Lithium-ion battery pack equalization: A multi-objective control strategy using interleaved cascaded bidirectional flyback converters

To address the challenges of the current lithium-ion battery pack active balancing systems, such as limited scalability, high cost, and ineffective balancing under complex unbalanced conditions, this study proposes a novel balancing structure based on a flyback transformer and switch matrix. This design effectively reduces the component count and enables balancing for long series-connected battery packs. Furthermore, building upon the improvement of the balancing strategy, a multi-objective sliding mode balancing controller is devised, considering balance speed, battery consistency, and energy losses during the balancing process. In response to the unbalanced state of the battery pack, the controller dynamically adjusts balancing currents to optimize system performance comprehensively. The sliding mode controller's adaptability enables the assignment of varied weight coefficients to different objective functions, thereby enhancing the efficiency of battery pack balancing. Ultimately, simulation and bench experiments substantiate the efficacy of the proposed scheme in this study. The outcomes of actual equalization experiment demonstrate a notable enhancement, including a 1.97% increase in the maximum capacity of the battery pack, a 21% improvement in equilibrium consistency, a 15.76% reduction in energy loss during equilibrium, and a 29.82% decrease in equilibrium time.