Static Voltage Stability

This is a stability phenomenon, where the power system looses its ability to control load bus voltage due to various reasons. This phenomenon can lead to failure of the total or partial power system due to interventions of various control and protection actions.

The reasons for voltage instability could be

- Failure to provide necessary power support to the loads as a consequence of power transfer limit. The power transfer limit is determined not only by the bus voltage phase angle, but also by bus voltage magnitude

- Failure to meet power requirements due to equipments reaching their control and operating limits. Examples are transformer tap limits, generator reactive power supply capabilities.

- Inconsistency in the load power requirements as function of bus voltage and power supply characteristics.

PowerApps provides various analytical tools for assessment of static voltage stability using load flow solution or output from static state estimation. Further the reactive power optimization algorithm provides a method of improving static voltage stability. The analytical tools are

V-P (nose) curves or PV curves
Sensitivity Indices. Sensitivity of bus voltage magnitude for active (P) and reactive (Q) injection at a bus.
Sensitivity of net reactive power generation for a given bus reactive power injection.
Minimum Singular Value Decomposition of the complete load flow Jacobian as well us reduced Jacobian formulations. [ P.A.Lof, T.Smed, G.Andersson, D.J.Hill – Two IEEE Transaction publications, 1992, 1993]. Further, identification of critical buses based on left and right singular vectors are also implemented in PowerApps.
Voltage Stability Index L proposed by P.Kessel and H.Glavitsch. [ IEEE Transactions on Power Delivery, 1986].
Static Voltage Stability Evaluation using relative bus voltage phasors at an operating point given by load flow solution or static state estimation.. [A New and Fast Technique for Voltage Stability Analysis of a Grid Network Using System Voltage Space", Published in International Journal of Electrical Power & Energy Systems, Elsevier Science Ltd. UK .]
Improvements in static voltage stability using a reactive power optimization tool. [Optimal Static Voltage Stability Improvement Using a Numerically Stable SLP Algorithm, for Real Time Applications", Published in International Journal of Electrical Power & Energy Systems, Elsevier Science Ltd. UK ]