Realization Of BMS Integrated Active And Passive Equalization Control For Power Batteries

The unequalizated problem of power battery packs severely affects the safety and efficiency of battery operation.Traditional equalization techniques suffer from slow equalization speed and low equalization efficiency.To address this issue,the article relies on the key industry innovation chain project of Shaanxi Provincial Key R&D Program(2019ZDLGY15-04-02),an active-passive equalization fusion topology based on a bidirectional bridge converter is proposed,and designed and implemented a corresponding Battery Management System.The specific contents of the paper are as follows:(1)Existing lithium battery models and state of charge estimation methods were studied and analyzed.Based on summarizing and comparing their advantages and disadvantages,the second-order RC equivalent circuit model was selected for modelling,and the recursive least squares with forgetting factor method was used for online parameter identification of the model parameters.The Adaptive Unscented Kalman Filter was chosen as the SOC estimation method for the BMS.(2)The traditional Buck-Boost equalization circuit can only equalize adjacent single cells,and the equalization speed is slow and inefficient.To solve this problem,an equalization circuit topology based on a bidirectional bridge converter was proposed to realize energy transfer between any individual cells in the battery pack,improving the equalization speed and efficiency.To reduce switch devices losses during the equalization process,a passive equalization auxiliary circuit with increased switch resistance is added.A fuzzy PID algorithm was used to design the equalization control strategy to achieve precise control of the dynamic changes in the equalization current.(3)The software and hardware of the battery management system were designed and implemented,and a battery management system test platform was built and its performance was tested.The experimental results show that the battery current,temperature,total voltage,single cell voltage collection accuracy,and SOC estimation accuracy of BMS all meet the design requirements.The equalization function of the system was verified through static equalization and charge-discharge equalization experiments.After the equalization control by the BMS,the battery inconsistency was significantly improved.