Low-frequency model for single-phase transformers based on the three-component Preisach model considering deep saturation

The transformer model is very important for the transient simulations of power systems. Although a large number of researches have been carried out on the developments and applications of the transformer model, there are still some deficiencies in the study, such as hysteresis and frequency-dependence. This paper proposes an improved transformer model for the calculation of low-frequency transients in power systems. The magnetizing branches are simulated by the composite curves with hysteresis part and deep saturation part. The expression of the inverse static I-Phi Preisach model (ISPM) is derived from the classical Preisach model (CPM). The Preisach distribution function (PDF) is determined by the centered cycles method. Based on the dynamic performance of the grain-oriented electrical steel, the inverse dynamic Preisach model (IDPM) with three components is proposed. The deep saturation inductance can be obtained from the modified AC plus DC test. Then, the modified dual reversible model of the single-phase transformer is developed in ATP-EMTP. At last, the ISPM and IDPM are validated by the comparison of the measured and simulated loops. The steady-state and transient performances of the proposed transformer model are also validated by the comparison of the experiments with simulations including no-load test, DC bias test, and inrush current test.