Study On Energy Management Strategy For The Plug-in Hybrid Electric Vehicles With CVT Based On Efficiency Optimized

Since the increasingly serious energy shortage and environmental pollution problems, it is rather urgent and vital to develop new energy vehicles. Plug-in hybrid electric vehicle(PHEV) is one of the new energy vehicles combined with the characteristics of both pure electric cars and hybrid vehicles. With a significant advantage of low fuel consumption and long driving range, PHEV have been attracting considerable attention and becoming a research hotspot. According to vehicle speed and load change, continuously variable transmission(CVT) can change the transmission ratio continuously and effectively control the working point of the power source. It is an ideal transmission for the automobile.Taking the PHEV equipped with CVT as the research object, its power system design and energy management strategy are studied deeply in this paper. The main contents are summarized as follows:(1) Based on the traditional CVT car, the overall structure and layout of the PHEV power system are designed. Then, according to the requirements of vehicle parameters and performance indexes, the parameters of the power system were calculated to determine, including the engine power, the motor power, the power battery capacity and the number of monomer and other key parameters. Besides, the performance data of the key components of the power system is obtained by experiment., and the efficiency numerical model of the key PHEV power system components is established by using experimental modeling and theoretical modeling method reasonably.(2) An energy conversion coefficient calculation method is proposed for PHEV. The efficiency of the system under different operation mode is changed into uniform standard, and the system efficiency calculation method is analyzed according to the energy transfer path of different working modes. In order to achieve the highest comprehensive efficiency of the system, the energy management of the various working modes was optimized based on the efficiency model of the key power system components.(3) Under optimum system efficiency, the system efficiency of each working mode is analyzed, and the mode switching rules are determined. The braking force distribution rule of vehicle in braking condition is analyzed, and the strategy of regenerative braking torque distribution and the control strategy of the brake mode are established.(4) Simulation and analysis of vehicle performance. According to the structure and features of PHEV power system, the vehicle forward simulation model was built based on MATLAB/Simulink platform and the vehicle power performance and economic simulation analysis are carried out to validate the proposed PHEV energy management strategy.