Optimal Multiobjective Charging for Lithium-Ion Battery Packs: A Hierarchical Control Approach

Successful operation of a battery pack necessitates an effective charging management. This study presents a systematic investigation that blends control design with control implementation for battery charging. First, it develops a multimodule charger for a serially connected battery pack, which allows each cell to be charged independently by a modified isolated buck converter. Then, it presents the development of a two-layer hierarchical charging control approach to be run on this charger. The top-layer control schedules the optimal charging currents through a multiobjective optimization that takes into account user demand, cell equalization, temperature, and operating constraints. The bottom-layer control is developed using the passivity theory to ensure that the charger can well track the scheduled charging current, and its stability is proven using the Lyapunov stability theory. Extensive simulation and experiments are provided to thoroughly validate the proposed charger and the hierarchical charging control approach.