Study On The Practical Application Of The Transformer Model For Three Phase Power Flow In Distribution Network

The most basic and most important calculation of power system is power flow.The application of three-phase power flow in distribution network is more and more extensive.When the power flow analysis of the distribution network is carried out,the characteristics of three-phase asymmetry should be considered.Whether the transformer model is set up properly,it will have a great impact on the convergence,the complexity and accuracy of the power flow calculation.The transformer has a variety of winding connection modes,when the connection mode of the transformer is not the same,the node admittance matrix of the transformer is not the same.In practical application,it is necessary to analyse and deduce the connection modes of each winding.To realize the automatic derivation and visualization of the admittance matrix of the transformer node is of great significance in the field of engineering application.As an important electrical equipment in the power system,the transformer model has become an important part of the analysis for the distribution network.Analysing the influence of different magnetic circuit structure on the transformer asymmetrical operation,Establishing the mathematical model of the three-phase transformer based on the characteristic of the magnetic circuit,and its equivalent circuit is determined.The accurate model,simplified model and practical model of power distribution transformer are established.Based on the practical model of transformer,by using the correlation matrix method,by the original admittance matrix and the actual transformer connection group can get the node admittance matrix of transformer.In the sequence network of transformer,according to the relationship between the sequence voltage and current of the transformer,the admittance matrix of the ordered network node is obtained,the node admittance matrix of the transformer is derived by using the symmetrical component method.The hand-calculation of admittance matrix is tedious,consuming and error-prone.Available information on the node admittance matrix is not complete,only part connection group derived result is given,which bring great inconvenience in engineering application.Therefore,Matlab symbolic operation is used to automatically derive the admittance matrix of the transformer node,LaTeX language can be used to set the mathematical formula and beautifully displayed,first,the symbolic expression is converted into LaTeX format,then in the GUI Matlab visualization interface,the transformer node admittance matrix can be displayed visually and vividly.