A simplified consensus-based distributed secondary control for battery energy storage systems in DC microgrids

DC microgrids have become a promising solution for efficient and reliable integration of renewable energy sources (RESs), battery energy storage systems (BESSs) and loads. To simultaneously achieve average voltage regulation, accurate current-sharing and state-of-charge (SoC) balance, at least two state variables need to be transmitted between neighboring BESS nodes in conventional distributed secondary control. In this paper, a simplified consensus-based distributed secondary control for BESSs in DC microgrids is proposed with only one virtually defined state variable being transmitted, where a cascaded control framework consisting of an SoC controller and a voltage controller is used to regulate DC bus voltages. This virtual state variable combines BESS SoC and its converter output current, there is no need to change the control law when BESSs switch between charging/discharging modes. Once SoCs are balanced, SoC controller works as a current controller. With the proposed control strategy, the number of transmitted state variables and the complexity of controller design are significantly reduced. Stability and steady-state analysis are also conducted to confirm the effectiveness of the proposed control strategy. Finally, Simulink simulation and hardware-in-loop tests are presented to validate the proposed control strategy.