation of frequency steady-state deviation of the Grid-Forming Converter (GFMC)1 of the core regulation unit in response to load fluctuations, and the active power oscillation caused by the output impedance mismatch during the parallel operation of multiple GFMC2 s. A coordinated control strategy that integrates dynamic secondary frequency regulation and active impedance reshaping is designed. Within the active power control loop of the GFMCs, a dynamic frequency regulation mechanism is developed by employing a compound feedforward-compensation control strategy, enabling automatic load power sharing proportional to GFMC capacity. Simultaneously, the output impedance of the converter is dynamically reshaped via impedance model analysis combined with adaptive damping compensation. The effectiveness of the proposed strategy is validated using the MATLAB/Simulink simulation platform. In this manner, deviation-free system frequency regulation is achieved, and the equilibrium of load power sharing among multiple GFMCs is significantly improved. Moreover, active power oscillations within the system are effectively suppressed. Multi-scenario simulation tests, covering load switching, equipment faults, and plug-and-play operations, confirm that the system achieves a substantial enhancement in system stability and dynamic response performance. The proposed strategy effectively addresses the issues of frequency deviation accumulation and power oscillation in islanded microgrid clusters and enhances the system's stable operation capability and dynamic regulation performance.