A Decentralized Control Strategy for Autonomous Transient Power Sharing and State-of-Charge Recovery in Hybrid Energy Storage Systems

This paper proposes a decentralized power management strategy for hybrid energy storage systems to achieve transient power sharing and state-of-charge (SoC) recovery simultaneously. A virtual capacitance droop control strategy with an autonomous SoC recovery loop is proposed for energy storage (ES) with fast dynamic response, and the conventional virtual resistance droop control method is employed to regulate ES with slow dynamic response. The hybrid battery/supercapacitor (SC) system is taken as an application example. With the proposed method, load power is autonomously split into high-frequency and low-frequency parts to be compensated by SC and battery. Meanwhile, SC SoC is automatically recovered and this enables continuous operation of the SC as a power buffer without mode change or performance tradeoff. A design guideline is developed to ensure desired transient power sharing dynamics and SoC recovery with negligible interactions. Both simulations and experiments are conducted to validate the effectiveness of the proposed strategy and analytical results.