Dear MATPOWER community, I have a question regarding adding DC lines to an AC system with the “toggle_dcline" command.
I am running a 1100-bus system, using IPOPT as solver. When I solve the standard ACOPF system, the simulation converges within 7 seconds (40 iterations). Now when I add one DC line of 10 MW capacity, applying the “toggle_dcline” command, the system needs 38 seconds (310 iterations) to converge. Since I have not really changed the system with adding one single 10 MW DC line, the results between both cases are 99.99% identical. So why is it, that the DC-line case needs so much more iterations to converge (factor 5 more)? The parameters of my fictitious DC line are: PMAX = +10 MW PMIN = -10 MW QMINF, QMINT both = -10 MVAr QMAXF, QMAXT both = +10 MVAr VF, VT both = 1.0 p.u. LOSS0 = 0.1 LOSS1 = 0 (since I want to enable the code to use the DC in both directions, following a comment in the MATPOWER manual) Have I messed up the definition of the DC line? If not, is there a workaround to bring individual DC lines into a predominantly AC system without having a runtime penalty of factor of 3-5? Or do I just need to re-adjust several parameters of the IPOPT solver to set it up for new constraints of the type “lower bound only”? In the AC-only system, I only have “both lower and upper bound” constraints, so maybe my IPOPT is set up to handle only those constraints properly? Any hints would appreciated. Thanks a lot. Best, Patrick Eser
