Is the initial power flow feasible? My guess is that the initial power flow is violating one of the generator limits, so when you enforce them with the OPF, the solution is no longer feasible.

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Ray > On Aug 8, 2017, at 3:45 AM, prem panigrahi <prempanigr...@outlook.com> wrote: > > > Dear all > I am facing problem in DCOPF. I need help. In my power grid model > i have fixed the capacity of transmission line in RATE A column by 110% of > initial power flow. Then increase the load by a factor (1.01) and run the > dcopf. But matpower showing infeasible model due to which it is not > converging. I am not able to understand the problem. Here load and generation > is also well balanced. Now which parameter constraint to converging of my > test case. I stuck here for a long time, so please help me > > > > The result shown below is after increasing the load by 1.01. > > > MATPOWER Version 6.0, 16-Dec-2016 -- DC Optimal Power Flow > Gurobi Version 7.0.2 -- automatic LP solver > Optimize a model with 19515 rows, 4968 columns and 47500 nonzeros > Coefficient statistics: > Matrix range [2e-03, 9e+05] > Objective range [1e+02, 2e+02] > Bounds range [5e-03, 1e+02] > RHS range [3e-17, 4e+02] > > Concurrent LP optimizer: dual simplex and barrier > Showing barrier log only... > > Presolve removed 2 rows and 17 columns > Presolve time: 0.06s > > Solved with dual simplex > Solved in 0 iterations and 0.07 seconds > Infeasible model > > >>>>> Did NOT converge (0.17 seconds) <<<<< > > > > > > Checking connectivity ... single fully connected network > Elapsed time is 0.051284 seconds. > ================================================================================ > Full > System > Number of: ---------- > buses 3989 > loads 2227 > on 2227 > off - > fixed 2227 > dispatchable - > on - > off - > generators 979 > on 979 > off - > shunt elements 247 > branches 8096 > on 8096 > off - > ties (off) - > > Load > active (MW) > dispatched 85879.4 > fixed 85879.4 > dispatchable - > nominal 85879.4 > on 85879.4 > off - > fixed 85879.4 > dispatchable - > on - > off - > reactive (MVAr) > dispatched 23668.6 > fixed 23668.6 > dispatchable - > nominal 23668.6 > on 23668.6 > off - > fixed 23668.6 > dispatchable - > on - > off - > > Generation > active (MW) > dispatched 86451.8 > max capacity 213706.7 > on 213706.7 > off - > min capacity -72665.3 > on -72665.3 > off - > reactive (MVAr) > dispatched 24069.5 > max capacity 69809.7 > on 69809.7 > off - > min capacity -50352.2 > on -50352.2 > off - > > Shunt Injections > active (MW) - > reactive (MVAr) 10848.8 > > Branch Losses > active (MW) - > reactive (MVAr) - > > DC line > export (MW) > dispatch - > max capacity - > on - > off - > min capacity - > on - > off - > > Reference Buses > num of ref buses 1 > ref bus numbers 3292 > > > From: bounce-121637002-78651...@list.cornell.edu > <bounce-121637002-78651...@list.cornell.edu> on behalf of Ray Zimmerman > <r...@cornell.edu> > Sent: Monday, July 3, 2017 9:33:26 PM > To: MATPOWER discussion forum > Subject: Re: DCOPF not converging for large system > > 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 >> <mailto: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> >