  Recent development of techniques that improve the convergence properties of
power flow simulation have been demonstrated to facilitate scaling to large
system sizes (80k+ buses). However, the problem remains to reliably identify
cases that are infeasible, system configurations that have no solution. In this
paper, we use the circuit theoretic approach based on adjoint networks to
evaluate the feasibility of a power flow test case and further locate and
quantify the source of infeasibility in the cases operating beyond the tip of
the nose curve. By creating infeasibility current source models that are added
to each node of the system model and further coupling each source to its
corresponding node of the adjoint network, any locations of insufficient real
or reactive power are captured by a non-zero response of the adjoint network.
Furthermore, it is shown that the proposed joint simulation of power flow and
its adjoint network models provide the optimally minimized currents that can be
later utilized to inform corrective actions to restore the feasibility of power
flow problems.
