Prospects of multilevel VSC technologies for power transmission

Deregulation and privatization are posing new challenges to high voltage transmission and distributions systems. System components are loaded up to their thermal limits, and power trading with fast varying load patterns is leading to an increasing congestion. In addition to this, the dramatic global climate developments call for changes in the way electricity is supplied. Innovative solutions with HVDC (High Voltage Direct Current) and FACTS (Flexible AC Transmission Systems) have the potential to cope with the new challenges. New power electronic technologies with self-commutated converters provide advanced technical features, such as independent control of active and reactive power, the capability to supply weak or passive networks and less space requirements. In many applications, the VSC (Voltage-Sourced Converter) has become a standard for self-commutated converters and will be increasingly more used in transmission and distribution systems in the future. This kind of converter uses power semiconductors with turn-off capability.