Dear Mr.Zimmerman: Thank you very much. Yes, I am using the same slack when I say "works for DC PF".
In DC OPF, there are generator capacity constraints and transmission line constraints. Before any constraint being reached, the proportion is fixed for an incremental load change in any bus. However, the proportion keeps changing as one and more constraints are reached. In this case, is it possible to predict the flow changes among all branches for an incremental load change? Can we resort to the original equations to get an analytic solution? Thanks a lot. Jerry On Wed, Mar 2, 2011 at 8:18 PM, Ray Zimmerman <[email protected]> wrote: > The PTDF shows how the power flows change based on load changes, given a > specific slack distribution. When you say that it "works for DC PF", I > assume you mean that you can use it to predict the new flows you get when > you run a new DC PF. That's because you probably are using the same slack > bus for both. If you think about how a DC OPF redispatches for an > incremental load change, the "slack" is taken up by the units that are on > the margin. I'm not sure how to compute what the proportion is, but if you > knew that proportion you could use it to specify the slack distribution for > computing the appropriate PTDF. > > -- > Ray Zimmerman > Senior Research Associate > 211 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > On Mar 2, 2011, at 5:27 PM, z qin wrote: > > > Hello, > > > > It seems that the linear shift factors (PTDF matrix) only works for DC > PF, but not for DC OPF. Is there a corresponding matrix for DC OPF? I am > wondering how the power flows on all the branches change if one bus's power > demand changes. Any suggestions? Thanks a lot. > > > > Jerry > > > > -- ------------------------------------------------------------------------------------ Zhengrui (Jerry) Qin Computer Science College of William and Mary Williamsburg, VA 23185 ------------------------------------------------------------------------------------
