Dear Mr.Zimmerman, Thank you very much for your quick help. Actually, I was also thinking along the same direction...but just to ensure whether what I thought is actually correct, I posed this question. Definitely, I have got the answer what I was seeking for and I am really thankful to you for this.
with best regards Sarina On 3/15/07, Ray Zimmerman <[email protected]> wrote:
On Mar 14, 2007, at 10:12 PM, Sarina Adhikari wrote: > I have a small query on Matpower. I noticed that in an optimal > power flow program (fmincopf), all the variables are sent as the > parameter > and there is no distinction between PV and PQ buses. In traditional > Power > flow, we have to make a distinction between PQ and PV bus. The > limits on > reactive power of the PV bus needs to be checked. If it hits the > limit,we > treat it as the PQ bus. But, in OPF of Matpower, I didnot notice these > things. Are there any assumptions or modificatiions made to take > care of this which I > have overlooked? Specifying buses as PV or PQ is done in a traditional n-bus power flow problem, because there are 4*n unknowns (P, Q, V, theta at each bus) but only 2*n equations (P and Q power balance at each bus). So in order to solve the equations we must specify values for half of the variables. We traditionally pick those that we either already know (reference theta, P and Q at load buses) or are able to control (V and P at generator buses). In the context of an optimal power flow, the power balance equations are simply constraints in an optimization problem and it is not necessary to make the PV / PQ distinction for the purpose of finding a solution. If, for example, one would like to hold the voltage constant, it can be done using the voltage constraints. Similarly, for any of the other variables. I hope this answers your question. -- Ray Zimmerman Senior Research Associate 428-B Phillips Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645
