Research On Refrigeration Control Strategy Of Thermal Management System For A Certain Pure Electric Passenger Vehicle

With the development of pure electric vehicle technology,the vehicle thermal management system is inseparable from the performance of the core components of the vehicle,and has gradually become the key core that restricts the performance of the vehicle.On the one hand,the vehicle thermal management system meets the comfort requirements of the passenger compartment for cooling and heating,and on the other hand,it makes the power battery and the drive motor work in a suitable temperature range to ensure safety and service life.However,the high energy consumption of the whole vehicle thermal management system under high temperature conditions greatly restricts the battery life of pure electric vehicles.Therefore,how to reduce the energy consumption of the vehicle thermal management system and increase the hightemperature driving range of the vehicle while ensuring a good temperature control effect has become a current research hotspot.Based on the optimization project of a certain pure electric passenger car thermal management system of the research group,this paper aims to improve the performance of the whole vehicle thermal management system under high temperature,reduce system energy consumption,and increase the driving range of the car,and carry out the research of refrigeration control strategy.First,analyze the thermal mechanism of the vehicle-mounted lithium-ion battery,study its heat generation mechanism and heat transfer mechanism,and obtain the battery DC internal resistance and open circuit voltage temperature changes at different temperatures and SOCs through the hybrid pulse power characteristic step method(HPPC)Curves provide experimental basis for subsequent battery model construction;design battery thermal property parameter experiments,and obtain battery specific heat capacity,thermal conductivity and other parameters by experimental measurement,and provide parameter basis for subsequent battery model construction.Secondly,determine the structure of the cooling circuit of the vehicle thermal management system,divide it into motor cooling circuit,air conditioning circuit and battery cooling circuit,and divide the cooling work mode of the vehicle thermal management system on this basis;calculate the battery pack and passenger compartment Determine the air-conditioning refrigeration load under the heat load under extreme summer conditions,and on this basis,match the key parameters of the compressor,heat exchanger,expansion valve,fan and other components of the airconditioning circuit to provide parameters for subsequent air-conditioning circuit model construction in accordance with.Then,build a one-dimensional simulation model based on GT-SUITE simulation software,including 7 sub-models of vehicle power system,motor cooling circuit,battery cooling circuit,air conditioning circuit,passenger compartment cooling,and front-end heat dissipation,according to the heat transfer relationship between the models Coupling 7 sub-models to complete the construction of the vehicle thermal management system simulation model;based on Simulink to build the vehicle thermal management system refrigeration control strategy model,including the control strategies of the system’s various working modes and components,and conduct joint simulation with GT-SUITE;conduct EV-TEST high temperature driving test,comparing test and simulation results,verifying the accuracy and reliability of the simulation model from the aspects of passenger compartment temperature,battery average temperature,motor outlet water temperature,and vehicle energy flow characterization.Finally,in order to improve the refrigeration performance of the vehicle thermal management system,this paper proposes two different air-conditioning compressor control schemes using fuzzy control and model predictive control.Based on the simulation model of the vehicle thermal management system,a joint simulation under high temperature conditions is carried out.Analyze the impact of the two schemes on the cooling performance of the vehicle thermal management system compared with the traditional PID control.The simulation results show that compared with PID control,fuzzy control and model predictive control can shorten the time for the temperature of the passenger compartment and the temperature of the battery inlet to reach the target temperature,and the temperature fluctuation range is smaller,the overshoot is small,and the control effect is better..In addition,the vehicle thermal management system using the model predictive control scheme has lower energy consumption,and its compressor power consumption is reduced by 10.7% compared with PID control,which increases the driving range of the vehicle by 1.3%.