Simulation Studies For Switched Reluctance Motor System Based On Finite Element Nonlinear Model And Torque Ripple Reduction

The stepped electromagnetic filed of Switched Reluctance Motor (SRM) is always working at saturation and nonlinear state. Due to the many control parameters and the phase current wave shape varies with the rotor position and control styles, so there is no simple and unified mathematic model and parsed equation can be obtained. Because of the nonlinear material and saturation of magnetic field of SRM, it is difficult to do accurate analysis and calculation by using conventional magnetic circuit method. Besides, SRM can not run by itself without driving circuit, it is needed to consider the influence of outside driving circuit and control parameter when calculating the electromagnetic filed. The non-sine phase current and the high saturation of magnetic flux density decide the machine as a time-varying and nonlinear system. There will be much error to describing the static and dynamitic characteristic by using linear model. For studying the static and dynamitic characteristic of SRM more deeply and accurately, it must be analyzed and designed wholly for the machine and its driving circuit based on nonlinear model. Further more, torque ripple is one of major problems for SRM which can cause undesirable acoustic noise and vibration. So, how to minimize and reduce the torque ripple is being the hotspot and difficult point in the SRM studies.In this paper, the whole analysis and simulation experiment are done aimed at the above problems of SRM based on finite element nonlinear model. In the end of this paper, in terms of the basic reason which caused undesirable torque ripple, the method of improving the structure of stator magnetic poles is advanced to reduce the torque ripple. Firstly, the finite element software ANSYS is used to calculate and analyze the nonlinear 2D electromagnetic filed of SRM. In the same time, the MATLAB/SIMULIN-K software is employed to build the dynamic system simulation model where the finite element electromagnetic data are transferred, which can consider the influence of material nonlinear, electromagnetic saturation and outside driving circuit and control parameter. Secondly, the dynamic simulation of SRM system is done to validate the validity of model under Chopped Current wave Control (CCC) and Angle Position Control (APC) strategy at low and high speed respectively. Finally, the basic reason of torque ripple is obtained and a method with improving the stator pole structure is advan- ced. That is the improved stator pole can reduce the varying degree of air magnetic field, which can minimize the torque ripple effectively and increase the average output torque.