Methods of determining weak transmission stability boundaries are deve
loped based on the strong controllability and observability properties
of power systems. This theory has been applied [251 to a dynamical mo
del of the generators and network. It was established [25] that the ne
twork and generator states associated with a cluster of generator and
load buses surrounded by weak transmission boundaries are strongly con
trollable and observable for a single measurement and control at gener
ators or load buses in that bus cluster. Such a bus cluster is called
a control area. Two methods of determining control areas, where strong
controllability and observability hold, are developed in this paper.
Both methods attempt to determine weak transmission stability boundari
es that encircle control areas. The groups of generators identified as
belonging to each control area is identical to the groups of coherent
generators determined using a rms coherency measure evaluated for the
set of all inertial load flow contingencies [11, 12].