Force commutated HVDC and SVC based on phase-shifted multi-converter modules

The authors examine how presently available gate-turn-off thyristors (GTOs), which are still relatively slow, can be used in force-commutated high-voltage direct-current (HVDC) and static VAR compensator (SVC) converters by employing multiconverter modules in conjunction with a phase-shifting principle which cancels the undesirable switching harmonics. They point out that incorporating the sinusoidal pulse-width modulation (SPWM) technique enables feedback control, active filtering and regulatory functions to be performed by the converters. This is because a reasonable bandwidth of the modulating signal is transmitted by the multiconverter station in spite of the low switching rates of the GTO valves