A Framework for Qualitative Analysis of Voltage Stability Indices (VSIs)

Voltage stability assessment (VSA) is invariably an essential step in the satisfactory operation of power system. For this, several Voltage Stability Indices (VSIs) based on 1) Existence of solution for voltage equations, 2) Maximum power transfer (MPT) through a line, 3) MPT theorem/maximum loadability limit, 4) P-V curve, 5) Energy function and 6) Jacobian matrix can be found in the literature. VSIs assist in identifying weak lines and buses, voltage collapse proximity, maximum loadability, voltage stability margin, and prompting countermeasures against voltage instability. This article examines 78 different VSIs based on their concepts, assumptions, thresholds, and formulae. Additionally, mathematical proofs for 29 indices have been elaborated upon so that researchers may familiarize themselves with the underlying concepts of the other existing indices and find newer indices in modern power systems composed of intermittent power generation and dynamic loads. Also, a novel qualitative comparative analysis of VSIs is tabulated. Further, a novel framework has been proposed to aid researchers in shortlisting VSIs for a particular application. This article intends to serve as a meaningful reference to various researchers and individuals working in domains like Distributed Generation (DG) placing and rating, Voltage Stability Assessment (VSA), and power system planning.