Research On Fault-tolerant Control For Multi-phase Permanent Magnet Motor

Multi-phase permanent magnet motor has been widely used in electric vehicles,aerospace,industrial manufacturing and other key areas due to its advantages of high reliability,high power density and high efficiency.The reliability of the drive system is very important in these applications,and the fault-tolerant control of multi-phase motor based on redundant degrees of freedom is an important measure to improve the reliability of multi-phase motor drive system.In this paper,the predictive direct torque control(DTC)strategy for six-phase and three-phase permanent magnet synchronous motor(PMSM)series-connected system with full phase or with one open-phase fault for six-phase PMSM and the fault-tolerant control strategy for six-phase dual-winding bearingless flux-switching permanent magnet motor(BFSPMM)were studied in detail.Multi-motor series-connected drive system has good application prospect in textile manufacturing,electric vehicles,industrial robots and other industrial applications due to its advantages of reducing the volume and cost of driver system and easy realization of regenerative braking.In this paper,the mathematical models of the six-phase and three-phase PMSM series-connected system in natural,stationary and rotating coordinate system were deduced.The prediction models of the two-PMSM series-connected system were deduced from the mathematical models,and the predictive DTC strategy of the two-PMSM series-connected system was constructed based on the prediction model in rotating coordinate system.In order to suppress the zero-sequence current caused by the dead time of switch tube,the turn-on voltage of switch tube and other nonlinear factors,the zero-sequence current suppression strategy was added into the control strategy.The simulation and experimental results show that the proposed predictive DTC strategy can achieve the independent decoupling control of two PMSMs,and the torque ripples of two PMSMs are obviously smaller than which of traditional DTC.In order to improve the reliability of the two-PMSM series-connected system,the voltage expression of the two-PMSM series-connected system with one open phase in six-phase PMSM was deduced,and the voltage of the open phase was included in the voltage expression.The prediction model for the two-PMSM series-connected system with fault was derived based on the voltage expression.According to the prediction model,a fault-tolerant predictive DTC strategy was proposed.The simulation and experimental results show that the proposed control strategy can achieve the stable torque output and the decoupling control of two PMSMs under one open-phase fault for six-phase PMSM.Flux-switching permanent magnet motor(FSPMM)is a kind of stator permanent magnet motor.For there are neither permanent magnet nor winding in its rotor,it is especially suitable for high-speed operation.For the traditional mechanical bearing is instead by bearingless technology,the bearingless FSPMM is more suitable for high-speed applications.In this paper,the mathematical models of tangential rotation and radial suspension of the six-phase dual-winding BFSPMM were deduced based on the simulation results of Ansoft.On this basis,the simulation model of the motor was established in Matlab,and a BFSPM control strategy was proposed.In this strategy,the given power current was got by vector control,and the given suspension current was got based on the minimum copper loss principle.The given current was transformed into natural coordinate system,and the phase current was controlled according to the given current by the hysteresis current comparator.Based on the same principle,the fault-tolerant control strategy for BFSPMM with open-phase fault in power winding or suspension winding was proposed based on the constraint that the current of open phase is zero.The simulation results show that the proposed control strategy for BFSPMM with or without open-phase fault can achieve accurate control of torque and suspension force.