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A scheme for a three-level voltage space phasor generation with common-mode voltage elimination is proposed. An open-end-winding induction motor, fed from both ends by two three-level inverters, which are realised by a cascading two two-level inverter, is used in this configuration. The voltage space vectors of individual three-level inverters, which generate the same common-mode voltage in the inverter pole voltage, are variously grouped. When these voltage space vectors are used to switch individual three-level inverters, it results in zero common-mode voltage across the motor windings. In the proposed scheme, voltage space phasors from individual inverters with zero common-mode voltage in the inverter pole voltage are used for PWM control. For the proposed drive configuration, the DC link voltage requirement is only half when compared to the DC link voltage of a conventional neutral-point-clamped (NPC) three-level inverter. The proposed inverter configuration offers reduced circuit and control complexity when compared to similar schemes with NPC or H-bridge inverter configurations.
Date of Publication: 4 March 2005