Re: MATPOWER QUESTIONS- runopf

[Alessandro Sacco]

Good day to all of you! Always talking about AC OPF formulation, I would ask you something more. When you introduce as constraints (non linear equality constraints) the active and reactive power balance at each bus, the result is 2*bus Lagrange multipliers on bus power mismatch; now I'm dealing with economic formulation of the OPF (such as spot prices) and I need to find out the values of Lagrange multiplier on total active and reactive power balance, the so called system-lambda. So I'm trying to obtain this 2 multipliers introducing two more non-linear equality constraint in the formulation of the AC OPF, these are the total active and reactive power balance:     sum(Pg_i) - sum(Pd_i) = LP , where LP are active losses     sum(Qg_i) - sum(Qd_i) = LQ , where LQ are reactive losses but in this way I find out new enormous Lagrange multipliers, so I suppose something is wrong. I also tryed to compute the amount of this 2 constraints after solving the OPF with your formulation and the result is the 2 new constraints are already satisfied, so the formulation of problem takes properly into account the losses, too. So, finally, my question is how we can calculate the system lamba for P and for Q. Thank you, have a nice day! Alessandro Mutmainna Tania wrote: thanks so much!!!! ----- Original Message ----- From: Ray Zimmerman <r...@cornell.edu> Date: Tuesday, November 25, 2008 1:14 pm Subject: Re: MATPOWER QUESTIONS- runopf To: MATPOWER discussion forum <matpower-l@list.cornell.edu> By default this section displays a row for each bus at which an upper (Vmax) or lower (Vmin) voltage limit is binding. These limits are defined in the corresponding column of the bus matrix in the input. The 'mu' values are the shadow prices (Lagrange multipliers) on the corresponding constraint, so they represent the sensitivity of the system cost to a unit change in the limit. -- Ray Zimmerman Senior Research Associate 428-B Phillips Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Nov 25, 2008, at 12:53 PM, Mutmainna Tania wrote: dear Professor Zimmerman, Good Day!! I would like your help to understand the "runopf" output values. What exactly is defined in "voltage constraints" table and what do "Vmin mu" and "Vmax mu" represent? thanks in advance. Regards. Tania -- Alessandro Sacco ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜ viale Europa 40 36025 Noventa Vicentina VI Italy ˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜˜