Sizing of Battery/Supercapacitor Hybrid Energy Storage System for Electric Vehicles

In a hybrid energy storage system, the battery is the primary source supplying energy for electric vehicles, whereas, the supercapacitor is used as the auxiliary source which supports the battery to prolong the lifetime and respond to the power requirement of acceleration. In order to maximize the efficiency of a hybrid energy system, this paper figures out the optimal configuration based on the non-dominated sorting genetic algorithm type 2 (NSGA-II). A set of optimal solutions simultaneously satisfies two objectives: maximize travel distance and battery lifetime. These objectives are formulated by five criteria, including the state of charge of the battery, the root-mean-square value and the standard deviation of the battery current, the final supercapacitor voltage and the regenerative energy to the battery system. The optimization result is evaluated by various driving cycles, i.e., UDDS, WLTC class 2, and Artemis Urban.