Robust self healing two-level state estimation in systems with optimally allocated PMUs

This paper presents a robust self healing algorithm for the two-level state estimation (SE), including both the substation and control center levels. The SE is based on the presence of phasor measurement units (PMUs) at the substations. Even though the cost of PMUs has been decreasing lately, logistic, economic and design aspects limit the installation of PMUs at all nodes of electric grids. Therefore, an optimal PMU allocation method for substations is also proposed. The proposed allocation method ensures reliability in the SE process even in cases of PMU malfunctioning. PMUs and measurement losses, security and observability issues are discussed. The combination of the optimal PMU allocation and self healing SE results in an economically attractive option that is able to preserve the system´s observability in case of loss of PMUs and measurements.