Research On Control Strategy Of Electric Vehicle Air Conditioning System In Dual Cooling Mode

At present,the pure electric vehicles have become the main strategic direction of the development of the new energy automobile industry because of the characteristics of no exhaust emission,low noise,high energy conversion rate and low running cost.The energy of pure electric vehicles comes entirely from on-board power batteries,and the limited battery energy greatly restricts the development of vehicles.As the largest auxiliary system of the vehicle,the energy consumption of the air conditioning system accounts for about 33% of the vehicle,which seriously affects the driving range of the vehicle.In addition,a large amount of heat will be released in the continuous working process of the battery.Too high temperature will directly reduce the performance of the battery.Therefore,based on the air conditioning system of electric vehicles and considering the requirements of passenger cabin refrigeration and power battery refrigeration,this paper designs a control strategy of air conditioning system in dualcooling mode,and finally carries out simulation verification.The main work is as follows:The heat load of the passenger compartment is 3526 W and that of the power battery is 2774 W,and the total heat load of the electric vehicle is 6300 W when the two are added together.Using R134 a as the refrigerant of the system,thermodynamic analysis of the air conditioning system is carried out.Combined with the calculated heat load,the relevant parameters of the compressor,internal and external heat exchanger,throttling device and other air conditioning components and power battery are calculated and matched.The overall simulation model of the air conditioning system of electric vehicle is established in the software AMESim.The control strategy of air conditioning system is designed according to the requirements of double cooling.The control of air conditioning system is divided into two parts: passenger cabin temperature control and power battery temperature control.Aiming at the temperature control of the passenger cabin,a fuzzy controller with two input and two output is designed by using the fuzzy control method.By controlling the speed of the compressor and the indoor fan,the cooling capacity of the passenger cabin is controlled.Aiming at the power battery temperature control,PID control method is adopted to control the cooling capacity of the battery by controlling the opening of the electronic expansion valve.The simulation model of the air conditioning system and the temperature control system of the passenger cabin are established respectively in the software AMESim and Simulink.Finally,the co-simulation analysis of the cooling performance of the passenger cabin and the cooling performance of the power battery is carried out.The results show that the control strategy designed in this paper can effectively control the temperature of the passenger cabin and the power battery,and can realize the dual cooling function.At the same time,comparing with switch control,it is found that the control effect of fuzzy control is more accurate,and the refrigeration energy efficiency ratio EER of air conditioning system is higher.In addition,when the air conditioning system is in double cooling mode,the SOC of battery drops more slowly,and the system is more energy saving.