Master–slave strategy based on fuzzy control for SOC recovery in the BESS FM process

Abstract Conventional units can regulate grid frequency but often face challenges such as slow response times and accelerated aging. As a solution for frequency modulation (FM), the battery energy storage system offers a promising alternative, enabling efficient frequency regulation while maintaining the state of charge (SOC) within an optimal range. This article proposes a master–slave FM strategy based on fuzzy control to facilitate SOC restoration during the FM process. Initially, the principles of FM for both control types are examined, focusing on the output characteristics of virtual sag control and virtual inertia control. Subsequently, a collaborative output approach combining sag control and inertia control is presented as the primary FM strategy, where frequency changes are analysed, and frequency deviations and SOC are regionally categorized. An adaptive regulator is then designed to dynamically allocate weights to the outputs of the sag and inertia slave FM controls. Finally, simulation results validate the effectiveness and feasibility of the proposed master–slave FM strategy. Under conditions of continuous load disturbance, the strategy demonstrates a 4.07% improvement in SOC recovery compared to conventional control strategies that coordinate outputs through sag and inertia control.