Research On Distributed Battery Management System Of Pure Electric Vehicle

Compared with traditional fuel vehicles,electric vehicles are one of the effective ways to cope with energy issues and promote the sustainable development of the automotive industry.As the power source for electric vehicles,batteries play a significant role in the cruising range of the vehicle and the personal safety of passengers.The battery management system(BMS)of electric vehicles is an important link connecting power batteries and electric vehicles.So far,lots of automotive companies at home and abroad have been committed to the development and manufacture of electric vehicles.However,with the increase in the number of electronic control units and the complication of functions,the safety and reliability of electronic control units need to be further studied.In this work,we introduced the development status of electric vehicles and battery management systems,following by an overview of the concept of functional safety of road vehicles.According to the functions of the battery management system,the functional failure was analyzed and the damage caused by the functional failure was identified.The hazard analysis and risk assessment was conducted as well as the security architecture analysis were performed,and the distributed BMS system architecture was summarized.In addition,high-voltage diagnostic functions such as contactor state detection,insulation detection,and high-voltage interlock detection have also been explored to increase the reliability of the system.The battery management system,which consists of a battery management unit(BMU)and several cell management units(CMU),adopts a master-slave topology.In the hardware design,CMU adopts the analog front-end chip MC33771 to collect battery voltage and temperature data,exchange data on the bus in the form of CAN network nodes.The configuration of equalization resistors outside the analog front-end chip and the processing scheme of error signals were unveiled.The BMU employs a dual-core lock-step MCU to complete the task scheduling.Relevant hardware peripheral circuits were designed,including: analog signal acquisition and process circuit,connection circuit between power management chip and BMU.Finally,the high-voltage detection,current detection,and CAN physical layers were tested and the experimental results are in agree with the hardware requirements.The software development process for the battery management system was introduced,and the software architecture of AUTOSAR was briefly described.The strategy of the controller operation,current sampling strategy,battery equalization strategy and joint status estimation strategy were demonstrated.The second-order lithium ion model was established on the Simulink platform through the hybrid pulse capability test.And then extended Kalman filter algorithm model was built.The accuracy of the EFK algorithm was verified by comparison with the coulomb counting algorithm under the same conditions.