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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Θεωρία στιγμιαίας ισχύος σε τριφασικά συστήματα με ασύμμετρες και μη ημιτονοειδείς κυματομορφές

Νούσιας, Σωτήριος 07 June 2013 (has links)
Στις μέρες μας, τα Συστήματα Ηλεκτρικής Ενέργειας περιλαμβάνουν μονάδες παραγωγής και φορτία που χρησιμοποιούν συσκευές με ηλεκτρονικά ισχύος σε ολοένα και αυξανόμενο βαθμό. Αυτό έχει σαν αποτέλεσμα να εμφανίζονται στο δίκτυο μη ημιτονοειδείς κυματομορφές τάσεων και ρευμάτων. Ως γνωστόν, υπό ημιτονοειδείς συνθήκες ο υπολογισμός της ενεργού ισχύος, της αέργου ισχύος και του συντελεστή ισχύος αρκούν για την κατανόηση της ροής ενέργειας ενός συστήματος. Παρ’όλα αυτά, σε μη ημιτονοειδείς συνθήκες οι κλασσικές έννοιες της ενεργού και αέργου ισχύος δεν είναι χρήσιμες. Στόχος της συγκεκριμένης διπλωματικής εργασίας είναι η ανάδειξη αυτού του προβλήματος καθώς και η θεμελίωση της θεωρίας στιγμιαίας ισχύος, η οποία αποτελεί βασική θεωρία ανάλυσης των σύγχρονων τριφασικών συστημάτων. / Nowadays, power systems include production units and loads using power electronic devices in an increasing rate. Thus,non sinusoidal voltages and currents appear in the network. In sunusoidal conditions the calculation of active power, reactive power and power factor are sufficient for understanding the energy flow of the system. Although, in non-sinusoidal conditions the classical theory is not sufficient to describe the energy flow in the system. The purpose of this thesis is to highlight this problem and present the instantaneous power theory, which is the basic theory of modern analysis of three phase systems.
2

Representação trifásica de desequilíbrios estruturais e operacionais em sistema de média tensão de distribuição / Three-phase representation of structural and operational unbalances on distribution system

Guilhoto, João Vitor de Araújo, 1983- 06 April 2012 (has links)
Orientador: Anésio dos Santos Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-20T21:30:41Z (GMT). No. of bitstreams: 1 Guilhoto_JoaoVitordeAraujo_M.pdf: 9238872 bytes, checksum: 2872f5a86f13a31cf1c8d3c62089038f (MD5) Previous issue date: 2012 / Resumo: A complexidade crescente dos estudos em sistemas de distribuição demanda uma formulação e modelagem capazes de agregar os desequilíbrios estruturais e operacionais dos sistemas elétricos de distribuição aos resultados das condições operacionais em regime permanente. Neste trabalho, aborda-se a representação trifásica em sistemas elétricos de média tensão de distribuição, considerando as particularidades dos sistemas trifásicos, bifásicos e monofásicos (MRT); e desenvolvendo os modelos dos circuitos, cargas, bancos de capacitores, transformadores e bancos de reguladores de tensão. Visando estabelecer o futuro vínculo dos modelos desenvolvidos com as sistemáticas existentes de determinação das condições operacionais dos sistemas elétricos de média tensão de distribuição, adota-se formulação matricial generalizada de correlação das correntes e tensões nodais. Tal formulação torna possível explorar e analisar os desequilíbrios estruturais e operacionais / Abstract: The increase complexity of power distribution analysis demands formulation and modeling that are capable to integrate structural and operational unbalance to steady state operational conditions. In this work the three-phase representation on distribution systems is addressed taking in account three-phase, two-phase and single-phase systems particularities; and developing the models for lines, loads, capacitor banks, transformers and step-voltage regulators. To achieve the future link between the models and existing techniques to determine the distribution systems operational conditions, it's chosen the formulation based on generalized matrices that establish the correlation of currents and nodal voltages. This formulation makes possible to explore and analyze the structural and operational unbalances / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

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