Research On Energy Management Of Plug-in Hybrid Electric Vehicle Considering Catalyst Temperature

Plug-in hybrid electric vehicle(PHEV)has two power sources: engine and motor.Its large power battery can be charged by external power grid.Therefore,PHEV has both advantages of hybrid electric vehicle and pure electric vehicle.PHEV,as an important research object in the transition period from traditional internal combustion engine vehicle to pure electric vehicle,has good fuel economy and emission,and is one of the effective ways to solve the current energy crisis and environmental pollution.The energy management strategy is one of the core technologies of PHEV.The purpose is to distribute the energy of the two power sources reasonably,which is an important factor affecting the fuel economy and emissions of the whole vehicle.The temperature of three-way catalyst has an important influence on the energy distribution and emission of the vehicle.The current optimization strategy fails to adapt to the change of working conditions well when considering the temperature of catalyst.Therefore,it is of great significance to study the instantaneous optimization strategy that comprehensively considers the adaptability of catalyst temperature and working conditions.In this paper,the coaxial parallel plug-in hybrid vehicle is taken as the research object.With the research goal of improving fuel economy and emission,the energy management strategy of plug-in hybrid vehicle considering catalyst temperature is studied.The research contents are as follows:(1)Taking the plug-in hybrid vehicle as the object,analyzing its working mode and energy flow,using the combination of numerical calculation and experiment,built the engine,three-way catalytic converter,motor and power battery in Matlab/Simulink.The vehicle simulation platform,such as vehicle dynamics model and driver model,provides a model basis for the design and verification of energy management strategies.(2)Analyze the principle of minimum value,explain the relationship between Equivalent Consumption Minimum Strategy(ECMS)and the principle of minimum value,and provide theoretical basis for ECMS strategy.At the same time,an ECMS strategy is established with the state of charge(SOC)as the state variable and the motor torque as the control variable.Applying the ECMS strategy to the CS phase of the CD-CS(Charge Depleting/Charge Sustaining)strategy solves the fuel economy at this stage.Through simulation,the influence of mileage and initial SOC on the optimal equivalent factor is analyzed.The genetic algorithm is used to establish the optimal equivalent factor map based on mileage and initial SOC of the battery,which provides the basis for the equivalent factor value.(3)For the plug-in hybrid vehicle,which has a large-capacity battery and the temperature of the three-way catalyst is easy to be in an abnormal working temperature when the ECMS strategy is applied;an ECMS strategy considering the catalyst temperature is proposed.At the same time,in order to solve the drawback that the battery power is not exhausted in the ECMS strategy considering the catalyst temperature under the fixed equivalence factor,an Adaptive Equivalent Consumption Minimum Strategy(A-ECMS)considering the catalyst temperature is proposed.Finally,the fuel economy and emissions of the strategy are verified under NEDC and WLTC cycle.