Research On Drive And Fault-tolerant Control Of Six-phase Permanent Magnet Synchronous Motor

Multi-phase permanent magnet synchronous motor has not only the characteristics of high power factor of PMSM,but also the advantages of low torque ripple and high reliability of multi-phase motor.It is widely used in AC transmission fields such as low voltage,high power and high reliability.In this paper,the double Y-shift 30 six-phase PMSM is taken as the research object,and its mathematical model,SVPWM modulation,fault-tolerant control after two-phase open circuit,model predictive fault-tolerant control and so on are deeply studied.Firstly,two structures of stator winding of six-phase PMSM are studied,and the principle of eliminating low harmonic magnetic motive force by double Y-shift 30 motor is given.The relationship between double modeling method and vector space decoupling modeling method of commonly used six-phase PMSM is analyzed in detail,and the mathematical model built by two modeling methods is given,and the MATLAB simulation model is built.Secondly,the principle and method of traditional two-vector SVPWM algorithm and four-vector SVPWM algorithm based on VSD coordinate transformation are introduced.Two-vector SVPWM and four-vector SVPWM have the characteristics of high voltage modulation index and effective suppression of harmonic current,respectively.In order to reduce the current amplitude in the harmonic plane to zero,a four-vector SVPWM algorithm based on intermediate voltage vector is proposed.The simulation results show that the algorithm can further reduce harmonic current while realizing stable operation of the motor.Thirdly,the vector control of six-phase PMSM after one-phase opencircuit is analyzed and the two-phase open circuit is studied.According to the principle the stator magnetic motive force is constant,the current of the six-phase PMSM with two-phase windings missing under different neutral point connection forms is solved with the minimum copper consumption and the minimum phase current of the stator as the targets respectively.According to different neutral point connection forms,the transformation matrix after missing phase is obtained,establishing a mathematical model of six-phase PMSM without two phases,and thus proposing a decoupling vector control method.The simulation verifies the correctness of the fault-tolerant control algorithm,which effectively reduces the torque ripple after phase failure and improves the reliability of the drive system.Finally,a fault-tolerant control based on model predictive current control(MPC)is proposed to solve the problem that the ??-subspace voltage vector distribution is irregular and the traditional vector control and SVPWM method cannot be realized when one phase winding is open.The predictive current control of different models are compared,including single,double and three vector MPC.The mathematical model of six-phase PMSM after phase loss is built in MATLAB,and the fault-tolerant control is realized by three control strategies with the same sampling frequency.Simulation results verify the effectiveness of the proposed fault-tolerant control algorithm and compare the advantages and disadvantages of the three control strategies,among which the three-vector MPC is more complex but has the best control performance.