Method to Modify the Performance of Direct Torque Control for Asynchronous Motor

A modified strategy was proposed,which bases on the problem of large torque ripples,stator flux depression and distortion of stator current and so on in the application of DTC of asynchronous motor at low speed.An improved integration algorithm with amplitude compensate in place of the integration to overcome the problem of the integrator drift dues to DC offset in the compute stator flux using the U-I model.To deal with the defect of traditional six section control of voltage select table and the performance decline when stator flux is near the section line and not all use voltage vector in each sector,the twelve section control method of voltage select table and the implementation was presented.The use of improved integration algorithm and twelve-section voltage vector select tables are comprised an improved method.The simulation results prove this method can markedly improve the stator flux linkage and torque ripples and improve the control performance of the system.