Research On Fault-Tolerant Control Strategy And Speed Ripple Suppression Methods Of Five-Phase Permanent Magnet Synchronous Motor

Stator winding fault is one of the common faults of permanent magnet synchronous motor(PMSM).In order to reduce the adverse impact of stator winding fault on motor operation,a five-phase fault-tolerant PMSM with no electromagnetic coupling and low thermal coupling between phase windings is taken as the research object in this thesis.The thesis focuses on the structure of fault-tolerant PMSM,control system and fault tolerant control strategy,and mainly studies the speed ripple suppression methods of five-phase fault-tolerant PMSM under coil inter-turn short circuit(ITSC)fault condition.Firstly,the structure of five-phase fault-tolerant PMSM with no electromagnetic coupling and low thermal coupling between phase windings is introduced and analyzed.The fractional slot concentrated winding is adopted in this motor.Two windings belonging to a same phase winding branch are wound in the opposite direction and there are small teeth on stator core between different phase windings.As a result,there is no electromagnetic coupling between different phase windings.The influence of the small teeth on winding coefficient of the motor is analyzed,and the calculation formulas of stator phase winding inductance under normal condition and coil ITSC fault condition are deduced in this thesis.The loss and operating efficiency of the motor are also analyzed.Secondly,the mathematical models of five-phase fault-tolerant PMSM under normal condition and single-phase open circuit fault condition are established in this thesis.The coordinate transformation matrix under single-phase open circuit fault condition is deduced.The basic voltage space vector and its action time of Space vector pulse width modulation under two conditions are calculated respectively.The switching sequence of the basic voltage space vector is determined.Based on this,the field-oriented control system under normal condition and the fault-tolerant control system under single-phase open circuit fault condition are designed.Finally,the generation mechanism of fault torque ripple and speed ripple under coil ITSC fault is analyzed in this thesis.Aiming at the problem that PI speed controller can not suppress the speed ripple caused by ITSC fault,a speed ripple suppression method of five-phase fault-tolerant PMSM based on quasi-proportional complex integral controller and a speed ripple suppression method based on speed ripple compensator are proposed.And the stability of these two systems is analyzed.The effectiveness of the proposed speed ripple suppression methods is verified by simulation and experiment.