A Practical Method for Building the FE-Based Phase Variable Model of Single Phase Transformers for Dynamic Simulations

摘要

A finite-element (FE)-based phase variable model of single-phase transformers is developed for fast and accurate dynamic simulation purposes. In the developed model, the winding flux linkages, $psi_{1}$ and $psi_{2}$ are used as the phase variables. Their values are obtained from a series of nonlinear FE computation over the full operating range of the transformer. An equivalent magnetizing current, $i_{rm em}$ is defined. The variation of flux linkages $psi_{1}$ and $psi_{2}$ with the defined $i_{rm em}$ and the primary current $i_{1}$ or the secondary current $i_{2}$ are used to describe the magnetization nonlinearity of the core. Our study shows that the utilization of $i_{rm em}$ enables the FE-based phase variable model has the same accuracy as the full FE model without the necessity of excessive number of FE computations. The validity of the developed FE-based circuit model is verified through comparing with the full FE model and demonstrated by simulating the inrush current and the magnetizing currents at various saturation levels.