Dynamic Vulnerability Assessment and Intelligent Control

Chapter 10Voltage Stability Enhancement by Computational Intelligence Methods

Worawat Nakawiro

Lecturer in Electrical Power Systems, Department of Electrical Engineering, Faculty of Engineering, King Mongkut's Institute of Technology Ladkrabang, Bangkok, Thailand

10.1 Introduction

Present day power systems are highly stressed conditions due to several factors such as stronger competition in generation sectors, inadequate transmission expansion [2], intermittent renewable sources and heavy use of induction machines. With these factors, a power system becomes more vulnerable to various types of unstable behaviour among which is voltage stability. This has been reported as the cause of various incidents throughout the world over the last decades, such as those in the western region (WECC) of the United States in 1996, the Chilean power system in 1997 (accounting for a loss of 80% of its total load) and the Greek system covering the whole of Athens and the neighbouring area in 2004 [1].

Voltage stability is defined as the ability to maintain an acceptable voltage profile in many parts of the system after being subject to disturbances such as gradual load increases or outages of critical lines or generating units [6]. After these events, some loads may try to restore power consumption according to their load dynamics. This may drive the weakened power system closer to the technical limits, which can lead to voltage collapse.

Several voltage stability indices have been proposed in ...