Good idea. That should probably be an option though. Ray
> On Feb 18, 2016, at 11:58 AM, Abhyankar, Shrirang G. <abhy...@anl.gov> wrote: > > I agree. Having the warnings for all generators, voltages, etc. would be > helpful for the cases when users are also varying the generation on PV buses. > I would even like MATPOWER fixing the active power at PV buses to the max. or > min. limit, if the generation exceeds these limits, and informing the users > via a warning. > > Shri > > From: Ray Zimmerman <r...@cornell.edu <mailto:r...@cornell.edu>> > Reply-To: MATPOWER discussion forum <matpowe...@list.cornell.edu > <mailto:matpowe...@list.cornell.edu>> > Date: Thursday, February 18, 2016 at 10:34 AM > To: MATPOWER discussion forum <matpowe...@list.cornell.edu > <mailto:matpowe...@list.cornell.edu>> > Subject: Re: power flow question > > I agree that checking for exceeded limits and warning about them would be a > nice feature to add to the the power flow. I see no reason, though, why it > should be limited to the swing bus power injection … why not include all of > the other generator, voltage and branch flow limits, all of which can be > violated in a converged power flow solution. > > I’ll put it on the “to do” list. > > Ray > > >> On Feb 18, 2016, at 8:05 AM, Jovan Ilic <jovan.i...@gmail.com >> <mailto:jovan.i...@gmail.com>> wrote: >> >> >> Jose, >> >> I did not suggest to turn the swing bus into a PV bus. There should be at >> least one swing bus >> in the system unless you formulate your PF problem as ACOPF problem which >> does not need >> any slack buses. >> >> I understand what you are saying and you are right. I'd keep the swing bus >> as it is just >> to provide the angle reference (admittance matrix is rarely singular) and >> add to Jacobian a >> constraint on the sum of P and Q flows on the lines connected to the swing >> bus. The sum >> of all these lines out flows must be less than the power injection >> capability of the swing bus, >> both P and Q. If the constraint is violated the power flow does not >> converge. The original >> poster was concerned with the convergence when there is not enough >> generation, so >> no convergence would give them a really stern "warning" and leave them >> guessing what went >> wrong. Or you can just keep it simple and have PF implementation just print >> out a warning >> that the slack bus exceeded its capacity. Modifying the Jacobian was the >> first thing that >> came to my mind but I am not sure if it provides anything in addition of a >> warning to user. >> >> Jovan >> >> >> On Thu, Feb 18, 2016 at 3:25 AM, Jose Luis Marin <mari...@gridquant.com >> <mailto:mari...@gridquant.com>> wrote: >> 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 <jovan.i...@gmail.com >> <mailto:jovan.i...@gmail.com>> 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 <santiago.i...@gmail.com >> <mailto:santiago.i...@gmail.com>> 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" <wenlei_...@baylor.edu >> <mailto:wenlei_...@baylor.edu>> 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 >> >> >> >> >> >> >