The Federal Ministry for Economic Affairs and Energy (BMWi) is now funding a collaborative project involving the University of Bremen, the Fraunhofer Institute for Wind Energy Systems (IWES) and industrial partners with 3.8 million euro. The aim of the project is to develop new structures in the DC grid to improve the economic potential of offshore wind turbines.

The experts know all about it – the “average consumer” usually not: How does the electricity get into the wall? “In Germany, this is done via three-phase networks. Everyone knows the overhead power lines that criss-cross the countryside,” explains Holger Raffel from the Bremen Center for Mechatronics at the University of Bremen. “However, worldwide it is more usual to use DC to transport electricity over long distances. This is done through point-to-point connections on high-voltage DC transmission links – HVDC lines, for short.” – For example, when electricity is transported from Sweden to Germany or from a distant wind farm off the coast.

How does electricity get from north to south with low loss?

Holger Raffel is the coordinator of the new collaborative project “Multi-Terminal Intelligent / Integrated Grids” (MuTiG), in which, in addition to the University of Bremen’s Institute for Electric Drives, Power Electronics and Components (IALB) and the Fraunhofer IWES (Bremerhaven), the industrial partners ABB AG (Ladenburg) and wpd offshore solutions GmbH (Bremen) also participate. The researchers want to develop the direct current solution with linked HVDC lines for use in Germany. Why? “Currently, there is a lot of discussion about how the offshore electricity generated in the north will cope with travelling over long distances to the south – from the coast to the mountains, so to speak,” says Raffel. Of course, it’s also possible to use the existing three-phase networks. “But over long distances, big losses can occur. Nobody wants that. By contrast, direct-current lines are low-loss – and therefore significantly more economical.”

Sophisticated control technology is necessary to implement such a solution – and the know-how for this comes from the state of Bremen. The IALB and the IWES have been working at different levels for many years on the physical and electrical challenges involved in the generation and transmission of offshore wind energy. Together with the industrial partners in the MuTiG project, they now want to coordinate research and application in order to create the electricity grid of tomorrow.

Will the electricity pylons disappear from the landscape one day?

The MuTiG project partners are not just concerned with making the transport of electricity from north to south low-loss. “The point-to-point connections on HVDC lines must be thought of as power cables running side-by-side from the coast to Bavaria, Saxony or Thuringia. We now want to link these adjacent routes together in numerous places. This has the advantage, for example, that – if a cable were to break somewhere – the power could be diverted to the south via another cable,” says Raffel. “As HVDC cables are nowadays usually laid underground, it could one day even lead to the disappearance of electricity pylons in Germany. But that's still a future dream.”

In order to connect the strands functionally, intelligent converter stations are required. One of the tasks within the project is to efficiently manage the various everyday situations that can occur. For modern power transmission systems are highly sensitive. Even small fluctuations can upset the balance – the risk of a “blackout” looms in the background. The joint research should ultimately also serve to make the German and European electricity grids more robust. Beside the technical challenges, over the next three years the four project partners will be investigating the legal and economic aspects as well as.

Attention editors: Photos for this press release can be downloaded here: https://seafile.zfn.uni-bremen.de/f/a3c4cac50d54411ab3d5/.

If you have any questions on this topic, feel free to contact:

Dr. Holger Raffel
University of Bremen
Bremen Center for Mechatronics
Phone: 0421 / 218-62690
Email: raffelprotect me ?!mechatronik-bcmprotect me ?!.de
www.mechatronik-bcm.de

About the project partners: ABB AG from Ladenburg contributes its expertise and experience in the field of HVDC systems as part of the research project. The global technology developer and manufacturer will focus on interconnect topologies for the conversion of electrical energy and solutions for monitoring and protecting electrical networks. Owing to its many years of international experience in implementing wind energy projects, the Bremen-based wpd offshore solutions GmbH supports German offshore wind projects in the areas of terminal connection, operation, risks and responsibilities. The Fraunhofer IWES brings its expertise and experience in the field of plant and park modeling, plant operation management and control as well as in the field of real-time simulation into the consortium. In the MuTiG project IWES conducts the system and interpark network modeling and develops new solutions for the overall system model of the offshore wind energy transmission system.

www.iwes.fraunhofer.de
www.abb.com/de
www.wpd.de
www.ialb.uni-bremen.de