Stacked multilevel inverter fed six phase induction motor with reduced DC link and lower voltage devices

This paper proposes a novel configuration of six phase IM to drive from a three phase stacked multilevel inverter. Apart from greater fault tolerance compared to three phase, a six phase machine enables the use of low voltage devices for the inverter. Also the inverter used here is a three phase nine level stacked inverter which itself uses low voltage devices. Thus MOSFETs can be used for the inverter. The nine level inverter is formed by stacking 2 five level inverters each of which is developed by cascading an FC and a capacitor fed H-bridge. The inverter can be stacked further to obtain still higher number of voltage levels. This enables the use of batteries at the front end and still lower voltage devices which will significanly improve the efficiency. Hence this will find applications in electric vehicles because of the direct battery drive. Experiment is conducted on a 15 KW six phase IM by reconfiguring it as a three phase machine and driven by the three phase nine level stacked inverter using V/f control scheme. Detailed experimental results are provided to validate the concept.