A New Modulation Method for Hexagram Inverter

Recently, Hexagram inverter has been proposed for medium-voltage variable speed drive systems. It is composed of six interconnected three-phase two-level voltage source inverters, and has the advantages of modular and symmetrical structure, even and much reduced voltage stress, low dc energy storage requirement, and easy control with well-developed two-level control techniques, and therefore, has the potential for future high power applications. This paper presents a modulation method for the Hexagram inverter, which improves the number of steps in the output voltages so as to reduce the voltage harmonics and operational dv/dt. Simulation and experimental results are both provided.