Research On Software And Hardware Design Of SOC Estimation And State Monitoring Based On Small Power Battery Pac

Cars are an indispensable transportation for our daily life traveling.While it is convenient for us to travel,they also emit a lot of harmful gases,which affect the ecological environment and lead to global warming.Compared with fuel vehicles,electric vehicles can effectively save energy and reduce harmful emissions.The electric vehicle industry has become a key development direction supported by the government.As the power source of electric vehicles,the performance of power batteries directly reflects the cruising range of electric vehicles.In practical applications,single cells are often connected in series and parallel to form a battery pack to increase the power and capacity of the battery.However,due to the differences between the monomers,it is necessary to perform balanced management and accurately estimate the battery SOC,that is to predict the remaining battery power and the vehicle mileage.However,the current batteries have large differences and low SOC estimation accuracy,which reduces the overall service life of automobile battery packs.Based on above problems,this paper designs a centralized lithium iron phosphate battery management system with MC9S12G128 chip as the core,which has realized the balanced management of single cells,and has proposed a SOC estimation method based on OEKF.The design has effectively improved the accuracy of SOC estimation.The invention is a great contribution to the electric vehicle industry.The management of single cells has provided support to the development of electric vehicles.The detailed research content and results of this article are as follows:(1)Carried out research on power battery condition monitoring and management methods and algorithms.According to the design requirements of the battery management system,a voltage,temperature and other information collection plan and a balanced management plan are proposed to meet the requirements of high sampling rate and high reliability for single battery voltage collection;According to the working principle,charging and discharging process,cycle life characteristics and influencing factors analysis of lithium iron phosphate battery,on the basis of traditional extended Kalman filter,the dynamic correction item of observation noise is introduced,and the optimized extended Kalman filter is obtained.Apply it to the battery SOC estimation,establish the OEKF algorithm based on the battery RC model,and verify its effectiveness through simulation.Simulation analysis shows that the average error after optimization is increased from 2%before optimization to 1.87%,and the maximum error after optimization is changed from before optimization.From 3%to 2%.(2)A centralized battery management system hardware circuit has developed.In response to high sampling rate,high reliability,high common-mode voltage,high-precision design requirements and based on NXP’s MC9S12G128 high-performance microcontroller,it has combined with battery management system functional characteristics,the main control chip peripheral circuit,voltage acquisition circuit,and equalization.And then Circuits are designed,temperature acquisition circuits,power supply circuits,and communication circuits,and used Altium Designer to build,rigidly weld and debug the circuits,and realize the single voltage collection of 12-24 cells;the isolated battery monitoring module is used to collect the voltage of the battery by passive balance controlling,through the single processor equipped with multiple battery monitoring chips,the management of multiple battery packs in series,as well as the passive balance and real-time feedback balance of the battery pack.It has improved the accuracy and timeliness of battery monitoring.The digital converter expands the temperature acquisition channel,makes up for the lack of the battery monitoring chip temperature acquisition channel,and finally realizes the full coverage of the temperature acquisition of the single battery.(3)A centralized battery management system software program has designed.According to the hardware function requirements of battery voltage acquisition,current acquisition,battery temperature acquisition,battery balance,state of charge estimation,system power-off,etc.,a layered design and a functional modular design concept are used.Based on the Code Warrior environment,the management system has compiled and debugged the module code,and it satisfies the hardware functional requirements and ensures the concise structure of the battery management system software system and the clear distinguished the division of functions.(4)Battery management experiments were carried out and also data collection and analysis.In accordance with the battery charging experiment,the battery voltage and temperature are measured,and the data acquisition accuracy and balance effect of the battery management system are tested.The experiment shows that the voltage acquisition accuracy reaches 5mV,the battery pack balance effect is remarkable,the system is stable and reliable,and matches the design requirements.