Research On Permanent Magnet Assisted Bearingless Synchronous Reluctance Motor And Its Speed Sensorless Control

Low torque density,high torque ripple,high suspension force ripple and low power factor are persistent diseases that restrict the development and wide application of traditional bearingless synchronous reluctance motors(BSynRMs).Aiming to solve the above problems,two permanent magnet assisted bearingless synchronous reluctance motors(PMa-BSynRMs)with different rotor structures are designed and contrasted.By inheriting the merits of the magnetic bearings,synchronous reluctance motors and permanent magnet motors with high saliency ratio,the extra advantages of PMa-BSynRMs are more appropriate for high speed and high precision applications,such as fast dynamic response,low torque ripple,low losses and so on.The operation mechanism and mathematical model of the PMa-BSynRM are analysed.Moreover,the finite element analysis and comparison of two different rotor structures and speed sensorless control are also researched and probed in this dissertation.1.The development process of bearingless motors and BSynRMs is elaborated.And then,the domestic and foreign research status and future development are detailedly described.The operation mechanism and mathematical model,including torque and suspension force subsystem,of the PMa-BSynRM are analysed.2.Aiming at reducing torque and suspension force ripple,increasing torque density and power factor,different permanent magnet adding position and magnetizing mode in magnetic barrier rotor are optimized and designed by ANSYS/Maxwell.The performance indexes,like torque,suspension force and power factor,of a traditional BSynRM and two PMa-BSynRMs with different rotor structures are analyzed in detail.3.To make the PMa-BSynRM break through the constraint of mechanical sensor from the point of view of speed sensorless control,a composite estimation method for the rotor position and speed is proposed.The position and speed of rotor are estimated by pulse vibration high frequency signal injection at zero speed and low speed.And then,a new Kalman filter algorithm is used to estimate the rotor position and speed when the motor is running at medium speed and high speed.The rotor position and speed can be estimated in full speed due to the smooth switching achieved.By the simulation model of speed sensorless control system built in MATLAB/SIMULINK,the reliability of system is verified.4.Based on the PMa-BSynRM operating mechanism and the proposed control strategy of the speed sensorless,the hardware and software of the prototype digital control system are designed and built.The performance and control system of the prototype are verified by the ex-perimental platform.