Investigation Of The Integrated Motor-drive And Battery-charging System Based On Doubly Salient Motor For Electric Vehicles

The integrated motor-drive and battery-charging system of the electric vehicles could utilize the motor and the driving system to charge the battery,and thus the fast-charging could be realized without the additional charger or charging pile,where only a high power charging cable is needed,then the convenience of charging could be greatly improved.The doubly salient electromagnetic machine(DSEM)has the advantages of simple structure,high reliability,and low cost,so it has good application prospects for electric vehicles,however,the excitation loss deteriorates the efficiency and power density,hence,an integrated motor-drive and battery-charging system based on DSEM is proposed.The system has a cascade structure of a front-end DC/DC converter and an inverter,where the field windings of DESM are adopted as the inductances in the front-end DC/DC converter to eliminate the large inductance in the conventional integrated motor-drive and battery-charging system.Then the efficiency of the system could be increased,the current ripple during the charing mode could be lower,and no torque of DSEM is generated.In this paper,the topology,the control strategy and the operation characteristics of the system are analyzed and studied.Firstly,the novel topology of the integrated motor-drive and battery-charging system utilizing the DSEM is presented.Based on the analysis of the driving operation with boost mode and constant current charging operation with buck mode,the arrangement and turns of the multiplex field windings are designed.After that,the methematical model of DSEM is presented,and the methematical model of the three-phase PWM rectifier which utilizing the three armature windings of DSEM is derived.Due to the coupling relationships among the excitation current of DSEM,the output voltage of DC/DC converter,the speed and the armature current of the motor in the driving operation,the decoupling control strategy of speed and current closed-loop is deduced,and the power constraints between the input and output of the system is also analyzed.Then,an improved decoupling control strategy of power closed-loop is proposed to achieve the steady DC bus voltage.After that,the excitation current ripple and DC bus voltage ripple which affects the driving performance are analyzed and optimized,and the efficiency of the drive operation is researched.In the charging operation,the parameters of controller for the three-phase PWM rectifier are designed in detail,and the corresponding control strategy of the front-end DC/DC converter is given.Besides,the output voltage limitation of the three-phase PWM rectifier,the influence on the charging current due to the mutual inductances and the output torque are discussed in detail.Finally,the simulation models of the proposed system in the driving operation with MATLAB and the finite element co-simulation model for the charging operation by MATLAB and ANSYS are built to verify the corresponding control strategies.Based on these,the experimental platform which is composed of the power circuit based on the Si C MOSFET,the sampling and amplifying circuit,and the controller based on DSP and CPLD is implemented for the experiment.The proposed integrated motor-drive and battery-charging system have been carried out to verify the good steady-state and dynamic performance.