Dear Ben,
Thank you for your interest. Yes I am studying transient stability and using
the IEEE 118 bus model. I would like to reduce it to have just the generator
buses by eliminating all the load buses. What I have done so far; I obtained
the Ybus from MATPOWER and wrote a MATLAB code to do Kron reduction. My main
aim is to obtain the reduced Ybus matrix. But I would like to verify my reduced
Ybus by doing a Powerflow analysis on it and comparing the result to that of
the original (unreduced) model which is available on MATPOWER. I would like to
know if that’s possible. Another thing I was thinking was using the network
reduction toolbox available on MATPOWER. I understand MATPOWER used a modified
Ward reduction so I am expecting some differences in the 2 reduced matrix but I
guess the power flow should be the same. Is this assumption right? Also, I
would be glad if my code to obtain the reduced matrix is right. I have it here;
define_constants;
mpc = loadcase('case118');
mpc.bus(38, BUS_TYPE) = 4; %Removing the Bus
mpc.branch(51, BR_STATUS) = 0; %Removing branches connecting Bus 38 to the
network
%(using their respective branch #s. See
runpf('case118'))
mpc.branch(54, BR_STATUS) = 0;
mpc.branch(96, BR_STATUS) = 0;
r = runpf(mpc);
%To now generate the reduced faulted Ymatrix
ExBus =
[118,117,115,114,109,108,106,102,101,98,97,96,95,94,93,88,86,84,83,82,81,79,78,75,71,68,67,64,63,60,58,57,53,52,51,50,48,47,45,44,43,41,39,38,37,35,33,30,29,28,23,22,21,20,17,16,14,13,11,9,7,5,3,2]';
[mpcreduced,Link,BCIRCr]=MPReduction(mpc,ExBus,0)
[Y1] = ext2int(mpcreduced)
[Yfaulted] = makeYbus(Y1)
Thank you.
From: [email protected]
[mailto:[email protected]] On Behalf Of Ben Ubah
Sent: Monday, August 08, 2016 4:25 PM
To: MATPOWER discussion forum <[email protected]>
Subject: Re: Ybus-matrix
@Philip
What do you intend to achieve overall? What is the end result of your
simulation? It would help someone to advice you better.
Kron reduction is usually done for the purpose of simplifying a system for
studies like transient stability or coherent generators.
Make your end-point clear so that one can know exactly where to help.
Ben
On Monday, August 8, 2016 6:21 PM, Carlos E Murillo-Sanchez
<[email protected]<mailto:[email protected]>> wrote:
Hmm... that is an odd question. Looking at the Kron reduction myself, I find
that there are six off-diagonal elements with positive real parts, which would
imply six "lines" in this 54 bus "network" with negative resistance. I suppose
that you could actually synthesize values for pi models that would give you the
observed coefficients in the reduced matrix, but some of the parameters would
not be physically possible.
carlos.
Philip Adedotun Olaniyi wrote:
Thank you so much sir. My next question would be, is it possible to compute the
bus and branch tables from the 54-by-54 admittance matrix? Thank you
From:
[email protected]<mailto:[email protected]>
[mailto:[email protected]] On Behalf Of Carlos E
Murillo-Sanchez
Sent: Friday, August 05, 2016 11:10 AM
To: MATPOWER discussion forum
<[email protected]><mailto:[email protected]>;
[email protected]<mailto:[email protected]>
Subject: Re: Ybus-matrix
When you simplified away the PQ buses, you lost the ability to specify loads in
them. So, theoretically, you could perform a load flow in which you can only
have loads at the 54 generator buses. You cannot use runpf, though, as runpf
starts by building the Ybus matrix from the bus and branch tables; it does not
take Ybus as an input. You would have to call newtonpf.m directly with
suitable parameters.
carlos.
Philip Adedotun Olaniyi wrote:
Hi MATPOWER community,
I asked a question earlier and would like to modify it. I have a reduced
54-by-54 admittance matrix for case118. Can I use this as an input in MATPOWER
for my power flow analysis? How do I go about it?
I would appreciate your help. Thank you.
