Dear all, in my work I'm trying to validate a module that creates a mpc with required grid information (buses, topology information, loads, ...). Therefore I have two questions related to the correct modelling of the MATPOWER case file.
1) After some adjustments of the model, I receive very accurate results for the DC power flow in matpower compared with a commercial powerflow tool. The decisive setting was the neglection of the parameters in the TAP column for the transformers. The only place where the TAP column is considered for the DC power flow is inside the function makeBdc below (line 64/65). ____________________________________________________________________________________ [Bbus, Bf, Pbusinj, Pfinj] = makeBdc(baseMVA, bus, branch ... stat = branch(:, BR_STATUS); %% ones at in-service branches b = stat ./ branch(:, BR_X); %% series susceptance tap = ones(nl, 1); %% default tap ratio = 1 i = find(branch(:, TAP)); %% indices of non-zero tap ratios tap(i) = branch(i, TAP); %% assign non-zero tap ratios b = b ./ tap; _____________________________________________________________________________________ After I received the results, I'm still trying to understand the influence of the column TAP (the transformer off nominal turns ratio). According to my actual understanding of the DC power flow only the reactance has an influence on the resulting flows. May someone be so kind to explain me the consideration of the TAP column in the makeBdc-function. I already found the old post here but would like to understand it even better (https://www.mail-archive.com/[email protected]/msg00320.html). 2) My second question is related to a proper validation of the AC-power flow. Here I have an issue with the modelling of transformers as I get different results between MATPOWER compared to a commercial powerflow tool. As I describe above the result for the DC-power flow are already quite accurate. Below I show the same input data for the transformer. It is a 2-winding transformer connecting two different voltage levels without any shifting. I'm trying to validate the AC-power flow in a small test grid with five nodes and the slack at "NODE2_21". ----- 2 WINDING TRANSFORMER BLOCK ----- _________1_________2_________3_________4_________5_________6_________7_________8_________9 Node 1 |Node 2 |O|S|U1 |U2 |Sn |R(Ohm)|X(Ohm)|B(uS) |G(uS) |I(A) |Element Name| ##T NODE5_81 NODE2_21 1 0 347.0 242.0 240.0 1.1200 44.100 -28.0000 1.0000 400 TR-1 To calculate the right values for the branch matrix I use the following values from the depending transformer: - baseKV_from = 347 kV - baseMVA = 100 MVA - zbase_from = basekV_from^2 / baseMVA - BR_R = 1.12 (Ohm) / zbase_from - BR_X = 44.1 (Ohm) / zbase_from - BR_B = -28 (uS) * 10^-6 * zbase_from My results for the branch matrix are - BR_R = 0,00093 - BR_X = 0,03662 - BR_B = -0,03371 Without modelling a load/generation at node "NODE5_81" I receive quite different results in voltage magnitude/angle. - MAPTOWER o VM = 1,04480948; VA= 0,000897843 - Commercial powerflow tool o VM = 0,998756671; VA = -0,000364748875 I suppose that it has do something with the modelling of the transformer losses in matpower. But I don't have a clue how to get more accurate results. I also tried the approach to model the losses as suggested here (https://www.mail-archive.com/[email protected]/msg02291.html). If someone can give me a hint where to look at, I would be very thankful! Thank you very much. With kind regards, Tobias Hoffmann Wichtiger Hinweis: Die Information in dieser E-Mail ist vertraulich. Sie ist ausschlie?lich f?r den Adressaten bestimmt. Sollten Sie nicht der f?r diese E-Mail bestimmte Adressat sein, unterrichten Sie bitte den Absender und vernichten Sie diese Mail. Vielen Dank. Unbeschadet der Korrespondenz per E-Mail, sind unsere Erkl?rungen ausschlie?lich final rechtsverbindlich, wenn sie in herk?mmlicher Schriftform (mit eigenh?ndiger Unterschrift) oder durch ?bermittlung eines solchen Schriftst?cks per Telefax erfolgen. Important note: The information included in this e-mail is confidential. It is solely intended for the recipient. If you are not the intended recipient of this e-mail please contact the sender and delete this message. Thank you. Without prejudice of e-mail correspondence, our statements are only legally binding when they are made in the conventional written form (with personal signature) or when such documents are sent by fax.
