Direct self control of induction machines fed by a double three-level inverter

For variable speed induction motor drives with very high power and extreme demand on the quality of torque, a novel concept of feeding an induction machine with open windings by two gate-turn-off (GTO) three-level inverters is investigated. For optimal operation with the restricted switching frequency of these high-power inverters, direct self control (DSC) is mostly suited, which is well proven with two-level and three-level inverters in traction, allowing a highly dynamic control of the induction machine. In comparison with two-level and three-level inverters, torque ripple and distortion of motor currents are efficiently reduced, while maintaining the excellent dynamic qualities of DSC.