| Due to its advantages of zero-emission and smooth operation,electric vehicles’development have attracted domestic and foreign researchers,while the vehicle thermal management system can reasonably regulate various components’thermal distribution and ensure all of them operation under a reasonable temperature range to meet the safety,comfort,energy saving,economy and durability of the vehicle.Therefore,the design of a reasonable and effective vehicle thermal management system is the top priority for electric vehicles to achieve the above goals.In this paper,the heat dissipation performance of the electric drive system and waste heat recovery system are studied deeply.The main contents of this paper are as follows:To begin with,this paper introduces the basic structure and function of the vehicle thermal management system.And then analyzes the heat generation mechanism(battery pack,motor,motor controller),operation principle and basic mathematical model of the important components of the electric drive and battery pack thermal management system,which provides a foundation for further research.Aiming at the thermal management of electric drive and control system,this paper presents a new physical framework and control strategy of thermal management.To study its thermal management performance,based on the bench test results and KULI mathematic models,the conventional model of cooling system of electric drive control system,mainly including triad components(on-board charger,high-voltage junction box and DC/DC converter),motor controller,motor,radiator,water pump and fan,etc.,are established.Based on mode switch strategies,control strategies of pump and fan are set up in Simulink.Also,the proposed innovative framework of electric drive system is built in KULI,which adds a proportional valve,two three-way valve and two pipelines,and the control strategies of proportional valve are established in Simulink based on component cooling demand to achieve real-time adjustment of coolant flow.Finally,the thermal management and energy consumption performance of the innovative framework is studied by steady state and transient simulation.Based on steady state simulation results,compared with conventional framework of electric drive system,the innovative framework could reduce coolant exit temperature of the motor 6.1,6.2 and 5 under high speed condition,high speed climbing condition and low speed climbing condition,respectively.On the other hand,based on the dynamic simulation results,the coolant exit temperature of the motor is dropped by an average of 1.1 ~oC under the WLTC condition,and dropped by an average of 1.5 ~oC under the condition and US06 conditions HWFET.Therefore,the proposed framework of electric drive system has better thermal management performance.Aiming at the research of waste heat recovery system,two kinds of waste heat recovery systems that can be used by electric vehicle are studied in this paper.Like the study of electric drive system,bench test was carried out to measure the changes of internal resistance and open-circuit voltage of battery pack with temperature and SOC as well as the heat transfer performance of plate heat exchanger.Combined with the test results and mathematical model,a simulation model of waste heat recovery system was built in KULI software.After formulated the corresponding control strategy of recovery of waste heat,waste heat recovery system based on four channel solenoid valve and waste heat recovery system based on the Chiller are compared with the traditional PTC heating mode analysis,respectively.And the environmental condition is set as-10 ~oC,5 ~oC and0 ~oC.The results show that two kinds of waste heat recovery methods can effectively utilize waste heat from electric drive system to heat the battery pack.On the one hand,the heating time is less different from the traditional way,on the other hand,it can reduce the energy consumption of PTC heaters for heating.Finally,a simulation study was carried out on the performance of the two waste heat recovery systems.The results show that the thermal management performance of the two architectures is very little different,the difference of battery SOC value is less than 0.1%,and the time required for battery pack heating to 15 ~oC is less than 15s.Overall,waste heat recovery system based on four-channel solenoid valve is slightly better than the Chiller-based waste heat recovery system. |
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