Research On Direct Torque Control Of Permanent Magnet Synchronous Motor Based On Super-twist Algorithm

Permanent magnet synchronous motor(PMSM)has the advantages of simple structure,small volume,low loss,high operating efficiency,and the domestic rare earth resources are abundant,so PMSM application are becoming more widespread.Direct torque control(DTC)has become a research hotspot in recent years due to its fast response speed and no need for complex coordinate transformation.However,the direct torque control has the problem of large flux linkage and torque ripple and inaccurate flux identification.In this paper,the research on these issues will be improved and the following tasks will be completed:Firstly,taking the surface-mount permanent magnet synchronous motor as the research object,this paper expounds the research status and development trend of the direct torque control of permanent magnet synchronous motor,then derives the mathematical model of permanent magnet synchronous motor in common coordinate system,and introduces the basic principle and implementation process of the traditional direct torque control.In consideration of the defects of large torque and flux ripple,the mechanism and mode of action of zero vector in DTC are explored,then the simulation model of PMSM-DTC with zero vector is constructed and compared with traditional DTC.The simulation results show that PMSM-DTC with zero vector can promote the reduction of flux linkage and torque ripple.Since the PMSM-DTC with zero vector has not changed the structure of traditional direct torque control,a high performance control system cannot be formed and the flux linkage and torque ripple are still large.According to the basic theory of second-order sliding mode and space voltage vector pulse width modulation,the PMSM-DTC based on super-twist algorithm is constructed.Meanwhile sign(s)function in super-twist algorithm is replaced by sigmoid(s)function in quasi-sliding mode to increase system robustness.The simulation results show that the PMSM-DTC based on the super-twist algorithm can effectively reduce the flux linkage and torque ripple,thus obtaining good control effect.In order to further enhance the system performance,this paper has improved and studied the specific problems existing in the traditional flux observer.The model reference adaptive system is used first to identify the stator resistance,then the realtime identified stator resistance is sent to the adaptive quadrature compensation flux observer without PI adjustment module to eliminate the effects of DC bias and stator resistance changes on the system.Combined with the super-twist algorithm,a new simulation model is construct.The results show that the new flux observer can not only improve the stator flux identification accurately,effectively reduce the flux linkage and torque ripple,but also improve the current waveform and further enhance the system stability.Finally,this paper designs hardware and software of the direct torque control system based on the digital signal processor,then introduces the hardware circuit diagram and software flow chart of the key links in the system and constructs a direct torque control experimental platform for PMSM.