A hierarchical energy management strategy for battery-supercapacitor hybrid energy storage system of electric vehicle

To improve the performance of electric vehicle (EV), supercapacitor has been used as an auxiliary energy storage system for battery due to its high power density and fast charging and discharging characteristics. However, the challenge is how to coordinate or optimize these two energy sources in order to take full advantage of their strengths respectively. In this paper, a two-layer energy management strategy is proposed, namely, energy layer and power layer. From the energy layer, an optimal state of charge (SOC) for supercapacitor is determined to meet the energy demand of electric vehicle, while the power split ratio is determined between the battery and the supercapcitor from the power layer. The hybrid energy storage system with both battery and supercapacitor is modeled with Advisor and the simulation results have shown that under various driving cycles the proposed strategy is valid and effective.