This paper proposes a decentralized derivative-free
dynamic state estimation method in the context of a power system
with unknown inputs, to address cases when system linearisation
is cumbersome or impossible. The suggested algorithm tackles
situations when several inputs, such as the excitation voltage,
are characterized by uncertainty in terms of their status. The
technique engages one generation unit only and its associated
measurements, and it remains totally independent of other system
wide measurements and parameters, facilitating in this way the
applicability of this process on a decentralized basis. The robust-
ness of the method is validated against different contingencies.
The impact of parameter errors, process and measurement noise
on the unknown input estimation performance is discussed. This
understanding is further supported through detailed studies in a
realistic power system model.