An eleven-level inverter system for dual-fed induction motor drive

In this paper, an eleven-level inverter system for dual-fed induction motor drive is described. The dual-fed structure is realized by opening the neutral-point of the conventional squirrel cage induction motor. The eleven-level inversion is obtained by feeding the dual-fed induction motor with an asymmetrical 4-level inverter from one end and a symmetrical 3-level inverter from other end. This inverter scheme does not experience neutral point fluctuations and uses a lesser number of DC sources compared to the series H-bridge topology. A multilevel carrier based Sinusoidal Pulse Width Modulation is implemented for the proposed drive where a progressive discrete DC bias depending upon the speed range is given to the reference wave to reduce the inverter switchings.