Design And Implementation Of Intelligent Battery Management System For Electric Vehicles

In recent years,the world's automobile industry has witnessed ushered an explosive growth,which aggravates the problem of energy shortage and environmental pollution in all around the world.The emergence of new energy vehicles which include BEV?Battery Electric Vehicle?,HEV?Hybrid Electric Vehicle?,FEV?Fuel cell Electric Vehicle?can solve the two problems mentioned above at the same time.Although electric vehicles have received great attention and research from automobile manufacturers and scientific research institutions,there are still many key problems that need to be solved,among which the most important one is BMS?Battery Management System?.SOC?State of Charge?is an index to measure the residual energy of battery,which is equivalent to the fuel meter in fuel vehicle.It provides the basis for other operation and management of electric vehicle.However,the state of charge is not a parameter that can be measured directly,other performance parameters of the battery,such as operating voltage,working current and the working temperature of the battery,used to be estimated.Accurate estimation of SOC is an important function of the battery management system,it can not only improve the overall effective capacity of the battery pack,but also play a role in prolonging the service life of the battery pack.In order to meet the needs of range and power output,the working battery package of electric vehicles needs enough energy and power.Due to the inconsistency of single battery,with the increase of service time,the difference between batteries will be greater and greater,which will greatly affect the service life and efficiency of batteries.The basic functions of BMS are:collecting the battery performance parameters?voltage,current,temperature,etc.?,realizing the balance between the single cells and estimating SOC.The advantages and disadvantages of the battery equivalent model proposed in papers are analyzed and combined,considering the characteristics of and a new battery equivalent model is proposed considering the characteristics of LiFePO₄ battery.On the basis of Kalman filter algorithm,considering the open circuit voltage methods,EKF-OCV?Extended Kalman Filter-Open Circuit Voltage?joint algorithm is proposed which can update the initial value of SOC.From the above requirements of the basic functions of the battery management system as the starting point,this paper designs the battery management system hardware system and the supporting software system,and we choose STM32F107VCT6 as the processor,a new electric vehicle chip LTC6803,a high precision current Hall sensor,and other hardware circuits?power supply circuit,isolation circuit,etc.?to complete battery management system.In order to collect the performance parameters of battery and realize the balance function between the single batteries.By using the Visual Studio as development environment and C++language as development language,to complete the sub-program flow chart of each function module in the hardware system.With the help of the platform of battery comprehensive test system,the feasibility and accuracy of battery information collection in battery management system are verified.By using the charge-discharge condition with the vehicle road test,the accuracy and convergence of the EKF-OCV estimation algorithm are verified.