Distributed Secondary Control of Battery Storage Systems in DC Microgrids with A Virtual State Variable

Abstract

<p>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. This paper proposes a distributed secondary control for BESSs in DC microgrids with the information of only one virtually defined state variable being transmitted. This virtual state variable combines the BESS converter output current and SoC, and a new voltage controller together with a new consensus-based current and SoC controller are designed all based on its information. Further, there is no need to change the control law when BESSs switch between charging/discharging modes with the designed current and SoC controller. Once SoCs are balanced, it works purely as a current controller. Stability and steady-state analysis are conducted to confirm the effectiveness of the proposed control strategy. Finally, three case studies assisted with hardware-in-loop (HIL) real-time tests are presented to validate the proposed control strategy.</p>