Design,Analysis,and Optimization Of Double-Stator Flux-Modulated Permanent-Magnet Motor

Recently,with the depletion of fossil fuels and worsening environmental pollution,electric vehicle(EV)industry has been developed rapidly and widely applied due to merits of low carobon emission and environment friendly.Permanent magnet motors have been wide applied as the driving motor of electric vehicle,mainly due to its merits of high torque density,high power density,and high efficiency.However,with the increase of complexity of modern transport,due to increasing critical operation environment and various driving cycle,it poses higher design requirments for driving motors of EVs.Double stator motors have attracted considerable attention of researchers in motor research field,due to its merits of high torque density,high space utilization,flexible operation modes.In this project,design concepts of flux modulated motors are incorporated into double stator permanent magnet motors,and a new double-stator flux-modulated permanent-magnet(DS-FMPM)motor is proposed and investigated,which exhibits high torque output capability and compact space.In this paper,the research of DS-FMPM motors mainly including following aspects: theoretical analysis,motor optimization design,finite element analysis verification,and experimental research.The main contents of this dissertation are presented as follows:Firstly,in this paper,in order to satisfy increasing critical design requirements for driving motors of new energy vehicles,design concept of flux modulated motor is introduced into double stator motor,a novel double stator flux modulated permanent magnet(DS-FMPM)motor.Based on flux modulation theory,the operation mechanism of the investigated DS-FMPM motor is clarified in detail.And three fundamental elements of flux modulation theory(magnetic source,flux modulator and filter)are mathematically explained.Then,the relationship between airgap flux harmonics and motor performances are investigated,including flux linkage,back-EMF,cogging torque,and output torque,which lays a solid foundation for the following optimization design.Secondly,the optimal split ratio of DS-FMPM motor is investigated.Considering the characteristics of multiple operation modes of DS-FMPM motor,design requirements for whole DS-FMPM motor are arranged for the inner and outer motors,so the optimization model of inner and outer motors can be established.In addition,by means of multi-objective genetic algorithm,the optimal split ratios of inner and outer motor can be determined.Thirdly,based on general airgap flux modulation theory,an airgap-harmonic-based multi-level multi-objective optimization design approach is proposed for DS-FMPM motor.In the proposed optimization approach,according to the flux modulation process of airgap flux harmonics,motor design parameters are classified into three levels,namely,magnetic source level,flux modulator level,and armature winding level,so that the dimensions of optimization model can be reduced.And response surface method,sensitivity analysis,and multi-objective genetic algorithm is applied to design parameters of these three levels.Based on the tradeoff of optimization objectives,the final optimal design of DS-FMPM motor can be determined,which also provide a research path for the optimization of flux modulated motors.In addition,based on finite element analysis,electromagnetic performances of the DS-FMPM motor are systematically analyzed,including flux distributions,airgap flux distribution,no-load flux linkage,no-load back-EMF,cogging torque,inductance characteristics,torque characteristics,power factor,and loss characteristics.Simulation results proves the reasonability of the DS-FMPM motor structure and effectiveness of proposed optimization approach.Furthermore,based on the characteristics of control circuit and magnetic field of DS-FMPM motor,a field-circuit coupling dynamic demagnetization analysis method is proposed.By this method,dynamic demagenetization characterisitcs of DS-FMPM motor under different operation condition are investigated,such as rated load,overload,deep flux weakening,and three-phase short-circuit.It is noted that,by comprehensively considering the trajectories of d-q-axis current,faulty dynamic demagnetization analysis can be realized.By the detailed investigation of operation points of PMs,it is indicated that DS-FMPM exhibit higher operation points and strong demagnetization capability.Finally,a prototype DS-FMPM motor is manufactured for principal validation and the corresponding experimental platform is also manufactured and set up.The basic electromagnetic characteristics and variable-speed variable-load characteristics of DS-FMPM motor are tested.Experimental results verify the reasonability of the proposed DS-FMPM motor,which lays experimental foundations for the potential application of DS-FMPM motor in EVs.