Origin-shifted multilevel discontinuous pulse width modulation

Pulse width modulation of two-level power converters is presently well established with most reported strategies focusing on the minimisation of line voltage harmonic distortion. For multilevel inverter modulation, additional performance merits can be achieved through the proper selection of available redundant switching states. This paper presents the concept of equivalent space vectors to link two-level and multilevel modulation, and shows how the intelligent selection of equivalent states can give rise to a new origin-shifted 60°-discontinuous PWM strategy for modulating multilevel inverters with both minimal generated common mode voltage and harmonic distortion. The presented PWM strategy has been verified through simulation and experimentally using a three-phase, three-level inverter.