Research On Sensorless Direct Torque Control System Of Permanent Magnet Flux-switching Motors

Permanent magnet flux-switching motors(PMFSM),whose Permanent Magnet is located on the stator,has the advantages of simple rotor structure,small torque fluctuation,high power density,and high sinusoidal inverse potential,which is suitable for AC speed regulation system.It has attracted much attention in the field of new energy and aerospace.Since PMFSM is a controllable speed regulating motor newly emerged in recent years and the development time is short,this thesis only focuses on PMFSM rotor position detection and control strategy.In this thesis,starting from the structure of PMFSM,the operation principle of the motor is described,the mathematical model of the motor is established,and through the analysis of the electromagnetic performance of the motor,it is found that it is suitable for AC control system,and its control mode is given.Based on the analysis of the traditional direct torque control strategy,a SVM-DTC control method based on sliding mode control is proposed to improve the control performance of the system and reduce the torque ripple.The sliding mode controller replaced the torque hysteresis and flux hysteresis,and combined with SVPWM to improve the control accuracy.The simulation model is built by Matlab/Simulink platform for simulation research.Under different operating conditions,the comparison with the traditional direct torque control method is carried out.The results show that the direct torque system under sliding mode control has smaller torque pulsation and improves the dynamic performance of the system.Secondly,in view of the existence of the position sensor can increase system complexity and influence the reliability of the system as a whole,in direct torque control system on the basis of study the non-inductive control method,analyzes the low speed under high frequency pulse vibration sine injection method and speed based on the extended position estimation method of back emf model,and the overlap of switching methods.In order to realize the position estimation of the motor rotor with the same model at different speeds,a position estimation method based on the quadratic extended back potential model is proposed.By further expanding the q-axis current in the classical extended back potential model into fundamental frequency quantity and high frequency quantity,the position estimation at low speed and medium high speed is unified.Compared with the high frequency pulse sinusoidal injection method,the position estimation effect is significantly improved compared with the weighted transition method because the low speed and high frequency injection method does not have the influence of phase lag caused by filter.The feasibility of the proposed position-free detection method is verified by simulation analysis.Finally,using TMS320F28335 as the system master chip,the PMFSM whole speed control system experiment platform is built,including the design of each circuit of hardware part and the corresponding software program.Experimental research is carried out on the designed experimental platform,and the experimental waveform of the motor under different working conditions is tested and compared with the simulation,which proves the effectiveness of the system designed in this thesis.