Design And Fault-tolerant Control Of Five-phase Permanent Magnet Synchronous Motor Without Electromagnetic Coupling Between Phase Windings

Five-phase permanent magnet synchronous motor(PMSM)has the redundancy of the phase number which can operate under the fault-tolerant conditions to improve the reliability of the motor.And it has the advantages of smooth operation and flexible control mode,so it is widely used in aerospace,ship propulsion and other fields with higher reliability requirements.In this paper,five-phase PMSM is taken as the research object.The selection of the combination of its poles and its slots,the design of electromagnetic structure,the application of the nearest two vectors(NTV)and the injection of the third harmonic current control strategy,the establishment of the mathematical model after the phase loss of the five-phase PMSM and the implementation of the fault-tolerant control strategy have been studied in detail.First of all,a five-phase PMSM without electromagnetic coupling between phase windings is designed.By analyzing the magnetomotive force(MMF)of the five-phase PMSM,the rule of harmonic pole-pairs of five-phase motor in the synthetic MMF is deduced and summarized and the combination of its poles and its slots are selected accordingly.The design of adding small teeth on the stator of the motor is proposed to eliminate the electromagnetic coupling between different phases,and the structure of the motor is optimized by electromagnetic simulation.Next,through establishing the corresponding mathematical model of the five-phase PMSM in the rotating coordinate system,the NTV control method and the control method of the injected third harmonic current in the five-phase PMSM system are obtained and they are discussed in detail.Besides,the contribution of the latter method to the improvement of torque density of motor is analyzed quantitatively.Finally,a fault-tolerant control strategy for five-phase PMSM under single-phase open-circuit fault is newly proposed.The mathematical model of the five-phase PMSM without electromagnetic coupling under single-phase open-circuit fault is deduced.This strategy adopts two methods which are based on the principles of minimum copper loss and equal amplitudes of currents to control the remaining four-phase currents.The distribution of voltage vectors of five-phase inverter system in ?-?-y plane under single-phase open-circuit fault can be obtained.The sectors are redefined,and the selection rules and the synthesis rules of the optimal voltage vectors are set in the reconstructed fundamental ?-? plane and the harmonic y-axis.Space vector pulse width modulation(SVPWM)is applied to fault-tolerant control of five-phase PMSM for the first time.In addition,feed-forward compensation is applied to the generation of the d-axis and q-axis reference voltage to reduce the nonlinear interference of the system.Simulation results validate the effectiveness of the proposed strategy.