On Jul 4, 2008, at 2:10 AM, hamid tahery2009 wrote:
hello
I'm student of electrical engeenearing.Ihave some questions about
opf at matpower.at"poewer system analysis" by Johnj.grainger
and WilliamD.Stevenson- i understood for computation lambda we have
gencost function (Quadratic function like C= aP^2 +bP+c)
and lambda=dc/dp , and for optimal power flow all the lambdas must
be equal.but at matpower when we run the opf ,for each bus
we earn one lambda.i want to know what function we use and how it
compute.(for example for PQ buses.)
For an optimal power flow, the lambdas are only equal when the system
is lossless and there are no transmission limits. In a general AC OPF,
the lambda at any given bus is equal to the sensitivity of the system
cost to changes in load at that bus. This will, in general, be
different for each bus. These values are computed as the shadow prices
on the nodal power balance equations. Each algorithm has it's own
method for computing them.
another question , at help IDX_BUS it said :" bus(:, VMIN) = 0.95;
% set the min voltage magnitude to 0.95 at all buses"
but when you type it at matlab prompt it never influence our
computation.please help me about this .(have can i set the min
voltage magnitude to 0.95 at all buses)
VMIN is simply a constant (13) that allows you to access the 13th
column of the bus matrix by name as opposed to having to remember
which column it is. You can either change this data directly in the
case file (13th column of the bus matrix). Or you can read it into
some variables, change it and then call the desired solver using the
modified data. For example,
mpc = loadcase('case30'); %% load the matpower case
mpc.bus(:, VMIN) = 0.95; %% modify the VMIN column of the bus matrix
runopf(mpc); %% run the OPF using this modified data
(Btw, seems like you've got an enthusiastic e-mail client ... I got 5
copies of your e-mail ... :-)
--
Ray Zimmerman
Senior Research Associate
428-B Phillips Hall, Cornell University, Ithaca, NY 14853
phone: (607) 255-9645
