The OPF problem does not need the concept of a slack bus. The slack
bus is needed for the power flow problem, where you want to specify
the generator injections, but are not permitted to independently
specify all of them. One is dependent on the others. In the OPF, on
the other hand, all generator dispatches are free variables,
constrained by the power flow equations.
So the OPF problem does not include any slack bus idea. It does,
however, require a voltage angle reference. In MATPOWER, the reference
bus is used as a voltage angle reference in the OPF and as both a
voltage angle reference and a real power slack in the PF problem.
--
Ray Zimmerman
Senior Research Associate
428-B Phillips Hall, Cornell University, Ithaca, NY 14853
phone: (607) 255-9645
On Mar 17, 2008, at 1:45 PM, kanwardeep singh wrote:
Dear Dr. Ray,
I have a querry regarding Matpower's OPF
program that how its load flow equations are considering the effect
of slack bus generator? Say if bus no. 1 is the slack bus then OPF
is considering Pg1 as one of the variable, then how it becomes
possible that Pg1 takes into account additional power to be injected
or taken out for overall balancing of the system.
Thanks for providing a platform to resolve the querries.
K D Singh
