Research On Torque Ripple Suppression And Performance Optimization Of Permanent Magnet Motors With Fractional-slot Concentrated Windings

The drive motor is one of the core components of the electric vehicle power system,and the performance of the motor is directly related to the driving and safety of the vehicle.Among many types of motors,permanent magnet synchronous motor is the preferred object of electric vehicle drive motor with its high power density,high efficiency and good reliability.Fractional-slot concentrated winding has the advantages of short end length,simple assembly process and low cost,and is widely used in servo systems,household appliances,wind power generation and other fields.It is of great practical importance to study the use of fractional-slot concentrated windings in permanent magnet synchronous motor and apply it to electric vehicle drive motor.In this thesis,based on the theory of fractional-slot concentrated windings,the slot-pole combination constraints of fractional-slot concentrated windings are elaborated,and the winding,stator and rotor structures are compared and analyzed.According to the design requirements and design methods,the design and simulation calculations of the electric vehicle drive motor are carried out.In addition,the torque composition,and the causes of torque ripple of the permanent magnet synchronous motor are modeled and analyzed,and the intrinsic mechanism of torque ripple caused by electromagnetic torque and cogging torque is investigated.Moreover,the research direction of suppressing torque ripple by improving the air gap magnetic field distribution is clarified.After that,the rotor notch theory is proposed and a comprehensive structural parameter design of the rotor notch is carried out,and seven design parameters are proposed.On this basis,the effects of the rotor notch on electromagnetic torque and cogging torque and the effect of suppressing torque ripple are investigated,respectively.Then,in order to improve the torque performance of the motor,a multi-objective optimization method is proposed to ensure that the average output torque is not affected while reducing the torque ripple,and performance indexes such as efficiency,current density,and output power are taken into account as constraints.The computational efficiency is greatly improved by constructing a prediction model and performing fitting accuracy analysis to replace the timeconsuming and inefficient finite element simulation.After the optimization,the torque ripple is suppressed and the average torque is improved.Finally,the reliability of the proposed method is demonstrated by prototype testing and experimental verification.In general,the overall performance of the permanent magnet synchronous motor with fractional-slot concentrated windings is satisfactory,and the torque performance can be improved by the appropriate optimization method,which is suitable as a drive motor for electric vehicles.In addition,the multi-objective optimization method proposed in this thesis is also applicable to the optimization of other design parameters and performance of the motor,which can significantly improve the optimization speed while ensuring the accuracy of the results.