The OPF selects voltage magnitudes and generator reactive injections in a way that satisfies the power balance equations and minimizes the real power cost. Voltage and reactive power injections do not have direct costs on them, but they do affect losses, which in turn affect real power generation. They can also affect the ability to transfer real power across key interfaces (e.g. between load centers and inexpensive generation), so in that sense they can also indirectly affect the set of feasible real power dispatches and therefore the system cost.
FYI, setting RATE_A = 0 is the preferred way to specify an unconstrained flow. -- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On May 2, 2013, at 12:05 PM, spyros gian <[email protected]> wrote: > Dear Dr Zimmerman, > > A simple ACOPF objective function is : > minimize Pgen * fuel_cost , where fuel_Cost is $/MWh and Pgen the MWh > produced. > In MatPower, I set the fuel costs for Pgen, in the mpc.gencost matrix. > I do not set any costs for Qgen production. > > I also set in the mpc.gen matrix, that Qmax=100 and Pmax=100 and also I set > rateA=10000 > i.e. no line constraints. Also, bus voltages are within statutory limits. > > Matpower results state than generator 1 produces 0 MVAr, generator2 produces > 50 MVAr and generator3 > produces 60 MVAr, at certain voltages. > > How does MatPower select these values for Qgen and Voltages, given that there > is no objective > function governing them? The only constraint is Qgen <=100, and V within > limits. > > Thank you, > Giannikos Stas > >
