Dear Walter, This my idea: In Optimal Power Flow we have *Objective function* (Like Cost minimization and etc) and we are giving "*Limits*" for " Pg, Qg" as control variables and " Um, Ua" as state variables. "Limits" for line loading is not mandatory but it is our inequality constraints in case of consideration . Solvers like NR, MIPS or fmincon then will try to fulfill Pi and Qi (PF equations for each bus) as equality constraints and fulfill line loading as an inequality constraint in a way that non of those "Limits" mentioned above being exceeded. So solver needs to solve Pi and Qi equations with *4 variables* (Pg, Qg, Um and Ua) each time to find at the end *the best solution* to satisfy our objective function, equality constraints and inequality constraints. You can find PF equations in Constraint functions of each solver.
But in Power Flow or Load Flow there is *no Objective function *to be fulfilled. We solve Pi and Qi equations with certain input. Solvers like NR solve Pi and Qi equations (PF equations) with some assumptions (like type of buses PV, Slack and PQ) and Qg limits and U limits. So 2 equations with* 2 Variables* is needed to be solved in each iteration. Best Wishes, Ehsan On Mon, Oct 30, 2017 at 10:35 AM, Sun Weigao <[email protected]> wrote: > Dear Matpower users, > > > > I have a confusing problem when I am doing some research to improve the > optimization of PF problem and OPF problem both. > > > > I solve the PF problem by Newton-Rapfson (NR) method, and OPF problem by > Primal-dual Interior Point method (PDIPM). I want to figure out the > relationship between the PF and OPF solving process. > > > > Do we need a complete PF solving process (using NR) during the OPF solving > process (using PDIPM)? In other words, Does the solving process of the OPF > problem (using PDIPM) contains many PF calculations? If Yes, in which step > the PF is calculated ? and if No, why ? > > > > I've been puzzled by this problem for a long time, please help if you > clear the answer. > > Thank you very much. > > > > Sincerely, > > Walter > > >
