I think if you plot the quadratic cost functions that you are using
for gen 3 reactive power, it will be clear what is happening. Here's
the code I used to plot the two cases.
>> x = [-15:15]';
>> yp = 0.0625 * x .^ 2 + x;
>> yn = 0.0625 * x .^ 2 + 10 * x;
>> plot(x, yp)
>> plot(x, yn)
In particular, in the case where the objective function value is
negative, it's because gen 3 has a reactive power cost of about -136
when dispatched at it's lower limit of -15.
0.0625 * (-15)^2 +10 * (-15) = -135.9375
Maybe you wanted to increase the quadratic coefficient in the cost
instead of the linear coefficient?
--
Ray Zimmerman
Senior Research Associate
428-B Phillips Hall, Cornell University, Ithaca, NY 14853
phone: (607) 255-9645
On Jun 4, 2009, at 4:06 PM, Gabox . wrote:
Dear Prof. Zimmerman, thank you very much for answering.
Please find the attached files to follow my explanation.
I did a runopf('case2Q_PosTotalCost') and later
runopf('case2Q_NegTotalCost')
If you compare both case files the only difference is at Gen 3 which
it is 10 times more expensive.
Why do I get negative prices? Shouldn't I get higher OPF costs for
having a more expensive system?
I would expect that the system with more expensive MVAR prices to
have higher total OPF costs but it gives negative OPF costs.
I use the Matpower 3.2 and I have updated all the toolboxes
I appreciate your help and thank you for sharing this excellent tool
Kindest regards
Gabriel
From: [email protected]
To: [email protected]
Subject: Re: Reactive Power Bug
Date: Thu, 4 Jun 2009 15:42:36 -0400
Negative prices could be correct depending on the costs. Could you
please send me an example case file that exhibits the issue along
with an explanation of what you expected to be different from the
output MATPOWER gives?
--
Ray Zimmerman
Senior Research Associate
428-B Phillips Hall, Cornell University, Ithaca, NY 14853
phone: (607) 255-9645
On Jun 4, 2009, at 3:27 PM, Gabox . wrote:
Dear Sirs,
I use the OPF tools of matpower to test the effect of Reactive Power
prices.
I build a case file similar to case30Q.m and I considered the
reactive power prices.
A generator dispatched with negative MVAR caused to get a wrong
total cost of the OPF
In the case of dispatching only negative MVAR, the OPF will get
negative total costs.
Is this a bug or there is another way to introduce reactive power
prices in the case files?
Could there be a missing abs() in the MVAR pricing?
I would appreciate your comments and help
Kind regards
¡Es hora que descubras quién sos! Alguien puede conocerte mejor que
vos mismo.
Tus elecciones hablan por vos. ¡Conocé quién sos realmente!
<MVARcasesRunOPF.txt><case2Q_PosTotalCost.m><case2Q_NegTotalCost.m>
