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Highlights • The Preisach model denoted by I - Φ is determined by the centered cycles method. • The combination of the Preisach model and the three-component model is proposed. • The composite curve with hysteresis part and deep saturation part is proposed. • The inverse dynamic Preisach model is implemented in ATP-EMTP. • The transformer model can simulate the dynamic magnetization and deep saturation. Abstract 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 - Φ 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. [ABSTRACT FROM AUTHOR]

This paper proposes an improved centered cycle method for identifying the Preisach distribution function based on the non-uniform discretization. The principle and the limits of the centered cycle method are first introduced. Then, the non-uniform discretization method is proposed based on the curvature of the anhysteretic magnetization curve. The numbers of loops for identifying the distribution function are decided by the proportion of the integral of curvature. The method to determine the cell values of the non-uniformly discrete Preisach triangle is also introduced. The proposed method is validated by the laboratory test of a toroidal sample. The results show the higher precision of the proposed method for predicting the hysteresis loop than the centered cycle method by the same number of loops used for identifying. [ABSTRACT FROM AUTHOR]

Despite remarkable achievements in the field of Jiles–Atherton (JA) hysteresis theory, JA hysteresis modeling remains challenging given that most commercial software still lacks a practical dynamic JA hysteresis reactor model for electromagnetic transients. A novel voltage-driven dynamic flux linkage–current ( ψ–i ) JA hysteresis reactor in Electromagnetic Transients Program–Alternative Transients Program (EMTP–ATP) is developed in this study. The proposed model is based on flux linkage and current instead of magnetic flux density and magnetic field. Voltage-driven dynamic losses are incorporated into the static ψ–i JA hysteresis model by using Type-94 element in EMTP–ATP. The two proposed models in this paper are validated using current tests under 50 and 150 Hz. The performance of the proposed dynamic Model 1 matches better with experiments than the dynamic Model 2. Ferroresonance tests are carried out to validate the performance of the proposed reactor. The results show that the proposed reactor has a broad application prospect in electromagnetic transient studies. [ABSTRACT FROM AUTHOR]

Amorphous alloy is increasingly widely used in the iron core of power transformer due to its excellent low loss performance. However, its potential harm to the power system is not fully studied during the electromagnetic transients of the transformer. This study develops a simulation model to analyze the effect of transformer iron core materials on ferroresonance. The model is based on the transformer π equivalent circuit. The flux linkage–current (ψ–i) Jiles–Atherton reactor is developed in an Electromagnetic Transients Program-Alternative Transients Program and is used to represent the magnetizing branches of the transformer model. Two ferroresonance cases are studied to compare the performance of grain-oriented Si-steel and amorphous alloy cores. The ferroresonance overvoltage and overcurrent are discussed under different system parameters. Results show that amorphous alloy transformer generates higher voltage and current than those of grain-oriented Si-steel transformer and significantly harms the power system safety. [ABSTRACT FROM AUTHOR]

• Method for describing the gradually quicker saturation process of the transformer core; • Approach to compute λ-i data points by several measured magnetizing inductances; • Modified dual reversible model considering the gradually quicker saturation process; • The proposed model can accurately predict the first peak of inrush current. The major nonlinear effects in the transformer core are saturation and hysteresis, in which saturation is the predominant effect for the transients involving saturation of transformers. A detailed representation of the saturation of the core is required. However, the available methods seldom provided experimental methods to represent the transients of the two magnetizing curves of the duality-based transformer model from slight saturation to deep saturation. This paper proposes a method to retrofitting the dual reversible transformer model with the gradually quicker saturation process of the core. Methods are proposed to measure the incremental inductances of the saturated core and using them to compute flux–current data of magnetizing branches of the proposed dual reversible π model. The entire magnetization curve is obtained by combining the unsaturated region by the available methods with the saturated region determined using the proposed methods. A single-phase two-winding transformer with a rated capacity of 500 VA is used to perform the proposed method to extract the required parameters of the proposed dual reversible transformer model. Inrush current tests are carried out and compared with simulations using ATP-EMTP to validate the model. Results show that the proposed model has better accuracy to simulate the first peak of the inrush current compared with the available model, contributing to the simulation involving low-frequency electromagnetic transients. [ABSTRACT FROM AUTHOR]