Topological analysis of the power grid and mitigation strategies against cascading failures

This paper presents a complex systems overview of a power grid network. In recent years, concerns about the robustness of the power grid have grown because of several cascading outages in different parts of the world. In this paper, cascading effect has been simulated on three different networks, the IEEE 300 bus test system, the IEEE 118 bus test system, and the WSCC 179 bus equivalent model, using the DC Power Flow Model. Power Degradation has been discussed as a measure to estimate the damage to the network, in terms of load loss and node loss. A network generator has been developed to generate graphs with characteristics similar to the IEEE standard networks and the generated graphs are then compared with the standard networks to show the effect of topology in determining the robustness of a power grid. Three mitigation strategies, Homogeneous Load Reduction, Targeted Range-Based Load Reduction, and Use of Distributed Renewable Sources in combination with Islanding, have been suggested. The Homogeneous Load Reduction is the simplest to implement but the Targeted Range-Based Load Reduction is the most effective strategy.Comment: 5 pages, 8 figures, 1 table. This is a limited version of the work due to space limitations of the conference paper. A detailed version is submitted to the IEEE Systems Journal and is currently under revie

Topological analysis and mitigation strategies for cascading failures in power grid networks

Master of ScienceDepartment of Electrical and Computer EngineeringCaterina M. ScoglioIn recent times, research in the field of complex networks has advanced by leaps and bounds. Researchers have developed mathematical models for different networks such as epidemic networks, computer networks, power grid networks, and so on. In this thesis, the power grid has been modeled as a complex network. The power grid is being used extensively in every field today. Our dependence on the power grid has exceeded to an extent that we cannot think of survival without electricity. Recently, there has been an increasing concern about the growing possibility of cascading failures, due to the fact that the power grid is works close to full utilization. Furthermore, the problem will be exacerbated by the need to transfer a large amount of power generated by renewable sources from the regions where it is produced to the regions where it is consumed. Many researchers have studied these networks to find a solution to the problem of network robustness. Topological analysis may be considered as one of the components of analysis of a system's robustness. In the first part of this thesis, to study the cascading effect on power grid networks from a topological standpoint, we developed a simulator and used the IEEE standard networks for our analysis. The cascading effect was simulated on three standard networks, the IEEE 300 bus system, the IEEE 118 bus test system, and the WSCC 179 bus equivalent model. To extend our analysis to a larger set of networks with different topologies, we developed a first approximation network generator the creates networks with characteristics similar to the standard networks but with different topologies. The generated networks were then compared with the standard networks to show the effect of topology on the robustness of power grid networks. A comparison of the network metrics for the standard and the generated networks indicate that the generated networks are more robust than the standard ones. However, even if the generated topologies show an increased robustness with respect to the standard topologies, the real implementation and design of power grids based on those topologies requires further study, and will be considered as future work. In the second part of this thesis, we studied two mitigation strategies based on load reduction, Homogeneous load reduction and Targeted range-based load reduction. While the generic Homogeneous strategy will only mitigate the severity of the cascade when a non-negligible load reduction is performed, our newly proposed targeted load reduction strategy is much more efficient, reducing the load only in a small portion of the grid. The determination of this special portion of the grid is based on an algorithm, which finds the paths supplying power from the generators to the nodes. This algorithm is described in details in the Appendix B. While the Homogeneous strategy is easier to implement, efficient results can be obtained using the targeted strategy

Dynamics on complex networks with application to power grids

Doctor of PhilosophyDepartment of Electrical and Computer EngineeringCaterina ScoglioThe science of complex networks has significantly advanced in the last decade and has provided valuable insights into the properties of real world systems by evaluating their structure and construction. Several phenomena occurring in real technological and social systems can be studied, evaluated, quantified, and remedied with the help of network science. The electric power grid is one such real technological system that can be studied through the science of complex networks. The electric grid consists of three basic sub-systems: Generation, Transmission, and Distribution. The transmission sub-system is of particular interest in this work because its mesh-like structure offers challenging problems to complex networks researchers. Cascading dynamics of power grids is one of the problems that can be studied through complex networks. The North American Electric Reliability Corporation (NERC) defines a cascading failure as the uncontrolled successive loss of system elements triggered by an incident at any location. In this dissertation, we primarily discuss the dynamics of cascading failures in the power transmission grid, from a complex networks perspective, and propose possible solutions for mitigating their effects. We evaluate the grid dynamics for two specific scenarios, load growth and random fluctuations in the grid, to study the behavior of the grid under critical conditions. Further, we propose three mitigation strategies for reducing the damage caused by cascading failures. The first strategy is intentional islanding in the power transmission grid. The aim of this method is to intentionally split the grid into two or more separate self- sustaining components such that the initial failure is isolated and the separated components can function independently, with minimum load shedding. The second mitigation strategy involves controlled placement of distributed generation (DG) in the transmission system in order to enhance robustness of the grid. The third strategy requires the addition of a link in the transmission grid by reduction of the average spectral distance, utilizing the Ybus matrix of the grid and a novel algorithm. Through this dissertation, we aim to successfully cover the gap present in the complex networks domain, with respect to the vulnerability analysis of power grid networks

Abruptness of cascade failures in power grids

Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into “super-grids”

Power grids, smart grids and complex networks

We present some possible Complex Networks approaches to study and understand Power Grids and to improve them into Smart Grids . We first sketch the general properties of the Electric System with an attention to the effects of Distributed Generation. We then analyse the effects of renewable power sources on Voltage Controllability. Afterwords, we study the impact of electric line overloads on the nature of Blackouts. Finally, we discuss the possibility of implementing Self Healing capabilities into Power Grids through the use of Routing Protocols