Research On Experiment And Calculation About Excitation-Vibration-Noise Characteristics Of Transformer Under Interharmonic Excitation

With the proposal of the strategic goal of carbon peaking and carbon neutralization,renewable energy and AC / DC transmission technology are widely used,more and more power electronic equipment are used to construct new power systems,which not only brings immense economic benefits to the society,but also creats the problem of interharmonic pollution that should be pay attention to.Under the condition of interharmonic excitation,the excitation characteristics,vibration characteristics and noise characteristics of power transformer will change greatly compared with those under power frequency conditions,which could endanger the safe and stable operation of the equipment and even the power grid.Therefore,it is of great theoretical and practical significance to study the operation characteristics of transformers under interharmonic conditions.Firstly,the magnetization and magnetostriction characteristics of oriented electrical steel sheets are measured accurately based on a set of laser magnetostrictive measurement systems,which compared B-H curves and magnetostrictive butterfly curves in different rolling directions,and the characteristic curves of magnetostrictive strain peak and magnetic field are fitted based on the empirical formula of magnetostriction,which provides data basis for the numerical calculation of vibration and noise of the equipment core.Secondly,an experimental platform for transformer excitation and core vibration noise characteristics with arbitrary interharmonic excitation is established.The transformer core excitation current,vibration displacement and sound pressure level of near field noise under power frequency and interharmonic excitation are measured.Then the influence of interharmonic frequency on the performance of cores is studied.The occurrence of other interharmonic frequencies in the analysis of excitation current and vibration displacement spectrum with single frequency interharmonic excitation is analyzed,and the distribution of sound pressure level in the frequency doubling band of core noise is summarized.Finally,based on the measured magnetic characteristics data,a three-dimensional finite element model of transformer core circuit-magnetic-mechanical-sound field coupling is established to explore the excitation characteristics,electromagnetic vibration and sound field distribution of transformer under interharmonic conditions.Quantitative calculation results of core excitation,sound field and vibration are obtained by calculation.The calculation results are compared with the experimental measurement results in time domains and frequency domains.The validity of the numerical multi field calculation model is verified,which can provide reference for the study of related characteristics of transformer core.