An Energy Management Strategy of Hybrid Energy Storage Systems for Electric Vehicle Applications

TLDR

Current ESS in PEVs suffer from power density limits, so a hybrid system combining a battery and supercapacitor is explored, requiring energy management. The study aims to minimize EV electricity consumption while extending battery life. An optimal strategy using Pontryagin's minimum principle instantaneously allocates propulsion and regenerative braking energy between the battery and supercapacitor, and its performance is evaluated via simulation against a rule‑based approach. Simulations demonstrate that the strategy reduces electricity consumption and extends battery life compared to both a rule‑based strategy and a single‑ESS configuration across three driving cycles.

Abstract

In order to mitigate the power density shortage of current energy storage systems (ESSs) in pure electric vehicles (PEVs or EVs), a hybrid ESS (HESS), which consists of a battery and a supercapacitor, is considered in this research. Due to the use of the two ESSs, an energy management should be carried out for the HESS. An optimal energy management strategy is proposed based on the Pontryagin's minimum principle in this research, which instantaneously distributes the required propulsion power to the two ESSs during the vehicle's propulsion and also instantaneously allocates the regenerative braking energy to the two ESSs during the vehicle's braking. The objective of the proposed energy management strategy is to minimize the electricity usage of the EV and meanwhile to maximize the battery lifetime. A simulation study is conducted for the proposed energy management strategy and also for a rule-based energy management strategy. The simulation results show that the proposed strategy saves electricity compared to the rule-based strategy and the single ESS case for the three typical driving cycles studied in this research. Meantime, the proposed strategy has the effect of prolonging the battery lifetime compared to the other two cases.