1. Unfortunately, "branch power flow" is not a precisely defined term. Your first expression is the apparent power flow at the "from" end of the branch, whereas, mpc.branch(1, PF) is just the real or active power flow. Keep in mind that the flow at the "to" end is likely different, so if you are looking for a single number you may want to average them (you'll need to flip the sign of one of them to that).
2. That row defines the sensitivities of the flow on line 7-8 with respect to an increase in injection at the corresponding bus (with slack at bus 1 decreasing the injection to compensate). Since bus 8 is connected radially to the system at bus 7, increasing the injection at any bus except bus 8 will have no impact on the flow in line 7-8. -- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Aug 1, 2013, at 9:32 PM, Yahook K <[email protected]> wrote: > Dear Dr Zimmerman > > I have 2 questions. > > First, in ac mode, if I want to calculate the branch power flow, take branch > 1 for example, should I use sqrt( mpc.branch(1,PF)^2 + mpc.branch(1,QF)^2 ) > ? Or simply mpc.branch(1,PF) is the branch power flow we meant in the > power system? > > Second, the following is the PTDF matrix for the case14.m(a 14 bus example). > I generate this use makePTDF(mpc.baseMVA,mpc.bus,mpc.branch,1). But I don't > understand why line 14(branch 14) is all zero except column 7(bus 7) . What > does this mean. And if I increase bus 1's power load by 1 MW, when I > runopf(mpc), the power flow of branch 14, is not zero (I use sqrt( > mpc.branch(1,PF)^2 + mpc.branch(1,QF)^2 ) ). > > 0 -0.8380 -0.7465 -0.6675 -0.6106 -0.6291 -0.6573 > -0.6573 -0.6518 -0.6477 > 0 -0.1620 -0.2535 -0.3325 -0.3894 -0.3709 -0.3427 > -0.3427 -0.3482 -0.3523 > 0 0.0273 -0.5320 -0.1513 -0.1031 -0.1188 -0.1427 > -0.1427 -0.1380 -0.1346 > 0 0.0572 -0.1434 -0.3167 -0.2158 -0.2487 -0.2986 > -0.2986 -0.2888 -0.2817 > 0 0.0774 -0.0711 -0.1994 -0.2917 -0.2616 -0.2160 > -0.2160 -0.2249 -0.2314 > 0 0.0273 0.4680 -0.1513 -0.1031 -0.1188 -0.1427 > -0.1427 -0.1380 -0.1346 > 0 0.0799 0.3067 0.5026 -0.3012 -0.0389 0.3584 > 0.3584 0.2808 0.2240 > 0 0.0030 0.0113 0.0186 -0.0111 -0.2075 -0.6338 > -0.6338 -0.4469 -0.4043 > 0 0.0017 0.0066 0.0108 -0.0065 -0.1211 -0.1658 > -0.1658 -0.2608 -0.2360 > 0 -0.0047 -0.0179 -0.0294 0.0176 -0.6714 -0.2004 > -0.2004 -0.2924 -0.3597 > 0 -0.0028 -0.0108 -0.0177 0.0106 0.1979 -0.1207 > -0.1207 -0.1760 -0.2873 > 0 -0.0004 -0.0016 -0.0026 0.0016 0.0291 -0.0177 > -0.0177 -0.0259 -0.0161 > 0 -0.0014 -0.0056 -0.0091 0.0055 0.1017 -0.0620 > -0.0620 -0.0904 -0.0563 > 0 0 0 0 0 0 0 > -1.0000 0 0 > 0 0.0030 0.0113 0.0186 -0.0111 -0.2075 0.3662 > 0.3662 -0.4469 -0.4043 > 0 0.0028 0.0108 0.0177 -0.0106 -0.1979 0.1207 > 0.1207 0.1760 -0.7127 > 0 0.0019 0.0071 0.0117 -0.0070 -0.1307 0.0797 > 0.0797 0.1163 0.0724 > 0 0.0028 0.0108 0.0177 -0.0106 -0.1979 0.1207 > 0.1207 0.1760 0.2873 > 0 -0.0004 -0.0016 -0.0026 0.0016 0.0291 -0.0177 > -0.0177 -0.0259 -0.0161 > 0 -0.0019 -0.0071 -0.0117 0.0070 0.1307 -0.0797 > -0.0797 -0.1163 -0.0724 > > Columns 11 through 14 > > -0.6386 -0.6309 -0.6323 -0.6433 > -0.3614 -0.3691 -0.3677 -0.3567 > -0.1269 -0.1204 -0.1215 -0.1308 > -0.2655 -0.2519 -0.2543 -0.2738 > -0.2463 -0.2587 -0.2564 -0.2387 > -0.1269 -0.1204 -0.1215 -0.1308 > 0.0948 -0.0137 0.0061 0.1607 > -0.3076 -0.2264 -0.2412 -0.3569 > -0.1795 -0.1321 -0.1408 -0.2083 > -0.5128 -0.6415 -0.6181 -0.4348 > -0.5402 0.1683 0.1452 -0.0356 > 0.0061 -0.5211 -0.1697 -0.0887 > 0.0213 -0.2886 -0.5936 -0.3104 > 0 0 0 0 > -0.3076 -0.2264 -0.2412 -0.3569 > -0.4598 -0.1683 -0.1452 0.0356 > -0.0274 -0.1902 -0.2367 -0.6008 > -0.4598 -0.1683 -0.1452 0.0356 > 0.0061 0.4789 -0.1697 -0.0887 > 0.0274 0.1902 0.2367 -0.3992 > > > Thank you very much for your patience. > > Sincerely, > > Yahook > >
