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Design Considerations for Medium-Frequency Power Transformers in Offshore Wind Farms
KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).ORCID iD: 0000-0002-8565-4753
KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).ORCID iD: 0000-0002-1755-1365
2009 (English)In: 2009 13th European Conference on Power Electronics and Applications, EPE '09, IEEE , 2009, 757-768 p.Conference paper, Published paper (Refereed)
Abstract [en]

In a recently proposed converter system for offshore wind farms, single-phase medium-fire (MF) transformers replace the conventional three-phase line-frequency transformers that convert the electricity from the wind turbine generators to high voltage. MF operation allows a reduction of the transformer size and weight, thus leading to a compact and efficient design, which minimizes the installation and maintenance costs, This paper presents design considerations for dry-type single-phase MF power transformers in offshore wind farms. Recent transformer problems in large wind turbines have shown that a thorough and careful magnetic, electric, and thermal design is required to ensure the reliability and performance of the transformers. As a result, a suitable design for a 3 MW wind turbine transformer is proposed.

Place, publisher, year, edition, pages
IEEE , 2009. 757-768 p.
Keyword [en]
Transformer, Design, Single phase system, Wind Energy
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-14306ISI: 000275384100085Scopus ID: 2-s2.0-72949120842ISBN: 978-1-4244-4432-8 (print)OAI: oai:DiVA.org:kth-14306DiVA: diva2:332111
Conference
13th European Conference on Power Electronics and Applications (EPE 2009) Barcelona, SPAIN, SEP 08-10, 2009
Note

QC 20100802

Available from: 2010-08-02 Created: 2010-08-02 Last updated: 2014-10-09Bibliographically approved
In thesis
1. System Aspects and Modulation Strategies of an HVDC-based Converter System for Wind Farms
Open this publication in new window or tab >>System Aspects and Modulation Strategies of an HVDC-based Converter System for Wind Farms
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 

In this thesis, a new HVDC-based converter system for wind farms is investigated. It is based on a mutually commutated soft-switching converter system and provides a unique integrated solution for the wind turbine generator drive systems, the wind turbine interconnection, and the power conversion for HVDC transmission.

In a wind farm, the mutually commutated converter system is a distributed system. A medium-frequency collection grid connects the converter station, equipped with a single-phase voltage source converter and a medium-frequency transmission transformer, with the wind turbines, each containing a cycloconverter and a medium-frequency distribution transformer. In this thesis, various system aspects regarding the application of a distributed mutually commutated converter system in a wind farm are investigated. Special attention is paid to the design of a medium-frequency collection grid that has an acceptable level of transient overvoltages, the design of medium-frequency transformers with suitable magnetic, electric and thermal properties, and the development of a strategy to commutate the voltage source converter during low power generation.

In order to adapt the mutually commutated converter system for an application in a wind farm, it had to be further developped. Different carrier-based and space-vector oriented modulation methods have been investigated. It turns out that for any load angle there is a quasi-discontinuous pulse width modulation strategy that can produce the same pulse patterns as space vector modulation. In addition, a modulation strategy has been developed that allows to replace the IGBTs in the cycloconverter with cheap, robust, and reliable fast thyristors, despite their absence of turn-off capability. The feasibility of different modulation strategies for mutually commutated converter systems has been verified on a down-scaled prototype converter system with both IGBT- and thyristor-based cycloconverters.

Finally, a feasible wind farm layout is proposed, which considerably reduces the energy generation costs for large winds farms distant to a strong grid connection point. As a consequence, the proposed solution may facilitate the establishment of remotely located wind farms.

 

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH, 2009. viii, 80 p.
Series
Trita-EE, ISSN 1653-5146 ; 2009:018
Keyword
Isolated AC/DC Converter, Mutual Commutation, Soft Switching, Voltage Source Converter, Cycloconverter, Modulation Strategies, Medium-Frequency Transformer, HVDC Transmission, Wind Power, Wind Farms
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-10267 (URN)978-91-7415-292-0 (ISBN)
Public defence
2009-05-18, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100802Available from: 2009-05-12 Created: 2009-04-28 Last updated: 2010-08-03Bibliographically approved

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Norrga, StaffanNee, Hans-Peter

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