Validation of a balancing model based on master-slave battery management system architecture

The battery management system (BMS) performs the monitoring and control of the charging/discharging process of the cell, state of charge estimation, battery safety and protection, state of health estimation, cell balancing, and thermal management. These control operations ensure accurate, safe, and reliable operating conditions, individual cell damage on battery string, and increase the cell life. Battery balancing is one of the key technologies in the BMS, which affects the actual usable capacity range, performance, and lifetime of the entire battery module. However, it is difficult to evaluate or compare the performance of the overall BMS under the multi-series battery module structure. Most of the proposed battery energy storage system (ESS) models focus on energy distribution and system estimation (microgrid or renewable energy). This study develops a balancing model for estimating the balancing performance of the BMS. A Master-Slave BMS (MS-BMS) is proposed to validate the balancing model. The Master and Slaves of the BMS employed a traditional flyback converter with a MOSFET switching array and bidirectional flyback converters with photoMOS arrays, respectively, to perform the balancing behavior. The balancing skill, balancing circuit power, equalization speed, control simplicity, modularization simplicity, and cost has been considered in designing the proposed BMS. The simulation results are verified with the experimental results, which are then compared with the balancing model's results under the five balancing conditions, and the average absolute error of the balancing duration results is 3.12%. The performance of the proposed BMS is also compared with the existing modular BMS architecture, which validates the advantages of the proposed BMS including equalization speed, control simplicity, modularization simplicity, and cost.