Flexible PWM control of three-level inverters for fuel cell/battery supplied aeromobile drive

New method of synchronized pulsewidth modulation (PWM) has been disseminated for control of dual neutral-point-clamped inverters feeding asymmetrical dual three-phase (six-phase) motor drive with two DC voltage sources. A novel control strategy for this drive topology is based on variation of switching frequencies of each inverter depending on the magnitudes of voltages of the corresponding DC sources. Specialized control scheme provides in this case full elimination of alternating common-mode voltages both in each inverter and in the load. Phase voltages of the drive system are characterised by symmetry during the whole control range. Simulations give the behaviour of dual three-phase system with synchronized PWM. Continuous, discontinuous, ¿direct-direct¿ and combined versions of synchronized PWM, applied for control of dual three-level converters, have been analyzed and compared.