Because of the form of the user-defined costs, I'm not sure you have full control over a constant term, but that doesn't impact the optimization anyway. You can certainly implement the quadratic function f(x) = -x^2 + 4x - 4. You will simply have to add an offset of 2 to that cost and to the final objective function value outside of the optimization.
You can do this with the following parameters: rhat = 2 k = 0 d = 2 m = 1 C = -1 -- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Sep 17, 2012, at 3:13 PM, Panagis Vovos wrote: > Dear Ray, > > I mean an quadratic cost function, such as f(x)= - x^2 + 4x - 2. This > function f(x) has both negative and positive values for positive > values of x (attached picture). > > Thanks for the help, > > Panagis > > > > > On 17 September 2012 16:20, Ray Zimmerman <[email protected]> wrote: >> In order to be sure I understand what you are attempting, I think I'd still >> need an example of the kind of function you are looking for. >> >> -- >> Ray Zimmerman >> Senior Research Associate >> 419A Warren Hall, Cornell University, Ithaca, NY 14853 >> phone: (607) 255-9645 >> >> >> >> >> On Sep 14, 2012, at 3:40 AM, Panagis Vovos wrote: >> >> Dear Ladies and Gentlemen, >> >> Judging from a reply I received already, I definetely have not made it >> perfectly clear what I mean by negative-psitive values for my >> user-defined cost function. I can get a function having both positive >> and negative values, BUT ONLY IF my variable can take negative values. >> This is because the user defined cost function is in the form >> Y=aX^2+bX, which means it has to verify Y=0 for X=0 (cross junction of >> the two axes). Unfortunatelly, most OPF variables cannot take negative >> values. >> >> >> Thanks again, >> >> Panagis Vovos >> >> >> >> Dear Ladies and Gentlemen, >> >> I am trying to define my own cost function, that will be added to the >> regulat MATPOWER OPF cost function, using 5.3.1. However, after >> simulating (5.27)-(5.31) in Matlab, I am unable to produce a (ideally, >> quadratic) cost function that will span in both negtive and positive >> values. The best I can get is a positive or negative (but never both) >> cost function with a dead band. Does anyone know a way that I can >> achieve this according to MATPOWER standard approach or do I have to >> write my own code for the definition of the cost function, derivatives >> etc? >> >> Thank you for your time, >> >> Panagis Vovos >> >> > <fx.jpg>
