  A robust observer for performing power system dynamic state estimation (DSE)
of a synchronous generator is proposed. The observer is developed using the
concept of $\mathcal{L}_{\infty}$ stability for uncertain, nonlinear dynamic
generator models. We use this concept to (i) design a simple, scalable, and
robust dynamic state estimator and (ii) obtain a performance guarantee on the
state estimation error norm relative to the magnitude of uncertainty from
unknown generator inputs, and process and measurement noises. Theoretical
methods to obtain upper and lower bounds on the estimation error are also
provided. Numerical tests validate the performance of the
$\mathcal{L}_{\infty}$-based estimator in performing DSE under various
scenarios. The case studies reveal that the derived theoretical bounds are
valid for a variety of case studies and operating conditions, while yielding
better performance than existing power system DSE methods.
