A New Multilevel Inverter - Hexagram Inverter for Medium Voltage Adjustable Speed Drive Systems Part II. Three-phase Motor Drive

A new multilevel inverter - Hexagram inverter [6] is proposed for medium-voltage adjustable speed drive systems. The new inverter is constructed by interconnecting six three-phase inverter modules. With six output terminals, hexagram inverter has two operation options: six-phase motor drive or three-phase motor drive (neutral floating). Article [7] has analyzed and verified the six-phase operation; therefore, the three-phase operation will be the focus of this paper. The study shows that the voltage stress of the hexagram inverter is only one sixth of a single VSI with the same output voltage. Simulation and experiment have verified the theoretical findings related to the proposed new inverter. With the eminent features, including modular structure, low component count, low voltage stress, low dc capacitor energy storage requirement, automatic current and power sharing, and easy control, the proposed hexagram inverter is an excellent candidate for high power motor drive applications.