DTC adaptation following the reconfiguration from three to two legs of a three level inverter fed induction motor drive

Direct torque control (DTC) strategies have been widely implemented in induction motor (IM) drives which are integrated in various industrial variable speed applications covering a wide range of power. In low power applications, the IM is associated to two level inverters, while in medium and high power applications it is associated to multi-level inverters, particularly the three level NPC topology. The paper deals with the adaptation of a DTC strategy following the reconfiguration from three to two legs of a three level inverter fed IM drive. A special attention is paid to the synthesis of the vector selection table, in so far as the number of the generated voltage vectors is reduced to nine, six among them are of half type, two are intermediate, and a null one, resulting in a limitation of the freedom degrees. Simulation results show that the drive remains sufficiently performant following the implementation of the proposed DTC strategy.