Sorry i get it,
abs(a*exp(x))=a
so
a*exp(x)/abs(a*exp(x))=exp(x)
sorry for my mistake
Thank you very much
Abdelkrim
Le 20/11/2015 11:59, ALI ZAZOU Abdelkrim a écrit :
Thank you very much for your explainations and advices.
So to understand how matpower operate i looked at "MATPOWER:
Steady-State Operations, Planning, and Analysis Tools for Power
Systems Research and Education" and the calcultion done in matlab but
i'm stuck with something.
In dSbus_dV.m where it's supposed to calculate the partial derivative
of the complex bus power injection, to proceed at one iteration of the
newton's method, i can't understand how you introduce Vm and Va in
Sbus expression.
i supposed that you used the expression:
U=Vm*exp(j*Va)
So logically:
dV/dVm=exp(jVa)
but what you explained is:
% Partials of V & Ibus w.r.t. voltage magnitudes
% dV/dVm = diag(V./abs(V))
% dI/dVm = Ybus * dV/dVm = Ybus * diag(V./abs(V))
and
dV/DVa=j*Vm*exp(jVa)<---- this one seems ok
% Partials of V & Ibus w.r.t. voltage angles
% dV/dVa = j * diag(V)
% dI/dVa = Ybus * dV/dVa = Ybus * j * diag(V)
Can you explained to me so how you get dV/dVm ???
Thank you very much for your reactivity
Abdelkrim
Le 19/11/2015 00:15, Carleton Coffrin a écrit :
Hi Abdelkrim,
I would recommend you have a look at the paper,
Baran, M.E.; Wu, F.F., "Optimal sizing of capacitors placed on a
radial distribution system," in Power Delivery, IEEE Transactions on ,
vol.4, no.1, pp.735-743, Jan 1989
It has a nice mathematical formulation of how voltage drops in a
radial system, based on the power flow on the lines.
Cheers,
-Carleton
On Nov 19, 2015, at 7:15 AM, Ray Zimmerman <[email protected]> wrote:
In general, the voltage tends to drop as you get further from the
source, if loads are evenly distributed and line parameters are
similar. In your example, however, you have a much larger load at bus
9 than at bus 8, and in particular, there is a large reactive load at
9, pulling down the voltage. The low load at 8 and the relatively
large line charging capacitance of the 8-9 line help to support the
voltage at 8, relative to 9.
Ray
On Nov 18, 2015, at 11:11 AM, ALI ZAZOU Abdelkrim
<[email protected]> wrote:
Hi,
my question is about the voltage level of each buses in a radial
distribution system. My understanding of this phenomena is that the
voltage level of the "farest" (in term of r and x) bus will have the
lowest voltage level if there is no generation or voltage regulator
between the slack bus and that bus? Am I getting it wright?
Because in the above example, based on the modified iee9_bus case
given by the tool, i get a strange behaviour. The last bus (8) don't
have the lower votage level, so based on that how can that factor be
explained?
You can find attached to the email, the test case and a figure of
the graph of the network.
Thank you very much for reading my question
Abdelkrim
<9_modif.png><case9_modif.m>
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