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

This paper examines how the presently available gate-turn-off thyristo rs (GTOs), which are still relatively slow, may be used in force-commu tated HVdc and SVC converters by employing multi-converter modules in conjunction with a phase-shifting principle which cancels the undesira ble switching harmonics. It points to the advantages of incorporating the well-known Sinusoidal Pulse Width Modulation (SPWM) technique beca use it enables feedback control, active filtering and regulatory funct ions to be performed by the converters. This is because a reasonable b andwidth of the modulating signal is transmitted by the multiconverter station in spite of the low switching rates of the GTO valves.