Wyniki 1-10 spośród 25 dla zapytania: authorDesc:"Gorazd ŠTUMBERGER"

Determining parameters of a three-phase permanent magnet synchronous machine using controlled single-phase voltage source

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This paper compares and evaluates different experimental methods for determining permanent magnet synchronous machine (PMSM) parameters. They are based on numerical integration, analysis of current time-response and harmonic analysis combined with calculation of phasors and impedances. The results presented in the paper show that the parameters of two-axis PMSM dynamic model can be determined with sufficient accuracy even when the three-phase PMSM with appropriately connected windings is supplied with a single stepwise changing voltage. Streszczenie..W artykule porównano i ewaluowano różne metody eksperymentalne dla określenia parametrów maszyn synchronicznych z magnesem trwałym. Metody te bazują na numerycznym całkowaniu, analizie prądowych odpowiedzi czasowych, oraz analizie harmonicznej połączonej obliczaniem fazorów i impedancji. Wyniki przedstawiane w artykule pokazują, że parametry dwuosiowego modelu silnika mogą być wyznaczone z wystarczającą dokładnością nawet wtedy, kiedy trójfazowy silnik zasilany jest z pojedynczego z krokowo zmiennego napięcia. (Określanie parametrów trójfazowej maszyny synchronicznej z magnesem trwałym przy użyciu jednofazowego źródła napięcia) Keywords: permanent magnet synchronous machine, experimental methods, controlled voltage source, parameters. Słowa kluczowe: maszyna synchroniczna z magnesem trwałym, metody doświadczalne, źródło ze sterowanym napięciem, parametry Introduction Parameters of three-phase AC machines are normally determined by means of measurements of current and voltage on the terminals of the machine supplied with threephase voltages. An inverter or an electric grid can be used as a three-phase voltage source. Standard methods for determining parameters of AC machines are normally based on tests performed at no-load, different loads and locked rotor, where the machine is supplied with sinusoidal voltages at rated frequency, using Fourier analysis and root-mean-square values of measur[...]

Comparison of different experimental methods for determining the magnetically nonlinear iron core characteristics of transformers

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This paper is divided into two sections. In the first section, different experimental methods for determining magnetically nonlinear iron core characteristics of transformer are described and evaluated. In the second section the obtained characteristic were used in nonlinear dynamic model of a single-phase transformer. The comparison of the measured and by the dynamic model calculated results is given for the case of transformer steady state operation at rated load and for the case of switch-on of unloaded transformer. Streszczenie. Artykł jest podzielony na dwie części: w pierwszej doświadczalne metody są opisane i ewaluowane, w dtugiej otrzymane doświadczalnie charakterystyki są uzyte w modelu jednofazowego transformatora. Porównanie pomierzonych i obliczonych z modelu wartości zostało przeprowadzone dla warunków pracy ustalonej i dla przypadku właczenia transformatora do sieci. (Porównanie różnych metod doświadczalnych dla okresślenia charakterystyki magnetycznie nieliniowego rdzenia transformatora) Keywords: dynamic model, magnetic nonlinearities, parameters, power transformer Słowa kluczowe: model dynamiczny, magnetyczne nieliniowości, parametry, transformator mocy Introduction This paper deals with determining parameters of a magnetically nonlinear dynamic model of power transformer. The paper focuses on determination of magnetically nonlinear iron core characteristic (i). It is determined by the classical methods based on no load test and by the alternative methods based on numerical integration of measured currents and voltages [1-3]. A power grid and linear amplifier were used as a voltage source. The linear amplifier was used to generate sinusoidal and stepwise changing voltage waveforms. A comparison of magnetically nonlinear characteristics determined by the different methods is presented. The magnetically nonlinear dynamic model of power transformer is evaluated through a comparison of measured and calculated c[...]

Magnetic field emissions caused by overhead power line: analytical calculations, numerical calculations and measurements

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Abstract. In the paper an analytical method for calculation of magnetic field emissions, caused by overhead power line, is dealt with. The obtained results are verified with measurements performed on a 400 kV double-system overhead power line and with numerical calculations using finite elements method. The results obtained by the proposed analytical method are compared with results of calculation where conductor sagging is considered. The proposed method is suitable to be used in optimization procedures where the computational time could have an important role. Streszczenie. W artykule opisano analityczną metodę obliczania emisji pola magnetycznego przez napowietrzną linię elektroenergetyczną. Wyniki porównano z pomiarami przeprowadzonymi na linii napowietrznej dwutorowej 400kV z wykorzystaniem metody elementów skończonych. Proponowana metoda pozwala na dużą oszczędność czasową i optymalizację tego rodzaju obliczeń. (Emisja pola magnetycznego napowietrznych linii elektroenergetycznych - obliczenia analityczne i numeryczne oraz pomiary). Keywords: overhead power line, measurements, magnetic fields, FEM. Słowa kluczowe: napowietrzna linia elektroenergetyczna, pomiary, pole magnetyczne, FEM. Introduction People become increasingly aware of the overhead power lines presence which might influence their health. This concern leads to the different objections related to the construction of the new and the re-constructions of the existing overhead power lines [1], [2]. In that sense the increased public concern about exposure to magnetic field emissions presents an important technical issue. Especially relations between the magnetic field emissions and the induced body currents are often taken as a basic restriction criteria of different international organizations like WHO, ICNIRP, etc [1]. The recent research findings led to the limitation of allowed currents induced in a human body, which are set to 10 mA/m2 at the occupational area and t[...]

Comparison of experimentally and by the finite element method determined magnetically nonlinear iron core characteristics applied in the dynamic model of a single phase transformer

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This paper deals with comparison of experimentally and by the finite element method determined magnetically nonlinear iron core characteristics. The obtained characteristic were used in the dynamic model of a single phase transformer. The comparison of the measured and by the dynamic model calculated results is given for the case of transformer steady state operation at rated load and for the case of switch-on of unloaded transformer. Streszczenie. W artykule przedstawiono porównanie podejścia eksperymentalnego i metody elementów skończonych w wyznaczaniu nieliniowej charakterystyki magnetycznej rdzenia żelaznego. Analizy dokonano poprzez wykorzystanie wyznaczonych charakterystyk w modelu dynamicznym transformatora jednofazowego i ich porównaniu dla pracy w stanie ustalonym z obciążeniem oraz przy załączaniu nieobciążonego transformatora. (Porównanie podejścia eksperymentalnego i metody elementów skończonych w wyznaczaniu nieliniowej charakterystyki magnetycznej rdzenia żelaznego w transformatorze jednofazowym z wykorzystaniem modelu dynamicznego urządzenia). Keywords: dynamic model, magnetic nonlinearities, experimental methods, FEM, power transformer. Słowa kluczowe: model dynamiczny, nieliniowości magnetyczne, metody eksperymentalne, FEM, transformator energetyczny. Introduction This work deals with magnetically nonlinear dynamic model of a single phase transformer. In order to achieve the best possible agreement between the measured and calculated responses the dynamic model is completed by the magnetically nonlinear characteristic of the tested transformer. It is given as current-dependent flux linkage characteristic, which is determine experimentally and by applying the finite element computations. Nowadays, there exist many electromagnetic devices with magnetically nonlinear iron core. For analysis of these devices and for their control design dynamic models are required. When the magnetically nonlinear properties of the devi[...]

Optimization based reduction of the electromagnetic field emissions caused by the overhead lines

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This paper deals with the reduction of electric and magnetic field emissions caused by the single-circuit 400 kV overhead power line. These emissions are especially important on the border of the overhead power line right of way, where electromagnetic field emissions should be under prescribed limits. This paper deals with the two solutions. Firstly the usage of higher towers is investigated, while secondly the new conductor arrangements is defined in the optimization process. Streszczenie. W artykule poruszono problem ograniczenia emisji pola elektromagnetycznego wywołanego linią elektroenergetyczną 400 kV. Emisja ta jest szczególnie istotna na obszarze dostępnym (right-of-way) gdzie emisja pola elektromagnetycznego podlega szczególnym restrykcjom. Artykuł pokazuje dwa rozwiązania: użycie wyższych słupów energetycznych lub/i zastosowanie nowych ustawień przewodów energetycznych. (Optymalna redukcja emisji pola elektromagnetycznego wywołanego liniami napowietrznymi) Keywords: optimization, electric fields, magnetic fields, overhead power lines. Słowa kluczowe: optymalizacja, pole elektryczne, pole magnetyczne, linie napowietrzne Introduction This work deals with the reduction of the electric and magnetic fields emissions caused by the overhead power lines. The sources of the magnetic and electric fields in the vicinity of the overhead lines are the electrical currents flowing through conductors and charges existing on it. Generally, these fields can be summed with fields induced in the earth or in nearby objects, neglected in this work. In the last decades the increasing public concern about exposure to electric and magnetic fields has been an important issue in most countries around the world. In that sense the relation between the electromagnetic field emissions and the possible induced body currents is often taken as basic restrictions by the international organization like IEEE (Institute of Electrical and Electronic Engineers),[...]

Emissions of electromagnetic fields caused by sagged overhead power lines

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Nowadays people became aware of the overhead lines and their emissions of electromagnetic fields. This work presents a method for calculation of the electric field strength and magnetic field density caused by the overhead power lines at the ground level. The method considers the conductor sagging. It is shown that the sagged conductors can be replaced with the properly placed straight conductors without substantial decrease in accuracy of calculated results. Streszczenie. Obecnie daje się zauważyć wzrost świadomości społecznej istnienia linii elektroenergetycznych napowietrznych i emitowania przez nie pola elektromagnetycznego. Artykuł prezentuje metodę obliczeń natężenia pola elektrycznego i strumienia magnetycznego od linii elektroenergetycznej na poziomie ziemi. Metoda uwzględnia obniżenie (zwis) przewodu. Pokazano, że zwis przewodów może zostać zastąpiony przez właściwie umieszczone proste przewody bez istotnej utraty dokładności. (Emisja pola elektromagnetycznego przez linie elektroenergetyczne przy uwzględnieniu ich zwisu) Keywords: overhead power line, magnetic fields, electric fields, conductor sagging. Słowa kluczowe: linie napowietrzne, pole magnetyczne, pole elektryczne, zwis przewodu Introduction In nowadays, the people become increasingly aware of the overhead power lines presence [1]. One of the reasons for that are the electromagnetic field emissions caused by the overhead power lines which could influence their health. This concern leads to the different objections related to the construction of the new overhead power lines. Additionally, the re-constructions of the existing overhead power lines and even different spatial plans could be under the influence of the people’s objections [1]. Moreover, in the case of overhead power lines not only emissions of electromagnetic fields but also the audible noise emissions are present, which could be a significant parameter. This paper only focuses on emissions of magne[...]

The optimal tracking strategies for two-axis PV system

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This paper deals with two-axis tracking system of photovoltaic (PV) systems. The new method for determining the optimal trajectories of the tracking system is proposed. The optimization goal is the maximum of electric energy production in the PV system, considering the consumption of the tracking system. The determination of the tracking system trajectories is described as a non-linear and bounded optimization problem. The stochastic search algorithm called differential evolution is used as an optimization tool. Streszczenie. Artykuł przedstawia system dwu-osiowego sterownia systemem fotowoltaicznym. Zaproponowana została nowa metoda określania optymalnej trajektorii systemu. Celem optymalizacji jest uzyskanie maksymalnej energii wyprodukowanej w systemie fotowoltaicznym z uwzględnieniem wydatku energii na system sterowania. Określenie trajektorii systemu stanowiło rozwiązanie nieliniowego problemu z ograniczeniami. Jako narzędzie zastosowano algorytm stochastyczny ewolucyjny.(Optymalne strategie sterowania dwuosiowym systemem fotowoltaicznym) Keywords: two axis tracking system, electromechanical system, solar radiation, differential evolution. Słowa kluczowe: dwuosiowy system naprowadzania, system elektromechaniczny, promieniowanie słoneczne, ewolucja różniczkowa Introduction European union‘s directive upon increasing the production of electricity from the renewable energy till 2020 has contributed to the growth of photovoltaic (PV) systems connected to the electric grid. The main elements of the PV systems are solar modules which convert the solar radiation directly into the electricity. The efficiency of this conversion depends on the solar radiation that reaches the surface of the solar cells, the temperature of the solar cells, the impedance matching between the solar modules and dc/dc converters, and the quality of the inverters. This paper focuses on the increase of energy conversion efficiency which can be achieved by t[...]

Control for Grid Connected Small Wind Turbine System DOI:10.15199/48.2015.05.39

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This paper presents a control of a grid connected small wind turbine (SWT) system. The chosen SWT topology consists of a synchronous machine (SM) with excitation winding, a full power back to back converter and an output filter. The control system consists of the hill search type Maximum Power Point Tracking (MPPT) algorithm and the Voltage Oriented Control (VOC). The two control algorithms are interacting over the DCvoltage controller. The proposed control requires small number of measurements that can be reduced to the electrical subsystem of SWT. Streszczenie. W artykule przedstawiono sterowanie małą turbiną wiatrową podłączoną do sieci. System składa się z silnika synchronicznego oraz przekształtnika i filtru wyjściowego. Do sterowania wykorzystano algorytm MPPT i układ VOC. Sterowanie małą turbiną wiatrową podłączona do sieci. Key words: small wind turbine, maximum power point tracking (MPPT), voltage oriented control (VOC), wind energy conversion Słowa kluczowe: mała turbine wiatrowa, algorytm MPPT, przekształtnik Introduction Wind energy is becoming a widely used renewable source of energy. The number of wind turbines connected to the electrical grid is increasing rapidly. 35GW of wind power capacity was added in 2013 alone [1]. Most of this power comes from large wind turbine systems which have very high initial cost and can only be built far away from residential areas [2]. However, the demand for small wind turbines (SWT) is increasing too [3-5]. SWTs usually have rated power of 50kW or less and turbine rotor diameter of 15 meters or less according to IEC. The demand for SWTs is increasing because of easier installation and connection to the grid, smaller initial cost and easier placement within the environment. An array of different topologies of wind turbine (WT) systems can be used for harvesting wind energy. The most widely used topologies include the permanent magnet synchronous machine (PMSG) along with a full powe[...]

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