| It is an urgent need to find a kind of new energy vehicles to replace the traditional motor vehicles because of environmental pollution and energy crisis. Electric vehicle has a big advantage in battery energy conversion and exhaust emission, which are becoming the alternatives to traditional motor vehicles. However, the lithium battery management restricts the popularization and promotion electric vehilcle.In this thesis, the lithium ion battery types are compared and analyzed, and finally the lithium iron phosphate battery is selected as lithium-ion batteries management research object of electric vehicle.This paper first introduces the current situation of the development of electric vehicle industry and some problems encountered in the popularization of electric vehicle at home and abroad, and it comes to a conclusion that the lithium battery management technology is the most prominent difficulties in electric car development. Then the analysis of management technical difficulties of the lithium battery are be given.Lithium battery SOC (SOC) estimation precision and inconsistency between lithium battery monomer battery are the most difficult in lithium battery management.Based on a large number of lithium iron phosphate battery charging and discharging test, the battery key performance basic parameters has been got, and basic parameters including charge and discharge characteristics, ratio, temperature and static characteristics.Based on the design and research of electric vehicle with lithium-ion batteries efficient operation management, the SOC estimation based on EKF composite algorithm and GS7708active equalization control strategy has been put forward, which is key research part of this article.In the process of electric vehicles use, if the lithium-ion battery pack can’t be effectively managed, and the lithium battery working state can not be real-time estimated, the overall performance of lithium-ion batteries will be reduced, obviously the driving distance will be cut down and the cost of cars will be soared.Based on ampere-hour metrology, open circuit voltage method and extended kalman filtering algorithm, complex SOC estimation algorithm based on EKF has been proposed, and the compound algorithm Thevenin battery model is set up, using the MATLAB simulation proves the accuracy and feasibility of the composite based on EKF algorithm.For other monomer lithium battery in the circulation work after a period of time, there are inconsistency, which easily to cause the lithium battery overcharge and overdischarge. The inductance active equalization control strategy based on GS7708and global optimization algorithm has been proposed, and the related active balancing control circuit has been designed.In addition to iron phosphate lithium battery pack for the active balancing experiments, comparing the balanced voltage change before and after, whose aim is to verify the feasibility of the active equilibrium strategies. Thus, by raising the lithium battery SOC estimation accuracy and decrease the active equilibrium time, which implements the lithium battery management effectively.On the hardware, the whole hardware circuit is based on STM32F103VBT6chip electric cars using lithium-ion battery pack has been designed, mainly including CPU minimum block system, power supply module, EEPROM, RS485communication interface circuit, man-machine interface and lithium battery charge and discharge voltage current signal sampling, and adopts special battery monitoring chip AD7280A to get the signal data sampling.On the software design the STM32Keil uVision4development environment and function has been made a brief overview, on the basis of hardware circuit, lithium battery charging and discharging management system of software programming has been completed, and the corresponding program and circuit diagram has been designed. Finally, some summary and outlook has been made in this article. |
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