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Modulation strategies for a mutually commutated converter system in 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).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
2007 (English)In: 2007 European Conference on Power Electronics and Applications, EPE, 2007, 1221-1230 p.Conference paper, Published paper (Refereed)
Abstract [en]

A novel mutually commutated converter (MCC) system consisting of a voltage source converter (VSC) and a cycloconverter connected by a medium-frequency (MF) transformer is adapted for the power collection and conversion in large wind farms. Different modulation strategies based on space vectors are described and evaluated with regard to the very restrictive constraints on the modulation and commutation of the thyristor valves in the cycloconverter. This paper shows that a feasible and effective modulation strategy can be found in order to provide the desired reference voltage vector during every single modulation interval and under all operating conditions. The proposed current clamping control strategy is based on stopping the gate pulses of the conducting thyristor valve during a certain dead-time whenever the current in the corresponding phase leg becomes zero.

Place, publisher, year, edition, pages
2007. 1221-1230 p.
Keyword [en]
modulation strategy, vector control, wind energy, adjustable speed generation system, HVDC
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-14303DOI: 10.1109/EPE.2007.4417478ISI: 000255993600134Scopus ID: 2-s2.0-51049112239ISBN: 978-90-75815-11-5 (print)OAI: oai:DiVA.org:kth-14303DiVA: diva2:332107
Conference
2007 European Conference on Power Electronics and Applications, EPE; Aalborg; Denmark; 2 September 2007 through 5 September 2007
Note

QC 20100802

Available from: 2010-08-02 Created: 2010-08-02 Last updated: 2014-10-29Bibliographically 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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