Wrocław University of Science and Technology
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Automated Classification of Power Quality Disturbances using SVM and RBF Networks
Full text linkThe authors propose a new method of power quality classification using SVM (Support Vector Machine) neural networks. Classifier based on RBF networks (Radial Basis Function) was in parallel applied to enable proper performance comparison. Both, RBF and SVM networks are introduced and considered an appropriate tool for classification problems. Space phasor is used for feature extraction from three-phase signals, to build distinguished patterns for classifiers. In order to create training and testing vectors different disturbance classes were simulated (e.g. sags, voltage fluctuations, transients) in Matlab. Finally, the investigation results of the novel approach are shown and interpreted
Wavelets an Hilbert Transform methods for detection of voltage dips and micro interruptions
Full text linkIn electrical energy power network, disturbances can cause problems in electronic devices therefore their monitoring is fundamental in Power Quality field both to properly dimension protections and to calculate compensations in case of malfunction of the apparatus. In this paper we address the problem of disturbances estimation by using two different signal processing methods such as Wavelets processing and Hilbert Transform (HT). This last is employed as an effective technique for tracking the voltage in distribution systems. The mathematical simplicity of the proposed technique, compared with the commonly used algorithms from the literature, renders them competitive candidate for the on-line tracking of disturbances. The accurate tracking of the HT facilitates its implementation for the control of disturbances mitigation devices. Simulation results are provided to verify the tracking capabilities of the HT and to evaluate its performance as pre-processing for an embedded system. Two algorithms have been tested on voltage dip under different conditions of noise and voltage harmonic distortion (THD) realizing a comparison between them that shows that the Hilbert Transform can be used as a valid methodology for this type of phenomena
Power Distortion Issues in Wind Turbine Power Systems Under Transient States
Full text linkIn this paper time-frequency methods have been investigated for complex investigations of transient states in wind power plants. Application of parallel processing in time and frequency domain brought new findings in description of wind power plants working under transient conditions. Proposed algorithms represents standard Short-Time Fourier Transform (STFT) as well as alternative methods associated with Cohen’s class: Choi-Williams Distribution (CWD) and Zhao-Atlas-Marks Distribution (ZAMD). In order to explore advantages and disadvantages of the method several experiments were performed using model of squirrel-cage induction machine connected directly to the grid. Investigated phenomena concerned power distortion caused by switching-on capacitor banks and faults as well as influence of wind speed on instantaneous character of the transient states
Inclined plane test, influence of transformer power
Full text linkThe inclined plane method is one of a few other tests that prove the material resistance to erosion and tracking caused by surface discharges. In this paper the review of inclined plane tests and the influence of additional factors were shown. A simple method for evaluating the voltage source rigidity was proposed
Insulators Glaze Modified by Plasma Processes
Full text linkSurface properties of electrical insulators are responsible for their behaviour, especially during heavy rains in contaminated areas. Different means are used in service to overcome this problem. A new approach can be applied here which involves the technology of plasma processes t9 modify surface properties of materials. Glaze is the last layer of electrical insulators and it is highly hydrophylic. To modify this some changes in constitution of glaze has to be done and new hydrophobic layer must be created. Such kind of treatments of surface is possible in plasma processes. During these processes -the heterogenous plasma polymerization takes place on the surface of glaze and thin deposition film is built. From the electrical applications point of view such films have very interesting properties ( high hardness, low friction, good adhesion to substrates, chemical stability).Some electrical properties of plasma modified real insulator glaze have been presented
Determination of Resonant Frequencies for a Power System: A New Approach
Full text linkThe paper deals with the harmonic resonance problem. At the beginning, disadvantages of the only viable method for resonant investigations, i. e. the method based on frequency scan analysis of the node impedances, are enumerated. Then, the theoretical background for the calculations of resonant frequencies is presented. In the paper one utilizes description of the system with use of state equations. After the conditions of occurrence of resonance are described, the manner of calculation resonant frequencies is discussed. The proposed approach is illustrated by two examples. In the first example a simple RLC circuit is considered, in the second one for the IEEE 14-bus test system the resonant investigations are made. At the end, the features of the described approach are analysed
Rekrutacja 2009 -2010
Full text linkKIERUNKI STUDIÓW I SPECJALNOŚCI: • Automatyka i Robotyka • Automatyka i Sterowanie w Energetyce • Automatyzacja Maszyn, Pojazdów i Urządzeń • Elektrotechnika • Elektroenergetyka • Inżyniera Elektryczna • Odnawialne źródła energii • Control in Electrical Power Engineering (MSc in English) Program „Podwójny Dyplom” (w języku niemieckim lub angielskim
Komputerowe metody analizy elektromagnetycznych stanów przejściowych. Przykłady.
No full textZamieszczone przykłady są uzupełnieniem materiału zawartego w książce Komputerowe metody analizy elektromagnetycznych stanów przejściowych, Oficyna Wydawnicza Politechniki Wrocławskiej, Wrocław 2009.. W szczególności, przykłady umieszczone w Dodatku C ilustrują zastosowanie programu ATP-EMTP do rozwiązywania następujących zagadnień: Przyklad_C1_1 - tworzenie modułów w trybie wsadowym. Przykład_C1_2 - tworzenie modeli w edytorze graficznym ATPDraw. Przykład_C1_3 - tworzenie modułów w edytorze ATPDraw. Przykład_C2 - uniwersalny model transformatora trójfazowego. Przykład_C3 - model analogowego filtru odcinającego. Przykład_C4 - model zabezpieczenia różnicowego transformatora. Przykład_C5 - symulacyjna analiza rozruchu silnika indukcyjnego. Przykład_C6 - model dwustronnie zasilanego generatora indukcyjnego. Przykład_C7 - symulacyjna analiza adaptacyjnego układu automatyki SPZ. Przykład_C8 - model statycznego kompensatora mocy biernej. Pozostałe przykłady zawierają numeryczne programy związane z odpowiadającymi im przykładami zamieszczonymi w książce
Computation of Voltage Sag Initiation with Fourier based Algorithm, Kalman Filter and Wavelets
Full text linkDynamic Voltage Restorers (DVR) have been successfully applied for voltage dip mitigation in the last years. Especially in systems with nonlinear loads and wind turbine generation DVR units support the Power Quality enhancement. The reliability and quality of DVR operation depends mostly on fast and accurate voltage dip detection. Detection methodologies must be able to detect a voltage dip as fast as possible and be immune to other types of perturbations. In this paper we address the problem of voltage dip estimation using carefully selected advanced signal processing methods such as Fourier based algorithm, Kalman filtering and Wavelets. Additionally, the traditional and common technique of RMS value tracking has been mentioned. The algorithms have been tested under different conditions: voltage dip with phase jump, noise, frequency variations