Research On Fault Tolerant Control Strategies For Demagnetization Faults Of Permanent Magnet Synchronous Motor Based On Observer

As a core part for electromechanical energy conversion in modern transmission field,permanent magnet synchronous motors had occupied a pivotal position in industrial production area relying on their excellent performance.Recently,along with the rapid development of automatic field,higher and higher requirements had been put forward on the reliability of permanent magnet synchronous motor and the performance of the servo system.In comparison with an electric excitation motor,the largest problem was the risk of demagnetization of the permanent magnet material.As a consequence,the application range of permanent magnet synchronous motors was greatly limited.Furthermore,the current loop dynamic performance required in a high-performance servo system could not be realized by adopting the PID regulating method based on coordinate transformation.Therefore,the research conducted in this paper focused on fault-tolerant control of permanent magnet synchronous motors based on current control strategies,aiming improving the performance and reliability of the servo system.The content of research in the paper included:The fault-tolerant control method based on the active flux linkage concept is presented,which addresses permanent magnet demagnetization faults in PMSMs.First,the effect of permanent magnet demagnetization on the current control is analyzed.Second,the stator current in the static coordinate is set as the state variable,an observer is designed based on a sliding-mode variable structure,and an equation for active flux linkage is established for dynamic estimation based on the equivalent control principle of sliding-mode variable structure.Finally,the active flux linkage for the next moment is predicted according to the operating conditions of the motor and the observed values of the current active flux linkage.The deadbeat control strategy is applied to eliminate errors in the active flux linkage and realize the objective of fault-tolerant control.Timely and effective control on the damage or loss of permanent magnet was realized by adopting the method.In the rail transit traction systems,the permanent magnet demagnetization faults in the permanent magnet synchronous motor can lead to the problem of load capacity reduction.A fault-tolerant predictive control method based on the on-line detection of flux linkage is proposed.Firstly,the effect of current control and motor running state caused by demagnetization of permanent magnet will be analyzed in great detail with conforming to predictive control model of permanent magnet synchronous motor.Then,a real-time estimation equation for permanent magnet flux linkage is established based on the equivalent control principle of sliding mode variable structure,whereas the observer is designed based on sliding mode variable structure.Through the permanent magnet flux linkage formula,and then calculate the state current observation value.Finally,a fault-tolerant predictive control algorithm is constructed.The algorithm used state current observation value as feedback to input the fault-tolerant predictive controller.And it can eliminate the current error,which will achieve the purpose of fault-tolerant control.