Effect of Harmonics on Symmetrical Components of Power Network Using Least Square Method

Since 1988, the system relay engineer of Kansas Power & Light Gas Service has served as a guest lecturer for the course on fault analysis and protection of power systems at Kansas State University. He meets the class five times during the semester. Two of these visits are field trips. In the other three visits he discusses power systems protection from a practicing engineer's point of view. He also discuss a practical design problem prepared for this class. The details of the course, the design project, and other activities are described. The benefits of such cooperation between university and industry are outlined. The main objectives of this course are to: make the students familiar with symmetrical components and fault analysis; make the students familiar with computer methods for fault analysis; make the students familiar with directional overcurrent, differential, distance, and pilot protection; impart practical knowledge on protection to the students; are prepare students for projection-related jobs in the utilities.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Mixed three-phase and six-phase power system analysis using symmetrical components method

The analysis of unbalanced power systems depends usually on transformation methods by which the phase quantities are substituted by, for example, symmetrical component quantities. These transformations had the computational advantages in the past, but with the use of digital computer, they no longer appear to be necessary. In this paper the analysis of power system faults including the simultaneous ones has been undertaken with the help of phase coordinates, i. e., the actual system phase voltages, currents and impedances. This approach is found to be simple and readily adaptable to digital computer techniques. Symmetrical components are, however, used as a measure of the system unbalance.

A Microsoft Windows graphical package to facilitate the teaching and learning of power system symmetrical components is described in this paper. This package is written in Microsoft Visual Basic 3.0. This software calculates and displays graphically, the ABC sequence and the corresponding symmetrical component phasors. Students can manipulate the graphical displays by keyboard input or by mouse operation. The objective of this package is to help the students to better understand the various aspects of symmetrical components' analysis through a user-friendly graphical user interface.

Grid converters are the key player in renewable energy integration. The high penetration of renewable energy systems is calling for new more stringent grid requirements. As a consequence, the grid converters should be able to exhibit advanced functions like: dynamic control of active and reactive power, operation within a wide range of voltage and frequency, voltage ride-through capability, reactive current injection during faults, grid services support. This book explains the topologies, modulation and control of grid converters for both photovoltaic and wind power applications. In addition to power electronics, this book focuses on the specific applications in photovoltaic wind power systems where grid condition is an essential factor. With a review of the most recent grid requirements for photovoltaic and wind power systems, the book discusses these other relevant issues: Modern grid inverter topologies for photovoltaic and wind turbines Islanding detection methods for photovoltaic systems Synchronization techniques based on second order generalized integrators (SOGI) Advanced synchronization techniques with robust operation under grid unbalance condition grid filter design and active damping techniques Power control under grid fault conditions, considering both positive and negative sequences Grid Converters for Photovoltaic and Wind Power Systems is intended as a coursebook for graduated students with a background in electrical engineering and also for professionals in the evolving renewable energy industry.

Chapter 28 - Optimal power generation and power flow control using artificial intelligence techniques

The dc symmetrical component method is introduced for the analysis and control of bipolar dc distribution systems under asymmetrical operation. This method is an extension of the classical symmetrical component theory in three-phase ac power systems. The asymmetrical voltage and current in the positive and negative poles are decomposed into symmetrical components in common and differential modes. The equivalent circuit for each mode is derived, which forms decoupled mode networks. Consequently, it allows for independent investigation of each mode, and provides an insightful view of the static and dynamic behavior of a bipolar dc power system. The dc symmetrical component method is a general approach which is applicable to different aspects of system design. As an example, an enhanced common-mode voltage regulation scheme is described. It suppresses common-mode LC resonance by adding active damping control, and reduces common-mode impedance to improve power quality and voltage stability. The major theoretical conclusions are verified by experimental results.

Guest Editorial

The continuous increase in power demand and huge power losses in modern power systems have been a growing concern to power utilities. Such phenomenon often results in epileptic power supply, power system instability, supply fluctuations and security problems in many parts of the globe. Identification of suitable places for the installation of reactive power compensators to minimize voltage drop and system power losses in a power system becomes imperative. In this paper, the Newton-Raphson iterative method was used for the power flow solution of the 28 bus Nigerian 330KV grid system. The Generalized Unified Power flow Controller (GUPFC) is installed at identified weak load buses of the Nigerian 28-bus power system to reduce the losses and voltage drop of the system. A comparative analysis of the GUPFC with Load Tap Changing Transformers (LTCT) is also performed. Result obtained shows that the GUPFC can largely (effectively) improve the system power stability and selectively balance the power flow of multi-lines power flows when placed at identified weak buses compared with LTCT. Thus, GUPFC can be used to reduce overall power losses along transmission lines as well as improve stability overall reliability of the power grid system.

The main aim of the power system is to meet the load demand within the power network involving economic operation, system reliability, system security and reduced environment impact. Proliferation of electrical power demand has given rise to various problems in the power systems. These problems include over loading, unbalanced system operation, poor voltage profile and increased power losses in the network. To address these issues there is a need to rely on additional source of generation and enrichment of transmission capacity. In this paper the placement of STATCOM, addition of new parallel transmission lines, placement of DG and their combinations are tested. The result shows the more than 60% of power loss reductions with 20-30% increment in the voltage values are observed.

Power system is one of the most complex systems ever designed. Determining its reliability is therefore a demanding process, which is mostly dealt with in a way that partial problems are stated and solved. A reliability method of loss of load expectation is selected and improved and the model of conventional power system is considered as a standpoint. Reliability of the initial conventional power system is evaluated. Then, the conventional power system is changed, where one conventional power plant is abandoned and new wind power plants stand to its place. The reliability of the initial and the changed power system is calculated and compared. Discussion shows the problems of decreased reliability of the power system with increasing the percentage of wind power plants within the power system replacing conventional plants, if not enough reserve is added to the power system at the same time. The other related problems are discussed in addition, to show that the problem is very complex and one cannot only consider a limited number of influencing parameters when deciding on power system configurations.

An adaptive method of symmetrical component estimation

Power transformers are essential components in power system networks, serving as their nerve centers. Because of this, it's vital to prevent any malfunctions in these transformers. Typically, a differential protection scheme is used to guard against internal short circuits. However, a significant drawback of this method is that it can sometimes malfunction during other abnormal conditions, such as external faults, magnetic inrush, and over-excitation. This paper presents an innovative algorithm that combines Random Forest and KNN (K-Nearest Neighbors) for classifying internal faults in both two-winding and three-winding transformers. We simulated various fault scenarios using MATLAB/SIMULINK to capture the current signals. The training for the Random Forest and KNN algorithms was conducted in PYTHON. The findings reveal that these algorithms effectively classify different operating conditions in power transformers. In our approach, the KNN algorithm achieved a remarkable accuracy of 99%, while the Random Forest algorithm reached 95%. Thus, we recommend the KNN algorithm for identifying internal faults amidst other abnormal operating conditions in real-world power transformer systems.

The problem of reliability and exploitation analysis of power systems used in intelligent transport systems (ITS) is extremely important from the point of view of ensuring the traffic safety. The use of advanced electronic devices in ITS systems requires their power supply from properly designed power systems. To ensure the continuity of operation of electronic devices, the basic and backup power supply are most often used. They should have specific values of reliability and performance indicators. Therefore, a reliability and exploitation model of the power system has been developed, taking into account renewable energy sources (RES), such as used in intelligent transport systems. This allowed to obtain dependencies enqabling to determine the probability of staying of the power system used in the intelligent transport system in the specified reliability and exploitation states.

Harmonic voltages and currents are created by nonlinear loads in power systems. These harmonics can cause serious problems to the energy suppliers (utility companies) and energy users (consumers). This dissertation presents new techniques for harmonic measurement and the accompanying problem, harmonic reduction. To reduce harmonics, the location and magnitude of harmonic sources must be known a priori. However, to measure and monitor harmonic sources requires specialized instrumentation that is not generally permanently installed at most buses. In this study, a method is developed to use neural networks in conjunction with state estimation for monitoring and estimating harmonic sources with only a few permanent instruments. The method can also identify and monitor a "suspected" harmonic source that has not previously been measured. Once harmonic sources are known, the objective from an energy supplier's point of view is to minimize the combined total harmonic distortion of all buses on a distribution system. A procedure is developed for designing optimum filters on distribution feeders that have distributed and balanced or unbalanced harmonic sources and variable compensating capacitors. The design includes finding optimum filter admittances and the corresponding locations. Symmetrical components are used for the unbalanced harmonic source case. Filter realization with the lowest cost including sensitivity analysis is also discussed. The optimum filters chosen and placed in this manner may produce results superior to the conventional filter design procedures. The problem of harmonic reduction is alternatively approached as an energy user's problem. The user's objective is to eliminate his voltage harmonic distortion problem locally without considering the effects of voltage distortion at neighboring buses. The remedy is insertion of a reactor in series with the local compensating capacitor. A method is presented for finding the optimum fixed LC combination to minimize voltage harmonic distortion at a load bus while holding the displacement factor (fundamental power factor) at a desired value and constraining the total cost of the compensating equipment. Source harmonics and impedances are represented as randomly time-varying quantities.