New aspects of a direct torque controlled induction motor drive

Abstract

Direct torque control (DTC) is a competitive alternative to the field oriented control nowadays in practical application. By DTC, the flux and the torque of the induction machine can be controlled directly. This paper presents a simulation working under the DTC concept, but for practical implementation some new aspects should be investigated: (1) the current is controlled indirectly, requiring the implementation of the current limitation mainly during starting operation; (2) the low speed operation is a special case of this drive. The possible unstable operating should be avoided; and (3) the dynamic limits of the power switches must be considered. It contains the switching frequency, the minimal pulse width and the dead-time of the switches in the same inverter leg. Simulation and experimental results are given.