The ABCs of HVDC Transmission Technologies

Monopolar HVDC converter station.

HIGH VOLTAGE DIRECT CURRENT (HVDC) TECHNOLOGY has characteristics that make it especially attractive for certain transmission applications. HVDC transmission is widely recognized as being advantageous for long-distance bulk-power delivery, asynchronous interconnections, and long submarine cable crossings. The number of HVDC projects committed or under consideration globally has increased in recent years reflecting a renewed interest in this mature technology. New converter designs have broadened the potential range of HVDC transmission to include applications for underground, offshore, economic replacement of reliability-must-run generation, and voltage stabilization. This broader range of applications has contributed to the recent growth of HVDC transmission. There are approximately ten new HVDC projects under construction or active consideration in North America along with many more projects underway globally.

HVDC Applications

HVDC transmission applications can be broken down into different basic categories.

Although the rationale for selection of HVDC is often economic, there may be other reasons for its selection. HVDC may be the only feasible way to interconnect two asynchronous networks, reduce fault currents, utilize long underground cable circuits, bypass network congestion, share utility rights of- way without degradation of reliability, and to mitigate environmental concerns. In all of these applications,

HVDC nicely complements the ac transmission system.

This article discusses HVDC technologies; application areas where HVDC is favorable compared to ac transmission, system configuration, station design, and operating principles.

The ABCs of HVDC Transmission Technologies