Adaptive Control Design for Autonomous Operation of Multiple Energy Storage Systems in Power Smoothing Applications

Energy storage systems (ESSs) are becoming indispensable components in electric power systems. They are used for energy scheduling, power/voltage smoothing, load shifting, as well as for emergency power supply. The most common control method for power/voltage smoothing is based on a high-pass-filter (HPF) structure. It generates the power reference according to the fluctuating power and provides a stabilization effect. The power and energy supplied by ESSs are majorly configured by the cutoff frequency and gain of the HPF. Considering the operational limits on ESS state-of-charge (SoC), this paper proposes an adaptive cutoff frequency design method to realize communication-less and autonomous operation of a system with multiple distributed ESSs. The experimental results demonstrate that the SoCs of all ESS units are kept within safe margins, while the SoC level and power of the paralleled units converge to the final state, providing a natural plug-and-play function.