Fault Tolerance and Security for Power Grid Confguration with FACTS Devices

Missouri University Of Science And Technology, Rolla MO

Investigators

Abstract

This award is made under the Exploratory Research on Engineering the Transport Industries (ETI) program solicitation. Bulk power systems form one of the largest and most complex inter-connect transportation networks ever built. These net-works throughout the world consist of large numbers of energy sources operating in near synchronism coupled through a high-voltage AC transmission system. As power systems have evolved, the dominant bulk power system has been formed as large groups of closely coupled machines connected by one or more transmission links. This situation has devel-oped as a consequence of growth in interconnections among regional power systems. With increasingly heavier power transfers, such systems become vulnerable to cascading failure as dynamics can couple throughout the system in unpredictable ways, Cascading failures may be brought on by naturally occurring events, or may be induced through terrorist-type activities. Examples of naturally occurring cascading failures include the infamous New York blackout in 1965 and more recently, the two California blackouts of July and August 1996. Control of the power network has traditionally been decentralized due to geographic and regulatory constraints. The nodes (called "buses") in a power system are often geographically remote from one another with little or no systematic communication between them, making coordinated control difficult. Also, different regions of the national power grid may be owned by independent private or public entities whose operating venues differ. This, too, poses difficulties in coordinated control. One of the most promising decentralized network controllers is the family of power electronics-based controllers, known as "flexible AC transmission system" (FACTS) devices. These devices locally modify the topology of the system by rapid switching. By the choice of switching patterns, these devices can achieve a variety of power system objectives, such as voltage support, oscillation damping, and stability improvement. This ability can be used for not only reliability objectives such as increasing the maximum throughput power, but can also be used to adjust power flow for economic reasons. In the power system restructured environment, it is foreseeable that power flows will be adjusted throughout the system to maximize economic objectives. These devices, however, are relatively new and few are cur-rently beyond the prototype stage, therefore their wide-spread impact on the transmission network has not yet been thoroughly analyzed. While these devices offer increased network power flow controllability, the decentralized nature of their actions may cause deleterious interactions between them. In this project, we propose to utilize flexible topology FACTS devices in developing distributed control strategies to i) detect and mitigate intentional or unintentional cascading failures, ii,) develop operating strategies that can automatically adjust to changing economic and physical environments, and iii) develop interaction policies to mitigate counterproductive actions.