Yes. I am making the line status zero and also making the removed buses as isolated. But apart from that is there anything else that I should change in the vectors of the mpc struct? I am still getting that warning with a smaller PTDF matrix generated this time.
On Tue, Feb 28, 2012 at 5:11 PM, Ray Zimmerman <[email protected]> wrote: > 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 > ------------------------------------------------------------- > > >
