Analysis of Ferroresonance in a Transformer with B-H Loop Having Variable Core Loss

Accurate model of permanent magnet synchronous machine (PMSM) is significant for high-performance control. The machine model can be affected by various factors such as magnetic saturation and core loss effect, especially in the deep saturation and high-speed regions. This article proposes a data-driven-based machine modeling and compensation approach to improve the model accuracy by considering saturation and core loss effect. In the proposed approach, magnetic saturation is initially modeled using nonlinear polynomials and core loss effect is modeled with various speed data. The model mismatch due to these effects is then derived to generate the training data for the neural network (NN), which can accurately predict the model mismatch under various operating conditions. In comparison to the conventional model, the proposed approach adds compensation terms directly to the machine models, which can achieve better accuracy with efficiency and simple implementation, which can be utilized in motor control and parameter estimation. The proposed approach is validated on a laboratory interior PMSM and compared with existing methods under various operating conditions.

Ferroresonance is a complex electrical phenomenon, which can cause overvoltages in the electrical power system and endangers the system reliability and continuous safe operating. This paper studies the effect of linear and nonlinear core losses on the chaotic ferroresonance in a voltage transformer. For confirmation this aspect simulation has been done on a one phase voltage transformer rated 100VA, 275kV. The magnetization characteristic of the transformer is modeled by a single-value two-term polynomial with q=7. The simulation results reveal that considering the nonlinear core losses on the voltage transformer, exhibits a great effect on ferroresonance overvoltages. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos along with ferroresonance voltages has been obtained and presented.

Ferroresonance an electrical phenomenon may cause overvoltages in the electrical power system. In this paper, an overview of available papers is provided, at rst ferroresonance is introduced and then various type of ferroresonance in a voltage transformer (VT) is simulated. Then eect of new model of circuit breaker (CB) on damping ferroresonance oscillation is examined. Finally eect of earth resistance on the stabilizing these oscillations in the case of nonlinear core loss has been studied. Core loss is modelled by third order power series in terms of voltage and includes nonlinearities in core loss. For conrmation, the simulation is done on a one phase voltage transformer rated 100VA, 275kV. The simulation results reveal that novel modeling of circuit breaker exhibits great controlling eect on ferrores- onance overvoltages.

Resonance and ferroresonance in power systems are categorized as two destructive phenomena especially in HV networks which initiate in consequence of a power system event. In each event, the analysis of network voltages is conducted based on identified allowable limits by IEEE 519 standard as evaluation critera. In this paper, a novel comprehensive study approach is used for resonance and ferroresonance phenomena study in a real power system. The utilized approach comprises different steps including substation equipment modeling, EMT simulation of the probable switching events, evaluation of correspondence results, and finally detecting the probable ferroresonance occurrence. In this paper, the detailed evaluation results of a 230 kV substation are presented as an example. Using the proposed evaluations identifies the probable condition which may lead to the resonance and ferroresonance occurrence. The results are highly valuable for network operators in the prevention of unintended overvoltages occurrence.

Ferroresonance is a complex behavior of an electric network which if sustained, may be dangerous for power system equipment. Besides establishing mitigation techniques, researchers are also working on the prediction of ferroresonance occurrence in susceptible networks. The study requires appropriate mathematical model of transformer for computer simulations. A geometrical approach had been proposed by Rudenburg in the year 1950. But it was difficult to prove those proposals experimentally as ferroresonance may lead to complete destruction of the transformer and other equipment under test. Objective of this paper is to study on ferroresonance and observe the effect of variation of degree of saturation of transformer core materials on ferroresonance. For that, the transformer is approximated with its nonlinear dynamic model. With the help of that model, a Simulink block diagram has been developed in MATLAB. The Simulink model is examined under various circuit conditions, and a conclusion has been drawn that higher degree of saturation of the transformer core material increases the risk of ferroresonance to occur in the network.KeywordsFerroresonanceNonlinear model of transformerHysteresis modelDegree of saturationMagnetizing curve

Preface. Chapter 1: INTRODUCTION. 1.1 A Brief History of Electric Power Systems. 1.2 The Structure of the Power System. 1.3 Outline of the Text. Chapter 2: BASICS OF ELECTRIC ENERGY SYSTEM THEORY. 2.1 Introduction. 2.2 Concepts of Power in Alternating Current Systems. 2.3 Three-Phase Systems. 2.4 The Per Unit System. 2.5 Electromagnetism and Electromechanical Energy Conversion. 2.6 Permeability and Magnetic Field Intensity. 2.7 Flux Linkages, Induced Voltages, Inductance, and Energy. 2.8 Hysteresis Loop. 2.9 Eddy Current and Core Losses. 2.10 Energy Flow Approach. 2.11 Multiply Excited Systems. 2.12 Doubly Excited Systems. 2.13 Salient-Pole Machines. 2.14 Round or Smooth Air-Gap Machines. 2.15 Machine-Type Classification. 2.16 P-Pole Machines. 2.17 Power System Representation. Problems. Chapter 3: POWER GENERATION AND THE SYNCHRONOUS MACHINE. 3.1 Introduction. 3.2 The Synchronous Machine: Preliminaries. 3.3 Synchronous Machine Fields. 3.4 A Simple Equivalent Circuit. 3.5 Principal Steady-State Characteristics. 3.6 Power-Angle Characteristics and the Infinite Bus Concept. 3.7 Accounting for Saliency. 3.8 Salient-Pole Machine Power Angle Characteristics. Problems. Chapter 4: THE TRANSFORMER. 4.1 Introduction. 4.2 General Theory of Transformer Operation. 4.3 Transformer Connections. Problems. Chapter 5: ELECTRIC POWER TRANSMISSION. 5.1 Introduction. 5.2 Electric Transmission Line Parameters. 5.3 Line Inductance. 5.4 Line Capacitance. 5.5 Two-Port Networks. 5.6 Transmission Line Models. Problems. Chapter 6: INDUCTION AND FRACTIONAL HORSEPOWER MOTORS. 6.1 Introduction. 6.2 Three-Phase Induction Motors. 6.3 Torque Relations. 6.4 Classification of Induction Motors. 6.5 Rotating Magnetic Fields in Single-Phase Induction Motors. 6.6 Equivalent Circuits for Single-Phase Induction Motors. 6.7 Power and Torque Relations. 6.8 Starting Single-Phase Induction Motors. 6.9 Single-Phase Induction Motor Types. Problems. Chapter 7: FAULTS AND PROTECTION OF ELECTRIC ENERGY SYSTEMS. 7.1 Introduction. 7.2 Transients during a Balanced Fault. 7.3 The Method of Symmetrical Components. 7.4 Sequence Networks. 7.5 Line-to-Ground Fault. 7.6 Double Line-to-Ground Fault. 7.7 Line-to-Line Fault. 7.8 The Balanced Three-Phase Fault. 7.9 System Protection, An Introduction. 7.10 Protective Relays. 7.11 Transformer Protection. 7.12 Transmission Line Protection. 7.13 Impedance-Based Protection Principles. 7.14 Computer Relaying. Problems. Chapter 8: THE ENERGY CONTROL CENTER. 8.1 Introduction 8.2 Overview of EMS Functions. 8.3 Power Flow Control 8.4 Power Flow 8.5 Stability Considerations 8.6 Power System State Estimation 8.7 Power System Security 8.8 Contingency Analysis 8.9 Optimal Preventive and Corrective Actions 8.10 Dynamic Security Analysis Chapter 9: THE PRESENT AND FUTURE OF ELECTRIC ENERGY SYSTEMS. 9.1 Introduction. 9.2 Challenges Facing the System. 9.3 Blackouts and their Impact. 9.4 Mitigating and Coping. REFERENCES. INDEX.

Arresters are widely used in power systems to protect other equipment against overvoltages. However, in some conditions, they can’t operate successfully. One of the disturbances leading to the failure of the riser pole arresters is the ferroresonance overvoltages. In this paper, at first the influence of different transformer simulation models of ATP software on the occurrence of ferroresonance is studied and then the effect of ferroresonance on the riser pole arrester has been scrutinized through the thermal and electrical performance of the arrester in an underground distribution system. The results show that the arrester temperature rises due to energy dissipation in a ferroresonance circumstance, which indeed may result into the explosion of the arrester. Also, applying different models of the transformer in the ATP software and comparing the results, it is shown that the available models do not show the same effect on the arrester.

Since the discovery of nonlinear dynamics and chaotic behaviors of basic power converter circuits, stability analysis has been extended to more complex converter structures, paralleled and interconnected converters, microgrids, and power systems. While the analysis has long been identifying the parameters that cause various nonlinear phenomena, some work has shown direct relevance toward practical design of power converters, and control circuits. In this article, a review is conducted to highlight the key contributions of bifurcation analysis for power converter circuits and systems, and to discuss the ongoing work in this area.

Purpose – The purpose of this paper is to present a simple method to analyze the iron loss in the laminated core of power and distribution transformers. Design/methodology/approach – This paper presents a practical method to calculate the no-load loss in the transformer cores. Considering the non-uniformity of the magnetic flux density in the corner areas of the Epstein frames will affect the measurement precision of the Wt-B curves then further affect the core loss calculation in FEM, a dual-Epstein frame method is used to measure the Wt-B curves with the Epstein sample stripes cutting by different angles to the rolling direction. A 2D FEM that considers the type of joints of the core and eddy current effect in the laminations is used to analyze the core loss with multi-angle Wt-B curves. Findings – The impact of lamination thickness, size of gaps and type of joint of the core are considered. Considering the no-load testing conditions, harmonics in the exciting currents are taken into account. Originality/value – Harmonic wave of magnetic flux density in the transformer core is calculated and the core loss in the joint region is calculated by the loss curve measured with dual-Epstein frame. It makes the calculation result of transformer core loss more exactly.

Manganese-zinc (MnZn) power ferrites own significant applications in inductors and transformers for power conversion. The performance of these components is dependent on permeability, saturation induction, core losses, and dc bias superposition characteristics of MnZn ferrites. It is worth emphasizing that excellent dc bias superposition characteristics of ferrites are beneficial for the stability and efficiency of power converters operated with both ac and dc signals. In this paper, Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -doped MnZn ferrites are fabricated using a solid-state reaction method and used to investigate dc bias superposition characteristics of permeability and core losses. More importantly, the physical mechanism of the dc bias superposition characteristics is clarified. Furthermore, the effect of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> doping on the efficiency of buck circuit was also investigated. The dc bias superposition characteristics suggests potential application in power components and systems.

This paper presents a new design of transformer shape core used in railway system for loss reduction analyzed via the magnetic vector potential in the form of partial differential equation related to magnetic field. Finite element method is used in order to simulate a three-dimensional system. This paper focuses on the core loss reduction which is calculated from magnetic vector potential and magnetic field behavior on core transformer with V-connection, while the transformer has supplied voltage from three-phase system. The unbalanced input voltage is divided into three case studies in this paper: C-A couple phase, A-B couple phase and B-C couple phase from three-phase system. In addition, a design of transformer shape core has occurred on the corner that is the intersection between vertical core and horizontal core with 5 mm radius curves. The simulation results compare core loss of transformer between the original shape of transformer core and the new design of transformer core even though the supplied voltage is unbalanced. However, the results have shown that the new design of transformer core can decrease the core loss and it can lead to develop the shape of transformer core in order to reduce the core loss in term of manufacturing.

Reducing the magnetic losses of amorphous ribbon

Ferroresonance suppression in power transformers using chaos theory

The authors present the design of a laboratory with software and hardware structures for digital and physical simulation in the area of power systems control education. The hardware structure includes a physically based model of the power system. The software structure includes a special man-machine interface designed with a graphical user interface approach. This interface allows the user full control over the simulation and provides facilities for the study of the response of the simulated system. This approach is illustrated with the design of a control system for a physically based high-voltage DC transmission system model. >

Core loss estimation in switched reluctance motor is a complex task, due to non-linear phenomena and non-sinusoidal flux density waveforms. Several methods have been developed for estimating it (e.g. empirical, and physical-mathematic models), each one with merits and limitations. This paper proposes a new method for core losses estimation based on Finite Element Method Magnetics software. The main idea is using the machine phase-current harmonics as input for estimating core losses. In addition, a comparative study is carried out, where the proposed approach is faced up to a different one, based on Fourier decomposition of the flux density waveforms in the machine sections. In order to systematically analyze and compare the applied estimation cores loss techniques, a case study of a three-phase 6/4 SRM for different simulation scenarios is introduced. The outcomes of both methods are discussed and compared, where core loss convergence is found for limited speed and load ranges.