If you have a solved AC power flow, that’s a good start. Normally, the first
step I try when faced with an OPF that won’t converge is to eliminate the
branch flow limits by setting the RATE_A column of the branch matrix to zero
(or by increasing the values by some factor). In your case, you can check which
flows in the power flow solution exceed their limits and only relax those to
begin with.
If I were you, I would relax any branch, voltage and generator limits as
required to make the power flow solution you have feasible for the AC OPF
problem. It should solve. If it does, then you can begin to eliminate those
relaxations to find the source of the infeasibility.
Ray
> On Jun 23, 2017, at 10:55 AM, Mort D. Webster <md...@psu.edu> wrote:
>
> Dear Matpower Folks:
>
> I have larger network that is a solved load flow case from an ISO.
>
> The AC power flow converges fine, but neither AC nor DC OPF solve.
>
> I supplied my own estimated generator costs, and perturbed them so that none
> are identical.
>
> I get the following error:
>
>> >> mpc = iso2015sum
>>
>> mpc =
>>
>> version: '2'
>> baseMVA: 100
>> bus: [7108x13 double]
>> gen: [720x25 double]
>> branch: [8930x13 double]
>> bus_name: {7108x1 cell}
>> dcline: [4x17 double]
>> gencost: [720x6 double]
>>
>> >> results = rundcopf(mpc)
>>
>> opf_setup: Warning: Multiple reference buses.
>> For a system with islands, a reference bus in each island
>> may help convergence, but in a fully connected system such
>> a situation is probably not reasonable.
>>
>>
>> MATPOWER Version 6.0b2, 01-Nov-2016 -- DC Optimal Power Flow
>> The interior-point-legacy algorithm uses a built-in starting point;
>> ignoring supplied X0.
>> Exiting: One or more of the residuals, duality gap, or total relative error
>> has stalled:
>> the primal appears to be infeasible and the dual unbounded since
>> the dual objective > 1e+10
>> and the primal objective > -1e+6.
>>
>> >>>>> Did NOT converge (7.52 seconds) <<<<<
>>
>>
>> results =
>>
>> version: '2'
>> baseMVA: 100
>> bus: [7108x17 double]
>> gen: [720x25 double]
>> branch: [8930x21 double]
>> bus_name: {7108x1 cell}
>> dcline: [4x17 double]
>> gencost: [720x6 double]
>> order: [1x1 struct]
>> om: [1x1 opf_model]
>> x: [7700x1 double]
>> mu: [1x1 struct]
>> f: 2.1192e+06
>> var: [1x1 struct]
>> lin: [1x1 struct]
>> et: 7.5220
>> success: 0
>> raw: [1x1 struct]
>
> The system has several complex features:
>
> 4 HVDC lines
>
> several storage resources as generators
>
> 4 buses as reference/slack bus type
>
> many "isolated" bus types ("4").
>
> Can you suggest where in the results I can look to diagnose the problem?
>
> Thanks so much!
>
> Mort Webster
> --
> Mort Webster
> Associate Professor of Energy Engineering
> Dept of Energy and Mineral Engineering
> Pennsylvania State University
> University Park, PA 16802
> (814) 863-1640
> m...@psu.edu <mailto:m...@psu.edu>
