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Performance of the modular multilevel converter with redundant submodules
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion. ABB Corporate Research.
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
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2015 (English)In: IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society, Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 3922-3927, article id 7392712Conference paper, Published paper (Refereed)
Abstract [en]

The modular multilevel converter (MMC) is the state-of-the-art voltage-source converter (VSC) topology used for various power-conversion applications. In the MMC, submodule failures can occur due to various reasons. Therefore, additional submodules called the redundant submodules are included in the arms of the MMC to fulfill the fault-safe operation requirement. The performance of the MMC with redundant submodules has not been widely covered in the published literature. This paper investigates the performance of the MMC with redundant submodules in the arms. Two different control strategies are used and compared for integrating redundant submodules. The response of the MMC to a submodule failure for the two strategies is also studied. Moreover, the operation of the MMC with redundant submodules is validated experimentally using the converter prototype in the laboratory.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2015. p. 3922-3927, article id 7392712
Keyword [en]
Modular multilevel converter, redundancy
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
SRA - Energy
Identifiers
URN: urn:nbn:se:kth:diva-185746DOI: 10.1109/IECON.2015.7392712ISI: 000382950703162Scopus ID: 2-s2.0-84973163763ISBN: 9781479917624 (print)OAI: oai:DiVA.org:kth-185746DiVA, id: diva2:923319
Conference
41st Annual Conference of the IEEE Industrial Electronics Society, IECON 2015, Pacifico YokohamaYokohama, Japan, 9 November 2015 through 12 November 2015
Funder
StandUp
Note

QC 20161104

Available from: 2016-04-26 Created: 2016-04-26 Last updated: 2018-05-22Bibliographically approved
In thesis
1. Efficient Modeling of Modular Multilevel Converters for HVDC Transmission Systems
Open this publication in new window or tab >>Efficient Modeling of Modular Multilevel Converters for HVDC Transmission Systems
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The drive towards getting more and more electrical energy from renewable sources, requires more efficient electric transmission systems. A stronger grid, with more controllability and higher capacity, that can handle power fluctuations due to a mismatch between generation and load is also needed. High-voltage dc (HVDC) provides efficient and economical power transmission over very long distances, and will be a key player in shaping-up the future electric grid. Due to its outstanding features, the modular multilevel converter (MMC) has already been widely accepted as a key converter topology in voltage-source converter (VSC)-based HVDC transmission systems.

In order to study the feasibility of future MMC-based HVDC grids, adequate simulation models are necessary. The main objective of the thesis is to propose MMC reduced-order simulation models capable of accurately replicating the response of an MMC during all relevant operating conditions. Such models are the basic building blocks in developing efficient simulation models for HVDC grids. This thesis presents two MMC equivalent simulation models, the continuous model (CM) and the detailed equivalent model (DEM). Compared to the CM, the DEM is also capable of demonstrating the individual sumodule behavior of an MMC. These models are validated by comparing with the detailed MMC model as well as with experimental results obtained from an MMC prototype in the laboratory. The most significant feature of the models is the representation of the blocking capability of the MMC, presented for the first time in the literature for an MMC equivalent simulation model. This feature is very important in replicating the accurate transient behavior of an MMC during energization and fault conditions. This thesis also investigates the performance of the MMC with redundant submodules in the arms. Two different control strategies are used and compared for integrating redundant submodules.

The proposed MMC models are used in developing point-to-point and multiterminal HVDC (MTDC) systems. A reduced-order model of a hybrid HVDC breaker is also developed and employed in the MTDC system, making the test system capable of accurately replicating the behavior of the MMCbased MTDC system employing hybrid HVDC breakers. The conclusion of the analysis of dc-side faults in a MTDC system is that fast-acting HVDC breakers are necessary to isolate only the faulted part in the MTDC system to ensure the power flow in rest of the system is not interrupted.

A generic four-terminal HVDC grid test system using the CM model is also developed. The simulated system can serve as a standard HVDC grid test system. It is well-suited to electromagnetic transient (EMT) studies in a limited version of commercially available EMT-type software. The dynamic performance of the HVDC grid is studied under different fault conditions.

Abstract [sv]

Utvecklingen mot att utvinna alltmer elektrisk energi från förnybara källor kräver mer effektiva elektriska transmissionssystem. Det behövs också ett starkare nät, med högre styrbarhet och högre kapacitet, som kan hantera effektfluktuationer pga obalans mellan generering och last. Högspänd likströmsöverföring (HVDC) erbjuder energieffektiv och kostnadseffektiv effektöverföring på långa avstånd. På grund av sina överlägsna egenskaper har modulära multinivå-omvandlare (MMC) accepterats som den rådande tekniken för HVDC med spänningsstyva effektomvandlare (VSC).

För att kunna studera framtida MMC-baserade HVDC-nät är lämpliga simuleringsmodeller nödvändiga. Huvudmålet med denna avhandling är att ta fram kompakta simuleringsmodeller för MMC. Dessa kompakta modeller ska kunna efterlikna responsen för en MMC i alla relevanta fall, och ska kunna användas som beräkningseffektiva byggblock vid simulering av HVDC-nät. Denna avhandling presenterar två ekvivalenta simuleringsmodeller för MMC, den kontinuerliga modellen (CM) och den detaljerade ekvivalenta modellen (DEM). I jämförelse med CM kan DEM också representera egenskaper av enstaka submoduler i en MMC. Modellerna valideras genom inbördes jämförelse och jämförelse med experimentella resultat från en MMC prototyp. Den mest betydelsefulla egenskapen hos modellerna är representationen av blockeringsfunktionen för MMC:n, vilket presenterades för första gången för simuleringsmodeller genom detta arbete. Denna funktion är mycket väsentlig för att beskriva transienta egenskaper hos MMC:n vid uppstart och felfall. Avhandlingen undersöker även MMC:ns egenskaper med redundanta submoduler i omvandlar-armarna. Två olika styrmetoder används och jämförs.

De framtagna MMC-modellerna används för att utveckla punkt-till-punkt- och multiterminal-HVDC (MTDC). En kompakt modell för en hybdrid-HVDC-brytare tas också fram och används i MTDC-systemet. Därigenom kan ett MMC-baserat MTDC-system med hybrid-HVDC-brytare beskrivas noggrant. Analysen av fel på likströmssidan av MTDC-systemet fastslår att snabba HVDC-brytare är nödvändiga för att isolera den felbehäftade delen av nätet utan att stoppa effektflödet i resten av systemet.

Ett generiskt fyrterminal-HVDC-system med CM-modellen utvecklas också. Det simulerade systemet kan tjäna som ett standard-testsystem för elektromagnetiskt transienta (EMT) studier vid användning av den begränsade versionen av den kommersiellt tillgängliga EMT-programvaran. De dynamiska egenskaperna av HVDCnätet studeras också för olika felfall.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 49
Series
TRITA-EECS-AVL ; 2018:39
Keyword
High-Voltage dc, Modular Multilevel Converter, Voltage-Source Converter, HVDC Grids, Multiterminal DC Systems, Hybrid HVDC Breaker, Modeling
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-228310 (URN)978-91-7729-798-7 (ISBN)
Public defence
2018-06-14, Q2, Osquldas väg 10, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180522

Available from: 2018-05-22 Created: 2018-05-21 Last updated: 2018-05-22Bibliographically approved

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