A Hybrid Energy Storage System for an Electric Vehicle and Its Effectiveness Validation

A hybrid energy storage system (HESS), which consists of a battery and a supercapacitor, presents good performances on both the power density and the energy density when applying to electric vehicles. In this research, an HESS is designed targeting at a commercialized EV model and a driving condition-adaptive rule-based energy management strategy (EMS) is proposed for the HESS, which takes into account the superiority achievement of each ESS and also the protection to each ESS. The effectiveness of the HESS plus the EMS compared to the single battery case is validated by both the computer simulation and the semi-physical rapid control prototype (RCP) test bench. An electric loading equipment is adopted in the RCP experiment validation for simulating the vehicle driving cycle instead of the traditional combination of a motor and a dynamometer. Both validation results show that compared to the single battery case, the working status of the battery is stabilized by the addition of the supercapacitor in the HESS case during both the propelling and regeneration modes and the battery energy is also saved. A dynamic degradation model for the battery is adopted in order to evaluate the life cycle cost of the HESS. Results show that the HESS plus the EMS has the effect of prolonging the battery lifetime and the HESS is economically effective compared to the single battery case.