  We consider a linear power flow model with interval-bounded nodal power
injections and limited line power flows. We determine the minimal number of
power injections to control based on a minimal set of measurements, such that
the overall system is feasible for all assignments of the non-controlled power
injections. For the important case where the possible measurements are the
nodal power injections, we show that the problem can be solved efficiently as a
mixed-integer linear program (MILP). When also line power flows are considered
as potential measurements, we derive an iterative, greedy algorithm that
provides a feasible, but potentially conservative solution. We apply the
developed algorithms to both a small microgrid and a modified version of the
IEEE 118 bus test power system. We show that in both cases a sparse solution in
terms of the number of required controllers and measurements can be obtained.
Moreover, the number of required measurements can be reduced significantly if
line flow measurements are considered additionally to nodal power injections.
