Hi Ray,
Thank you,
I found out there must be 1 at the tap to make Matpower understand the
branch as transformer,
this is ok, and the impedance in per unit, 14% is 0.14.
For example branches:
1 2 0.001 0 0 250 250 250 0 0 1 -360 360; Is a power cable
2 3 0.001 .105 0 250 250 250 1 0 1 -360 360; Is a transformer
impedence 10.5%
2 4 0.001 .12 0 250 250 250 1 0 1 -360 360; Is a transformer
impedence 12%
What I don't understand, as you stated, is where do we specify the
transformer MVA rating, which
should take part in the calculation except my misunderstanding.
For instance both are 16 MVA transformers.
So I just set the above values and made a calculation without indicating
the transformer apparent
power, as I could not find if it matters and where to specify.
Regards,
Jean-François
Le 09/08/2021 à 16:42, Ray Daniel Zimmerman a écrit :
Yes, in the current MATPOWER case format v2, the transformers are specified in
the same branch matrix as the AC transmission lines. I’m a bit rusty on my
transformer modeling, so someone please correct me if I’m wrong, but I believe
the % impedance specification is equivalent to the p.u. impedance value
expressed using the transformer rated power and voltages as the per-unit bases.
So I think you just have to convert the impedance to the system per-unit bases
to put it in the branch matrix.
Ray
On Aug 2, 2021, at 9:49 AM, Jean-Francois Simon <jfsi...@startmail.com> wrote:
Good day,
I am learning MatPower and have a case to study with 8 buses. The below example
a simplification:
I could understand how to build buses and links and simulate the energy flow.
Results look right,
however I have a question since the buses are working on different voltage
levels, hence some
links have power transformers.
*** Bus 2: 90 kV - Feeder bus ***
*** Bus 3: 30 kV - Load bus ***
*** Bus 5: 690 V - Load bus ***
<Bus 2>---(90/30kV XFR)---<Bus 3>---(30/.69 kV XFR)---<Bus 5>
Bus 2 to bus 3 is a 16 MVA transformer with impedance 10.5%
Bus 3 to bus 5 is a 5 MVA transformer with impedance 6.5%
At the moment, the bus definition looks like this:
mpc.bus = [
2 3 0.0 0.0 0 0 1 1 0 90.0 1 1.1 0.9;
3 1 7.2 2.1 0 0 1 1 0 30.0 1 1.1 0.9;
5 1 3.5 0.1 0 0 1 1 0 0.69 1 1.1 0.9;
];
And branches definition is incomplete:
mpc.branch = [
2 3 0.1 0 0 250 250 250 0 0 1 -360 360;
3 5 0.1 0 0 250 250 250 0 0 1 -360 360;
];
Is this right transformers are set in "Branches" ? How do we calculate and set
resistance branches
resistance and and reactance in order to properly integrate transformers as for
example in above
case ?
Thank you for support,
Regards,
Jean-François Simon
