Hi Simon, ich schreib mal auf Deutsch, das ist einfacher nachzuvollziehen. Naja ich hatte erstmal gar keinen Trafo modelliert, sondern eben nur einen Generator erstmal als Einspeisung auf 230V (quasi den Netzanschluss 'hinter' den Trafo verlegt). D.h. ich hab bisher gar keine Übersetzungsverhältnisse drin, durch die ich die Impedanzen transformieren müsste. Ich wollte das ganze Netz in 230V rechnen, um es nicht zu verkomplizieren. Der Generator stellt eben nur die Energieeinspeisung zur Verfügung. Probleme wie begrenzte Scheinleistung eines Trafos/Trafoimpedanzen etc. lass ich erstmal raus. Ich wollt eben einen Fixpunkt mit 230V direkt generieren, da Trafobetrachtungen für den ersten Einstieg in die Spannungshaltungsrechnung erstmal zum Einstieg zweitrangig sind.
IN ENGLISH: At first step i didn't model a transformator. The energy injection was simplified modeled as a balancing generator directly at 230V. So there's no transformation of impedances neccessary as far as I can see. I wanted to work only with one base voltage for the whole net, because only the low voltage network has to be analyzed. So I tried to generated the most simple case in order to expand the model afterwards. At the moment the "getting-Started"-model consists only of two busses, one branch, one load on a bus and one generator. So the balancing generator should only the represent the injected power of a real transformator, which wasn't modeled at first step. Sincerely/Grüße, Oliver Kopp -----Ursprüngliche Nachricht----- Von: "Simon Schneider" <[email protected]> Gesendet: 10-Nov-2011 11:29:04 An: "MATPOWER discussion forum" <[email protected]> Betreff: Re: Question about MATPOWER / LV >Hi Oliver, > >did you consider that the chosen base voltage has to be transformed >depending in which voltage level you are calculating? > >If you choose e.g. baseMVA = 1MVA and baseV = 20 kV, but your cable is >on the 10 kV side of the transformer, you have to calculate the >impedance of the transformer, rated to the 10 kV side and the cable >impedance with a base voltage of 10 kV. EXCEPTION: If the transformer >has a "Übersetzungsverhältnis" different from 1/2 (in this case) you >have to consider this also. If your chosen Voltage is 20 kV und the >ratio is 1/3, then the rated voltage would be 20/3 kV. > >Sincerely/Grüße >Simon >Am 10.11.2011 11:05, schrieb [email protected]: >> Dear Sir or Madame, >> >> I'm a student at the Otto-von-Guericke University in Magdeburg, Germany and >> I'm about to get started in using Matpower for some network analysis >> problems in Low Voltage networks (230V rms). I try to calculate how the >> voltages at the busses/nodes change by adding more decentral energy sources >> like photovoltaics. I tried to use Matpower and have got some problems. It >> would be very nice if you could give me some advice in solving my modelling >> problem. I'd be very happy about any help. >> >> >> At first view Matpower seems to be usefull for solving these problems. At >> first step I tried to build a network of only to busses (#01 to represent a >> energy source (transformator from medium voltage to low voltage, modelled as >> a generator) (#02: 100kW Load) in order to get to know Matpower itself. But >> I found a problem, which I can't solve right now: >> I have to set a baseMVA-Value and a base voltage. So I decided for some >> values. The lower the chosen MVA-Value the bigger the chance that the >> iteration won't converge. But in Low-Voltage I can't use some GVA or >> TVA-Values just in order to get it work, can't I?! >> For the Impedance of the branch, connecting both busses, I calculated values >> for a 300m piece of cable. Than I devided the Impedance-values by the >> baseImpedance in order to get p.u. Impedances as claimed by Matpower. The >> baseimpdance was calculated by Basevoltage * Basevoltage / Base power >> (MVA-Value) as written in my collection of formulas. >> But the impedances of the branch were so small that there's almost no >> powerloss and no decrease in the voltage between bus 1& 2. >> I tried to scale up my Lowvoltage problem by setting 100MW for (real) 100kW >> and 230kV for 230V(real). But it didn't work. The modell didn't converge or >> gave wrong values back. So I want to know whats the best way to modell my >> Low-Voltage-problem in Matpower? >> >> In order to give you an idea, what I tried, here are some very short >> .m-files, which show my Problem at the decripted example. The file >> startbaresSkript is a runable file, which calculates the impedances and than >> passes them into the modell. The modell itself is just set up with some >> 'random' values just to create the structure and fill in correct values >> afterwards by using the "startbareSkript". >> Nomenclature: In Germany "U" is used for Voltage and the "_bez" in variable >> names express that Base-Values for p.u. - calculations are ment. >> I also tried for the Calculation of the base impedance to scale down the >> MVA-Base and the Base-Voltagein (kV) down to SI-measurement units, but it >> did'nt work either. >> Somehow I did'nt found a good way to cope with low voltage networks >> decripted in the manual. >> >> Can you help me?! Which settings have to be done to calculate a >> low-voltage-network with matpower? >> The concrete Data are: >> 230 V (RMS) between phase and neutral Line, 3 phase-model (Star-circuit, >> symmetric Loads and generations!) >> Loadvalues somewhere between 2-100 kW at each bus (fix Load/ fix generation) >> and a balancing generator representing the connected network to upper >> Voltage-Network-Layers... >> >> I would be really happy, if you could give me some hints, ideas or tipps to >> cope with that problem. >> Thanks a lot! >> >> Yours sincerely, >> Oliver Kopp >> Germany >> >> >> >> >> >> >> >> >> >> ___________________________________________________________ >> SMS schreiben mit WEB.DE FreeMail - einfach, schnell und >> kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192 > > ___________________________________________________________ SMS schreiben mit WEB.DE FreeMail - einfach, schnell und kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc=021192
