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

A new multilevel inverter - Hexagram inverter [12], is introduced for medium-voltage adjustable speed drive systems. The new inverter is composed of six interconnected three-phase six-switch modules. With six terminals, Hexagram inverter can be configured for both six-phase and three-phase (floating neutral) motor drive. The focus of this paper is on Hexagram inverter for six-phase motor drive. With proposed Hexagram inverter topology, the semiconductor switches has half of the current stress and one third of the voltage stress compared to a same output power and output voltage VSI system, or the same current stress and one sixth voltage stress when compared to a same output power and output current VSI. With the modular six-switch structure, previously proposed control methods for VSI are all applicable. In this paper, One-Cycle Control and SPWM are respectively used for demonstration, simulation and experimental verification. The eminent characteristics of the Hexagram inverter including modular structure, low component count, low voltage and current stress, and automatic voltage and current balancing, make it an excellent candidate for high power motor drive applications.