I. Introduction
When it comes to power systems, voltage stability is a critical issue that has existed for many years. It can be defined as “After being subjected to a disturbance from a given initial operating state, it is the capacity of a power system to sustain steady voltages at all the system buses [1]. Voltage stability and voltage collapse have been a great subject of study. Despite the low possibility of voltage collapse, its effect is surely large. Several massive blackouts reportedly resulted from voltage collapse [2]. Voltage is a certain bus parameter. However, under certain conditions, voltage drop at a bus in the power system may have a significant effect on the overall system.