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  • 1. Olivares-Galvan, J. C.
    et al.
    Campero-Littlewood, E.
    Hernandez-Avila, J. L.
    Escarela-Perez, R.
    Adame, S. M.
    Theocharis, Andreas
    Technol. & Educ. Inst. of Patras, Patras, Greece.
    Evaluation of stray losses in throats of distribution transformers using finite element simulation2012Ingår i: 2012 VI Andean Region International Conference, IEEE, 2012, s. 7-10Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper provides a numerical methodology to quantify the losses produced by induced currents in the metallic ducts (throats) used to enclose the bus bars connecting distribution transformers to switchgears. This calculation is important because some transformer manufacturers in Mexico don’t include throats in the load losses measurement. In particular, it presents the results of simulations made with commercial Finite-Element Software, to quantify the stray losses, originated by the induced currents, in throats of a 2000 kVA distribution transformer. The information provided by transformer’s manufacturers has been used judiciously in the creation of the numerical model. © 2012 IEEE.

  • 2. Olivares-Galván, J. C.
    et al.
    Georgilakis, P. S.
    Theocharis, Andreas
    1: Dept. de Energia, Univ. Autonoma Metropolitana-Azcapotzalco, Mexico City, Mexico .
    Madrigal, M.
    Experimental investigation of parameters influencing transformer excitation current2010Ingår i: 7th Mediterranean Conference and Exhibition on Power Generation, Transmission, Distribution and Energy Conversion (MedPower 2010), 2010, nr 572 CPKonferensbidrag (Refereegranskat)
    Abstract [en]

    This paper quantifies experimentally the impact of ten parameters on transformer excitation current. These parameters belong to the following six categories: (1) annealing process, (2) mechanical process, (3) operating conditions, (4) magnetic material, (5) assembly process, and (6) core design process parameters. The conclusions of this research are very useful during both the design and production phases of transformers. Consequently, transformers can be designed and manufactured to fulfill the excitation current specifications.

  • 3.
    Theocharis, Andreas
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Charalambakos, Vasilios
    Technological Educational Institute of Patras – Dept of Electrical Engineering.
    Pyrgioti, Eleftheria
    Peppas, George
    Laskos, G
    Modelling of breakdown and pre-breakdown phenomena in liquid dielectrics2011Ingår i: Proc. of the 17th International Symposium on High Voltage (ISH 2011), August 2011: Book of abstract / [ed] E Gockenbach, C Eichler, F Mohsen, M Fischer, O Gratz,, VDE Verlag GmbH, 2011Konferensbidrag (Refereegranskat)
  • 4.
    Theocharis, Andreas
    et al.
    Department of Electrical Engineering, Technological and Educational Institute of Patras, Patras, Greece.
    Charalampakos, V. P.
    Department of Electrical Engineering, Technological and Educational Institute of Patras, Patras, Greece.
    Drosopoulos, A.
    Department of Electrical Engineering, Technological and Educational Institute of Patras, Patras, Greece.
    Equivalent linearized circuit of photovoltaic generator appropriate for implementation in electromagnetic transient software programs2011Ingår i: 2011 10th International Conference on Environment and Electrical Engineering, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, an equivalent linearized electrical circuit of a photovoltaic generator is developed appropriate for association with electromagnetic transient packages for power systems studies which are based on nodal analysis. The proposed technique is based on published and well-tested ipv-vpv equations which are used in an alternative mathematical manner. The application of Newton-Raphson algorithm on i pv-vpv equations leads to uncoupling of the ipv and vpv quantities in each time step of a digital simulation. This is represented by a current source in parallel with a conductance. The proposed equivalent circuit is a powerful tool for power engineers who are involved in PV systems modeling since one can develop a PV generator element in electromagnetic transient programs for PV power systems studies. © 2011 IEEE.

  • 5.
    Theocharis, Andreas
    et al.
    Univ Patras, Dept Elect & Comp Engn, Patras, Greece.
    Charalampakos, V. P.
    Drosopoulos, A.
    Milias-Argitis, J.
    Equivalent circuit of photovoltaic generator using Newton-Raphson algorithm2012Ingår i: Compel, ISSN 0332-1649, Vol. 31, nr 4, s. 1224-1245Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose - The purpose of this paper is to develop a linearized equivalent electrical circuit of a photovoltaic generator. This circuit is appropriate to confront problems such as numerical instability, increased computational time and nonlinear/non-canonical form of system equations that arise when a photovoltaic system is modelled, either with differential equations or with equivalent resistive circuits that are generated by electromagnetic transient software packages for power systems studies. Design/methodology/approach - The proposed technique is based on nonlinear and well-tested ipv 2 vpv equations which are however used in an alternative mathematical manner. The application of the Newton-Raphson algorithm on the ipv 2 vpv equations leads to uncoupling of the ipv and vpv quantities in each time step of a digital simulation. This uncoupling is represented by a linearized equivalent electrical circuit. Findings - The application of nodal analysis equivalent resistive circuits using the proposed equivalent photovoltaic generator circuit leads to a system model based on linear algebraic equations. This is in opposition to the nonlinear models that normally result when a nonlinear ipv 2 vpv equation is used. In addition, using the proposed scheme, the regular systematic methods of circuit analysis are fully capable of deriving the differential equations of a photovoltaic system in standard form, thus avoiding the time-consuming solution process of nonlinear models. Originality/value - In this paper, a new method of using the ipv 2 vpv characteristic equations is proposed which remarkably simplifies photovoltaic systems modeling. Moreover, a very important practical application is that by using this methodology one can develop a photovoltaic generator element in electromagnetic transient programs for power systems analysis, of great value to power engineers who are involved in photovoltaic systems modeling. © 2012 Emerald Group Publishing Limited.

  • 6.
    Theocharis, Andreas
    et al.
    University of Patras, Greece.
    Menti, A.
    University of Patras, Greece.
    Milias-Argitis, J.
    University of Patras, Greece.
    Zacharias, Th.
    University of Patras, Greece.
    Modeling and simulation of a single-phase residential photovoltaic system2005Ingår i: Power Tech, 2005 IEEE Russia, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    A grid connected single-phase residential photovoltaic system is modeled and simulated using a detailed transformer model. The transformer model takes into account the non-linearity of the core material, which further affects the harmonic currents injected into the utility grid. Furthermore, suitable models for the photovoltaic array and the inverter have been used to assemble a system model in the field of standard form state equations. Comparison with published results has been made with a prototype installation of the same configuration. Very good agreement is accomplished between the predicted and measured values. Thus, a valid powerful tool is given for studies of such grid connected single-phase photovoltaic systems.

  • 7.
    Theocharis, Andreas
    et al.
    Department of Electrical and Computer Engineering,University of Patras,Patras,Greece.
    Milias-Argitis, J.
    Zacharias, T.
    A systematic method for the development of a three-phase transformer non-linear model2010Ingår i: International journal of circuit theory and applications, ISSN 0098-9886, E-ISSN 1097-007X, Vol. 38, nr 8, s. 797-827Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a novel three-phase transformer non-linear model is developed. The proposed model takes into account the magnetic core topology and the windings connections. The non-linear characteristic curve of the core material is introduced by its magnetization curve or by its hysteresis loop using the mathematical hysteresis model proposed by Tellinen or the macroscopic hysteresis model proposed by Jiles-Atherton. The eddy currents effects are included through non-linear resistors using Bertotti’s work. The proposed model presents several advantages. An incremental linear circuit, having the same topology with the magnetic circuit of the core, is used in order to directly write the differential equations of the magnetic part of the transformer. The matrix Ld that describes the coupling between the windings of the transformer is systematically derived. The electrical equations of the transformer can be easily written for any possible connection of the primary and secondary windings using the unconnected windings equations and transformation matrices. The proposed methods for the calculation of the coupling between the windings, the representation of the eddy currents and the inclusion of the core material characteristic curve can be used to develop a transformer model appropriate for the EMTP/ATP-type programs. Copyright © 2009 John Wiley & Sons, Ltd.

  • 8.
    Theocharis, Andreas
    et al.
    Univ Patras, Dept Elect & Comp Engn, Patras 26500, Rion, Greece..
    Milias-Argitis, J.
    Zacharias, T.
    Three-phase transformer model including magnetic hysteresis and eddy currents effects2009Ingår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 24, nr 3, s. 1284-1294Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a three-phase transformer model is developed to be suitable for slow transient and power-quality studies. The proposed model takes into account the eddy currents, the magnetic core topology, and the nonlinear characteristics of the core material. In order to model the eddy currents effects in the magnetic core, Bertotti’s work for the eddy currents is used and nonlinear resistors dependent on the magnetic core topology are proposed. A systematic procedure is developed for the determination of the incremental self and mutual inductances of the windings. The nonlinear characteristics of the core material are represented either by a magnetization curve or by a hysteresis loop. The hysteresis loop is introduced either by the mathematical model proposed by Tellinen or by the macroscopic model presented by Jiles-Atherton. Simulations results are compared to published measurements in order to verify the proposed model. © 2009 IEEE.

  • 9.
    Theocharis, Andreas
    et al.
    Department of Electrical and Computer Engineering, University of Patras, Greece.
    Milias-Argitis, J.
    Zacharias, Th.
    A dynamic model of a single-phase transformer with asymmetrical magnetic core2006Ingår i: WSEAS Transactions on Circuits and Systems, ISSN 1109-2734, E-ISSN 2224-266X, Vol. 5, nr 1, s. 39-45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dynamic model of a core-type single-phase transformer is presented in this work, which takes into account not only the non-linearity of the core material but also the geometry of the core. The model is based on the decoupling and the direct solution of the electric and the magnetic circuits. Simulation results with a non-uniform cross-section of the magnetic core are presented in comparison with simulation results with a uniform cross-section of the magnetic core. The results show a strong influence on the electrical quantities in the case of a non-uniform cross-section of the magnetic core.

  • 10.
    Theocharis, Andreas
    et al.
    Univ Patras, Dept Elect & Comp Engn, Patras 26500, Rion, Greece.
    Milias-Argitis, J.
    Zacharias, Th.
    Single-phase transformer model including magnetic hysteresis and eddy currents2008Ingår i: Electrical engineering (Berlin. Print), ISSN 0948-7921, E-ISSN 1432-0487, Vol. 90, nr 3, s. 229-241Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a single-phase core-type and shell-type transformer model is proposed on the level of state equations. The magnetic hysteresis and the eddy currents effects are successfully included based on the analytical description of the magnetic core topology. Predicted values from simulations are in very good agreement with published measurements and hence, the developed transformer model is a powerful tool for transient and steady-state studies. © 2007 Springer-Verlag.

  • 11. Theocharis, Andreas
    et al.
    Milias-Argitis, John
    Zacharias, Thomas
    A Detailed Single-Phase Core-Type Transformer Model Based on Jiles-Atherton Theory of Ferromagnetic Hysteresis2006Konferensbidrag (Refereegranskat)
  • 12.
    Theocharis, Andreas
    et al.
    Department of Electrical and Computer Engineering University of Patras.
    Milias-Argitis, John
    Zacharias, Thomas
    Analysis and Simulation of a Core-Type Single-Phase Transformer With Non-uniform Cross-section2005Konferensbidrag (Refereegranskat)
  • 13.
    Theocharis, Andreas
    et al.
    University of Patras, Patras, Greece.
    Milias-Argitis, John
    University of Patras, Patras, Greece.
    Zacharias, Thomas
    University of Patras, Patras, Greece.
    Three-phase Transformer Model for Slow Transient and Power Quality Studies2009Konferensbidrag (Refereegranskat)
  • 14.
    Theocharis, Andreas
    et al.
    Department of Electrical Sustainable Energy, Delft University of Technology, Netherlands.
    Naxakis, Ioannis
    Pyrgioti, Eleftheria
    Photovoltaic generator modeling with electromagnetic transient programs2011Konferensbidrag (Refereegranskat)
  • 15.
    Theocharis, Andreas
    et al.
    Department of Electrical Engineering, Technological and Educational, Institute of Patras, Greece.
    Olivares-Galvan, J. C.
    Departamento de Energia, Universidad Autonoma Metropolitana, Mexico City, Mexico.
    Zacharias, T.
    Department of Electrical Engineering, Technological and Educational, Institute of Patras, Greece.
    Eddy-currents modelling in transformers magnetic cores using ohmic resistances2012Ingår i: 2012 11th International Conference on Environment and Electrical Engineering, IEEE, 2012, s. 549-554Konferensbidrag (Refereegranskat)
    Abstract [en]

    The inclusion of eddy-currents effects in transformers cores is a very hot subject on transformers modeling. The dominated modeling approach is based on the usage of equivalent ohmic resistances placed in the equivalent electrical circuit which represents the electrical part of the transformer. In this paper, a comparison study, between the main different models using ohmic resistances for the eddy-currents in transformers magnetic cores, is conducted. Specifically, the selection of the suitable ohmic resistance, according to the study that is going to be conducted using an appropriate transformer model, is clarified; a topic that has not sufficiently been investigated and presented in the literature. The methods for determination of the ohmic resistances, in the simple case of a single-phase core-type transformer, are presented. Corresponding numerical results are given, which are compared to measured values if possible. © 2012 IEEE.

  • 16.
    Theocharis, Andreas
    et al.
    Delft Univ Technol, Fac EEMCS, Mekelweg 4, NL-2628 CD Delft, Netherlands.
    Popov, M.
    Delft Univ Technol, Fac EEMCS, Mekelweg 4, NL-2628 CD Delft, Netherlands.
    Modelling of foil-type transformer windings for computation of terminal impedance and internal voltage propagation2015Ingår i: IET Electric Power Applications, ISSN 1751-8660, E-ISSN 1751-8679, Vol. 9, nr 2, s. 128-137Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The goal of this work is to develop an efficient numerical model of foil-type windings. An equivalent lumped-parameter circuit model is presented, which is suitable for the computation of the terminal impedance within a broad frequency range and for internal voltage propagation studies. Owing to the special geometrical winding shape, particular attention has been paid to the calculation of the involved lumped parameters where efficient and accurate formulas for parameter determination are presented. The core influence is investigated for the broad frequency range by taking into account the frequency dependency of core material properties. Simulated results compared to measurements show that the proposed equivalent circuit in combination with the applied formulas for parameter determination can be used with full success for the computation of the terminal impedance and internal voltage distribution studies. © The Institution of Engineering and Technology 2015.

  • 17.
    Theocharis, Andreas
    et al.
    Delft Univ Technol, Fac EEMCS, NL-2628 CD Delft, Netherlands..
    Popov, M.
    Delft Univ Technol, Fac EEMCS, NL-2628 CD Delft, Netherlands..
    Seibold, R.
    Siemens AG, Power Transmiss Div Transformers, D-73230 Kirchheim Unter Teck, German.
    Voss, S.
    Siemens AG, Power Transmiss Div Transformers, D-90461 Nurnberg, Germany.
    Eiselt, M.
    Siemens AG, D-13629 Berlin, Germany.
    Analysis of switching effects of vacuum circuit breaker on dry-type foil-winding transformers validated by experiments2015Ingår i: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 30, nr 1, s. 351-359Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the prestrike and the restrike effects during switching a vacuum circuit breaker (VCB) connected to a dry-type foil-winding transformer are theoretically and experimentally analyzed. The analysis is conducted by performing a wide range of experimental three-phase switching ON/OFF tests for a 3.75-MVA prototype test transformer connected to a VCB by a cable with different lengths and for different loading conditions. A refined transformer model is successfully applied for the computation of the voltage distribution along the transformer windings. In particular, the winding properties are separately investigated, for which the core influence for frequencies above some tens of kilohertz is studied, and the terminal impedance variation for a broad frequency range is accurately calculated. The simulated results are excellent. Based on these results, an analysis was performed to evaluate the severity of the switching operations by applying spectral analysis of the recorded signals. The statistical analysis of the overvoltages with respect to the cable length and the load value shows that long cables do not guarantee lower overvoltages because of the load and its interaction with the system that makes each case unique. © 2014 IEEE.

  • 18.
    Theocharis, Andreas
    et al.
    Higher Coll Technol, Fac ETS, Nahyan 1st St,POB 17155, Al Ain, U Arab Emirates.
    Popov, M.
    Delft Univ Technol, Fac EEMCS, Mekelweg 4, NL-2628 CD Delft, Netherlands.
    Terzija, V.
    Univ Manchester, Sch Elect & Elect Engn, Manchester M13 9PL, Lancs, England.
    Computation of internal voltage distribution in transformer windings by utilizing a voltage distribution factor2016Ingår i: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 138, s. 11-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a method for the application of the black-box transformer models to the lumped-parameter transformer winding models is presented. The methodology is based on applying terminal transformer voltages as input parameters that could be provided by using the powerful black box vector fitting. Then, internal voltage distribution is determined by applying a lumped-parameter model approximation. In particular, the paper is focused on the direct computation of the internal voltage distribution, by avoiding a complicated procedure of solving the lumped-parameter winding model. The method is based on the transformation matrix utilization of the voltage distribution factors. This transformation matrix reflects the voltage distribution at specific internal points along the winding with respect to the input terminal voltages. At this stage, the inputs for the lumped-parameters model are provided by measured voltages at transformer terminals and the transformation matrix is determined through geometrical data of the transformer. The implementation of the proposed method with the black-box modeling approach in existing simulation software tools like EMTP is under development. The method is verified by comparing measured with computed waveforms. © 2016 Elsevier B.V. All rights reserved.

  • 19.
    Theocharis, Andreas
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Popov, Marjan
    Delft Univ Technol, TUDelft, Dept Elect Sustainable Energy, Delft, Netherlands.
    PV Generator Modelling in EMTP2017Ingår i: 2017 IEEE SECOND INTERNATIONAL CONFERENCE ON DC MICROGRIDS (ICDCM), IEEE, 2017, s. 400-405Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, the development of a photovoltaic generator model in EMTP is presented. The model is based on the linearization of the current-voltage nonlinear equations of a PV generator. The model is realized by using standard electrical components and MODELS language in ATP-EMTP. The operational environmental conditions are taken into account and the proposed model is suitable for transients and dynamic power systems studies.

  • 20. Theocharis, Andreas
    et al.
    Popov, Marjan
    Gustavsen, Bjorn
    An EMTP-based Analysis of Transformer Switching Overvoltages2013Konferensbidrag (Refereegranskat)
  • 21.
    Theocharis, Andreas
    et al.
    HigherCollegesofTechnology,Faculty-ETS.
    Popov, Marjan
    Terzija, Vlabimir
    Computation of internal voltage distribution in transformers windings by utilizing the voltage distribution factor2015Konferensbidrag (Refereegranskat)
  • 22.
    Theocharis, Andreas
    et al.
    Delft Univ Technol, Dept Elect Sustainable Energy, Intelligent Elect Power Grids, Mekelweg 4, NL-2628 CD Delft, Netherland.
    Pyrgioti, E. C.
    Univ Patras, Dept Elect & Comp Engn, Power Syst Sect, GR-26500 Patras, Rio, Greece.
    Development of a linearized photovoltaic generator model for simulation studies with electromagnetic transient programs2015Ingår i: International Transactions on Electrical Energy Systems, E-ISSN 2050-7038, Vol. 25, nr 3, s. 454-470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a linearized equivalent electrical circuit of a photovoltaic generator is developed. The proposed model is based on nonlinear and well-tested current-voltage equations which are however used in an alternative mathematical manner. The application of a linearization process, which differs from the well-known piecewise linear scheme and is based on Taylor’s series approximation, leads to uncoupling of the current and voltage quantities in each time step of a digital simulation. Using the proposed equivalent photovoltaic generator circuit, the application of nodal analysis on equivalent resistive circuits derives a photovoltaic system model of linear algebraic equations. This remarkably simplifies photovoltaic systems modeling because one can develop a photovoltaic generator element in electromagnetic transient programs for power systems analysis, of great value to power engineers who are involved in photovoltaic systems modeling. Copyright © 2014 John Wiley & Sons, Ltd.

  • 23. Theocharis, Andreas
    et al.
    Pyrgioti, E. C.
    Electromagnetic transient programs and the photovoltaic input2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a linearized equivalent electrical circuit of a photovoltaic generator is developed. The application of a linearization process, which differs from the well-known piecewise linear approximation and is based on Taylor’s series scheme, leads to uncoupling of the current and voltage quantities. This uncoupling is represented by a equivalent electrical circuit. Using the proposed equivalent photovoltaic generator circuit, the photovoltaic systems modeling is remarkably simplified. This is because one can develop a photovoltaic generator element in electromagnetic transient programs for photovoltaic power systems transient analysis. © 2013 IEEE.

  • 24.
    Theocharis, Andreas
    et al.
    Department of Electrical and Computer Engineering University of Patras .
    Pyrgioti, Eleftheria
    Naxakis, Ioannis
    Modelling of Photovoltaic Generators Based on a Linearized Equivalent Circuit2012Konferensbidrag (Refereegranskat)
  • 25.
    Theocharis, Andreas
    et al.
    University of Patras, Department of Electrical and Computer Engineering, 26500 Rion, Greece.
    Tzinevrakis, A.
    Charalampakos, V.
    Milias-Argitis, J.
    Zacharias, Th.
    Transformer modeling based on incremental reluctances2010Ingår i: Conference Proceeding 2010 International Conference on Power System Technology: Technological Innovations Making Power Grid Smarter, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper is the completion of a previous work, published recently, on transformer modeling where the magnetic core topology is taken into account. A new circuit, that represents the magnetic core, is proposed, more easily handled mathematically in antithesis to the conventional magnetic circuit that is used in the literature. The proposed circuit has the same topology with the nonlinear magnetic circuit of the core and, in each time interval of a dynamic simulation, it is considered as linear circuit. Its excitations and responses are the time derivatives of both the magnetomotive forces and the magnetic fluxes, respectively. This modeling approach helps power engineers to construct easily a nonlinear transformer model. Applying any method of circuit analysis on the proposed circuit, one can directly write linear differential equations, in each time interval Δt, for the magnetic core and the state equations of the electrical part are written in standard form. ©2010 IEEE.

  • 26.
    Theocharis, Andreas
    et al.
    Department of Electrical EngineeringTechnological Educational Institute of PatrasPatrasGreece.
    Tzinevrakis, A. E.
    Department of Electrical and Computer EngineeringUniversity of PatrasPatrasGreec.
    Charalampakos, V. P.
    Department of Electrical EngineeringTechnological Educational Institute of PatrasPatrasGreece.
    Milias-Argitis, J.
    Department of Electrical and Computer EngineeringUniversity of PatrasPatrasGreec.
    Zacharias, T.
    Department of Electrical and Computer EngineeringUniversity of PatrasPatrasGreec.
    Development of a nonlinear geometric transformer model based on an incremental circuit of its magnetic core2012Ingår i: Electrical engineering (Berlin. Print), ISSN 0948-7921, E-ISSN 1432-0487, Vol. 94, nr 4, s. 217-232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the investigation is focused on the topology-based geometric models of power transformers. These models take into account any type of core design, the geometrical characteristics of the magnetic core, and the nonlinear characteristics of the core material. These models differ from each other in the way in which the magnetic part is described. Themethods, which have been proposed for the description of the magnetic part of a power transformer, are based on the conventional magnetic circuit of the core and present disadvantages. In this paper, a new method for the derivation of the differential equations of the magnetic core of the transformer is proposed by introducing a newauxiliary incremental circuit, more easily handled mathematically in antithesis to the conventional magnetic circuit that is used in the literature until now. Specifically, using the proposed circuit one can directly write the differential equations of the magnetic part of the transformer, the coupling between the windings of the transformer is easily calculated, the equations of the electric and the magnetic part are decoupled as well as the state equations of the electrical part can be written in standard form. The proposed method can be combined with anymethodology presented in the literature on the core losses modeling without any restriction. The simulation results show forth that the proposed method of transformer modeling is suitable for transients and power quality studies. Moreover, the proposed method can be a useful tool on sensitivity analysis during the design stage of small and large power transformers as well. © Springer-Verlag 2012.

  • 27.
    Theocharis, Andreas
    et al.
    University of Patras, Patras, Greece.
    Zacharias, Thomas
    University of Patras, Patras, Greece.
    Tsanakas, Dimitrios
    University of Patras, Patras, Greece.
    Milias-Argitis, John
    University of Patras, Patras, Greece.
    Μodeling of a Grid Connected Photovoltaic System Using a Geometrical Transformer Model2009Ingår i: Zeszyty Problemowe – Maszyny Elektryczne, Katowice: Komel , 2009, Vol. 84Konferensbidrag (Refereegranskat)
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