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Loss evaluation for modular multilevel converters with different switching strategies
KTH, School of Electrical Engineering (EES), Electric power and energy systems.ORCID iD: 0000-0001-8788-0415
KTH, School of Electrical Engineering (EES), Electric power and energy systems.ORCID iD: 0000-0002-8565-4753
2015 (English)In: Power Electronics and ECCE Asia (ICPE-ECCE Asia), 2015 9th International Conference on, IEEE , 2015, 1558-1563 p.Conference paper (Refereed)Text
Abstract [en]

Apparently, modular multilevel converter (MMC) has been extensively used in high voltage direct current (HVDC) transmission links in recent years. The efficiency of MMC stations are highly related to the switching methods and semiconductor devices. So, various switching methods and semiconductor devices have been investigated and introduced in the field. This paper settles a benchmark for an HVDC link, based on a real project, and investigates the impact of six different switching methods on the converter loss, utilizing a commercial semiconductor device. The evaluation indicates that switching methods which consider the current level at switching instants are more efficient in comparison with the other methods which only consider the number of switching events. The result of this study is essential for more efficient converter stations.

Place, publisher, year, edition, pages
IEEE , 2015. 1558-1563 p.
Keyword [en]
HVDC power convertors, HVDC power transmission, switching convertors, HVDC transmission link, high voltage direct current transmission link, modular multilevel converter station, semiconductor device, Benchmark testing, Capacitors, HVDC transmission, Insulated gate bipolar transistors, Sorting, Switches, Switching loss, HVDC transmission, Power conversion, Switching frequency, Switching loss
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-182747DOI: 10.1109/ICPE.2015.7167984ScopusID: 2-s2.0-84961932810ISBN: 978-895708254-6OAI: oai:DiVA.org:kth-182747DiVA: diva2:905661
Conference
Power Electronics and ECCE Asia (ICPE-ECCE Asia), 2015 9th International Conference on
Funder
StandUp
Note

QC 20160418

Available from: 2016-02-23 Created: 2016-02-23 Last updated: 2016-09-16Bibliographically approved
In thesis
1. Modulation of Modular Multilevel Converters for HVDC Transmission
Open this publication in new window or tab >>Modulation of Modular Multilevel Converters for HVDC Transmission
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The outstanding features of modular multilevel converters (MMC) have recently gained much attention in the high-voltage direct-current (HVDC) transmission field. Power quality, converter cost and system performance are three crucial aspects of HVDC MMCs which are directly linked to the converter modulation and switching schemes. High power quality and performance require high switching frequency and large cell capacitor whereas low switching frequency and small cell capacitor are needed to reduce the converter cost.

The main objective of this thesis is to propose a practical switching method for HVDC MMCs which balances the aforementioned contradictory requirements. A mathematical analysis of the converter switching pattern, against the power quality and converter cost, has been conducted to formulate an optimization problem for MMCs. Different objective functions are studied for the formulated optimization problem such as converter loss minimization, voltage imbalance minimization and computational burden minimization. This thesis proposes three methods to address different objective functions. Ultimately, a real-time simulator has been built to practically verify and investigate the performance of the proposed methods in a realistic point-to-point HVDC link.

The most significant outcome of this thesis is the tolerance band-based switching scheme which offers a direct control of the cell capacitor voltage, low power losses, and robust dynamic performance. As a result, the converter switching frequency can reach frequencies as low as 70 Hz (with the proposed cell tolerance band (CTB) method). A modified optimized CTB method is proposed to minimize the converter switching losses and it could reduce the converter switching losses by 60% in comparison to the conventional phase shifted carrier modulation method.

It is concluded intelligent utilization of sorting algorithm can enable efficient HVDC station operation by reducing the converter cost.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 57 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2016:139
Keyword
HVDC, switching schemes, modulation, high power converters, power grids
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-192607 (URN)978-91-7729-098-8 (ISBN)
Public defence
2016-10-07, Sal D3, Kungl Tekniska Högskolan, Lindstedtsvägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160916

Available from: 2016-09-16 Created: 2016-09-15 Last updated: 2016-09-16Bibliographically approved

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