A battery/supercapacitor hybrid energy storage system is developed to mitigate the battery degradation for electric vehicles. By coordinating the battery and supercapacitor, the proposed system avoids using the large bidirectional DC/DC. Through the improved topology and two added controlled switches, the battery current can be managed flexibly. Based on the battery and supercapacitor voltage, seven operation modes of battery and capacitor cooperation are designed. The control strategy is redesigned to match the modes, in which the key control parameters are calibrated based on three standard driving cycles. During driving, the proposed system calls the predefined parameter set by the cycle recognition technique. The objective of the cycle-related control is to maximize the harvest of the braking energy and minimize battery degradation in various driving styles. Taking the battery case solely as a benchmark and the infinite supercapacitors case as the largest battery degradation mitigation scenario, the battery degradation quantification of the proposed energy storage system shows more than 80% mitigation of the maximum theoretical battery degradation mitigation on urban dynamometer driving schedule (UDDS), highway fuel economy cycle (HWFET), and high-speed (US06) driving cycle, respectively. During the tested driving cycles, the simulation result indicates the battery degradation reduced by 30% more than the battery solely scenario, which proves the benefit of the proposed system.
Optimal sizing and sensitivity analysis of a battery-supercapacitor energy storage system for electric vehicles
