Research on Torque Hysteresis Amplitude Adjustable Direct Torque Control Method

The direct torque control (DTC) technique has been widely used as a control strategy for motor drive system. High torque ripple is a major problem when the motor is running at low speed in DTC system. By analyzing the causes of torque ripple, it is can be found that the change of the speed error signal is a good indicator to determine the situation of motor torque ripple. In this paper, a DTC strategy with a fuzzy logic controller has been proposed. The inputs of the fuzzy controller are the speed error signal and the change rate of current signal. The output is incremental value of the torque hysteresis amplitude. Dynamic adjustment of the torque hysteresis amplitude is the ultimate goal. The simulation results show that the DTC system with hysteresis amplitude adjustment fuzzy logic controller can reduce the pulsation of the motor torque and flux, and improve the performance of low-speed operating conditions.