Multilevel Voltage Space Phasor Generation for an Open-end Winding Induction Motor Drive

A topology for multilevel voltage space phasor generation for an open-end winding induction motor drive is presented in this paper. The open-end winding induction motor is fed from both ends by two 3-level inverters. Each 3-level inverter is formed by cascading two 2-level inverters. This results in voltage space phasor levels equivalent to a conventional 8-level inverter. The proposed 8- level inverter configuration requires lesser number of switching devices as compared to conventional 8-level inverter scheme. Compared to the H-bridge topology, the proposed scheme uses a lower number of power supplies. In the multilevel carrier-based Sinusoidal Pulse Width Modulation (SPWM), used for the proposed drive, a progressive discrete DC bias depending on the speed range is given to the reference wave so that the drive can operate in the i-level modes (i=2, 3, ...8) depending on the speed range. The inverter with the higher DC-link voltage is switching less frequently, compared to the inverter with the lower DC-link voltage.