Hi Sashi, The issue here is the definition of the term "branch flow" in the case when you have a lossy branch. I'm not sure there is a universally accepted convention. Once you define the term, it should be easy to compute the "flow". For example, you might use something like the average of PF and -PT.
And no, you won't see both flows (PF and PT) being negative since that would imply negative losses (unless you have some strange negative resistances or something). With reactive power, on the other hand you might see this case, where the line is a net generator of reactive power. -- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Oct 3, 2013, at 5:06 AM, Sashireka Appalasamy <[email protected]> wrote: > Hi Dr. Zimmerman, > > Just to let you know that currently I am analyzing branch flows in a > modified IEEE 118 benchmark problem. I have observed that there exists cases > as given in red below in where the To and From bus P value is (+) which means > that it is giving to each other, hence the losses is the sum of both the (+) > values, hence does this mean that the flow is 0 on this branch? and is there > possibility for both to and from end to be receiving from each other too > (both P values (-)). And if there is than what is the branch flow? > > > > Branch Data > | > ======================================================================== > Brnch From To From Bus Injection To Bus Injection Loss (I^2 * Z) > > # Bus Bus P (MW) Q (MVAr) P (MW) Q (MVAr) P (MW) Q > (MVAr) > 77 54 55 -4.99 -72.73 5.89 74.39 > 0.895 3.74 > 78 54 56 7.75 -633.11 3.53 671.51 > 11.276 39. > > Thank you for your valuable time. > > Sincerely, > Sashi > > > On Thu, Oct 3, 2013 at 3:39 AM, Ray Zimmerman <[email protected]> wrote: > The real power loss in branch k can be computed as ... > > Ploss = results.branch(k, PF) + results.branch(k, PT) > > Also, I just noticed my previous response had an error in it. The voltage > angles used to compute Vf and Vt need to be multiplied by pi/180 to convert > from degrees to radians. > > -- > Ray Zimmerman > Senior Research Associate > B30 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > > On Oct 2, 2013, at 2:18 AM, Muhammad Buhari > <[email protected]> wrote: > >> Hi, >> >> Pls can you help me with an advice on the best method to compute the branch >> losses using matpower >> >> Thanks for your continued assisstance. >> >> Regards >> >> Muhammad Buhari >> >> PhD student >> >> Electrical Energy and Power Systems Research group, >> >> University of Manchester, UK >> >> From: [email protected] >> [[email protected]] on behalf of Ray Zimmerman >> [[email protected]] >> Sent: 30 September 2013 8:22 PM >> To: MATPOWER discussion forum >> Subject: Re: Branch Currents in matpower 4.1 >> >> For branch k, connecting bus f to bus t, you can calculate them directly >> from the bus voltages and branch powers. >> >> Sf = results.branch(k, PF) + 1j * results.branch(k, QF); >> St = results.branch(k, PT) + 1j * results.branch(k, QT); >> Vf = results.bus(f, VM) * exp(1j * results.bus(f, VA)); >> Vt = results.bus(t, VM) * exp(1j * results.bus(t, VA)); >> If = conj( Sf / Vf ); >> %% complex current injected into branch k at bus f >> It = conj( St / Vt ); >> %% complex current injected into branch k at bus t >> >> >> -- >> Ray Zimmerman >> Senior Research Associate >> B30 Warren Hall, Cornell University, Ithaca, NY 14853 >> phone: (607) 255-9645 >> >> >> On Sep 28, 2013, at 11:24 AM, Jiashen Teh <[email protected]> >> wrote: >> >>> Hi >>> >>> I would like to know the method to calculate correctly the branch currents >>> from the matpower results. >>> >>> Regards >>> >>> >>> Yours sincerely, >>> >>> Jiashen Teh >>> PhD Student >>> Electrical Energy & Power Systems Group, School of Electrical & Electronic >>> Engineering >>> Ferranti Building (B18), The University of Manchester, M13 9PL, United >>> Kingdom >>> Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 792 322 4864 >>> From: Muhammad Buhari >>> Sent: 28 September 2013 16:19 >>> To: Jiashen Teh >>> Subject: Branch Currents in matpower 4.1 >>> >>> Hi, >>> >>> Please can you help me with the method to calculate correctly the branch >>> currents from the matpower results. >>> >>> Regards >>> >>> Muhammad Buhari >>> >>> PhD student >>> >>> Electrical Energy and Power Systems Research group, >>> >>> University of Manchester, UK >>> >> >> > >
