Duality-Based Potential Transformer Model Including Black-Box Circuit for High-Frequency Transient Simulation

Abstract

The precise transformer modeling is of significant importance for the analysis and simulation of transient overvoltage. This paper proposes an improved hybrid transformer model combining nonlinear and frequency-dependent effects and the parameters determination methods. The duality-based transformer model is employed to describe the low-frequency characteristics of the hybrid model by the direct application of the principle of duality. The model parameters are obtained considering the variations of the transformer electromagnetic behaviours under various operating conditions. The black-box model is utilized to describe the high-frequency characteristics of the hybrid model. The black-box modeling methodology is based on the transfer function, which is derived from the two-port test data at the transformer terminals. The model parameters are approximated by the vector-fitting method, which is used in this paper to fit the transfer function by rational functions consisting of real as well as complex conjugate poles and residues. The hybrid model is developed by the merging of the dual transformer model and the black-box circuit model by the filters. The hybrid model is validated with experimental data of the 10-kV potential transformer on the inrush current, the harmonic voltage, and the lightning excitation, respectively. There is a good agreement between the measurement results and the simulation results of the voltage on the secondary side. The hybrid model proposed in this paper is meaningful for the overvoltage analysis in power systems.