Differentiation Power Control of Modules in Second-Life Battery Energy Storage System Based on Cascaded H-Bridge Converter

There is a possibility that second-life power batteries, which can store and deliver substantial energy, could satisfy the requirements of stationary energy storage applications. In this article, split second-life battery modules with good performance have been directly introduced to the dc sides of the H-bridges in cascaded H-bridge converter (CHBC) without complex manual dismantling, screening, and recombination of the battery cells. However, the severe discrepancies of the second-life battery modules' parameters can lead to overcharge, overdischarge, and underutilization of some battery modules' effective capacity simultaneously. To suitably integrate and control these widely different battery modules, a differentiation power control strategy based on the online battery parameter estimation method is proposed. Real-time online power allocation of the independent power modules according to the parameters of the battery modules is conducted by the strategy, which ensures that the charging/discharging trajectories of the second-life battery modules during a charging/discharging cycle will all arrive at their maximum/minimum values at the same time, whether the battery modules are in the same phase or different phases. The control range and capability of the strategy are also analyzed quantitatively. Finally, modeling, analysis, and experimental validation are performed on a downscaled prototype in the laboratory.