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Increasing distributed generation hosting capacity in distribution systems via optimal coordination of electric vehicle aggregators

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IET GENERATION TRANSMISSION & DISTRIBUTION 2021年第2期15卷 359-370页

作者： Quijano, Darwin A. Melgar-Dominguez, Ozy D. Sabillon, Carlos Venkatesh, Bala Padilha-Feltrin, Antonio Sao Paulo State Univ UNESP Elect Engn Dept BR-15385000 Ilha Solteira SP Brazil Ryerson Univ Ctr Urban Energy Toronto ON Canada

This work presents a novel strategy, designed from the distribution system operator viewpoint, aimed at estimating the hosting capacity in electric distribution systems when controllable plug-in electric vehicles are in place. The strategy seeks to determine the maximum wind-based distributed generation penetration by coordinating, on a forecast basis, the dispatch of electric vehicle aggregators, the operation of voltage regulation devices, and the active and reactive distributed generation power injections. Different from previous works, the proposed approach leverages controllable features of electric vehicles taking into account technical electric vehicle characteristics, driving behaviour of electric vehicle owners, and electric vehicle energy requirements to accomplish their primary purpose. The presented strategy is formulated as a two-stage stochastic mixed-integer linear programming problem. The first stage maximises the distributed generation installed capacity, while the second stage minimises the energy losses during the planning horizon. probability density functions are used to describe the uncertainties associated with renewable distributed generation, conventional demand, and electric vehicle driving patterns. Obtained results show that controlling the power dispatched to electric vehicle aggregators can increase the distributed generation hosting capacity by up to 15% (given a 40% electric vehicle penetration), when compared to an uncontrolled electric vehicle approach.

关键词： Optimisation techniques Voltage control Control of electric power systems probability and statistics Other topics in statistics Optimisation techniques Distributed power generation Power system planning and layout Distribution networks Transportation

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Fluctuations and the effective moduli of an isotropic, random aggregate of identical, frictionless spheres

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2005年第1期53卷 197-225页

作者： Jenkins, J Johnson, D La Ragione, L Makse, H Cornell Univ Dept Theoret & Appl Mech Ithaca NY 14853 USA Schlumberger Doll Res Ctr Ridgefield CT 06877 USA

We consider a random aggregate of identical frictionless elastic spheres that has first been subjected to an isotropic compression and then sheared. We assume that the average strain provides a good description of how stress is built up in the initial isotropic compression. However, when calculating the increment in the displacement between a typical pair of contaction particles due to the shearing, we employ force equilibrium for the particles of the pair, assuming that the average strain provides a good approximation for their interactions with their neighbors. The incorporation of these additional degrees of freedom in the displacement of a typical pair relaxes the system, leading to a decrease in the effective moduli of the aggregate. The introduction of simple models for the statistics of the ordinary and conditional averages contributes an additional decrease in moduli. The resulting value of the shear modulus is in far better agreement with that measured in numerical simulations. (C) 2004 Elsevier Ltd. All rights reserved.

关键词： vibrations granular materials rock stress waves probability and statistics

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STATISTICAL APPROACH TO THERMAL RATING OF OVERHEAD LINES FOR POWER TRANSMISSION AND DISTRIBUTION

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IEE PROCEEDINGS-C GENERATION TRANSMISSION AND DISTRIBUTION 1983年第5期130卷 245-256页

作者： PRICE, CF GIBBON, RR CENT ELECT GENERATING BOARD DIV TECHNOL PLANNING RESLEATHERHEAD KT22 7SESURREYENGLAND

The rating of an overhead line is limited by the maximum temperature it is permitted to reach. This temperature is chosen at the design stage along with the size of conductor, the height and spacing of the towers and overall optimisation of the design to meet the required balance between capital and revenue costs. Outside the control of the designer is the complex and variable cooling effect of the weather on the conductor. Fortunately the three basic parameters of wind, sun and air temperature do not each reach their extreme values for minimum cooling simultaneously. Hitherto, the degree of noncoincidence of these extreme values has been difficult to quantify owing to a lack of data on wind speeds below 1 m/s. Research work at CERL has provided comprehensive data on the incidence of low wind speeds, together with simultaneous values of wind direction, insolation and ambient air temperature. The temperature of a typical transmission conductor (400 mm2ACSR, Zebra) carrying full-load current was also recorded. The variations in this conductor temperature reflected the varying cooling effect of the weather parameters. The range over which the conductor temperature varied was divided into 5 deg C intervals, and the percentage of time that the conductor temperature was in each interval was calculated. The data was divided into three seasons for the purpose of the analysis. A relationship was then established between the time that the conductor exceeded any given design temperature and the ratio of the heat input under test to the heat loss that would occur under design conditions. This relationship was found to provide a correlation of the data for the three seasons, which was then used with existing heat transfer data to predict the rating of any conductor for any chosen design temperature and selected percentage of total time that the conductor may exceed that temperature. In practice, system design and security standards restrict actual continuous loadings, and lines

关键词： heat losses optimisation power transmission power overhead lines air temperature thermal rating power transmission and distribution wind Power transmission, distribution and supply overhead lines Overhead power lines probability and statistics cooling sun sunlight statistical analysis

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Micromechanical simulation of the failure of fiber reinforced composites

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2000年第3期48卷 621-648页

作者： Landis, CM Beyerlein, IJ McMeeking, RM Harvard Univ Div Engn & Appl Sci Cambridge MA 02138 USA Univ Calif Los Alamos Natl Lab Div Mat Sci & Technol Los Alamos NM 87545 USA Univ Calif Santa Barbara Dept Mech & Environm Engn Santa Barbara CA 93106 USA

The strength of unidirectionally reinforced fiber composites is simulated using the three dimensional shear lag model of Landis, C. M., McGlockton, M. A. and McMeeking, R. M. (1999) (An improved shear lag model for broken fibers in composites. J. Comp. Mat. 33, 667-680) and Weibull fiber statistics. The governing differential equations for the fiber displacements and stresses are solved exactly for any configuration of breaks using an influence superposition technique. The model predicts the tensile strength of well bonded, elastic fiber/matrix systems with fibers arranged in a square array. Length and strength scalings are used which are relevant for elastic, local load sharing composites. Several hundred Monte Carlo simulations were executed to determine the statistical strength distributions of the composite for three values of the fiber Weibull modulus, m = 5, 10 and 20. Stress-strain behavior and the evolution of fiber damage are studied. Bundle sizes of 10 x 10, 15 x 15, 20 x 20, 25 x 25, 30 x 30 and 35 x 35 fibers of various lengths are investigated to determine the dependence of strength on the composite size. The validity of weakest link statistics for composite strength is examined as well. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： fiber-reinforced composite material stress concentrations fracture mechanisms probability and statistics shear lag

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REPRESENTATION OF NON-GAUSSIAN probability-DISTRIBUTIONS IN STOCHASTIC LOAD-FLOW STUDIES BY THE METHOD OF GAUSSIAN SUM APPROXIMATIONS

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IEE PROCEEDINGS-C GENERATION TRANSMISSION AND DISTRIBUTION 1983年第4期130卷 165-171页

作者： SIRISENA, HR BROWN, EPM MINIST ENERGY NEW ZEALAND ELECTWELLINGTONNEW ZEALAND

The stochastic load flow (SLF) is extended to include non-Gaussian ‘long-term’ nodal probability-density-function (PDF) data by replacing each non-Gaussian PDF with a ‘Gaussian sum’ approximation. A series of SLFs (stochastic load flows) are then performed and the results recombined, with the correct weightings, to generate non-Gaussian PDF profiles for busbars and lines of interest. Generally less than half of the most likely convolution components need evaluating.P–ø,Q–Vdecomposition and nodal dependence is easily incorporated in the study and moment matching can be used to determine the ‘best’ lower order Gaussian sum approximation. Long-term network topological impedance changes can also be included in the proposed method.

关键词： load flow network topological impedance changes nonGaussian probability distributions Gaussian sum approximations probability and statistics probability stochastic systems Network and transmission line calculations stochastic load-flow studies

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A novel approach to touch voltage risk assessment for gas pipelines in shared transmission corridors

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IET SCIENCE MEASUREMENT & TECHNOLOGY 2023年第1期17卷 27-36页

作者： Chan, Keith Man-Kei Baguley, Craig Antony Madawala, Udaya K. Auckland Univ Technol Dept Elect & Elect Engn Auckland New Zealand Univ Auckland Dept Elect Comp & Software Engn Auckland New Zealand

Touch voltages are more likely to appear on long-distance pipelines that lie in shared corridors with transmission lines. The touch voltage level varies with soil resistivity and can become hazardous while maintenance is being undertaken, necessitating risk assessment. Therefore, a novel approach is proposed that achieves better accuracy in the risk assessment of hazardous touch voltages appearing on pipelines than current approaches. The proposed approach incorporates soil resistivity measurements taken over a 1-year period, allowing for the derivation of soil models, touch voltage hazard profiles versus time and, thus, a probability reduction factor that can be integrated into a probabilistic risk calculation. Using a probability reduction factor is a key aspect to improving the accuracy of risk assessment, allowing pipeline asset operators to clearly identify whether or not, risk mitigation action is required. Further, the proposed approach allows appropriate risk mitigation actions to be identified. The efficacy and significance of the proposed approach are demonstrated through a case study on an area of land near a shared gas pipeline and transmission line corridor. The case study results show how appropriate safety levels can be achieved by adjusting the number of work day per year and temporary protection settings.

关键词： soil resistivity measurements touch voltage hazard profiles Environmental issues transmission lines probability and statistics gas pipelines hazardous touch voltages probability reduction factor shared transmission corridors long-distance pipelines maintenance engineering touch voltage level soil hazardous materials statistics Mechanical components risk mitigation action risk management probability Measurement power transmission lines Health and safety aspects Power transmission lines and cables Maintenance and reliability pipelines probabilistic risk calculation voltage risk assessment

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The influence of particle fluctuations on the average rotation in an idealized granular material

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2009年第9期57卷 1449-1458页

作者： La Ragione, Luigi Jenkins, James T. Politecn Bari Dipartimento Ingn Civile & Ambientale I-70125 Bari Italy Cornell Univ Dept Theoret & Appl Mech Ithaca NY 14853 USA

Granular materials are a simple example of a Cosserat continuum in that the average particle rotations may differ from the rotation of the average deformation. In the absence of couple stress, this difference insures that the stress is symmetric. This has been shown in theories that assume that the displacement at particle contacts is given by the average deformation and spin. Here, we indicate how the difference between the average rotation of the particles and the average rotation of the deformation can be determined when fluctuations in particle displacements and rotations satisfy local force and moment equilibria in a random aggregate of identical spheres. The predictions based on this model are in better agreement with numerical simulation than that given by the simple average strain theory. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Effective moduli Granular material Cosserat material probability and statistics Numerical simulation

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A variance analysis of the Metropolis Light Transport algorithm

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COMPUTERS & GRAPHICS-UK 2001年第2期25卷 287-294页

作者： Ashikhmin, M Premoze, S Shirley, P Smits, B Univ Utah Dept Comp Sci Salt Lake City UT 84112 USA

The Metropolis Light Transport algorithm is a variant of the classic Metropolis method used in statistical physics, A variance analysis of the Metropolis Light Transport algorithm is presented that bounds its Variance in terms of the number of paths used and the intrinsic correlation between samples. It is shown that the variance of a pixel is Theta (1/N)1 where N is the number of samples for the entire image. The analysis uses basic probability, Bayes' law, and the principle of stationary distributions. This result implies that the presence of correlation in the algorithm does not make its asymptotic time complexity worse than uncorrelated Monte Carlo methods such as path tracing. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： three-dimensional graphics and realism, raytracing simulation and modeling, Monte Carlo analysis of algorithms and problem complexity, numerical algorithms and problems probability and statistics

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Hyper-QC: An accelerated finite-temperature quasicontinuum method using hyperdynamics

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2014年第1期63卷 94-112页

作者： Kim, W. K. Luskin, M. Perez, D. Voter, A. F. Tadmor, E. B. Univ Minnesota Dept Aerosp Engn & Mech Minneapolis MN 55455 USA Univ Minnesota Sch Math Minneapolis MN 55455 USA Los Alamos Natl Lab Theoret Div T1 Los Alamos NM USA

The quasicontinuum (QC) method is a spatial multiscale method that extends the length scales accessible to fully atomistic simulations (like molecular dynamics (MD)) by several orders of magnitude. While the recent development of the so-called "hot-QC method" enables dynamic simulations at finite temperature, the times accessible to these simulations remain limited to the sub-microsecond time scale due to the small time step required for stability of the numerical integration. To address this limitation, we develop a novel finite-temperature QC method that can treat much longer time scales by coupling the hot-QC method with hyperdynamics a method for accelerating time in MD simulations. We refer to the new approach as "hyper-QC". As in the original hyperdynamics method, hyper-QC is targeted at dynamical systems that exhibit a separation of time scales between short atomic vibration periods and long waiting times in metastable states. Acceleration is achieved by modifying the hot-QC potential energy to reduce the energy barriers between metastable states in a manner that ensures that the characteristic dynamics of the system are preserved. First, the high accuracy of hot-QC in reproducing rare event kinetics is demonstrated. Then, the hyper-QC methodology is validated by comparing hyper-QC results with those of hot-QC and full MD for a one-dimensional chain of atoms interacting via a Lennard-Jones potential. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Fracture Constitutive behavior Finite elements probability and statistics Multiscale methods

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Dynamic fragmentation of brittle solids: a multi-scale model

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EUROPEAN JOURNAL OF MECHANICS A-SOLIDS 2002年第1期21卷 105-120页

作者： Denoual, C Hild, F Univ Paris 06 CNRS LMT Cachan ENS Cachan F-94235 Cachan France CTA Dept Mat Surfaces Protec DGA F-94114 Arcueil France

Modeling dynamic fragmentation of brittle materials usually implies to choose between a discrete description of the number of fragments and a continuum approach with damage variables. A damage model that can be used in the whole range of loadings (from quasi-static to dynamic ones) is developed. The deterministic or probabilistic nature of fragmentation is discussed. Qualitative and quantitative validations are given by using a real-time visualization configuration for analyzing the degradation kinetics during impact and a moire technique to measure the strains in a ceramic tile during impact. Finally, a closed-form solution of the change of the number of broken defects with the applied stress gives a way of optimizing the microstructure of ceramics for armor applications. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

关键词： ceramic materials probability and statistics impact testing

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