1. Analysis of synchronous generators’ local mode eigenvalues in modern power systemsJožef Ritonja, Boštjan Polajžer, 2022, izvirni znanstveni članek Opis: New energy sources, storage facilities, power electronics devices, advanced and complex
control concepts, economic operating doctrines, and cost-optimized construction and production of
machines and equipment in power systems adversely affect small-signal stability associated with local
oscillations. The objective of the article is to analyze local oscillations and the causes that affect them in
order to reduce their negative impact. There are no recognized analyses of the oscillations of modern
operating synchronous generators exposed to new conditions in power systems. The basic idea is to
perform a numerical analysis of local oscillations of a large number of synchronous generators in
the power system. The paper represents the local mode data obtained from a systematic analysis of
synchronous generators in the Slovenian power system. Analyzed were 74 synchronous generators
of the Slovenian power system, plus many additional synchronous generators for which data were
accessible in references. The mathematical models convenient for the study of local oscillations
are described first in the paper. Next, the influences of transmission lines, size of the synchronous
generators, operating conditions, and control systems were investigated. The paper’s merit is the
applicable rules that have been defined to help power plant operators avoid stability-problematic
situations. Consequently, boundaries were estimated of the eigenvalues of local modes. Finally,
experiments were performed with a laboratory-size synchronous generator to assess the regularity of
the numerically obtained conclusions. The obtained results enable the prediction of local oscillations’
frequencies and dampings and will be useful in PSS planning.
Ključne besede: power system, synchronous generators, oscillations, local modes, eigenvalue analysis
Objavljeno v DKUM: 27.03.2025; Ogledov: 0; Prenosov: 9
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2. Analysis and improvements of the mechanisms for cross-border interchange and activation of the regulating reserves : doctoral dissertationMarcel Topler, 2022, doktorska disertacija Opis: This Doctoral Thesis deals with the mechanisms for cross-border interchange and activation of the regulating reserves (RRs), i.e., Imbalance Netting Process (INP) and Cross-Border Activation of the RRs (CBRR), between participating Control Areas (CAs), to reduce the costs of balancing energy.
The main objective of INP is to interchange the RRs between participating CAs with opposite signs of interchange power variation. In comparison, the main objective of CBRR is to activate the RRs in participating CAs with the same signs of interchange power variation. Both the INP and CBRR aim to release the RRs and reduce balancing energy as part of the power system's safe operation.
The Thesis's main objective is to analyze the impact of the mechanisms for cross-border interchange and activation of the RRs on mutual oscillations of participating CAs and stability for small disturbances. The Thesis's secondary objective is to analyze the impact of the INP and CBRR on frequency quality, on the provision of Load-Frequency Control (LFC), on balancing energy and unintended exchange of energies between participating CAs.
Frequency quality in Continental Europe (CE) has been declining in recent years, so it is important that the mechanisms for cross-border interchange and activation of the RRs do not further impair its quality.
Both the classic INP and CBRR include a frequency-dependent contribution and, therefore, inherently affect the frequency response of the participating CAs, which is not discussed in the literature. Thus, the impact of the classic INP and CBRR on frequency quality and the provision of LFC is thoroughly evaluated with dynamic simulations of a three-CA test system and eigenvalue analysis of a two-CA system. It is demonstrated that both the classic INP and CBRR reduce the damping of the entire power system.
Therefore, a modified implementation of the classic INP and CBRR is presented, and improved INP and CBRR are proposed, which have no impact on the mutual oscillations of participating CAs and stability for small disturbances.
Furthermore, the dynamic simulations results confirm that the frequency quality can be improved by the classic INP and CBRR, although there are also cases where it can deteriorate. However, the improved INP and CBRR generally improve the frequency quality in all cases. The improved INP and CBRR also enhance the provision of LFC compared to the classic INP and CBRR. Moreover, the improved INP and CBRR reduce the unintended exchange of energies, thus increasing the economic effects of the INP's and CBRR's activation.
The improved INP increases energy exchange, therefore positive economic benefits can be expected in comparison to the system with the classic INP.
However, the improved CBRR reduces energy exchange, therefore positive economic benefits can be expected in comparison to the system with the classic CBRR, since energy exchange is paid by CA via bidding process.
Ključne besede: load-frequency control, imbalance netting, cross-border activation, balancing
energy, regulating reserves, eigenvalue analysis, performance indicators, area control error, rate of change of frequency, control area
Objavljeno v DKUM: 09.03.2023; Ogledov: 594; Prenosov: 118
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3. Li, Hao(PRC-TSI); Lu, Mei(PRC-TSI): The $m$-connectivity index of graphs. (English summary). - MATCH Commun. Math. Comput. Chem. 54 (2005), no. 2, 417--423.Sandi Klavžar, 2006, recenzija, prikaz knjige, kritika Ključne besede: matematika, kemijska teorija grafov, lastna vrednost, Laplaceova matrika, utežen graf, mathematics, chemical graph theory, eigenvalue, Laplacian matrix, weighted graph
Objavljeno v DKUM: 10.07.2015; Ogledov: 37382; Prenosov: 21
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4. Reingold, Omer; Vadhan, Salil; Wigderson, Avi: Entropy waves, the zig-zag graph product, and new constant-degree expanders. - Ann. of Math. (2) 155 (2002), no 1, 167-187Sandi Klavžar, 2003, recenzija, prikaz knjige, kritika Ključne besede: matematika, teorija grafov, produkt grafov, lastne vrednosti, matrika sosednosti, mathematics, graph theory, graph product, adjacency matrix, eigenvalue
Objavljeno v DKUM: 10.07.2015; Ogledov: 1061; Prenosov: 25
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5. The mass spectrum of high energy elementary particles via El Naschie's [epsilon][sup]([infinity]) golden mean nested oscillators, the Dunkerly-Southwell eigenvalue theorems and KAMLeila Marek-Crnjac, 2003, izvirni znanstveni članek Opis: Predstavimo klasični mehanični model in ustrezne izrazitve teoretičnih mas elementarnih delcev, pri čemer so tudi vsebovane mase kvarkov, ki so povezane z lastnimi vrednostmi kombiniranih nihajočih množic. Tukaj uporabimo Southwellov in Dunkerlyev izrek. Zlati rez ima posebno vlogo v KAM-ovi teoriji, obravnavan je pa tudi naš model.
Ključne besede: KAM-ova teorija, Dunkerly-Southwellovi izreki o latnih vrednostih, zlati rez, matematika, KAM theory, Dunkerly-Southwell eigenvalue theorems, golden mean
Objavljeno v DKUM: 10.07.2015; Ogledov: 887; Prenosov: 43
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6. Handbook of semidefinite programming : theory, alorithms, and applicationszbornik Ključne besede: operacijsko raziskovanje, optimizacija, linearno programiranje, teorija, algoritmi, aplikacija, programiranje, konvekcija, matrike, teorija odločitev, matematika, geometrija, matematično programiranje, Jordanske derivacije, meritve, metode, aproksimacija, kombinatorika, struktura, poslovne odločitve, modeli, semmidefinite programming, convex analysis, symmetric matrices, duality, eigenvalue, embedding theorems, multipliers
Objavljeno v DKUM: 01.06.2012; Ogledov: 2940; Prenosov: 96
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7. Convex analysis and nonlinear optimization : theory and examplesJonathan M. Borwein, Adrian S. Lewis, učbenik za višje in visoke šole Ključne besede: semmidefinite programming, convex analysis, symmetric matrices, duality, eigenvalue, embedding theorems, multipliers, polyhedra, polyhedral convex functions
Objavljeno v DKUM: 01.06.2012; Ogledov: 2126; Prenosov: 44
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8. Wave motion in infinite inhomogeneous waveguidesIgor Špacapan, Miroslav Premrov, 2003, izvirni znanstveni članek Opis: The analysis of wave motion in infinite homogeneous waveguides, having a complicated cross-section and/or an irregular inclusion, is a rather difficult task for the majority of available methods, especially when striving for accurate results. In contrast, this presented procedure performed in the frequency domain, is simple to apply. It yields correct results because the radiation conditions are considerably accurately satisfied, and it offers a clear parametric insight into wave motion. This procedure uses the FE modelling of an analysed section of the waveguide. It is based on the decomposition of wave motion, distinguishing propagating and non-propagating wavemodes by solving the eigenvalue problem. The presented examples demonstrate the effectiveness of this procedure, whilst a comparison between computed and analytical results demonstrates its accuracy.
Ključne besede: waves, wavemodes, waveguides, inhomogeneity, finite element method, parametric analysis, radiation conditions, eigenvalue problem, frequency domain
Objavljeno v DKUM: 01.06.2012; Ogledov: 2340; Prenosov: 67
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