The detection, prevention and mitigation of cascading outages in the power system
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This dissertation studies the causes and mechanism of power system cascading outages and develops new methods and new tools to help detect, prevent and mitigate the outages. Three effective solutions: a steady state control scheme, a transient stability control scheme, and an interactive system-wide and local scheme have been proposed using those new methods and tools. A steady state control scheme can help detect and prevent the possible cascading outage at its initial slow steady state progress stage. It uses new methods and new tools to solve the line overload, congestion or bus high/low voltage problems. New methods, such as vulnerability index (VI), margin index (MI), network contribution factor (NCF), topology processing and selected minimum load shedding (SMLS), and new tools, such as transmission network control based on a network contribution factor (NCF) method, generator control based on a generator distribution factor (GDF) method, and load control based on a load distribution factor (LDF) method have been proposed and developed. A transient stability control scheme can help prevent and mitigate the possible cascading outage at its transient progress stage if there is enough time to take action. It uses one Lyapunov direct method, potential energy boundary surface (PEBS) method, and sensitivity analysis of transient energy margin for fast stabilizing control. The results are verified by the accurate time-domain transient stability analysis method. The interactive scheme takes advantage of accurate system-wide and local information and analysis results, uses some techniques from both steady state control and transient stability control, works at both the system-wide level and local substation level, monitors the system all the time, and takes actions when needed to help detect, prevent and mitigate the possible cascading outage. Comprehensive simulation studies have been implemented using the IEEE 14- bus, 24-bus, 39-bus and 118-bus systems and promising results show the ability of the proposed solutions to help detect, prevent and mitigate cascading outages.