The New Black Start: System Restoration with Help from Voltage-Sourced Converters

The very first commercial high-voltage dc (HVdc) transmission system, commissioned in 1954, had black-start capability. This system links the island of Gotland in the Baltic Sea with the Swedish mainland. Gotland had very few generating units, and the HVdc system was required to start up and deliver power without any generation operating on Gotland. Because the HVdc stations used line-commutated converters (LCCs), synchronous condensers were necessary to start up the dc system with a dead receiving network. This complicated the start-up sequence for system restoration.