Research On Magneto-thermal Coupled Motor Model For High Fidelity Electric Machine Emulator

Energy saving and environmental protection have gradually become the theme of automobile development.New energy vehicles,especially electric ones,have become the general trend.New energy vehicles are mainly driven by electric power,and they have extremely high requirements on the technical accuracy and stability of the motor control unit(MCU).Therefore,the MCU needs to undergo detailed and complete verification before it can be put into actual vehicle applications.The electric machine emulator(EME),as a semi-physical simulation platform,can replace the actual motor to complete the MCU test work.It has the advantages of high efficiency,energy saving and high reliability.The paper is oriented to the application of EME and aims to develop a magneto-thermal coupled mathematical model that can simultaneously simulate multiple internal characteristics of permanent magnet synchronous motors.In this paper,the in-depth analysis of the generation and influence mechanism of the electromagnetic characteristics of permanent magnet synchronous motors(including iron core magnetic saturation and cross-coupling,air gap magnetic field harmonic effects)is carried out,and the accuracy of the research conclusion is confirmed by the finite element simulation results.The paper establishes the distributed parameter model of the motor based on the distribution law of flux linkage under different current excitation and rotor position.According to the application requirements of the EME system,a three-dimensional back look-up table technology based on the coefficient fitting method is proposed,which together with the distributed parameter model constitutes the electromagnetic model of the target motor.The paper continues to study the cause of the thermal characteristics(loss,temperature rise phenomenon)in the motor and its coupling relationship with the electromagnetic characteristics.Based on the electromagnetic parameters,a calculation model of motor loss and temperature change is established to complete the positive coupling from magnet to heat in the motor.The paper quantifies the influence of thermal characteristics by means of loss and temperature rise equivalent current compensation,and completes the reverse coupling from heat to magnetism.This part of the model and the electromagnetic model together constitute the final research goal of the thesis,that is,the magneto-thermal coupled motor model for EME applications.In terms of the verification of the research results,the paper firstly carries out offline simulation verification based on the Matlab software for the accuracy of the main modules inside the magneto-thermal coupled model,including the distributed parameter model,back look-up table technology,and the calculation model of loss and temperature.The calculated values of the mathematical model are compared and verified with reference to the JMAG finite element simulation results under the same input conditions.Each module embodies a high simulation accuracy and can meet the development needs of the EME system.Secondly,based on Simulink software,this paper establishes a power-to-drag system between MCU and EME,and applies the magneto-thermal coupled motor model to the EME unit.In this paper,three typical steady-state and transient operating conditions of the motor are selected to conduct online simulation verification of the overall working performance of the EME test system.The research results show that the EME system can achieve stable operation under three working conditions,and the dynamic response speed is fast.It indirectly proves that the magneto-thermal coupled model studied in this paper is feasible and can meet the development and use requirements of the EME system.