A Model-Based Research on Performance Evaluation and Topology Optimization of Series-Parallel Lithium-Ion Battery Packs

In order to meet the voltage and capacity demands of actual battery system, the battery pack usually needs to use a large number of lithium-ion (Li-ion) cells in groups, and different grouping topologies will bring differences in the performance of the pack. In order to better evaluate and compare the differences, this paper proposed a simplified modeling method for battery packs by considering the variations of battery parameters. And for the complex series-parallel grouping topologies, this paper developed an iterative algorithm which is suitable for computer simulation. Compared with the combined model, the proposed modeling method can improve the calculation speed while ensuring the accuracy, and the proposed method can be easily applied to large-scale battery systems. Based on the algorithm, this paper conducted the Monte Carlo simulations to quantitatively evaluate and compare the differences of current distribution and capacity utilization between different grouping topologies, and to compare the change process of the state of charge (SOC) through cyclic charge and discharge simulations. Finally, this paper proposed an idea of topology optimization for different possible grouping topologies of large-scale battery systems. In a word, this study provided users a method about performance evaluation and topology optimization when designing battery systems.