Synchronized pulsewidth modulation for different control regimes of AC drives

Both one-stage and two-stage schemes of feedforward synchronized pulsewidth modulation (PWM), applied to three-phase voltage source inverter with discontinuous voltage space vector modulation with the 30°-nonswitching intervals, have been described in the paper. Different control modes of inverter-fed drive systems with synchronized PWM, including standard scalar V/F control, and control regimes with nonlinear control dependencies between the fundamental voltage and fundamental frequency, have been analysed. Simulations give the behaviour of the PWM schemes and algorithms proposed. The output voltage waveforms of the inverter have quarter-wave symmetry during the whole control range including the zone of overmodulation, and its spectra do not contain even harmonics and combined harmonics, which is especially important for power adjustable speed drive systems with low switching frequencies.