[Couenne] a non-convex problem

[mahbube zeraatzade]

Hi, I have been working on AC Optimal Power Flow for a while. The AC OPF is naturally a non-convex problem. The AMPL file that I have written works perfectly with all of the Mixed Integer Non-Linear solvers on the NEOS site. IEEE 5-Bus and 14-Bus are used to check the results.
The referees of the Journal that I had sent my paper, believed that these test systems are small and the methodology should be checked on a real system. Therefore I am testing the real power system of a country with 1388 buses and 1212 lines. 
I have entered a Snap Shot of the network as the starting point and have run the program with all the possible assumptions but can't get any feasible solution.
When I use Couenne as the solver, I get the following results:
****************************************************************************** 
Job 2379178 has finished.
Job 2379178 sent to e032.chtc.wisc.edu
password: tYaAJeBv
---------- Begin Solver Output -----------
Executing /opt/neos/Drivers/couenne-ampl/couenne-driver.py
File exists
You are using the solver couenne.
Executing AMPL.
processing data.
processing commands.

Presolve eliminates 4268 constraints and 9191 variables.
Adjusted problem:
Error: Error at _cmdno 3 executing "solve" command
3913 variables:
Error: (file amplin, line 2727, offset 199919):
	3329 nonlinear variables
Error: can't open /tmp/neos-29505/at29512.sol
	584 linear variables
4547 constraints; 21611 nonzeros
	4543 nonlinear constraints
	4 linear constraints
1 linear objective; 584 nonzeros.

couenne: 
ANALYSIS TEST: Problem size before reformulation: 3913 variables (0 integer), 4547 constraints.
Problem size after  reformulation: 26548 variables (0 integer), 3043 constraints.
 warning, tightened NLP is infeasible
problem infeasible
 Error (512) in /opt/ampl/ampl -R amplin
*******************************************************************************************

Can the limitaions on NEOS server be the reason of the infeasible solution?
Does reducing the size of the problem by ommitting some buses and lines can help to get a feasible solution?
I thank you in advance for your help.
Regards,
Mahbube
 
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