20.500.12556/RUL-84372 NAPETOSTNA STABILNOST V FLEKSIBILNIH ELEKTROENERGETSKIH SISTEMIH VOLTAGE STABILITY IN FLEXIBLE AC TRANSMISSION SYSTEMS Današnji elektroenergetski sistemi se vse bolj soocajo s posledicami prehajanja na tako imenovane nizkoogljicne proizvodnje elektricne energije (proizvodnja iz vetrnih in soncnih elektrarn in zapiranje termo in nuklearnih elektrarn), kar znatno vpliva na prerazporeditev pretokov moci, v obstojecih elektroenergetskih omrežjih. Ena bistvenih komponent fleksibilnih elektroenergetskih sistemov, ki je pogoj za integracijo vecjega deleža obnovljivih virov elektricne energije, so elektronske naprave, ki jih imenujemo tudi naprave FACTS. Naprave FACTS lahko ustrezno in dinamicno regulirajo parametre sistema (pretoke energije, napetosti), kar omogoca sigurno obratovanje sistema tudi, ko se njegove spremenljivke približajo dopustnim mejnim vrednostim. Na zacetku so naprave FACTS, zaradi dimenzij in cene, dajale predvsem teoreticne odgovore na probleme v elektroenergetskih sistemih. Danes, ko lahko stroški razpadov elektroenergetskih sistemov narastejo na milijarde evrov in so osnovni gradniki FACTS - mocnostne komponente (tiristorji) tehnološko in cenovno bolj dostopne, je tehnologija FACTS stalnica v elektroenergetskih sistemih. Naprave FACTS odlikujeta: hitrost delovanja (perioda obratovalne frekvence ali celo manj), možnost vplivanja na admitance omrežja in fazorje napetosti, kar posledicno vpliva na pretoke energije. Glede na konstrukcijo, nacin delovanja in modele v disertaciji locimo: • regulabilna serijska kompenzacija (angl. Controllable Series Compensation – CSC), • staticni sinhronski serijski kompenzator (angl. Static Synchronous Series Compensator – SSSC), • staticni VAr kompenzator (angl. Static Var Compensator – SVC), • staticni sinhronski kompenzator (angl. Static Synchronous Compensator – STATCOM) in • univerzalni precni transformator (angl. Unified Power Flow Controller – UPFC) • in druge, ki jih disertacija ne obravnava. Prenos energije po visokonapetostnih vodih je, poleg staticnih parametrov omrežja (admitance), odvisen od fazorjev napetosti na zacetkih in koncih vodov, lokacije bremenskih vozlišc in proizvodnih virov. Po visokonapetostnih vodih lahko, kljub zadostnim proizvodnim kapacitetam, prenašamo le omejeno kolicino delovne in jalove energije, kar pomeni, da za zanesljivo oskrbo z elektricno energijo ni pomembna le zadostna proizvodnja, temvec tudi njena ustrezna razporeditev. Na ustrezno razporeditev proizvodnih enot v elektroenergetskih sistemih je zelo obcutljiva (lokalna) izravnava porabe in proizvodnje jalove moci, saj jo je treba proizvesti cim bližje mestu porabe. Odstopanje porabe in proizvodnje jalove moci lahko vodi v napetostno nestabilnost, ki v najneugodnejšem slucaju povzroci razpad sistema. Posledice odmevnih razpadov elektroenergetskih sistemov, zaradi napetostne nestabilnosti, so še vedno v spominu in nam služijo kot svarilo, da je treba pri nacrtovanju in obratovanju elektroenergetskih sistemov predvideti možnost njenega nastanka. Napetostno stabilnost obravnavamo glede na razsežnost in trajanje: pocasna in hitra napetostna nestabilnost. Pri obravnavi pocasne napetostne stabilnosti zadostuje reševanje algebrajskih enacb za izracun fazorjev napetosti in uporaba metod, ki ne upošteva casovne komponente. S stališca staticne (angl. steady state) analize, hitrost delovanja naprav FACTS ne pride do izraza, saj se pojavu pocasne napetostne nestabilnosti lahko izognemo z ustreznimi (rocnimi) ukrepi, ce so ti na voljo. Hitra napetostna nestabilnosti, ki je precej manj raziskana in precej manj publicirana, temelji na dinamicnih karakteristikah modelov bremen in diferencialno algebrajskih enacbah. Nekatere raziskave nakazujejo, da je možen pristop k analizi napetostne stabilnosti tudi z direktnimi metodami, ki so dobro raziskane za analizo kotne stabilnosti. Doktorska disertacija obravnava podrocje napetostne stabilnosti, z vidika možnosti uporabe direktnih metod pri oceni napetostne stabilnosti in vpliva naprav FACTS na napetostni profil v prenosnih elektroenergetskih sistemih. Disertacija pokaže primernost direktnih metod za analizo napetostne stabilnosti in nujnost izbire ustrezne casovno odvisne (dinamicne) karakteristike bremena. Naprave FACTS lahko spreminjajo napetostni profil prenosnega omrežja, kar pokažemo z izpeljavo enacb odvisnosti napetosti v PQ vozlišcu, na osnovnih modelih sistemov z napravami FACTS. Uporaba analiticnih enacb omogoci hiter in tocen izracun PU krivulj za poljubno vrednost regulabilnih parametrov naprav FACTS. V disertaciji pokažemo, da površina podrocja, ki ga opišejo PU krivulje med mejami dopustnih napetosti, lahko služi za kriterij ocene ucinkovitosti naprave FACTS pri zagotavljanju napetostne stabilnosti. Today's electric power systems are increasingly facing the consequences of a project, i.e., low-carbon electricity production (the increase of electricity production from wind and solar power plants, the closing of coal and nuclear power plants), which has a significant impact on the redistribution of power flows in the existing electric power networks. One of the essential components of smart grids (which is a prerequisite for the integration of more renewable energy in modern electric power systems) is the electronic devices that can properly and dynamically regulate the parameters of the electric power systems (power flows, voltage). FACTS technology has been developed, but at the beginning, mainly because of the price, it only provided more or less theoretical answers to the problems in an EPS. Today, when the costs of blackouts in electric power systems can rise to billions of dollars and power-thyristor technology is more affordable, FACTS technology is often employed in electric power systems. The FACTS devices are distinguished by their operating speed (operating frequency cycle or even less), the possibility to change the network admittance and the voltage phasors, which in turn affects the power flow. Depending on the construction, operating principles and models, FACTS devices may be classified as: • controllable series compensation – CSC, • static synchronous series compensator – SSSC, • static var compensator – SVC, • static synchronous compensator – STATCOM, • unified power flow controller – UPFC • and the others which are not the subject of this thesis. The power flow through transmission lines depends not only on the static network parameters (admittances), but also on the location of the load centres and on the location of the production. Despite sufficient electricity production, the transmission lines can transmit only a limited amount of active and reactive electric power, which means that not only adequate production, but also its proper location, is important for a reliable supply. The equilibrium for the production and consumption of reactive power is greatly influenced by the location of the production units in the electric power system, which should be as close as possible to the place of consumption. A lack of reactive power can lead to voltage instability, which, in the worst case, can cause a system blackout. The consequences of significant blackouts due to voltage collapse are still in the memory and they can occur again if they are not predicted during the planning and operation of a power system. Voltage stability is considered in terms of the extension of the disturbance (small, large disturbance) and the duration: long-term and short-term voltage instability. Long-term voltage instability includes the operations of on load tap changers, thermostatically controlled loads, generator excitation limiters, and the duration is from a few minutes to a few hours. When dealing with such a slow phenomenon the solving of algebraic equations for a calculation of the power flow is sufficient, as is the use of methods that do not take into account the time component. In terms of the steady-state analysis the speed of FACTS devices is not relevant, as the occurrence of a slow voltage instability can be avoided by appropriate (“hand”) measures, if they are available. Short-term voltage instability is based on time dependant (dynamic) load models and differential algebraic equations. Some researches show the possibility of implementation of the direct methods into short-term voltage analysis, which are well-known approach in the (angle) transient-stability studies. The doctoral thesis treats the topic of voltage stability in terms of the possibility to apply the direct methods for the voltage stability estimation and the impact of FACTS-devices on the voltage profile in an electric transmission power system. Direct methods for the analysis of the transient-stability of power systems with FACTS devices are well-studied, so we focused on their suitability for analysis of voltage stability by selecting the appropriate time-dependant (dynamic) load characteristics which is explained in the present thesis. FACTS devices can vary the voltage profile of the transmission network, which we proved with the analytical derivation of equations based on power system model with FACTS devices. Application of analytical equations allows fast and accurate calculation of PU curves for any value of controllable parameters of FACTS-devices. In the thesis is shown that the surface area in PU diagram covered between the boundaries of the permissible voltage can be used for the evaluation criteria of the effectiveness of FACTS-device for achieving a stable voltage profile. elektroenergetski sistem napetostna stabilnost PU krivulje direktne metode energijske funkcije naprave fleksibilnega prenosnega sistema FACTS electric power system voltage stability PV curves direct methods energy functions FACTS true false false Slovenski jezik Angleški jezik Doktorsko delo/naloga 2016-08-17 13:55:02 2016-08-17 13:55:10 2023-06-16 08:45:52 0000-00-00 00:00:00 2016 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 1970-01-01 36601 11483220 Gasperic_Samo_-_NAPETOSTNA_STABILNOST_V_FLEKSIBILNIH_ELEKTROENERGETSKIH_SISTEMIH.pdf Gasperic_Samo_-_NAPETOSTNA_STABILNOST_V_FLEKSIBILNIH_ELEKTROENERGETSKIH_SISTEMIH.pdf 1 21323D5DA0822EC730E25634198B986D 082c57403d55fe11fefc6fc54b820eef7daa8de4e3b2204e389c750c22766b11 e5920fe8-a1b0-11eb-a523-00155dcfd717 20.500.12556/rul/e49e71e3-bcce-4197-8b06-e0a102dd0237 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=87475 Fakulteta za elektrotehniko 0 0 0