Research On Direct Torque Control For Five-Phase Salient-Pole Permanent Magnet Synchronous Motor

In high power and high reliability applications,such as aerospace propulsion systems,ship's power-drive,electric locomotive traction,electric/hybrid fuel vehicles and other key areas,it has rigorous limits with volume and weight of drive system.Therefore,a multi-phase motor drive system with high reliability,high power density,high efficiency,small torque ripple,fault-tolerant operation and low voltage and high power will be an important development direction.Some researches on direct torque control(DTC)strategy for five-phase salient-pole permanent magnet synchronous motor(PMSM),DTC strategy for five-phase salient-pole PMSM with 3rd harmonic injection and fault-tolerant DTC for five-phase salient-pole PMSM with one open-phase fault.Concrete contents are as follows.According to the stator model Y112M-2 three-phase induction motor,by changing the stator winding and rotor electromagnetic structure,and then using Ansoft/Maxwell finite element analysis software to design a power of 1.5kW,the back-EMF is a five-phase trapezoidal wave Salient-pole permanent magnet synchronous motor In addition,a set of experiment platform with TMS320F2812 DSP as its core and a corresponding software system are introduced in order to carry out experimental research on the control strategy proposed later.In the case of considering harmonics,the distribution of motor inductance is deduced.The mathematical model of three-phase salient pole PMSM with the third harmonic winding in the three coordinate systems is further constructed.A five-phase PMSM DTC scheme based on maximum torque per ampere(MTPA)is proposed.Under the condition of no harmonic injection,the given fundamental flux changes dynamically with the load,so that the output electromagnetic torque reaches the maximum when the stator copper loss is constant.Two DTC schemes for five-phase PMSM are proposed on the basis of the 3rd harmonic injection and the reluctance torque of the motor.The same between the two DTC schemes is using five-phase inverter to output single voltage vector or discrete synthesis of voltage vectors in one control period to realize the direct control of torque and flux on the fundamental and 3rd harmonic planes simultaneously,and then realize the 3rd harmonic injection to enhance the load capacity.The difference between the two DTC schemes is that the scheme I takes the minimum copper loss as the constraint condition to construct the MTPA-DTC strategy;However,the scheme 2 takes the minimum copper loss and the same phase relation between fundamental and 3rd harmonic currents as the constraint condition to construct the MTPA-DTC strategy.The two DTC schemes all take advantage of the motor torque to further enhance the load capacity.Simulation and experimental results show that not only the motor output torque is enhanced,but also the magnetic saturation of the stator core is reduced.Based on the mathematic model of five-phase permanent magnet synchronous motor without fault,a kind of fault-tolerant direct torque control scheme of five-phase PMSM based on torque reference feed-forward compensation is proposed.Simulation and experimental results show that the proposed control strategy can make the motor run smoothly and respond dynamically.In order to solve the problem of large torque ripple of ordinary DTC,a five-phase PMSM space vector modulation direct torque control(SVM-DTC)strategy based on double vector space is proposed.Under two conditions of non harmonic injection and 3rd harmonic injection,Simulation and experimental analysis of the proposed five phase SVM-DTC strategy verify that the proposed strategy can effectively control both the fundamental and 3rd harmonic plane flux and torque,and significantly reduce the torque ripple of the motor.