Research On Control Technology Of Six-phase Permanent Magnet Synchronous Wind Turbine

Compared with the traditional three-phase motor,the six-phase permanent magnet synchronous motor has more phases,can realize low-voltage and high-power AC transmission,has the advantages of small torque ripple,high reliability,rich control resources,and high flexibility.It has great application prospects in highpower,high-reliability applications such as wind turbines.Based on a six-phase permanent magnet synchronous motor,this paper studies the constant switching frequency hysteresis control method of the inverter,and the constant frequency hysteresis current fault-tolerant control.The main contents include:Two coordinate transformation methods of six-phase permanent magnet synchronous motors are introduced,and the mathematical model and vector control strategy of the motor are established.Analyze the mathematical model of the six-phase permanent magnet synchronous motor under normal conditions and after the phase failure,explain the decoupling process of the six-phase permanent magnet synchronous motor from the two directions of double d-q coordinate transformation and vector space decoupling,and give the motor the voltage,flux linkage and torque equations under synchronous rotating coordinate system,described the vector control method of a six-phase permanent magnet synchronous motor.Aiming at the shortcomings of the traditional current hysteresis control that the switching frequency is not fixed,a current hysteresis control scheme for the fixed switching frequency of a six-phase permanent magnet synchronous motor is proposed.Based on four different current positions,the principle formula of the fixed frequency hysteresis control is derived in detail,and the control strategy of fixed frequency hysteresis control scheme is designed,Based on simulation and experiment,the two hysteresis control methods are compared and analyzed in torque ripple,current ripple,THD value.,The effectiveness of the fixed-frequency hysteresis control is verified,and the THD value of the motor phase current can be reduced.The constant frequency hysteresis current control method is used to realize the fault tolerance control of the six-phase permanent magnet synchronous motor.According to the optimal current method,the current constraint conditions and optimization schemes was designed when the motor under normal conditions and after the W phase is broken,the corresponding current command value was calculated,the experimental scheme and control block diagram was designed,and built a simulation model through Matlab/Simulink for analysis After the motor phase is broken,the operating effects of the fault-tolerant algorithm before and after the embedding explain the feasibility of the fault-tolerant scheme,and the fault-tolerant experiment of the sixphase permanent magnet synchronous motor is completed,which verified that the six-phase permanent magnet synchronous motor can continue to operate without disturbance after the phase was broken.It shown the feasibility and scientificity of the fixed-frequency hysteresis current fault-tolerant control algorithm.The work of the paper proves that on the basis of establishing an accurate mathematical model of sixphase permanent magnet synchronous motor,the operation of the motor can be effectively controlled in real time through fixed-frequency hysteresis control.Under the condition of open phase,the disturbance-free operation of the six-phase permanent magnet synchronous motor is realized.