Investigation On Power Factor And Optimization Design Method Of V-type Magnetic Field Modulation Permanent Magnet Motor

With the gradual depletion of fossil fuels globally and the increasing severity of environmental pollution,electric vehicles have gradually become one of the main means of transportation for people’s daily travel.Among them,the distributed hub motor drive system has gradually become one of the important development directions for future electric vehicle design due to its highly integrated internal limited space and flexible control.Magnetic field modulated permanent magnet motors have become one of the potential applications of hub motor drive systems due to their low speed and high torque output capabilities.However,due to the relative increase in the number of pole pairs and leakage flux of magnetic field modulated permanent magnet motors,their power factor is usually relatively low,which limits their application prospects in the field of hub motor drive systems.Therefore,in the field of electric vehicle hub motor drive systems,improving the power factor characteristics of magnetic field modulated permanent magnet motors is a research hotspot and difficulty.This article proposes a hierarchical optimization design method for improving the power factor characteristics of magnetic field modulated permanent magnet motors based on the theory of magnetic field modulation,using air gap harmonics as a bridge.In order to demonstrate the feasibility of the proposed optimization design method in detail,this paper takes a V-type flux modulation permanent magnet(V-TFMPM)motor as the research object,and theoretically deduces and optimizes the electromagnetic performance related to the motor power factor.The specific summary is as follows:Firstly,this article introduces the research background and significance of the topic,and outlines the current development status of electric vehicle hub motor drive systems.Based on the above background introduction,the development status of magnetic field modulated permanent magnet motors and the research status of power factor of magnetic field modulated permanent magnet motors are introduced.Subsequently,based on the working principle of magnetic field modulation,this article divides the air gap synthetic magnetic field into permanent magnetic field generated by permanent magnets and armature magnetic field generated by armature reactions.From the perspectives of magnetic potential and magnetic conductivity,the distribution patterns of magnetic field air gap magnetic density and harmonics are analyzed.And based on the mechanism of air gap harmonic generation,the basic theory of power factor of magnetic field modulated permanent magnet motors has been improved.Secondly,based on the analysis of the working principle and power factor mechanism of magnetic field modulation mentioned above,a hierarchical optimization design method for power factor is proposed.This method divides the power factor optimization process of magnetic field modulation permanent magnet motors into permanent magnet flux layer and synchronous inductance layer,and uses dual parameter scanning,sensitivity analysis,and response surface methodology to optimize their design.Once again,in order to verify the feasibility of the hierarchical optimization design method proposed in this article,an optimization design method was validated and analyzed using a V-shaped magnetic field modulated permanent magnet motor as an example.Based on the above theoretical derivation and optimization design of the motor,the electromagnetic performance before and after the optimization design was compared and analyzed using finite element simulation software.Among them,the relevant electromagnetic performance mainly includes the no-load performance and load performance of the motor.The comparative analysis results prove the feasibility of the hierarchical optimization design method proposed in this article.Finally,based on the hierarchical optimization design method proposed in this article,a V-shaped magnetic field modulated permanent magnet motor was manufactured and an experimental platform was built to test the basic experiments related to the motor power factor.The experiment mainly includes the no-load back electromotive force,power factor,dynamic and steady-state operating characteristics of the motor.The experimental results are basically consistent with the simulation analysis,further proving the effectiveness of the hierarchical optimization design method and laying the theoretical foundation for magnetic field modulated permanent magnet motors in distributed hub drive systems.