Torque ripple minimization in Direct Torque Control based induction motor drive using multilevel inverter

In the classical DTC scheme using 2 level inverter, due to the limited number of voltage vectors large and small errors in torque or flux cannot be distinguished. In fact switching vectors chosen for large errors are same as for small errors. Because of this reason torque and flux ripples are high in case of classical DTC scheme using 2 level inverter. In this work in order to overcome this problem multi level inverter is used instead of 2 level inverter. This work presents a novel Direct Torque Control algorithm to be applied in induction motor electric drives supplied by 3-level Diode Clamped inverters. Results obtained with numerical simulation show that the employment of a 3 level inverter in such a control scheme permits to obtain the same dynamic performances as those obtained with a 2 level inverter with resulting far lower torque ripple.