Atp Hibryd Model

Implementation and verification of the Hybrid Transformer model in ATPDraw
Hans K. Høidalen, Bruce A. Mork, Francisco Gonzalez, Dmitry Ishchenko, Nicola Chiesa
Abstract-- The paper documents a new transformer model in ATPDraw called XFMR. This model handles 3-phase transformers with two or three windings. Autotransformers and all Wye and Delta couplings are supported. The model includes aninverse inductance matrix for the leakage description, optional frequency dependent winding resistance, capacitive coupling, and a topologically correct core model (3- and 5-legged) with individual saturation and losses in legs and yokes. Three different sources of data are supported; typical values, standard test reports, and design information. The hybrid model XFMR is compared to the UMEC model inPSCAD showing good agreement at rated, stationary operation, but considerable differences in transient situations. Both models need development to reproduce all switching transient behaviors properly. Keywords: Transformer modeling, saturation, leakage inductance, winding resistance, capacitance, topologically correct core.
CHA-Xa/2 6 NH:NX A RH( f )
HA-HB/2

CH-GND/2 CHA-HB/2 CH-GND/2CHB-HC/2 CH-GND/2

L3 L4 Zy L3 Zy Zl

NX:NX RX( f ) ’ NX:NX Zl RX( f ) ’ NX:NX

a a’ b b’ c RX( f )

CX-GND/2

A’ C B B’ C

NH:NX RH( f ) CHB-HC/2 NH:NX RH( f )

L4 L3

Zl

’

CH-GND/2

C’

c’ CX-GND/2

Fig. 1. Electric model of the Hybrid Transformer [4], 2-windings (H and X), 3-phases, 3-legged core.

HE transformer is an essential component in power systems but the standardmodels used to represent it in transient analysis are rather poor. Several approaches are documented in the literature [1] and this paper focuses on models with topologically correct cores. A model called the Hybrid Transformer model [2]-[4] is recently implemented in ATPDraw and is there called XFMR. The characteristics and implementation of this model is outlined in this paper and its responseis compared to the UMEC model [5], [6] found in PSCAD. UMEC is chosen since it is based on similar core geometry data as XFMR. The purpose is not to show which model is the best but rather to point out the need for improved transformer models for switching transient studies. II. MODELING The modeling of the transformer is based on the magnetic circuit transformed to its electric dual [2], [3]. Theleakage and main fluxes are then separated into a core model for the main flux and an inverse inductance matrix for the leakage flux. The copper losses and coil capacitances are added at the terminals of the transformer. The resulting electrical circuit is shown in Fig. 1. Only standard EMTP elements are used.
This work has received financial support from Bonneville Power Administration, theSpanish Secretary of State of Education and Universities, the Fulbright, the Norwegian Research Council, and SINTEF Energy Research. H. K. Høidalen and N. Chiesa are with the Norwegian University of Science and Technology, Trondheim-Norway, B. A. Mork, F. Gonzalez, and D. Ishchenko are with Michigan Technological University, Houghton-USA, (e-mail of corresponding authors:hans.hoidalen@elkraft.ntnu.no, bamork@mtu.edu). Presented at the International Conference on Power Systems Transients (IPST’07) in Lyon, France on June 4-7, 2007

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I. INTRODUCTION

Modeling of the transformer can be based on three different data sources; typical values, test report, and design information. The three sources can be selected independently for resistance, inductance, capacitance, and core. Test reportinput is based on standard open and short circuits tests, with capacitance measurements as an additional option. This is the normal choice of data source for existing transformers. Design data requires the geometry and material parameters of the windings and the core. Such data are rarely available so this option is more for research purposes. The Typical value option uses available text book...