| Title | STABILNOST PRETKAOTIČNIH USTALJENIH STANJA FEROREZONANTNOG KRUGA |
| Author | Igor Lukačević |
| Mentor(s) | Kruno Miličević
|
| Abstract | Ferorezonancija se pojavljuje u elektroenergetskim sustavima se kao neželjeno stanje sustava koje može dovesti do oštećenja pojedinih dijelova sustava. Osnovna komponenta ferorezonantnog dijela elektroenergetske mreže je nelinearna zavojnica sa željeznom jezgrom koju u stvarnosti predstavljaju energetski i mjerni transformatori i kompenzacijske prigušnice. Opisano je nekoliko karakterističnih primjera ferorezonantnih dijelova elektroenergetske mreže koji se mogu modelirati jednostavnim RLC krugom kojega nazivamo ferorezonantnim krugom.
U ferorezonantnom krugu mogu se pojaviti različite vrste ustaljenih stanja ovisno vrijednosti bifurkacijskog parametra. Kroz slijed bifurkacija udvostručavanja periode pojavljuje se i kaotično ustaljeno stanje. Identifikacija ustaljenih stanja provedena je s pomoću frekvencijske analize varijabli stanja, Poincaréovih slika i bifurkacijskih dijagrama.
Opisana je grafo-analitička metoda analize stabilnosti pretkaotičnih ustaljenih stanja ferorezonantnog kruga temeljena na metodi inkrementalne opisne funkcije. Pomoću ove metode objašnjena je pojava ferorezonantnog skoka kao nestabilnost sustava na frekvenciji poticaja. Slijed pretkaotičnih bifurkacija objašnjen je kao slijed nestabilnih stanja i oscilacija na točno određenim harmonicima osnovne frekvencije poticaja.
Model zavojnice sa željeznom jezgrom ima ključan utjecaj na ponašanje ferorezonantnog kruga. Definirani su bitni parametri modela nelinearne zavojnice (ekvivalentna impedancija, početna ili linearna admitancija, ovojnica prijenosne funkcije) na osnovu kojih se izrađuje portret nelinearne komponente. Portret nelinearne komponente služi kao podloga za analizu stabilnosti ferorezonantnog kruga i predviđanje ferorezonancije. Analiza mogućnosti nastanka ferorezonancije provedena je na dva praktična primjera elektroenergetskih postrojenja.
Modeliranje zavojnice sa željeznom jezgrom svodi se na dvije bitne komponente: modeliranje nelinearne karakteristike induktiviteta i modeliranje otpora koji predstavlja gubitke u jezgri. Parametari modela zavojnice sa željeznom jezgrom određuju se na osnovu mjerenja U-I-P karakteristike. Predložena je mjerna metoda za izravno mjerenje ekvivalentne impedancije te način modeliranja zavojnice sa željeznom jezgrom na osnovu ekvivalentnog induktiviteta i ekvivalentne vodljivosti. |
| Keywords | ferroresonance ferroresonant circuit chaos stability steady-state bifurcation incremental describing function iron-cored coil |
| Parallel title (English) | Stabilitiy of pre-chaotic steady states of ferroresonant circuit |
| Committee Members | Denis Pelin (committee chairperson)
Ivo Uglešić (committee member)
Srete Nikolovski (committee member)
Robert Cupec (committee member)
|
| Granter | Josip Juraj Strossmayer University of Osijek
Faculty of Electrical Engineering, Computer Science and Information Technology Osijek |
| Lower level organizational units | Department of Power Engineering
Chair of Power Systems and Substations |
| Place | Osijek |
| State | Croatia |
| Scientific field, discipline, subdiscipline | TECHNICAL SCIENCES
Electrical Engineering
Power Engineering
|
| UDK | 621.3
APPLIED SCIENCES. MEDICINE. TECHNOLOGY
Electrical engineering |
| Study programme type | university |
| Study level | postgraduate |
| Study programme | Postgraduate doctoral study programme; branch Power Engineering and Communications, branch Informatics |
| Study specialization | branch Power Engineering and Communications |
| Academic title abbreviation | dr.sc. |
| Genre | doctoral thesis |
| Language | Croatian |
| Defense date | 2015-09-30 |
| Promoted date | 2016-04-09 |
| Parallel abstract (English) | An initiation of ferroresonance in the electrical power networks is an undesirable phenomenon with possible harmful consequences. The main component of a ferroresonant part of the electrical power network is a nonlinear iron-cored coil, which represents a power transformer, a wound potential transformer or a shunt reactor. A few typical examples of ferroresonant parts of the electrical power networks are described which can be modeled with a ferroresonant circuit as a simple RLC circuit.
Varying one of the parameters of the ferroresonant circuit, called bifurcation parameter, several steady-states types can be obtained. Furthermore, a chaotic steady-state can be obtained following a sequence of period doubling bifurcations, known as period doubling route to chaos. Ways of identification and presentation of steady-states are described: harmonic content of a state variable, Poincáre maps and bifurcation diagrams.
A grapho-analytical analysis method of stability of pre-chaotic steady states is described. The method is based on the incremental describing function method. A phenomenon of ferroresonant jump is explained by instability of the system on the fundamental frequency of excitation. The pre-chaotic bifurcation sequence is explained by sequence of unstable states and oscillations on certain frequencies.
The model of iron-cored coil has substantial impact on the behavior of the ferroresonant circuit. A graphical portrait of a nonlinear component is created which is based on substantial parameters of nonlinear coil (equivalent impedance, linear admittance, transmission function envelope). The graphical portrait of nonlinear component is used to analyze ferroresonant circuit and predict an initiation of the ferroresonance. The ferroresonance possibility analysis on two practical examples of real electrical power systems is carried out.
There are two component of iron-cored coil model: nonlinear inductor representing saturation effect and nonlinear resistor representing coil loss. The commonly used method to obtain the model parameters is based on standard U-I-P measurements. The method of measuring of equivalent impedance is proposed. According to such measurements the model of iron-cored coil can be obtained involving equivalent inductance and equivalent conductivity. |
| Parallel keywords (Croatian) | ferorezonancija ferorezonantni krug kaos stabilnost ustaljeno stanje bifurkacije inkrementalna opisna funkcija zavojnica sa željeznom jezgrom |
| Extent | 132 |
| Version | accepted version |
| Resource type | text |
| Access condition | Open access |
| Terms of use |  |
| Note | accepted version |
| URN:NBN | https://urn.nsk.hr/urn:nbn:hr:200:859456 |
