  Deregulation of energy markets, penetration of renewables, advanced metering
capabilities, and the urge for situational awareness, all call for system-wide
power system state estimation (PSSE). Implementing a centralized estimator
though is practically infeasible due to the complexity scale of an
interconnection, the communication bottleneck in real-time monitoring, regional
disclosure policies, and reliability issues. In this context, distributed PSSE
methods are treated here under a unified and systematic framework. A novel
algorithm is developed based on the alternating direction method of
multipliers. It leverages existing PSSE solvers, respects privacy policies,
exhibits low communication load, and its convergence to the centralized
estimates is guaranteed even in the absence of local observability. Beyond the
conventional least-squares based PSSE, the decentralized framework accommodates
a robust state estimator. By exploiting interesting links to the compressive
sampling advances, the latter jointly estimates the state and identifies
corrupted measurements. The novel algorithms are numerically evaluated using
the IEEE 14-, 118-bus, and a 4,200-bus benchmarks. Simulations demonstrate that
the attainable accuracy can be reached within a few inter-area exchanges, while
largest residual tests are outperformed.
