What are the original PMIN values for those generators? If you are actually
relaxing constraints from a feasible problem, it cannot be infeasible (the
previous solution is feasible for the new problem). Just to be sure the problem
isn't different in some other way, try the following …
mpc = loadcase('your_initial_problem');
r = runopf(mpc);
i = <wind gen indices>;
r.gen(i, PMIN) = 0.99 * r.gen(i, PMIN);
r2 = runopf;
Be sure to check r.success and r2.success. If the first is 1 and the second is
0, please send me the case off-list. I'd like to see it.
--
Ray Zimmerman
Senior Research Associate
419A Warren Hall, Cornell University, Ithaca, NY 14853
phone: (607) 255-9645
On Oct 3, 2012, at 1:37 PM, Evangelos Galinas <[email protected]> wrote:
> Hallo and thank you very much for the input.
>
> my system has 14 generators of which 3 are supposed to be wind gens.
>
> What i'm changing in the infeasible case,is that I'm making the min P =0.1
> "mpc.gen(i,10)=0.1" for only the three Wind generators. Even if I make it
> 0.99 of the original limit it becomes infeasible. As I said, I'm relaxing the
> constraints, it does not make any sense becoming infeasible.
>
> Thanks once more,
>
> Vagelis
>
> From: [email protected]
> Subject: Re: opf issue while cahnging the Pmin of gens
> Date: Wed, 3 Oct 2012 11:56:47 -0400
> To: [email protected]
>
> I'm not sure I understand what you are changing between the feasible case and
> the infeasible one. But if it is infeasible, then it will not solve
> successfully, and any results (generation levels, line flows, etc.) are
> meaningless.
>
> Ray
>
>
> On Oct 1, 2012, at 8:10 PM, Evangelos Galinas <[email protected]> wrote:
>
> Dear all,
>
> I have the following issue when I'm implementing an OPF I would like to ask
> if anyone has experienced ever something similar.
>
> Well, I want to check feasibility for constrained and unconstrained OPF's.
> When I have only the max limits of Gens on, the opf solves and the same
> happens when I have minimum limits on as well as when I include max flow
> limits for branches. All the above take plave by manipulating the
> mpc.gen(:,10)-> 0 or something close to and mpc.branch(i,6)-> 0 or 9999.
>
> The really weird thing happens when I include the regular min limits for
> conventional units but I limit the min P of my Wind gens to 0 or sth close
> to. Then the opf runs crazy and instead of solving even easier since I
> relaxed the constraints the system becomes infeasible. For the same Load
> conditions (4,4 G) while before the Generation was the same now, it increases
> to 5,3 G and all the branch loading go up to 300-400 %.
>
> Does anyone have a hint on why this can be happening. It sounds like an error
> from my side, but I can see in the results that the constraints are exactly
> as I had told matlab to do it.
>
> Any kind of help would be much appreciated.
>
> Best Regards,
>
> Vagelis
