State-of-Charge-Based Energy Management Strategy for Hybrid Energy Storage System in DC Microgrid

Abstract

Integration of photovoltaic (PV) systems increases demand for DC microgrids (DCMGs). Stability of PV-based DCMG is enhanced by integrating battery storage into it. Addition of another energy storage element, i.e., supercapacitor (SC) further ameliorates battery’s longevity and dynamic stability of DC microgrid. Combination of battery and SC is known hybrid energy storage system (HESS). Control and power sharing of battery and SC play a significant role in HESS operation. Conventional constant frequency low pass filter-based HESS control can share dynamic power between battery and SC. However, the constant and slow dynamics of HESS control affect DC bus regulation and battery’s state-of-charge (SoC). To improve dynamic performance of HESS, this paper proposes, a SoC-based variable frequency low pass filter-based energy management strategy (EMS). Proposed EMS controls power splitting between battery and SC and reduces battery’s sluggishness under necessary conditions. Proposed strategy enhances dynamic DC bus stability, battery life and utilizes SC effectively. Proposed EMS is validated with Matlab simulation and real-time digital simulation.