Research On Torque Ripple Reduction Of Asynchronous Motor In Direct Torque Control System

Direct torque control is another high performance control technique of AC motor, it discard the decouple idea of vector control, but adapt flux oriented control and transient space vector theory, directly control stator flux and torque, it has the advantage of rapid torque response and less relying on stator parameters, but has the disadvantage of bigger torque ripple.Direct torque control system that uses TMS320LF2407A DSP as its core is designed. In this paper, on the basis on analyzing of asynchronous motor, DTC principle and torque ripple characteristic, the vector subdivision method is studied particularly, and at the same time, an improved optimized switch stable method is proposed.Finally, conventional control method, vectors subdivision method and optimized switch table method are researched by MATLAB simulation; the control circuits based on TMS320LF2407A are designed .Conventional control method, vectors subdivision method and optimized switch table method have been implemented on 1.1kW induction motor by assembly language. The simulation and experiment results prove that at the same sampling frequency and hysteresis width of stator flux and torque, comparing with conventional control method, the vectors subdivision method can better reduce the torque ripple , improve the motor performance at low speed; The optimized switch table method which proposed on the basis of vectors subdivision, has the same results comparing with vectors subdivision method , it reduce the torque ripple and complex degree of implementation.