Emergency Voltage Stability Controls: an Overview

This paper provides an overview of emergency voltage stability controls in power systems. First, a brief review is made of voltage instability mechanisms, countermeasures, and system protection schemes. Next, the paper discusses various aspects of emergency controls, including generator voltage control, load tap changer modified control and load shedding, pointing out some important features and addressing research aspects. Load shedding is considered in some more detail, and applications to two real systems of, respectively, a response-based and an event-based load shedding scheme, are described.