New State-Space White-Box Transformer Model for the Calculation of Electromagnetic Transients

Mombello, Enrique E.; Portillo, Álvaro; Díaz, Guillermo

doi:10.1109/tpwrd.2020.3023824

Cited by 8 publications

(7 citation statements)

References 33 publications

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“…Eq. ( 13) and (11a) are combined into a single state-space equation (14a) [14]. The output is given by (14b) where (12b) has been used for the lower partitioning.…”

Section: State-space Modelingmentioning

confidence: 99%

“…. Such impedance matrix can be subjected to state-space modeling via a passive rational function approximation, and be introduced in the k-factor model, leading to a complete frequency-dependent state-space model of the transformer [14]. The procedure in [14] achieves this by fitting a pole-residue model approximation to ( ) B s Z by vector fitting (VF) [15].…”

mentioning

confidence: 99%

“…Such impedance matrix can be subjected to state-space modeling via a passive rational function approximation, and be introduced in the k-factor model, leading to a complete frequency-dependent state-space model of the transformer [14]. The procedure in [14] achieves this by fitting a pole-residue model approximation to ( ) B s Z by vector fitting (VF) [15]. Passivity is ensured by a modification to the model by enforcing positive definiteness for a set of matrices obtained from the rational model of ( ) B s Z , using particle swarm optimization.…”

mentioning

confidence: 99%

“…Passivity is ensured by a modification to the model by enforcing positive definiteness for a set of matrices obtained from the rational model of ( ) B s Z , using particle swarm optimization. The present work introduces two alternative approaches to the one in [14] which are conceptually simpler and more efficient. The first one fits a pole-residue model to B Z in the phase domain, using poles that are obtained by fitting approximate eigenvalues using a common pole set.…”

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confidence: 99%

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Rational Function Approximation of Transformer Branch Impedance Matrix for Frequency-Dependent White-Box Modeling

Gustavsen

2023

IEEE Trans. Power Delivery

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Transformer white-box models are used by the manufacturers to calculate internal winding voltages during the lightning impulse test. The model can also be applied in general network studies, but the model accuracy should then be improved, considering the many different voltage waveforms and frequencies that can exist in the system. Accuracy improvements are achievable by including the frequency-dependency of the branch impedance matrix via rational function approximation, but the large size of the matrix makes such modeling very difficult. Two suitable methods for passive rational modeling are presented, based on vector fitting and residue perturbation in either phase domain or modal domain. Application to a power transformer shows that the two methods are capable of fitting a 213×213 branch impedance matrix with a 6 th order passive pole-residue model in a few seconds. The resulting model is included in a complete white-box state-space model of the transformer that is compatible with a previously implemented model interface for EMTP. An efficient procedure is presented for validating the simulation result by the Numerical Laplace Transform. Comparison with a measurement shows that the inclusion of the frequency dependency gives a better reproduction of the measured waveshape than a previously proposed damping-factor model.

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“…Eq. ( 13) and (11a) are combined into a single state-space equation (14a) [14]. The output is given by (14b) where (12b) has been used for the lower partitioning.…”

Section: State-space Modelingmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Rational Function Approximation of Transformer Branch Impedance Matrix for Frequency-Dependent White-Box Modeling

Gustavsen

2023

IEEE Trans. Power Delivery

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“…by a so-called white box model [3]. Such models are usually calculated based on spatial discretization of the transformer windings, yielding a ladder-type RLCG network which can be cast as a state-space model for efficient inclusion in EMT simulation programs [4], [5]. White-box models can in practice only be created by the Manuscript received… This work was supported by the consortium participants of the SINTEF-led projects "ProTrafo" (project no.…”

Section: Introductionmentioning

confidence: 99%

Inclusion of Neutral Points in Measurement-Based Frequency-Dependent Transformer Model

Gustavsen

2022

IEEE Trans. Power Delivery

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Measurement-based wide-band black-box transformer models are well suited for simulation studies of highfrequency transients in power systems. The inclusion of neutral points in such models can be difficult when the model is required to simulate voltage transfer to windings with high-impedance loads. The difficulty arises because it is then necessary to include the small winding capacitive currents in the measurement and model extraction procedure, while at the same time the capacitances can be asymmetrical with respect to the winding ends. This paper introduces a new measurement procedure which can accurately capture the effect of such capacitive asymmetries. The procedure is demonstrated for a wye-wye connected transformer. The measurement and subsequent passive rational modeling results in two alternative models. The first is a fourterminal model with bonded high-voltage and low-voltage terminals, suitable for simulation of lightning overvoltages in distribution systems. The second is a full eight-terminal model, suitable for general purpose transient studies.

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Transformer Design Using Advanced Methods

Portillo

2022

Transformer and Reactor Procurement

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New State-Space White-Box Transformer Model for the Calculation of Electromagnetic Transients

Cited by 8 publications

References 33 publications

Rational Function Approximation of Transformer Branch Impedance Matrix for Frequency-Dependent White-Box Modeling

Rational Function Approximation of Transformer Branch Impedance Matrix for Frequency-Dependent White-Box Modeling

Inclusion of Neutral Points in Measurement-Based Frequency-Dependent Transformer Model

Transformer Design Using Advanced Methods

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