Hello Dominic, Probably you are confusing what is the objective of each routine:
On one hand opf tries to minimize the production cost subject to voltage constraints : Vmin<= V <= Vmax (for all buses, even PV buses) and other network constraints, therefore, opf does not fix the terminal voltage of the generators. On the other hand pf solves and obtain an equilibrium point that satisfy power balance equations, but, in this case pf fixes the terminal voltage the generators (PV buses) Vk == Vref. IMHO that is the reason why your are experiencing those differences. Best, Uriel > El 28/01/2015, a las 10:42, Hewes, Dominic <dominic.he...@tum.de> escribió: > > Dear Matpower Community, > > I am observing a strange problem whereby the results from a successful > 'runopf()' do not seem to present a solved power flow case. I want to verify > the power flow solution from an OPF by running a PF with the OPF results as > the mpc struct. Firstly, the 'runpf()' converges in 1 iteration, whereas i > would expect a solved case to converge in 0 iterations- am i mistaken here? > Secondly, when i use the 'compare_case()' command to compare the OPF results > with the resulting PF results, I see that there are large differences between > the solutions. My code is as follows: > > resultsOPF=runopf(mpc123); > resultsPF=runpf(resultsOPF); > > compare_case(resultsOPF, resultsPF) > > The comparison shows a maximum reactive power difference of 494 MVAR between > the generator results: > > gen > PG 5.00578e-10 9.67145e-09 9.17088e-09 614 > QG 7.99959e-11 494.118 494.118 218 * > > The OPF command converges successfully with no error warnings, and so I > assumed that running the results struct through a PF command should give the > same power flow solution. Am i mistaken here? If my thinking is correct, > this would indicate that the optimiser has provided results that do not > represent a feasible power flow solution - is this potentially a bug? I have > tested the same method on the 'case14.m' file and observe that this also > requires 1 iteration to converge and gives very small differences (~2e-7) > between the OPF and PF results. > > I am using the latest matpower release (5.0), the TSPOPF 5.0 solver and a > windows 7 machine (see output of mpver at end of email). I have tried with > other solvers and observe the same problem. I am working with a large model > (>5000 bus) that i have attached below. Could the size of my model be the > cause of this problem? > > Presently I am not sure whether I am making a simple mistake or if there is a > bug in the solver that is causing the output of inaccurate results. > > Has anyone experienced similar problems? I would very much appreciate any > advice on the cause of the problem. > > Kind Regards, > > Dominic > > > mpver > > MATPOWER Version 5.0 17-Dec-2014 > MATLAB Version 8.4 08-Sep-2014 Release: (R2014b) > Optimization Toolbox Version 7.1 08-Sep-2014 Release: (R2014b) > MIPS Version 1.1 17-Dec-2014 > SDP_PF -- not installed -- > YALMIP -- not installed -- > BPMPD_MEX -- not installed -- > CPLEX Version 12.6.0.0 PCWIN64 > Gurobi -- not installed -- > GLPK -- not installed -- > IPOPT -- not installed -- > KNITRO -- not installed -- > MINOPF -- not installed -- > MOSEK -- not installed -- > PDIPMOPF Version 5.0 17-Dec-2014 PCWIN64 > SCPDIPMOPF Version 5.0 17-Dec-2014 PCWIN64 > SDPT3 -- not installed -- > SeDuMi -- not installed -- > TRALMOPF Version 5.0 17-Dec-2014 PCWIN64 > Architecture: PCWIN64 > <mpc123.mat>
