Research On Torque Ripple Optimization Of Interior Permanent Magnet Synchronous Machines

The interior permanent magnet synchronous machines(IPMSM)have the advantages of high-power density,wide speed range and high overload capacity,so they are widely applied to the field of electric vehicles.The torque ripple of IPMSM is relatively large,which will affect the comfort of passengers.In this paper,the main research work of this paper contains the following three parts:Firstly,the generation mechanism of torque ripple is analyzed,and the analytical formula of torque ripple is derived.As shown in the analytical formula,the saturation degree of magnetic circuit has a great influence on the torque ripple of the machines.The saturation degree of magnetic circuit cannot be taken into account by the analytical method,so the equivalent magnetic circuit method is applied to analyze the influence of saturation degree on torque ripple,and the influence of different load conditions on torque ripple is compared.Besides,the d-axis and q-axis inductances under different loads are analyzed.Then the torque ripples at different rotor positions are considered by using dynamic magnetic equivalent circuit,and it is verified by a prototype.Secondly,the torque ripple is optimized in the two aspects which are machine design and current harmonic suppression.In the process of torque ripple suppression,the influence of the output torque is considered.When the torque ripple is suppressed from the perspective of motor design,three skew-pole methods are compared firstly.Then the effects of rotor eccentric and auxiliary slot on rotor surface on torque ripple are studied,and the cogging torque,permanent magnet torque ripple and reluctance torque ripple are taken into account.When the torque ripple is suppressed from the perspective of motor control,the proportional integral resonance control is used to suppress the harmonic components caused by dead time effect and other factors.Therefore,the sinusoidal characteristics of the current waveform is improved.Finally,a multi-objective optimization method combining the Taguchi method with the multi-level Kriging model is proposed.In the process of motor optimization,torque ripple and output torque are determined as the optimization objectives,and different parameters have different influence on these two objectives.Firstly,the influence degrees of each parameter on these two objectives are obtained according to the sensitivity analysis,and Taguchi method is used to optimize the parameters which have less influence on these two objectives.Besides,the multi-level Kriging model is applied to optimize the parameters having great influence on objectives.This method improves the optimization accuracy and effectively reduces the finite element calculation burden in the optimization process.Then the V-shape skew-pole method is applied to the optimized motor,and the optimized model is co-simulated with Matlab Simulink and Ansys Simplorer.And the torque ripple is obviously suppressed.