Two-phase modulation technique for three-level inverter fed AC drives

Two-phase dipolar and unipolar modulation techniques for three-level inverters are suggested and compared with conventional three-phase ones. Two-phase PWMs with 60/spl deg/ (0/spl deg/ and /spl plusmn/30/spl deg/ shift) and 120/spl deg/ cycles are investigated from the point of view of harmonic losses, motor voltage spectra and torque pulsations. It is shown that two-phase dipolar PWMs have no advantages in comparison with three-phase PWMs. At the same time two-phase unipolar PWMs-in contrast with three-phase PWMs-considerably decrease the motor harmonic losses and torque pulsations in the whole motor voltage region.