الفهرس | Only 14 pages are availabe for public view |
Abstract Power systems today are made up of thousands and thousands of different components. They are widely and, in some cases, massively spread over vast lands and territories. Hence reliability and security of their operation is no longer an easy target. Challenges in maintaining healthy operation are magnified and elevated by the power system size. Despite huge advancements in different power system components, operations, and protection technologies, today’s power systems are more vulnerable to blackouts than ever before. Recorded major blackout incidents have been classified according to time and location. This showed that the frequency of their occurrence has increased over time. It is not realistically possible to completely eliminate blackouts; however, it can be shown that by taking some reasonably cost-effective measures, occurrence of the blackouts could be minimized and/or their effects could be mitigated. Clearly, the most straightforward way is to minimize the risk of inadvertent disturbances by mitigating, as far as possible, the root causes of system disturbances through analyses and audits, preventive and corrective actions and Public policy, Transmission, and future investments. One of the recommended preventive plans against the wide area disturbances and the blackouts is Wide Area Protection. With the rapidly growing capabilities in computer and communication technologies, opportunities are now being available for the introduction of advanced wide-area protection and control systems which show great potential. Such systems would receive wide-span information, e.g. system-wide voltages, angles, active and reactive power flows, etc., and analyze them, indicating whether the system is on the urge of a transformation into an unstable state, and thus, issuing wide-span, coordinated actions that will save the system from proceeding to total collapse, or even, mitigate the wide-area disturbance effects upon the system. System splitting, also known as controlled separation, is to split the interconnected transmission network, deliberately and on purpose, into islands of load with matching generation at proper splitting points by opening a selection of transmission lines and ties. After which, load shedding and sometimes generation rejection should follow in order for the load and generation to remain within balance, keeping the majority of the system intact and hence avoid cascading instabilities or even partial or total blackouts. The study of previous blackouts and outages suggest that if proper system splitting strategies along with suitable load shedding and minimized generator rejection had been performed within short time, some blackouts could have been avoided and mitigated. In this thesis the author is proposing three simple real-time algorithms that are intended to be operating online, analyze data from wide-area PMUs placed in different parts of the grid, process the system state and lines’ status and issue disconnecting actions to certain lines in the grid to form islands with minimum imbalances of power between generation and loads, without violating thermal and overloading constraints of the ties left intact within each island. First a simple approach is introduced, which takes long times and performs an extensive search for proper splitting strategies. The author then analyzes the operation of this preliminary algorithm and comments on ways to enhance its performance. This will emphasize on how such WAP systems would be designed and developed and if necessary tailored to fit specific systems or applications. The author then presents the modified approach that suggests that some of the work must be done off-line and leave the decision making to be real-time but within much shorter times. Another technique is explored which is based on Angle-modulated Particle swarm optimization and its results are commented on showing potential of such optimization techniques in the field of controlled separation. At last, a third heuristic technique introduced for the first time is presented and its results are also highlighted and shown to achieve the best results when related to time, which makes it a possible implementation as an on-line, real-time, solution. Then a brief portrait of how would such system exist in a today’s modern smart grid is made with some useful guides for further implementation and research. Keywords: Blackouts, Wide Area Protection, Controlled Separation, Angle Modulated Particle Swarm Optimization. |