Optimal design methodology of a three phase Rotary transformer for a brushless doubly fed induction generator

Zietsman, Nikita Linda (2016-03)

Thesis (MEng)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: The brushless doubly fed induction generator (BDFIG) offers higher reliability over the standard doubly fed induction generator (DFIG), by eliminating the slip ring and brush assembly. The currently employed BDFIG configuration results in a more complex machine. In order to improve reliability while still retaining the simplicity of the DFIG, alternative brushless topologies have been explored. One such solution is to make use of a rotary transformer (RT) to replace the slip rings and brushes. The RT is placed on the same shaft as the generator and provides inductive coupling over the interface. Size and efficiency are important constraints of the RT used in a DFIG application. The purpose of this study is to develop a design methodology that takes into account the unique properties of the RT, while simultaneously minimising size and maximising efficiency. An analytical model, which makes provision for the non-idealities of the RT, is used to improve the analysis. The model is then verified using FEM. Although the improved model offers better correlation to the simulated results than the original model, there is still room for improvement. A prototype RT, is designed using developed procedure, constructed and practically tested. The resultant size is suitably smaller than a prototype built using standard transformer design strategies. Encouraging results are obtained from the tests, indicating that the RT performs well at the rated conditions. However, a number of differences exist between the FEM analysis and the measured operation. The cause of this deviation is discussed and suitable recommendations are made for future work.

AFRIKAANSE OPSOMMING: Die borsellose dubbel gevoed induksie generator (BDGIG) bied hoër betroubaarheid as die standaard dubbel gevoed induksie generator (DGIG), deur die verwydering van die sleepringe en borsels. Die huidige BDGIG topologie veroorsaak ’n meer komplekse masjien. Om gelyktydig die betroubaarheid van die generator te verbeter en nogsteeds die eenvoudigheid van die DGIG te behou, alternatiewe borsellose topologieë is ondersoek. Een so oplossing is om gebruik te maak van ’n roterende transformator (RT) wat die sleepringe en borsels vervang. Die RT is op die selfde skag as die generator geplaas en lewer induktiewe koppeling oor die lug gaping. Grootte en doeltreffendheid is belangrik beperkings van die RT. Die doel van hierdie studie is om ’n ontwerp metode te ontwikkel wat die unieke eienskappe van die RT in ag neem, en terselfdertyd die grootte verminder en doeltreffendheid maksimeer. ’n Analitiese model, wat voorsiening maak vir die nieidealiteite van die RT, word gebruik om die ontleding van die RT te verbeter. Die model is geverifieer behulp van FEM. Hoewel die verbeterde model bied aan ’n beter korrelasie met die gesimuleerde resultate, as die oorspronklike, die model kan nogsteeds verbeter word. ’n Prototipe RT, wat ontwerp is met behulp van die metode, is gebou en prakties getoets. Die gevolglike grootte is paslik kleiner as ’n prototipe gebou met behulp van standaard transformator ontwerp strategieë. Bemoedigende resultate word verkry uit die toets, wat aandui dat die RT presteer goed by die gegradeerde voorwaardes. Daar bly ’n aantal verskille tussen die FEM ontleding en die gemeet operasie. Die oorsaak van hierdie afwyking word bespreek en gepaste aanbevelings word gemaak vir toekomstige werk.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98414
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