A Seven Level Voltage Space Phasor Generation Scheme For An Open-End Winding Induction Motor Drive With Asymmetric Dc Link Voltages

Abstract

A seven-level inverter scheme, for an open-end winding induction motor drive, is proposed in this paper. The open-end winding induction motor is fed from both sides with three-level inverters. Each three-level inverter is formed by cascading two two-level inverters. The DC link voltage of the top two-level inverter is equal to Vdc /3, while the DC link voltage of the bottom two-level inverter is Vdc /6, where Vdc is the DC link voltage of the equivalent two-level inverter. This results in the space vector combinations similar to conventional seven-level inverter. The proposed seven-level inverter configuration requires lesser number of switching devices as compared to conventional seven-level inverter scheme. Similarly, lesser isolated power supplies are required when compared to the cascaded H-bridge configuration. A space phasor based PWM modulator is used for generation of inverter leg switching times and inverter-switching vectors, directly from instantaneous sampled magnitudes of reference voltages. The proposed scheme is implemented on a 1.5 kW, induction motor and the experimental results are presented.