Three-dimensional pulse-width modulation technique in three-level power inverters for three-phase four-wired system

Shunt-connected trilevel power inverter in three-phase four-wired system as an active filter or individual current supply (peak-load supply) is studied by a novel technique: Three-dimensional (3-D) voltage vectors pulse width modulation (PWM), In past decades, almost all the study for PWM is limited in two-dimensional (2-D) domain, alpha and beta frames, in three-phase three-wired system. However, in practical operation, there are many three-phase four-wired systems in distribution sites. The generalized study of 3-D two-level and three-level inverters is achieved in this paper so as to perform the basic theory of 3-D multilevel space vector switching PWM technique. The sign cubical hysteresis control strategy is proposed and studied with simulation results in 3-D aspect. The 3-D PWM technique in three-level inverters is accomplished.