Electric power system is a fundamental infrastructure of modern society. A magnicent property of electric power system { security, is achieved by keeping it operated in a secure state at most of the time. Security means the ability to withstand imminent disturbances or contingencies, such as electric short circuits or unanticipated loss of system elements, without interruption of customer service. This thesis proposes methods to secure power system operation from classifying threat origins to power system security, analyzing power system steady-state security, splitting power system network intentionally to increase power system transient stability. Maintaining electric power system secure is a very challenging interdisciplinary multidimensional problem, which is impacted by a large amount of factors, such as extreme weather conditions and unexpected disturbances. In order to achieve keeping the system secure, pursuing a better understanding of all kinds of origins of threats to electric power system is meaningful. Identifying and classifying potential threats to electric power system help to design corresponding measures to tackle them. Moreover, due to impossibility of considering countless threats with nite resource, quantifying and ranking the risks of threats contribute to level up eciency and eectiveness. When power system in a normal, alert, or emergency state, steady-state security analysis, as a branch of power system security analysis, is an eective tool to provide information for operators to design control to mitigate power system progressing into a extremis state. Conventionally, most analysis methods for steady-state security are "point-wised", which means that they considering operational points by checking all components' electrical quantities. However, this sort of method has obvious disadvantages, such as heavy numerical computation and lacking global information. Therefore, "region-wised" method, such as nodal power injections security region and interface power ow security region, with the ability to provide global security information to operators, is promising. Normal, preventive and emergency control measures are eective tools to keep power system security. However, if these measures fail, power system will be placed into a extremis state. Extremely, a cascading spreading of system components outages would result in partial or systemwide blackout (loss of supplied load). In this case, intentional islanding, the ultimate control to preserve as many stable areas as possible, is an eective and promised measure to prevent blackout. In designing a islanding scheme, fast and eectively searching out the optimal MC (minimum cut-set) to split power system network is a conundrum. Moreover, for the large-scale power system, it is even impossible to nd out the best scheme but surrender to suboptimum ones. Genetic algorithm, with excellent optimization capacity, is suitable in this optimization problem to search the optimal MC from the collection of possible cut-sets. However, a considerable portion of meaningless individuals would be produced at the stages of population initialization and genetic operation in the original algorithm, some supplementary modications must be employed to improve its eciency and eectiveness. For each survived island, resynchronization, one aspect of restoration, is a prior issue should be considered. A threat to jeopardize the resynchronization of the survived island is power system 1 transient instability. The mechanism of transient instability can be described as a part of generators in power system deviating from the remaining ones. The deviation of the group from the remaining groups causing power system instable is called critical pattern. The strategy of designing controllers to increase the coherency between the two groups of generators is promising to reduce, even eliminate in some case, the risk of the threat to power system transient stability. In order to implement the control strategy, Lyapunov trajectory tracking control is eective to calculate the mechanical torque to track power system's desired state.

Contributions to Secure Electric Power System Operation / Wu, Yingjun. - STAMPA. - (2013).

Contributions to Secure Electric Power System Operation

WU, YINGJUN
2013

Abstract

Electric power system is a fundamental infrastructure of modern society. A magnicent property of electric power system { security, is achieved by keeping it operated in a secure state at most of the time. Security means the ability to withstand imminent disturbances or contingencies, such as electric short circuits or unanticipated loss of system elements, without interruption of customer service. This thesis proposes methods to secure power system operation from classifying threat origins to power system security, analyzing power system steady-state security, splitting power system network intentionally to increase power system transient stability. Maintaining electric power system secure is a very challenging interdisciplinary multidimensional problem, which is impacted by a large amount of factors, such as extreme weather conditions and unexpected disturbances. In order to achieve keeping the system secure, pursuing a better understanding of all kinds of origins of threats to electric power system is meaningful. Identifying and classifying potential threats to electric power system help to design corresponding measures to tackle them. Moreover, due to impossibility of considering countless threats with nite resource, quantifying and ranking the risks of threats contribute to level up eciency and eectiveness. When power system in a normal, alert, or emergency state, steady-state security analysis, as a branch of power system security analysis, is an eective tool to provide information for operators to design control to mitigate power system progressing into a extremis state. Conventionally, most analysis methods for steady-state security are "point-wised", which means that they considering operational points by checking all components' electrical quantities. However, this sort of method has obvious disadvantages, such as heavy numerical computation and lacking global information. Therefore, "region-wised" method, such as nodal power injections security region and interface power ow security region, with the ability to provide global security information to operators, is promising. Normal, preventive and emergency control measures are eective tools to keep power system security. However, if these measures fail, power system will be placed into a extremis state. Extremely, a cascading spreading of system components outages would result in partial or systemwide blackout (loss of supplied load). In this case, intentional islanding, the ultimate control to preserve as many stable areas as possible, is an eective and promised measure to prevent blackout. In designing a islanding scheme, fast and eectively searching out the optimal MC (minimum cut-set) to split power system network is a conundrum. Moreover, for the large-scale power system, it is even impossible to nd out the best scheme but surrender to suboptimum ones. Genetic algorithm, with excellent optimization capacity, is suitable in this optimization problem to search the optimal MC from the collection of possible cut-sets. However, a considerable portion of meaningless individuals would be produced at the stages of population initialization and genetic operation in the original algorithm, some supplementary modications must be employed to improve its eciency and eectiveness. For each survived island, resynchronization, one aspect of restoration, is a prior issue should be considered. A threat to jeopardize the resynchronization of the survived island is power system 1 transient instability. The mechanism of transient instability can be described as a part of generators in power system deviating from the remaining ones. The deviation of the group from the remaining groups causing power system instable is called critical pattern. The strategy of designing controllers to increase the coherency between the two groups of generators is promising to reduce, even eliminate in some case, the risk of the threat to power system transient stability. In order to implement the control strategy, Lyapunov trajectory tracking control is eective to calculate the mechanical torque to track power system's desired state.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2507525
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