Communication-Free Pulsed Power Distribution and Tracking Method for Hybrid Energy Storage System Based on Active Disturbance Rejection Control

A dc microgrid is encountering the stability issues caused by emerging pulsed power loads (PPLs). A hybrid energy storage system (HESS) helps to suppress dc bus fluctuation due to periodical power demand of PPL within a short time. A common practice is to handle transient and steady power separately with high-power-density and high-energy-density units. This article proposes a novel communication-free pulsed power distribution method for the HESS consisting of battery and supercapacitor (SC) units; the battery unit only provides dc power, while the SC unit provides an ac component of pulsed power. To track the high-frequency ac component, active disturbance rejection control (ADRC) is applied to the SC unit. Taking dual-active-bridge converters as the interfaces, a detailed design process is presented. Besides, the frequency-domain model illustrates the mechanism of dc-ac power distribution, and a comparison with proportional-integral control shows the advantage of ADRC in fast ac power tracking. With the proposed control strategy, the current surge to the battery unit is significantly reduced and the droop characteristics are unaffected when PPL works. Finally, an HESS testbench supplying 10-150 Hz 1 kW PPL is built to verify the proposed pulsed power distribution and tracking method.