Optimization Research On Sound Quality Of Drive Motors Considering Harmonic Currents

Thanks to the support of national policy and efforts paid by automobile enterprises on electrification transformation,new energy vehicles’ market penetration has been rising in recent years.Electric vehicles have already become a vital option for consumers.As the power unit of an electric vehicle,drive motor’s NVH performance makes a great difference to passengers’ ride comfort.In the meanwhile,sound pressure level can no longer reflect passengers’ subjective auditory sensation accurately.Sound quality should be considered while developing NVH performance of drive motors.This paper sets sound quality as the optimization target of a drive motor’s electromagnetic noise,and takes harmonic currents which have considerable impact on electromagnetic noise as the research focus.A nonlinear analytical radial electromagnetic force model and an electromagnetic noise prediction model are established to analyze the contribution by harmonic currents on electromagnetic force and noise at test point progressively.Electromagnetic noise prediction model and sound quality prediction model are combined to optimize the currents’ parameters using genetic algorithm,thereby sound quality of the drive motor’s noise is effectively improved.First of all,near-field noise of an IPMSM drive motor was gathered.After summing up the order characteristic of various noise sources,the noise orders aroused by odd order harmonic currents were identified and their contribution on total sound pressure level was analyzed.Based on psychoacoustic objective parameters and the sound quality prediction model developed by the research group,the noise orders which had great impact on sound quality were determined.Secondly,aimed at radial electromagnetic force which was the main source of the electromagnetic noise,a nonlinear analytical model considering stator and rotor slotting as well as magnetic saturation was established.Its precision was verified by FEM simulation results.A qualitative analysis of the contribution by currents’ armature reaction magnetomotive force and permanent magnetic magnetomotive on each electromagnetic force order was given.Furthermore,a quantitative analysis of electromagnetic force’s spatiotemporal distribution was given based on the nonlinear analytical model.Then,a structure model of the drive motor was established and its accuracy was verified by modal test.A magnetic-structure-acoustic coupling simulation model was built by jointing the structure model and the finite element model of drive motor to simulate electromagnetic noise.By comparing simulation results and tested results,the coupling model’s correctness was proved.Noise transfer function of each stator tooth towards the noise test point was calculated using the coupling model.Meanwhile,concentrated electromagnetic force on each tooth was computed by compound cotes formula based on the nonlinear analytical model.According to linear superposition method,fast prediction of electromagnetic noise was achieved.Thus,the contribution on sound pressure level by each electromagnetic force order was analyzed.Finally,sound quality was set as the optimization objective while considering drive motor’s torque pulse.On the basis of electromagnetic noise prediction model and sound quality prediction model,genetic algorithm was used to optimize the parameters of odd order harmonic currents.Motor control system in Simulink,inverter model in Simplorer and finite element model of the drive motor were jointed to perform the harmonic injection simulation.By comparing the noise sound quality before injection with that after injection,the effectiveness of injecting harmonic currents was proved.