Thank you for the clarification and hint for further study.
2014-03-11 14:53 GMT+01:00 Ray Zimmerman <[email protected]>: > You are correct. Typical simple power flow models assume a constant power > (independent of voltage) for loads and generators. Some software models > load using a "ZIP" model, that is, a combination of constant impedance, > constant current and constant power elements. This gives the flexibility to > more accurately reflect a load's actual relationship between voltage and > power. Currently MATPOWER does not include a ZIP load model, though the > constant impedance portions could be placed in the GS and BS columns of the > bus matrix, though they would not be reported as part of the load. > > Ray > > > On Mar 11, 2014, at 5:53 AM, mateusz wanka <[email protected]> > wrote: > > > Dear all, > > > > I'm starting to model and analyse power systems and I've decided to use > Matpower. I have a question regarding creating admittance matrix which is > needed to performe a load flow. Text books say that diagonal elements of > this matrix is a sum of admittances all branches connected to a particular > node and 'include also the admittance to ground of line charging > susceptance and any other fixed admittance to ground' (from 'Power System > Analysis' by H.Saadat). There is also presented a way how to convert > impedance diagram of a system into the admittance diagram and the > admittance matrix of such a systm is calculated. The diagonal elements > include also admittance of the current sources. (chapter 6 of the book) > > > > My question is: why in Matpower (but also in examples of power flow > calculations from above book) we don't consider admittance of > sources/loads? Is this because we assume that there are 'ideal power > sources/consumers' with constant power and if we considered internal > admittances, their power would be variable and depending on the system load > and therefore couldn't be PQ-nodes anymore? Similarly for PV- and slack > node? > > If not, what is a reason for that? I cannot find any explicit > explanation in the literature. > > > > Thank you in advance and best regards, > > Mateusz Wanka > > > >
