Open-end multilevel six-phase machine drive system with five three-leg converters

Multi-phase machine drive have received considerable attention because of their numerous advantages over the traditional three-phase drive, such as high power handling capability by dividing the required power between multiple phases, reduced torque pulsations and higher reliability. Multilevel converter technologies have been widely recognized as viable solutions to overcome current and voltage limits of low power switching converters in high-power medium-voltage applications. This paper proposes and investigates a multilevel AC six-phase motor drive. The system is composed of five three-leg voltage source inverters (VSIs) feeding the open-end windings (OEW) of an asymmetrical six-phase induction motor (SPIM), which is adequate to generate multilevel voltages for high power system with current and voltage rating restrictions. The operating principles, the system model and a space vector pulse width modulation (SV-PWM) and its implementation by means of equivalent level-shifted PWM (LS-PWM) are presented. The PWM strategy is based on a space vector approach and is designed to improve the performance of the system in terms of harmonic distortion. Simulation results compare proposed and conventional configurations in terms of harmonic distortion and semiconductor losses. Experimental results were obtained by using IGBTs with dedicated drives and a digital signal processor (DSP) with appropriated plug-in boards and sensors.