AUTHOR=Li Xiaohang , Yin Xin , Tian Zhongbei , Jiang Xinyu , Jiang Lin , Smith Jeremy 

TITLE=Multi-layer state of health balancing control for a battery-based energy storage system to extend cycle life based on active equalization circuits

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2022.966422

DOI=10.3389/fenrg.2022.966422

ISSN=2296-598X

ABSTRACT=State-of-health (SoH) imbalance of batteries brings the waste of capacity, the loss of cycle life and the additional maintenance cost to the BESS. The SoH imbalance widely exists among the battery packs in parallel and battery cells in series, while the current SoH balancing methods can only achieve the SoH equalization of the parallel layer or the series layer separately. This paper proposed a modified multi-layer SoH balancing control method for BESS based on the active equalization circuits. It can attain the SoH equalization among battery packs in parallel layer and battery cells in series layer simultaneously. In parallel layer, the SoH is balanced by controlling the output current of battery packs. The power distribution is determined by the initial equivalent SoH of each pack. In series layer, the series-connected battery cells among each pack will be equalized individually by offering disparate balancing currents with the fly-back converter equalization technique. Furthermore, unlike the common passive equalization technique using the shunt resistor to dissipate the redundant energy in cells with higher SoH, the fly-back converter equalization topology transfers the redundant energy from the cells with higher SoH to the cells with lower SoH, which achieves higher capacity and energy utilization efficiency. Simulation result based on a 3-packs-15-cells BESS verified the effectiveness of the proposed method. This method further prolong the cycle life of BESS about 52.9% and 18.3% comparing with the conventional active SoC balancing control and the existing multi-layer SoH equalization scheme, respectively.