Power Management for Modular Battery Energy Storage Systems with SoC Equalization

Abstract

Modular Battery Energy Storage Systems (MBESSs) provide improved reliability, flexible power sharing, and reduced voltage stress on individual converters, thereby simplifying battery management. This paper presents a power-sharing approach that enhances overall energy conversion efficiency while maintaining State of Charge (SoC) balance and extending battery lifetime. Unlike many existing approaches, the proposed method accounts for both converter and battery losses, which become increasingly significant as the number of cells scales in grid-connected applications. The real-time optimal power-sharing ratios are implemented through a simple lookup table generated from offline genetic algorithm optimization, considering the module loss characteristics of the system. To validate the approach, a MATLAB/Simulink model of a four-module system was developed, with each module consisting of a half-bridge converter and a 10 Ah, 12.8 V $\mathbf{L i F e P O}_{\mathbf{4}}$ battery. Simulation results obtained in discharging mode under various operating conditions show that the proposed power-sharing strategy achieves up to a 3% improvement in efficiency compared with conventional SoC-based power-sharing approaches, particularly under light load conditions, while also maintaining efficiency at high load levels and enhancing overall system reliability.