Yes. I suspect that the convergence issues are related to your non-convex cost function (i.e. a < 0).
-- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Jul 3, 2013, at 3:57 AM, Julian dB <[email protected]> wrote: > Hi, > > I am currently working with a model of a 1000+ bus transmission network. > I wanted to implement the dropping efficiency factor of power plants when > working under off-nominal conditions. Therefore i tried altering the cost > function, but with that my opf doesn't converge anymore, which I can't > explain. > > Here's what I did: > I assigned each power plant a quadratic polynomial cost function (ax² + bx > +c). > a = - 1 * (costs at nominal power output) / (nominal power output)²; > b = 2 * (costs at nominal power output) / (nominal power output); > c = 0. > So basically a function with its apex above the nominal power output, sloping > down to 0 towards the origin. > > Does someone have an idea, why the opf stopped converging? Or what i could do > differently? > > I also unsuccesfully tried using the solver IPOpt. > And I tried using a piecewise linear cost function instead looking > approximately the same as the quadratic function. With this function the opf > did converge but not to a feasible solution. At least for this case I think > it doesn't work because the shape of the function is not "convex" as > described in the manual. > > I would be grateful for any help, regards > Julian B.
