Research On Direct Torque Control For Six-phase PMSM Series-connected Three-phase PMSM With One Inverter

The rapid developments of aerospace technology the ship's power-driven,electric locomotive traction,electric/hybrid fuel vehicles and other key areas,it has rigorous limits with volume and weight of drive system,lightweight,high power density,low cost,and greater fault tolerance will be an important development direction.Some researches on direct torque control strategy for six-phase PMSM series-connected three-phase PMSM with one inverter,fault-tolerant direct torque for six-phase PMSM with open-phase series-connected three-phase PMSM with one inverter and direct torque control strategy for six-phase PMSM with four open-phase fault.Concrete contents are as follows.The' decoupled transform matrix for six-phase PMSM series-connected three-phase PMSM is established in this thesis.The connection law of six-phase PMSM series-connected three-phase PMSM is analyzed,and it proves that the two motors can be decoupled by this connection.The mathematical model of series system is established in three coordinate,a direct torque control(DTC)strategy is proposed for six-phase symmetrical winding salient pole permanent magnet synchronous motor series-connected three-phase salient pole permanent magnet synchronous motor(PMSM)in this thesis.By using the orthogonal transformation matrix,the electromechanical energy conversion variables of the two motors are projected into the space of two orthogonal planes,and the non electromechanical energy conversion variables are projected into the zero sequence space,to achieve the two motor flux and torque decoupling.A new voltage vector is generated by combining the single voltage vector and the partial combined voltage vector,Torque,stator flux linkage and zero-sequence current of two motors are controlled at the same time by the output voltage vector through the 6 phase inverters.The simulation and experimental results show that the proposed control strategy makes each motor stator flux linkage and electromagnetic torque decouple each other.Based on the mathematical model of six-phase PMSM series-connected three-phase PMSM,study on the direct torque control strategy for series-connected system with six-phase motor one opened phase.A new voltage vector is generated by combining the single voltage vector and the partial combined voltage vector,Torque and stator flux linkage of two motors are controlled at the same time,it is proved that the two motors in the series can be decoupled by a single inverter by simulation and experiment.The mathematical model of four phases of symmetrical six-phase salient pole permanent magnet synchronous motor is studied;in order to build circular flux trajectory of four-phase of DTC strategy,based on the definition of dummy variable,virtual stator flux and torque of mathematical model was rebuilded.Select the correct voltage vector to control the virtual stator flux and torque.Simulation and experimental results show that the proposed control strategy is able to make the motor run smoothly and the dynamic response rapidly.