  Fundamental sensor feedback limitations for improving rotor angle stability
using local frequency or phase angle measurement are derived. Using a
two-machine power system model, it is shown that improved damping of inter-area
oscillations must come at the cost of reduced transient stability margins,
regardless of the control design method. The control limitations stem from that
the excitation of an inter-area mode by external disturbances cannot be
estimated with certainty using local frequency information. The results are
validated on a modified Kundur four-machine two-area test system where the
active power is modulated on an embedded high-voltage dc link. Damping control
using local phase angle measurements, unavoidably leads to an increased rotor
angle deviation following certain load disturbances. For a highly stressed
system, it is shown that this may lead to transient instability. The
limitations derived in the paper may motivate the need for wide-area
measurements in power oscillation damping control.
