Research On Thermal Management Technology For Battery Of Pure Electric Vehicle

With the increasingly serious environmental and energy problems,automobile manufacturers all over the world focus on new energy vehicles.In recent years,pure electric vehicles have developed rapidly in China.Battery pack is the only power source in pure electric vehicle,its performance,endurance mileage and safety are related to the temperature of battery pack.Therefore,it is of great significance to study the battery thermal management technology of pure electric vehicle.Firstly,aiming at the problems of high energy consumption and slow cooling/heating speed of traditional battery thermal management system,a comprehensive thermal energy utilization thermal management system is proposed.The system adopts heat pump technology,liquid-based convection heat transfer method and motor cooling heat recovery technology.Secondly,the simulation model of the comprehensive thermal energy utilization thermal management system is established,and the refrigeration/heating performance of the comprehensive thermal energy utilization thermal management system is simulated.Then,the influence of relevant parameters on the comprehensive thermal energy utilization thermal management system is studied,and the parameters that have a greater influence on the system performance are revealed.Finally,according to the results of parameter research,the control method is designed to further improve the performance of the system.The main work and conclusions of this thesis are as follows:1.Design and simulation of the comprehensive thermal energy utilization thermal management systemAiming at the problems of high energy consumption and slow cooling/heating speed of traditional battery thermal management system,a comprehensive thermal energy utilization thermal management system is designed.The system adopts heat pump technology,liquid-based convection heat transfer method and motor cooling heat recovery technology.Then,the simulation models of the comprehensive thermal energy utilization thermal management system and the traditional battery thermal management system are established,and the cooling/heating performance of the two systems is studied.The results show that compared with the traditional battery thermal management system,the comprehensive thermal energy utilization thermal management system has a faster cooling/heating rate.In refrigeration mode,at least 43.6% energy can be saved.In the heating mode,the motor cooling heat can increase the average COP of the system by over 32%.2.Study on parameters of the comprehensive thermal energy utilization thermal management systemIn order to design the control method of the comprehensive thermal energy utilization thermal management system,the influence of related parameters on the cooling/heating performance of the system is studied.The results show that the compressor speed/displacement has a great influence on the cooling/heating performance,the average COP of the system and the compressor power.The inlet air volume of condenser/evaporator has a certain influence on the cooling/heating performance of the system,and has a great influence on the outlet air temperature of condenser/evaporator.The speed of vehicle has a great influence on the generated heat of battery pack and motor.As the speed of vehicle increases,the generated heat of the battery pack and motor increases continuously,and the increase is more and more large.3.Research on control method of the comprehensive thermal energy utilization thermal management systemAiming at the problems of high energy consumption of system and battery pack temperature fluctuation under threshold control,the PID controller and fuzzy PID controller are designed.PID control and fuzzy PID control take the temperature difference between the battery pack temperature and the set temperature as the feedback quantity,and the compressor speed as the output quantity.The results show that compared with the threshold control,the PID control can adjust the compressor speed in real time and reduce the energy consumption of the system.However,in the early stage of simulation,the cooling speed of the system is slow and the battery temperature overshoot is large.Compared with PID control,fuzzy PID control introduces fuzzy control,which can adjust the three parameters of P,I and D in real time.The problems such as slow cooling speed of the system,large overshoot of battery temperature and slow response speed of the system are solved.