Resilient Networks

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Now showing 1 - 9 of 9
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    Building Synthetic Power Transmission Networks of Many Voltage Levels, Spanning Multiple Areas
    ( 2018-01-03) Birchfield, Adam B. ; Xu, Ti ; Shetye, Komal ; Overbye, Thomas
    Synthetic power grids, that is, test cases designed to match realistic structural and statistical characteristics of actual grids, are useful for research, development, and demonstration of innovations, since the cases are fictitious and thus free from data confidentiality issues. Building on previous work, this paper addresses a couple of related problems in the transmission network synthesis process. These issues appear as created cases become larger and involve multiple areas and overlapping nominal voltage levels. A fast, scalable hierarchical clustering is designed to assign voltage levels to substations considering the needs of the system, the specific constraints of the area, and smooth interconnections between neighboring areas with different voltage levels. A line topology generation framework is considered that is appropriate for many networks of different voltage levels, constructed together for a useful, realistic grid. These methods are demonstrated in a new 2000 bus test case, validated and publicly released.
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    Interdependence of Transmission Branch Parameters on the Voltage Levels
    ( 2018-01-03) Athari, Mir Hadi ; Wang, Zhifang
    Transformers and transmission lines are critical components of a grid network. This paper analyzes the statistical properties of the electrical parameters of transmission branches and especially examines their interdependence on the voltage levels. Some interesting findings include: (a) with appropriate conversion of MVA rating, a transformer’s per unit reactance exhibits consistent statistical pattern independent of voltage levels and capacity; (b) the distributed reactance (ohms/km) of transmission lines also has some consistent patterns regardless of voltage levels; (c) other parameters such as the branch resistance, the MVA ratings, the transmission line length, etc, manifest strong interdependence on the voltage levels which can be approximated by a power function with different power constants. The results will be useful in both creation of synthetic power grid test cases and validation of existing grid models.
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    Assignment of Electrical Properties to Power Grid Topologies
    ( 2018-01-03) Schweitzer, Eran ; Scaglione, Anna ; Hedman, Kory
    Power systems are often described in terms of graphs, with various properties like load and impedance associated with the nodes and edges. These properties are coupled to the graph's topology, reflecting the great deal of engineering design in the power system. With the goal of automating the creation of usable synthetic cases, the problem of assigning these properties is considered. It is formulated as a Mixed Integer Program (MIP), which aims to minimize the angle differences between adjacent nodes in the system. Since the problem quickly balloons in size, a decomposition into smaller zones is explored, that enables scaling the problem to larger system sizes. Experiments demonstrate the efficacy and viability of the approach.
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    Systematic Framework for Integration of Weather Data into Prediction Models for the Electric Grid Outage and Asset Management Applications
    ( 2018-01-03) Kezunovic, Mladen ; Obradovic, Zoran ; Djokic, Tatjana ; Roychoudhury, Shoumik
    This paper describes a Weather Impact Model (WIM) capable of serving a variety of predictive applications ranging from real-time operation and day-ahead operation planning, to asset and outage management. The proposed model is capable of combining various weather parameters into different weather impact features of interest to a specific application. This work focuses on the development of a universal weather impacts model based on the logistic regression embedded in a Geographic Information System (GIS). It is capable of merging massive data sets from historical outage and weather data, to real-time weather forecast and network monitoring measurements, into a feature known as weather hazard probability. The examples of the outage and asset management applications are used to illustrate the model capabilities.
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    Exploring cascading outages and weather via processing historic data
    ( 2018-01-03) Dobson, Ian ; Carrington, Nichelle'Le ; Zhou, Kai ; Wang, Zhaoyu ; Carreras, Benjamin ; Reynolds-Barredo, Jose
    We describe some bulk statistics of historical initial line outages and the implications for forming contingency lists and understanding which initial outages are likely to lead to further cascading. We use historical outage data to estimate the effect of weather on cascading via cause codes and via NOAA storm data. Bad weather significantly increases outage rates and interacts with cascading effects, and should be accounted for in cascading models and simulations. We suggest how weather effects can be incorporated into the OPA cascading simulation and validated. There are very good prospects for improving data processing and models for the bulk statistics of historical outage data so that cascading can be better understood and quantified.
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    A Submodular Approach for Electricity Distribution Network Reconfiguration
    ( 2018-01-03) Khodabakhsh, Ali ; Yang, Ger ; Basu, Soumya ; Nikolova, Evdokia ; Caramanis, Michael ; Lianeas, Thanasis ; Pountourakis, Emmanouil
    Distribution network reconfiguration (DNR) is a tool used by operators to balance line load flows and mitigate losses. As distributed generation and flexible load adoption increases, the impact of DNR on the security, efficiency, and reliability of the grid will increase as well. Today, heuristic-based actions like branch exchange are routinely taken, with no theoretical guarantee of their optimality. This paper considers loss minimization via DNR, which changes the on/off status of switches in the network. The goal is to ensure a radial final configuration (called a spanning tree in the algorithms literature) that spans all network buses and connects them to the substation (called the root of the tree) through a single path. We prove that the associated combinatorial optimization problem is strongly NP-hard and thus likely cannot be solved efficiently. We formulate the loss minimization problem as a supermodular function minimization under a single matroid basis constraint, and use existing algorithms to propose a polynomial time local search algorithm for the DNR problem at hand and derive performance bounds. We show that our algorithm is equivalent to the extensively used branch exchange algorithm, for which, to the best of our knowledge, we pioneer in proposing a theoretical performance bound. Finally, we use a 33-bus network to compare our algorithm's performance to several algorithms published in the literature.
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    Location-Dependent Impacts of Resource Inertia on Power System Oscillations
    ( 2018-01-03) Xu, Ti ; Jang, Wonhyeok ; Overbye, Thomas J.
    Inertial responses are seen by the system as the injection or withdrawal of electrical energy, corresponding to a change of frequency. The inertia of a machine primarily contributes to the power system transient stability. Oscillations are always present in the bulk power system due to the electromechanical nature of the grid. Poorly damped oscillations may cause system instability. Thus, this paper aims to study inertia's impacts on system primary frequency response, in particular on system oscillation modes. Both transient stability simulations and modal analysis are performed to provide insights into the extent to which inertia and its location influence the system oscillation behavior. Simulation results using both a small-scale test system and a large-scale synthetic network dynamic model are presented to verify the locational impacts of resource inertia.
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    Autonomous Energy Grids
    ( 2018-01-03) Kroposki, Benjamin ; Dall'Anese, Emiliano ; Bernstein, Andrey ; Zhang, Yingchen ; Hodge, Bri-Mathias
    Current frameworks to monitor, control, and optimize large-scale energy systems are becoming increasingly inadequate because of significantly high penetration levels of variable generation and distributed energy resources being integrated into electric power systems; the deluge of data from pervasive metering of energy grids; and a variety of new market mechanisms, including multilevel ancillary services. This paper outlines the concept of autonomous energy grids (AEGs). These systems are supported by a scalable, reconfigurable, and self-organizing information and control infrastructure, are extremely secure and resilient (self-healing), and can self-optimize in real time to ensure economic and reliable performance while systematically integrating energy in all forms. AEGs rely on cellular building blocks that can self-optimize when isolated from a larger grid and participate in optimal operation when interconnected to a larger grid. This paper describes the key concepts and research necessary in the broad domains of optimization theory, control theory, big data analytics, and complex system theory and modeling to realize the AEG vision.