Synchronized PWM control of asymmetrical dual-inverter fed open-end winding traction drive

Space-vector-based synchronized PWM algorithms have been applied to the control of a dual-inverter fed open-end winding induction motor drive supplied by two isolated dc sources with non-equal voltages. It has been shown that algorithms of synchronized PWM provide continuous phase voltage symmetry for any ratio (integral or fractional) of switching frequency to fundamental frequency of the inverters and also for any ratio between the two dc source voltage levels of these systems. Phase voltage spectra of open-end winding drives for both continuous and discontinuous schemes of synchronized PWM do not contain even harmonics and sub-harmonics during the whole control range, including the zone of over-modulation which is especially important for the medium and high-power traction systems.