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Design of a Medium Voltage Generator with DC-Cascade for High Power Wind Energy Conversion Systems

: Steffen, Jonas; Lengsfeld, Sebastian; Jung, Marco; Ponick, Bernd; Herranz Gracia, Mercedes; Spagnolo, Aristide; Klöpzig, Markus; Schleicher, Klaus; Schäfer, Klaus

Fulltext urn:nbn:de:0011-n-6362747 (6.6 MByte PDF)
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Created on: 29.6.2021

Energies 14 (2021), No.11, Art. 3106, 17 pp.
ISSN: 1996-1073
Bundesministerium fur Wirtschaft und Energie BMWi (Deutschland)
6. EFP-Windenergie; 0325502; MagnetRing III
Entwurf und Integration eines segmentiertenMittelspannungsgenerators für große Windenergieanlagen
Journal Article, Electronic Publication
Fraunhofer IEE ()
DC-cascade; PMSG; wind power; dc-voltage; medium voltage

This paper shows a new concept to generate medium voltage (MV) in wind power application to avoid an additional transformer. Therefore, the generator must be redesigned with additional constraints and a new topology for the power rectifier system by using multiple low voltage (LV) power rectifiers connected in series and parallel to increase the DC output voltage. The combination of parallel and series connection of rectifiers is further introduced as DC-cascade. With the resulting DC-cascade, medium output voltage is achieved with low voltage rectifiers and without a bulky transformer. This approach to form a DC-cascade reduces the effort required to achieve medium DC voltage with a simple rectifier system. In this context, a suitable DC-cascade control was presented and verified with a laboratory test setup. A gearless synchronous generator, which is highly segmented so that each segment can be connected to its own power rectifier, is investigated. Due to the mixed AC and DC voltage given by the DC-cascade structure, it becomes more demanding to the design of the generator insulation, which influences the copper fill factor and the design of the cooling system. A design strategy for the overall generator design is carried out considering the new boundary conditions.