Disturbance-Observer-Based Fault-Tolerant DTC Of Five-phase Permanent Magnet Motor

With the intensification of the greenhouse effect and the energy crisis,electric-driven vehicles are favored by countries and car manufacturers around the world because of their zero emission and low energy consumption.As the core power component of electric vehicles,the performance and reliability of electric motors are very important.Compared with other types of motors,Permanent-Magnet Synchronous Motor(PMSM)has the advantages of high efficiency,high power density,and compact structure.Therefore,it has been widely used in electric vehicles.However,when one-phase open-circuit or short-circuit fault occurs in the PMSM,large torque ripple will be generated if relevant measures are not taken,which will seriously affect the running performance of the vehicle.In this paper,five-phase PMSM is used as the control object,disturbance-observer-based fault-tolerant DTC of PMSM is carried out to realize the stable and undisturbed operation under one-phase open-circuit fault or short-circuit fault.The main research contents are four parts:(1)The mathematical model of five-phase PMSM is established in the natural frame and the two-phase stationary frame.According to the characteristics of the five-phase PMSM,DTC strategy based on switching table with suppresion of the third harmonic is designed.(2)When one-phase open-circuit or short-circuit fault occurs in the PMSM,the currents of the healthy phases are solved according to the constraints of equal magnetomotive force before and after the fault,minimum copper loss,and zero sum of the healthy phase currents.And the reduced-order Clark transformation matrix is deduced.Then,the mathematical model of PMSM in the two-phase stationary frame and the space voltage vector is reconstructed.Fault-tolerant switching table which meets the control requirements of flux linkage and torque is designed with closed-loop control based on the idea of zero third harmonic current.Then,mathematical model of PMSM is constructed in the MT coordinate frame,and disturbance observer is designed to observe external disturbances caused by phase short-circuit currents and unmodeled part.Finally,the fault-tolerant DTC strategy based on disturbance observer is proposed,and its feasibility is verified by simulation.(3)When two-phase open-circuit fault or short-circuit fault occurs,the remaining healthy currents are derived according to the constraints of equal magnetomotive force before and after the fault,and the zero sum of remaining healthy currents.Then the reduced-order transformation matrix is obtained by the fault-tolerant currents.On the basis of reduced order transformation matrix,the mathematical model and voltage vector of the PMSM are established in the two-phase stationary frame,and the optimal voltage vector is selected according to the control requirements of the flux linkage and torque.Hence,the fault-tolerant switching table under two-phase fault is made.At the same time,the disturbance observer obtained before is added to observe the external disturbance.The anti-interference of the system is enhanced by it.Finally,fault-tolerant DTC control under two-phase faults are realized,and fault-tolerant performance is tested through simulation.(4)The five-phase PMSM experiment platform is built,and the motor controller based on the DSP TMS320F2812 and power module PM100CVA120 is designed.The proposed disturbance-observer-based DTC strategy under one-phase open-circuit fault and one-phase short-circuit fault is verified through the experiment.Compared to performance under normal conditions,the experimental results show that the proposed fault-tolerant DTC strategy can not only effectively inhibit torque ripple caused by open-circuit faults and short-circuit faults,but also improve steady state and dynamic performance of PMSM.