0.5 degree might be possible if the termination criteria for the power flow is rather large. If small termination tolerances do not improve the match, it must be a difference in modeling somewhere.
-- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Oct 16, 2013, at 11:40 PM, jiji aminudin <[email protected]> wrote: > Hi > > Thanks for the feedback, Ray. Now I know why the losses are different > (Question 1-anwered). For Question 3, I did use the same data for both > Matpower and the other software, but the voltage angle still not tally. At > base case, the difference is roughly <0.5 degree. Can I just ignore it? > > To other Matpower forum members, please, i really need a hand to answer > Question 2. I would appreciate if you could run the load flow for IEEE24 bus > and email me the result. Since I'm afraid the problem is not cause by > Matpower but from myself. Perhaps I did some errors during installation parts > (some of the tests failed) and I just want to check whether it affects the > results. > > Thank you > > On Tue, Oct 15, 2013 at 10:15 PM, Ray Zimmerman <[email protected]> wrote: > On Oct 13, 2013, at 7:46 AM, jiji aminudin <[email protected]> wrote: >> Dear all, >> >> I’m using Matpower to run load flow for IEEE-24 bus system. I would >> appreciate if anybody can help me on the followings: >> >> 1) I just wonder why the difference between buses’s sending power and >> buses’s receiving power (for branch) doesn’t tally with the resulted line >> losses? For example (please refer to highlighted area in the attachment), at >> branch 1, bus 1 is sending 11.94-j26.92MVA and bus 2 receives >> -11.94-j22.45MVA. Logically, the losses will be 0-j4.47MVA >> ([11.94-j26.92MVA]-[-11.94-j22.45MVA]). But, the resulted line loses >> connecting the two buses are 0.004+j0.02MVA. Is that possible? >> >> > The losses that are reported are only the series losses (I^2 * Z) and do not > include the reactive power injected by the line-charging elements of the > transmission model. This is simply a matter of defining clearly which losses > you are including. You will notice that in the System Summary section of the > output, the Losses are reported separately from the Branch Charging. > >> 2) Is anybody here working on the same system as I am? Can you help me to >> verify the result (please refer to attachment)? >> >> 3) I’ve compared the result with other load flow software. It seems that the >> voltage magnitude and active power losses do not differ much. But, the >> voltage angle and reactive power losses vary significantly. Isn’t all the >> results should be approximately the same? >> > The voltage angle results should be exactly the same assuming the input data > is identical. The loss numbers may be different if other load flow software > lumps the branch charging together with the series losses, otherwise they > should also be identical. > > > > -- > Ray Zimmerman > Senior Research Associate > B30 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > >
