FORCE COMMUTATED HVDC AND SVC BASED ON PHASE-SHIFTED MULTI-CONVERTER MODULES

This paper examines how the presently available gate-turn-off thyristors (GTOs), which are still relatively slow, may be used in force-commutated HVdc and SVC converters by employing multi-converter modules in conjunction with a phase-shifting principle which cancels the undesirable switching harmonics. It points to the advantages of incorporating the well-known Sinusoidal Pulse Width Modulation (SPWM) technique because it 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.