Together with the Technical University of Dresden and the University of the Federal Armed Forces in Munich, Siemens has carried out research work into a highly efficient and robust medium-voltage converter for feeding electrical energy into power supply grids.
The insights gained were successfully implemented within the scope of the research project funded by Germany‘s Federal Ministry of Research and Education (BMBF) on the basis of a demonstrator, and will be incorporated into the next generation of products.
Converters feeding into the grid based on power electronics are the key to efficient use of regenerative energy sources. They make sure that the electricity generated by wind or solar power installations is converted to the right frequency and voltage before it can be fed into the grid. At present, low-voltage converters up to 690 volts are used for this purpose. However, the line filters and transformers required for the infeed consume a considerable part of the power produced, which is then lost to the end user. In addition, the ever increasing capacity of plants, particularly those used in offshore wind farms, means that the power semiconductors used reach their technical limits, and so the use of medium-voltage converters from two to ten volts makes both economic and technical sense.
In the research project entitled ‚Medium-voltage converters based on a new type of circuit technology (M2C) for feeding electrical energy into power grids‘, a medium-voltage converter based on a modular structure was designed and put into practice that manages for the first time without additional line filters or transformers. Thus, such a converter can be designed for substantially greater energy efficiency and with reduced use of materials in comparison with current equipment. Based on a wind power station with a rated output of three megawatts, about 24,000 kWh electrical energy per year and wind power station can be fed into the grid additionally thanks to the new, highly efficient converter. Extrapolated to a wind farm with 50 turbines, this means that about 400 more households than before could now be supplied with electricity thanks to the new technology.
Moreover, the modular structure enables much more reliable operation because defective modules can be bypassed by deploying innovative cell bypass technology. Failure probability can thus be reduced by a factor of up to 5. Project manager Dr. Marc Hiller , who was honored for the new converter concept in 2009 together with Dr. Rainer Sommer from Siemens as the ‚inventor of the year‘, underscores that, „this special characteristic particularly benefits applications such as offshore wind power, where maintenance conditions are difficult. On many days in the year, such installations far out to sea are very difficult to reach and valuable energy is lost every day a system is down. The availability of such installations can now be boosted significantly thanks to M2C technology“ . Dr. Hiller also adds that „the research results will be incorporated directly into the new generation of medium-voltage converters and the new Sinamics SM120 platform. We can therefore strengthen our market and technology leadership in this field in the long term“ .
The M2C research project is jointly carried out by the “Institute for Intelligent System Technology” of the German University of the Federal Armed Forces in Munich and the chair of power electronics at the Electrical Engineering Institute of the Technical University of Dresden, and is funded by the German Ministry of Education and Research (BMBF). The project will run until 2013 and is backed by the ‚Power electronics for increasing energy efficiency‘ sponsored program under the high-tech strategy of the German government and the support program ‚Information and communication technology 2020‘ (IKT 2020). One of the objectives of the IKT 2020 program is to strengthen and extend Germany’s technological lead in the field of information and communication technology.
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Press release, August 8, 2013; Image: Siemens