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

A positioning algorithm for SPH ghost particles in smoothly curved geometries

An algorithm to place ghost particles across the domain boundary in the context of Smoothed Particle Hydrodynamics (SPH) is derived from basic principles, and constructed for several simple, three-dimensional, geometries. The performance of the algorithm is compared against the more commonly used ‘‘mirrored with respect to the local tangent plane" approach and shown to converge to it whenever the distance of the particles to the reflecting boundary is much smaller than a local measure of the surface’s curvature. The algorithm is demonstrated, tested and compared against the usual approach via simulations of a compressible flow around a cylinder, and the numerical cost of implementing it is addressed. We conclude that use of ghost particles to enforce boundary conditions is not only viable in the presence of smoothly curved boundaries, but more robust than the usual method for low-resolution scenarios.This research was sponsored in part by the DGICYT (Dirección General de Investigaciones Científicas y Tecnológicas) of Spain under National Project No. ENE2015-68265. Research was also funded in part by the Erasmus Mundus Program: International Doctoral College in Fusion Science and Engineering FUSION-DC, Spain

Fourier signature of filamentary vorticity structures in two-dimensional turbulence

It is shown that coherent regions of isotropic two-dimensional (2D) turbulence can be clearly identified in the phase part of the Fourier spectrum. Certain spectral phase events are particularly prominent, and are much stronger in the range of wave numbers corresponding to the dissipation range. It is shown that these events are associated with spatially localized filamentary structures in the 2D vorticity field that historically have been related to the intermittency of dissipation. The identified phase signature provides a particularly transparent diagnostic of the temporal evolution of the coherent coupling of disparate scales in anisostropic intermittent dissipative events. These results open the possibility of using the phase of the Fourier transform as a new turbulence diagnostic that identifies and quantitatively characterizes details pertaining to dissipative events.Research supported in part by the Spanish national projects No. ENE2009-12213-C03-03, ENE2012-33219, UNC313-4E-2361 and ENE2012-31753 and the US DOE Office of Science Grants No. DE-FG02-04ER54741 and DE-FG02-89ER53291. Simulations run at the Uranus supercomputer cluster at Universidad Carlos III de Madrid

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

Analysis of the blackout risk reduction when segmenting large power systems using lines with controllable power flow

Large electrical transmission networks are susceptible to undergo very large blackouts due to cascading failures, with a very large associated economical cost. In this work we propose segmenting large power grids using controllable lines, such as high-voltage direct-current lines, to reduce the risk of blackouts. The method consists in modifying the power flowing through the lines interconnecting different zones during cascading failures in order to minimize the load shed. As a result, the segmented grids have a substantially lower risk of blackouts than the original network, with reductions up to 60% in some cases. The control method is shown to be specially efficient in reducing blackouts affecting more than one zone.DG and PC acknowledge funding from project PACSS RTI2018-093732-B-C22 and APASOS PID2021-122256NB-C22 of the MCIN/AEI/10.13039/501100011033/ and by EU through FEDER funds (A way to make Europe), from the Maria de Maeztu program MDM-2017-0711 of the MCIN/AEI/10.13039/501100011033/, and also from the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 957852, VPP4Islands). B.A.C. and J.M.R.-B. acknowledge access to Uranus, a supercomputer cluster located at Universidad Carlos III de Madrid (Spain) funded jointly by EU FEDER funds and by the Spanish Government via the National Research Project Nos. UNC313-4E-2361, ENE2009-12213-C03-03, ENE2012-33219, and ENE2012-31753. OGB was supported in part by FEDER/Ministerio de Ciencia, Innovacion y Universidades - Agencia Estatal de Investigación, Project RTI2018-095429-B-I00 and in part by FI-AGAUR Research Fellowship Program, Generalitat de Catalunya. The work of OGB is supported by the ICREA Academia program

Magneto-hydrodynamical nonlinear simulations of magnetically confined plasmas using smooth particle hydrodynamics (SPH)

The successful application of techniques inspired in Smoothed Particle Hydrodynamics (SPH) to magnetohydrodynamical (MHD) nonlinear simulations of magnetically confined plasmas requires the previous solution to a number of challenging issues that are still not fully resolved, namely, the construction of precise, arbitrary initial conditions in complicated geometries, the formulation of adequate boundary conditions for the magnetic field, and the correct treatment of three-dimensional toroidal boundaries of the arbitrary shape. In this paper, we present an SPH implementation of the nonlinear MHD equations that include our proposed solution to these issues and test its performance on a broad selection of nonlinear MHD problems: (1) the propagation of circularly polarized Alfven waves, (2) the occurrence of magnetic reconnection for a Harris current-sheet, and (3) the nonlinear MHD stability properties of various cylindrical pinches.This research was sponsored by DGICYT (Dirección General de Investigación Científica y Técnica) under Project No. ENE2015-68265, MINECO (Ministerio de Economía y Competitividad) under Project No. UNC313-4E-2361, and the Erasmus Mundus Program: International Doctoral College in Fusion Science and Engineering FUSION-DC

A novel efficient solver for Ampere's equation in general toroidal topologies based on singular value decomposition techniques

A new method is proposed to solve Ampere's equation in an arbitrary toroidal domain in which all currents are known, given proper boundary conditions for the magnetic vector potential. The novelty of the approach lies in the application of singular value decomposition (SVD) techniques to tackle the difficulties caused by the kernel associated by the curl operator. This kernel originates physically due to the magnetic field gauge. To increase the efficiency of the solver, the problem is represented by means of a dual finite difference-spectral scheme in arbitrary generalized toroidal coordinates, which permits to take advantage of the block structure exhibited by the matrices that describe the discretized problem. The result is a fast and efficient solver, up to three times faster than the double-curl method in some cases, that provides an accurate solution of the differential form of Ampere law while guaranteeing a zero divergence of the resulting magnetic field down to machine precision.This research has been sponsored in part by the Ministerio de Economía y Competitividad (MINECO) of Spain under Project No. ENE2015-68265-P. Use have also been made of Uranus, a supercomputer cluster located at Universidad Carlos III de Madrid (Spain) funded jointly by EU FEDER Project No. UNC313-4E-2361, by the Ministerio de Economía, Industria y Competitividad (MICINN) via the National Research Project No. ENE2009-12213-C03-03 and by the Ministerio de Economía y Competitividad (MINECO) via the National Research Project Nos. ENE2012-33219 and ENE2012-31753

The potential impact of climate change on the efficiency and reliability of solar, hydro, and wind energy sources

Climate change impacts the electric power system by affecting both the load and generation. It is paramount to understand this impact in the context of renewable energy as their market share has increased and will continue to grow. This study investigates the impact of climate change on the supply of renewable energy through applying novel metrics of intermittency, power production and storage required by the renewable energy plants as a function of historical climate data variability. Here we focus on and compare two disparate locations, Palma de Mallorca in the Balearic Islands and Cordova, Alaska. The main results of this analysis of wind, solar radiation and precipitation over the 1950–2020 period show that climate change impacts both the total supply available and its variability. Importantly, this impact is found to vary significantly with location. This analysis demonstrates the feasibility of a process to evaluate the local optimal mix of renewables, 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.P.C. and D.G. acknowledge financial support from Ministerio de Ciencia e Innovación (Spain), the Agencia Estatal de Investigación (AEI, Spain), and the Fondo Europeo de Desarrollo Regional (FEDER, EU) under grant PACSS (RTI2018-093732-B-C22) and the Maria de Maeztu program for Units of Excellence in R&D (MDM-2017-0711). D.N. gratefully acknowledges support from DOE Project GMLC 1.5.02—Resilient Alaskan Distribution system Improvements using Automation, Network analysis, Control, and Energy storage (RADIANCE). U.S.B. acknowledges support from the National Science Foundation under award #OIA-1753748 and by the State of Alaska for material which this work is based upon

Bootstrap current control studies in the Wendelstein 7-X stellarator using the free-plasma-boundary version of the SIESTA MHD equilibrium code

The recently developed free-plasma-boundary version of the SIESTA MHD equilibrium code (Hirshman et al 2011 Phys. Plasmas 18 062504; Peraza-Rodriguez et al 2017 Phys. Plasmas 24 082516) is used for the first time to study scenarios with considerable bootstrap currents for the Wendelstein 7-X (W7-X) stellarator. Bootstrap currents in the range of tens of kAs can lead to the formation of unwanted magnetic island chains or stochastic regions within the plasma and alter the boundary rotational transform due to the small shear in W7-X. The latter issue is of relevance since the island divertor operation of W7-X relies on a proper positioning of magnetic island chains at the plasma edge to control the particle and energy exhaust towards the divertor plates. Two scenarios are examined with the new free-plasma-boundary capabilities of SIESTA: a freely evolving bootstrap current one that illustrates the difficulties arising from the dislocation of the boundary islands, and a second one in which off-axis electron cyclotron current drive (ECCD) is applied to compensate the effects of the bootstrap current and keep the island divertor configuration intact. SIESTA finds that off-axis ECCD is indeed able to keep the location and phase of the edge magnetic island chain unchanged, but it may also lead to an undesired stochastization of parts of the confined plasma if the EC deposition radial profile becomes too narrow.Research was funded in part by the Spanish National Project No. ENE2015-68265. Research carried in part at the Max-PlanckInstitute for Plasma Physics in Greifswald (Germany), whose hospitality is gratefully acknowledged. SIESTA free-boundary runs have been carried out in Uranus, a supercomputer cluster located at Universidad Carlos III de Madrid and funded jointly by EU-FEDER funds and by the Spanish Government via the National Projects No. UNC313-4E-2361, No. ENE2009-12213- C03-03, No. ENE2012-33219, and No. ENE2012-31753

Extension of the SIESTA MHD equilibrium code to free-plasma-boundary problems

is a recently developed MHD equilibrium code designed to perform fast and accurate calculations of ideal MHD equilibria for three-dimensional magnetic configurations. Since SIESTA does not assume closed magnetic surfaces, the solution can exhibit magnetic islands and stochastic regions. In its original implementation SIESTA addressed only fixed-boundary problems. That is, the shape of the plasma edge, assumed to be a magnetic surface, was kept fixed as the solution iteratively converges to equilibrium. This condition somewhat restricts the possible applications of SIESTA. In this paper, we discuss an extension that will enable SIESTA to address free-plasma-boundary problems, opening up the possibility of investigating problems in which the plasma boundary is perturbed either externally or internally. As an illustration, SIESTA is applied to a configuration of the W7-X stellarator.This research was funded in part by the Ministerio de Economía, Industria y Competitividad of Spain, Grant No. ENE2015-68265. This research was carried out in part at the Max-Planck-Institute for Plasma Physics in Greifswald (Germany), whose hospitality is gratefully acknowledged. This research was supported in part by the U.S. Department of Energy, Office of Fusion Energy Sciences under Award DE-AC05-00OR22725. SIESTA runs have been carred out in Uranus, a supercomputer cluster located at Universidad Carlos III de Madrid and funded jointly by the European Regional Development Funds (EU-FEDER) Project No. UNC313-4E-2361, and by the Ministerio de Economía, Industria y Competitividad via the National Project Nos. ENE2009-12213-C03-03, ENE2012-33219, and ENE2012-31753