ad 1) the most conservative approach would be that you compute a dispatch that 
will be secure in nominal case and in all contingency scenarios, however 
restrictive this might be. Considering N-1 security of line failures, you 
simple replicate all mismatch equations and line power flow limits of nominal 
case for each contingency with changes in grid connectivity - i.e, first build 
admittance matrices from mpc structure where a single branch is deleted from 
mpc.branch (representing your contingency) and then compute bus and branch 
power flows for each scenario and evaluate jacobian/hessian of constraints and 
objective function using these different admittance matrices (see 

ad 2) I have implemented the approach described above, you can find the code in 
my fork of Matpower https://github.com/goghino/matpower. Simply run the SCOPF 
problem by specifying a list of branches that you want to cut and run the 

mpc = loadcase('case9');
contingencies = [1:nbrch];
mpopt = mpoption('opf.ac.solver', 'IPOPT', 'verbose', 2);
runscopf(mpc, contingencies, mpopt);

There is an interface to MIPS and IPOPT solvers, but MIPS has troubles with 
converging to the solution since the problem is very ill-conditioned. I am 
currently investigating why the linear systems are so ill-conditioned. If you 
have any ideas why this ill-conditioning occurs let me know.

Hope this helps.

Juraj Kardos
Advanced Computing Laboratory
Institute of Computational Science
Universita della Svizzera italiana
Via Giuseppe Buffi 13
Lugano 6904

On 10 Aug 2017, at 22:37, Brandon Eidson 
<eids...@gmail.com<mailto:eids...@gmail.com>> wrote:


I have been writing code to implement basic power/optimization calculations.  I 
started with power flow, then DC power flow, then OPF.  I have been using 
MATPOWER as a source of case systems and to check my results.

I am in the process of implementing N-1 (in hopes of moving on to N-1-1).  I 
need help on two fronts.

1) I am having trouble understanding the workflow/algorithm for these.  Some 
appear to find violations for different contingencies and then stop.  Others 
appear to use the violations and update the OPF constraints to pursue a new 
dispatch that will result in no violations in the base case and in as many as 
possible contingency cases.

a) Are those broad descriptions of the workflow in the ballpark?

b) Given the iterative/decomposed approach is correctly described above, what 
are the new constraints that are added to the OPF problem in order to find a 
new dispatch?  I can't just keep adding "assume 0 flow on this branch that 
caused a violation" constraints.

2) If someone has non-propitiatory code that uses MATPOWER to calculate N-1 
and/or N-1-1 SCOPF, I would appreciate that being passed along.  I'm hoping to 
keep checking my code using reasonably tested code.    I suppose this could 
also be a way of answer question 1b.

Glad to be apart of this list,

Reply via email to