Integrated Temperature Effect And Real-time Energy Management Strategy Of Plug-in Hybrid Electric Vehicle

Plug-in hybrid electric vehicle is a new energy vehicle with the advantages of pure electric vehicles and hybrid electric vehicles. It has a long pure electric driving range, and can use fuel to increase its mileage. So it becomes an important developing direction in the research field of electric vehicles, and the energy management strategy is the core technology of plug-in hybrid electric vehicle.The temperature effect of the three way catalytic converter and engine coolant has important influence on the energy distribution of the vehicle’s power source and the fuel consumption and emission of the vehicle. At present, the energy management strategy does not consider the temperature effect of the three way catalytic converter and engine cooling, and the energy management strategy based on optimization theory is difficult to be used in real-time control. Therefore, it is great significance to study the optimal control strategy which considers the temperature effect of the three way catalytic converter and the engine coolant and can be applied to real-time control.This thesis takes the single motor plug-in hybrid electric vehicle as the object of research. In order to improve the vehicle’s fuel economy and emissions, this paper carrys out the real-time optimization control strategy of plug-in hybrid electric vehicle considering the temperature effect. The main works are summarized as follows.① After the parameters of plug-in hybrid electric vehicle’s power transmission system are optimized, the model of the power transmission system is built. The economic car developed by a domestic manufacturer is taken as a foundation, according to the parameters of the prototype vehicle and the domestic and foreign relevant technical indicators, the constraints about power performance are determined. Based on the power model of the prototype vehicle, the parameters of the power transmission system are optimized by using multi-objective genetic algorithm, which takes the power system’s cost, engine fuel consumption and emission as the optimization objective. On the basis of obtaining the parameters of the power transmission system, the experiments of the power transmission system’s components are carried out. Base on the experimental results and theoretical calculations, the model of the engine, motor, battery, transmission and driver are established.② The energy management stragy considering the conversion of the three way catalytic converter is built. Because the plug-in hybrid vehicle’s catalytic converter is easily to work in abnormal operating temperature range, the catalytic converter’s conversion efficiency is low. In order to solve the problem, the method of temperature compensation by increaseing additional cost function when the catalytic converter work in abnormal operating temperature range is put forward. Then make the engine fuel consumption and that additional cost as the target function. According to the minimum principle of Pontryagin, Hamilton function is built, The energy management stragy considering the conversion of the three way catalytic converter is got after the solve of the target function.③ The energy management strategy considering the cooling/heating power demand of the cab is established. The cabin thermal model is set up on the basis of the vehicle’s heating system, and the demand cooling/heating power of the cabin under the set environment temperature and cabin temperature is calculated, and the engine coolant temperature which is high enough to provide all heater demanded by the cabin is also calculated. Then, the CD-CS mode control strategy with and without the cooling power demand is studied, and the influence of the cooling power on the pure electric driving range of plug-in hybrid vehicle is analyzed. At last, aiming at the energy management strategy considering the heating power demand of the cab, the passive heating mode control strategy and the active heating mode control strategy are studied, and the system’s energy flow under that control strategy is analyzed.④ The plug-in hybrid electric vehicle’s control strategy integrated temperature effect and real-time controlling is established. Because control strategy basing on principle of the minimum is hard to apply in real time controling, the real-time control strategy basing on approximate pontryagin’s minimum principle is proposed, which can shorten the optimization time by simplifying the optimal control variable’s search space; Based on considering the temperature effect of the three way catalytic converter and the engine coolant, a method is put forward, which can add heater supply by engine coolant’s waste heat and reduce heater supply by battery’s electric energy, by adding punish in the cost function when the temperature of engine coolant is below its temperature threshold, at the same time, in order to reduce engine start and stop times to make catalytic converter’s temperature above its light temperature and improve the efficiency of catalytic converter, the engine torque after the optimization control strategy basing on approximate minimum value principle is filtered by start and stop filter. Taking the fuel consumption and emission under the NEDC driving cycle and the commute condition as the cost function, the filtering time of the start and stop filter is optimized by using the genetic algorithm. At last, the plug-in hybrid electric vehicle’s real-time optimal control strategy with temperature effect is simulated under the NEDC driving cycle and the commute condition.⑤ The experimental study on real time optimal control strategy based on approximate minimum principle is carried out. The multiple test platform of the plug-in hybrid electric vehicle‘s power transmission system is built, and the test’s program developed on the D2P’s Motohawk and Matlab/Simulink/stateflow is designed. The measurement and control interface is developed based on ATI-VISION platform. The function and operation mode of plug-in hybrid electric vehicle is realized by the bench test. The vehicle control software of the CD-CS model control strategy and the real-time control strategy based on approximate minimum principle is designed. Finally, the vehicle road test is carried out, and the results of the road test verify the real time optimal control strategy’s real-time performance and fuel economy.