A Comparison Study of Hybrid Energy Storage System Topologies for Electric Vehicles

This study presents a comprehensive comparison of battery-only, passive, and semi-active hybrid energy storage system (HESS) topologies for electric vehicle (EV) applications. Despite numerous studies on HESS topologies for EVs, there remains a lack of consensus regarding the optimal topology, with limited attempts to address this gap through comprehensive comparisons. Previous research has focused on comparing different semi-active topologies through simulations, neglecting passive approaches and employing best-case scenarios for the energy management system (EMS), disregarding widely used rule-based power follower strategies. The present study aims to address the research gap by conducting a comprehensive comparison of battery-only, passive, and semi-active topologies for a realistic EV application case, focusing on their ability to enhance DC bus voltage stability, RMS battery current, and maximum battery current. The performance of these topologies is evaluated through simulations and experimental validation, with the system under investigation based on the parameters of an electrically converted vehicle. Results show that while the passive HESS topology delivers excellent RMS battery current performance, comparable to the semi-active SC/battery system, it falls short in reducing the maximum battery peak current where the semi-active topologies excel. Additionally, both passive and semi-active SC/battery topologies significantly improve the standard deviation and variation of the DC bus voltage. This study highlights the importance of topology selection in reducing battery degradation in EVs, contributing to the understanding of topology-dependent characteristics, power flow control, discharge rates of the battery pack, and DC bus voltage stability in HESS for EVs.