| Electric vehicles are the focus of new energy vehicle developments in the future since EVs can realize zero emission and pollution.However,on the one hand the needs for cooling and heating in the cabin reduce the driving mileage to a large extent in the real work.On the other hand,overheating of battery will lead to thermal failure.Overcooling also harms the charge/discharge efficiency and reduce the available capacity.Good thermal management system can improve the energy efficiency of EVs as well as the thermal safety,reliability and cycle life of the battery.Therefore,the integration of BTMS(Battery Thermal Management System)and HPAC(Heat Pump Airconditioner)systems is discussed,focusing on reducing thermal load,effective heat transfer and reuse of waste heat,to establish the integrated VTMS(Vehicle Thermal Management System)of EVs which can help different subsystems collaborative control and utilize the on-board energy more efficiently.This article focused on the integrated thermal management of EVs combining some project of EV's VTMS development,matched the parameters of critical components of thermal manage according to the parameters of the target vehicle,decided the control strategy of working mode and verified the feasibility using simulation.Detailed works are as follow:(1)Completed schematic design of the integrated VTMS including the elaboration of working principle and components of the heat pump air conditioner,the testing of temperature characteristic of lithium battery in which the temperature characteristic,physical characteristics and heat transfer characteristic were understood,and the optimum working temperature range were decided.Besides,the normal working temperature of motor and electric system was investigated.The integrated VTMS was designed and the detailed structure and working mode were introduced.(2)Completed the matching and modeling works of key components of the VTMS subsystems,based on parameters of target vehicle,including matching parameters of the power battery and verifying the battery heat model according to testing data of the power battery.The balance calculation and thermodynamic calculation of heat load of heat pump air conditioner were completed,as well as the modeling works of compressor,electronic expansion valve,and heat exchanger.The status of each working point in theoretical condition was decided.Besides,the modeling works of power motor,the radiator in the circulation loop,the inverter and control system were also completed.(3)Completed the control strategy design of VTMS.The logic threshold control strategy of the VTMS was designed according to the needs of thermal management working mode.The speed control strategy of compressor and opening control strategy of electronic expansion valve were designed according to the heat pump air conditioner.The BTMS control strategy under specific working conditions was designed.In addition,the control strategies of motor,open and close of cooling fan and speed of water pump were designed.(4)Completed the simulation works in AMESim and MATLAB/Simulink.Based on the mode comparison of PTC,air conditioner and waste heat reuse under different temperature conditions.The impact of temperature condition in the driving cabin on driving mileage was analyzed.The preheat,insulation and heat dissipation performance of the power battery and analysis of the reuse of motor waste heat shows that they can meet the needs of comforts for heating and cooling,as well as increase the driving mileage of EVs. |
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