Comparison of energy management strategies of a battery/supercapacitors system for electric vehicle under real-time constraints

The paper deals with real-time energy management strategies for a hybrid energy storage system including a battery and supercapacitor for an electric vehicle. Besides efficiency concerns, a key issue for real-time applications is ensuring safe operations for the considered system. In such a system it is mandatory to limit the supercapacitor voltage by the energy management strategy to comply with efficiency and safety constraints. An optimisation-based strategy (λ-control) and a rule-based strategy (filtering) are compared in this paper. The active limitation of the supercapacitor voltage is ensured in both strategies. Experimental results show that the two strategies have equivalent performances under real-driving cycles not known in advance. A difference of 2% between the strategies on the battery current root mean square value is shown. By varying the desired supercapacitor voltage range, the results show that the λ-control is better-suited for a high supercapacitor voltage range whereas the filtering gives the best performances for a low supercapacitor voltage range.