Good idea. That should probably be an option though.
Ray
> On Feb 18, 2016, at 11:58 AM, Abhyankar, Shrirang G. <[email protected]> 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 <[email protected] <mailto:[email protected]>>
> Reply-To: MATPOWER discussion forum <[email protected]
> <mailto:[email protected]>>
> Date: Thursday, February 18, 2016 at 10:34 AM
> To: MATPOWER discussion forum <[email protected]
> <mailto:[email protected]>>
> 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 <[email protected]
>> <mailto:[email protected]>> 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 <[email protected]
>> <mailto:[email protected]>> 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 <[email protected]
>> <mailto:[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]
>> <mailto:[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]
>> <mailto:[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
>>
>>
>>
>>
>>
>>
>
