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Core component ordered for new German-Danish interconnector

50Hertz and Energinet.dk establish a 400 MW offshore interconnection using offshore wind-park connections

11.03.2016

By awarding the contract for a HVDC (high-voltage direct current) converter station in Bentwisch, Northern Germany, the transmission system operators 50Hertz and Energinet.dk make an important step towards establishing an interconnection between the national grids of Germany and Denmark. The “Kriegers Flak Combined Grid Solution” will be the world’s first offshore interconnection that is using the national grid connections to offshore wind-farms.

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Kriegers Flak – Combined Grid Solution

Together with its project partner, the Danish transmission system operator Energinet.dk, 50Hertz is planning the first offshore interconnector in the Baltic Sea by linking the two national offshore wind farm connections.

The so-called Kriegers Flak Combined Grid Solution (CGS) should connect the Danish region of Zealand with the German state of Mecklenburg-Western Pomerania. The planned transfer capacity is 400 megawatts (MW). The project partners are planning to start construction around the turn of the year (2016/17). It should become operational in late 2018.
Kriegers Flak – Combined Grid Solution Kriegers Flak – Combined Grid Solution

The project

Germany currently operates two offshore wind farms in the Baltic Sea, Baltic 1 (48 MW) and Baltic 2 (288 MW). At present, Denmark is preparing the construction of the offshore wind farm Kriegers Flak (600 MW). The Kriegers Flak (Denmark) and Baltic 2 (Germany) wind farms are less than 30 kilometres apart. The interconnector should be established by connecting both wind farms by means of two submarine cables.
The frequencies of the Danish and German transmission systems use a slightly different phase. That is why they need to be matched at the interface. This should be enabled by means of two serial voltage source converters (VSC). A converter transforms the alternating current (AC) from the Nordic interconnected system to direct current (DC). Another converter transforms this direct current back to alternating current - only now adapted to the synchronous area of continental Europe.

This so-called back-to-back converter should be installed in Bentwisch, near Rostock. The construction of the double converter on land is more favourable and allows easier maintenance than the construction and opration of the installation on an offshore platform. This was provided for in the original concept.

Due to the different voltage levels of the Danish and German offshore wind farms (150 to 220 kilovolt), a transformer is also required. However, this should be installed on the Danish offshore platforms.

Benefits of the connection

The new interconnector will further increase the security of supply of the German transmission system. Moreover, the new connection facilitates the integration of regionally generated renewable energy in Germany and in eastern Denmark. This renders renewables more useful and contributes to the success of the energy transition.

Project of common interest

The Kriegers Flak Combined Grid Solution has been categorised by the European Commission as a project of common interest (PCI). Such grid development projects are of particular importance as they close gaps in the European interconnected grid and contribute to the development of a single European energy market. Additionally, the project is subsidised by the European Energy Programme for Recovery (EEPR).

Schedule
Approval procedure: until the first half of 2017
Specification of the technical design: January 2010 - September 2014
Call for tenders and award of contract: October 2014 - June 2016
Production of the installations: January 2016 - June 2018
Construction and commissioning:
January 2017 - December 2018

 

Contact

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Axel Happe

Public participation

Axel Happe
Tel: +49 30 5150-3414
Fax: +49 30 5150-2199
E-Mail: axel.happe@50hertz.com