Study On Cooling System Performance Analysis And Optimal Control Of New Energy Vehicle

Compared with traditional fuel vehicles,electric vehicles,which possess many unique advantages,such as no pollution emissions,simple structure,easy to maintain,and almost no noise during driving,may be the future development of the automotive industry.Power lithium-ion battery packs,as the main energy storage devices of current electric vehicles,have the advantages of higher energy density,low self-discharge rate,high charge-discharge rate,long cycle life,etc.,However,a large amount of heat is generated during use of the battery pack,and lithium-ion batteries have rapidly degraded performance under high temperature conditions,which will affect the cycle life and performance of the batteries.Continuous heat accumulation may also cause dangers such as explosions and fires,seriously affecting the safety of electric vehicles.Thereby,thermal management of the battery pack is of great importance.As the main power output device of electric vehicles,the drive motor has high power,high torque and other characteristics,which will reversely bring a lot of heat to driving motor during its use.Meanwhile,the motor cooling system consumes a lot of power,which seriously affect the cruising range of electric vehicles.Therefore,it is very critical to formulate a detailed control strategy for the working process of motor cooling system work process.In this paper,the research methods combined experiments and CFD simulation analysis,has been carries out to further study of the power lithium battery pack cooling system of new energy vehicles in length.And the automatic control module for the motor ATS cooling system was designed based on the analysis and the experiments.The main conclusions can be obtained as follows:(1)The working principle and heat generation mechanism of the lithium iron phosphate battery are analyzed,and the simulation model of the thermal effect of the power lithium battery is established.The simulation analysis of the heat generation characteristics and the battery temperature field are performed on the single cell at different discharge rate conditions.In addition,the temperature distribution of battery is also imaged.(2)The test bench for internal resistance characteristics and temperature rise characteristics of the power lithium battery is built.The internal resistance of the battery at different SOC conditions is tested and its variation law was analyzed.The temperature rise of the battery at conditions of 1C,2C and 3C discharge rate is tested,and the reason for the temperature change of the single cell is analyzed.(3)Established a simulation model for battery cooling structure,and the battery cooling performance test bench is built to test the cooling performance of the preliminary designed cooling structure and verify the simulation model.On this basis,the optimization design of the heat dissipation structure of the battery pack and the simulation analysis of the cooling structure at different cooling conditions are performed.(4)Radiating performance of the radiator in the motor cooling system is tested through an experimental bench.Meanwhile,a detailed automatic control strategy is formulated based on the test data.The hardware design and software development of the motor ATS cooling system automatic control module is completed using Freescale's MC9S08DZ60 main control chip.