Wideband modelling and parameter estimation of two-winding transformers

[摘要] ENGLISH ABSTRACT:This dissertation proposes a new wideband, lumped-parameter equivalent-circuit transformermodel that is suitable for parameter estimation applications, while reflecting the internalelectromagnetic behaviour of the transformer in its structure. Frequency-dependenceof the resistive and inductive model elements is investigated experimentally and provisionis made for these effects in the model structure. A procedure by which the parameters ofthe proposed model structure can be estimated directly from terminal frequency responsemeasurements is developed and applied to a 16 k VA, 22 kV / 220 V single-phase distri butiontransformer and a 11kV/110 V single-phase voltage transformer. The transformermodel is validated by applying it to frequency-domain and time- domain simulations inthe frequency range between 10 Hz and 100 kHz. The results show that the proposedmodel is able to accurately predict transformer responses in this frequency range, includingall prominent winding resonances. The physical significance of the model structureis validated by comparing the frequency response of the voltage induced in a search coilaround the core of the 11 kV / 110 V voltage transformer to the magnetizing branch voltagepredicted by the model. From this comparison it could be concluded that the proposedtransformer model correctly represents the magnetic coupling between the transformerwindings.Keywords: Transformer, Wideband modelling, Parameter estimation

[发布机构] Stellenbosch University