ABB, a leading power and automation technology company, has successfully commissioned a high-voltage direct current (HVDC) link between Norway and Denmark in order to the increase availability of renewable hydroelectric and wind power in the region’s power grid.
The 240km cable stretches across the Skagerrak Strait separating southern Norway and northern Denmark. It is Norway’s first new power link to Denmark since 1993. ABB also delivered Skagerrak 1 and 2 in the 1970s.
Transmission voltage record
The 500kV Skagerrak 4 link sets a new record in transmission voltage using Voltage Source Converters (VSC). The converters rely on semiconductors to convert electricity from HV alternating current to direct current and back, while offering controllability and compact design.
VSC links are increasingly being deployed in underground and subsea applications such as integration of renewable energies from land-based and offshore wind farms, mainland power supply to islands and offshore oil and gas platforms, city center in-feeds and cross-border interconnections.
This HVDC Light link reinforces the grid owned by Norwegian transmission system operator Statnett and Denmark’s Energinet.dk and helps balance loads between Norway’s hydroelectric-based system and Denmark’s wind- and thermal-based generation.
The existing Skagerrak interconnection, three HVDC cables with a combined 1,000MW of capacity, is already showing the world how wind and hydropower complement each other. According to the Danish Energy Agency, such interconnectors are why Denmark can accommodate the world’s highest levels of wind power, which met 41.2% of Danish demand in the first half of last year. Sometimes, wind power production even exceeds the country’s domestic power demand.
“We store their surplus in the hydro reservoirs and then feed it back on a seasonal basis or a daily basis. This is a very strong business case,” says Håkon Borgen, executive vice president at Statnett, Norway’s state grid operator.
The link will also help Denmark to reach its 85% renewables target by 2040. [Engerati – Denmark On Target for 85% Renewables by 2040.]
VSC converters offer new possibilities
For Skagerrak 4, ABB delivered two 700MW VSC stations based on the company’s HVDC Light technology. The new link operates in bipolar mode with the Skagerrak 3 link that uses classic Line Commutated Converter HVDC technology.
This is the first time the two technologies have been connected in such a bipole arrangement. ABB’s advanced MACH control system was used to master the different ways power reversal is handled between the two technologies.
In the future, use of 500kV VSC converters opens up new possibilities, especially when combined with ABB’s recently launched extruded 525kV HVDC cable. The world record cable will double power flow and extend the range to allow for greater integration of distant renewables.
The Skagerrak 4 stations are also the building blocks for more ambitious cables from Norway to wind-power heavyweights Germany and the United Kingdom. Construction on those is expected to commence over the next year.