The Research Of The Broadband Nonlinear Transformer Model Based On A10kV Transformer

The transformer model is one of the most needed improving components ofmodern transient simulation software. Not only the transformer is essential inpower system, but also some of the transformer parameters are both nonlinear andfrequency dependent. The simulation models which are valid for a wide frequencyrange are rarely available. Therefore, it is necessary to establish a new broadbandnonlinear transformer model.Based on the study of transformer structure, a new nonlinear broadbandmodel of power transformer is proposed in this paper for steady state till severalmegahertz. Firstly, this article describes the basic principles of the transformer,including the frequency dependent electromagnetic phenomena, saturablecomponents and parameter measurements. Secondly, the circuit which consists ofa linear module and a nonlinear module is derived by the analysis of the basicstructure of the transformer. The linear parameters are measured by networkanalyzer. Based on the black box method, the linear module is established bymodified vector fitting and circuit synthesis. For the nonlinear module, theadmittance is derived by mathematical calculations of the silicon steel. A linearcircuit for iron core is established by modified vector fitting. Then the nonlinearinductance is added to the circuit.The simulations and experiments are studied on a10kV two-windingtransformer. Based on the above methods, a Simulink model is constructed forsimulation. To verify the model, the experiments of power frequency steady state,power frequency overvoltage and lightning overvoltage are conducted. Thecomparisons between the simulation and measurement results verify the feasibilityand validity of the model.