Simulation And Control Strategy Development Of Heat Pump Air Conditioning System For Electric Vehicles

In recent years,electric vehicles stand on the stage of history with their advantages of high efficiency and pollution-free driving process.But the market share of electric vehicles is small because of problems with their battery capacity and range.In addition to the direct research on battery,many scholars also start from the electric vehicle auxiliary system,and the air conditioning system,which has the highest energy consumption,has become the research focus.Nowadays,most of the electric vehicles on the market are equipped with steam compression refrigeration and PTC electric heating system.Due to the limitation of PTC energy conversion efficiency,the opening of heating system in winter seriously affects the vehicle mileage.As the air conditioning system with the highest energy efficiency ratio known at present,heat pump air conditioning can reduce the adverse impact on the mileage when it is popularized in the automobile.In this paper,an electric vehicle is taken as the research object.After the simulation analysis of the original air conditioning system,the system is improved,and the low-pressure air replenishment heat pump air conditioning system is proposed.The simulation model is built in KULI to study its heating performance in winter.Finally,the corresponding compressor control strategy is established according to the heating condition.There are two main methods for the research of air conditioning system:experiment and computer simulation.This paper mainly studies by simulation method.One dimensional thermal management software is selected as the simulation platform.Firstly,the modeling principle of monomer model is discussed,and then the original refrigeration condition model of the air conditioning system is established and calibrated.In order to have a better understanding of the refrigeration performance of the air conditioning system,this paper selects three parameters,namely the ambient temperature,the condenser air volume and the evaporator air volume,and analyzes the performance changes of the air conditioning system under different parameters.In order to improve the performance of automobile heating in winter,a low-pressure air supplement heat pump air conditioning system is proposed,and its principle and configuration are analyzed.Based on the above original air conditioning model,a new heating condition model of air conditioning system is built.Considering the fact that the calibration data used in the establishment of the indoor and outdoor heat exchanger unit model is the refrigeration condition,that is,the outdoor heat exchanger is used as the condenser,and the indoor heat exchanger is used as the evaporator,which cannot reflect the heat transfer performance of the indoor and outdoor heat exchanger function when heating,this paper chooses the theoretical calculation method to recalibrate the two heat exchangers.Further,in order to study the heating performance of low-pressure supplement heat pump air conditioning,based on the steady-state model,the effects of ambient temperature,outdoor heat exchanger air volume,cabin temperature and relative air supplement on the system performance were simulated and analyzed under different compressor speeds.The above results also provide a reference for the formulation of compressor control strategy.In addition,considering that the heat pump system is prone to frosting in winter,taking the experimental data in a paper as a reference,the heat transfer factor and pressure drop of the heat exchanger are used in KULI for equivalent substitution,and the relevant parameters of the heat pump system performance during frosting are analyzed.Finally,the improved reverse cycle defrosting method is selected after comparing the defrosting methods.The control strategy of air conditioning system is mainly based on the demand of passenger compartment.Firstly,the thermal load of automobile in winter is analyzed.Then,several operating points are selected in the range of use,and the compressor speed is adjusted according to the calculated thermal load.A total of 1855 groups of sample data are obtained.Traditional air conditioning system control is based on threshold control and fuzzy control.In this paper,SVR is used to establish the regression model,which is an intelligent algorithm.The effectiveness of the model is verified by the prediction of compressor speed in China and American condition,and the energy saving effect is outstanding compared with PTC electric heating system.