Letter to the Editor: Risk Index Functions of Voltage Instability with Load Changes

Abstract Based on a new optimization model of maximizing the load level for voltage stability and Monte Carlo simulation, three risk indices of voltage instability in the form of a function of load level are developed to quantify the overall voltage instability risk of a system with load changes under multiple system states and load uncertainty. These indices are obtained in one single Monte Carlo run and directly provide the quantified relationship between voltage instability risk and load level. The effectiveness of the proposed method is demonstrated using the IEEE 57-bus system.