Thank you very much to everyone. I should have solved the matter definitively.
Il giorno lun 21 giu 2021 alle ore 17:12 Russ Patterson <r...@relayman.org> ha scritto: > Hi Simone, > > > > Actually, it looks like PSS/E just converts 3-winding pair-wise data to > the T equivalent model (just like in the attachment I sent you in previous > email). Then it just models as three 2-winding transformers (the node in > the middle is fictitious but needed for the mathematical model). See page > 2 here: > https://static.dc.siemens.com/datapool/us/SmartGrid/docs/pti/2010July/PDFS/Modeling%20of%20Three%20Winding%20Voltage%20Regulating%20Transformers.pdf > > > > Here is a link to the MATPOWER documentation where you can find details on > the psse2mpc() function: > https://matpower.org/docs/ref/matpower5.1/menu5.1.html It calls another > function (psse_convert_xfmr) which has these lines of code below: > > > > 0187 R1 = (R12+R31-R23) ./ 2; > > 0188 R2 = (R12+R23-R31) ./ 2; > > 0189 R3 = (R31+R23-R12) ./ 2; > > 0190 X1 = (X12+X31-X23) ./ 2; > > 0191 X2 = (X12+X23-X31) ./ 2; > > 0192 X3 = (X31+X23-X12) ./ 2; > > > > The above is simply the conversion from pair-wise test data to the T model. > > > > Which make it pretty clear that, aside from all the data structure > manipulation and other “foggy” items), it is just building the T model and > then making 3 two-winding transformers as the first link above describes. > > > > Best regards, > > russ > > > > > > *From:* bounce-125723529-88411...@list.cornell.edu [mailto: > bounce-125723529-88411...@list.cornell.edu] *On Behalf Of *Russ Patterson > *Sent:* Monday, June 21, 2021 10:49 AM > *To:* 'MATPOWER discussion forum' > *Subject:* RE: Negative resistance > > > > Hi Simone, > > > > I’m not certain I understand your question. The pair-wise test data > include winding resistance and leakage inductance (I ignored resistance in > my example for simplicity). This pair-wise test data does not account for > the magnetizing branch if that is what you mean by RM. > > > > If you search the archive ( > https://www.mail-archive.com/matpower-l@cornell.edu/) on “3-winders” you > will see a reply from Ray explaining that the psse2mpc() function is used > to convert 3-winding transformers to multiple 2-winding transformers to put > in mpc.branch. I don’t know what is “under the hood” on that function. I > would be interested to see the math if you take the time to figure it out. > > > > You can’t just put the pair-wise data directly into mpc.branch for > 3-winding transformers. In my experience, the only case in which that > would work fine is when the transformer is balanced (H-X and H-Y pair > impedances are equal, or very close) and the 2 generators are loaded the > same (P,Q). Otherwise, you need to convert using psse2mpc(). > > > > Best regards, > > russ > > > > *From:* bounce-125721802-88411...@list.cornell.edu [mailto: > bounce-125721802-88411...@list.cornell.edu] *On Behalf Of *Simone Fratton > *Sent:* Sunday, June 20, 2021 5:36 AM > *To:* MATPOWER discussion forum > *Subject:* Re: Negative resistance > > > > Hello, thank you so much again for your answer to the problem of negative > resistances. I still have doubts though. Considering precisely the T > diagram for the 3-winding transformer (that of your attached) the possible > negative resistance that I find myself is RM? How do I know the value of > the other resistances? I will eventually only have 2 rows of mpc.branch > used for the 3-winding transformer or am I wrong? > > Thank you so much in advance I hope I don't bother you too much > > > > Il giorno ven 18 giu 2021 alle ore 15:01 Russ Patterson <r...@relayman.org> > ha scritto: > > Hi Simone, > > > > The negative branch is due to the conversion of pair-wise transformer test > data to “T” model. See if the attached helps. It is not a “real” negative > physical value – it is necessary for the mathematical model. > > > > Best regards, > > russ > > > > > > > > *From:* bounce-125719454-88411...@list.cornell.edu [mailto: > bounce-125719454-88411...@list.cornell.edu] *On Behalf Of *Simone Fratton > *Sent:* Friday, June 18, 2021 5:17 AM > *To:* MATPOWER discussion forum > *Subject:* Re: Negative resistance > > > > Thank you very much for your answer, but I am not sure that I have yet > understood why; especially if at the end it's about having a transformer > with negative resistance. > > > > Il giorno ven 18 giu 2021 alle ore 11:08 Dirk Van Hertem < > dirk.vanher...@ieee.org> ha scritto: > > Hello, > > Negative resistances normally correspond to equivalent branches... > > Dirk > > On 18/06/2021 11:04, Simone Fratton wrote: > > Hello everyone, > > I wanted to ask you if anyone knows exactly why in some cases the > resistance of mpc.branch is negative? Or at least if someone has any good > ideas. > > For example, case3012wp has as many as 10 negative resistances (all refer > to a transformer). > > Thank you all very much. > >
