Hello,
I have been working on an AC OPF/Economic Dispatch model with ipopt for solving
the nonlinear power flow equations, and i have been using Matpower (under
Octave in MacOS X) as a baseline with which to compare results, but my model is
returning different answers. This has led me to a few questions:
1 -- When using runopf, what variables (bus voltage, real/reactive power,
etc.) are actually taken from the case files and kept constant? Originally, I
was working under the assumption that voltage magnitude at generator buses (Vg
in the case files) was kept constant, but case30.m shows that not to be the
case.
2 -- Running my model on case6ww.m, if I fix the voltage magnitude and
angle at generator buses to match Matpower's results, I end up with the same
answers (to within rounding error), but if no voltages are assumed to be known
a priori, I end up with very different dynamics. In fact, the solution I get
ends up having a lower objective value than the Matpower solution which becomes
even lower when allowing voltage magnitudes to be unbounded (resulting in
voltages well outside of the Vmin, Vmax range given in the bus data). Is this
an artifact of ipopt instead of MIPS, or is this issue related to my
misunderstanding of what values are kept constant when solving the OPF?
Thanks for your time,
~Zev Friedman
