Ferroresonant Circuit Research Articles

Regulation system by voltage booster transformer

In this article, the features of the oscillatory circuit are investigated in order to determine the possibility of their application for controlling thrusters when building new, simple and reliable circuits for regulating booster voltage stabilizers from the value of the supply voltage. In Ferro resonant circuits connected to a voltage source with low internal resistance, with a certain combination of parameters, oscillations are excited at the fundamental frequency, the initial phase of which has a shift relative to the initial phase of the applied voltage.

Current source converter into stabilized voltage source based on electromagnetic ferromagnetic circuit

The article considers a series ferroresonant circuit connected in parallel with a linear capacitance, having an “N” - shaped current-voltage characteristic with a wide zone of the incident section. By compensating this section with a linear inductance characteristic connected in series with the resulting circuit, it is possible to create a device that converts a current source into a stabilized voltage source.

Analysis of subharmonic oscillations in three-phase Ferroresonant circuits with bias

In the theory of nonlinear electrical circuits, the analysis of physical processes occurring in three-phase Ferroresonant circuits during excitation of subharmonic oscillations (SHO) of the second order is of particular importance in the design and creation of various converter devices. From the point of view of creating multi-phase secondary power sources (phase-discrete devices, frequency dividers, switching elements, automation and relay protection devices, etc.), the study of second-order SHO excitation in three-phase Ferro resonant circuits with bias is of greatest interest. The article deals with the excitation of second-order subharmonic oscillations in three-phase self-oscillatory circuits with common magnetic circuits with a bias winding. Shortened equations are derived using the averaging method with appropriate phases. From the condition for the existence of a periodic solution, the phase and amplitude relationships of the excited oscillations are determined, which are different from three-phase circuits with a separate ferromagnetic element. In the steady state, the conditions of excitation, the region of existence are determined depending on the parameters of the circuit, the bias current and the applied action. The stability of the solution of the original system of nonlinear differential equations of the second order is also studied by analyzing the roots of the characteristic equation by a qualitative method. Numerical realization of the initial considered system of equations described, self-oscillatory processes is given.

Verification of Period-Doubling Behavior of Ferroresonance Circuit with the Jacobian Matrix and Eigenvalues

Verification of Period-Doubling Behavior of Ferroresonance Circuit with the Jacobian Matrix and Eigenvalues

EXPERIMENTAL FERRORESONANT CIRCUIT AS A PHYSICAL MODEL OF A FERRORESONANT PART OF THE ELECTRICAL POWER NETWORK

The paper presents types of ferroresonance as well as a part of the electrical power network in which the ferroresonance could occur. The experimental investigation of the ferroresonant parts of the electrical power network is not practically possible. Therefore, an experimental ferroresonant circuit is realized in the laboratory as a physical model of a ferroresonant part of the electrical power network, based on the 230-kV Converter Station Dorsey (Manitoba, Canada). Per-unit parameter values of the experimental ferroresonant circuit and 230-kV Converter Station Dorsey are compared as well as the results obtained from the measurements.

Analysis of subharmonic oscillations in multi-phase ferroresonance circuits using a mathematical model

The article about solution of system of nonlinear differential equations that are almost impossible to solve by analytical methods by constructing a mathematical model of nonlinear oscillations occurring in three-phase ferroresonance circuits. A system of nonlinear differential equations was formed by approximating the volt-ampere characteristics of a ferromagnetic element in a ferroresonance circuit. Mathematical models for solving technical problems characterizing subharmonic oscillation processes in three-phase ferroresonance circuits and systems using the finite-difference method are expressed in the form of differential equations without appropriate initial conditions. Amathematical model of a system of equations representing subharmonic oscillations in ferroresonance connections depending on the value of the selected parameters in the field of change of any variable is considered.

A MATLAB GUI teaching application for ferroresonance simulation

AbstractFerroresonance is a complex phenomenon and can compromise power system sustainability in transformer cores during the electromagnetic saturation process. Over‐voltage can be induced in the inductive core of transformers in an oscillation imbalance circuit; thus causing short circuits or permanent damage to a transformer. Hence, this paper developed a teaching application that combined a graphical user interface (GUI) in MATLAB with a SIMULINK function to model a ferroresonance circuit, to undergraduate engineering students at a Chinese University, as a part of a high‐ voltage engineering course. Students can adjust the parameters in the model to test different types of resonance voltage waveforms to obtain the corresponding power frequencies directly in the GUI. Through the interactive GUI environment, the difficulties that undergraduate students experience in distance education can be eliminated. A questionnaire of the 63 students who took the course was administered to measure student perceptions of this project‐based learning experience, and the responses are included in this paper.

The use of frequency converters on three-circuit ferroresonant circuits

In this paper, the processes of formation of low-frequency currents in the circuits of ferromagnetic oscillations are analyzed, and the theory of the formation of secondary amplitude frequencies of soft excitation of parallel and series-connected ferroresonant chains is developed. Based on this, considering the use of frequency dividers in the irrigation system shown in Figure 1, it is possible to carry out experiments on the study of multi-circuit frequency dividers. Therefore, the study of spontaneous (soft) vibration processes in multi-circuit ferroresonant electric circuits of periodic changes in the parameters of a ferromagnetic element generated by the resulting harmonic oscillations (HA) and their development and application of improved sources of harmonic signals for telecontrol of the system in power lines, switchgears and drainage networks.

Формирование максимальных перенапряжений при возникновении феррорезонансных процессов во время дуговых однофазных замыканий в низковольтных судовых электросистемах

The article discusses processes with single-phase faults in shipboard low-voltage electrical plants with a neutral grounded through a reactor. In such electrical plants, ferroresonant oscillations occur if one of the phases closes to the housing. The oscillations have an influence on the process of generating maximum arc overvoltages during single-phase shorts on the housing. The conditions for appearing ferroresonant phenomena in low-voltage ship electrical networks are studied. The processes in the ferroresonant circuit have been analyzed, the initial conditions necessary for their excitation have been identified. The processes causing the initial conditions in the power supply network that are sufficient for generating ferroresonant oscillations when the phase is closed to the housing have been considered. The conditions favorable for ferroresonant excitation are created due to the behavior of the low-voltage grounding arc and subsequent transient processes in the zero sequence circuit. Maximum overvoltages accompanied by ferroresonant processes occur when the grounding arc is burned in accordance with the theory of Peters and Slepian, that is, when it is extinguished at a moment close to the transition through the zero value of the forced component of the single-phase current short. The arc causes the increased voltages on the neutral grounding elements. As a result, the neutral bias voltage at a constant potential increases significantly. Based on the magnitude of the neutral bias voltage at a constant potential, the effect of ferroresonant oscillations on the maximum overvoltages arising in strong phases is estimated. The quoted formulas help to calculate the maximum values of arc overvoltages. The reliability of the proposed methodology for calculating overvoltages is confirmed by the studies performed on the physical model of the ship electrical network.

Phase relations in resonant circuits with a wide falling section on the amplitude characteristic

This article examines the features of circuits in order to determine the possibility of their use for controlling thyristors when building new, simple and reliable circuits for controlling boost voltage stabilizers. In ferroresonant circuits connected to a voltage source with a low internal resistance, with a certain combination of parameters, oscillations are excited at the fundamental frequency, the initial phase of which has a shift with respect to the phase of the applied voltage. Moreover, the phase of the excited oscillations depends on the magnitude of the applied emf.

Diagnostic approach in assessment of a ferroresonant circuit

This paper presents possibilities offered by a diagnostic system called FeD. The system is completely original; it has been developed by the authors on the basis of Arduino platform. The system has been designed to perform and record measurements and to carry out different numerical operations. The real-time function for several operations is incorporated in this system. The necessary input data for the system consist of the electrical voltage waveforms only. Rescaled voltage quantities can be displayed, measured, recorded or computed in any chosen way. The system has been developed particularly for measurements and computations in the ferroresonant circuits. The strongest part of the system is its versatility. It works with a standard PC and supports a universal connection (USB standard). This is undeniably a cost-wise solution. Driving and control of the system functions are carried out using the authors’ original software implemented in SciLab environment. This is free software, similar to and compatible with other existing CAD programs such as Octave and MATLAB. The obtained data, scripts and results can be freely transferred between them. The program is equipped with a transparent GUI. The need of constructing a special system to diagnose the ferroresonant circuit has emerged during earlier ferroresonance analyses and computations. Every ferroresonant circuit requires specific kind of diagnostics to estimate and display its base features in order to determine the best scientific approach to the problem. The ferroresonance phenomenon belongs to the domain of nonlinear problems. Its analysis requires excellent skills in mathematics and physics as well as computer science. Moreover, this subject also requires specialized engineering knowledge, particularly in the field of power engineering and power system equipment. Modern mathematical models and analyses used in ferroresonant computations are quite accurate; however, in case of a common user, they are often difficult to understand or implement. This paper provides full description of construction, features and test results of the developed hardware/software system designed for diagnostics of ferroresonant circuits. The test circuit case study has been performed in the entire power supply range. Results of measurements and computations as well as screenshots captured from authors’ original software are shown in different figures. The developed software and recorded data have been finally used in modeling and further simulations. During this, the application of the fractional derivative iron core coil model to ferroresonance analysis has been shown. The waveforms obtained from computer simulations have been compared with those obtained from measurements performed in the test circuit.

Diagnosis of a ferroresonance type through visualisation

The paper is focused on presenting the possible enhancements in visualisation of the ferroresonance phenomenon. The investigations have been performed with the usage of overcurrent/overvoltage responses of a ferroresonance circuit. The waveforms have been measured and recorded in a ferroresonant test circuit. Phase–plane/–space graphs analysed in this paper are a visual display of certain type characteristics for the time dependent system of nonlinear differential equations. The application of Poincare maps is also mentioned in the paper.

Accurate simulation model for a three-phase ferroresonant circuit in EMTP–ATP

This study presents a simulation model for a ferroresonant circuit. The proposed model includes a transformer model and a vacuum circuit breaker (VCB) model. Hysteresis nonlinearity and core topology are considered in the transformer model. The VCB model comprises the current chopping level, withstand capability, and quenching capability. Fundamental ferroresonance and sub-harmonic ferroresonance experiments are conducted to verify the accuracy of the proposed ferroresonance simulation model. Bifurcation, phase-plane, and Poincare methods are used to compare the difference between the simulation and experiment results. The proposed model can accurately predict the ferroresonance, and the waveform similarities calculated from the experiment and simulation data are greater than 0.9.

Suppressing ferroresonance in potential transformers using a model-free active-resistance controller

Ferroresonance, excited by saturated electromagnetic voltage transformers, can severely damage power systems because it produces long duration large overvoltages. In this paper, a method is developed to eliminate potential transformer (PT) ferroresonance through a model-free method. First, a structural diagram of the ferroresonance eliminating device is established based on a practical ferroresonant circuit. The effect of the adjustable parameters of the device is investigated, including resistance, pulse frequency, and pulse duty cycle. Then, Iterative control strategies are developed to adjust the gate signal duty cycle of the controller for limiting the ferroresonance to a normal status and then switching off the elimination device. Finally, simulations are conducted demonstrating that the method proposed was effective.

Electromagnetic transient study on flexible control processes of ferroresonance

Ferroresonance, which is a common phenomenon in power systems, have threatened the security of power systems for a long time. Although several ferroresonance suppression measures have been applied in power systems, ferroresonance still occurs occasionally. In this study, a flexible control strategy to control different ferroresonant modes is proposed. The behavior of a typical ferroresonant circuit acquired from a ferroresonance testing system to obtain the electromagnetic transient and control details of the control method is also investigated. The key parameters in the control module are determined, including the switching frequency and the coefficients of the proportional–integral (PI) controller. Then, six typical ferroresonant overvoltages are selected as control systems using the proposed method. Given the effect of a damping resistor and fully controllable power electronic switches with a gate signal controlled by a proportional–integral (PI) control system, these six typical ferroresonant overvoltages can all be suppressed in 0.12s to the non-ferroresonant state after the controller is activated. The electromagnetic transients, including the essential system state quantity transients in the control process, are also investigated. At last, a laboratory prototype is implemented, and the experimental results show that the proposed method is useful for ferroresonant overvoltage control.

Analytical Solution to Fundamental Ferroresonance of Ineffectively Grounded Three Phase Transformers

This paper investigates the effect of neutral ground resistance on the ferroresonance behavior of a three phase transformer. For simplicity only fundamental ferroresonance (FF) solutions has been addressed. Harmonic balanced method has been used to formulate an analytical solution to the problem of fundamental frequency ferroresonance (FF) in a three phase system. Continuation has been used to study ferroresonance circuit around parameter space when a control parameter is varied. Time domain simulation has been carried out and compared with analytical solutions. The results reveal that the presence of neutral resistance, even a low value, has a major role on FF stability domain. Different scenarios like one phase and two phase switching have been studied.

Chua’s model of nonlinear coil in a ferroresonant circuit obtained using Dommel’s method and grey box modelling approach

Chua’s model of the nonlinear coil is often used in ferroresonance research. In this paper, two methods are used to determine such a model: usual Dommel’s method and a grey box modelling approach, which is a novel way to model the nonlinear coil in a ferroresonant circuit. The parameters of the grey box model are determined by nonlinear regression using a metaheuristic optimization algorithm. The obtained models are evaluated by comparing the steady-state types obtained by measurements with those obtained using simulation. Comparing the obtained Chua’s models, results indicate that the grey box modelling approach is more accurate than Dommel’s method for lower coil nominal voltage. However, the main conclusion is that Chua’s model in general cannot be used to predict all steady-state types typical for ferroresonance, i.e. it can be used in a highly restricted manner for appearance of certain steady-state types only.

Ferroresonance conditions in wind parks

Wind parks are made up of a large number of saturable inductances (power transformers, inductive voltage transformers (IVTs)), as well as capacitors (cables, wind turbine harmonic filters, capacitor voltage transformers (CVTs), voltage grading capacitors in circuit-breakers). Therefore, they may present scenarios in which ferroresonance occurs. This paper presents the scenarios that can lead to ferroresonant circuits in doubly fed induction generator (DFIG) based wind parks. Ferroresonance conditions and their consequences are demonstrated by simulating the detailed model of the wind park in EMTP-RV. The wind park simulation model includes detailed models of wind turbines, medium voltage (MV) collector grid, high voltage/medium voltage (HV/MV) wind park substation, overvoltage, overcurrent and differential current protections, current transformers (CTs), IVTs and CVTs.

Estimation of Electronic Suppression Circuit Resistance for Protective Relaying Applications

The transient response of instrument transformers affects the performance of high-speed relays, particularly speed and overreach in case of distance protection. Transient response of a capacitive voltage transformer depends on the type of ferro-resonance suppression circuit (FSC), i.e., active, passive, or electronic, provided in the secondary to damp the ferro-resonant oscillations. The objective of this article is not to estimate optimum resistance but to provide a systematic approach instead of the trial-and-error approach to estimate damping resistance for the electronic ferro-resonance suppression circuit used in the: capacitive voltage transformer for protective relaying application. The performance of the numerical distance relay for the: capacitive voltage transformer with estimated damping resistance in the electronic ferro- resonance suppression circuit is tested and validated in real time using a field programmable gate array.

Experimental Investigation of Symmetry-Breaking in Ferroresonant Circuit

This study focuses on the impact of circuit parameters on the breaking of steady-state symmetry in a ferroresonant circuit. Symmetry-breaking occurs owing to pitchfork bifurcation and results in the ambiguousness of steady-state solution through two possible waveform types. The two types are distinguished in this study by positive and negative peak values of capacitor voltage. Circuit parameters analyzed in detail are source voltage RMS value U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and initial values of capacitor voltage and coil remanent flux. There is symmetry of occurrence in the two types of waveform, which is expected because of the odd symmetry of characteristics of all passive circuit elements. It is shown that the property of symmetry could be experimentally demonstrated and through simulation using a mathematical model of the experimental ferroresonant circuit. In addition, measurements have been carried out with two further coils to investigate the impact of the nominal voltage and type of core material on the initiation of the two types of waveforms.