Distributed Slack with ACOPF - Multiple connected slacks in one area found. This would probably lead to non-convergence of the OPF. Therefore, all but one slack (ext_grid) were changed to gens. To avoid undesired behaviour, rather convert the slacks to gens yourself and set slack=True for only one of them.

[PB-vines]

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Issue

I have a transmission grid with the following specs:

• bus (6717 elements)
• load (4541 elements)
• sgen (63 elements)
• gen (668 elements)
• shunt (367 elements)
• line (7173 elements)
• trafo (1967 elements)
  I want 5-8 gen.slack = True. I need to run this for ACOPF, DCOPF, and ACPF. Regardless if I use gen.slack = True or external grids, I get the following message:
  "Multiple connected slacks in one area found. This would probably lead to non-convergence of the OPF. Therefore, all but one slack (ext_grid) were changed to gens. To avoid undesired behaviour, rather convert the slacks to gens yourself and set slack=True for only one of them." I get this message anytime I have more than 1 gen.slack = True or external grid when running ACOPF and DCOPF. The PF is fine.

I have seen other comments related, like the one below, with no resolve.
#1163 (comment)

Any conclusions on this? @rbolgaryn @lthurner @FlorianShepherd.

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