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228 Power electronic equipment
Fig. 6.51 Sinusoidal PWM for the three-level single-phase half-bridge NPC VSC. (a) reference and two
carrier waveforms phase-shifted by 180 ; (b) control signal for switch S a1 ; (c) control signal for switch S a2 ;
(d) control signal for switch S a3 ; (e) control signal for switch S a4 ; (g) resultant line-to-neutral voltage
waveform v AO ; and (f) harmonic spectrum of the line-to-neutral voltage waveform v AO .
