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Abstract: 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.
Keywords: power system, synchronous generators, oscillations, local modes, eigenvalue analysis
Published in DKUM: 27.03.2025; Views: 0; Downloads: 7
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Abstract: Namen diplomske naloge je bil posodobitev krmilnega sistema avtomatiziranega čistilnega stroja na turbinskem vtoku MHE Melje. Čistilni stroj ima dvoje čistilnih grabelj, ki drsijo po rešetkah navzgor in odstranjujejo naplavine. Grablje poganja hidravlični agregat in s pomočjo elektromagnetnih ventilov upravlja stroj. Vodenje je izvedeno s pomočjo programirljivega logičnega krmilnika. V okviru posodobitve vodenja smo zamenjali strojno in programsko opremo. Programirljivi logični krmilnik Siemens Simatic S7-200 smo zamenjali s Siemens Simatic S7-1200. V programskem okolju TIA Portal V16 smo napisali uporabniški program na osnovi lestvičnega diagrama. Za vnos in prikaz informacij o delovanju stroja smo izdelali tudi grafični vmesnik HMI.
Keywords: Elektrarna, čistilni stroj na turbinskem vtoku, programirljivi logični krmilnik, S7-1200, TIA Portal V16, vmesnik HMI.
Published in DKUM: 20.09.2024; Views: 0; Downloads: 40
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Abstract: The paper deals with the dynamics of a resistance spot welding system. At the core of this system is a transformer, which is powered on the primary side by a pulse-width modulated inverter and has a full-wave output rectifier on the secondary side that provides a direct welding current. The entire system is nonlinear, due to magnetic hysteresis and electronics. The electronics prevent the current from flowing in all parts of the welding transformer at separate time intervals during the voltage supply period; therefore, not all the parameters affect the dynamic of currents and voltages all the time so the system is also time-variant. To design a high-performance welding system and to predict the maximum possible welding current at a specific load, it is necessary to know the welding and primary currents. The leakage inductances of the system can reduce the maximum welding current significantly at higher frequencies and the same load. There are several methods to determine these currents, each with its drawbacks. Measurements are time-consuming, using professional software is expensive and requires time to learn and free open-source software has many limitations and does not guarantee the correctness of the results. The article presents a new, fourth option—a theoretical derivation of analytical expressions that facilitate straightforward and rapid calculation of the welding and primary currents of the resistance spot welding system with symmetrical secondary branches. The derivation of the mathematical expressions is based on the equivalent circuits that describe the system in different operating states. The results of the numerical simulations confirmed the derived expressions completely.
Keywords: DC–DC converters, pulse width modulation (PWM), welding transformers, center-tapped transformers, full-wave rectifier, resistance spot welding (RSW), leakage inductance, analytical modeling, time-variant system, equivalent circuit
Published in DKUM: 08.08.2024; Views: 77; Downloads: 40
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Abstract: V Sloveniji poznamo različne načine vodenja prometa vlakov na železniškem omrežju. V največji meri prevladuje krajevno vodenje, kjer so železniške postaje zasedene s prometnim osebjem. V diplomskem delu je analizirana obstoječa proga Zidani Most–Šentilj z vidika vodenja prometa. Proga Zidani Most–Šentilj je v večini vodena krajevno, za zagotovitev daljinskega vodenja iz centra je potrebna nadgradnja prog in postaj. Analizirane so prednosti in slabosti uvedbe daljinskega vodenja iz centra vodenja prometa. Ugotovili smo, da ukrepi za uvedbo daljinskega vodenja in vključitev daljinskega vodenja prometa vlakov iz centra povečuje varnost potnikov v železniškem prometu, prispeva k zanesljivejšemu delovanju, k zmanjšanju zaposlenih v vodenju prometa ter omogoča večjo prepustnost in zmogljivost proge Zidani Most–Šentilj.
Keywords: železniški promet, daljinsko vodenje železniškega prometa, centralno daljinsko vodenje, Zidani Most – Šentilj
Published in DKUM: 30.01.2024; Views: 507; Downloads: 142
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Abstract: V teoretičnih izhodiščih diplomske naloge je opisan oprtni sistem transporta A ter njegove prednosti in slabosti. Opisani so spremljevalni ukrepi ter tehnologiji RoLa in Flexiwagen. V obstoječih povezavah so opisane povezave oprtnega sistema v srednji Evropi, primeri dobrih praks ter natančen opis obstoječe povezave Maribor Tezno - Wels. V analizi tehnične upravičenosti so opisani kriteriji za tehnično upravičenost, aktivni terminali ter analiza tehnične infrastrukture. V izboljšavah novih železniških povezav so opisane nove železniške povezave od Maribor Tezno do: Brennersee; Budimpešta; Trento; Reka; Salzburg; Beljak; Wörgl in Gorica. Vsaka nova povezava temelji na zahtevanih kriterijih za tehnično upravičenost. Za primerne povezave so opisani rezultati emisijskega kalkulatorja, za neprimerne pa izboljšave proge. Opisani so predlogi ukrepov za izboljšanje delovanja oprtnega sistema A na železniški postaji Maribor Tezno za tehnično upravičene nove povezave. V sklepu je opisano moje osebno mnenje o oprtnem sistemu A iz postaje Maribor Tezno.
Keywords: Oprtni sistem A, Maribor Tezno, terminal, nove železniške povezave, tehnična upravičenost, nakladalni profil, osna obremenitev
Published in DKUM: 16.11.2023; Views: 474; Downloads: 63
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