Hi Russ,
I suspect the models may not be identical. Are they using the model shown in
the MATPOWER User’s Manual<https://matpower.org/docs/MATPOWER-manual-7.1.pdf>
in Fig 3-1 with an ideal transformer in series with a pi-model? If not, that
would explain the discrepancy.
I don’t have those books handy, so feel free to send me (off-list please) the
PDFs of the relevant pages, as it would be useful to confirm.
Thanks,
Ray
On Jan 4, 2021, at 11:19 AM, Russ Patterson
<[email protected]<mailto:[email protected]>> wrote:
Hi Ray,
I’ve chewed on this a while and it looks like the MATPOWER approach is
equivalent to the circuit below for the off-nominal transformer (#2). The
<image001.png> I show is based on <image002.png> for both transformers (#1 is
at nominal tap, #2 is at tap of 1.0502). The <image003.png> below is =
<image004.png>. This is the <image001.png> that MATPOWER builds. The
secondary bus voltage is then 0.976 pu.
<image005.png>
Below is what you get if you follow the approach that Gross1, Neunswander2, and
Kusic3 use (attached).
<image006.png>
Although the MATPOWER approach and Gross approach result in different
<image007.png> matrices, they result in nearly exactly the same secondary bus
voltage because the ratio of <image008.png> in both are nearly identical.
It seems to me that the <image001.png> created by MATPOWER may be wrong when
off-nominal taps are used. I say that with a large dose of humility because
surely I am missing something. But, it seems clear that either Gross or
MATPOWER is wrong here. What am I missing?
References (I can provide pdf of the pages if needed):
1 – “Power System Analysis”, 2ed, Charles A. Gross (p. 204)
2 – “Modern Power Systems”, John. R. Neunswander (p. 251)
3 – “Computer-Aided Power System Analysis”, George L. Kusic (p. 95)
Best regards,
Russ
From:
[email protected]<mailto:[email protected]>
[mailto:[email protected]] On Behalf Of Ray Daniel
Zimmerman
Sent: Monday, December 21, 2020 11:44 AM
To: MATPOWER-L
Subject: Re: circulating current (MVAR loss)
I suggest double-checking your calculations against the code in makeYbus.m,
which is pretty straightforward, and the model described in the User’s
Manual<https://matpower.org/docs/MATPOWER-manual-7.1.pdf> see Figure 3-1 and
equation (3.2). Be sure to keep in mind the orientation of the taps in the
model.
Ray
On Dec 16, 2020, at 3:52 PM, Russ Patterson
<[email protected]<mailto:[email protected]>> wrote:
Carlos – thank you. Very helpful.
The YBus I get for my case is below. I expected Y(1,1) to equal the of this
sum: (1/j0.1) + (1/j0.09522) + (1/-j1.991) = j 19.9997 (negative sign is per
coder preference). Is attached (page 1) not how MATPOWER would modify the
bank #2 impedances before creating YBUS?
Yb =
Compressed Column Sparse (rows = 2, cols = 2, nnz = 4 [100%])
(1, 1) -> 0 - 19.0663i
(2, 1) -> 0 + 19.5217i
(1, 2) -> 0 + 19.5217i
(2, 2) -> 0 - 20i
Best regards,
russ
From:
[email protected]<mailto:[email protected]>
[mailto:[email protected]] On Behalf Of Carlos E
Murillo-Sanchez
Sent: Wednesday, December 16, 2020 4:12 PM
To: MATPOWER discussion forum
Subject: Re: circulating current (MVAR loss)
Russ Patterson wrote:
Hi - I am still trying to hand calculate the flow into branch 2 from bus 1 to
bus 2. I can’t get my results to match MATPOWER.
I get Q into the banks from bus 1 of,
Bank #1: 24.00 MVAR
Bank #2: -25.02 MVAr
Attached is my short calculation and the .m file. Is there a way to have
MATPOWER barf out the YBUS matrix?
>> help makeYbus
If buses are numbered consecutively starting from 1 in the bus table (see
ext2int if not), simply type:
>> mpc = loadcase('mycase');
>> [Yb, Yf, Yt] = makeYbus(mpc)
To get all the relevant current injections in the solved case, simply do
>> mpc = runpf(mpc);
>> define_constants;
>> V = mpc.bus(:, VM) .* exp(1i * mpc.bus(:, VA)*pi/180);
>> Ibus = Yb * V
>> Ifrom = Yf * V;
>> Ito = Yt * V;
From there, compute power injections as
>> Sbusinj = V .* conj(Yb * V);
>> Sfrominj = V(mpc.branch(:, F_BUS)) .* conj(Yf * V);
>> Stoinj = V(mpc.branch(:, T_BUS)) .* conj(Yt * V);
carlos.
<power.pdf>
<image021.png><image007.png><image001.png><image012.png><image014.png><image022.png><image011.png><image005.png><image013.png><image020.png><image003.png><image019.png><snip.pdf>
