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"Symmetrical components (Electric engineering)"
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Symmetrical components for power systems engineering
Emphasizing a practical conception of system unbalances, basic circuits, and calculations, this essential reference text presents the foundations of symmetrical components with a review of per unit (percent), phasors, and polarity--keeping the mathematics as simple as possible throughout.
Book
A reference current control strategy based on Sogi and FBD method for shunt active power filter
When the grid voltage is not ideal, most of the reference current control strategies of shunt active power filter often fail or are too complex. In this regard, this paper proposes a reference current control strategy for shunt active power filter based on the second-order generalized integrator and FBD method. This method first uses a second-order generalized integrator to extract the fundamental component of each phase of the grid voltage and the corresponding orthogonal component, and then obtains the fundamental positive sequence component of the grid voltage based on the symmetric component method. Then, the FBD method is used to decompose the load current based on the fundamental positive sequence component of the grid voltage to obtain the reference value of the compensation current. This method does not require complex coordinate transformation, and the calculation is simple and the physical meaning is clear. Finally, experiments show that the method can also compensate for harmonic current, reactive current and negative sequence current in various complex grid voltage and load environments.
Journal Article
Development of a Method for Estimating Topology and Line Impedance of Distribution Networks
This study presents a method for estimating distribution network topology based on three-phase symmetric component transformation and a sliding window algorithm. Owing to the grid connection of various energy sources, the demand for precise grid voltage control and management is increasing. Grid information such as network topology and line impedance is required for effective voltage control. Although several related studies have been conducted, most existing methods determine the network topology only based on the correlation coefficient between the measured voltages and the linear circuit equation assuming single-phase or system balanced conditions. Therefore, these methods are not applicable in unbalanced conditions and cause poor estimation for real networks. In this study, we propose a new method for estimating network topology and line parameters using only positive sequence components of measurement data based on the symmetrical components method, which overcomes the limitations of the existing methods. To verify the proposed method, we performed an estimation of the topology and line parameters of the modified IEEE 15 system reflecting unbalanced conditions in a case study.
Journal Article
Understanding Symmetrical Components for Power System Modeling
<p><b>An essential guide to studying symmetrical component theory</b></p> <p>This book utilizes symmetrical components for analyzing unbalanced three-phase electrical systems, by applying single-phase analysis tools. The author covers two approaches for studying symmetrical components; the physical approach, avoiding many mathematical matrix algebra equations, and a mathematical approach, using matrix theory. Divided into seven sections, topics include: symmetrical components using matrix methods, fundamental concepts of symmetrical components, symmetrical component s –transmission lines and cables, sequence components of rotating equipment and static load, three-phase models of transformers and conductors, unsymmetrical fault calculations, and some limitations of symmetrical components. In addition, this book:</p> <ul> <li>Provides concise treatment of symmetrical components</li> <li>Describes major sequence models of power system components</li> <li>Discusses Electromagnetic Transient Program (EMTP) models</li> <li>Includes worked examples to illustrate the complexity of calculations, followed by matrix methods of solution which have been adopted for calculations on digital computers</li> </ul>
eBook
Analysis of and reflection on the short-circuit fault of a large hydraulic generator
As a large hydro-generator carries a heavy load for the power grid, any fault in the generator would have extremely negative consequences for the power system, the power plant as well as for the local or even national economy. To minimise the risk of failure, the design, manufacture and operation of any large hydro-generator necessitates meticulous care and caution. Taking the real case of one power plant in China, this study conducts a detailed analysis of the cause of a failure at its large hydro-generator terminal because of a short-circuit fault. Based on a series of simplified calculations, the analysis finds that the main causes of the failure are 2-fold. On the one hand, instantaneous over-voltage by the short circuit generated strong over current and released huge electro-dynamic forces; on the other hand, the long period of de-excitation inevitably prolonged the short-circuit current, resulting in damage to the generator's windings as well as to other parts. The analysis uses the notion of instantaneous symmetrical components to explain the instantaneous over-voltage and strong over-current generated by the conversion fault in this particular case. It further emphasises the importance of rapid de-excitation in similar circumstances.
Journal Article
On-line Detection and Classification of PMSM Stator Winding Faults Based on Stator Current Symmetrical Components Analysis and the KNN Algorithm
The significant advantages of permanent magnet synchronous motors, such as very good dynamic properties, high efficiency and power density, have led to their frequent use in many drive systems today. However, like other types of electric motors, they are exposed to various types of faults, including stator winding faults. Stator winding faults are mainly inter-turn short circuits and are among the most common faults in electric motors. In this paper, the possibility of using the spectral analysis of symmetrical current components to extract fault symptoms and the machine-learning-based K-Nearest Neighbors (KNN) algorithm for the detection and classification of the PMSM stator winding fault is presented. The impact of the key parameters of this classifier on the effectiveness of stator winding fault detection and classification is presented and discussed in detail, which has not been researched in the literature so far. The proposed solution was verified experimentally using a 2.5 kW PMSM, the construction of which was specially prepared for carrying out controlled inter-turn short circuits.
Journal Article
Modeling of Measuring Transducers for Relay Protection Systems of Electrical Installations
The process of establishing relay protection and automation (RPA) settings for electric power systems (EPSs) entails complex calculations of operating modes. Traditionally, these calculations are based on symmetrical components, which require the building of equivalent circuits of various sequences. This approach can lead to errors both when identifying the operating modes and when modeling the RPA devices. Proper modeling of measuring transformers (MTs), symmetrical component filters (SCFs), and circuits connected to them effectively solves this problem, enabling the configuration of relay protection and automation systems. The methods of modeling the EPS in phase coordinates are proposed to simultaneously determine the operating modes of high-voltage networks and secondary circuits connected to the current and voltage transformers. The MT and SCF models are developed to concurrently identify the operating modes of secondary wiring circuits and calculate the power flow in the controlled EPS segments. This method is effective in addressing practical problems related to the configuration of the relay protection and automation systems. It can also be used when establishing cyber–physical power systems. For a comprehensive check of the adequacy of the MT models, 140 modes of the electric power system were determined which corresponded to time-varying traction loads. Based on the results of calculating the complexes of currents and voltages at the MT terminals, parametric identification of the power transmission line was performed. Based on this, the model of this transmission line was adjusted; repeated modeling was carried out, and errors were calculated. The modeling results showed a high accuracy when calculating the modules and phases of voltages using the identified model. The average error value for current modules was 0.6%, and for angles, it was 0.26°.
Journal Article
CNN-Based Fault Classification in Induction Motors Using Feature Vector Images of Symmetrical Components
Motor Current Signature Analysis (MCSA) is a commonly used non-invasive method for diagnosing faults in electric motors. Although MCSA provides significant advantages—current signals are easy to acquire and inherently robust against noise—this study aims to further enhance its diagnostic capabilities by focusing on symmetrical components. Three-phase stator current signals are converted into zero, positive, and negative sequence components, and their time-domain feature vectors are systematically integrated into a single image representation. A Convolutional Neural Network (CNN) is then employed for fault classification. The proposed method is model-free, requiring no explicit motor model, which offers greater flexibility compared to model-based techniques. Validation experiments were conducted on a rotor kit test bench under seven different conditions (one healthy condition and six mechanical/electrical fault conditions), with fault severities chosen to reflect practical scenarios. The symmetrical components-based image classification method demonstrated superior performance, achieving 99.76% classification accuracy and outperforming a widely used Short-Time Fourier Transform (STFT)-based spectrogram approach. These findings highlight that integrating all symmetrical component information into one image effectively captures each fault’s distinct behavior, enabling reliable diagnostic outcomes. By leveraging the distinct variations in zero, positive, and negative components under fault conditions, the proposed method offers a powerful, accurate, and non-invasive framework for real-time motor fault diagnosis in industrial applications.
Journal Article
Turn-to-earth fault modelling of power transformer based on symmetrical components
In this paper, a new approach to simulate transformer turn to earth fault, by using symmetrical components approach, has been presented. In the suggested novel modeling technique, the transformer turn to earth fault is simulated as a new healthy transformer with new short circuit (SC) impedance. This SC impedance is considered as the SC impedance of the transformer with the fraction part of the transformer winding through which the turn to earth fault occurs. The SC impedance of the reminder part of the transformer winding is added to the transmission line impedance or load impedance as external impedance. Hence, by using this suggested modelling technique, the system of turn to earth fault transformer is represented with a new system of a new healthy transformer, and the turn to earth fault is represented as an external line to ground fault. The values of the turn to earth fault current from this novel modelling technique (using the symmetrical components approach) were compared with those obtained by Electromagnetic Transient Program/Alternative Transient Program (EMTP/ATP). Finally, a suggestion method to estimate general information about the SC impedance of a three-phase three-winding transformer at different percentages of turn to earth fault is discussed.
Journal Article
A State of the Art of the Multilevel Inverters with Reduced Count Components
Multilevel inverters (MLIs) have become a trend in the field of DC/AC inverters and one of the main requirements in many of the industrial applications. MLIs spread in the academic research field and replaced the conventional inverters due to the several advantages that these topologies presented over the conventional inverters, as follows. (1) Operate with a high number of steps in the output voltage waveform, which helps in reducing the level of harmonics and presents fine and clear waveforms; furthermore, reduce the voltage stress on the switching devices and gives it a long lifetime and more reliability. (2) MLIs have a low rating of the switching devices, which has a noticeable role in reducing the system cost. (3) MLIs can be operated at both higher and lower switching frequencies, which reduces the level of power losses and enhances the overall efficiency. The main problem that faces the researchers in the multilevel inverters field is to design a topology that uses the optimum number of components to ensure the low cost and obtain a high efficiency. This paper presents a description of different topologies of MLIs that were investigated in the last two decades to show the pros and cons of each topology. Also a set of performance parameters that were used to measure the effectiveness of the MLI topologies have been discussed.
Journal Article