Direct torque control of induction machines using discrete space vector modulation applied to traction

A control strategy of direct torque control (DTC) based on discrete space vector modulation (DSVM) system of induction motor fed with GTO voltage source inverter applied to railway traction is introduced. The switching frequency cannot be high in high power GTO inverter applications. When direct torque control of induction machines is implemented using microprocessor, undesired torque and current ripple happen because of using the six voltage vectors and the time delay due to digital implementation. An improvement of driver performance can be obtained using DSVM without increasing the frequency of the system. Moreover, it doesn't lead to extra complexity of the control system. Numerical simulation has been carried out to validate this method.