Improvement of direct torque control performance by using a discrete SVM technique

The basic concept of direct torque control of induction machines is investigated in order to emphasise the effects produced by a given voltage vector on stator flux and torque variations. The low number of voltage vectors which can be applied to the machine using the basic DTC scheme may cause undesired torque and current ripple. An improvement of the drive performance can be obtained using a new DTC technique based on the application of space vector modulation for prefixed time intervals. In this way, a sort of discrete space vector modulation is introduced. Numerical simulations and experimental tests have been carried out to validate the proposed method.