Model-free voltage stability assessments via singular value analysis of PMU data

Ill-conditioning of the power flow, reflected in high sensitivity of bus voltage magnitudes to load variation, often serves as a basic indicator of vulnerability to voltage instability. This sensitivity may be quantified by the induced 2-norm associated with the power flow Jacobian inverse, as may be computed from Singular Value Decomposition(SVD). While this conceptual picture is simple, near-real-time assembly of the power flow Jacobian under volatile operating conditions, and monitoring its singular values, presents severe computational and data management problems. As an alternative, work here will propose a “model-free” voltage stability and conditioning monitor, based solely on phasor measurement unit (PMU) data, arguing that such an approach is much better suited to near-real-time application. We first review singular value analysis in voltage stability assessment, and relate these existing approaches to our proposed method. We offer computational evidence that the proposed measure closely tracks the largest singular value of the inverse of the power flow Jacobian under continuous change in operating point, without the need for any network admittance data nor construction of the power flow model. This work goes on to examine characteristics of the PMU-based SVD measure in scenarios of discontinuous changes to network topology. We demonstrate that the new measure also provides a highly sensitive indicator of the occurrence of topology change, that may offer a valuable “consistency check” to supplement directly reported breaker status.