This is the way I am going to face this issue then. In the worst case, I will perform the simulation without constraints on the lines I think... Thank you very much for your precious help, time and advices!
Sincerely, Enrico > Il giorno 21/feb/2017, alle ore 10:36, Samuel Perkin <[email protected]> ha > scritto: > > Dear Enrico, > > I’m happy to help. > > The resistance and reactance values don’t necessarily look too high or low. > Nothing stood out as obviously wrong to me at least. I reduced the values > just to see if the convergence of the ACOPF was a topology issue. I find that > simplifying a system until it works is useful when dealing with problems like > this. Another thing you could try is to solve parts of the system (e.g. > simplify your network to only 380kV nodes, or a small area) and gradually add > complexity back into your model until it fails. > > In response to your last question, you’re almost correct. In an OPF the > values you put in to mpc.gen(:,PG) will change, as PG is an optimisation > variable, but the initial guess will affect the convergence of the algorithm. > In some cases (possibly yours!) a bad initial guess for PG and QG can prevent > the ACOPF from converging to a solution. > > Kind regards, > > Samuel > > > From: [email protected] > [mailto:[email protected]] On Behalf Of Enrico > Vaccariello > Sent: 21. febrúar 2017 00:48 > To: MATPOWER discussion forum <[email protected]> > Subject: Re: Sequential OPF: Non-convergence of both OPF and PF > > Dear Samuel, > I really appreciate your help, thank you. > > After reading your reply I have made some further tests, and I believe that > the very issue is the branch matrix too. > The ACOPF actually converges with your corrections on the branch matrix, and > I have noticed that it still works even keeping the original values for the > lines' resistances. Keeping the original values of mpc.branch(:,BR_R) results > in active power losses accounting for around 3% of the total generated active > power, which seems reasonable to me, suggesting that the p.u. values of the > resistances are acceptable. > > So the problem should lie in the values of X and of the MVA ratings. > Did u reduce the values of X because they looked too high to you or just to > get the ACOPF to converge? > As for the MVA ratings given in mpc.branch(:,RATE_A), setting them all equal > to zero, as you suggested, and running the ACOPF clearly shows that in the > optimal solution some branches have power flows much higher than their limit > in the original case. Some of these branches are the same that you indicated > (150,369,...). > What I think is weird is that all these branches link PQ buses, with no power > generation. So, it's difficult to understand what is the logic behind it. > Anyway, I have checked all the branches and their From and To indexes are all > correct. > > I hope I will find a way to fix this. > Until then, thank you again. > > One last thing I wanted to ask about your reply (first paragraph of your > mail): I have understood that the values that you use to initialize > mpc.bus(:,PG) do affect the solution of the PF problem, while they are not > considered by the OPF solver. Is that right? > > Best regards, > Enrico > > > > > > 2017-02-20 12:31 GMT+01:00 Samuel Perkin <[email protected]>: > Hi Enrico, > > I had a quick look at your case. Firstly, the results you get when running an > DC PF on your case are normal. The active power is fixed at all Load and > Generator buses, and therefore only the slack bus can add/remove active power > to the system in order to find a solution. Given that all your generators > begin with 0 MW of active power production, you find that all power must be > produced at your slack bus. > > I tried running an ACOPF on your model, using: > mpopt = mpoption('verbose', 3, 'out.force', 1,'pf.nr.max_it',10); > runopf(mpc,mpopt); > > This doesn’t converge, but the output suggests a few issues with your model. > If you look at the branch constraints, you’ll find that some of your branches > with the greatest capacity are only being utilized <5%. Whilst a few low > capacity branches (150, 290, 369, 370) have absurdly large flows. This > implies to me that you either have some branches connected to the wrong > buses, or have some errors in the electrical parameters of your lines. > > Note that it is possible to get an ACOPF to converge on your case if you > apply the following modifications/simplifications, which supports my argument > that there is probably a few errors in your branch data: > mpc.branch(:,RATE_A) = 0; > mpc.branch(:,BR_R) = 0.1*mpc.branch(:,BR_R); > mpc.branch(:,BR_X) = 0.001*mpc.branch(:,BR_X); > > I hope this helps you debug your case, and good luck with your thesis. > > Kind regards, > > Samuel Perkin > > From: [email protected] > [mailto:[email protected]] On Behalf Of Enrico > Vaccariello > Sent: 20. febrúar 2017 02:25 > To: [email protected] > Subject: Sequential OPF: Non-convergence of both OPF and PF > > Dear All MATPOWER developers and users, > I really hope some of you can give me some advice. > I am working on sequential OPF simulations (not using MOST, but simply > running MATPOWER's runopf in a loop and manually updating some values the > MATPOWER case at each time-step t) to be performed on a case(s) that I have > been working a lot to prepare. > Anyway, unfortunately, now that the time of running the simulation has > finally come, I have some serious convergence issues. > > With the 285-bus case structs that I have built, the OPF simulation running > with the default MIPS does not converge. > The case structs differ one from another for some parameters as a function of > t (time-step of the loop). Anyway, whatever the t I set, the OPF won't > converge in any case, so there must be some structural issue of my cases I > guess. > I'll attach the case of t=1 to this mail for who wishes to have a look. > > Making some tests, I have found out that the PF simulation does not converge > either. Among the (non-converged) results of the PF it seems that the slack > bus is the only trying to generate active power (a lot of), whereas all the > others do not dispatch, i.e. results.gen(:,PG) is zero for all the generators > of the PV buses. > What is more, the same generators dispatch very high quantities of reactive > power, much beyond their lower and upper limits. > > If someone could help I would be very grateful... Last days for my thesis, > very hard times! > > Thank you and best regards. > Enrico > >
