A review of key issues for control and management in battery and ultra-capacitor hybrid energy storage systems

The hybrid energy storage system is a kind of complex system including state coupling, input coupling, environmental sensitivity, life degradation, and other characteristics. How to accurately estimate the internal state of the system, delay the battery life degradation, realize the coordinated and optimized control of power and energy have become the focus and difficulty of the hybrid energy storage system. With the application and popularization of hybrid energy storage systems in electric vehicles and smart grids, relevant theoretical and technological breakthroughs become more and more urgent. Many new achievements, new theories, new methods and new technologies from the fields of materials, information, energy, control and artificial intelligence have been put into this field. This paper comprehensively reviewed the key issues for control and management in hybrid energy storage systems from the aspects of multi-scale state estimation, aging mechanism investigation, life prediction, and energy optimization control of the hybrid energy storage system. Through the in-depth review of key scientific issues, the latest theoretical techniques and application results are presented. Finally some future research challenges and outlooks are presented, in hopes to provide some new ideas and inspirations for the future investigation of the hybrid energy storage systems. (C) 2020 Elsevier B.V. All rights reserved.