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This paper introduces and illustrates an approach to automatically detecting and selecting “critical” road segments, intended for application in circumstances of limited human or technical resources for traffic monitoring and management. The reported study makes novel contributions at three levels. At the specification level, it conceptualizes “critical segments” as road segments of spatially prolonged and high traffic accident risk. At the methodological level, it proposes a two-stage approach to traffic accident clustering and selection. The first stage is devoted to spatial clustering of traffic accidents. The second stage is devoted to selection of clusters that are dominant in terms of number of accidents. At the implementation level, the paper reports on a prototype system and illustrates its functionality using publicly available real-life data. The presented approach is psychologically inspired to the extent that it introduces a clustering criterion based on the Gestalt principle of proximity. Thus, the proposed algorithm is not density-based, as are most other state-of-the-art clustering algorithms applied in the context of traffic accident analysis, but still keeps their main advantages: it allows for clusters of arbitrary shapes, does not require an a priori given number of clusters, and excludes “noisy” observations.

Summary A new method for synchronous generator static excitation control is proposed in this paper, based on the PI controller and stabilizing feedback action. Compared with the existing solutions, this paper introduces improvements in the system's dynamic performance, robustness, and sensitivity in relation to noise, based on simplified control system structure modification. By introducing the stator voltage stabilizing feedback action, an improved level of dynamic performance is achieved, which also introduces an increased level of robustness. Furthermore, compared with sequential PID and lead–lag compensator based controllers proposed in related standards and technical papers, the system sensitivity in relation to the measurement noise is not compromised, since the differential control action is not included in the proposed controlling structure. The controller design procedure is performed by means of a frequency domain based technique, while its performance is verified by means of simulation and experimental test runs. Copyright © 2015 John Wiley & Sons, Ltd.

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Summary In this paper, a synchronous generator excitation controller based on a novel feedforward control action is proposed. The main purpose of the new feedforward action is to enable a more robust excitation of the synchronous generator operating in varying operating conditions when connected to a power grid, for any superimposed stator voltage controller. Namely, the dynamic performance of the proposed controller is compared with a conventional proportional‐integral (PI) controller, and with the PI controller combined with a feedforward action based on the direct component of the stator current. It is analytically shown that the novel controller improves the robustness when compared to 2 aforementioned solutions. Also, by simulation and experimental tests, it is shown that for the loaded synchronous generator, the novel controller, which is designed to have a similar response speed in open circuit as conventional controllers, exhibits up to 2 times faster dynamic performance.

The paper explores the impact of leasing in agriculture on agricultural production in the Republic of Serbia by means of correlation and regression analysis. The research was conducted in the period between 2006 and 2016. The authorized data from National Bank of Serbia and Statistical Office of the Republic of Serbia were used in the paper. With the aim of carrying out a more comprehensive research, the paper analyzes the impact of leasing placement on the following economic accounts for agriculture: Output of agricultural industry, Intermediate consumption, Gross value added, Agricultural goods output, and Factor income.

Kratak sadržaj: U radu je prikazano tehničko rešenje zamene sistema pobude bloka B1 u TE "Nikola Tesla B" u okviru remonta bloka 2012. godine. S obzirom da generatori u TE "Nikola Tesla B" imaju najveću snagu u elektroenergetskom sistemu Srbije bilo je neophodno postići visoku pouzdanost sistema pobude kako ne bi uticao na prekid procesa proizvodnje električne energije. U tom cilju sistem pobude je realizovan korišćenjem savremenih tehnologija sa redundancijom i u energetskom i u upravljačkom bloku čime je postignuta stopostotna topla rezerva. Pored toga bilo je neophodno prilagoditi sistem pobude povećanju snage agregata sa 618MW na 667.5MW. U radu su navedeni osnovni parametri sistema pobude, opisan je energetski deo, regulacija sistema pobude, paljenje tiristora, akvizicioni sistem, zaštite, upravljanje, merenja i signalizacija.Ključne reči: pobudni sistem / tiristoski most / digitalni regulator / rekonstrukcija / pouzdanost / akvizicija Opšti opisStari sistem pobude bloka B1 u TE "Nikola Tesla B" sistem pobude bio je u upotrebi oko 30 godina, zbog čega su pojedine komponente sistema pri kraju životnog veka. Takođe, bilo je neophodno prilagoditi sistem pobude povećanju snage agregata sa 618MW na 667.5MW. Iz tih razloga, kao i usled zastarelosti i nemogućnosti nabavke rezervnih delova, a sa ciljem povećanja pouzdanosti, urađena je zamena sistema pobude.Sistem pobude je statičkog samopobudnog tipa, odnosno energija za napajanje sistema pobude se dobija sa sabirnica generatora i dovodi se preko pobudnog transformatora na tiristorske mostove sa kojih se ispravljeni napon dovodi rotor generatora. Regulacija napona pobude se vrši u okviru regulatora 47

Kratak sadržaj: U ovom radu dat je prikaz procedure za određivanje vrednosti parametara regulatora pobude na osnovu step promene reference u praznom hodu. Regulator pobude sastoji se od PID regulatora i tiristorskog mosta kao izvršnog organa. U sistemu pobude zatvorene su dve povratne sprege: unutrašnja povratna sprega po struji pobude i spoljašnja povratna sprega po struji pobude u slučaju strujnog regulatora odnosno povratna sprega po naponu statora u slučaju naponskog regulatora. Procedura za određivanje parametara opisuje određivanje ekvivalentnog pojačanja regulatora i tiristorskog mosta. U radu su određeni parametri regulatora na osnovu merenja i snimaka sa agregata A5 u TE ''Kolubara A''.