Ray, Thanks a lot, this clears a lot confusions i had. i appreciate.
On 12 December 2012 21:24, Ray Zimmerman <[email protected]> wrote: > Álvaro's answers are correct, but maybe these additions will help too … > > On Dec 9, 2012, at 12:20 PM, Fred Kanjelesa <[email protected]> wrote: > > I am using MATPOWER to run OPF for a 60 bus network modeled based on a > real power system. the output window indicates MIPS is the solver used and > converges in quite a few iterations. > > *Question 1* > what i do not understand is whether MATPOWER uses Quadratic Programing > (QP) for power systems defined with quadratic generation cost functions or > it uses Linear Programing (LP) > > > For the AC problem, it does not use QP or LP, it solves the full NLP > problem. For DC OPF it uses a QP if the costs are quadratic, otherwise an > LP. > > *Question 2* > If it uses LP is there a way of knowing in how many linear segments the > polynomial/quadratic cost function is converted to linearize it? > > > MATPOWER can model both polynomial cost functions (only up to quadratic > for DC OPF) or piecewise linear. For AC it uses the full non-linear cost > function. For DC it picks the solver based on the cost function, but it > will not automatically convert a polynomial to a piecewise linear cost. > MATPOWER does include a utility function (poly2pwl.m) that can do this, but > it is not used internally. > > *Question 3* > Is there a way of knowing the confidence level of the results obtained > from an OPF MATPOWER simulation, i.e. a value or something to use one can > use to convince others the certainity of the results. > > > Each algorithm has a set of parameters it uses as termination criteria. > Typically using smaller values will give more precise results, but there is > a limit to how small you can go before you reach numerical limitations. I > don't think there is a simple "confidence level" number MATPOWER can give > you, but in practice if you solve the same problem with multiple solvers, > the differences between the solutions should give you an estimate of the > numerical accuracy of the solution. > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > -- *Fred Kanjelesa.* KU/Nepal. Home (Zambia): +260967753320 "Go as far as you can see. When you get there, you'll be able to see farther!" *Thomas Carlyle* ** ****
