Research On Parameters Distortion Characteristics And Loss Of Transformer Under Harmonic Background

In recent years,the connection of power electronic load and a large number of new energy grid-connected power generation equipment have injected a large amount of harmonics into the power grid.When harmonics flow through the transformer,a large amount of harmonic loss will be generated,certain economic losses.will be brought,the transmission efficiency and utilization rate of the transformer will be reduced.and the operational safety of the system will be reduced.Therefore,quantitative research on harmonic loss of transformers is of great significance.At present,there is a lack of reference quantitative analysis for harmonics.The main research method is to replace the AC resistance by multiplying the DC resistance by a constant to calculate each harmonic loss under each harmonic condition.In the case of high-frequency harmonics,the AC resistance of the transformer winding is much larger than that of the DC resistance and the parameter distortion is obvious.It is not accurate to calculate the harmonic loss by using this method.The influence of harmonics on transformer parameters and losses can be studied.Firstly,based on the electromagnetic field theory,the skin effect and proximity effect in the transformer winding under harmonic conditions are analyzed.The current density distribution in the winding and the eddy current loss effect of the leakage magnetic field are analyzed.The distortion characteristics of the transformer parameters are studied and the quantitative model of the winding harmonic loss is established.Quantification of system harmonic loss,establishment and improvement of equipment harmonic loss model are the basis of further harmonic control.After that,the simplified two-dimensional model of the leakage magnetic field of the transformer is established by ANSYS finite element method.The distribution of the leakage magnetic field of the transformer winding under harmonics is analyzed,and then the eddy current distribution under each harmonic current is analyzed.Further,the harmonic eddy current loss of the winding under different harmonic conditions is obtained.The mutual verification of the eddy current loss of each w inding of the finite element simulation and theoretical calculation is realized.Finally,based on theoretical calculation model of transformer harmonic loss,the experimental platform is established to test the winding resistance under each harmonic current and the mutual verification between the theoretical calculation model and the experimental measurement is realized.By fitting the characteristics of the AC resistance under the harmonic background and combining with the experimental measurement data,the engineering practical model of the harmonic resistance of the transformer winding is established and the applicable scope of the model is analyzed.The practical model has certain guiding value for engineering calculation.The harmonic loss of the transformer can be quickly and efficiently calculated by using this engineering practical model in the system under the premise of meeting the engineering precision requirements.It provides theoretical support for the calculation of energy saving of power grid harmonic control engineering and the construction of laboratory physical simulation model.