SOC Balance Control Strategy for Distributed Energy Storage System in DC Microgrid

Abstract

By integrating a distributed energy storage system (ESS), a standalone DC microgrid can maintain power balance and voltage stability between distributed energy sources and loads. However, without establishing the relationship between the output power of the distributed energy storage units and their state of charge (SOC), inconsistent SOC among the storage units can occur. This inconsistency can lead to issues such as overcharging and over-discharging, significantly impacting the ESS lifespan. To address this, the paper proposes a SOC droop control scheme utilizing the arctangent function to rapidly achieve SOC balancing of the energy storage units. During the SOC balancing process, as the SOC difference between units decreases, the balancing speed also decreases. To overcome this, a variable acceleration factor is introduced in the arctangent function SOC droop control strategy. This can ensure a progressive increment in the acceleration factor as the SOC gap between energy storage units diminishes. In addition, the integration of DC bus voltage compensation control effectively mitigates voltage deviations within the bus. Finally, the paper presents and simulates a variable acceleration factor-based arctangent function SOC droop control. It demonstrates its effectiveness in achieving SOC balance and maintaining stable bus voltage during charging and discharging scenarios in distributed energy storage systems.