Switching strategies in direct torque control of doublestar induction motors

AC drives based on direct torque control of double-star induction motors (DSIM) allow high dynamic performance to be obtained with very simple control schemes. Using a two-level voltage source inverter (VSI), the output voltages of PWM inverter can be represented by 8 space vectors in (d , q) plane. Then the amplitude and the rotating velocity of the flux vector can be controlled freely, both fast torque and optimal switching strategy can be obtained. In this paper a novel DTC scheme of double-star induction motors is proposed , the selection is based on the value of the stator flux and the torque. Compared to classical Field Oriented Control (FOC), which necessitates generally three feedback loops with P1 regulators, a current- regulated PWM converter, and two coordinate transformations, Direct Torque Control (DTC) uses only a couple of hysteresis comparators to perform both torque and flux dynamic control [11, The results obtained show superior performances over the FOC one without need to any mechanical sensor.