Research On Potential Of Energy-Saving From Electric Vehicle Regeneration

Energy shortage issues have become increasingly pronounced nowadays.A large number of studies on new energy automobiles have been carried out as the focus of future development,among that,the pure electrics are drawing much more emphasis.However,the serious existed problem of lack of mileage range hinders the further development of pure electrics.As we know,the significant method of increasing the mileage range is to recycle the braking energy with the regenerative braking technology.So,how to tap the potential energy-saving capacity of regenerative braking becomes a research hit on electric vehicles.In this paper,the energy flow paths of driving and braking processes are studied under the key factors which are influencing the energy recovery rate of automobile regenerative braking.Through the theoretical analysis and numerical calculation,the energy-saving potential capacity of regenerative braking of pure electric passenger vehicles and commercial vehicles are emphatically discussed under different driving situations.Firstly,the dynamical characteristics of braking process are described,and the structure form and basic principle of the regenerative braking system of electric vehicles are introduced.It is proposed that the speed,braking power and braking deceleration are the important factors influencing the energy flow in regenerative braking,which provides the theoretical foundation to the braking force distribution strategy for the maximum regenerative braking.Secondly,the typical pure electric passenger vehicles and large commercial vehicles are applied in LMS AMESim to establish the forward simulation model.The model is composed of key component model of powertrain,key component model of braking system,longitudinal dynamics model,closed-loop driver model and so on.At this basis,the standardization and verification are carried out with the experimental data.In order to study the energy flow and loss in the process of driving and braking,three common test cycle conditions of passenger vehicles,FTP-75,NEDC,JC08,together with two of commercial vehicles,CCBC,NYCC,are selected to apply to the simulation of pure electric passenger cars and commercial cars with the forward simulation model,respectively.The braking energy distribution under different vehicle speed,braking power and braking deceleration is mainly analyzed.Then this paper summarizes the total amount of kinetic energy that can be regenerated by the regenerative braking module of some particular vehicle under a certain driving condition.On this basis,the high efficiency range of braking energy recovery is determined.Finally,the braking force distribution strategy for the maximum regenerative braking is further analyzed aimed at traditional parallel regenerative braking system and advanced mechanical-electrical regenerative braking system from the point of front and rear axle distribution.That is,on the premise that relative policies and regulations are guaranteed,as well as that the front wheel is not first to be locked,the driving force is allocated to the driven wheel as much as possible(for passenger cars,the driving force is mainly allocated to the front wheels,rather for the commercial vehicles is rear wheels).And the regenerative braking should be employed by the motor as much as possible in the premise of ensuring the braking strength.The braking force distribution strategy based on the maximum regeneration braking of parallel hybrid braking system and integrated hybrid braking system are formulated.Combined with the selected test cycle conditions,the simulation of the distribution strategy is carried out.The results demonstrate that the percentage of regenerative braking energy occupied in the total braking energy increase apparently.And for the optimization of integrated regenerative braking of pure electric passenger vehicles,the percentage of regenerative braking energy can reach more than 80%,increasing the braking energy recovery rate greatly.