Hi Ms. Dogan, I will try to give some simple answers to your questions, yet if you need more information, please don't hesitate to write back.
For your first question, what you got as a message is not actually an error message but kind of a warning. The solution method of an OPF problem adopted in MATPOWER needs to get the inverse of the matrix. This warning you got states that matrix is close to singular (singular matrix is non-invertible) so that computationally you cannot trust the inverse of a matrix, which is closed to singular. I may suggest you to increase the interval you used for reactive power generation. You may increase the value in 4th column of mpc.gen matrix and decrease the value in 5th column of mpc.gen. This change will increase the reactive power generation interval. If that doesn't work, the reason of singularity might be the values you used for Pmax and Pmin. You may want to change and try again. For your second question, the value you got (7,....e-06) can be treated as zero. Exact zero in optimization problem is computationally difficult. Generally, the solvers use a small epsilon value as a stopping criterion. In other words, every number less than epsilon is actually zero. Yet if I couldn't convince you, or if you want to have exact zero in the generation, then I suggest you to use GEN_STATUS column(8th column) at mpc.gen matrix to take the generator out of service. This will lead MATPOWER not take that generator into account, so it will give you exact zero in the generation. For the second part of your question, if you want a generator to generate at least 5MW, then change the value of PMIN (10th column) in mpc.gen matrix to 5. But this constraint will force this generator to generate at least 5MW. As far as I know, there is no way to tell MATPOWER; I want the status of a generator to be OFF if the generation is less than 5MW and ON if the generation is more than 5MW. I cannot help you on that. I hope those information are helpful. Regards, ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *Gokturk Poyrazoglu* Teaching Assistant | Student Assistant Department of Electrical Engineering / The State University of New York at Buffalo 230V Davis Hall, Buffalo, NY 14260 *Phone *: (716) 239 - 8095 *E-mail* : [email protected] On Thu, May 15, 2014 at 7:01 AM, Gamze Dogan <[email protected]> wrote: > Hi, I am new at using Matpower and I have two questions: > > 1. I tried to launch an OPF but I wanted it to only vary the reactive > power of the generators to get to a solution, thus I put Pmax, Pmin and Pg > to the same values. Apparently I cannot do that because I get the following > error message: > > > In mips at 422 > In mipsopf_solver at 145 > In opf_execute at 106 > In opf at 225 > In runopf at 96 > In MAIN at 190 > Warning: Matrix is close to singular or badly scaled. > Results may be inaccurate. RCOND = 2.164066e-019. > > > Do you know how to help me? > > > 2. I put a generator to 0 production and then I launch my OPF, the results > gave me for that generator a production of 7,00441667255350e-06 > My question is, how can I ask my OPF not to start a generator for a > production that low? Let's say that I want my OPF to start a generator for > at least a production of 5MW? > > Thank you for your help, > > Regards, > > G.D. > >
