| The multi-phase permanent magnet synchronous motor has the advantage of high reliability,high power density,low torque ripple,and fast response speed when the variable frequency drive is performed.In order to reduce the harmonic content of the inverter output,and meet the power level requirements and system reliability requirements,a three-level drive scheme is adopted.In this paper,the double-Y shift30° six-phase permanent magnet synchronous motor is selected as the control object,and the advantages of both the six-phase permanent magnet synchronous motor and the three-level variable frequency drive are combined.The driving strategy of the three-level six-phase permanent magnet synchronous motor is studied and analyzed.Firstly,the double-Y shift 30° six-phase permanent magnet synchronous motor is taken as the research object,and its mathematical model is established.The transformation matrix in the six-phase permanent magnet synchronous motor is derived based on the six-phase stationary coordinate system,the double d-q coordinate system and the vector space decoupling method,which can realize the decoupling of the six-phase permanent magnet synchronous motor.Secondly,the topology of the Neutral-Point-Clamped type three-level six-phase inverter drive system is designed,and the basic principle of modulation strategy based on carrier cascade comparison and that of SVPWM modulation strategy based on dual three-level is analyzed respectively.The two modulation strategies are simulated by MATLAB/Simulink,and the simulation results are compared.It is concluded that the closed-loop control of the harmonic current can effectively reduce the stator harmonic current under the two modulation strategies.Thirdly,the magnetic potential relationships of the motor are analyzed,which runs in normal operation state and phase loss operation state,and the motor’s fault-tolerant control method after the Z-phase open circuit fault is studied.Twofault-tolerant optimization methods are studied,which are based on the minimum stator copper loss and the maximum output torque.Adjusting the currents of remaining phase,which can ensure the stable operation in the motor after the phase loss occurs.MATLAB/Simulink software is used to simulate the open circuit fault of Z phase during normal operation of the motor.At this moment,it is switched to fault-tolerant control,and its feasibility is verified by simulation.Finally,according to the overall structure of the three-level six-phase permanent magnet synchronous motor control system,the main circuit,drive circuit,detection circuit and communication circuit of the control system are designed,and the software of the control system is designed based on DSP and FPGA.The whole control system experiment platform is built,to verify the feasibility of the control system strategy. |
