| At present,due to factors such as low energy density of power batteries,short service life,and low coverage of charging facilities,the large-scale industrialization of pure electric vehicles and their market promotion are still difficult.The extended-range electric vehicle is equipped with dual power sources,and has the technical advantages of hybrid and pure electric vehicles,which can effectively alleviate the anxiety of using pure electric vehicles such as short driving range,difficulty in charging and so on.Therefore,at the present stage,it has attracted wide attention as an ideal vehicle for the transition to pure electric drive.However,since the battery capacity of the extended-range electric vehicle is significantly lower than that of the pure electric vehicle,the charge/discharge rate of the battery pack is larger and the temperature rise is more significant.Therefore,it is necessary to focus on the temperature control of the power battery pack for the extended-range electric vehicle.This paper relies on the school-enterprise cooperation project,based on battery thermal characteristics analysis,in order to meet the battery temperature control requirements under all conditions,to develop powertrain matching and control strategy research,and to further enhance the driving safety and adaptability of operating conditions of extended-range electric vehicles.The main research content of this paper is as follows:1.According to the design criteria of the target vehicle's pure electric driving range,the battery's optional capacity range and battery type were determined.Then,the theoretical analysis of the heat generation and heat transfer mechanism of the battery were conducted.Finally,the effect of temperature on the performance of the battery was analyzed using experimental methods,to demonstrate the necessity of conducting in-depth research based on battery thermal characteristics.The accuracy of the electrochemical-thermal coupling model was verified based on the experimental data of the battery's charge and discharge.2.Based on the calculation results of the battery's heat generation power,the battery arrangement space was used as a constraint,and extract a variety of cooling method of medium temperature and flow characteristics.Using CFD simulation technology,the simulation analysis of the cooling characteristics of battery packs with different capacities and cell spacings were conducted and the relevant laws were summarized.For the target model,the higher the upper limit of the volumetric heat rate of the battery,the smaller the degree of freedom of the heat dissipation mode selection.Finally,an adaptation scheme for the capacity of the power battery pack and its cooling method for the target model was determined.3.Based on the research results of battery pack matching and its cooling characteristics,an air conditioning(AC)system considering the cooling of the battery pack was developed.Based on the calculation of the thermal load of the battery pack and the passenger compartment,the key components of the AC system were matched and selected,and the test characteristics of the compressor was conducted.Then,a twostage cooling strategy for battery packs based on cooling characteristics and a cabin temperature control strategy based on fuzzy logic were developed.Finally,the AC system and its load model were built.The co-simulation method was used to verify the cooling effect of the passenger compartment and the battery pack.4.Explain the characteristics of commonly used control strategies for extendedrange electric vehicles,comprehensively considering driving economy and safety,a composite control strategy for the powertrain based on the temperature state of the battery was proposed.Based on the MATLAB/Simulink platform,an Extended-Range electric vehicle simulation model including an integrated AC system was built to verify the rationality of the powertrain control strategy.A unified quantified vehicle operating cost model was established to analyze the impact of ambient temperature and the new AC system on the economy of the vehicle's CD/CS model.Finally,combined with the operating characteristics of the target vehicle model,particle swarm optimization algorithm was used to optimize the APU control strategy.After optimization,the total vehicle operating cost can be reduced by about 3%.The research content of this paper can provide guidance for research on the power battery pack cooling and AC system design of the extended-range electric vehicle.The research results of this paper have reference value for the improvement and optimization of the powertrain control strategy of the extended-range electric vehicle and the promotion of the performance of the vehicle. |
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