Aging-Based Controller for Hybrid Energy Storage System in Off-Grid Intermittent Renewable Energy Mini-Grids

Deployment of battery system (BS) together with supercapacitors (Scs) in off-grid intermittent renewable energy mini-grids(IREMGs) is crucial to prolong the lifespan of the BS. There are different control strategies utilized to split power between BS and Sc in BS–Sc hybrid energy storage system (HESS). This study proposes an aging-based controller for lithium-ion battery(LB)–Sc HESS in off-grid IREMGs. Power management system (PMS) for the controller, which is based on the aging status of the energy storage systems (ESSs), is implemented through embedding a frequency-based control (FBC) strategy in a rule-based control strategy (RBC). The controller is validated by performing many simulations, which were carefully designed to activate different controller limits. Simulation results, in general, show that the proposed controller is capable of dynamically splitting power across the LB–Sc HESS based on their aging states. Additionally, results indicate that the aging-based controller slows aging rate of the faster-aging ESS so that in the long run, both LB and Sc end-of-life times converge. Furthermore, the aging-based controller was compared with a conventional RBC–FBC controller. Results show that the aging-based controller reduces capacity degradation rates of the LB and the Sc by 2.29E-06%/s and 3.56E-06%/s, respectively, more than the conventional controller. Also, both controllers show that their low-level control systems are capable of tracking reference currents. Finally, the study recommends experimental validation of the designed aging-based controller.