Accuracy analysis of fixed voltage setpoint indices for voltage stability

There are many voltage stability indices for voltage security assessment and calculating stable margins from operating points to voltage instability at each load bus. Among them, one type of indices based on fixed voltage setpoint is applied in practice. Previous research has proved inaccuracy of these indices with the P-V curve method. This paper aims to verify the accuracy of these indices by theoretical analysis with a first-order induction motor model and dynamic time domain simulation using a third-order induction motor model. It briefly reviews the accuracy analysis of voltage stability indices based on fixed voltage setpoint by the P-V curve method. Then theoretical analysis and dynamic time domain simulation are performed on a simple system to verify these indices based results. Results obtained from both theoretical calculation and dynamic simulation reveal that fixed voltage setpoint indices are neither accurate nor adequate, just as the P-V curve method suggests.