Towards a smarter hybrid energy storage system based on battery and ultracapacitor - A critical review on topology and energy management

Hybrid Energy Storage System (HESS) can well solve the problems faced by alternative single energy storage system in terms of meeting the needs of high specific power and high specific energy simultaneously for plug-in hybrid electric vehicles (HEVs). A HESS containing battery and ultracapacitor (UC) has drawn much attention. However, there have been relatively few reviews on its structures and energy management strategies (EMSs). Based on the summary and analysis from the existing publications, this paper reviews and discusses the structures and the EMSs of HESSs comprised of battery and UC. Focusing on energy management research, a detailed discussion of rules-based control algorithms, optimization-based control algorithms and intelligent-based control algorithms is presented. Several typical implementations and applications are presented in detail, and a comparative evaluation of these methods can help researchers select the appropriate method to develop EMSs for HESSs. Finally, the paper also highlights a number of key factors and challenges, and presents the possible recommendations for the development of big data and machine learning-based algorithm for the energy management of the HESSs.