High performance induction motor drive: A dither injection technique

In this paper, a three-level inverter fed induction motor drive operating under Direct Torque Control (DTC) is presented. DTC do not show good performance in low speed region due to stator flux demagnetization that relates to variation in stator resistance. Here, a sinusoidal wave is used as dither signal of minute amplitude (for torque hysteresis band and flux hysteresis band respectively) in the error block. Hence, this method is used to take care of the demagnetizing effect of flux vector near sector boundary. In this paper, sinusoidal dithering technique is applied to study the effect of settling time, flux demagnetizing effect, dc drift and initial value problem, flux and current ripple reduction. A laboratory prototype of the drive system has been developed and the simulation and experimental results are reported.