Utjecaj magnetskog međudjelovanja uzdužne i poprečne osi na dinamičke karakteristike sinkronog generatora u autonomnom radu : doktorska disertacija - Mirošević, Marija; Maljković, Zlatko (Zagreb : M. Mirošević ; Fakultet elektrotehnike i računarstva, 2005)
U radu se analizira utjecaj magnetskog međudjelovanja uzdužne i poprečne osi na dinamičke karakteristike sinkronog generatora u autonomnom radu. Analiza dinamike sinkronog generatora je zanimljiva kod malih, izoliranih električnih mreža kao što je npr. brodska električna mreža u kojoj je glavni izvor električne energije dizelski agregat. Direktno uklapanje većih asinkronih motora na izoliranu električnu mrežu predstavlja značajno udarno opterećenje. Za potrebe analize dinamike sinkronog generatora razvijen je matematički model kojeg čine: dizelski motor, sinkroni generator i aktivno trošilo-asinkroni motor.
Razvijen je matematički model sinkronog generatora s uvedenim zasićenjem i međudjelovanjem uzdužne i poprečne osi. Primjenjuje se pristup s jednim faktorom zasićenja, neizotropni stroj s istaknutim polovima nadomješta se jednakovrijednim izotropnim. Ovaj pristup omogućuje da se uzme u obzir doprinos željeza na način da, kod većeg nivoa zasićenja, postaje veći «prividni zračni raspor». Na taj način, zadržan je isti koncept koji se koristi u klasičnoj teoriji električnih strojeva a utjecaj «prividnog zračnog raspora» vodi na definiciju varijabli koje se ne javljaju u teoriji nezasićenih strojeva.
Matematički model asinkronog motora opisuje stroj s uvedenim zasićenjem i magnetskim međudjelovanjem uzdužne i poprečne osi.
Sinkroni generator i asinkroni motor modeliraju se tako da su za varijable odabrane struje svih namota.
Za analizu dinamike kombiniranih sekvenci zaleta asinkronih motora na sinkroni generator u autonomnom radu formiran je matematički model kojeg čine: dizelski motor, sinkroni generator, mehanička veza na mjestu spajanja i dva neregulirana asinkrona motora koji se napajaju izravno sa stezaljki sinkronog generatora. Mehanička veza na mjestu spajanja dizelskog motora i sinkronog generatora razmatra se kao rotirajući sustav sa dvije koncentrirane mase, jedna na strani dizelskog motora, druga na strani rotora sinkronog generatora. Matematičko modeliranje rotacijskog gibanja ovih masa omogućuje izračun njihovih različitih kutova zakreta odnosno torzijskog moment u mjestu spajanja, koji se javlja pri kombiniranim sekvencama zaleta asinkronih motora na sinkroni generator u autonomnom radu.
Rezultati dobiveni simulacijom za slučaj zaleta asinkronog motora na neopterećeni sinkroni generator pokazuju dobro slaganje s rezultatima dobivenim mjerenjem.
Za proračun elektroagregata pri udarnim promjenama opterećenja korišten je programski paket «MATLAB-SIMULINK».
Ključne riječi:
zasićenje, modeliranje zasićenja, magnetsko međudjelovanje uzdužne i poprečne osi, o zasićenju ovisne reaktancije, dinamika, torzijska dinamika, dizelski agregat, sinkroni generator, asinkroni motor, torzijske oscilacije.
The influence of cross-saturation on dynamics of a synchronous generator in autonomous operation is analyzed. Dynamic conditions of generator-units are interesting in the case of smaller, often isolated electrical grids. The electrical grids on ships have such units with a diesel engine and a synchronous generator as sources. The connection of bigger induction motors to the ship's grid with such sources is the most difficult transient regime for units.
In order to analyze the dynamics of generator-units a unique mathematical model of the integral motor drives has been developed consisting of a diesel engine, a synchronous generator and an induction motor as an active consumer.
The mathematical model of a saturated salient pole synchronous generator is developed. The cross-magnetizing phenomenon in the saturated synchronous machine (the magnetic coupling between its direct and quadrature axis) is included. The saturation itself is accounted for by means of a single saturation factor approach, and an anisotropic salient pole machine is converted into an equivalent isotropic one. One can imagine that a fictitious variable air gap exists which is a function of the magnetization current. This will allow taking into account the contribution of the iron in the sense that, the greater the saturation level, the greater the «effective» airgap becomes. It is possible to use the same concepts, which are used in classical theory. The influence of the «effective» airgap will lead to the definition of the variables, which do not appear in the theory of the non-saturated machine.
The induction motor is modeled as a saturated machine. The method of main flux saturation modeling is used. The cross-saturation effect is explicitly presented in the model.
In the transient dq axis model of a synchronous generator, as well as in the induction motor model, all winding currents are selected as state space variables.
In an isolated electrical grid the dynamics of generator-units during start-up of the induction motor drives is interesting. Starting the other induction motor at the time when the transition regime of the previously connected motor is not terminated is particularly difficult situation due to electricity loads and also due to torsional strains in the shaft lines. The mechanical coupling of the diesel engine and the synchronous generator is considered to be a rotating system with two concentrated masses connected by elastic coupling. In the transients, the masses of generator rotor and diesel engine rotate at different speeds, allowing thus the analysis of the torsional dynamics in the coupling.
The results obtained by numerical calculation indicate that, compared to the results of measurements, the established mathematical model can be applied with sufficient certainty.
The analysis of the dynamics of the generator-unit at impact load–direct-on-line starting of induction motors was performed by the application of program package “MATLAB-SIMULINK”.
Keywords:
saturation, saturation modeling, cross-coupling, saturated reactances, dynamics, torsional dynamics, diesel generator-unit, synchronous generator, induction motor, torsional oscillation.
Bibliografija str. 146-148.