But you did that, it would no longer be a powerflow calculation. There are good mathematical reasons why the standard powerflow calculation is formulated so that there should be at least one swing bus (where you specify both V and A, leaving P and Q "free"). If you specified V, A, and Pgen at the swing, this would yield an overdetermined system. You could theoretically formulate a powerflow in which the swing bus specified only A (the global angle reference) and Pgen, leaving Vref and Qgen free, but this would yield a system of equations with a severe pathology, namely a near-singular Jacobian (this originates from the fact that the full transmission admittance matrix, being a Laplacian matrix, always has a zero eigenvalue, which corresponds to a translation symmetry consisting in uniformly shifting all voltages; pinning down at least one voltage is what breaks this symmetry and recovers invertibility).
However, I think you're right it would be a good idea to *warn* the user when the swing generator(s) have gone over their PMAX (or below their PMIN!). -- Jose L. Marin Grupo AIA On Thu, Feb 18, 2016 at 12:08 AM, Jovan Ilic <[email protected]> wrote: > > Good point, maybe we should trow a Pgen constraint on the swing buses in > the Jacobian. > > > > On Wed, Feb 17, 2016 at 5:30 PM, Santiago Torres <[email protected]> > wrote: > >> Because the exceding generation is supplied by the swing bus. Normal >> power flow does not check power generation limits. >> El 17 feb. 2016 1:58 PM, "Bai, Wenlei" <[email protected]> escribió: >> >>> Dear Ray, >>> >>> I tried to modified load of ‘case9’ to exceed the total generation >>> capacity purposely. >>> >>> To my surprise, power flow still converges. More specifically, the >>> total generator ‘on-line capacity’ is 820MW, while the ‘actual generation’ >>> is 920.8MW >>> >>> Why the actual generation can be larger than its capacity? >>> >>> >>> >>> Blessings, >>> Wenlei >>> >>> >>> >> >
