It's an error thrown by Matlab while running the opf function possibly due to various reasons. See http://en.wikibooks.org/wiki/MATLAB_Programming/Error_Messages
From: Fereshteh Moghateli <[email protected]> Reply-To: MATPOWER discussion forum <[email protected]> Date: Tue, 17 Jun 2014 11:55:38 -0800 To: MATPOWER discussion forum <[email protected]> Subject: Re: OPF with IPOPT >hi >what is the meaning of error ''[r, success] = opf(casedata, mpopt)'' > > >On Mon, Jun 16, 2014 at 11:10 AM, Ray Zimmerman <[email protected]> wrote: > >MATPOWER is not able to handle non-convex cost functions. > >-- >Ray Zimmerman >Senior Research Associate >B30 Warren Hall, Cornell University, Ithaca, NY 14853 >phone: (607) 255-9645 > > > > > > > > > >On Jun 15, 2014, at 7:36 PM, Eser Patrick <[email protected]> wrote: > > >Dear Dr. Zimmerman, >Dear Matpower Community, > >Thank you for your help. I understand your comment about my costs not >defining a convex function. But unfortunately, I am specifically looking >to also solve problems that could have nonconvex cost functions. > >So for the case of nonconvex cost functions, can I still use Matpower? >Are there any solvers implemented/supported, that allow using a nonconvex >function (unlike IPOPT or MIPS)? If yes, how do I select those within the >code? > >I appreciate your help. > >Best Regards, > >Patrick Eser >________________________________________ >Von: Ray Zimmerman [[email protected]] >Gesendet: Montag, 9. Juni 2014 16:46 >An: MATPOWER Discussion List >Cc: Eser Patrick >Betreff: Re: OPF with IPOPT > >‹ I have replied to the list Š and you should address your questions to >the list (you have to be subscribed), not the list owner ‹ > >The problem is with the specification of the generator cost, namely that >the gencost parameters do not define a convex cost function. In >particular, see section 5.4.1 on how MATPOWER handles piecewise linear >cost functions. If you look at the basin created by set of linear >constraints defined by the points specified for generator 3¹s cost >function, it is probably not what you intended ($1/MWh for Pg < 20 MW, >$14/MWh for Pg > 20 MW. > >-- >Ray Zimmerman >Senior Research Associate >B30 Warren Hall, Cornell University, Ithaca, NY 14853 >phone: (607) 255-9645 > > > >On Jun 9, 2014, at 9:02 AM, Eser Patrick ><[email protected]<mailto:[email protected]>> wrote: > >Dear Dr. Zimmerman, >Dear Matpower Community, > >I am new to Matpower, and I am struggling to fully understand the method, >with which the optimization for lowest costs happens in the OPF. Please >let me make a short example case to show my problem: > >mpc.version = '2'; > >mpc.baseMVA = 100; > >mpc.bus = [ >[1, 3, 0, 0, 0, 0, 1, 1, 0, 380.0, 1, 1.2, 0.8]; >[2, 2, 0, 0, 0, 0, 1, 1, 0, 380.0, 1, 1.2, 0.8]; >[3, 2, 0, 0, 0, 0, 1, 1, 0, 380.0, 1, 1.2, 0.8]; >[4, 1, 45, 6.75, 0, 0, 1, 1, 0, 380.0, 1, 1.2, 0.8]; >]; > >mpc.gen = [ >[1, 0, 0, 4.5, -4.5, 1, 100, 1, 30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]; >%Power >[2, 0, 0, 4.5, -4.5, 1, 100, 1, 30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]; >%Power >[3, 0, 0, 4.5, -4.5, 1, 100, 1, 30, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]; >%Power >]; > >mpc.branch = [ >[1, 4, 0.0001, 0.001, 0.1, 0, 5000, 5000, 0, 0, 1, -360, 360]; >[2, 4, 0.0001, 0.001, 0.1, 0, 5000, 5000, 0, 0, 1, -360, 360]; >[3, 4, 0.0001, 0.001, 0.1, 0, 5000, 5000, 0, 0, 1, -360, 360]; >]; > >mpc.gencost = [ >[1.0, 0.0, 0.0, 3.0, 10, 100, 20, 120, 30, 140]; %Cost >[1.0, 0.0, 0.0, 3.0, 10, 100, 20, 120, 30, 140]; %Cost >[1.0, 0.0, 0.0, 3.0, 10, 100, 20, 240, 30, 250]; %Cost >]; > >So effectively, I have three 30 MW units (at bus 1,2 and 3) to satisfy my >demand of 45 MW at bus 4. The losses are negligible. The units are >technically the same, but have different costs to distinguish them. > >If I now run Matpower with the IPOPT optimizer (MIPS delivers the same >result, though), my resulting power output is: > >Unit 1: 12.5 MW >Unit 2: 12.5 MW >Unit 3: 20 MW >Overall cost (f): 450 $/h > >Obviously, this result is not correct. Unit 3 is by far the most >expensive one, yet it is asked to deliver the most power. Why is this >happening? How does the optimization work here? > >The only thing that strikes me here: Unit 3 has the lowest gradient of >all units (10 $/MWh from 20 to 30 MW)... is this the reason why it is >dispatched? If it is, why is it then not run at 30 MW, but only 20 MW? > >I read the segment about the OPF in the manual carefully, but I can't >find an explanation for these phenomena in there. Is my problem ill-posed >in some way? > >I felt free to attach the input and output files to this email. > >I would be very thankful for any hints/explanations on the topic. I >greatly appreciate your help. > >Best Regards, > >Patrick Eser<pe_example_case.m><matpower_output.txt> > > > > > > > > > > > > > >
