  This paper introduces a two-level robust approach to estimate the unknown
states of a large-scale power system while the measurements and network
parameters are subjected to uncertainties. The bounded data uncertainty (BDU)
considered in the power network is a structured uncertainty which is inevitable
in practical systems due to error in transmission lines, inaccurate modelling,
unmodeled dynamics, parameter variations, and other various reasons. In the
proposed approach, the corresponding network is first decomposed into smaller
subsystems (areas), and then a two-level algorithm is presented for state
estimation. In this algorithm, at the first level, each area uses a weighted
least squares (WLS) technique to estimate its own states based on a robust
hybrid estimation utilizing phasor measurement units (PMUs), and at the second
level, the central coordinator processes all the results from the subareas and
gives a robust estimation of the entire system. The simulation results for IEEE
30-bus test system verifies the accuracy and performance of the proposed
multi-area robust estimator.
