The Research Of Direct Instantaneous Torque Control For Bearingless Switched Reluctance Motor

Switched Reluctance Motor(SRM)is a kind of double salient pole synchronous motor,with the advantages of simple structure,large starting torque and high stability.It has obtained the development and application prospect in some fields such as oil,aviation and electric cars.Bearingless Switch Reluctance Motor(BSRM)has the same structure as ordinary SRM.The introduction of bearingless technology can solve the problems caused by mechanical friction,and can broaden the application area to the high speed adaptability of BSRM.There is a strong coupling between torque and suspension force,which is one of the most important factors that restrict its operation performance and application range.In this paper,the control strategies of double-winding and single-winding BSRMs are studied.The control strategies are adopted to improve the control performance and fault tolerance of BSRM.Firstly,the Direct Instantaneous Torque Control and Direct Force Control(DITC&DFC)strategy of 12/8 double-winding BSRM is studied.The basic principle and working method are introduced mainly.The decoupling of the torque and radial force of BSRM is realized by making torque and radial force as variables to be contoroled directly.Its control is simple which is independent on precise mathematical model.It is verified by simulations and experiments that torque ripple and suspension fluctuation can be effectively restrained though DITC&DFC,and it can also provide a good dynamic performance.Secondly,due to the single-winding BSRM has a simpler structure,and is more practical and versatile,the following are mainly studied in the single-winding BSRM control strategy.In view of 12/8 single-winding BSRM,the advantages and disadvantages of the traditional current control strategy,Direct Torque Control and Direct Force Control(DTC&DFC)strategy and DITC&DFC are analyzed.Experiments illustrate that the method of direct control can provide a better performance.Meanwhile,torque ripple is smaller in DITC&DFC in contrast to DTC&DFC.Finally,in order to improve the reliability of BSRM,the fault-tolerant operation under different control methods are studied for the 12/8 single-winding BSRM.The fault-tolerant current mathematical model of the 12/8 single-winding BSRM is optimized based on the traditional current control strategy.It is verified by simulations and exper iments that the improved mathematical model can increase the torque in fault-tolerant operation.In order to further improve its ability of fault tolerance,the fault-tolerance control is studied based on DITC&DFC control strategy.The winding fault-tolerant operations of short-circuit and open-circuit fault are realized by establishing compensation principle and reconstructing voltage symbol selection table.Exper iments verify that the fault-tolerant control strategy can effectively restrain torque ripple and suspension force fluctuation,and can provide a good dynamic performance.