A Multilevel Open-End Winding Six-Phase Induction Motor Drive Topology Based on Three Two-Level Three-Phase Inverters

This paper presents a nine-leg (9L) multilevel inverter to drive a six-phase induction machine in an open-end winding (OEW) configuration. The system is based on three conventional two-level three-phase voltage source inverters (VSIs) and three, two, or one isolated dc links. A machine with two sets of 30 degrees shifted three-phase stator windings is considered. The inverter operating principles are discussed and a simple space-vector pulse-width modulation (SV-PWM) is proposed. The 9L-OEW system is compared with two conventional drives: the six-leg two-level (6L), and the 12-leg OEW (12L-OEW) systems. The number of components, the required dc-link voltage, voltage and current harmonic distortions, torque ripple, and semiconductor losses are considered as figures of merit. Simulations and experiments were also performed, showing steady-state results for a 1 HP machine operating at constant torque.