Thank you. My questions are introduced as follows:
1.The value of Pmin in the case file and in the results are different while they have to be the same. Why they are different when I am doing runmarket? 2. The value MU_Pmin for dispatachable load and generators are computed in different way, i.e. for generators it is calculated as explained in the manual while for the dispatchable loads I don't know how they are calculated. I want to know this(when I am doing runmarket). 3. How MU_Pmax is calculated? 4. Also, for voltage how they are calculated (MU_Vmin&max when I am doing runmarket) I am so sorry for asking many questions. Best Regards C.F. On Thu, Mar 29, 2012 at 21:28, Ray Zimmerman <[email protected]> wrote: > PMIN is a lower limit on the amount of generation PG in MW. This is an > input value set in the case file. The value of MU_PMIN is the sensitivity > of the objective to this constraint, a shadow price computed by the > optimization. Similarly for PMAX and MU_PMAX. If you don't understand > shadow prices you will need to get that from a course or book on > optimization theory. > > When using the smart market code (runmarket.m) PMIN (for loads) and PMAX > (for generators) are modified according to the bid and offered quantities > before calling the OPF. > > Does that help? > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > On Mar 29, 2012, at 12:27 PM, Carol Francesca wrote: > > Thank you for your response. > > My problem is the first: I don't understand how PMIN is computed in the > result(it is different from the Pmin set in the case file)? MU_PMAX? > > MU_PMin for dispatchable loads and generators are calculated in a > different way. I cannot understand this also why? > > Could you please explain these? > > Best Regards > > Carol Francesca > > > > On Thu, Mar 29, 2012 at 17:10, Ray Zimmerman <[email protected]> wrote: > >> Are you saying you do not understand what a shadow price on a constraint >> is? Or that you do not understand a specific optimization algorithm (such >> as the interior point method used by MIPS) and how these multipliers are >> computed? >> >> If it is the first, I will just say, it is the sensitivity of the >> objective function to the constraint. In other words, in the case of >> MU_PMIN, for example, a shadow price of $X/MW means that the objective >> function would decrease by $X*Y if you were to relax the PMIN limit by Y MW >> for some tiny value of Y. >> >> If it is the second, I suggest that you take a course or read a book on >> non-linear optimization. The algorithmic details of how these shadow prices >> are actually computed is different for each algorithm and beyond the scope >> of what I can explain in an e-mail. >> >> -- >> Ray Zimmerman >> Senior Research Associate >> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >> phone: (607) 255-9645 >> >> >> >> >> On Mar 28, 2012, at 4:13 PM, Carol Francesca wrote: >> >> Dear Dr. Zimmerman, >> >> I read the manual but I didn't understand how Pmin mu for dispatchable >> loads as well as Pmax for generators are calculated. I really confused. If >> it is possible please explain, because It is not clear for me how it has >> been computed. >> >> Best Regards >> >> Carol Francesca >> >> >> >> On Mon, Mar 26, 2012 at 15:16, Ray Zimmerman <[email protected]> wrote: >> >>> MU_PMIN and MU_QMIN are shadow prices on the minimum generation limits >>> for real and reactive power. Constraint shadow prices, also called >>> Kuhn-Tucker multipliers, are a standard output of most all constrained >>> optimization solvers. See any book on constrained optimization for a >>> description of their meaning and how they are computed for any given >>> algorithm. >>> >>> In MATPOWER, the shadow prices are computed by whichever solver is used. >>> For example, in the case of the default MIPS solver, they are included in >>> the mu variable in equation (A.32) in Appendix A. The value is computed in >>> mips.m. >>> >>> I should probably mention also that in the case of trapezoidal generator >>> capability curves (see Section 5.4.3 in the manual), if one of the sloped >>> portions of the curve is binding, its shadow price is decomposed into >>> components for the corresponding real and reactive limits. >>> >>> -- >>> Ray Zimmerman >>> Senior Research Associate >>> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >>> phone: (607) 255-9645 >>> >>> >>> >>> >>> On Mar 25, 2012, at 7:08 PM, Carol Francesca wrote: >>> >>> Dear Prof. Zimmerman, >>> >>> I have a question: >>> >>> When I do runmarkt sometimes price and Lambdas are not equal and its >>> because of network congestion and losses. >>> In MATPOWER, how MU_PMIN and MU_QMIN are calculated? Could you please >>> address the m.file which calculates these? >>> How they affect the prices? There is no sufficient explanation about it >>> in the manual. I am sorry but I cannot understand how they are calculated. >>> >>> Best Regards >>> >>> Carol >>> >>> >>> >> >> > >
