Modeling And Validation Of Structural Components Loss Under Multi-harmonic Excitation

In recent years,electric power demand of our country is growing rapidly,as energy resources are spread unevenly across the country,power transmission and transformation technology in UHV(ultra high voltage)get the major development.In UHVDC(ultra high voltage direct current),large of harmonic generated from rectifiers in operation,harmonic current flow into converter transformer and smoothing reactor,it makes the loss of windings increase.Because of the effect of harmonic leakage magnetic field,higher-order harmonic loss increases in structural components.It affects the temperature rise seriously and may result in partial local overheating.It has bad effects to the normal operation of transformer.In this paper,based on TEAM(Testing Electromagnetic Analysis Methods)Problem 21 Benchmark model and Mag Net software,an improved method which is used for measure stray-field loss is proposed.The properties of stray-field loss in transformer structure components is modeled and validated under harmonic excitations.The main contents of this thesis are as follows:(1)Measuring methods about stray-field loss of structures in TEAM P21 model are studied and existing problems are analyzed.Based on experiment results and calculating results of exciting coils loss,an improved method of measuring loss is proposed and it can consider the loss difference of coils when structures exist or not.The validity of this method is verified under power frequency.(2)An experimental platform is built which is used to research the stray-field loss under harmonic excitations.Based on simplified TEAM P21C-EM1 model,the validity of the method proposed in this paper is verified under sine and not power frequency excitations,when the structural component is non-magnetic material.The eddy-current loss of copper shield under harmonic excitations is modeled and simulated.(3)Based on simplified TEAM P21C-M1 model,the validity of the method proposed in this paper is verified under sine and not power frequency excitations,when the structural component is magnetic material.Equivalent homogenized method to magnetic permeability and conductivity in simulation is analyzed.Bulk is set up.Additional loss in silicon lamination caused by the leakage flux normal is studied under harmonic excitations.The distribution of of loss and flux is analyzed.(4)Stray-field loss and flux distribution inside magnetic steel plate under harmonic excitations.Under mixed excitations,the effect to stray-field loss caused by harmonic order,harmonic phase difference and harmonic content is studied.The averaged magnetic flux density inside steel plate is measured and analyzed.Based on simulationresults in Mag Net,the numeric of magnetic flux in different depth is extracted and the skin effect is analyzed.The wok in this paper is meaningful to the study of stray-field loss of transformer under harmonic excitations,it can provide a basis for the design and optimization of electromagnetic devices and shields.