Research On Wideband Modeling Method Of Power Transformer Considering The Nonlinearity Of The Core

Power transformer as the key equipment in power system,it is needed to ensure its reliable and safe operation.To accurately analyze the operating characteristics of the transformer in transient over-voltage,it is necessary to establish a transformer model for simulation study.The simulation model of current transformer can seldom considering the effect of frequency dependent and nonlinear characteristic of iron core,so the establishment of a core considering the nonlinear effect of broadband transformer model has important theoretical significance and practical application value.In this paper,the transformer broadband modeling method considering the core nonlinearity is studied.Starting from the T-type equivalent circuit of the transformer,a black-box model considering the wide-band characteristics of the transformer is connected in parallel,and a broadband nonlinear parallel expansion model.First,the T-type equivalent circuit of the power frequency is established by transformer no-load test and short-circuit test.Secondly,the spectral impedance analyzer is used to measure the scattering parameters,transform the wide-band admittance parameters in the range of 50Hz-5MHz,and the traditional equivalent circuit admittance is used to obtain the black box model admittance parameter.The improved vector matching method is used to fit the admittance parameter rational function,and then the equivalent circuit of the black box model is established through the network.Using the signal generator,precision power amplifier,precision power analyzer to obtain no-load UI curve,converted to core flux-current characteristic curve,the curve fitting to complete the nonlinear inductor modeling,linear inductor instead of linear Inductance to obtain the equivalent circuit model of the whole;Finally,Epstein Frame and product-grade silicon steel lap composed of single-phase dual-winding transformer model for the experimental study,the use of lightning surge generator analog operation wave,Experiment,through the power frequency,the harmonic wave,the operation wave,the lightning wave experiment and the simulation contrast,has carried on the confirmation to this article modeling method validity.