SVD-Based Voltage Stability Assessment From Phasor Measurement Unit Data

Electric power systems can display a range of undesirable dynamic phenomena by which acceptable, stable operation may be lost. Quasi-steady-state operational problems such as the voltage instability phenomena are among these. Ill-conditioning of the power flow, reflected in high sensitivity of bus voltage magnitudes to load variation is an often observed precursor to such quasi-steady state operational problems. Motivated by this insight, work here will propose a voltage stability and conditioning monitor that is model-free in real-time, based solely on phasor measurement unit (PMU) data, arguing that such an approach is well suited to near-real-time application. We review model-dependent singular value analysis in voltage stability assessment, and relate these existing approaches to our proposed model-free method in real-time application. The proposed algorithm is first applied under the idealized assumption of full measurement data at all buses. This work then extends the algorithm to apply in the more practical case for which only subset of buses have available measurement data. The proposed approach is illustrated in IEEE test cases, augmented to include heavy load conditions that stress voltage stability. Algorithms for efficient computation of small numbers of singular values, as well as means to exploit low-rank updates in data, are reviewed to demonstrate opportunities for fast computation that allow these SVD methods to operate in near-real-time in large systems.