Loss Analysis And Control Strategy Of Hybrid Electric Vehicle Regenerative Braking System

In recent years,research on new energy vehicles has entered a period of rapid development.Hybrid vehicles are one of the ideal transition models for replacing new cars with new energy vehicles because they can reduce emissions,maintain good economy and have reliable mileage.Regenerative braking is an important technology for hybrid vehicles to improve their cruising range.When the vehicle is braking,the traditional car converts the kinetic energy into frictional heat energy,and the regenerative braking converts the kinetic energy into electrical energy through the motor and stores it in the battery,thereby achieving the purpose of recycling.The whole regenerative braking recovery process consists of two power flows,one electric brake power flow and one hydraulic brake power flow;the hydraulic brake can ensure the safety and stability of the whole vehicle due to the mature technology,and the electric brake The recovery efficiency of the power flow and the loss of each part directly affect the amount of energy recovered.This paper aims to use a front-and-rear dual-motor hybrid vehicle as the research platform.Firstly,the loss mechanism of the permanent magnet synchronous motor in the electric brake power flow transmission process is analyzed,and then the electrical power flow of various key components such as CVT is considered comprehensively.Based on the impact of loss,the joint efficiency model of front and rear axles is established respectively,and the corresponding regenerative braking distribution strategy is proposed.The specific research contents are as follows:(1)The mechanical analysis of the whole vehicle before and after the study of the two-motor hybrid vehicle was carried out and the I curve was derived.The characteristics of the three types of allocation strategies: ideal braking force distribution method,maximum energy recovery braking force distribution method and parallel braking force distribution method are briefly described.Relevant ECE braking regulations are introduced to restrain the front and rear braking force.To lay the foundation for proposing his own distribution strategy.(2)In order to accurately reflect the efficiency change of the regenerative braking process,the loss mechanism analysis is carried out for the three important parts of the motor,CVT and battery in the electric braking process,specifically the copper loss,iron loss and remaining loss of the motor;CVT The sliding loss of the steel strip,the loss caused by the deformation of the pulley,the slippage loss of the metal sheet;the temperature influence and the internal resistance loss of the lithium iron phosphate battery.Establish their own models and motor controllers.(3)Analyze the electric brake power flow during the regenerative braking process of the whole vehicle,and divide the electric brake of the whole vehicle according to the front and rear axles,and establish the combined efficiency model of the front axle(CVT-ISG)combined efficiency model and the rear axle(PMSM).Combined with the front axle efficiency model,the optimal CVT speed ratio is obtained by algorithm optimization.The input and output characteristics of the front and rear axle joint efficiency model are analyzed,and the operating areas of the front and rear axle joint efficiency model are fully considered by various influencing factors.Then a new braking force distribution strategy for regenerative braking is proposed.(4)Based on the MATLAB/Simulink simulation platform,the backward simulation model and loss model of the regenerative braking system of the front and rear dual-motor hybrid electric vehicles are built.They are regenerated under three typical braking conditions and NYCC and FTP-72 cycle conditions.Brake simulation analysis.The simulation results of typical braking conditions reflect the recovery efficiency and the loss and proportion of various important components under the braking condition;the typical cycle conditions reflect the power,front and rear motor braking torque,combined efficiency,and verified The motor controller and braking force distribution strategy proposed in this paper is feasible.