Multi-level converters: a real solution to high voltage drives?

Multi-level converters are a small family of inverter circuit topologies whose final output voltage is made up by stepping through several intermediate voltage levels. Each of these topologies has a different mechanism for providing the voltage levels, and switching them to the output. The three main circuits are: the isolated H bridge circuit; the flying capacitor circuit; and the diode clamped circuit. This paper reviews these three topologies for use in high voltage high power variable speed AC motor drive