Development of a new voltage stability index and its implementation considering voltage measurement uncertainty

In this study, a new method is proposed to analyse steady-state voltage stability under load variations. This method combines a weighted sum of two voltage stability indices: one derived from power flow equations, and another from the decay of voltage magnitudes. The weight value of each index is updated using an algorithm based on a backwards Euler approximation. In addition, the impact of uncertainty related to voltage measurements on the prediction of voltage instability is mathematically quantified using this new index. The obtained formula shows a reduction in the capability of the proposed stability index in predicting voltage instability when the amplitude of measurement uncertainties increases. Thus, an appropriate filtering technique is added in parallel to the developed index, which proves to reduce the adverse impacts due to uncertain measurements. Simulation studies are performed using four test cases: 5-bus, IEEE 14-bus, IEEE 57-bus, and IEEE 118-bus systems. The obtained results show that the proposed index, named as global voltage stability index, is effective when compared to other voltage stability indices such as voltage collapse prediction index, voltage collapse index, and local Thévenin index.