Research On Energy Feedback Control System Of Four Wheel Motor Pure Electric Vehicle

With an increasing number of electric vehicles,the Chinese electric vehicle industry has flourished in recent years.However,the short cruising distance becomes a main factor limiting its further development.Compared with fuel vehicles,electric vehicles are regenerative in terms of braking energy,thus having great potential in urban traffic conditions with frequent vehicle start-stop,acceleration,and deceleration.Therefore,it is of abundant significance to improve the cruising distance by optimizing the feedback system of braking energy so that the braking loss could be recycled,stored,and reused.Focusing on the demand for the energy feedback system of the existing four-in-wheel motor electric vehicles,this paper proposes a novel topology of the four-in-wheel motor pure electric vehicle,whose energy feedback system is investigated indeed.Based on the proposed topology,the drive control system of the in-wheel permanent magnet synchronous motor(PMSM)is designed.The mathematical model of the PMSM is deduced in detail,and the principle of the space vector pulse width modulation is characterized.The inner loop decoupling strategy is presented from the perspective of the stator flux-oriented control.The inner loop controller and the outer loop controller are designed on the basis of the constructed model.The simulation results prove the effectiveness of the designed control strategy.Secondly,the dual active bridge DC/DC converter(DAB)and its control strategy are investigated.The steady-state work modes of DAB with single phase-shifted modulation are analyzed,thus establishing its simplified small signal model for the dynamic behavior analysis and controller design.A feedforward controller for decreasing the load current fluctuation is proposed to improve the dynamic and robustness of the converter.The waveforms and measurement data are obtained by MATLAB/SIMULINK simulation and verifier experiment,which provide validation for the accessibility and practicality of the strategy.Furthermore,on the basis of the DAB converter,PMSM and its drive control system,the energy feedback system of the electric vehicle is realized.The work modes with two different power flow directions are introduced in detail.The dynamic model of the electric vehicle is constructed,and the logic threshold control strategy for realizing regenerative braking is derived under the constraints defined by the braking torque distribution of the front and rear axles.The co-simulation of AVL-Cruise and MATLAB under the FTP-75 cycle condition is conducted to obtain the braking feedback torque of the front and rear axle motors and the SOC state of the battery,which verifies the effectiveness of the energy feedback control system.Finally,the DAB converter,PMSM and its drive control system are integrated for overall simulation and related experiments.The hardware and software parts of the DAB converter and the PMSM drive system are designed.Accordingly,the experiment for regenerative braking is carried out,and the relevant experimental results are analyzed.