Nonlinear Transformer Model for Circuit Simulation (original) (raw)
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A Single-Phase Two-Winding Transformer Dynamic Model for Circuit Simulators
2015
Transformers are magnetic components widely used in switched-mode power electronics systems. The non-linear hysteresis behavior of the magnetic material and the high frequency effects in both core and windings have significant effects on system's efficiency, reliability and power losses. This behavior can be modeled using simple fast models or complex accurate models in order to predict and improve the transformer behavior before realization. This paper is summarized by proposing a non-linear dynamic model of transformers for use in circuit simulators. This model allows winding and core modeling including the material's accurate nonlinear dynamic hysteresis behavior. The magnetic component model is implemented in the circuit simulation software " Simplorer " using VHDL-AMS modeling language. It is validated for a medium-frequency nanocrystalline core transformer. Effects of frequency and waveform on computed efficiencies are discussed and validated thanks to experi...
Modeling and Analysis of Transformer
The transformers are an integral part of the power system. In transformers, the main consequence of harmonic currents is an increase in losses, mainly in windings, because of the deformation of the leakage fields. Higher losses mean that more heat is generated in the transformer so that the operating temperature increases, leading to deterioration of the insulation and a potential reduction in lifetime. Due to the non-linear loads, the transformers are much affected by the distorted currents and supply voltages which largely reduce its efficiency due to overheating. Nonlinear loads cause harmonics to flow in the power lines which can overload wiring and many desktops, personal computers present nonlinear loads to the AC supply because of their power supplies design (capacitor input power supply). In power transformers, the main consequence of harmonic currents is an increase in losses, mainly in windings, because of the deformation of the leakage fields. Higher losses mean that more heat is generated in the transformer so that the operating temperature increases, leading to deterioration of the insulation and a potential reduction in lifetime. As a result, it is necessary to reduce the maximum power load on the transformer, a practice referred to as de-rating, or to take extra care in the design of the transformer to reduce these losses. To estimate the de-rating of the transformer, the load's K Factor may be used. Thus analysing this problem and reducing the losses of the transformer has become a major area of research in today's scenario. This report includes the effects of non-sinusoidal supply voltage on the transformer excitation current and the core losses which includes eddy current and hysteresis losses. INTRODUCTION Events over the last several years have focused attention on certain types of loads on the electrical system that results in power quality problems for the user and utility alike. Equipment which has become common place in most facilities including computer power supplies, solid state lighting ballasts, adjustable speed drives (ASDs), and uninterruptible power supplies (UPSs) are examples of non-linear loads. It is forecast that before the end of the century, half of all electrical devices will operate with a nonlinear current draw. These nonlinear loads are the cause of current harmonics. Non-linear loads are loads in which the current waveform does not have a linear relationship with the voltage waveform. Non-linear loads generate voltage and current harmonics which can have adverse effects on equipment that are used to deliver electrical energy such as transformers, feeders, circuit breakers, which are subjected to higher heating losses due to harmonic currents consumed by non-linear loads. The discontinuous, Harmonic currents cause overheating of electrical distribution system wiring, transformer overheating and shortened transformer service life. Electrical fires resulting from distribution system wiring and transformer overheating were rare occurrences until harmonic currents became a problem. Transformers which provide power into an industrial environment are subject to higher heating losses due to harmonic generating sources (non-linear loads) to which they are connected. The major source of harmonic currents is the switch mode power supply found in most desktop computers, terminals, data processors and other office equipment is a good example of a non-linear load. The switching action of the computer power supply results in distortion of the current waveform [2]. Harmonics are produced by the diode-capacitor input section of power supplies. The diode-capacitor section rectifies the AC input power into the DC voltage used by the internal circuits. The personal computer uses DC voltage internally to power the various circuits and boards that make up the computer. The circuit of the power supply only draws current from the AC line during the peaks of the voltage waveform, thereby charging a capacitor to the Peak of the line voltage. The DC equipment requirements are fed from this capacitor and, as a result, the current waveform becomes distorted. The increasing usage of non-linear loads on electrical power systems is causing greater concern for the possible loss of transformer life. So, Manufacturers of distribution transformers have developed a rating system called K Factor, a design which is capable of withstanding the effects of harmonic load currents. The amount of harmonics produced by a given load is represented by the term "K" factor. The larger the "K" factor, the more harmonics are present [3].
2016
The sound of a vacuum tube guitar amplifier may be significantly influenced by the non-linear behavior of its output transformer, which therefore should also be considered in digital simulations. In this work, we develop a model for inductors and transformers with the magnetization following the model of Jiles and Atherton. For this purpose, the original magnetization model is rewritten to a differential equation with respect to time which can then easily be integrated into a previously developed circuit simulation framework. The model thus derived is then exercised in the simulation of three simple circuits where it shows the expected behavior.
Transformer Transient Behavior Simulation by a Coupled Circuit-Field Model
Proceedings of the International Conference on Electrical Machines (ICEM), Paris, 1994, pp. 654-659.
The design and optimization of electrical machines is one of the most important research areas in electrical engineering. Transient behavior is sometimes a critical part of designing and limits setting. The effects of saturation and secondary armature reaction are considered in the transformer circuit model by changing suitable the mutual inductance. The proposed circuit field model follows the idea that if the main path flux linkages is calculated by solving a field problem one can avoid the mutual inductance computation. The proposed circuit field model is conceived to be solved by means of computer and takes fully into account the nonlinearity. Computer results via the usual circuit model and circuit-field model, compared with given tests, stand by to prove the proposed model usefulness. Abstract �h� design a�d o�timization of ��ec�rical ma c � i ne � is one of t�e mo� t im;Jcr-tan-= r-es ea ""c h areas in
Modeling and simulation of high voltage and radio-frequency transformer
Journal of Applied Physics, 2012
This work presents a methodology for designing a 50 kW RF transformer operating at a frequency of 400 kHz with a view to operation with minimal magnetic losses used in the project experimental treatment of industrial wastes and effluents of petrochemical thermal plasma. This innovator model of a RF transformer offers many advantages over traditional transformers, the main ones being their small size for this power level, high power density, low electromagnetic radiation level, and easy and economic manufacturing. The equivalent circuit was obtained practically and theoretically at the university lab. From the project, simulations are made to evaluate the performance of different parameters as a function of magnetic induction, current density, and temperature. V
Developments in the hybrid transformer model – Core modeling and optimization
This paper deals with the modeling of power transformers for calculation of switching transients based on mainly test report data. The paper is a follow-up of an IPST'07 paper and discusses the modeling and implementation of core saturation and losses in the Hybrid Transformer. A modified Frolich equation with knee-point adjustment and final slope handling is presented. The optimization process to fit the model to test report data is outlined and the modeling of topologically correct core loss is addressed. The inclusion of type 96 hysteretic inductors is presented. The final slope is a crucial parameter in inrush current calculations and requires design data.
IEEE Open Access Journal of Power and Energy
This paper presents a novel model for transformer windings to accurately represent the duality between electrical and magnetic circuits. The model can be used for the calculation of high-frequency transients in power systems and the design of high-frequency transformers, for example, those to be used in solidstate (utility-grade) transformers and power electronic converters. Existing circuit models do not consider the flux linkage in the winding thickness in a physical (dual) way. Duality is achieved by discretizing the winding thickness into thin subsections and distributing the proposed model building block across the winding. Analytical calculations are carried out to compare the accuracy of the proposed circuit for the computation of the terminal impedance, flux duality, and current distribution in the physical geometry of the winding. Further discretization is performed to extend the circuit to represent high-frequency phenomena: eddy currents and capacitive effects. The model can be easily implemented in any circuit simulation program using available circuit elements. The circuit parameters are computed with very simple expressions. The model is validated with finite element simulations. Differences of around 1% are obtained for relatively low model orders for high frequencies.
Recent Developments in the Modelling of Transformer Windings
2021
The paper provides a review of the modelling techniques used to simulate the frequency response of transformer windings. The aim of the research and development of modelling methods was to analyze the influence of deformations and faults in the windings on the changes in the frequency response. All described methods are given with examples of the modelling results performed by the authors of this paper and from literature sources. The research is prefaced with a thorough literature review. There are described models based on lumped parameters with input data coming from direct calculations based on the winding geometry and obtained from FEM modelling software and models considering the wave phenomena in the windings. The analysis was also performed for practical problems in winding modelling: the influence of windings other than the modelled one and the influence of parallel wires in a winding.
High frequency transformer model derived from limited information about the transformer geometry
International Journal of Electrical Power & Energy Systems, 2018
To represent transformer behaviour during a transient state which includes high frequencies, it is necessary to consider the resonances which occur inside the transformer. One strategy is to deduce the transformer model from the measurements of the transformer's frequency response, another one is to construct the model based on a careful representation of the inside of the apparatus. In the paper a model is presented which is compatible with EMTP-type software programs based on a finite element method (FEM) calculations and the complex permeability approximation. The model can be classified as a Grey Box transformer model, according to the terminology of the CIGRE. The model's frequency dependent parameters are derived from limited information about the transformer geometry. State space equations are used to input the model into an electromagnetic transient calculation software program. This approach requires specific mathematical treatments to avoid stability issues during simulations. The model is validated for lightning impulse studies using the field test measurements of overvoltages that had occurred at the external transformer's terminals.