Improved Control Strategy for Dc Microgrid with SOC Balance

Abstract

This study focuses on the power regulation of energy storage units in photovoltaic-based DC microgrids and proposes an improved droop control strategy centered on the equalization of the state of charge (SoC). The goal is to optimize power distribution among storage units, thereby enhancing the operational stability and coordination of the DC microgrid. First, the limitations of conventional droop control strategies are analyzed, including issues such as bus voltage deviation, SoC inconsistency among storage modules, and the risk of battery overcharging or overdischarging. To address these challenges, an SoC-based adaptive droop coefficient adjustment method is proposed to achieve faster SoC balancing. In addition, to mitigate voltage fluctuations caused by droop coefficient variations, a bus voltage compensation mechanism is introduced. Beyond these improvements, a dynamic consensus algorithm is employed to enhance communication efficiency and global SoC consistency across the microgrid system. Finally, MATLAB/Simulink simulations are conducted to verify the effectiveness of the proposed strategy under three operating scenarios: discharging, charging, and solar irradiance variation. The results show that compared with the conventional control strategy, the proposed method improves SoC balancing speed by up to 73%, while maintaining the bus voltage stably at 400 V, thereby demonstrating the superiority of the proposed approach.

Keywords: SOC balance, sag control, Energy Storage System, Dc microgrid, Voltage Compensation