Study On Energy Management Strategy Of Plug-in Hybrid Electric Vehicle With Consideration Of Battery Aging

The quantity of automobile ownership in our country is growing rapidly with the rapid development of the economy,which makes environmental problem and energy issues the human face sharper.Developing new energy vehicles has become consistent strategic choice of the world and inevitable trend of the automobile industry.The Plug-in Hybrid Electric Vehicle(PHEV)can not only make use of the technical achievements in the traditional automobile industry,but also reduce the emission,reduce the fuel consumption and ensure the endurance mileage of the vehicle to a certain extent,which has become the ideal type of the transition of the Hybrid Electric Vehicle(HEV)to Blade Electric Vehicle(BEV).Due to the constraints of design technology,manufacturing process,constituent materials,energy density,safety performance and battery management system,there are still problems in the cost,life,quality and safety of the battery.These problems undoubtedly affect the performance of the PHEV's cost of acquisition,cost-in-use and durable years.Judging from the current products of new energy vehicles,the life of battery still can not meet customers' expectations.When the battery life is terminated,there are three main choices for consumers: the first is to change the battery by OEM according to the warranty period or replace the battery by consumers,but at present,the warranty period of battery is shorter than that of the new energy vehicles,and the replacement cost will bring OEM or consumers the second cost;the second is to scrap battery and use PHEV as traditional fuel car,which will reduce the economic performance of vehicle;the third is to continue to use the discarded battery,which will increase the frequency of the battery safety accidents when vehilce is in high discharge powers.At present,battery aging has not been taken into consideration in most of mainstream energy management strategies for PHEVs,even though it is an important parameter that affects the cost and performance of the vehicle.Therefore,it is necessary to adjust the working state of the battery in order to improve the service life of the power battery,optimize the design of the vehicle and reduce the cost of consumers.This paper mainly introduces battery aging in the control strategy from the following two aspects: one is to adjust the working state of battery to reduce the frequency of high discharge and charge rate;the other is to match the battery life in the control strategy with the maximum charge and discharge power to prolong service life of battery further.Based on the purpose and research route,the main contents of this paper are as follows:(1)By consulting relevant literature,research status of energy management strategies for PHEVs and battery capacity attenuation models are summarized.In view of the question that early replacement which is caused by short battery life relatively of the battery will result in seaond cost consumption,the main research framework is determined.(2)The dynamic system structure of target vehicle is analyzed,and parameters of driving motor,engine,generator,battery pack and transmission ratio for drive system are matched on the basis of dynamic performance and parameters of target motorcycle type.On this basis,the numerical models of the engine,the driving motor and the generator,and PNGV model for monomer of NCM523 lithium-ion power battery are set up.(3)The working principle of lithium-ion power battery,the main influencing factors of life,the mechanism of life decay and the test data of life test are analyzed.The NCM523 battery life model with capacity as the characteristic of it is established and verified.(4)The life of NCM523 battery is introduced into the CD-CS control strategy by reducing the high rate charge and discharge frequency of the battery.The main implementation methods are as follows: according to the lower limit efficiency method,the lower limit of the efficient working area of the engine is determined,and the maximum torque curve is used as the upper limit of it.The threshold of limited power of NCM523 battery is decidede after analysing the effect of charge and discharge rate on the battery capacity consistency.(5)The life decay of the battery is further introduced in the control strategy by matching threshold of charge and discharge power with the life state of it.The vehicle lifetime,fuel consumption and cost of vehicle under different control strategies are simulated by using the vehicle model built in MATLAB/Simulink.The results show that the energy management control strategy considering battery aging can not only extend the service life of the battery t,but also reduce the using cost of the vehicle to a certain extent.