Wrocław University of Science and Technology
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Detection of the Fundamental Harmonic of Distorted Signals using Min-Norm Method
No full textSpectrum analysis is a fundamental tool for diagnostic purposes widely used in monitoring and diagnostic systems. Estimation of frequencies of multiple sinusoids in the presence of noise arises in many areas of electrical power engineering. The most recent methods of spectrum estimation are based on the linear algebraic concepts of subspaces. Min-norm harmonic retrieval method is an example of eigenstructure-based methods, which yield high resolution and asymptotically exact results. In this paper some results of simulation investigations of inverter-fed induction motor drive are presented. We use the EMTP-ATP program to simulate the PWM converter supplying an asynchronous motor. A measuring system consisting of the data acquisition module SigLab™ and a personal computer was realised and tested
Comparison between step and pulsed electroacoustic techniques using both PVDF and LiNbO3 transducers
No full textTwo kinds of piezoelectric transducers thin PCDF foil and thick LiBNO3 crystal were used as strain waves detectors. The time domain analysis was applied for analysis and interpretation of measured oscillograms. The space charge, electrical field and potential profiles across the thickness of three layered PTFE samplaes have been shown
Distanzschutz mit Mikrorechnern
Get PDFNachdem erst vor kurzem in der Schutztechnik die Technologie der elektromechanischen Relais durch den elektronischen ("statischen") Schutz abgelöst wurde, stehen wir zur Zeit bereits wieder vor einer Wende: Die Technologie der Mikroprozessoren macht auch vor diesem Bereich nicht halt; im Gegenteil: der Mikrorechner ist für die schwierigen Meßaufgaben in der Schutztechnik geradezu prädestiniert. Ausgehend von verschiedenen Modellen werden einige Algorithmen entwickelt, mit deren Hilfe man aus den Augenblickswerten von Strom und Spannung die komplexe Impedanz der zu überwachenden Leitung berechnen kann. Diese Algorithmen werden einem dreifachen Test unterworfen. Dabei sind die Strom- und Spannungsverläufe völlig unterschiedlicher Herkunft: Mit dem Rechner simuliert, am Netzmodell und im Netzversuch gemessen. Es zeigt sich, daß mit einem Mikrorechner vom Typ lntel 8086 drei Schleifenimpedanzen in weniger als l ms berechnet werden können und daß in weniger als 10 ms der Fehlerort eingemessen werden kann. ___ It was only recently that the technology of the electromechanical relais was replaced by pure electronic protection devices. At the moment we are again standing at a turning-point: The technology of microprocessors cannot be stopped in this field either. On the contrary, one could say that the microcomputer was almost predetermined for the difficult measuring tasks in the field of protection. Using different models ceveral algorithms were developed: applying the scanned values of current and voltage the complex impedance of the line under supervision can be calculated. These algorithms are subjected to a threefold test, in which the shapes of current and voltage curves are generated in completely different ways: they are simulated by computer and measured on a network analyser and in a field test. It turns out that by using the microcomputer lntel 8086 three loop impedances can be calculated in less than l ms, and that the location of the short circuit can be determined in las than 10 ms
Assessment of Transients in Power System with Wind Generators by Application of Prony Method
Get PDFWind power installations impact on power quality is crucial for power system operation. This paper presents modeling and simulation of an induction generator driven by wind turbine. Especially switching transients have been simulated and analyzed. Prony algorithm has been applied to determine signal parameters in different operation modes of wind generation unit. Detailed power quality studies on transients are helpful in better assessment of the phenomena
Fast cathode processes in conditioning of vacuum electrodes
Get PDFHigh - speed streak photographs of vacuum breakdown show oscillations in light emission at the cathode . Experimental results are presented that show the change in frequency of that oscillation as conditioning progresses. The link between the oscillations and conditioning supports the hypothesis that adsorbed gas removal is the cause of conditioning in vacuum breakdown
Analiza widmowa sygnałów dyskretnych
Get PDFCelem ćwiczenia jest przeprowadzenie analizy widmowej dyskretnych sygnałów okresowych przy zastosowaniu szybkiego przekształcenie Fouriera (FFT) oraz zbadaniu wpływu różnych czynników na dokładność przetwarzania. Do analizy i wizualizacji otrzymanych wyników wykorzystano funkcje programu MATLAB
Szybkie przekształcenie Fouriera
Get PDFWprawdzie DFT jest najbardziej bezpośrednią procedurą matematyczną do określania częstotliwościowej zawartości ciągu z dziedziny czasu, jest ona bardzo nieefektywna. Ponieważ liczba punktów w DFT wzrasta do setek lub tysięcy, liczba wymaganych do przetworzenia danych staje się bardzo szybko gigantyczna. W 1965 roku został opublikowany przez Cooley'a i Tuckey'a artykuł przedstawiający bardzo wydajny algorytm implementujący DFT. Algorytm ten jest obecnie znany jako szybkie przekształcenie Fouriera (ang. Fast Fourier Transform — FFT)
Some conditions for strong asymmetric double injection in insulators and semiconductors
Get PDFIn this paper a space-charge transport model is studied. As a model system the planar capacitor is used. A boundary problem for space charge transport is presented. The effect of the mechanisms of carrier injection on the current-voltage characteristics is shown. It was found that the current-voltage characteristics can be strongly nonlinear. Einige Bedingungen fur stark asymmetrische Doppelinjektion in Isolierstoffen und Halbleitern. Ein Model1 des Transportes von Raumladungen wird untersucht. Als Modellsystem wurde ein Plattenkondensator venrendet. Randprobleme des Raumladungstranportes werden dargestellt. Der EinfluB des Injektionsmechanismus auf die Strom- Spannungs -Kennlinien wird ebenfalls angegeban. Die Untersuchungen zeigen, dass die Kennlinien starke Nichtlinearitaeten aufweisen konnen
Investigations of Influence on Power Quality of Superconducting Fault Current Limiter
Get PDFWaveforms obtained from a superconducting Fault Current Limiter are investigated using the Prony modeling technique. Comparable measurements with the use of standard tools of spectral analysis (like FFT) fail because of short data available and low levels of higher spectral components
Artificial Neural Network for Real-Time Estimation of Basic Parameter of Signals
Get PDFThis paper presents for students instructions to using parallel algorithms, which can be implemented by analogue adaptive circuits employing some neural networks principles for estimation of parameters of signals in power system. Algorithms based on the standard least-squares (LS) criteria is proposed. The problem of estimation is formulated as an optimization problem and solved by using the gradient descent optimization algorithm. The corresponding architectures of analogue neuron-like adaptive processors are also shown