ABB Review Special Report - ABB - ABB Group

sign underwent its first big change withthe introduction of thyristor valves inthe early 1970s. The first of these wereair-cooled and designed for indoor use,but soon outdoor oil-cooled, oil-insulatedvalves were also being used. Today,all HVDC valves are water-cooled [2].Good examples of modern bulk powerHVDC transmission are the links ABB isinstalling for the Three Gorges hydroelectricpower plant project in China.(See article starting on page 6.)In 1995 ABB presented a new generationof HVDC converter stations: ‘HVDC2000’ [3]. HVDC 2000 was developedto meet stricter electrical disturbancerequirements, to provide better dynamicstability where there was insufficientshort-circuit capacity, to overcomespace limitations, and to shorten deliverytimes.A key feature of HVDC 2000 was theintroduction of capacitor commutatedconverters (CCC). This was, in fact, thefirst fundamental change to have beenmade to the basic HVDC system technologysince 1954!HVDC 2000 also includes other ABB innovations,such as continuously tunedAC filters (ConTune), active DC filters,outdoor air-insulated HVDC valves, andthe fully digital MACH2 control system.Submarine cable for the 600-MW BalticCable HVDC link between Germany andSwedenBaltic Cable HVDC converter stationThe first project to employ HVDC 2000with CCC and outdoor valves was theGarabi 2200-MW HVDC back-to-backstation in the Brazil – Argentina HVDCInterconnection.HVDC Light TMHVDC technology has become a maturetechnology over the past 50 years andreliably transmits power over long distanceswith very low losses. This begsthe question: where is developmentwork likely to go in the future?It was conceived that HVDC developmentcould, once again, take its cuefrom industrial drives. Here, thyristorswere replaced a long time ago by voltagesource converters (VSC), with semiconductorsthat can be switched off aswell as on. These have brought manyadvantages to the control of industrialdrive systems and it was realized thatthey could also apply to transmissionsystems. Adapting the technology of voltagesource converters to HVDC, however,is no easy matter. The entire technologyhas to change, not just the valves.As development of its VSC converter gotunder way, ABB realized that the insulatedgate bipolar transistor, or IGBT,held more promise than all the otheravailable semiconductor components.Above all else, the IGBT needs onlyvery little power for its control, makingseries connection possible. However, forHVDC a large number of IGBTs wouldhave to be connected in series, somethingindustrial drives do not need.In 1994, ABB concentrated its developmentwork on VSC converters in a projectthat aimed at putting two convertersbased on IGBTs into operation forsmall-scale HVDC.An existing 10-km-long AC line in centralSweden was made available for theproject.At the end of 1996, after comprehensivesynthetic tests, the equipment was installedin the field for testing under serviceconditions. In 1997 the world’s firstVSC HVDC transmission system, HVDCLight [4], began transmitting powerbetween Hellsjön and Grängesberg inSweden.In the meantime, seven such systemshave been ordered, and six of them arenow in commercial operation in Sweden,Denmark, the USA and Australia.HVDC Light is now available for ratingsup to 350 MW, ±150 kV.ABB is to date the only company thathas managed to develop and build VSCHVDC transmission systems [5].Special ReportABB Review65