Study On Electromagnetic-mechanical Resonance Of Permanent Magnet Synchronous Motor With Converter Supply

Nowadays,the permanent magnet synchronous machine(PMSM)with converter supply has been widely used in many fields.In some certain occasions,the electromagnetic vibration and noise problems of PMSM are very serious,which affect the machine operation stability and working reliability.Therefore,in this paper based on the National Natural Science Foundation Project "Research on the electromagnetic vibration key foundational issues of permanent magnet synchronous machine with converter supply"(51737008),the author carries out a systematic study on the PMSM in terms of vibration analysis.The main research is summarized as follows:1.Analytical calculation method of magnetic field in PMSMAn intensive study about the magnetic field analytical prediction in PMSM has been carried out,which lays the foundation for the following research about electromagnetic vibration.An analytical method for predicting the magnetic field of surface-mounted PMSM(SPMSM)has been proposed.The method can take into account the effect of magnetic saturation and rotor eccentricity,the high precision of which was verified by making comparison with the finite element method(FEM)predictions.Then the analytical method about magnetic field prediction of V-shaped interior PMSM(IPMSM)was proposed.The existing division method do not apply to this machine.Hence,a new division method with respect to V-shaped IPMSM was given,and the machine was divided into several subdomains by this method.On this basis,the theoretical derivations of the general solutions of vector potential in subdomains and the boundary conditions between adjacent subdomains were exhibited.According the boundary conditions,the vector potential solution in each subdomain and magnetic field could be obtained.This analytical method was further improved to predict the magnetic field of V-shaped IPMSM with non-uniform air-gap.Based on the proposed method,the governing functions about electromagnetic force wave of V-shaped IPMSM,including the amplitude,rotating speed,frequency and phase angle parameters,was derived to conduct the fast and accurate calculation of electromagnetic force wave,which lays the foundation for the depression of electromagnetic vibration.2.Torsional vibration analysis of the PMSM with converter supplyDue to the effects of PM magnetomotive force(MMF)harmonics,rotor slot,stator current harmonics and magnetic saturation,the electromagnetic torque of PMSM contains rich harmonics.The torque ripple would lead to obvious torsional vibration,which has adverse effect on machine operation stability.Though the FEM can be adopted to calculate the machine electromagnetic parameter,it cannot be used to analyze the machine torsional vibration phenomenon directly.The mechanical-electromagnetic vibration analysis model of SPMSM was proposed,which contained the converter model,the machine model,the mechanical load model,and the control system model.The voltage equation established in dq rotating coordinate system cannot take into account the effect of cross coupling and magnetic field harmonics.Hence,an improved voltage equation of SPMSM was given for modeling magnetic saturation and magnetic field harmonics effects.Combining with the motion equation,an accurate mathematic model of SPMSM was established.On this basis,the torsional vibration analysis model about SPMSM was established.The study to explore the influence of variable speed adjustment,load mutation,load periodic change and converter current harmonic on machine torsional vibration was conducted based on the proposed model,which lays the foundation for the suppression of torsional vibration in SPMSM with converter supply.By the similar method,the torsional vibration simulation model about IPMSM was established.The research to explore the influence of control strategy and control system parameters on machine torsional vibration was then conducted.3.Torsional vibration suppression of the PMSM with converter supplyThe structures of step-skewed PM and non-uniform PM were adopted to weaken the torsional vibration of SPMSM.In this paper,the torsional vibration analysis models about these two machines were established.And the torsional vibration under variable speed adjustment and load mutation conditions were analyzed.The simulation results verified the effectiveness of two structures in the suppression of torsional vibration.An analytical method of magnetic field prediction in saturated non-uniform SPMSM was also proposed to conduct the fast and accurate calculation of magnetic field during this process.The optimized SPMSM was designed to suppress the machine torsional vibration.In machine design process,the hybrid methods of changing winding configuration mode and PM structure were adopted to improve the suppression effect.The prototype experiment was conducted to verify the effectiveness of this method.The improved control strategy was also proposed to weaken the electromagnetic torque ripple and torsional vibration of PMSM.The torque harmonics of IPMSM are complex.Hence,it is difficult to weaken the torque harmonics from different sources.In this paper,an improved control strategy of IPMSM was proposed.The electromagnetic torque equation considering the effect of magnetic field harmonics and cross coupling was derived.An optimized objective function was further established based on the torque equation,which was adopted to determine the current value combining with the optimization algorithm.The electromagnetic torque harmonics was canceled out under this condition.The proposed control strategy was adopted to control the machine operation,and the simulation results verified the effectiveness of this control strategy in suppressing torsional vibration.4.Rotor radial vibration analysis of the SPMSMThe rotor of PMSM is affected by the mechanical force and electromagnetic force,which suffers from complex nonlinear vibration.Aiming at this problem,the systematic analysis about rotor radial vibration was conducted.For the SPMSM neglecting stator slot,the governing function of radial electromagnetic force acting on rotor outer surface of machine with rotor eccentricity was derived combining with the proposed analytical method and magnetomotive force-magnetic permeability method.On this basis,the influence of rotor eccentricity on machine electromagnetic parameters and radial electromagnetic force was analyzed.Then the electromagnetic-mechanical motion equation about rotor radial vibration was established based on the Lagrange equation.The nonlinear equation was solved by the minor parameter method to derive the radial vibration amplitude function and phase angle function.The criteria to evaluate the radial vibration stability was also given.For the machine considering stator slot effect,the rotor radial vibration analysis model of SPMSM was proposed.And this model was adopted to analyze the influence of inherent magnetic force on rotor radial vibration under open-circuit condition.Finally,the mathematic model of SPMSM including electromagnetism,rotation and radial vibration was established.Combining with the SPMSM model,converter model and control strategy,the radial vibration simulation model of SPMSM with converter supply was established,which was further adopted to study the radial vibration phenomenon during start-up and load mutation processes.The corresponding conclusions were also drew.