On the configuration of the US Western Interconnection voltage stability boundary

Stability limits are considered in power system planning and operations to estimate the available stability margins and, if possible, to maximize the use of transmission facilities. These important tasks are influenced by configuration of the voltage stability boundary. This paper first propose a new method to explore static voltage stability conditions in Cartesian coordinates instead of polar coordinates. In this way, the formulated singularity problem can be reduced to solving a set of linear equations with respect to real and imaginary components of nodal voltages. Using the proposed method, several case studies were performed for 17939-bus U.S. Western Interconnection planning model. Significant peculiarities of the boundary configuration were identified, including its non-convexity, discontinuity, branching and internal singularities (“holes”) that were not known before and could not be found by traditional methods.