High-Frequency Modeling of Three-Phase Transformers Considering Inter-Phase and Capacitive Coupling Based on Enhanced Magnetic Circuit

The high-frequency harmonics in the power grid have significantly increased, necessitating the construction of equivalent circuit models for large power transformers under the influence of high-frequency harmonics. High-frequency models are typically obtained by adding parasitic capacitances to the ports of conventional models. However, the influence of capacitances is only reflected in the calculation of equivalent circuit topologies, rather than in the nonlinear analysis process of inductances. This paper inverses a magnetic circuit model incorporating capacitances, based on the conventional transformer equivalent circuit model with capacitances added at the ports. Subsequently, a time-domain simulation program for the inverted magnetic circuit model is developed using C++ language. The program realizes the collaborative calculation of magnetic circuit parameters derived from capacitance inversion and reluctance parameters. The accuracy of the proposed three-phase high-frequency model is validated through no-load tests on a three-phase transformer prototype. The simulation results obtained from the improved model are compared with those from finite element method simulations as well as conventional models. The improved high-frequency model can more accurately describe the electromagnetic transient process of transformers in the presence of high-frequency harmonics.