Kriegers Flak – Combined Grid Solution: World’s first hybrid interconnector

The ‘Combined Grid Solution’ (CGS) is a hybrid system that interconnects the grid of north-eastern Germany with the Danish island of Zealand utilising the grid connection infrastructure of the German offshore wind farms Baltic 1 and 2 and the Danish offshore windfarm Kriegers Flak. It’s the first of its kind worldwide and will be operational before year-end.

 

Highlights

• CGS effectively manages fluctuations in intermittent supply and demand.
• It provides black-start capability by linking Scandinavian and continental grids.
• CGS aims to foster the European energy transition by strengthening grid integration of renewables and security of supply, especially for the Danish island of Zealand.
• Early dialogue and public participation accompanied the project systematically from start to finish, achieving high local acceptance.
• The project can be seen as a starting point for future meshed offshore grids.

 

About the practice

Due to the short distance between the German ‘Baltic’ wind parks and the Danish ‘Kriegers Flak’ wind parks the idea of creating a system that includes both, offshore wind park feed-in and cross-border interconnection capacity was born. This way, a better utilisation of offshore infrastructure than normal can be reached in the interest of society: when the wind is strong the grid infrastructure is used to transport wind power, when the wind is weak or not blowing at all, it is used to exchange electricity between Germany and Denmark.

What makes the project unique on a global scale is the combination of an interconnector with grid connections of offshore wind, as well as the way the complex hybrid system is going to be operated. A newly developed Master Controller for Interconnector Operation (MIO) with the latest information technology will be installed in the 50Hertz Control Centre in Berlin.The Master Controller acts as the ‘brain’ of the entire system. It calculates the available capacity of the interconnector (based on wind forecasts and the resulting wind infeed) in real-time, prevents overload by controlling the converter and/or the wind farms, maximises the feed-in from the wind farms through active system control, and controls the exchange of electricity between the grids of both countries by means of the converter installed in Mecklenburg-Western Pomerania (Germany). This way, the cable connection can be utilised to a much higher extend, thus maximising social welfare for society.

 

Find out more

The project is based on a partnership between the German transmission system operator (TSO) 50Hertz and the Danish TSO Energinet. This partnership includes the planning phase as well as the future operation of the interconnector, since both, 50Hertz and Energinet own all assets on equal shares. Further project partners, such as ABB and EnBW support the construction of the hybrid interconnector.