Hi Richaed:
i did bwefore Load Flow for the electrical power system in the westren region
of Saudi Arabia. it was very large system and have used the load flow data from
the PSS/E like your case exactly. it was required from me to do Load Flow first
in Matlab and the results should be compared to PSS/E load flow to make sure
that we are in the righr direction.
all the date was intered in PSS/E is in per-unit and and there was no need to
change any values. it was surprising to me and my supervisor why is that PSS/E
is using negative impedance in one winding for modeling the transformer . after
a search on this area, i have understood that this might be for representing
the leakage !! not sure.
However, what u have to do to make the loadflow analysis in Matlab is to put
the -ve value as a negative in the Trasmission line matrix. just put it as it
is simply.
then run load flow and it should give you identical results like PSS/E
solution.just make sure that u input the right tap changers values as written
in the PSS/E
Best of Luck
Basem
> Date: Thu, 3 Jun 2010 01:10:31 +0100
> Subject: Three winding transformers
> From: [email protected]
> To: [email protected]
>
> Hello,
>
> I have a PSS/E model that I would like to solve power flows for with
> MATPOWER, but it contains a three winding transformer. The PSS/E
> manual mentions that these devices are represented internally by three
> two-winding transformers and a fictitious neutral bus. To calculate
> the r and x for each of the transformers I have been using the
> equations:
>
> r1 = 0.5 * (r12 + r31 - r23)
> x1 = 0.5 * (x12 + x31 - x23)
> r2 = 0.5 * (r12 + r23 - r31)
> x2 = 0.5 * (x12 + x23 - x31)
> r3 = 0.5 * (r23 + r31 - r12)
> x4 = 0.5 * (x23 + x31 - x12)
>
> However, this does result in negative values for certain windings.
> The magnetizing susceptance is given as a single value in the PSS/E
> file, so I have just been dividing it equally between the three
> branches. Does anyone have experience modelling three-winding
> transformers with MATPOWER, who might be able to tell me if I am
> missing anything or if I am on the right tracks?
>
> Regards,
>
> Richard
>
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