A Nine-Level Inverter System for an Open-End Winding Induction Motor Drive

A nine-level inverter system for an open-end winding induction motor drive is presented in this paper. Multilevel inversion is achieved by feeding an open-end winding induction motor with two symmetrical 3-level inverters from both ends. The combined inverter system with open-end winding induction motor produces voltage space phasor locations identical to a 9-level inverter. A total of 4096 space phasor combinations are available in the proposed scheme, distributed over 217 space vector locations. The proposed inverter drive scheme is capable of producing the phase voltage ranging from 2-level to 9-level depending on the depth of modulation. The inverter with the higher DC-link voltage is switching less frequently, compared to the inverter with the lower DC-link voltage.