Verjetnostni izračuni napetostnih razmer ter pretokov energije v elektroenergetskih omrežjih z vključenimi hitrimi regulabilnimi napravami : doktorska disertacija

BOGOVIČ, JERNEJA (avtor), Mihalič, Rafael (mentor)

Doktorska disertacija obravnava področje verjetnostne analize napetostnih razmer in pretokov energije v radialnih omrežjih z vključenimi hitrimi regulabilnimi napravami. Zaradi vključevanja novih naprav v elektroenergetski sistem (EES) se ta neprestano razvija. V zadnjem času je razvoj usmerjen v smeri množičnega vključevanja obnovljivih virov v sistem, ki pa imajo slabo lastnost, da je njihov obratovalni režim pogojen z vremenskimi razmerami in je bolj ali manj nenapovedljiv. Zaradi tega se vse pogosteje uporablja verjetnostni pristop k analizi napetostnih razmer in pretokov energije. Ima pa nepoznavanje obratovalnih razmer za posledico še potrebo po ustrezni regulaciji napetostnih razmer. V nekaterih starejših transformatorskih postajah so vključeni transformatorji, ki omogočajo preklope le v času izključitve. Ker pa se proizvodnja s strani sončnih elektrarn spreminja dnevno, bi bilo treba v takšnih sistemih dnevno spreminjati odcepe. Zato se kot ena izmed smiselnih rešitev postavlja vključitev hitrih regulabilnih naprav v sistem za namen regulacije ustreznih napetostnih razmer. Doktorska disertacija, ki temelji na reševanju problematike napetostnih razmer v radialnih omrežjih z vključevanjem hitrih regulabilnih naprav v sistem in z verjetnostno analizo obratovalnih stanj sistema je v grobem sestavljena iz štirih sklopov. V prvem sklopu so opisani trifazni modeli najbolj pogosto uporabljenih naprav ter metode za izračun napetostnih razmer in pretokov energije. V drugem sklopu smo se dotaknili verjetnostnega računa, osnov statistike in metod za verjetnostni izračun napetostnih razmer in pretokov energije. V tem delu je predstavljena tudi nadgradnja obstoječe metode kumulant za verjetnostni izračun napetostnih razmer in pretokov energije, ki omogoča verjetnostni izračun v radialnih omrežjih. Obstoječa metoda namreč zaradi singularnosti občutljivostne matrike ni uporabna v radialnih omrežjih. V tretjem sklopu doktorska disertacija predstavlja nove modele hitrih naprav, ki so primerni za uporabo v radialnih sistemih v trifazni analizi napetostnih razmer in pretokov energije. Modeli naprav temeljijo na reševanju sistema nelinearnih enačb znotraj reševanja sistema linearnih enačb. S sistemom nelinearnih enačb so zapisane lastnosti hitre regulabilne naprave, sistem linearnih enačb pa predstavljajo enačbe za padce napetosti. Predstavljen je model vzdolžne veje, katerega zastopnik je SSSC, model prečne veje, ki ga simbolizira naprava STATCOM, in njuna kombinacija, ki jo zastopa UPFC. V četrtem sklopu pa so prikazani primeri uporabe novih modelov hitrih regulabilnih naprav in nove nadgrajene metode kumulant. Modele hitrih regulabilnih naprav smo preskusili na treh standardnih testnih sistemih, tj. IEEE 34, IEEE 37 in IEEE 123 vozliščnem testnem sistemu. Vsi trije sistemi so radialni in se za izračun napetostnih razmer ter pretokov energije uporablja U-I metoda. Pri testiranju modelov posamezne naprave smo opazovali število iteracij, potrebnih za dosego želene točnosti rezultata, napetostni odziv sistema na vsiljeno jalovo moč in modele dodatno preizkusili z nadomestno impedanco, ki jo je predstavljala hitra regulabilna naprava. Prav tako smo na standardnih trifaznih sistemih z vključenimi nelinearnimi napravami prikazali uporabo nove nadgrajene metode za verjetnostni izračun napetostnih razmer in pretokov energije. Rezultate verjetnostnih napetostnih razmer in pretokov energije smo podali v obliki tabel in jih primerjali z rezultati, pridobljenimi z metodo Monte Carlo. Na podlagi analize smo ugotovili, da so rezultati obeh metod primerljivi, zato se lahko za verjetnostni izračun napetostnih razmer in pretokov energije v radialnih omrežjih uporabi nova nadgrajena metoda, ki je v primerjavi z metodo Monte Carlo bistveno hitrejša.

• Jezik: Slovenski jezik
• Vrsta gradiva: Doktorsko delo/naloga
• Organizacija: FE - Fakulteta za elektrotehniko
• Leto izida: 2017
• PID: 20.500.12556/RUL-88905
• COBISS.SI-ID: 11682644
• Datum objave v RUL: 30.01.2017

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Probability calculations of voltage conditions and load flow in power systems with included FACTS devices

Izvleček

This doctoral thesis deals with probabilistic power flow in radial distributional systems which include flexible alternating current transmission system devices (FACTS devices). Due to the integration of new devices into the electric power system (EPS), the system is constantly evolving. Recently, development has been oriented towards the massive integration of renewable power plants into the system, but these have the disadvantage that their operating diagram is subjected to weather conditions and inconveniences. As a result, the probabilistic approach is being used increasingly to analyse voltage conditions and power flows. The lack of knowledge of the operating diagram of renewable power plants has resulted in the need for appropriate regulation of voltage conditions. Some of the older substations include transformers which allow tap changes only when disconnected. However, since the production of solar power plants varies daily, it would be difficult to change the taps in such systems. Therefore, a reasonable solution is to include FACTS devices in the system for the purposes of regulating voltage conditions. This doctoral thesis, which presents the solution to the problem of voltage conditions in radial distributional systems by integrating FACTS devices and the probabilistic analysis of operating conditions into the system, is roughly composed of four parts. The first part describes the three-phase models of the most commonly used devices and the methods for calculating voltage conditions and power flows. In the second part, the basic statistics and probability methods for calculating voltage conditions and power flows are illustrated. This section presents the upgrading of the existing method of cumulants for calculating the probabilistic power flow that is suitable for use in radial networks. Due to the singularity of the sensitivity matrix, the basic cumulant method is unsuitable for use in radial networks. The third part of the thesis presents new models of FACTS devices that are suitable for use in three-phase power flow calculations in radial systems. The models are based on the solving of a system of nonlinear equations within the system of linear equations. The system of nonlinear equations describes the features of FACTS devices, while the system of linear equations represents voltage drops. The thesis presents the model of the static synchronous series compensator (SSSC), the static synchronous compensator (STATCOM) and the unified power flow controller (UPFC). In the fourth part, new models of FACTS devices and the new upgraded method of cumulants are evaluated. The models of FACTS devices were tested on three standard test systems, i.e. IEEE 34, IEEE 37 and IEEE 123 node test systems. All three systems are radial, so the U-I method was used for power flow calculation. The number of iterations required to achieve the desired accuracy and voltage response was observed when testing the FACTS devices. The reactance of FACTS devices was calculated from mathematical results and used in simulations to verify the models. The new upgraded method for probability power flow calculations was tested on standard three-phase systems incorporating FACTS devices. The results of the probabilistic power flow are presented in tabular form and compared with the results obtained by the Monte Carlo method. Based on the analysis, it has been established that the results of the two methods are comparable, and therefore the new upgraded method, which is much faster than the Monte Carlo method, may be used for probability power flow calculations in radial networks.