| With the rapid increase in the number of global vehicles,the rapid development of the vehicle industry is restricted by environmental pollution and the energy crisis.New energy vehicles reduces the use of fossil fuels and the emission of polluted gases.The rapid development of the new energy vehicle industry drives the demand for machines to rise sharply.At the same time,wide speed region is the demand of machines in new energy vehicles.In order to select and control machines suitably for new energy vehicles,analysis and calculation of torque-speed characteristics are essential.Usually,the fundamental component of the flux-linkage is used to calculate the torque-speed characteristics of machines,which have the sinusoidal waveform of flux-linkage.However,in the machines with large high-order harmonics in the flux-linkage,the large high-order harmonics in the flux-linkage will cause the significant distortion of the phase voltage and the reduction of the dc-link voltage utilization,which will affect the torque-speed characteristics of machines.Therefore,the calculation method of torque-speed characteristics considering kth-order harmonics(k≥2)in flux-linkage is proposed in this thesis for the machines with large high-order harmonics in the flux-linkage.Through this calculation method,the influence of high-order harmonics in flux-linkage on torque-speed characteristics can be investigated deeply,and the high-order harmonic which has the greatest influence on the torque-speed characteristics can be found.This method is used to analyze the torque-speed characteristics of variable flux reluctance machines(VFRMs)considering the high-order harmonics in flux-linkage,and to compare the influence of high-order harmonics on torque-speed characteristics of VFRMs and hybrid-excited variable flux reluctance machines(HEVFRMs)in this thesis.The research content of this thesis is conducive to achieving a wide speed range of this type of machines.The main content in this thesis is as follows:Firstly,the influence of high-order harmonics in flux-linkage on the phase voltage is analyzed theoretically.And the calculation method of torque-speed characteristics considering kth-order harmonics in flux-linkage is proposed for the machines with large high-order harmonics in the flux-linkage.Secondly,the influence of the high-order harmonics in flux-linkage on torque-speed characteristics of VFRMs with different rotor poles is investigated from the aspects of back-EMF,electromagnetic torque,distortion of voltage,etc.The results show that compared with 7-rotor-pole VFRM,the influence of the high-order harmonics in flux-linkage on the torque-speed characteristics of 4-rotor-pole VFRM is greater due to large high-order harmonics in flux-linkage.Thirdly,6S/4R VFRM is selected as the research object.And the calculation method of torque-speed characteristics considering kth-order harmonics in flux-linkage proposed in this thesis is used to find the high-order harmonic of the flux linkage,which has the greatest influence on the torque-speed characteristics of the 6S/4R VFRM.The changing of the dominant high-order harmonic of phase voltage is also researched.It can be found that compared with other high-order harmonics in flux-linkage,the influence of the second-order harmonic in flux-linkage is the most significant.Finally,the results of FEA is verified by the fabrication and experiments of prototype.Finally,the torque-speed characteristics of 6S/4R VFRM and 6S/4R HEVFRM are analyzed and compared based on the calculation method of torque-speed characteristics considering kth-order harmonics in flux-linkage proposed in this thesis.The results show that compared with 6S/4R VFRM,there are larger high-order harmonics in flux-linkage and lower dc-link voltage utilization in 6S/4R HEVFRM.The influence of high-order harmonics in flux-linkage on torque-speed characteristics of 6S/4R HEVFRM is more significant.However,the dominant role of the second-order harmonic in flux-linkage decreases in 6S/4R HEVFRM. |
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