Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The purpose of a solid state transformer (SST) is to use power electronic converters to mimic
the operation of the conventional distribution transformer. These power electronic converters
are proposed to overcome the disadvantages of the conventional distribution transformer. The
advantages of a SST include near perfect voltage regulation and harmonic isolation between the
primary and secondary windings of the transformer.
This thesis discusses the design and development of the different converters in a solid state
transformer (SST). A prototype modular back-to-back converter is developed for the input and
isolation stage of the SST. The isolation stage consists of a high voltage DC-DC converter, which
transfers power across the isolation barrier of the SST. This stage is evaluated in the laboratory
with special attention being paid to the efficiency of the converter.
The second aspect that this thesis addresses is the output stage of the SST, namely a three
phase inverter. The discussion of the output stage focuses on the losses occurring in the inverter.
The switching device losses are calculated by means of an adapted numerical method as opposed
to using conventional analytical methods. The presented numerical method is compared to the
existing analytical method and the findings are discussed.
A double loop control strategy is implemented for the output stage inverter. The inner
current loop utilizes a predictive control strategy. The control analysis of the double loop
controller is discussed and evaluated in the laboratory. All the converters that are discussed in
this thesis are evaluated in the laboratory and the relevant measurements are included. / AFRIKAANSE OPSOMMING: Die doel van ’n drywingselektroniese transformator (DET) is om drywingselektroniese omsetters
te gebruik om die werking van die konvensionele distribusietransformator na te boots. Hierdie
drywingselektroniese omsetters word voorgestel ten einde die nadele van die konvensionele distribusietransformator
te bowe te kom. Die voordele van ’n DET sluit in: feitlik perfekte regulering
van spanning en harmoniese isolasie tussen die primˆere en sekondˆere windings van die
transformator.
Hierdie tesis bespreek die ontwerp en ontwikkeling van die verskillende omsetters in ’n drywingselektroniese
transformator (DET). ’n Prototipe modulˆere rug-aan-rug-omsetter word ontwikkel
vir die intree- en isolasiefase van die DET. Die isolasiefase bestaan uit ’n hoogspanning-
GS-GS omsetter, wat drywing oor die isolasiegrens van die DET heen oordra. Hierdie omsetter
word in die laboratorium ge¨evalueer met besondere aandag aan die doeltreffendheid van die
omsetter.
Die tweede aspek waarna in hierdie tesis gekyk word, is die uittreefase van die DET, naamlik
’n driefaseomsetter. Die bespreking van die uittreefase fokus egter op die verliese wat in die omsetter
voorkom. Die verliese van die skakelaars word bereken deur middel van ’n aangepaste numeriese
metode teenoor die gebruik van konvensionele analitiese metodes. Die numeriese metode
wat aangebied word, word vergelyk met die bestaande analitiese metode en die bevindings word
bespreek.
’n Dubbellus-beheerstrategie word vir die uittreefase-omsetter ge¨ımplementeer. Die binneste
stroomlus word ge¨ımplementeer deur van ’n voorspelbare beheerstrategie gebruik te maak. Die
beheeranalise van die dubbellusbeheerder word bespreek en in die laboratorium ge¨evalueer. Al
die omsetters wat in hierdie tesis bespreek word, word in die laboratorium ge¨evalueer en die
relevante metings word ingesluit.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2773 |
| Date | 12 1900 |
| Creators | Wolf, Marko |
| Contributors | Mouton, H. du T., Van der Merwe, W. J., University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Rights | University of Stellenbosch |
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