| The research topic in this thesis is one of the important parts of the project"Study on the safety state monitoring system and fault diagnosis and early warning system of underground power distribution and ventilation networks in coal mine"(2007BAK29B05), which is supported by National Science & Technology Pillar Program of China. The Switched Reluctance Motor (SRM) continues to attract a lot of research interests in academe and industry due to its simple structure, flexible control, excellent starting performance and phase-deficient operation characteristics. The SRM has been widely applied in the fields of industry, aviation,household electric appliance, etc. However, owing to its doubly salient pole structure and highly nonlinear electromagnetism characteristics, the torque ripple of SRM is much serous than that of the conventional motors. When the SRM operates under the condition of two-phase excitation mode, the magnetic field coupling between the phases will occur. The mathematic model becomes much complicated and the high performance control is difficult to be achieved. In other words, the SRMs couldn't be applied in the servo driving system which request stationary torque at lower speed. As a result, it is of important theoretical value and practical significance to conduct the research on the mutual inductance under the condition of two-phase excitation, the accurate mathematic modeling considering mutual inductance and control strategy to minimize the torque ripple.In this thesis, the distribution features of magnetic field in single-phase excitation mode and in two-phase excitation mode are presented respectively, and the magnetic asymmetry in even phase SRM is analyzed. The total flux-linkage characteristics under the condition of single phase excitation mode and two-phase excitation mode are calculated by Finite Element Analysis (FEA) separately, and the difference between them is demonstrated by mutual inductance. The mutual inductance calculation model is put forward. The variety of mutual inductance with rotor position and phase current is calculated. The calculation method of co-energy is established considering the mutual inductance in two-phase excitation mode, and the mutual coupling effect on static torque-angle characteristic is theoretically analyzed. The time-stepping FEA analysis is carried out combining with the actual power converter. It has been shown by the research result that the mutual inductance is negative with larger current; the total torque in two-phase excitation mode is less than the sum of torques of the two phases in single-phase excitation mode; the instantaneous torque waveform is irregular.The variety of mutual inductance with different geometric parameters is discussed and it has been found that the mutual inductance can be reduced by increasing the proportion of the width of stator yoke and tooth appropriately or by decreasing the length of rotor pole arc. In view of the irregularity of torque waveform induced by mutual coupling, several compensatory measures are investigated to reduce the mutual coupling effect on torque. It is proposed that increasing the winding turns or chopped current properly could improve the regularity of torque waveform. The formula for calculating the winding turns and chopped current are also presented in this thesis.The static characteristics of the SRM prototype in single-phase excitation mode are measured by experiments. The method to measure the mutual inductance between two adjacent phases excited simultaneously is proposed, which is based on the practical running situation of SRM. The variation of mutual inductance with respect to rotor position and phase current has been measured and it has been found that the measured results are consistent with that calculated by FEA.The potential balance equation and torque balance equation considering mutual inductance are derived. The electromagnetic models of SRM are trained by Least Squares Support Vector Machine (LS-SVM). It has been shown by training results that this method is of rapid training speed and the trained models are highly accurate. The simulation model of Switched Reluctance Drive (SRD) system, which considers mutual inductance, is established based on LS-SVM. The SRD system is simulated and experimented. It has been verified by experimental results that the modeling method by LS-SVM considering mutual inductance is correct and effective.A torque ripple minimization control strategy based on torque compensation is proposed, which can compensate the torque caused by mutual inductance of asymmetric phases. The selection and calculation method of turn-on and turn-off angles, as well as the estimation method of the maximum speed at rated load are set up. In consideration with the torque inverse model, the simulation model of low torque ripple switched reluctance motor drive system, which can compensate the mutual inductance torque, is established and simulated. Simulation results show that the torque ripple is effectively reduced, and the degree of torque ripple with mutual torque compensation is lower than the one without mutual torque compensation.The controller of switched reluctance drive system based on TMS320LF2407 is developed and a redundant split-phase power converter is designed. A series of experiments, such as steady-state running at high and at low speed, dynamic running, starting operation, allowed output torque and so on, have been carried out. It has been shown by the experiments that the developed SRD system is of low static error, strong robustness and strong anti-interference ability. |
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