Dear Dr. Zimmerman, Thank you so much for your approach. But I still have several questions.
1. For the two dummy buses, where should I add them? Are they directly connected to the original bus X and Y? Or they are not connected to bus X and bus Y, but have the same buses connection as X and Y? 2. According to step 1, the relaxed line is reconnected to bus X' and bus Y', but in step 6, it seems the line connected to X and Y still exists. Should both the lines connected to X and Y, and X' and Y' exist in the system? Actually I'm not fully understanding why this approach can be equivalent to relaxed the thermal limit constraints on a specific branch. Can you explain the theory of the approach more in detail? Thank you! Best Regards, Jiazi On Tue, Sep 23, 2014 at 1:20 PM, Ray Zimmerman <[email protected]> wrote: > There isn’t a really easy to solve what you want with the current version > of MATPOWER, but I think it should be possible to do it with a few “tricks”. > > For a branch between bus X and bus Y ... > > 1. Add two dummy buses X’ and Y’ and reconnect the line to X’ and Y’ > instead of X and Y. > 2. Add dummy generators at X, X’, Y and Y’ with PMIN = –M, PMAX = M, where > M is some value larger than the max flow on the line (even in the relaxed > solutions). > 3. Add user-defined linear constraints to enforce equality between the Pg > of dummy gen at X and -Pg of dummy gen at X’, and likewise for dummy gens > at Y and Y’. > 4. Set the cost on each of the dummy generators to a piecewise linear > function that is zero up to the original line limit value, and some large > value above that. > 5. Add user-defined linear constraints to enforce equality between the > voltages (magnitudes and angles) at X and X’ and at Y and Y’. > 6. Remove or relax the original line limit on the line itself. > > I don’t think I’ve never tried this, so I’d be interested in hearing how > well it works if you decide to attempt it. > > -- > Ray Zimmerman > Senior Research Associate > B30 Warren Hall, Cornell University, Ithaca, NY 14853 USA > phone: (607) 255-9645 > > On Sep 23, 2014, at 5:51 AM, Jiazi Zhang <[email protected]> wrote: > > Dear all, > > > I'm running AC OPF using Matpower for my project and for some cases, the OPF > does not converge due to the capacities of several branches are not enough. > > I'd like to relax the thermal limit constraints on these branches with large > penalty factors. But the power flow thermal limit constraints are nonlinear > for AC OPF. I wonder if it is possible to do such branch limit relaxation in > AC OPF program. > > > Best Regards, > > Jiazi > > > -- > Jiazi Zhang > Research Assisant > School of Electrical, Computer & Energy Engineering > Ira A. Fulton Schools of Engineering > Arizona State University > [email protected] > > > -- Jiazi Zhang Research Assisant School of Electrical, Computer & Energy Engineering Ira A. Fulton Schools of Engineering Arizona State University [email protected]
