Research On Inrush Current Of Transformer Based On Residual Flux Prediction

At the closed time,the transformer core is saturated by the influence of residual flux and bias.This causes the transformer excitation current to surge,which is the phenomenon of inrush current.Therefore,the research on inrush current has been paid much attention by scholars for many years.The magnitude of the inrush current is mainly affected by the two factors of the closing angle and the remanence.Therefore,the development of the suppression technology of the inrush current is also considered as a breakthrough by considering the two factors of the closing angle and the remanence.With the rapid development of power electronics technology,the inrush current suppression technology of phase selection and closing by selecting the closing angle has been proposed by scholars.However,the study of residual flux is still limited by experimental methods and equipment.At present,there is no method for directly measuring residual flux.Therefore,the mathematical model is used to predict the residual flux.The analysis and discussion of the inrush current has important research significance and engineering value in the suppression of inrush current.The main body of this paper is divided into two parts: one is to predict the residual flux of the transformer,the Preisach mathematical model is established and experimental verification is carried out;the other part is about the simulation research and experimental analysis of the inrush current.The main research contents are as follows:Firstly,by analyzing the mechanism of the inrush current,the importance of residual flux to the study of inrush current is described.Then,through the study of the hysteresis characteristics of ferromagnetic materials,the causes of residual flux are discussed.Then,based on the hysteresis characteristics of ferromagnetic materials,the classical Preisach mathematical model is improved,and the Preettach mathematical model based on magnetic permeability calculation is established by using the Everett distribution function method,and the residual flux prediction is performed accordingly.Afterwards,the magnetic hysteresis loop of the silicon steel sheet under different excitations was experimentally measured,and the Preisach model was verified and proved.The feasibility of calculating the Preisach model based on magnetic permeability was proved.Finally,due to the indirect measurement of residual flux,this paper uses the simulation of the inrush current waveform and the simulated inrush current simulation waveform after remanence,to verify the accuracy of residual flux prediction.Using the closing experiment under load conditions,the simulation model was built in Matlab/Simulink for comparison and verification,and the current characteristics of the inrush current were obtained.Finally,the feasibility of using the Preisach mathematical model for residual flux prediction is verified.