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Hitachi ABB Power Grids pioneered offshore HVDC connections with world's most powerful converter platform in the North Sea

DolWin2 is the third offshore wind connection project that Hitachi ABB Power Grids has executed for transmission system operator TenneT in Germany’s North Sea, following BorWin1 and DolWin1. The high-voltage direct current (HVDC) link connects offshore wind farms to the mainland grid and has the capacity to supply more than a million households with renewable energy. DolWin2 supports Germany’s “Energiewende” roadmap, which aims to generate more than 15 gigawatts (GW) of offshore wind power by 2030.

The 916 megawatt (MW) link deploys Hitachi ABB Power Grids’ HVDC Light®, Voltage Source Converter (VSC) based technology and includes a 320 kilovolt (kV) converter station, housed on an offshore platform about 45 km offshore, making it the world's most powerful installation of its kind in operation.

The wind farms are connected with AC cables to the HVDC converter station installed on the offshore platform. The power is then converted to DC and transmitted by cable to the onshore converter station, where it is converted back to AC and safely integrated into the AC-grid. The HVDC Light system used offers advanced stabilizing capability benefitting both the AC-network and the windfarm. The technology is ideal for connecting remote wind farms to mainland networks without distance limitations or constraints on the grid.

The technology is ideal for connecting remote wind farms to mainland networks without distance limitations or constraints on the grid enabling large scale integration of renewable power, supporting the green transition. It also provides numerous environmental benefits, such as electrical losses of less than one percent per converter station and compact converter stations.

Hitachi ABB Power Grids’ scope covered the overall project responsibility and system engineering including design, supply and installation of the offshore converter station, sea and land cable systems and the onshore converter station. Aibel has designed and built the platform. The usage of underground cable systems minimized environmental impacts.

Map for DolWin2 project, from DolWin Beta till Dörpen West in Germany
Illustrated overview for DolWin2 project
Main data
Commissioning year: 2017
Power rating: 916 MW 
No of circuits: 1
AC voltage: 155 kV (Platform DolWin beta),
380 kV (Dörpen West)
DC voltage: ±320 kV
Length of DC submarine cable: 2 x 45 km
Length of DC underground cable: 2 x 90 km
Main reason for choosing HVDC Light®: Length of land and sea cables
Application: Offshore wind connections