Research On Fault Tolerant Control Of Six-Phase Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)stands out in military and industrial fields because of its advantages of high efficiency,energy saving and convenient maintenance.At first,domestic and foreign scholars mainly used three-phase PMSM as the research object,but the three-phase motor could not meet many occasions requiring high precision and high reliability.The multi-phase permanent magnet synchronous motor is redundant due to the number of phases.When the motor fails,it does not have to stop running,merely adjust its control mode and enter the fault-tolerant compensation control algorithm to resume the operation of the system.Therefore,the research on fault-tolerant control of multi-phase PMSM has begun to deepen.In this thesis,six-phase PMSM is taken as the research object.The main research contents are as following:Firstly,the structural characteristics and working principle of the six-phase PMSM stator winding are stated.The transformation matrix of six-phase stationary to two-phase rotating coordinate system is derived,and the nonlinear six-phase PMSM mathematical model is transformed into a decoupled six-phase PMSM mathematical model.The magnetic field orientation control is adopted in the d-q coordinate system,the current loop and the speed loop are adjusted by PI control,and the six-phase PMSM control system is built and verified by MATLAB/Simulink.Secondly,the magnetic potential of a six-phase PMSM with two-phase stator winding open faults are analyzed in this thesis(both orthogonal and non-orthogonal).The principle of equal magnetic potential of the stator windings before and after phase loss is used.The phase and amplitude of the current are adjusted,and after the fault is switched to the current hysteresis control for magnetic potential compensation.The simulation experiment of six-phase PMSM fault-tolerant compensation control is implemented in MATLAB/Simulink.Thirdly,in order to reduce the overshoot and improve the dynamic characteristics of the fault-tolerant control system,the sliding-mode variable-structure control is applied to the six-phase PMSM fault-tolerant control system in this thesis.Aiming at the slip mode chattering problem,a new approach law is introduced to design the sliding mode speed controller.The Lyapunov function is used to verify the stability of the closed-loop fault-tolerant control system.The mathematical model of the sliding mode speed controller is built in MATLAB\Simulink,and the simulation waveforms of the six-phase PMSM fault-tolerant system under the sliding mode speed is compared with the PI speed controller.Finally,a six-phase PMSM drive system based on TMS320F28335 is built,and the main modules such as power module,sampling module and PWM output module are introduced.