Effects of Self-Consistent Flow on Island Generation in Interchange Mode

The time evolution of magnetic island in the nonlinear phase of the resistive interchange mode is examined in the cylindrical geometry. The effects of self-consistent uniform poloidal flow is taken into account. In this case, the reconnection of the magnetic field line occurs both at the saturation of the dominant unstable mode and at the saturation of the n = 0 mode, where n is the toroidal mode number, through the curvature change of perturbed poloidal flux surface

Topological structures of the resistive pressure gradient turbulence with averaged poloidal flow

When a significant averaged poloidal flow is generated by the resistive pressure-gradient-driven turbulence the topological properties of the flow structures can change in some radial regions where the shear flow is large. We have applied the topological analysis approach that we have developed (2013 J. Phys. A: Math. Theor. 46 375501) to this situation and found that in addition to the filamentary vortex structures there are deformed toroidal structures that seem to act as transport barriers. Analysis of all these structures is presented here.This research was sponsored by DGICYT (Dirección General de Investigación Científica y Técnica) of Spain under Project No. ENE2012-38620-C02-02. One of us (B.A.C) also gratefully acknowledges the support from a 'Cátedra de Excelencia' from Universidad Carlos III and Banco de Santander

Optimized implementation of power dispatch in the OPA model and its implications for dispatch sensitivity for the WECC power network

The social and economic costs of large blackouts in power transmission networks make it critical to properly understand their dynamics. The OPA model was developed with this objective in mind and has previously been applied to power grids of small and medium size, some of them properly modeling realistic cases such as the simplified WECC network, covering the Western region of the US. The bulk of the OPA model's computational cost comes from the repeated solution of a linear programming problem using the Simplex method which is difficult to parallelize. In this paper we introduce important improvements to the modeling part of the linear problem, accelerating the previous implementation by a factor of up to 200, depending on the network. These improvements make it possible, from a practical point of view, to simulate the largest, most detailed, WECC network consisting of 19,402 nodes, reducing the wall-clock time of the simulation from two years to only 10 days. The first simulations show an interesting result: the detailed 19,402 nodes network displays a reduced sensitivity of the dynamics to the dispatch, when compared to the previously used simplified WECC models containing only 1553 and 2504 nodes.This research was sponsored by Ministerio de Economía y Competitividad of Spain under Projects No. ENE2012-31753, ENE2012- 33219, ENE2015-68265-P and ENE2015-68265-P. Simulations have been run in the supercomputer cluster Uranus located at Universidad Carlos III de Madrid (Spain), funded by the Spanish Government via the national projects UNC313-4E-2361, ENE2012-33219 and ENE2012- 31753

The Impact of Incorporating Wind Energy in the Electric Grid

In this paper we investigate the impact of increasing the penetration of wind generation with real variability on the risk to, and robustness of, the power transmission grid using a dynamic model of the power transmission system (OPA). There are three timescales of variability discussed but this paper will focus on the impact of two. It is found that with different fractions and distributions of wind generation and central generation, varied dynamics and risk are possible. One important parameter is the fraction of the total power demand supplied by the wind generation. It is found that the risk has a minimum in fraction of wind power supplied, after which the risk increased as the wind power penetration increases. In the same networks, decreasing the number of central generators without decreasing their power supplied in general increases the risk after a critical minimum number of generators is reached

Validating the OPA Cascading Blackout Model on a 19402 Bus Transmission Network with Both Mesh and Tree Structures

The OPA model calculates the long-term risk of cascading blackouts by simulating cascading outages and the slow process of network upgrade in response to blackouts. We validate OPA on a detailed 19402 bus network model of the Western Electricity Coordinating Council (WECC) interconnection with publicly available data. To do this, we examine scalings on a series of WECC interconnection models with increasing detail. The most detailed, 19402 bus network has more tree structures at the edges of the main mesh structure, and we extend the OPA model to account for this. The higher-risk cascading outages are the large cascades that extend across interconnections, so validating cascading models on large networks is crucial to understanding how the real grid behaves. Finally, exploring networks with mixed mesh and tree like structure has implications for the risk analysis for both the transmission grid and other network infrastructures

The interplay of network structure and dispatch solutions in power grid cascading failures

For a given minimum cost of the electricity dispatch, multiple equivalent dispatch solutions may exist. We explore the sensitivity of networks to these dispatch solutions and their impact on the vulnerability of the network to cascading failure blackouts. It is shown that, depending on the heterogeneity of the network structure, the blackout statistics can be sensitive to the dispatch solution chosen, with the clustering coefficient of the network being a key ingredient. We also investigate mechanisms or configurations that decrease discrepancies that can occur between the different dispatch solutions

The Radial Propagation of Heat in Strongly Driven Non-Equilibrium Fusion Plasmas

Heat transport is studied in strongly heated fusion plasmas, far from thermodynamic equilibrium. The radial propagation of perturbations is studied using a technique based on the transfer entropy. Three different magnetic confinement devices are studied, and similar results are obtained. "Minor transport barriers" are detected that tend to form near rational magnetic surfaces, thought to be associated with zonal flows. Occasionally, heat transport "jumps" over these barriers, and this "jumping" behavior seems to increase in intensity when the heating power is raised, suggesting an explanation for the ubiquitous phenomenon of "power degradation" observed in magnetically confined plasmas. Reinterpreting the analysis results in terms of a continuous time random walk, "fast" and "slow" transport channels can be discerned. The cited results can partially be understood in the framework of a resistive Magneto-HydroDynamic model. The picture that emerges shows that plasma self-organization and competing transport mechanisms are essential ingredients for a fuller understanding of heat transport in fusion plasmas.Research sponsored in part by the Ministerio de Economía y Competitividad of Spain under Project No. ENE2015-68206-P and ENE2015-68265-P. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2014-2018 and 2019-2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission

Obtaining statistics of cascading line outages spreading in an electric transmission network from standard utility data

We show how to use standard transmission line outage historical data to obtain the network topology in such a way that cascades of line outages can be easily located on the network. Then we obtain statistics quantifying how cascading outages typically spread on the network. Processing real outage data is fundamental for understanding cascading and for evaluating the validity of the many different models and simulations that have been proposed for cascading in power networks.This work was supported in part by NSF grant CPS-1135825. Paper no. TPWRS-01019-2015. We gratefully thank Bonneville Power Administration for making publicly available the outage data that made this paper possible. The analysis and any conclusions are strictly those of the authors and not of Bonneville Power Administratio

A First Analysis of the Potential Impact of Climate Change on the Efficiency and Reliability of Solar and Hydro Energy Sources

Climate change impacts our electric power system in several ways, affecting both the load and generation. Here we investigate one part of these impacts, the effect of climate change on the supply of renewable energy. Analyzing 60 years of data, climate change is found to impact both the total supply available and its variability. This impact is found to vary significantly with location. Here we focus on and compare two disparate locations, Palma de Mallorca in the Balearic Islands and Cordova, Alaska. Using novel metrics, this analysis demonstrates the feasibility of a process to evaluate the changing needs for energy storage as well as the ability to evaluate the impact on grid reliability regarding both penetration of the increasing renewable resources and changes in the variability of the resource. This framework can be used to quantify the impact on both transmission grids and microgrids and can guide possible mitigation paths