A five-level inverter topology with common-mode voltage elimination for induction motor drives

Abstract

Common-mode voltages generated by PWM inverters in induction motor drives cause shaft voltages, bearing currents and ground leakage currents resulting into early mechanical failure of machine bearings and conducted EMI. A five-level inverter topology with switching state combination selection strategy for the PWM control is proposed for an open-end winding induction motor drive, which completely eliminates the common-mode voltages at inverter poles and machine phase windings, in the complete modulation range of the drive. The proposed induction motor drive structure offers reduced device count, simple power-bus structure and more number of redundant switching state combinations when compared to a conventional five-level NPC inverter fed induction motor drive. The DC-link voltage requirement for the proposed five-level inverter fed drive scheme is half compared to that of conventional five-level inverter fed drive and hence it needs power devices with lower blocking voltage capability, which makes the proposed inverter topology suitable for high power induction motor drive applications