Research On Electromagnetic Noise Of Ipmsm For Electric Vehicles Under All Operating Conditions

Electromagnetic noise has the characteristics of high frequency,time-varying and easily resonant when the interior permanent magnet synchronous motor（IPMSM）operates under all conditions.Coupled with the complex effects of static/dynamic eccentricity,current harmonics and segmented inclined poles on the electromagnetic noise characteristics,it makes the forward prediction,diagnosis and optimization of electromagnetic noise very difficult.Therefore,it is necessary to research the electromagnetic noise characteristics and optimization method of IPMSM for electric vehicles under all operating conditions.（1）Research on mechanism of air-gap magnetic field and electromagnetic force wave of IPMSM.The mechanical-electric-magnetic analytical model,finite element models and magnetic circuit model of IPMSM under all operating conditions are established,and the direct measurement experiment of air-gap magnetic field is carried out.It reveals the characteristics of air-gap magnetic field and electromagnetic force wave in IPMSM excited by all harmonic currents.The research results show that:When the fundamental current/low-order odd-numbered harmonic armature reaction magnetic field and permanent magnet magnetic field（PMMF）interact,the frequency of electromagnetic force wave is an even number of the fundamental frequency of the power supply,that is,2kf_c.When the low-order even-numbered harmonic armature reaction magnetic field and PMMF interact,the frequency of the electromagnetic force wave is kf_c.Furthermore,under the high sideband harmonic frequency armature reaction magnetic field and PMMF interact,the frequency of electromagnetic force wave is k₁f_s±（k₂±n）f_c.For the motors with integer slots,the spatial order of electromagnetic force wave can be written as 2kp±mQ.（2）The mechanical-electrical-magnetic-solid-acoustic multi-physical field coupling simulation model and analysis of IPMSM.Firstly,both experimental modal analysis and simulation modal analysis of IPMSM stator assembly are accomplished.Then,the accurate simulation calculation models of steady and unsteady electromagnetic vibration and noise are established.They are used to calculate the vibration and noise in steady condition,unsteady acceleration condition and unsteady regenerative braking condition.Finally,the accuracy of the steady-state and non-steady-state electromagnetic vibration noise calculations were verified by vibration and noise experiments.The results show that the frequency characteristics of vibration and noise in the acceleration condition and the regenerative braking condition change with the rotate speed,showing obvious order characteristics.The main components are the integer multiples of the number of poles 2kpf_r with unidirectional radial shape and the higher order frequency around the bi-directional umbrella switch frequency f_s±（k₂±n）f_c with bi-directional umbrella shape.The predicted noise peak point is the same as the experimental noise peak point,which appears at the position of the resonance speed,and the error with the experimental peak is within4%.（3）Analysis of the influence factors of vibration/noise in IPMSM.The influence regularity of various influencing factors on the electromagnetic noise is calculated and analyzed by using the mechanical-electrical-magnetic-solid-acoustic multi-physical field coupling model of IPMSM in steady/unsteady conditions.The results show that static eccentricity does not change the frequency characteristics of electromagnetic noise,dynamic eccentricity causes the appearance of f_n±f_r and f_n±2f_r of electromagnetic noise.As the degree of static/dynamic eccentricity increases,the amplitude of electromagnetic noise tends to increase.Under the same degree of eccentricity,the frequency components of the electromagnetic noise with dynamic eccentricity are more abundant,and the amplitude of the total SPL is greater than that with static eccentricity.2kf_c will introduce electromagnetic noise harmonics with odd power supply frequency.k₁f_s±k₂f_c will introduce the electromagnetic noise harmonic whose frequency is k₁f_s±（k₂±n）f_c.Such electromagnetic noise is often difficult to be distinguished in the steady state,while it shows the bidirectional umbrella orders in the noise order diagram in the unsteady condition.Moreover,the electromagnetic noise of the IPMSM can be significantly suppressed by the segmented skewed poles.（4）Experimental testing and analysis of vibration noise of IPMSM.The vibration noise under acceleration conditions with different load torque and regenerative braking conditions with different braking torque are tested in the semi-anechoic room.It reveals the order characteristics of the noise distribution in all operating conditions,identifies the order source and analyzes the order and sound quality characteristics of vibration noise under different load torque/brake torque.The results show that the noise orders mainly include seven types:low-frequency integer orders,low-frequency fractional orders,integer orders of the number of poles,pk±1 orders,fractional orders of the number of poles,high orders near the switching frequency and resonance bands.During the acceleration/feedback braking process,the AI index generally decreases with increasing speed,but is non-linear;the total SPL and Loudness generally increase with increasing speed,but the peak point does not appear at the highest Speed;the Sharpness of the acceleration/feedback braking process is evenly distributed over the full speed range.The load/braking torque has little effect on AI index,but is proportional to the SPL,Loudness and Sharpness.（5）Electromagnetic noise diagnosis and multi-objective optimization of IPMSM.First,the forward diagnosis and optimization method of the electromagnetic noise of the IPMSM are presented and the combination of design and optimization of electromagnetic noise is realized.Afterwards,the multi-objective optimization of the electromagnetic force wave,average torque and efficiency is carried out by applying the finite element numerical iterative method and the intelligent algorithm iterative method respectively.Finally,the effectiveness of the multi-objective optimization is verified by the electromagnetic noise simulation results.The results show that,the appearance of noise peak under the full-speed working condition is mainly because the electromagnetic force harmonics stimulate the inherent mode of the motor and cause resonance.The performance,efficiency and noise of IPMSM can be optimized by multi-objective numerical iterative method based on the electromagnetic finite element parametric model in Maxwell,VBS script and the NSGA-Ⅱgenetic algorithm and multi-objective intelligent algorithm iteration method based on BP neural network model and the NSGA-Ⅱgenetic algorithm.After optimization,the electromagnetic force wave of the motor is reduced by 34.2%,the average torque is increased by 7.6%,the efficiency is increased by 1%,and the electromagnetic vibration noise level was reduced by 24.4%.