System Theoretic Analysis of Battery Equalization Systems

Abstract

Battery equalizers are widely used in multi-battery systems to maintain balanced charge among individual battery cells. While the research on the hardware realization of battery equalizers has received significant attention, rigorous analysis of battery equalization from the system's point of view remains largely unexplored. In this research, we study three types of battery equalization system structures: series-based, layer-based, and module-based. Specifically, we develop mathematical models that describe the system-level behavior of the battery equalization processes under these equalization structures. Then, based on the mathematical models, analytical methods are derived to evaluate the performance of the equalization processes. We also carry out statistical analysis to compare the performance of the three equalization structures considered. In addition, these systems will be studied with energy loss. Note to Practitioners--This research work develops computationally efficient tools to evaluate the performance of battery equalization systems under series-based, layer-based, and module-based structures, respectively. Using these tools, engineers and designers can predict the equalization time of a battery system in real-time with high accuracy. In addition, based on these tools, one can compare the equalization performance under different structures without using time-consuming simulations. Numerical experiments suggest that the layer-based and module-based structures have better average performance than the traditional series-based equalization structure.