  Nonconvexity induced by the nonlinear AC power flow equations challenges
solution algorithms for AC optimal power flow (OPF) problems. While significant
research efforts have focused on reliably computing high-quality OPF solutions,
it is not always clear that there exists a feasible path to reach the desired
operating point. Transitioning between operating points while avoiding
constraint violations can be challenging since the feasible space of the OPF
problem is nonconvex and potentially disconnected. To address this problem, we
propose an algorithm that computes a provably feasible path from an initial
operating point to a desired operating point. Given an initial feasible point,
the algorithm solves a sequence of convex quadratically constrained
optimization problems over conservative convex inner approximations of the OPF
feasible space. In each iteration, we obtain a new, improved operating point
and a feasible transition from the operating point in the previous iteration.
In addition to computing a feasible path to a known desired operating point,
this algorithm can also be used to improve the operating point locally.
Extensive numerical studies on a variety of test cases demonstrate the
algorithm and the ability to arrive at a high-quality solution in few
iterations.
