Research On SOC Estimation Method Of LiFePO₄ Battery For Electric Vehicle And BMS Design

As the energy crisis and environmental pollution problems become more and more serious,new energy has gradually become the focus of research and application in various countries.The development of battery technology for electric vehicles has attracted worldwide attention.Among them,the characteristics of Li FePO₄batteries and SOC estimation have become the key technologies of EV battery research,which deserve further study and discussion.In this paper,a set of algorithms and systems are developed to protect and manage LiFePO₄ batteries in order to ensure battery safety,prolong battery life,improve battery performance,and promote the rapid development of electric vehicles.The chemical characteristics of the first study of LiFePO₄ battery voltage,temperature,comprehensive internal resistance of the battery and battery capacity,performance parameters,further inside the electricity core study on electro-chemical polarization and concentration of poor electro-chemical properties,establish the electro-chemical model and the equivalent circuit model,two order RC equivalent model for LiFePO₄ cell model is the most suitable,with high speed the computer processing power and precision,according to the LiFePO₄cell electro-chemical reaction rules,identification of the estimated parameters of LiFePO₄ RC battery two order equivalent circuit model using least square method,dynamic parameter model,and the simulation test to verify the rationality of the parameters.And then put forward the unscented filtering based on Kalman?UKF?Li FePO₄ battery SOC estimation algorithm theory,the design of battery management system?BMS?and the system architecture,the battery management system module design,hardware design,software design,functional safety and testing etc.in detail.After the completion of the above tasks,summarizes the work process and results,in view of the problems and the completion of the situation,the future research work is prospected.In this paper,through the model simulation analysis by least square method to analyze the battery two order RC model can identify key parameters quickly,at less than 2%accuracy,and can achieve on-line identification,improved real-time identification;precise cell model provides a guarantee for the estimation of battery SOC and safe operation,with unscented Kalman filtering?UKF?algorithm,the SOC estimation accuracy is less than3%;the design of the BMS has been applied to a variety of models,the total number of test kilometers has more than 30 thousand kilometers,and has passed the national standard"QCT897-2011 electric vehicle battery management system technical conditions"and EMC,provides a prerequisite for functional safety the development of Autosar standard and development based on ISO26262.