Research And Design On Battery Management System For Electrical Vehicle

The energy crisis and environmental pollution has promoted the rapid development of new energy electric vehicle industry. As the bottleneck of electric vehicle technology, power battery technology directly restricts the scale of the development of electric vehicle. So far the progress of battery technology itself is still unable to meet the stringent requirements of the electric vehicle. In order to ensure the operation safety of the electric vehicles, increase the energy utilization efficiency and extend the power battery life, in this paper we selected the LFP battery widely and maturely applied in application of electric vehicle energy storage system. Combine with the factual request in application, high-speed real-time data acquisition, battery protection and fault alarm circuit, state of charge estimation, charge and discharge management, equalization management, data storage and distribution management were designed and implemented in this paper. This paper mainly includes the following research:In this article I firstly detailed introduced the development status and problems of electric vehicles, power battery and battery management system. And then I studied and summed up the properties and applications of power battery from the three areas: material selection, specification selection and group technology.Technical ways and process of the design of BMS were studied and set up, the BMS functional modules were divided, and the realizing methods of key technique were discussed. On the basis of analysis and comparison of the distributed method and centralized method, combined with the engineering practice, a distributed BMS based on double CAN communication network was presented, which adopted a two stage structure including Central Master Control Unit (CMCU) and Local Slave Control Unit (LSCU). The LSCU mainly fulfills the function of battery data acquisition, equalization management, battery protection and communication etc. The CMCU mainly fulfills the function of data processing, data storage, data display, transfers, and charge and discharge management etc.Hardware platform is the most important part of the BMS design and is the base and guarantee of the function of the system. Based on distributed structure, two-level of BMS architecture was introduced in detail. In the thesis, the hardware overall system based on "DSP+CPLD" was introduced and the principle of each peripheral module was also showed, including the controller unit circuit, RTC circuit, cell voltage and temperature acquisition circuit, two-direction active equalization circuit, protection and fault alarm circuit, charge and discharge control circuit, total voltage and current measuring unit circuit, data storage and display, CAN communication and remote GPRS communication unit. The paper analyzed interference of BMS, and accomplished anti-jamming hardware design based on design of power supply, electromagnetism shield, transmit lines and grounding system.Software development depends on the BMS hardware platform and they cannot be separated from each other. While developing Software system, it needs to take into account the enforceability of the various parts of the hardware. This paper described the overall design of BMS software system, each functional module division and its programming realization, and gave the CAN communication protocol and software control flow chart. To improve the reliability and stability of the system software, the jamming design was given.This paper designed two-level of BMS architecture and CMCU and LSCU data transmission was via CAN bus. It realized centralized management of distributed control of BMS, facilitated the rational distribution of the battery on the electric vehicle, and reduced sampling harness and improved system reliability and stability.