A Method for Charging Electric Vehicles With Battery-Supercapacitor Hybrid Energy Storage Systems to Improve Voltage Quality and Battery Lifetime in Islanded Building-Level DC Microgrids

TLDR

The study proposes a method to extend the central battery energy storage system’s lifetime and improve voltage quality in an islanded building‑level DC microgrid by leveraging the supercapacitor of electric vehicles equipped with battery‑supercapacitor hybrid storage. An adaptive filtration‑based current‑sharing strategy in the microgrid’s voltage‑feedback loop smooths CBESS current by allocating high‑frequency variations to the EV charger, with the filter bandwidth tuned by a data‑driven algorithm so that only the EV’s supercapacitor absorbs these variations while its battery follows a standard CC‑CV charging profile, and the approach is validated in MATLAB/Simulink and hardware‑in‑the‑loop tests. The results show that the EV supercapacitor can coordinate with the CBESS without disrupting the EV battery’s charging profile, and small‑signal stability analysis indicates enhanced marginal voltage stability, improved transient response, and higher voltage quality.

Abstract

This paper proposes a methodology to increase the lifetime of the central battery energy storage system (CBESS) in an islanded building-level DC microgrid (MG) and enhance the voltage quality of the system by employing the supercapacitor (SC) of electric vehicles (EVs) that utilize battery-SC hybrid energy storage systems. To this end, an adaptive filtration-based (FB) current-sharing strategy is proposed in the voltage feedback control loop of the MG that smooths the CBESS current to increase its lifetime by allocating a portion of the high-frequency current variations to the EV charger. The bandwidth of this filter is adjusted using a data-driven algorithm to guarantee that only the EV's SC absorbs the high-frequency current variations, thereby enabling the EV's battery energy storage system (BESS) to follow its standard constant current-constant voltage (CC-CV) charging profile. Therefore, the EV's SC can coordinate with the CBESS without impacting the charging profile of the EV's BESS. Also, a small-signal stability analysis is provided indicating that the proposed approach improves the marginal voltage stability of the DC MG leading to better transient response and higher voltage quality. Finally, the performance of the proposed EV charging is validated using MATLAB/Simulink and hardware-in-the-loop (HIL) testing.