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/[email protected]/) 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: [email protected] [mailto:[email protected]] 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 <[email protected]> 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: [email protected] [mailto:[email protected]] 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 <[email protected]> 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.
