The context of the error message is important. In this case, it has nothing to do with the ill-conditioning of a matrix encountered by MIPS in the AC OPF solution, rather the ill-conditioning of a matrix encountered in forming the PTDF. I suppose it's possible that the same underlying network conditions could cause both.
Are you sure that the remaining system is fully-connected? I suspect that the PTDF calculation may encounter singular matrices if the network is not connected, though I haven't tested it. I suggest converting the indexing to a consecutive internal ordering (and removing out-of-service branches, buses, etc) by calling ext2int() after setting the line statuses to zero and before calling makePTDF(). -- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Feb 28, 2012, at 7:29 AM, Ravikumar V wrote: > Hi Trivik Verma, > > This is Matlab error message appears when the matrix inverse is not possible > because of singular matrix. This shows that the power system becomes > unhealthy or ill-conditioning because of opening several lines. Kindly refer > previous posts on this topic. > > http://www.mail-archive.com/[email protected]/msg01678.html > > > > On Tue, Feb 28, 2012 at 4:05 PM, Trivik <[email protected]> wrote: > Could anyone help me?? > > I am viewing a power grid using MATPOWER and for my simulations I need to > remove a node together with its links. By doing so, I am changing > mpc.branch(links,:) = 0. After removing the respective links, I am > calculating PTDFs again. The first time is fine, but in the event of > redistribution of flows, the next time I am removing about 10 percent of the > nodes and calculating PTDFs. I get a warning as follows, > > Warning: Matrix is close to singular or badly scaled. > Results may be inaccurate. RCOND = 4.060450e-019. > > Do I have to remove something else from the mpc struct as well? > > cheers, > Trivik > > > > ------------------------------------------------------------- > WITH REGARDS, > > V. Ravikumar Pandi, > Masdar Institute, Abu Dhabi, > United Arab Emirates - 54224. > mobile : +971 5522 78027. > ------------------------------------------------------------- > HAVE A NICE DAY > ------------------------------------------------------------- >
