New Boundary Constraints for Elliptic Systems used in Grid Generation Problems
Kaul, Upender K.; Clancy, Daniel (Technical Monitor)
2002-01-01
This paper discusses new boundary constraints for elliptic partial differential equations as used in grid generation problems in generalized curvilinear coordinate systems. These constraints, based on the principle of local conservation of thermal energy in the vicinity of the boundaries, are derived using the Green's Theorem. They uniquely determine the so called decay parameters in the source terms of these elliptic systems. These constraints' are designed for boundary clustered grids where large gradients in physical quantities need to be resolved adequately. It is observed that the present formulation also works satisfactorily for mild clustering. Therefore, a closure for the decay parameter specification for elliptic grid generation problems has been provided resulting in a fully automated elliptic grid generation technique. Thus, there is no need for a parametric study of these decay parameters since the new constraints fix them uniquely. It is also shown that for Neumann type boundary conditions, these boundary constraints uniquely determine the solution to the internal elliptic problem thus eliminating the non-uniqueness of the solution of an internal Neumann boundary value grid generation problem.
Streamline integration as a method for two-dimensional elliptic grid generation
Energy Technology Data Exchange (ETDEWEB)
Wiesenberger, M., E-mail: Matthias.Wiesenberger@uibk.ac.at [Institute for Ion Physics and Applied Physics, Universität Innsbruck, A-6020 Innsbruck (Austria); Held, M. [Institute for Ion Physics and Applied Physics, Universität Innsbruck, A-6020 Innsbruck (Austria); Einkemmer, L. [Numerical Analysis group, Universität Innsbruck, A-6020 Innsbruck (Austria)
2017-07-01
We propose a new numerical algorithm to construct a structured numerical elliptic grid of a doubly connected domain. Our method is applicable to domains with boundaries defined by two contour lines of a two-dimensional function. Furthermore, we can adapt any analytically given boundary aligned structured grid, which specifically includes polar and Cartesian grids. The resulting coordinate lines are orthogonal to the boundary. Grid points as well as the elements of the Jacobian matrix can be computed efficiently and up to machine precision. In the simplest case we construct conformal grids, yet with the help of weight functions and monitor metrics we can control the distribution of cells across the domain. Our algorithm is parallelizable and easy to implement with elementary numerical methods. We assess the quality of grids by considering both the distribution of cell sizes and the accuracy of the solution to elliptic problems. Among the tested grids these key properties are best fulfilled by the grid constructed with the monitor metric approach. - Graphical abstract: - Highlights: • Construct structured, elliptic numerical grids with elementary numerical methods. • Align coordinate lines with or make them orthogonal to the domain boundary. • Compute grid points and metric elements up to machine precision. • Control cell distribution by adaption functions or monitor metrics.
Liseikin, Vladimir D
2010-01-01
This book is an introduction to structured and unstructured grid methods in scientific computing, addressing graduate students, scientists as well as practitioners. Basic local and integral grid quality measures are formulated and new approaches to mesh generation are reviewed. In addition to the content of the successful first edition, a more detailed and practice oriented description of monitor metrics in Beltrami and diffusion equations is given for generating adaptive numerical grids. Also, new techniques developed by the author are presented, in particular a technique based on the inverted form of Beltrami’s partial differential equations with respect to control metrics. This technique allows the generation of adaptive grids for a wide variety of computational physics problems, including grid clustering to given function values and gradients, grid alignment with given vector fields, and combinations thereof. Applications of geometric methods to the analysis of numerical grid behavior as well as grid ge...
Liseikin, Vladimir D
2017-01-01
This new edition provides a description of current developments relating to grid methods, grid codes, and their applications to actual problems. Grid generation methods are indispensable for the numerical solution of differential equations. Adaptive grid-mapping techniques, in particular, are the main focus and represent a promising tool to deal with systems with singularities. This 3rd edition includes three new chapters on numerical implementations (10), control of grid properties (11), and applications to mechanical, fluid, and plasma related problems (13). Also the other chapters have been updated including new topics, such as curvatures of discrete surfaces (3). Concise descriptions of hybrid mesh generation, drag and sweeping methods, parallel algorithms for mesh generation have been included too. This new edition addresses a broad range of readers: students, researchers, and practitioners in applied mathematics, mechanics, engineering, physics and other areas of applications.
Elliptic Curve Cryptography-Based Authentication with Identity Protection for Smart Grids.
Directory of Open Access Journals (Sweden)
Liping Zhang
Full Text Available In a smart grid, the power service provider enables the expected power generation amount to be measured according to current power consumption, thus stabilizing the power system. However, the data transmitted over smart grids are not protected, and then suffer from several types of security threats and attacks. Thus, a robust and efficient authentication protocol should be provided to strength the security of smart grid networks. As the Supervisory Control and Data Acquisition system provides the security protection between the control center and substations in most smart grid environments, we focus on how to secure the communications between the substations and smart appliances. Existing security approaches fail to address the performance-security balance. In this study, we suggest a mitigation authentication protocol based on Elliptic Curve Cryptography with privacy protection by using a tamper-resistant device at the smart appliance side to achieve a delicate balance between performance and security of smart grids. The proposed protocol provides some attractive features such as identity protection, mutual authentication and key agreement. Finally, we demonstrate the completeness of the proposed protocol using the Gong-Needham-Yahalom logic.
Elliptic Curve Cryptography-Based Authentication with Identity Protection for Smart Grids.
Zhang, Liping; Tang, Shanyu; Luo, He
2016-01-01
In a smart grid, the power service provider enables the expected power generation amount to be measured according to current power consumption, thus stabilizing the power system. However, the data transmitted over smart grids are not protected, and then suffer from several types of security threats and attacks. Thus, a robust and efficient authentication protocol should be provided to strength the security of smart grid networks. As the Supervisory Control and Data Acquisition system provides the security protection between the control center and substations in most smart grid environments, we focus on how to secure the communications between the substations and smart appliances. Existing security approaches fail to address the performance-security balance. In this study, we suggest a mitigation authentication protocol based on Elliptic Curve Cryptography with privacy protection by using a tamper-resistant device at the smart appliance side to achieve a delicate balance between performance and security of smart grids. The proposed protocol provides some attractive features such as identity protection, mutual authentication and key agreement. Finally, we demonstrate the completeness of the proposed protocol using the Gong-Needham-Yahalom logic.
A mixed nonoverlapping covolume method on quadrilateral grids for elliptic problems
Zhao, X.; Chen, Y.; Lv, J.
2016-01-01
A covolume method is proposed for the mixed formulation of second-order elliptic problems. The solution domain is divided by a quadrilateral grid, corresponding to which a nonoverlapping dual grid is constructed. The velocity and pressure are approximated by the lowest-order Raviart–Thomas space on
Smart Grids and Distributed Generation
Directory of Open Access Journals (Sweden)
Dorin BICĂ
2018-06-01
Full Text Available This paper describes the main characteristics of Smart Grids and distributed generation. Smart Grids can be defined as a modernization of the power system so it monitors, protects and automatically optimizes the operation of its interconnected elements (power plants, transmission and distribution system, industrial and residential loads. Distributed generation (DG refers to the production of electricity near the consumption place using renewable energy sources. A load flow analysis is performed for the IEEE14 system in which a DG source (a 5MW wind turbine is added that is on-grid or off-grid. The power losses are determined for these two cases.
TIGER: Turbomachinery interactive grid generation
Soni, Bharat K.; Shih, Ming-Hsin; Janus, J. Mark
1992-01-01
A three dimensional, interactive grid generation code, TIGER, is being developed for analysis of flows around ducted or unducted propellers. TIGER is a customized grid generator that combines new technology with methods from general grid generation codes. The code generates multiple block, structured grids around multiple blade rows with a hub and shroud for either C grid or H grid topologies. The code is intended for use with a Euler/Navier-Stokes solver also being developed, but is general enough for use with other flow solvers. TIGER features a silicon graphics interactive graphics environment that displays a pop-up window, graphics window, and text window. The geometry is read as a discrete set of points with options for several industrial standard formats and NASA standard formats. Various splines are available for defining the surface geometries. Grid generation is done either interactively or through a batch mode operation using history files from a previously generated grid. The batch mode operation can be done either with a graphical display of the interactive session or with no graphics so that the code can be run on another computer system. Run time can be significantly reduced by running on a Cray-YMP.
Workshop on Future Generation Grids
Laforenza, Domenico; Reinefeld, Alexander
2006-01-01
The Internet and the Web continue to have a major impact on society. By allowing us to discover and access information on a global scale, they have created entirely new businesses and brought new meaning to the term surf. In addition, however, we want processing, and increasingly, we want collaborative processing within distributed teams. This need has led to the creation of the Grid - an infrastructure that enables us to share capabilities, and integrate services and resources within and across enterprises. "Future Generation Grids" is the second in the "CoreGRID" series. This edited volume brings together contributed articles by scientists and researchers in the Grid community in an attempt to draw a clearer picture of the future generation Grids. This book also identifies some of the most challenging problems on the way to achieving the invisible Grid ideas
Grid Synchronization for Distributed Generations
DEFF Research Database (Denmark)
Peyghami, Saeed; Mokhtari, Hossein; Blaabjerg, Frede
2017-01-01
Distributed generators (DGs) like photovoltaic arrays, wind turbines, and fuel cell modules, as well as distributed storage (DS) units introduce some advantages to the power systems and make it more reliable, flexible, and controllable in comparison with the conventional power systems. Grid inter...
Plasma blob generation due to cooperative elliptic instability.
Manz, P; Xu, M; Müller, S H; Fedorczak, N; Thakur, S C; Yu, J H; Tynan, G R
2011-11-04
Using fast-camera measurements the generation mechanism of plasma blobs is investigated in the linear device CSDX. During the ejection of plasma blobs the plasma is dominated by an m=1 mode, which is a counterrotating vortex pair. These flows are known to be subject to the cooperative elliptic instability, which is characterized by a cooperative disturbance of the vortex cores and results in a three-dimensional breakdown of two-dimensional flows. The first experimental evidence of a cooperative elliptic instability preceding the blob-ejection is provided in terms of the qualitative evolution of the vortex geometries and internal wave patterns.
Generation of Elliptically Polarized Terahertz Waves from Antiferromagnetic Sandwiched Structure.
Zhou, Sheng; Zhang, Qiang; Fu, Shu-Fang; Wang, Xuan-Zhang; Song, Yu-Ling; Wang, Xiang-Guang; Qu, Xiu-Rong
2018-04-01
The generation of elliptically polarized electromagnetic wave of an antiferromagnetic (AF)/dielectric sandwiched structure in the terahertz range is studied. The frequency and external magnetic field can change the AF optical response, resulting in the generation of elliptical polarization. An especially useful geometry with high levels of the generation of elliptical polarization is found in the case where an incident electromagnetic wave perpendicularly illuminates the sandwiched structure, the AF anisotropy axis is vertical to the wave-vector and the external magnetic field is pointed along the wave-vector. In numerical calculations, the AF layer is FeF2 and the dielectric layers are ZnF2. Although the effect originates from the AF layer, it can be also influenced by the sandwiched structure. We found that the ZnF2/FeF2/ZnF2 structure possesses optimal rotation of the principal axis and ellipticity, which can reach up to about thrice that of a single FeF2 layer.
An Adaptive Sparse Grid Algorithm for Elliptic PDEs with Lognormal Diffusion Coefficient
Nobile, Fabio
2016-03-18
In this work we build on the classical adaptive sparse grid algorithm (T. Gerstner and M. Griebel, Dimension-adaptive tensor-product quadrature), obtaining an enhanced version capable of using non-nested collocation points, and supporting quadrature and interpolation on unbounded sets. We also consider several profit indicators that are suitable to drive the adaptation process. We then use such algorithm to solve an important test case in Uncertainty Quantification problem, namely the Darcy equation with lognormal permeability random field, and compare the results with those obtained with the quasi-optimal sparse grids based on profit estimates, which we have proposed in our previous works (cf. e.g. Convergence of quasi-optimal sparse grids approximation of Hilbert-valued functions: application to random elliptic PDEs). To treat the case of rough permeability fields, in which a sparse grid approach may not be suitable, we propose to use the adaptive sparse grid quadrature as a control variate in a Monte Carlo simulation. Numerical results show that the adaptive sparse grids have performances similar to those of the quasi-optimal sparse grids and are very effective in the case of smooth permeability fields. Moreover, their use as control variate in a Monte Carlo simulation allows to tackle efficiently also problems with rough coefficients, significantly improving the performances of a standard Monte Carlo scheme.
Energy Technology Data Exchange (ETDEWEB)
Maliassov, S.Y. [Texas A& M Univ., College Station, TX (United States)
1996-12-31
An approach to the construction of an iterative method for solving systems of linear algebraic equations arising from nonconforming finite element discretizations with nonmatching grids for second order elliptic boundary value problems with anisotropic coefficients is considered. The technique suggested is based on decomposition of the original domain into nonoverlapping subdomains. The elliptic problem is presented in the macro-hybrid form with Lagrange multipliers at the interfaces between subdomains. A block diagonal preconditioner is proposed which is spectrally equivalent to the original saddle point matrix and has the optimal order of arithmetical complexity. The preconditioner includes blocks for preconditioning subdomain and interface problems. It is shown that constants of spectral equivalence axe independent of values of coefficients and mesh step size.
A new solution-adaptive grid generation method for transonic airfoil flow calculations
Nakamura, S.; Holst, T. L.
1981-01-01
The clustering algorithm is controlled by a second-order, ordinary differential equation which uses the airfoil surface density gradient as a forcing function. The solution to this differential equation produces a surface grid distribution which is automatically clustered in regions with large gradients. The interior grid points are established from this surface distribution by using an interpolation scheme which is fast and retains the desirable properties of the original grid generated from the standard elliptic equation approach.
Progress in Grid Generation: From Chimera to DRAGON Grids
Liou, Meng-Sing; Kao, Kai-Hsiung
1994-01-01
Hybrid grids, composed of structured and unstructured grids, combines the best features of both. The chimera method is a major stepstone toward a hybrid grid from which the present approach is evolved. The chimera grid composes a set of overlapped structured grids which are independently generated and body-fitted, yielding a high quality grid readily accessible for efficient solution schemes. The chimera method has been shown to be efficient to generate a grid about complex geometries and has been demonstrated to deliver accurate aerodynamic prediction of complex flows. While its geometrical flexibility is attractive, interpolation of data in the overlapped regions - which in today's practice in 3D is done in a nonconservative fashion, is not. In the present paper we propose a hybrid grid scheme that maximizes the advantages of the chimera scheme and adapts the strengths of the unstructured grid while at the same time keeps its weaknesses minimal. Like the chimera method, we first divide up the physical domain by a set of structured body-fitted grids which are separately generated and overlaid throughout a complex configuration. To eliminate any pure data manipulation which does not necessarily follow governing equations, we use non-structured grids only to directly replace the region of the arbitrarily overlapped grids. This new adaptation to the chimera thinking is coined the DRAGON grid. The nonstructured grid region sandwiched between the structured grids is limited in size, resulting in only a small increase in memory and computational effort. The DRAGON method has three important advantages: (1) preserving strengths of the chimera grid; (2) eliminating difficulties sometimes encountered in the chimera scheme, such as the orphan points and bad quality of interpolation stencils; and (3) making grid communication in a fully conservative and consistent manner insofar as the governing equations are concerned. To demonstrate its use, the governing equations are
Grid Generation Techniques Utilizing the Volume Grid Manipulator
Alter, Stephen J.
1998-01-01
This paper presents grid generation techniques available in the Volume Grid Manipulation (VGM) code. The VGM code is designed to manipulate existing line, surface and volume grids to improve the quality of the data. It embodies an easy to read rich language of commands that enables such alterations as topology changes, grid adaption and smoothing. Additionally, the VGM code can be used to construct simplified straight lines, splines, and conic sections which are common curves used in the generation and manipulation of points, lines, surfaces and volumes (i.e., grid data). These simple geometric curves are essential in the construction of domain discretizations for computational fluid dynamic simulations. By comparison to previously established methods of generating these curves interactively, the VGM code provides control of slope continuity and grid point-to-point stretchings as well as quick changes in the controlling parameters. The VGM code offers the capability to couple the generation of these geometries with an extensive manipulation methodology in a scripting language. The scripting language allows parametric studies of a vehicle geometry to be efficiently performed to evaluate favorable trends in the design process. As examples of the powerful capabilities of the VGM code, a wake flow field domain will be appended to an existing X33 Venturestar volume grid; negative volumes resulting from grid expansions to enable flow field capture on a simple geometry, will be corrected; and geometrical changes to a vehicle component of the X33 Venturestar will be shown.
Directory of Open Access Journals (Sweden)
Debiao He
2017-01-01
Full Text Available Recent advances of Internet and microelectronics technologies have led to the concept of smart grid which has been a widespread concern for industry, governments, and academia. The openness of communications in the smart grid environment makes the system vulnerable to different types of attacks. The implementation of secure communication and the protection of consumers’ privacy have become challenging issues. The data aggregation scheme is an important technique for preserving consumers’ privacy because it can stop the leakage of a specific consumer’s data. To satisfy the security requirements of practical applications, a lot of data aggregation schemes were presented over the last several years. However, most of them suffer from security weaknesses or have poor performances. To reduce computation cost and achieve better security, we construct a lightweight data aggregation scheme against internal attackers in the smart grid environment using Elliptic Curve Cryptography (ECC. Security analysis of our proposed approach shows that it is provably secure and can provide confidentiality, authentication, and integrity. Performance analysis of the proposed scheme demonstrates that both computation and communication costs of the proposed scheme are much lower than the three previous schemes. As a result of these aforementioned benefits, the proposed lightweight data aggregation scheme is more practical for deployment in the smart grid environment.
DIGRD: an interactive grid generating program
International Nuclear Information System (INIS)
Foote, H.P.; Rice, W.A.; Kincaid, C.T.
1982-11-01
Pacific Northwest Laboratory has completed the development and documentation of an interactive grid generating program (DIGRD, digitize grid). This program is designed to rapidly generate or modify grids necessary for the unsaturated flow code TRUST. In addition to the code, a user's manual was prepared. Unfortunately, the computer hardware that comprises the PNL interactive graphics capability is unique. Direct technology transfer is not possible, therefore, this report is intended to convey the utility of interactive graphics in supplying a grid generating capability. DIGRD has already been effectively used in the preparation of grids for the analysis of leachate movement from uranium mill tailings. The principal conclusion is that the interactive graphics employed in DIGRD are useful and economical in the development of complex grids. Grid generation activities that previously took between a half- and a full-man month can now be completed in less than a week. DIGRD users have recommended development of an uniform grid of either rectangles or equilateral triangles, which could be superimposed on any domain and then adjusted through the DIGRD program to match the boundaries of a tailings disposal facility. This improvement to the DIGRD package could further reduce the effort in grid generation while providing more optimal grids
Random source generating far field with elliptical flat-topped beam profile
International Nuclear Information System (INIS)
Zhang, Yongtao; Cai, Yangjian
2014-01-01
Circular and rectangular multi-Gaussian Schell-model (MGSM) sources which generate far fields with circular and rectangular flat-topped beam profiles were introduced just recently (Sahin and Korotkova 2012 Opt. Lett. 37 2970; Korotkova 2014 Opt. Lett. 39 64). In this paper, a random source named an elliptical MGSM source is introduced. An analytical expression for the propagation factor of an elliptical MGSM beam is derived. Furthermore, an analytical propagation formula for an elliptical MGSM beam passing through a stigmatic ABCD optical system is derived, and its propagation properties in free space are studied. It is interesting to find that an elliptical MGSM source generates a far field with an elliptical flat-topped beam profile, being qualitatively different from that of circular and rectangular MGSM sources. The ellipticity and the flatness of the elliptical flat-topped beam profile in the far field are determined by the initial coherence widths and the beam index, respectively. (paper)
Generation of an elliptic hollow beam using Mathieu and Bessel functions.
Chakraborty, Rijuparna; Ghosh, Ajay
2006-09-01
A new (to our knowledge) technique for the generation of a propagation-invariant elliptic hollow beam is reported. It avoids the use of the radial Mathieu function and hence is mathematically simpler. Bessel functions with their arguments having elliptic locus are used to generate the mask, which is then recorded using holographic technique. To generate such an elliptic beam, both the angular Mathieu function, i.e., elliptic vortex term, and the expression for the circular vortex are used separately. The resultant mask is illuminated with a plane beam, and the proper filtering of its Fourier transform generates the expected elliptic beam. Results with both vortex terms are satisfactory. It has been observed that even for higher ellipticity the vortices do not separate.
GENIE - Generation of computational geometry-grids for internal-external flow configurations
Soni, B. K.
1988-01-01
Progress realized in the development of a master geometry-grid generation code GENIE is presented. The grid refinement process is enhanced by developing strategies to utilize bezier curves/surfaces and splines along with weighted transfinite interpolation technique and by formulating new forcing function for the elliptic solver based on the minimization of a non-orthogonality functional. A two step grid adaptation procedure is developed by optimally blending adaptive weightings with weighted transfinite interpolation technique. Examples of 2D-3D grids are provided to illustrate the success of these methods.
Modeling and Grid Generation of Iced Airfoils
Vickerman, Mary B.; Baez, Marivell; Braun, Donald C.; Hackenberg, Anthony W.; Pennline, James A.; Schilling, Herbert W.
2007-01-01
SmaggIce Version 2.0 is a software toolkit for geometric modeling and grid generation for two-dimensional, singleand multi-element, clean and iced airfoils. A previous version of SmaggIce was described in Preparing and Analyzing Iced Airfoils, NASA Tech Briefs, Vol. 28, No. 8 (August 2004), page 32. To recapitulate: Ice shapes make it difficult to generate quality grids around airfoils, yet these grids are essential for predicting ice-induced complex flow. This software efficiently creates high-quality structured grids with tools that are uniquely tailored for various ice shapes. SmaggIce Version 2.0 significantly enhances the previous version primarily by adding the capability to generate grids for multi-element airfoils. This version of the software is an important step in streamlining the aeronautical analysis of ice airfoils using computational fluid dynamics (CFD) tools. The user may prepare the ice shape, define the flow domain, decompose it into blocks, generate grids, modify/divide/merge blocks, and control grid density and smoothness. All these steps may be performed efficiently even for the difficult glaze and rime ice shapes. Providing the means to generate highly controlled grids near rough ice, the software includes the creation of a wrap-around block (called the "viscous sublayer block"), which is a thin, C-type block around the wake line and iced airfoil. For multi-element airfoils, the software makes use of grids that wrap around and fill in the areas between the viscous sub-layer blocks for all elements that make up the airfoil. A scripting feature records the history of interactive steps, which can be edited and replayed later to produce other grids. Using this version of SmaggIce, ice shape handling and grid generation can become a practical engineering process, rather than a laborious research effort.
Multilevel Methods for Elliptic Problems with Highly Varying Coefficients on Nonaligned Coarse Grids
Energy Technology Data Exchange (ETDEWEB)
Scheichl, Robert [Univ. of Bath (United Kingdom). Dept. of Mathematical Sciences; Vassilevski, Panayot S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zikatanov, Ludmil T. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mathematics
2012-06-21
We generalize the analysis of classical multigrid and two-level overlapping Schwarz methods for 2nd order elliptic boundary value problems to problems with large discontinuities in the coefficients that are not resolved by the coarse grids or the subdomain partition. The theoretical results provide a recipe for designing hierarchies of standard piecewise linear coarse spaces such that the multigrid convergence rate and the condition number of the Schwarz preconditioned system do not depend on the coefficient variation or on any mesh parameters. One assumption we have to make is that the coarse grids are sufficiently fine in the vicinity of cross points or where regions with large diffusion coefficients are separated by a narrow region where the coefficient is small. We do not need to align them with possible discontinuities in the coefficients. The proofs make use of novel stable splittings based on weighted quasi-interpolants and weighted Poincaré-type inequalities. Finally, numerical experiments are included that illustrate the sharpness of the theoretical bounds and the necessity of the technical assumptions.
Middleware for the next generation Grid infrastructure
Laure, E; Prelz, F; Beco, S; Fisher, S; Livny, M; Guy, L; Barroso, M; Buncic, P; Kunszt, Peter Z; Di Meglio, A; Aimar, A; Edlund, A; Groep, D; Pacini, F; Sgaravatto, M; Mulmo, O
2005-01-01
The aim of the EGEE (Enabling Grids for E-Science in Europe) project is to create a reliable and dependable European Grid infrastructure for e-Science. The objective of the EGEE Middleware Re-engineering and Integration Research Activity is to provide robust middleware components, deployable on several platforms and operating systems, corresponding to the core Grid services for resource access, data management, information collection, authentication & authorization, resource matchmaking and brokering, and monitoring and accounting. For achieving this objective, we developed an architecture and design of the next generation Grid middleware leveraging experiences and existing components essentially from AliEn, EDG, and VDT. The architecture follows the service breakdown developed by the LCG ARDA group. Our strategy is to do as little original development as possible but rather re-engineer and harden existing Grid services. The evolution of these middleware components towards a Service Oriented Architecture ...
Nobile, F.
2015-10-30
In this work we provide a convergence analysis for the quasi-optimal version of the sparse-grids stochastic collocation method we presented in a previous work: “On the optimal polynomial approximation of stochastic PDEs by Galerkin and collocation methods” (Beck et al., Math Models Methods Appl Sci 22(09), 2012). The construction of a sparse grid is recast into a knapsack problem: a profit is assigned to each hierarchical surplus and only the most profitable ones are added to the sparse grid. The convergence rate of the sparse grid approximation error with respect to the number of points in the grid is then shown to depend on weighted summability properties of the sequence of profits. This is a very general argument that can be applied to sparse grids built with any uni-variate family of points, both nested and non-nested. As an example, we apply such quasi-optimal sparse grids to the solution of a particular elliptic PDE with stochastic diffusion coefficients, namely the “inclusions problem”: we detail the convergence estimates obtained in this case using polynomial interpolation on either nested (Clenshaw–Curtis) or non-nested (Gauss–Legendre) abscissas, verify their sharpness numerically, and compare the performance of the resulting quasi-optimal grids with a few alternative sparse-grid construction schemes recently proposed in the literature.
Nobile, F.; Tamellini, L.; Tempone, Raul
2015-01-01
In this work we provide a convergence analysis for the quasi-optimal version of the sparse-grids stochastic collocation method we presented in a previous work: “On the optimal polynomial approximation of stochastic PDEs by Galerkin and collocation methods” (Beck et al., Math Models Methods Appl Sci 22(09), 2012). The construction of a sparse grid is recast into a knapsack problem: a profit is assigned to each hierarchical surplus and only the most profitable ones are added to the sparse grid. The convergence rate of the sparse grid approximation error with respect to the number of points in the grid is then shown to depend on weighted summability properties of the sequence of profits. This is a very general argument that can be applied to sparse grids built with any uni-variate family of points, both nested and non-nested. As an example, we apply such quasi-optimal sparse grids to the solution of a particular elliptic PDE with stochastic diffusion coefficients, namely the “inclusions problem”: we detail the convergence estimates obtained in this case using polynomial interpolation on either nested (Clenshaw–Curtis) or non-nested (Gauss–Legendre) abscissas, verify their sharpness numerically, and compare the performance of the resulting quasi-optimal grids with a few alternative sparse-grid construction schemes recently proposed in the literature.
Energy Technology Data Exchange (ETDEWEB)
Katz, Jessica; Cochran, Jaquelin
2015-05-27
Greening the Grid provides technical assistance to energy system planners, regulators, and grid operators to overcome challenges associated with integrating variable renewable energy into the grid. This document, part of a Greening the Grid toolkit, provides power system planners with tips to help secure and sustain investment in new renewable energy generation by aligning renewable energy policy targets and incentives with grid integration considerations.
Ellipticity and the offset angle of high harmonics generated by homonuclear diatomic molecules
International Nuclear Information System (INIS)
Odzak, S; Milosevic, D B
2011-01-01
In our recent paper (2010 Phys. Rev. A 82 023412) we introduced a theory of high-order harmonic generation by diatomic molecules exposed to an elliptically polarized laser field and have shown that the nth harmonic emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. Using both components of the T-matrix element we now develop a theoretical approach for calculating ellipticity and the offset angle of high harmonics. We show that the emitted harmonics generated by aligned molecules are elliptically polarized even if the applied field is linearly polarized. Using examples of N 2 , O 2 and Ar 2 molecules we show the existence of extrema and sudden changes of the harmonic ellipticity and the offset angle for particular molecular alignment and explain them by the destructive two-centre interference. Taking into account that the aligned molecules are an anisotropic medium for high harmonic generation, we introduce elliptic dichroism as a measure of this anisotropy, for both components of the T-matrix element. We propose that the measurement of the elliptic dichroism may reveal further information about the molecular structure.
Grid code requirements for wind power generation
International Nuclear Information System (INIS)
Djagarov, N.; Filchev, S.; Grozdev, Z.; Bonev, M.
2011-01-01
In this paper production data of wind power in Europe and Bulgaria and plans for their development within 2030 are reviewed. The main characteristics of wind generators used in Bulgaria are listed. A review of the grid code in different European countries, which regulate the requirements for renewable sources, is made. European recommendations for requirements harmonization are analyzed. Suggestions for the Bulgarian gird code are made
Flames in fractal grid generated turbulence
Energy Technology Data Exchange (ETDEWEB)
Goh, K H H; Hampp, F; Lindstedt, R P [Department of Mechanical Engineering, Imperial College, London SW7 2AZ (United Kingdom); Geipel, P, E-mail: p.lindstedt@imperial.ac.uk [Siemens Industrial Turbomachinery AB, SE-612 83 Finspong (Sweden)
2013-12-15
Twin premixed turbulent opposed jet flames were stabilized for lean mixtures of air with methane and propane in fractal grid generated turbulence. A density segregation method was applied alongside particle image velocimetry to obtain velocity and scalar statistics. It is shown that the current fractal grids increase the turbulence levels by around a factor of 2. Proper orthogonal decomposition (POD) was applied to show that the fractal grids produce slightly larger turbulent structures that decay at a slower rate as compared to conventional perforated plates. Conditional POD (CPOD) was also implemented using the density segregation technique and the results show that CPOD is essential to segregate the relative structures and turbulent kinetic energy distributions in each stream. The Kolmogorov length scales were also estimated providing values {approx}0.1 and {approx}0.5 mm in the reactants and products, respectively. Resolved profiles of flame surface density indicate that a thin flame assumption leading to bimodal statistics is not perfectly valid under the current conditions and it is expected that the data obtained will be of significant value to the development of computational methods that can provide information on the conditional structure of turbulence. It is concluded that the increase in the turbulent Reynolds number is without any negative impact on other parameters and that fractal grids provide a route towards removing the classical problem of a relatively low ratio of turbulent to bulk strain associated with the opposed jet configuration. (paper)
Alternatives to the grid : distributed generation
Energy Technology Data Exchange (ETDEWEB)
Kline, R.H. [Mercury Electric Co., Calgary, AB (Canada)
2002-07-01
This presentation outlines the benefits of distributed generation with reference to energy drivers, reliability, power quality, and the impact of open energy markets. Deregulation in Alberta's electric power industry has created options and imposed responsibilities on both industrial and commercial consumers. Customers have the option to self-generate a portion or all of their energy needs. The options are to buy energy from a power marketer, to buy energy from the Power Pool of Alberta, to develop one's own power, or to contract with an independent power producer. It is important to understand base load and peaking requirements in order to determine which option is best, where power quality and reliability will not be compromised. Small scale on-site power generation offers advantages such as reduced peak strain on the transmission grid, and reduced total energy costs. Regulatory changes are making it easier than ever to make the transition to distributed generation. The author briefly reviews the advantages of reciprocating engines and turbine-based generators. He notes that fuel cells, solar, and wind generators are not currently economically viable options. Mercury Electric's conventional turbine systems are illustrated as a potential viable option for self-generation. 2 figs.
Alternatives to the grid : distributed generation
Energy Technology Data Exchange (ETDEWEB)
Kline, R.H. [Mercury Electric Corp., Calgary, AB (Canada)
2001-07-01
This presentation highlighted the merits of distributed generation. The author began by discussing energy drivers, touching on issues such as reliability, power quality, and the confusion resulting from the energy market, and energy costs. It was pointed out that the deregulation of the electricity market in Alberta was implemented on January 1, 1996 which has resulted in steady price increases ever since. A review of the options available to the customer begin by understanding baseload and peaking. The options then available are buying from the utility, buying through a reputable marketer, buying direct from a large scale independent power producer, on-site generation, and finally, distributed generation. The emphasis was placed on distributed generation defined as small scale on-site power generation and offers advantages such as the reduction/elimination of peak strain on grid, and offset/defer utility capital costs, therefore reducing total energy costs. Regulatory changes are making it easier than ever before to make the transition to distributed generation. The author briefly reviewed the advantages of microturbines then presented the Honeywell Parallon 75 TurboGenerator{sup TM}, reviewing its characteristics, operating modes and commercial applications. Examples were provided of successful microturbines installations throughout the country. figs.
Emissions & Generation Resource Integrated Database (eGRID), eGRID2012
U.S. Environmental Protection Agency — The Emissions emissions rates; net generation; resource mix; and many other attributes. eGRID2012 Version 1.0 is the eighth edition of eGRID, which contains the...
An Adaptive Sparse Grid Algorithm for Elliptic PDEs with Lognormal Diffusion Coefficient
Nobile, Fabio; Tamellini, Lorenzo; Tesei, Francesco; Tempone, Raul
2016-01-01
In this work we build on the classical adaptive sparse grid algorithm (T. Gerstner and M. Griebel, Dimension-adaptive tensor-product quadrature), obtaining an enhanced version capable of using non-nested collocation points, and supporting quadrature
A Family of Multipoint Flux Mixed Finite Element Methods for Elliptic Problems on General Grids
Wheeler, Mary F.; Xue, Guangri; Yotov, Ivan
2011-01-01
In this paper, we discuss a family of multipoint flux mixed finite element (MFMFE) methods on simplicial, quadrilateral, hexahedral, and triangular-prismatic grids. The MFMFE methods are locally conservative with continuous normal fluxes, since
A Family of Multipoint Flux Mixed Finite Element Methods for Elliptic Problems on General Grids
Wheeler, Mary F.
2011-01-01
In this paper, we discuss a family of multipoint flux mixed finite element (MFMFE) methods on simplicial, quadrilateral, hexahedral, and triangular-prismatic grids. The MFMFE methods are locally conservative with continuous normal fluxes, since they are developed within a variational framework as mixed finite element methods with special approximating spaces and quadrature rules. The latter allows for local flux elimination giving a cell-centered system for the scalar variable. We study two versions of the method: with a symmetric quadrature rule on smooth grids and a non-symmetric quadrature rule on rough grids. Theoretical and numerical results demonstrate first order convergence for problems with full-tensor coefficients. Second order superconvergence is observed on smooth grids. © 2011 Published by Elsevier Ltd.
Comparison of two superconducting elliptical undulators for generating circularly polarized light
Directory of Open Access Journals (Sweden)
C. S. Hwang
2004-09-01
Full Text Available The potential use of two planar superconducting elliptical undulators—a vertically wound racetrack coil structure and a staggered array structure—to generate a circularly polarized hard x-ray source was investigated. The magnetic poles and wires of the up and down magnet arrays were rotated in alternating directions on the horizontal plane, an elliptical field is generated to provide circularly polarized light in the electron-storage ring and the energy-recovery linac accelerator. Rapid switching between right- and left-circularly polarized radiations is performed using two undulators with oppositely rotated wires and poles. Given a periodic length of 15 mm and a gap of 5 mm, the magnetic-flux densities in the elliptical undulator are B_{z}=1.2 T (B_{x}=0.6 T and B_{z}=0.35 T (B_{x}=0.15 T in the planar vertically wound racetrack coil and the staggered structure with poles rotated by 35° and 25°, respectively. In maximizing the merit of the flux and the width of the effective field region in the two superconducting elliptical undulators, the trade-off rotation angles of the coils and poles are 20° and 5°, for vertically wound racetrack coil and staggered undulators, respectively.
Grid-Connected Inverter for Distributed Generation in Microgrid
DEFF Research Database (Denmark)
Naderipour, Amirreza; Miveh, Mohammad Reza; Guerrero, Josep M.
for power generation. DGS units can operate in parallel to the main grid or in a Microgrid (MG) mode. An MG is a discrete energy system consisting of DGSs and loads capable of operating in parallel with, or independently from, the main grid. Meanwhile, Grid-Connected Inverters (GCIs) are typically used...
A comparative study of the parabolized Navier-Stokes code using various grid-generation techniques
Kaul, U. K.; Chaussee, D. S.
1985-01-01
The parabolized Navier-Stokes (PNS) equations are used to calculate the flow-field characteristics about the hypersonic research aircraft X-24C. A comparison of the results obtained using elliptic, hyperbolic and algebraic grid generators is presented. The outer bow shock is treated as a sharp discontinuity, and the discontinuities within the shock layer are captured. Surface pressures and heat-transfer results at angles of attack of 6 deg and 20 deg, obtained using the three grid generators, are compared. The PNS equations are marched downstream over the body in both Cartesian and cylindrical base coordinate systems, and the results are compared. A robust marching procedure is demonstrated by successfully using large marching-step sizes with the implicit shock fitting procedure. A correlation is found between the marching-step size, Reynolds number and the angle of attack at fixed values of smoothing and stability coefficients for the marching scheme.
Ellipticity dependence of high harmonics generated using 400 nm driving lasers
Cheng, Yan; Khan, Sabih; Zhao, Kun; Zhao, Baozhen; Chini, Michael; Chang, Zenghu
2011-05-01
High order harmonics generated from 400 nm driving pulses hold promise of scaling photon flux of single attosecond pulses by one to two orders of magnitude. We report ellipticity dependence and phase matching of high order harmonics generated from such pulses in Neon gas target and compared them with similar measurements using 800 nm driving pulses. Based on measured ellipticity dependence, we predict that double optical gating (DOG) and generalized double optical gating (GDOG) can be employed to extract intense single attosecond pulses from pulse train, while polarization gating (PG) may not work for this purpose. This material is supported by the U.S. Army Research Office under grant number W911NF-07-1-0475, and by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.
Study of the integration of distributed generation systems in the grid: application in micro-grids
International Nuclear Information System (INIS)
Gaztanaga Arantzamendi, H.
2006-12-01
The present PhD deals with an original micro-grid concept and its application as a Renewable Energy Source's (RES) grid integration scheme. This micro-grid is composed of RES generators as well as support systems that incorporate additional functionalities in order to improve RES integration into the grid. According to this concept, two practical micro-grid applications have been studied in detail: a residential micro-grid and a wind farm supported by DFACTS systems (STATCOM and DVR). In both applications, the control structures which are implemented at different levels and applied to the different micro-grid elements have been developed, analyzed by means of off-line simulations and finally validated in real-time conditions with physical reduced-scale prototypes. (author)
Free piston linear generator for low grid power generation
Directory of Open Access Journals (Sweden)
Abdalla Izzeldin
2017-01-01
Full Text Available Generating power is of great importance nowadays across the world. However, recently, the world became aware of the climatic changes due to the greenhouse effect caused by CO2 emissions and began seeking solutions to reduce the negative impact on the environment. Besides, the exhaustion of fossil fuels and their environmental impact, make it is crucial to develop clean energy sources, and efforts are focused on developing and improving the efficiency of all energy consuming systems. The tubular permanent magnet linear generators (TPMLGs are the best candidate for energy converters. Despite being suffering problem of attraction force between permanent magnets and stator teeth, to eliminate such attraction force, ironless-stator could be considered. Thus, they could waive the presence of any magnetic attraction between the moving and stator part. This paper presents the design and analysis of ironless -cored TPMLG for low grid power generation. The main advantages of this generator are the low cogging force and high efficiency. Therefore, the magnetic field computation of the proposed generator has been performed by applying a magnetic vector potential and utilizing a 2-D finite element analysis (FEA. Moreover, the experimental results for the current profile, pressure profile and velocity profile have been presented.
Grid Monitoring and Advanced Control of Distributed Power Generation Systems
DEFF Research Database (Denmark)
Timbus, Adrian Vasile
. As an example, the latest published grid codes stress the ability of distributed generators, especially wind turbines, to stay connected during short grid disturbances and in addition to provide active/reactive power control at the point of common coupling. Based on the above facts, the need for improving...... reported in some countries creating concerns about power system stability. This leads to a continuous evolution of grid interconnection requirements towards a better controllability of generated power and an enhanced contribution of distributed power generation systems to power system stability...... and adding more features to the control of distributed power generation systems (DPGS) arises. As a consequence, this thesis focuses on grid monitoring methods and possible approaches in control in order to obtain a more reliable and exible power generation system during normal and faulty grid conditions...
Emission & Generation Resource Integrated Database (eGRID)
U.S. Environmental Protection Agency — The Emissions & Generation Resource Integrated Database (eGRID) is an integrated source of data on environmental characteristics of electric power generation....
SECOND-GENERATION STELLAR DISKS IN DENSE STAR CLUSTERS AND CLUSTER ELLIPTICITIES
International Nuclear Information System (INIS)
Mastrobuono-Battisti, Alessandra; Perets, Hagai B.
2016-01-01
Globular clusters (GCs) and nuclear star clusters (NSCs) are typically composed of several stellar populations, characterized by different chemical compositions. Different populations show different ages in NSCs, but not necessarily in GCs. The youngest populations in NSCs appear to reside in disk-like structures as observed in our Galaxy and in M31. Gas infall followed by formation of second-generation (SG) stars in GCs may similarly form disk-like structures in the clusters nuclei. Here we explore this possibility and follow the long-term evolution of stellar disks embedded in GCs, and study their effects on the evolution of the clusters. We study disks with different masses by means of detailed N-body simulations and explore their morphological and kinematic signatures on the GC structures. We find that as a SG disk relaxes, the old, first-generation stellar population flattens and becomes more radially anisotropic, making the GC structure become more elliptical. The SG stellar population is characterized by a lower velocity dispersion and a higher rotational velocity compared with the primordial older population. The strength of these kinematic signatures depends both on the relaxation time of the system and on the fractional mass of the SG disk. We therefore conclude that SG populations formed in flattened configurations will give rise to two systematic trends: (1) a positive correlation between GC ellipticity and fraction of SG population and (2) a positive correlation between GC relaxation time and ellipticity. Therefore, GC ellipticities and rotation could be related to the formation of SG stars and their initial configuration.
MESH2D Grid generator design and use
Energy Technology Data Exchange (ETDEWEB)
Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2017-10-31
Mesh2d is a Fortran90 program originally designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). x-coordinates depending only on index i implies strictly vertical x-grid lines, whereas the y-grid lines can undulate. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations. Since the original development effort, Mesh2d has been extended to more general two-dimensional structured grids of the form [x(i,j),(i,j)].
New challenges in grid generation and adaptivity for scientific computing
Formaggia, Luca
2015-01-01
This volume collects selected contributions from the “Fourth Tetrahedron Workshop on Grid Generation for Numerical Computations”, which was held in Verbania, Italy in July 2013. The previous editions of this Workshop were hosted by the Weierstrass Institute in Berlin (2005), by INRIA Rocquencourt in Paris (2007), and by Swansea University (2010). This book covers different, though related, aspects of the field: the generation of quality grids for complex three-dimensional geometries; parallel mesh generation algorithms; mesh adaptation, including both theoretical and implementation aspects; grid generation and adaptation on surfaces – all with an interesting mix of numerical analysis, computer science and strongly application-oriented problems.
Integration issues of distributed generation in distribution grids
Coster, E.J.; Myrzik, J.M.A.; Kruimer, B.; Kling, W.L.
2011-01-01
In today’s distribution grids the number of distributed generation (DG) units is increasing rapidly. Combined heat and power (CHP) plants and wind turbines are most often installed. Integration of these DG units into the distribution grid leads to planning as well as operational challenges. Based on
A Survey on Next-generation Power Grid Data Architecture
Energy Technology Data Exchange (ETDEWEB)
You, Shutang [University of Tennessee, Knoxville (UTK); Zhu, Dr. Lin [University of Tennessee (UT); Liu, Yong [ORNL; Liu, Yilu [ORNL; Shankar, Mallikarjun (Arjun) [ORNL; Robertson, Russell [Grid Protection Alliance; King Jr, Thomas J [ORNL
2015-01-01
The operation and control of power grids will increasingly rely on data. A high-speed, reliable, flexible and secure data architecture is the prerequisite of the next-generation power grid. This paper summarizes the challenges in collecting and utilizing power grid data, and then provides reference data architecture for future power grids. Based on the data architecture deployment, related research on data architecture is reviewed and summarized in several categories including data measurement/actuation, data transmission, data service layer, data utilization, as well as two cross-cutting issues, interoperability and cyber security. Research gaps and future work are also presented.
Emissions & Generation Resource Integrated Database (eGRID), eGRID2010
U.S. Environmental Protection Agency — The Emissions emissions rates; net generation; resource mix; and many other attributes. eGRID2010 contains the complete release of year 2007 data, as well as years...
Grid generation for the solution of partial differential equations
Eiseman, Peter R.; Erlebacher, Gordon
1989-01-01
A general survey of grid generators is presented with a concern for understanding why grids are necessary, how they are applied, and how they are generated. After an examination of the need for meshes, the overall applications setting is established with a categorization of the various connectivity patterns. This is split between structured grids and unstructured meshes. Altogether, the categorization establishes the foundation upon which grid generation techniques are developed. The two primary categories are algebraic techniques and partial differential equation techniques. These are each split into basic parts, and accordingly are individually examined in some detail. In the process, the interrelations between the various parts are accented. From the established background in the primary techniques, consideration is shifted to the topic of interactive grid generation and then to adaptive meshes. The setting for adaptivity is established with a suitable means to monitor severe solution behavior. Adaptive grids are considered first and are followed by adaptive triangular meshes. Then the consideration shifts to the temporal coupling between grid generators and PDE-solvers. To conclude, a reflection upon the discussion, herein, is given.
Grid-connected inverter for wind power generation system
Institute of Scientific and Technical Information of China (English)
YANG Yong; RUAN Yi; SHEN Huan-qing; TANG Yan-yan; YANG Ying
2009-01-01
In wind power generation system the grid-connected inverter is an important section for energy conversion and transmission, of which the performance has a direct influence on the entire wind power generation system. The mathematical model of the grid-connected inverter is deduced firstly. Then, the space vector pulse width modulation (SVPWM) is analyzed. The power factor can be controlled close to unity, leading or lagging, which is realized based on PI-type current controller and grid voltage vector-oriented control. The control strategy is verified by the simulation and experimental results with a good sinusoidal current, a small harmonic component and a fast dynamic response.
Modelling of Diesel Generator Sets That Assist Off-Grid Renewable Energy Micro-grids
Directory of Open Access Journals (Sweden)
Johanna Salazar
2015-08-01
Full Text Available This paper focuses on modelling diesel generators for off-grid installations based on renewable energies. Variations in Environmental Variables (for example, Solar Radiation and Wind Speed make necessary to include these auxiliary systems in off-grid renewable energy installations, in order to ensure minimal services when the produced renewable energy is not sufficient to fulfill the demand. This paper concentrates on modelling the dynamical behaviour of the diesel generator, in order to use the models and simulations for developing and testing advanced controllers for the overall off-grid system. The Diesel generator is assumed to consist of a diesel motor connected to a synchronous generator through an electromagnetic clutch, with a flywheel to damp variations. Each of the components is modelled using physical models, with the corresponding control systems also modelled: these control systems include the speed and the voltage regulation (in cascade regulation.
Automatic Overset Grid Generation with Heuristic Feedback Control
Robinson, Peter I.
2001-01-01
An advancing front grid generation system for structured Overset grids is presented which automatically modifies Overset structured surface grids and control lines until user-specified grid qualities are achieved. The system is demonstrated on two examples: the first refines a space shuttle fuselage control line until global truncation error is achieved; the second advances, from control lines, the space shuttle orbiter fuselage top and fuselage side surface grids until proper overlap is achieved. Surface grids are generated in minutes for complex geometries. The system is implemented as a heuristic feedback control (HFC) expert system which iteratively modifies the input specifications for Overset control line and surface grids. It is developed as an extension of modern control theory, production rules systems and subsumption architectures. The methodology provides benefits over the full knowledge lifecycle of an expert system for knowledge acquisition, knowledge representation, and knowledge execution. The vector/matrix framework of modern control theory systematically acquires and represents expert system knowledge. Missing matrix elements imply missing expert knowledge. The execution of the expert system knowledge is performed through symbolic execution of the matrix algebra equations of modern control theory. The dot product operation of matrix algebra is generalized for heuristic symbolic terms. Constant time execution is guaranteed.
Virtual laboratory of electrical mini-grids with distributed generation
International Nuclear Information System (INIS)
Menezes Ramos, Vanessa; Barros Galhardo, Marcos André; Oliveira Barbosa, Claudomiro Fábio de; Tavares Pinho, João
2015-01-01
This paper presents a computing tool called Virtual Laboratory de Minirredes (Virtual Laboratory of Mini-grids). Using the virtual environment of the developed tool, it is possible to make remote connection/disconnection of switches and loads (resistive, inductive, capacitive and non-linear) at strategic points of the electric mini-grid with hybrid distributed generation systems (solar photovoltaic-diesel). The mini-grid has a length of about 1 km and is installed in the test area of the Grupo de Estudios e Desenvolvimento de Alternativas Exergética (GEDAE) of the Universidade Federal do Pará, located in the city of Belém, Pará, Brazil. The developed tool has communication functions with electric parameters transducers and programmable logic controllers (PLCs). This communication enables the opening and closing of contactors, resulting in different settings for the mini-grid. In addition to that, based on the proposed configuration by the user, the real-time operation status of mini-grid is presented in a graphic interface (for example, monitored electric parameters, distributed generators connected, status of disconnected switches, etc.) and the acquired data is stored. The use of the computing tool also focuses on the construction of a database, in order to obtain knowledge about the mini-grid performance under various conditions that can be set, depending on the operational strategy adopted, based on the choice of the layout, loads and power sources used in the mini-grid. (full text)
Wingridder - an interactive grid generator for TOUGH2
International Nuclear Information System (INIS)
Pan, Lehua
2003-01-01
The TOUGH (Transport Of Unsaturated Groundwater and Heat) family of codes has great flexibility in handling the variety of grid information required to describe a complex subsurface system. However, designing and generating such a grid can be a tedious and error-prone process. This is especially true when the number of cells and connections is very large. As a user-friendly, efficient, and effective grid generating software, WinGridder has been developed for designing, generating, and visualizing (at various spatial scales) numerical grids used in reservoir simulations and groundwater modeling studies. It can save mesh files for TOUGH family codes. It can also output additional grid information for various purposes in either graphic format or plain text format. It has user-friendly graphical user interfaces, along with an easy-to-use interactive design and plot tools. Many important features, such as inclined faults and offset, layering structure, local refinements, and embedded engineering structures, can be represented in the grid
Recent Developments in Grid Generation and Force Integration Technology for Overset Grids
Chan, William M.; VanDalsem, William R. (Technical Monitor)
1994-01-01
Recent developments in algorithms and software tools for generating overset grids for complex configurations are described. These include the overset surface grid generation code SURGRD and version 2.0 of the hyperbolic volume grid generation code HYPGEN. The SURGRD code is in beta test mode where the new features include the capability to march over a collection of panel networks, a variety of ways to control the side boundaries and the marching step sizes and distance, a more robust projection scheme and an interpolation option. New features in version 2.0 of HYPGEN include a wider range of boundary condition types. The code also allows the user to specify different marching step sizes and distance for each point on the surface grid. A scheme that takes into account of the overlapped zones on the body surface for the purpose of forces and moments computation is also briefly described, The process involves the following two software modules: MIXSUR - a composite grid generation module to produce a collection of quadrilaterals and triangles on which pressure and viscous stresses are to be integrated, and OVERINT - a forces and moments integration module.
Grid support by power electronic converters of distributed generation units
Morren, J.
2006-01-01
An increasing number of small Distributed Generation (DG) units are connected to the grid. The introduction of DG causes several problems, which are mainly related to the differences between DG units and conventional generators. Four problems have been considered in this thesis: damping of
Distributed Generation to Counter Grid Vulnerability
National Research Council Canada - National Science Library
Nerad, Anton H
2007-01-01
... power generation and distribution capabilities, outline several terrorist designs for disruption to it and the resulting economic impact, and provide a possible solution with the adoption of a concept...
Xu, Danfeng; Gu, Bing; Rui, Guanghao; Zhan, Qiwen; Cui, Yiping
2016-02-22
We present an arbitrary vector field with hybrid polarization based on the combination of a pair of orthogonal elliptically polarized base vectors on the Poincaré sphere. It is shown that the created vector field is only dependent on the latitude angle 2χ but is independent on the longitude angle 2ψ on the Poincaré sphere. By adjusting the latitude angle 2χ, which is related to two identical waveplates in a common path interferometric arrangement, one could obtain arbitrary type of vector fields. Experimentally, we demonstrate the generation of such kind of vector fields and confirm the distribution of state of polarization by the measurement of Stokes parameters. Besides, we investigate the tight focusing properties of these vector fields. It is found that the additional degree of freedom 2χ provided by arbitrary vector field with hybrid polarization allows one to control the spatial structure of polarization and to engineer the focusing field.
Grid Voltage Synchronization for Distributed Generation Systems under Grid Fault Conditions
DEFF Research Database (Denmark)
Luna, Alvaro; Rocabert, J.; Candela, I.
2015-01-01
on the installation of STATCOMs and DVRs, as well as on advanced control functionalities for the existing power converters of distributed generation plants, have contributed to enhance their response under faulty and distorted scenarios and, hence, to fulfill these requirements. In order to achieve satisfactory......The actual grid code requirements for the grid connection of distributed generation systems, mainly wind and PV systems, are becoming very demanding. The Transmission System Operators (TSOs) are especially concerned about the Low Voltage Ride Through requirements. Solutions based...
Parallel grid generation algorithm for distributed memory computers
Moitra, Stuti; Moitra, Anutosh
1994-01-01
A parallel grid-generation algorithm and its implementation on the Intel iPSC/860 computer are described. The grid-generation scheme is based on an algebraic formulation of homotopic relations. Methods for utilizing the inherent parallelism of the grid-generation scheme are described, and implementation of multiple levELs of parallelism on multiple instruction multiple data machines are indicated. The algorithm is capable of providing near orthogonality and spacing control at solid boundaries while requiring minimal interprocessor communications. Results obtained on the Intel hypercube for a blended wing-body configuration are used to demonstrate the effectiveness of the algorithm. Fortran implementations bAsed on the native programming model of the iPSC/860 computer and the Express system of software tools are reported. Computational gains in execution time speed-up ratios are given.
Turbulent premixed flames on fractal-grid-generated turbulence
Energy Technology Data Exchange (ETDEWEB)
Soulopoulos, N; Kerl, J; Sponfeldner, T; Beyrau, F; Hardalupas, Y; Taylor, A M K P [Mechanical Engineering Department, Imperial College London, London SW7 2AZ (United Kingdom); Vassilicos, J C, E-mail: ns6@ic.ac.uk [Department of Aeronautics, Imperial College London, London SW7 2AZ (United Kingdom)
2013-12-15
A space-filling, low blockage fractal grid is used as a novel turbulence generator in a premixed turbulent flame stabilized by a rod. The study compares the flame behaviour with a fractal grid to the behaviour when a standard square mesh grid with the same effective mesh size and solidity as the fractal grid is used. The isothermal gas flow turbulence characteristics, including mean flow velocity and rms of velocity fluctuations and Taylor length, were evaluated from hot-wire measurements. The behaviour of the flames was assessed with direct chemiluminescence emission from the flame and high-speed OH-laser-induced fluorescence. The characteristics of the two flames are considered in terms of turbulent flame thickness, local flame curvature and turbulent flame speed. It is found that, for the same flow rate and stoichiometry and at the same distance downstream of the location of the grid, fractal-grid-generated turbulence leads to a more turbulent flame with enhanced burning rate and increased flame surface area. (paper)
Improving nuclear generating station response for electrical grid islanding
International Nuclear Information System (INIS)
Chou, Q.B.; Kundur, P.; Acchione, P.N.; Lautsch, B.
1989-01-01
This paper describes problems associated with the performance characteristics of nuclear generating stations which do not have their overall plant control design functions co-ordinated with the other grid controls. The paper presents some design changes to typical nuclear plant controls which result in a significant improvement in both the performance of the grid island and the chances of the nuclear units staying on-line following the disturbance. This paper focuses on four areas of the overall unit controls and turbine governor controls which could be modified to better co-ordinate the control functions of the nuclear units with the electrical grid. Some simulation results are presented to show the performance of a typical electrical grid island containing a nuclear unit with and without the changes
HypGrid2D. A 2-d mesh generator
Energy Technology Data Exchange (ETDEWEB)
Soerensen, N N
1998-03-01
The implementation of a hyperbolic mesh generation procedure, based on an equation for orthogonality and an equation for the cell face area is described. The method is fast, robust and gives meshes with good smoothness and orthogonality. The procedure is implemented in a program called HypGrid2D. The HypGrid2D program is capable of generating C-, O- and `H`-meshes for use in connection with the EllipSys2D Navier-Stokes solver. To illustrate the capabilities of the program, some test examples are shown. First a series of C-meshes are generated around a NACA-0012 airfoil. Secondly a series of O-meshes are generated around a NACA-65-418 airfoil. Finally `H`-meshes are generated over a Gaussian hill and a linear escarpment. (au)
DC micro-grid with distributed generation for rural electrification
Sarker, M.J.; Asare-Bediako, B.; Alipuria, B.; Slootweg, J.G.; Kling, W.L.
2012-01-01
This paper investigates the use of low voltage DC distribution network for rural electrification within an intelligent grid concept. The goal is to provide local communities in sparsely populated areas with electricity supply generated from renewable energy sources. Since these communities subsist
Conducting grids to stabilize MHD generator plasmas against ionization instabilities
International Nuclear Information System (INIS)
Veefkind, A.
1972-09-01
Ionization instabilities in MHD generators may be suppressed by the use of grids that short circuit the AC electric field component corresponding to the direction of maximum growth. An analysis of the influence of the corresponding boundary conditions has been performed in order to obtain more quantitative information about the stabilizing effect of this system
Integrating Renewable Generation into Grid Operations: Four International Experiences
Energy Technology Data Exchange (ETDEWEB)
Weimar, Mark R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mylrea, Michael E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Levin, Todd [Argonne National Lab. (ANL), Argonne, IL (United States); Botterud, Audun [Argonne National Lab. (ANL), Argonne, IL (United States); O' Shaughnessy, Eric [National Renewable Energy Lab. (NREL), Golden, CO (United States); Bird, Lori [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2016-04-22
International experiences with power sector restructuring and the resultant impacts on bulk power grid operations and planning may provide insight into policy questions for the evolving United States power grid as resource mixes are changing in response to fuel prices, an aging generation fleet and to meet climate goals. Australia, Germany, Japan and the UK were selected to represent a range in the level and attributes of electricity industry liberalization in order to draw comparisons across a variety of regions in the United States such as California, ERCOT, the Southwest Power Pool and the Southeast Reliability Region. The study draws conclusions through a literature review of the four case study countries with regards to the changing resource mix and the electricity industry sector structure and their impact on grid operations and planning. This paper derives lessons learned and synthesizes implications for the United States based on answers to the above questions and the challenges faced by the four selected countries. Each country was examined to determine the challenges to their bulk power sector based on their changing resource mix, market structure, policies driving the changing resource mix, and policies driving restructuring. Each countries’ approach to solving those changes was examined, as well as how each country’s market structure either exacerbated or mitigated the approaches to solving the challenges to their bulk power grid operations and planning. All countries’ policies encourage renewable energy generation. One significant finding included the low- to zero-marginal cost of intermittent renewables and its potential negative impact on long-term resource adequacy. No dominant solution has emerged although a capacity market was introduced in the UK and is being contemplated in Japan. Germany has proposed the Energy Market 2.0 to encourage flexible generation investment. The grid operator in Australia proposed several approaches to maintaining
High-resolution subgrid models: background, grid generation, and implementation
Sehili, Aissa; Lang, Günther; Lippert, Christoph
2014-04-01
The basic idea of subgrid models is the use of available high-resolution bathymetric data at subgrid level in computations that are performed on relatively coarse grids allowing large time steps. For that purpose, an algorithm that correctly represents the precise mass balance in regions where wetting and drying occur was derived by Casulli (Int J Numer Method Fluids 60:391-408, 2009) and Casulli and Stelling (Int J Numer Method Fluids 67:441-449, 2010). Computational grid cells are permitted to be wet, partially wet, or dry, and no drying threshold is needed. Based on the subgrid technique, practical applications involving various scenarios were implemented including an operational forecast model for water level, salinity, and temperature of the Elbe Estuary in Germany. The grid generation procedure allows a detailed boundary fitting at subgrid level. The computational grid is made of flow-aligned quadrilaterals including few triangles where necessary. User-defined grid subdivision at subgrid level allows a correct representation of the volume up to measurement accuracy. Bottom friction requires a particular treatment. Based on the conveyance approach, an appropriate empirical correction was worked out. The aforementioned features make the subgrid technique very efficient, robust, and accurate. Comparison of predicted water levels with the comparatively highly resolved classical unstructured grid model shows very good agreement. The speedup in computational performance due to the use of the subgrid technique is about a factor of 20. A typical daily forecast can be carried out in less than 10 min on a standard PC-like hardware. The subgrid technique is therefore a promising framework to perform accurate temporal and spatial large-scale simulations of coastal and estuarine flow and transport processes at low computational cost.
Grid-Connected Distributed Generation: Compensation Mechanism Basics
Energy Technology Data Exchange (ETDEWEB)
Aznar, Alexandra Y [National Renewable Energy Laboratory (NREL), Golden, CO (United States);
2017-10-02
This short report defines compensation mechanisms for grid-connected, behind-the-meter distributed generation (DG) systems as instruments that comprise three core elements: (1) metering and billing arrangements, (2) sell rate design, and (3) retail rate design. This report describes metering and billing arrangements, with some limited discussion of sell rate design. We detail the three possible arrangements for metering and billing of DG: net energy metering (NEM); buy all, sell all; and net billing.
Impact of Converter Interfaced Generation and Load on Grid Performance
Ramasubramanian, Deepak
Alternate sources of energy such as wind, solar photovoltaic and fuel cells are coupled to the power grid with the help of solid state converters. Continued deregulation of the power sector coupled with favorable government incentives has resulted in the rapid growth of renewable energy sources connected to the distribution system at a voltage level of 34.5kV or below. Of late, many utilities are also investing in these alternate sources of energy with the point of interconnection with the power grid being at the transmission level. These converter interfaced generation along with their associated control have the ability to provide the advantage of fast control of frequency, voltage, active, and reactive power. However, their ability to provide stability in a large system is yet to be investigated in detail. This is the primary objective of this research. In the future, along with an increase in the percentage of converter interfaced renewable energy sources connected to the transmission network, there exists a possibility of even connecting synchronous machines to the grid through converters. Thus, all sources of energy can be expected to be coupled to the grid through converters. The control and operation of such a grid will be unlike anything that has been encountered till now. In this dissertation, the operation and behavior of such a grid will be investigated. The first step in such an analysis will be to build an accurate and simple mathematical model to represent the corresponding components in commercial software. Once this bridge has been crossed, conventional machines will be replaced with their solid state interfaced counterparts in a phased manner. At each stage, attention will be devoted to the control of these sources and also on the stability performance of the large power system. This dissertation addresses various concerns regarding the control and operation of a futuristic power grid. In addition, this dissertation also aims to address the issue
Wang, F.; Duarte, J.L.; Hendrix, M.A.M.
2010-01-01
Distributed power generation systems are expected to deliver active power into the grid and support it without interruption during unbalanced grid faults. Aiming to provide grid-interfacing inverters the flexibility to adapt to the coming change of grid requirements, an optimised active power
On the integration of wind generators on weak grids and island grids
International Nuclear Information System (INIS)
Laverdure, N.
2005-12-01
Wind energy is now an energy that can not be ignored. Because of intrinsic characteristics (scattered primary energy, generators with different technologies, use of power electronics interface), wind energy system integration in distribution grids leads to real problems in terms of impacts. With recent standard changes, it is necessary to study the possibilities of each technology of wind turbines to answer or not to these new constraints. This PhD thesis focuses on a comparison of the main present wind turbines concerning three points of discussion: energy quality, fault ride through, ancillary services (voltage and frequency). It insists on the possibilities in terms of control laws for variable speed wind turbines. (author)
DEFF Research Database (Denmark)
Rodriguez, Pedro; Luna, Alvaro; Hermoso, Juan Ramon
2011-01-01
The operation of distributed power generation systems under grid fault conditions is a key issue for the massive integration of renewable energy systems. Several studies have been conducted to improve the response of such distributed generation systems under voltage dips. In spite of being less s...
An Analysis of Elliptic Grid Generation Techniques Using an Implicit Euler Solver.
1986-06-09
at M. =0.90 and a=00 is when interpolating for the radius of curvature obtained. One expects the computed shock strength (r), a second examination is...solver to yield accurate second-order, ... v.s zd solutions. References Snn, .:-P.. Flr.e ’rference Methods In Z, .tational Fluid DinamIcs , to he published
Arkani-Hamed, J.; Seyed-Mahmoud, B.; Aldridge, K. D.; Baker, R. E.
2008-06-01
We propose a causal relationship between the creation of the giant impact basins on Mars by a large asteroid, ruptured when it entered the Roche limit, and the excitation of the Martian core dynamo. Our laboratory experiments indicate that the elliptical instability of the Martian core can be excited if the asteroid continually exerts tidal forces on Mars for ~20,000 years. Our numerical experiments suggest that the growth-time of the instability was 5,000-15,000 years when the asteroid was at a distance of 50,000-75,000 km. We demonstrate the stability of the orbital motion of an asteroid captured by Mars at a distance of 100,000 km in the presence of the Sun and Jupiter. We also present our results for the tidal interaction of the asteroid with Mars. An asteroid captured by Mars in prograde fashion can survive and excite the elliptical instability of the core for only a few million years, whereas a captured retrograde asteroid can excite the elliptical instability for hundreds of millions of years before colliding with Mars. The rate at which tidal energy dissipates in Mars during this period is over two orders of magnitude greater than the rate at which magnetic energy dissipates. If only 1% of the tidal energy dissipation is partitioned to the core, sufficient energy would be available to maintain the core dynamo. Accordingly, a retrograde asteroid is quite capable of exciting an elliptical instability in the Martian core, thus providing a candidate process to drive a core dynamo.
Emissions & Generation Resource Integrated Database (eGRID), eGRID2002 (with years 1996 - 2000 data)
U.S. Environmental Protection Agency — The Emissions emissions rates; net generation; resource mix; and many other attributes. eGRID2002 (years 1996 through 2000 data) contains 16 Excel spreadsheets and...
Schwarz-Christoffel Conformal Mapping based Grid Generation for Global Oceanic Circulation Models
Xu, Shiming
2015-04-01
We propose new grid generation algorithms for global ocean general circulation models (OGCMs). Contrary to conventional, analytical forms based dipolar or tripolar grids, the new algorithm are based on Schwarz-Christoffel (SC) conformal mapping with prescribed boundary information. While dealing with the conventional grid design problem of pole relocation, it also addresses more advanced issues of computational efficiency and the new requirements on OGCM grids arisen from the recent trend of high-resolution and multi-scale modeling. The proposed grid generation algorithm could potentially achieve the alignment of grid lines to coastlines, enhanced spatial resolution in coastal regions, and easier computational load balance. Since the generated grids are still orthogonal curvilinear, they can be readily 10 utilized in existing Bryan-Cox-Semtner type ocean models. The proposed methodology can also be applied to the grid generation task for regional ocean modeling when complex land-ocean distribution is present.
Electric Grid Expansion Planning with High Levels of Variable Generation
Energy Technology Data Exchange (ETDEWEB)
Hadley, Stanton W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); You, Shutang [Univ. of Tennessee, Knoxville, TN (United States); Shankar, Mallikarjun [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Liu, Yilu [Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-02-01
Renewables are taking a large proportion of generation capacity in U.S. power grids. As their randomness has increasing influence on power system operation, it is necessary to consider their impact on system expansion planning. To this end, this project studies the generation and transmission expansion co-optimization problem of the US Eastern Interconnection (EI) power grid with a high wind power penetration rate. In this project, the generation and transmission expansion problem for the EI system is modeled as a mixed-integer programming (MIP) problem. This study analyzed a time series creation method to capture the diversity of load and wind power across balancing regions in the EI system. The obtained time series can be easily introduced into the MIP co-optimization problem and then solved robustly through available MIP solvers. Simulation results show that the proposed time series generation method and the expansion co-optimization model and can improve the expansion result significantly after considering the diversity of wind and load across EI regions. The improved expansion plan that combines generation and transmission will aid system planners and policy makers to maximize the social welfare. This study shows that modelling load and wind variations and diversities across balancing regions will produce significantly different expansion result compared with former studies. For example, if wind is modeled in more details (by increasing the number of wind output levels) so that more wind blocks are considered in expansion planning, transmission expansion will be larger and the expansion timing will be earlier. Regarding generation expansion, more wind scenarios will slightly reduce wind generation expansion in the EI system and increase the expansion of other generation such as gas. Also, adopting detailed wind scenarios will reveal that it may be uneconomic to expand transmission networks for transmitting a large amount of wind power through a long distance
International Nuclear Information System (INIS)
Le, Anh-Thu; Lin, C. D.; Lucchese, R. R.
2010-01-01
We present theoretical calculations for polarization and ellipticity of high-order harmonics from aligned N 2 , CO 2 , and O 2 molecules generated by linearly polarized lasers. Within the rescattering model, the two polarization amplitudes of the harmonics are determined by the photo-recombination amplitudes for photons emitted with polarization parallel or perpendicular to the direction of the same returning electron wave packet. Our results show clear species-dependent polarization states, in excellent agreement with experiments. We further note that the measured polarization ellipse of the harmonic furnishes the needed parameters for a 'complete' experiment in molecules.
Rating Requirements of the UPQC to Integrate the FSIG Type Wind Generation to the Grid
Jayanti, N.; Basu, Malabika; Conlon, Michael; Gaughan, Kevin
2009-01-01
The ability of wind generation to remain connected to the grid in the event of system faults and dynamic reactive power compensation are two aspects of grid integration, which have received particular attention. The wind driven, fixed-speed induction generator (FSIG) on its own fails to fulfil these requirements of grid integration. The application of a unified power quality conditioner (UPQC) to overcome the grid integration problems of the FSIG is investigated. The role of the UPQC in enhan...
International Nuclear Information System (INIS)
Kamel, Rashad M.
2014-01-01
Highlights: • This paper evaluated the effects of different wind system types on fault performance of Micro-Grid. • Both standalone and grid connected modes are considered. • The MG earthing system configuration is taken in consideration. - Abstract: Recently, there are three wind generation (WG) system types. The first type is called Fixed Speed Wind Generation (FSWG) system, which employs squirrel cage induction generators. Double Fed Induction Generator (DFIG) is utilized in the second type. The third type is called Full Converter Wind Generation (FCWG) system, which is interfaced with Micro-Grid (MG) through a back to back converter. During fault occurrence, each WG has its performance and characteristics which are determined by the generator physical characteristics and the MG earthing system configuration. For some WG types, the fault current depends also on the control algorithm of the power converter. The main target of this paper is to investigate and estimate how the fault performance of MG during both standalone and grid-connected modes is influenced by the type of WG. It is found during standalone mode that the type of the employed WG has a dominant impact on the MG performance under fault disturbance. On the contrary, the type of the employed WG has a negligible effect on the MG fault performance during grid-connected mode. This is because the main grid contributes most of the fault current. Effects of earthing system type on MG performance are highlighted
Direct numerical simulation of turbulent mixing in grid-generated turbulence
International Nuclear Information System (INIS)
Nagata, Kouji; Suzuki, Hiroki; Sakai, Yasuhiko; Kubo, Takashi; Hayase, Toshiyuki
2008-01-01
Turbulent mixing of passive scalar (heat) in grid-generated turbulence (GGT) is simulated by means of direct numerical simulation (DNS). A turbulence-generating grid, on which the velocity components are set to zero, is located downstream of the channel entrance, and it is numerically constructed on the staggered mesh arrangement using the immersed boundary method. The grid types constructed are: (a) square-mesh biplane grid, (b) square-mesh single-plane grid, (c) composite grid consisting of parallel square-bars and (d) fractal grid. Two fluids with different temperatures are provided separately in the upper and lower streams upstream of the turbulence-generating grids, generating the thermal mixing layer behind the grids. For the grid (a), simulations for two different Prandtl numbers of 0.71 and 7.1, corresponding to air and water flows, are conducted to investigate the effect of the Prandtl number. The results show that the typical grid turbulence and shearless mixing layer are generated downstream of the grids. The results of the scalar field show that a typical thermal mixing layer is generated as well, and the effects of the Prandtl numbers on turbulent heat transfer are observed.
Direct numerical simulation of turbulent mixing in grid-generated turbulence
Energy Technology Data Exchange (ETDEWEB)
Nagata, Kouji; Suzuki, Hiroki; Sakai, Yasuhiko; Kubo, Takashi [Department of Mechanical Science and Engineering, Nagoya University, Nagoya 464-8603 (Japan); Hayase, Toshiyuki [Institute of Fluid Science, Tohoku University, Sendai 980-8577 (Japan)], E-mail: nagata@nagoya-u.jp, E-mail: hsuzuki@nagoya-u.jp, E-mail: ysakai@mech.nagoya-u.ac.jp, E-mail: t-kubo@nagoya-u.jp, E-mail: hayase@ifs.tohoku.ac.jp
2008-12-15
Turbulent mixing of passive scalar (heat) in grid-generated turbulence (GGT) is simulated by means of direct numerical simulation (DNS). A turbulence-generating grid, on which the velocity components are set to zero, is located downstream of the channel entrance, and it is numerically constructed on the staggered mesh arrangement using the immersed boundary method. The grid types constructed are: (a) square-mesh biplane grid, (b) square-mesh single-plane grid, (c) composite grid consisting of parallel square-bars and (d) fractal grid. Two fluids with different temperatures are provided separately in the upper and lower streams upstream of the turbulence-generating grids, generating the thermal mixing layer behind the grids. For the grid (a), simulations for two different Prandtl numbers of 0.71 and 7.1, corresponding to air and water flows, are conducted to investigate the effect of the Prandtl number. The results show that the typical grid turbulence and shearless mixing layer are generated downstream of the grids. The results of the scalar field show that a typical thermal mixing layer is generated as well, and the effects of the Prandtl numbers on turbulent heat transfer are observed.
Application of a non-contiguous grid generation method to complex configurations
International Nuclear Information System (INIS)
Chen, S.; McIlwain, S.; Khalid, M.
2003-01-01
An economical non-contiguous grid generation method was developed to efficiently generate structured grids for complex 3D problems. Compared with traditional contiguous grids, this new approach generated grids for different block clusters independently and was able to distribute the grid points more economically according to the user's specific topology design. The method was evaluated by applying it to a Navier-Stokes computation of flow past a hypersonic projectile. Both the flow velocity and the heat transfer characteristics of the projectile agreed qualitatively with other numerical data in the literature and with available field data. Detailed grid topology designs for 3D geometries were addressed, and the advantages of this approach were analysed and compared with traditional contiguous grid generation methods. (author)
Economic aspects of grid connected solar electricity generation
International Nuclear Information System (INIS)
Pharabod, F.
1993-01-01
Experience gained with available solar thermal technologies enlighten on options for research and development on solar electricity generation. The proposed analysis of new solar technologies concerns market, costs and profit viewpoint: - Systems under development have to fit with consumers' needs and utilities' specifications, technology is not the only item to study. - Expense headings depend on technological options and operation procedures such as size of the plant, solar only or hybrid concept. - Anticipation of revenues highly depends on direct insolation quality and on local conditions for introducing the electric power generated into the network: daily direct insolation measurements and annual local load curve are prerequisite data. Strategic advantages regarding environment and sustainable development are to be pointed out, specially in industrialized countries or for projects including financing institutions. As far as generating electric power on the grid is a major challenge in the development of a number of countries in the sun belt, cooperation between industrialized and developing countries, under the auspices of international organization, has to be promoted. (Author) 12 refs
Comparison of control strategies for Doubly fed induction generator under recurring grid faults
DEFF Research Database (Denmark)
Chen, Wenjie; Blaabjerg, Frede; Zhu, Nan
2014-01-01
The new grid codes demand the wind turbine systems to ride through recurring grid faults. Many control strategies have been proposed for the Doubly Fed Induction Generator under single grid fault, but their performance under recurring grid faults have not been studied yet. In this paper, five...... different control strategies for DFIG to ride through single grid faults are presented, and their performance under recurring grid faults are analyzed. The controllable range, stator time constant and torque fluctuations of the DFIG with different control strategies are compared. The results are verified...
Doubly fed induction generator based wind turbine systems subject to recurring grid faults
DEFF Research Database (Denmark)
Chen, Wenjie; Blaabjerg, Frede; Zhu, Nan
2014-01-01
New grid codes demand the wind turbine systems to ride through recurring grid faults. In this paper, the performance of the Doubly Fed Induction Generator wind turbine system under recurring grid faults is analyzed. The stator natural flux produced by the voltage recovery after the first grid fault...... may be superposed on the stator natural flux produced by the second grid fault, and it may result in large current and voltage transient. The damping of the stator natural flux can be accelerated with a rotor natural current in its opposite direction after voltage recovery, but larger torque....... The performance of DFIG under recurring grid faults is verified by the simulation and experiments....
Three-Phase Grid-Connected of Photovoltaic Generator Using Nonlinear Control
DEFF Research Database (Denmark)
Yahya, A.; El Fadil, H.; Guerrero, Josep M.
2014-01-01
This paper proposes a nonlinear control methodology for three phase grid connected of PV generator. It consists of a PV arrays; a voltage source inverter, a grid filter and an electric grid. The controller objectives are threefold: i) ensuring the Maximum power point tracking (MPPT) in the side...... stability analysis and simulation results that the proposed controller meets all the objectives....
High Order Sliding Mode Control of Doubly-fed Induction Generator under Unbalanced Grid Faults
DEFF Research Database (Denmark)
Zhu, Rongwu; Chen, Zhe; Wu, Xiaojie
2013-01-01
This paper deals with a doubly-fed induction generator-based (DFIG) wind turbine system under grid fault conditions such as: unbalanced grid voltage, three-phase grid fault, using a high order sliding mode control (SMC). A second order sliding mode controller, which is robust with respect...
Doubly Fed Induction Generator Wind Turbine Systems Subject to Recurring Symmetrical Grid Faults
DEFF Research Database (Denmark)
Chen, Wenjie; Blaabjerg, Frede; Zhu, Nan
2016-01-01
New grid codes demand the wind turbine systems to ride through recurring grid faults. In this paper, the performance of the doubly Ffed induction generator (DFIG) wind turbine system under recurring symmetrical grid faults is analyzed. The mathematical model of the DFIG under recurring symmetrical...... grid faults is established. The analysis is based on the DFIG wind turbine system with the typical low-voltage ride-through strategy-with rotor-side crowbar. The stator natural flux produced by the voltage recovery after the first grid fault may be superposed on the stator natural flux produced...... by the second grid fault, so that the transient rotor and stator current and torque fluctuations under the second grid fault may be influenced by the characteristic of the first grid fault, including the voltage dips level and the grid fault angle, as well as the duration between two faults. The mathematical...
Efficient identification of opportunities for Distributed Generation based on Smart Grid Technology
DEFF Research Database (Denmark)
Mutule, Anna; Obushevs, Artjoms; Lvov, Aleksandr
2013-01-01
The paper presents the main goals and achievements of the Smart Grids ERA-NET project named “Efficient identification of opportunities for Distributed Generation based on Smart Grid Technology (SmartGen)” during the second stage of project implementation. A description of Smart Grid Technology (S......) models developed within the framework of the project is given. The performed study cases where the SGT-models were implemented to analyze the impact of the electrical grid are discussed....
Energy Technology Data Exchange (ETDEWEB)
Deister, F.; Hirschel, E.H. [Univ. Stuttgart, IAG, Stuttgart (Germany); Waymel, F.; Monnoyer, F. [Univ. de Valenciennes, LME, Valenciennes (France)
2003-07-01
An automatic adaptive hybrid Cartesian grid generation and simulation system is presented together with applications. The primary computational grid is an octree Cartesian grid. A quasi-prismatic grid may be added for resolving the boundary layer region of viscous flow around the solid body. For external flow simulations the flow solver TAU from the ''deutsche zentrum fuer luft- und raumfahrt (DLR)'' is integrated in the simulation system. Coarse grids are generated automatically, which are required by the multilevel method. As an application to an internal problem the thermal and dynamic modeling of a subway station is presented. (orig.)
SPAGETTA: a Multi-Purpose Gridded Stochastic Weather Generator
Dubrovsky, M.; Huth, R.; Rotach, M. W.; Dabhi, H.
2017-12-01
SPAGETTA is a new multisite/gridded multivariate parametric stochastic weather generator (WG). Site-specific precipitation occurrence and amount are modelled by Markov chain and Gamma distribution, the non-precipitation variables are modelled by an autoregressive (AR) model conditioned on precipitation occurrence, and the spatial coherence of all variables is modelled following the Wilks' (2009) approach. SPAGETTA may be run in two modes. Mode 1: it is run as a classical WG, which is calibrated using weather series from multiple sites, and only then it may produce arbitrarily long synthetic series mimicking the spatial and temporal structure of the calibration data. To generate the weather series representing the future climate, the WG parameters are modified according to the climate change scenario, typically derived from GCM or RCM simulations. Mode 2: the user provides only basic information (not necessarily to be realistic) on the temporal and spatial auto-correlation structure of the weather variables and their mean annual cycle; the generator itself derives the parameters of the underlying AR model, which produces the multi-site weather series. Optionally, the user may add the spatially varying trend, which is superimposed to the synthetic series. The contribution consists of following parts: (a) Model of the WG. (b) Validation of WG in terms of the spatial temperature and precipitation characteristics, including characteristics of spatial hot/cold/dry/wet spells. (c) Results of the climate change impact experiment, in which the WG parameters representing the spatial and temporal variability are modified using the climate change scenarios and the effect on the above spatial validation indices is analysed. In this experiment, the WG is calibrated using the E-OBS gridded daily weather data for several European regions, and the climate change scenarios are derived from the selected RCM simulations (CORDEX database). (d) The second mode of operation will be
WinGridder - An interactive grid generator for TOUGH - A user's manual (Version 1.0)
International Nuclear Information System (INIS)
Pan, Lehua; Hinds, Jennifer; Haukwa, Charles; Wu, Yu-Shu; Bodvarsson, Gudmundur
2001-01-01
WinGridder is a Windows-based software package for designing, generating, and visualizing at various spatial scales numerical grids used in reservoir simulations and groundwater modeling studies. Development of this software was motivated by the requirements of the TOUGH (Transport of Unsaturated Groundwater and Heat) family of codes (Pruess 1987, 1991) for simulating subsurface processes related to high-level nuclear waste isolation in partially saturated geological media. Although the TOUGH family of codes has great flexibility in handling the variety of grid information required to describe complex objects, designing and generating a suitable irregular grid can be a tedious and error-prone process, even with the help of existing grid generating programs. This is especially true when the number of cells and connections is very large. The processes of inspecting the quality of the grid or extracting sub-grids or other specific grid information are also complex. The mesh maker embedded within TOUGH2 generates only uniform numerical grids and handles only one set of uniform fracture and matrix properties throughout the model domain. This is not suitable for grid generation in complex flow and transport simulations (such as those of Yucca Mountain, which have heterogeneity in both fracture and matrix media). As a result, the software program Amesh (Haukwa 2000) was developed to generate irregular, effective-continuum (ECM) grids
Cheng, Zheming; Eiseman, Peter R.
1995-01-01
With examples, we illustrate how implicitly specified surfaces can be used for grid generation with GridPro/az3000. The particular examples address two questions: (1) How do you model intersecting tubes with fillets? and (2) How do you generate grids inside the intersected tubes? The implication is much more general. With the results in a forthcoming paper which develops an easy-to-follow procedure for implicit surface modeling, we provide a powerful means for rapid prototyping in grid generation.
Job system generation in grid taking into account user preferences
Directory of Open Access Journals (Sweden)
D. M. Yemelyanov
2016-01-01
Full Text Available Distributed computing environments like Grid are characterized by heterogeneity, low cohesion and dynamic structure of computing nodes. This is why the task of resource scheduling in such environments is complex. Different approaches to job scheduling in grid exist. Some of them use economic principles. Economic approaches to scheduling have shown their efficiency. One of such approaches is cyclic scheduling scheme which is considered in this paper.Cyclic scheduling scheme takes into account the preferences of computing environment users by means of an optimization criterion, which is included in the resource request. Besides, the scheme works cyclically by scheduling a certain job batch at each scheduling step. This is why there is a preliminary scheduling step which is job batch generation.The purpose of this study was to estimate the infl uence of job batch structure by the user criterion on the degree of its satisfaction. In other words we had to find the best way to form the batch with relation to the user optimization criterion. For example if it is more efficient to form the batch with jobs with the same criterion value or with different criterion values. Also we wanted to find the combination of criterion values which would give the most efficient scheduling results.To achieve this purpose an experiment in a simulation environment was conducted. The experiment consisted of scheduling of job batches with different values of the user criterion, other parameters of the resource request and the characteristics of the computing environment being the same. Three job batch generation strategies were considered. In the first strategy the batch consisted of jobs with the same criterion value. In the second strategy the batch consisted of jobs with all the considered criteria equally likely. The third strategy was similar to the second one, but only two certain criteria were considered. The third strategy was considered in order to find the most
Directory of Open Access Journals (Sweden)
Bernhard Faessler
2017-12-01
Full Text Available Due to the promoted integration of renewable sources, a further growth of strongly transient, distributed generation is expected. Thus, the existing electrical grid may reach its physical limits. To counteract this, and to fully exploit the viable potential of renewables, grid-balancing measures are crucial. In this work, battery storage systems are embedded in a grid simulation to evaluate their potential for grid balancing. The overall setup is based on a real, low-voltage distribution grid topology, real smart meter household load profiles, and real photovoltaics load data. An autonomous optimization routine, driven by a one-way communicated incentive, determines the prospective battery operation mode. Different battery positions and incentives are compared to evaluate their impact. The configurations incorporate a baseline simulation without storage, a single, central battery storage or multiple, distributed battery storages which together have the same power and capacity. The incentives address either market conditions, grid balancing, optimal photovoltaic utilization, load shifting, or self-consumption. Simulations show that grid-balancing incentives result in lowest peak-to-average power ratios, while maintaining negligible voltage changes in comparison to a reference case. Incentives reflecting market conditions for electricity generation, such as real-time pricing, negatively influence the power quality, especially with respect to the peak-to-average power ratio. A central, feed-in-tied storage performs better in terms of minimizing the voltage drop/rise and shows lower distribution losses, while distributed storages attached at nodes with electricity generation by photovoltaics achieve lower peak-to-average power ratios.
Adaptive grid generation in a patient-specific cerebral aneurysm
Hodis, Simona; Kallmes, David F.; Dragomir-Daescu, Dan
2013-11-01
Adapting grid density to flow behavior provides the advantage of increasing solution accuracy while decreasing the number of grid elements in the simulation domain, therefore reducing the computational time. One method for grid adaptation requires successive refinement of grid density based on observed solution behavior until the numerical errors between successive grids are negligible. However, such an approach is time consuming and it is often neglected by the researchers. We present a technique to calculate the grid size distribution of an adaptive grid for computational fluid dynamics (CFD) simulations in a complex cerebral aneurysm geometry based on the kinematic curvature and torsion calculated from the velocity field. The relationship between the kinematic characteristics of the flow and the element size of the adaptive grid leads to a mathematical equation to calculate the grid size in different regions of the flow. The adaptive grid density is obtained such that it captures the more complex details of the flow with locally smaller grid size, while less complex flow characteristics are calculated on locally larger grid size. The current study shows that kinematic curvature and torsion calculated from the velocity field in a cerebral aneurysm can be used to find the locations of complex flow where the computational grid needs to be refined in order to obtain an accurate solution. We found that the complexity of the flow can be adequately described by velocity and vorticity and the angle between the two vectors. For example, inside the aneurysm bleb, at the bifurcation, and at the major arterial turns the element size in the lumen needs to be less than 10% of the artery radius, while at the boundary layer, the element size should be smaller than 1% of the artery radius, for accurate results within a 0.5% relative approximation error. This technique of quantifying flow complexity and adaptive remeshing has the potential to improve results accuracy and reduce
Online Detection and Estimation of Grid Impedance Variation for Distributed Power Generation
DEFF Research Database (Denmark)
Jebali-Ben Ghorbal, Manel; Ghzaiel, Walid; Slama-Belkhodja, Ilhem
2012-01-01
A better knowledge of the grid impedance is essential in order to improve power quality and control of the Distributed Power Generation Systems (DPGS) and also for a safe connection or reconnection to the utility grid. An LCL-filter associated to a Voltage Source Inverter (VSI) is usually used...... to disconnect the DPG systems of the network. This work presents a rapid and simple technique to detect the grid impedance variation and to determine the grid impedance before and after grid faults accurs. Implementation on FPGA control board, simulations and experimental results are presented to validate...
Generating Free-Form Grid Truss Structures from 3D Scanned Point Clouds
Directory of Open Access Journals (Sweden)
Hui Ding
2017-01-01
Full Text Available Reconstruction, according to physical shape, is a novel way to generate free-form grid truss structures. 3D scanning is an effective means of acquiring physical form information and it generates dense point clouds on surfaces of objects. However, generating grid truss structures from point clouds is still a challenge. Based on the advancing front technique (AFT which is widely used in Finite Element Method (FEM, a scheme for generating grid truss structures from 3D scanned point clouds is proposed in this paper. Based on the characteristics of point cloud data, the search box is adopted to reduce the search space in grid generating. A front advancing procedure suit for point clouds is established. Delaunay method and Laplacian method are used to improve the quality of the generated grids, and an adjustment strategy that locates grid nodes at appointed places is proposed. Several examples of generating grid truss structures from 3D scanned point clouds of seashells are carried out to verify the proposed scheme. Physical models of the grid truss structures generated in the examples are manufactured by 3D print, which solidifies the feasibility of the scheme.
Modelling grid losses and the geographic distribution of electricity generation
DEFF Research Database (Denmark)
Østergaard, Poul Alberg
2005-01-01
In Denmark more than 40% of the electricity consumption is covered by geographically scattered electricity sources namely wind power and local CHP (cogeneration of heat and power) plants. This causes problems in regard to load balancing and possible grid overloads. The potential grid problems...... and methods for solving these are analysed in this article on the basis of energy systems analyses, geographic distribution of consumption and production and grid load-flow analyses. It is concluded that by introducing scattered load balancing using local CHP plants actively and using interruptible loads...
Integration of renewable generation and elastic loads into distribution grids
Ardakanian, Omid; Rosenberg, Catherine
2016-01-01
This brief examines the challenges of integrating distributed energy resources and high-power elastic loads into low-voltage distribution grids, as well as the potential for pervasive measurement. It explores the control needed to address these challenges and achieve various system-level and user-level objectives. A mathematical framework is presented for the joint control of active end-nodes at scale, and extensive numerical simulations demonstrate that proper control of active end-nodes can significantly enhance reliable and economical operation of the power grid.
A brief overview of the distribution test grids with a distributed generation inclusion case study
Directory of Open Access Journals (Sweden)
Stanisavljević Aleksandar M.
2018-01-01
Full Text Available The paper presents an overview of the electric distribution test grids issued by different technical institutions. They are used for testing different scenarios in operation of a grid for research, benchmarking, comparison and other purposes. Their types, main characteristics, features as well as application possibilities are shown. Recently, these grids are modified with inclusion of distributed generation. An example of modification and application of the IEEE 13-bus for testing effects of faults in cases without and with a distributed generator connection to the grid is presented. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 042004: Smart Electricity Distribution Grids Based on Distribution Management System and Distributed Generation
Program EAGLE User’s Manual. Volume 3. Grid Generation Code
1988-09-01
15 1. ompps.te Grid Structure ..... .. .................. . 15 2. Block Interfaces ......... ...................... . 18 3. Fundmental ...in principle it is possible to establish a correspondence between any physical region and a single empty rectangular block for general three...differences. Since this second surrounding layer is not involved in the grid generation, no further account will be taken of its presence in the present
Control strategies for gas turbine generators for grid connected and islanding operations
DEFF Research Database (Denmark)
Mahat, Pukar; Chen, Zhe; Bak-Jensen, Birgitte
2010-01-01
fine while a DG is connected to a grid, might not work as desired while it is islanded and vise versa. This paper presents a strategy to operate distribution systems with a small gas turbine generator (GTG), which is capable of supplying local loads, in both islanding and grid connected conditions...
Enhanced Local Grid Voltage Support Method for High Penetration of Distributed Generators
DEFF Research Database (Denmark)
Demirok, Erhan; Sera, Dezso; Rodriguez, Pedro
2011-01-01
Grid voltage rise and thermal loading of network components are the most remarkable barriers to allow high number of distributed generator (DG) connections on the medium voltage (MV) and low voltage (LV) electricity networks. The other barriers such as grid power quality (harmonics, voltage...
Generating Realistic Dynamic Prices and Services for the Smart Grid
Pagani, G. A.; Aiello, M.
2014-01-01
The smart grid promises to change the way people manage their energy needs, to facilitate the inclusion of small-scale renewable sources, and to open the energy market to all. One of the enabling instruments is the real-time pricing of energy at the retail level: dynamic and flexible tariffs will
Digital control of grid connected converters for distributed power generation
Energy Technology Data Exchange (ETDEWEB)
Skjellnes, Tore
2008-07-01
Pulse width modulated converters are becoming increasingly popular as their cost decreases and power rating increases. The new trend of small scale power producers, often using renewable energy sources, has created new demands for delivery of energy to the grid. A major advantage of the pulse width modulated converter is the ability to control the output voltage at any point in the voltage period. This enables rapid response to load changes and non-linear loads. In addition it can shape the voltage in response to the output current to create an outward appearance of a source impedance. This is called a virtual impedance. This thesis presents a controller for a voltage controlled three phase pulse width modulated converter. This controller enables operation in standalone mode, in parallel with other converters in a micro grid, and in parallel with a strong main grid. A time varying virtual impedance is presented which mainly attenuates reactive currents. A method of investigating the overall impedance including the virtual impedance is presented. New net standards have been introduced, requiring the converter to operate even during severe dips in the grid voltage. Experiments are presented verifying the operation of the controller during voltage dips. (Author). 37 refs., 65 figs., 10 tabs
A two-dimensional adaptive numerical grids generation method and its realization
International Nuclear Information System (INIS)
Xu Tao; Shui Hongshou
1998-12-01
A two-dimensional adaptive numerical grids generation method and its particular realization is discussed. This method is effective and easy to realize if the control functions are given continuously, and the grids for some regions is showed in this case. For Computational Fluid Dynamics, because the control values of adaptive grids-numerical solution is given in dispersed form, it is needed to interpolate these values to get the continuous control functions. These interpolation techniques are discussed, and some efficient adaptive grids are given. A two-dimensional fluid dynamics example was also given
Improved numerical grid generation techniques for the B2 edge plasma code
International Nuclear Information System (INIS)
Stotler, D.P.; Coster, D.P.
1992-06-01
Techniques used to generate grids for edge fluid codes such as B2 from numerically computed equilibria are discussed. Fully orthogonal, numerically derived grids closely resembling analytically prescribed meshes can be obtained. But, the details of the poloidal field can vary, yielding significantly different plasma parameters in the simulations. The magnitude of these differences is consistent with the predictions of an analytic model of the scrape-off layer. Both numerical and analytic grids are insensitive to changes in their defining parameters. Methods for implementing nonorthogonal boundaries in these meshes are also presented; they differ slightly from those required for fully orthogonal grids
Computational Needs for the Next Generation Electric Grid Proceedings
Energy Technology Data Exchange (ETDEWEB)
Birman, Kenneth; Ganesh, Lakshmi; Renessee, Robbert van; Ferris, Michael; Hofmann, Andreas; Williams, Brian; Sztipanovits, Janos; Hemingway, Graham; University, Vanderbilt; Bose, Anjan; Stivastava, Anurag; Grijalva, Santiago; Grijalva, Santiago; Ryan, Sarah M.; McCalley, James D.; Woodruff, David L.; Xiong, Jinjun; Acar, Emrah; Agrawal, Bhavna; Conn, Andrew R.; Ditlow, Gary; Feldmann, Peter; Finkler, Ulrich; Gaucher, Brian; Gupta, Anshul; Heng, Fook-Luen; Kalagnanam, Jayant R; Koc, Ali; Kung, David; Phan, Dung; Singhee, Amith; Smith, Basil
2011-10-05
The April 2011 DOE workshop, 'Computational Needs for the Next Generation Electric Grid', was the culmination of a year-long process to bring together some of the Nation's leading researchers and experts to identify computational challenges associated with the operation and planning of the electric power system. The attached papers provide a journey into these experts' insights, highlighting a class of mathematical and computational problems relevant for potential power systems research. While each paper defines a specific problem area, there were several recurrent themes. First, the breadth and depth of power system data has expanded tremendously over the past decade. This provides the potential for new control approaches and operator tools that can enhance system efficiencies and improve reliability. However, the large volume of data poses its own challenges, and could benefit from application of advances in computer networking and architecture, as well as data base structures. Second, the computational complexity of the underlying system problems is growing. Transmitting electricity from clean, domestic energy resources in remote regions to urban consumers, for example, requires broader, regional planning over multi-decade time horizons. Yet, it may also mean operational focus on local solutions and shorter timescales, as reactive power and system dynamics (including fast switching and controls) play an increasingly critical role in achieving stability and ultimately reliability. The expected growth in reliance on variable renewable sources of electricity generation places an exclamation point on both of these observations, and highlights the need for new focus in areas such as stochastic optimization to accommodate the increased uncertainty that is occurring in both planning and operations. Application of research advances in algorithms (especially related to optimization techniques and uncertainty quantification) could accelerate power
Development and Evaluation of a Methodology for the Generation of Gridded Isotopic Datasets
Energy Technology Data Exchange (ETDEWEB)
Argiriou, A. A.; Salamalikis, V [University of Patras, Department of Physics, Laboratory of Atmospheric Physics, Patras (Greece); Lykoudis, S. P. [National Observatory of Athens, Institute of Environmental and Sustainable Development, Athens (Greece)
2013-07-15
The accurate knowledge of the spatial distribution of stable isotopes in precipitation is necessary for several applications. Since the number of rain sampling stations is small and unevenly distributed around the globe, the global distribution of stable isotopes can be calculated via the generation of gridded isotopic data sets. Several methods have been proposed for this purpose. In this work a methodology is proposed for the development of 10'x 10' gridded isotopic data from precipitation in the central and eastern Mediterranean. Statistical models are developed taking into account geographical and meteorological parameters as regressors. The residuals are interpolated onto the grid using ordinary kriging and thin plate splines. The result is added to the model grids, to obtain the final isotopic gridded data sets. Models are evaluated using an independent data set. the overall performance of the procedure is satisfactory and the obtained gridded data reproduce the isotopic parameters successfully. (author)
Development and Evaluation of a Methodology for the Generation of Gridded Isotopic Datasets
International Nuclear Information System (INIS)
Argiriou, A.A.; Salamalikis, V; Lykoudis, S.P.
2013-01-01
The accurate knowledge of the spatial distribution of stable isotopes in precipitation is necessary for several applications. Since the number of rain sampling stations is small and unevenly distributed around the globe, the global distribution of stable isotopes can be calculated via the generation of gridded isotopic data sets. Several methods have been proposed for this purpose. In this work a methodology is proposed for the development of 10'x 10' gridded isotopic data from precipitation in the central and eastern Mediterranean. Statistical models are developed taking into account geographical and meteorological parameters as regressors. The residuals are interpolated onto the grid using ordinary kriging and thin plate splines. The result is added to the model grids, to obtain the final isotopic gridded data sets. Models are evaluated using an independent data set. the overall performance of the procedure is satisfactory and the obtained gridded data reproduce the isotopic parameters successfully. (author)
Energy Technology Data Exchange (ETDEWEB)
Larsson, Aake; Larsson, Richard [Vattenfall Power Consultants, Stockholm (Sweden)
2006-12-15
Grid connections of large power generating units normally require more detailed studies compared to small single units. The required R and D-level depends on the specific characteristics of the production units and the connecting grid. An inquiry for a grid connection will raise questions for the grid owner regarding transmission capability, losses, fault currents, relay protection, dynamic stability etc. Then only a few larger wind farms have been built, the experiences from these types of grid connections are limited and for that reason it can be difficult to identify issues appropriate for further studies. To ensure that electric power generating units do not have unacceptable impact on the grid, directions from the Swedish TSO (Svenska Kraftnaet) have been stated. The directions deal, for example, with power generation in specific ranges of voltage level and frequency and the possibility to remain connected to the grid when different faults occur. The requirements and the consequences of these directions are illustrated. There are three main issues that should be considered: Influence on the power flow from generating units regarding voltage level, currents, losses etc.; Different types of electric systems in generating units contribute to different levels of fault currents. For that reason the resulting fault current levels have to be studied; It is required that generating units should remain connected to the grid at different modes of operation and faults. These modes have to be verified. Load flow and dynamic studies normally demand computer models. Comprehensive models, for instance of wind farms, can bee difficult to design and normally large computer capacity is required. Therefore simplified methods to perform relevant studies are described. How to model an electric power generating unit regarding fault currents and dynamic stability is described. An inquiry for a grid connection normally brings about a discussion concerning administration. To make it
Bornemeier, Matthew; Luznik, Luksa
2017-11-01
High resolution, two dimensional PIV measurements of grid-generated turbulence in the US Naval Academy's recirculating water tunnel (1.8m test section with 0.41m x 0.41m cross sectional area) are presented for two different grid designs. The first grid is a uniform square bar grid with mesh width, M =3.9cm, bar thickness t0 = 1cm, a streamwise thickness of 1cm and resulting solidity of 44%, similar to the conventional grid used by Krogstad and Davidson (2012). The other is Mazellier & Vassilicos' (2010) square fractal grid, SFG17, with fractal iteration count, N =4, thickness ratio tr = 17 and length ratio Lr = 8. Grid patterns differ from the published designs by a circular hole with 4.30cm diameter in the middle that will accept, in future experiments, a shaft connected to an axisymmetric rotating wake generator with diameter, D. Grids were designed to generate turbulence of specific integral length scale of O(D) and intensity of 6% at the prescribed downstream location. Mean tunnel centerline velocity is 2 m/s and measurements are made in a streamwise vertical center plane with nominal individual field of view (FOV) of 12x8 cm2. Spatial coverage in the test section is accomplished by ``tiling'' individual FOV with approximately 2cm overlap. Results will focus on characterizing resulting turbulence in the test section and discussion will include comparison between published results and the present measurements.
Application of Load Compensation in Voltage Controllers of Large Generators in the Polish Power Grid
Directory of Open Access Journals (Sweden)
Bogdan Sobczak
2014-03-01
Full Text Available The Automatic Voltage Regulator normally controls the generator stator terminal voltage. Load compensation is used to control the voltage which is representative of the voltage at a point either within or external to the generator. In the Polish Power Grid (PPG compensation is ready to use in every AVR of a large generator, but it is utilized only in the case of generators operating at the same medium voltage buses. It is similar as in most European Power Grids. The compensator regulating the voltage at a point beyond the machine terminals has significant advantages in comparison to the slower secondary Voltage and Reactive Power Control System (ARNE1. The compensation stiffens the EHV grid, which leads to improved voltage quality in the distribution grid. This effect may be particularly important in the context of the dynamic development of wind and solar energy.
Intelligent voltage control in a DC micro-grid containing PV generation and energy storage
Rouzbehi, Kumars; Miranian, Arash; Candela García, José Ignacio; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro
2014-01-01
This paper proposes an intelligent control scheme for DC voltage regulationin a DC micro-grid integrating photovoltaic (PV) generation, energy storage and electric loads. The maximum power generation of the PV panel is followed using the incremental conductance (IC) maximum power point tracking (MPPT) algorithm while a high-performance local linear controller (LLC)is developed for the DC voltage control in the micro-grid.The LLC, as a data-driven control strategy, controls the bidirectional c...
Use of thermoelectric generators for improve power dependability over grid power
Energy Technology Data Exchange (ETDEWEB)
Archer, Jack [Global Thermoelectric, Calgary (Canada)
2005-07-01
A natural gas transportation company was experiencing extensive pipeline corrosion on some sections of their pipeline protected by impressed current using grid power and rectifiers. After determining that grid power was being interrupted on the affected sections, the gas transporter began looking for a more dependable power supply and chose thermoelectric generators. Since installing thermoelectric generators in 2002, the pipeline potentials have stabilized and transporter was able to experience 100% operational time on affected sections. (author)
Online Optimization Method for Operation of Generators in a Micro Grid
Hayashi, Yasuhiro; Miyamoto, Hideki; Matsuki, Junya; Iizuka, Toshio; Azuma, Hitoshi
Recently a lot of studies and developments about distributed generator such as photovoltaic generation system, wind turbine generation system and fuel cell have been performed under the background of the global environment issues and deregulation of the electricity market, and the technique of these distributed generators have progressed. Especially, micro grid which consists of several distributed generators, loads and storage battery is expected as one of the new operation system of distributed generator. However, since precipitous load fluctuation occurs in micro grid for the reason of its smaller capacity compared with conventional power system, high-accuracy load forecasting and control scheme to balance of supply and demand are needed. Namely, it is necessary to improve the precision of operation in micro grid by observing load fluctuation and correcting start-stop schedule and output of generators online. But it is not easy to determine the operation schedule of each generator in short time, because the problem to determine start-up, shut-down and output of each generator in micro grid is a mixed integer programming problem. In this paper, the authors propose an online optimization method for the optimal operation schedule of generators in micro grid. The proposed method is based on enumeration method and particle swarm optimization (PSO). In the proposed method, after picking up all unit commitment patterns of each generators satisfied with minimum up time and minimum down time constraint by using enumeration method, optimal schedule and output of generators are determined under the other operational constraints by using PSO. Numerical simulation is carried out for a micro grid model with five generators and photovoltaic generation system in order to examine the validity of the proposed method.
Garcia-Botella, Angel; Fernandez-Balbuena, Antonio Alvarez; Bernabeu, Eusebio
2006-10-10
Nonimaging optics is a field devoted to the design of optical components for applications such as solar concentration or illumination. In this field, many different techniques have been used to produce optical devices, including the use of reflective and refractive components or inverse engineering techniques. However, many of these optical components are based on translational symmetries, rotational symmetries, or free-form surfaces. We study a new family of nonimaging concentrators called elliptical concentrators. This new family of concentrators provides new capabilities and can have different configurations, either homofocal or nonhomofocal. Translational and rotational concentrators can be considered as particular cases of elliptical concentrators.
Research on a New Control Scheme of Photovoltaic Grid Power Generation System
Directory of Open Access Journals (Sweden)
Dong-Hui Li
2014-01-01
Full Text Available A new type of photovoltaic grid power generation system control scheme to solve the problems of the conventional photovoltaic grid power generation systems is presented. To aim at the oscillation and misjudgment of traditional perturbation observation method, an improved perturbation observation method comparing to the next moment power is proposed, combining with BOOST step-up circuit to realize the maximum power tracking. To counter the harmonic pollution problem in photovoltaic grid power generation system, the deadbeat control scheme in fundamental wave synchronous frequency rotating coordinate system of power grid is presented. A parameter optimization scheme based on positive feedback of active frequency shift island detection to solve the problems like the nondetection zone due to the import of disturbance in traditional island detection method is proposed. Finally, the results in simulation environment by MATLAB/Simulink simulation and experiment environment verify the validity and superiority of the proposed scheme.
Nuclear Power as an Option in Electrical Generation Planning for Small Economy and Electricity Grid
International Nuclear Information System (INIS)
Tomsic, Z.
2012-01-01
Implementing a NPP in countries with relatively small total GDP (small economy) and usually with small electricity grid face two major problems and constrains: the ability to obtain the considerable financial resources required on reasonable terms and to connect large NPP to small electricity grid. Nuclear generation financing in developing countries involves complex issues that need to be fully understood and dealt with by all the parties involved. The main topics covered by paper will be the: special circumstances related to the financing of NPP, costs and economic feasibility of NPP, conventional approaches for financing power generation projects in developing countries, alternative approaches for mobilizing financial resources. The safe and economic operation of a nuclear power plant (NPP) requires the plant to be connected to an electrical grid system that has adequate capacity for exporting the power from the NPP, and for providing a reliable electrical supply to the NPP for safe start-up, operation and normal or emergency shut-down of the plant. Connection of any large new power plant to the electrical grid system in a country may require significant modification and strengthening of the grid system, but for NPPs there may be added requirements to the structure of the grid system and the way it is controlled and maintained to ensure adequate reliability. Paper shows the comparative assesment of differrent base load technologies as an option in electrical generation planning for small economy and electricity grid.(author).
Mixing in 3D Sparse Multi-Scale Grid Generated Turbulence
Usama, Syed; Kopec, Jacek; Tellez, Jackson; Kwiatkowski, Kamil; Redondo, Jose; Malik, Nadeem
2017-04-01
Flat 2D fractal grids are known to alter turbulence characteristics downstream of the grid as compared to the regular grids with the same blockage ratio and the same mass inflow rates [1]. This has excited interest in the turbulence community for possible exploitation for enhanced mixing and related applications. Recently, a new 3D multi-scale grid design has been proposed [2] such that each generation of length scale of turbulence grid elements is held in its own frame, the overall effect is a 3D co-planar arrangement of grid elements. This produces a 'sparse' grid system whereby each generation of grid elements produces a turbulent wake pattern that interacts with the other wake patterns downstream. A critical motivation here is that the effective blockage ratio in the 3D Sparse Grid Turbulence (3DSGT) design is significantly lower than in the flat 2D counterpart - typically the blockage ratio could be reduced from say 20% in 2D down to 4% in the 3DSGT. If this idea can be realized in practice, it could potentially greatly enhance the efficiency of turbulent mixing and transfer processes clearly having many possible applications. Work has begun on the 3DSGT experimentally using Surface Flow Image Velocimetry (SFIV) [3] at the European facility in the Max Planck Institute for Dynamics and Self-Organization located in Gottingen, Germany and also at the Technical University of Catalonia (UPC) in Spain, and numerically using Direct Numerical Simulation (DNS) at King Fahd University of Petroleum & Minerals (KFUPM) in Saudi Arabia and in University of Warsaw in Poland. DNS is the most useful method to compare the experimental results with, and we are studying different types of codes such as Imcompact3d, and OpenFoam. Many variables will eventually be investigated for optimal mixing conditions. For example, the number of scale generations, the spacing between frames, the size ratio of grid elements, inflow conditions, etc. We will report upon the first set of findings
DEFF Research Database (Denmark)
Hansen, Anca Daniela; Michalke, G.
2009-01-01
Emphasis in this paper is on the fault ride-through and grid support capabilities of multi-pole permanent magnet synchronous generator (PMSG) wind turbines with a full-scale frequency converter. These wind turbines are announced to be very attractive, especially for large offshore wind farms...... and discussed by means of simulations with the use of a transmission power system generic model developed and delivered by the Danish Transmission System Operator Energinet.dk. The simulation results show how a PMSG wind farm equipped with an additional voltage control can help a nearby active stall wind farm....... A control strategy is presented, which enhances the fault ride-through and voltage support capability of such wind turbines during grid faults. Its design has special focus on power converters' protection and voltage control aspects. The performance of the presented control strategy is assessed...
Control of Doubly-Fed Induction Generator to Ride-Through Recurring Grid Faults
DEFF Research Database (Denmark)
Chen, Wenjie; Xu, Dehong; Zhu, Nan
2016-01-01
The wind turbine system (WTS) is required to ride-through recurring grid faults by the new grid codes. Under single grid faults, the fault ride-through (FRT) strategy with rotor-side crowbar is normally used for the doubly-fed induction generator (DFIG) WTS. However, under recurring faults, larger...... transient current and voltage may be produced, and the DFIG may fail to ride-through the second fault even with the rotor-side crowbar. The crowbar can be active again during the voltage recovery, but large electromagnetic torque (EM-torque) fluctuations will be introduced. The reliability of the mechanical...... system will be influenced. In this paper, an FRT strategy for the DFIG WTS to ride-through recurring symmetrical grid faults is investigated. An improved control strategy is introduced and it is applied during the voltage recovery of the grid faults. The decay of the stator natural flux can...
International Nuclear Information System (INIS)
Howlader, Harun Or Rashid; Matayoshi, Hidehito; Senjyu, Tomonobu
2015-01-01
Highlights: • Optimal operation of the thermal generation for the smart grid system. • Different distributed generations are considered as the power generation sources. • Forecast error of the renewable energy systems is considered. • Controllable loads of the smart houses are considered to achieve the optimal operation. • Economical benefits can be achieved for the smart grid system. - Abstract: This paper concentrates on the optimal operation of the conventional thermal generators with distributed generations for a smart grid considering forecast error. The distributed generations are considered as wind generators, photovoltaic generators, battery energy storage systems in the supply side and a large number of smart houses in the demand side. A smart house consists of the electric vehicle, heat pump, photovoltaic generator and solar collector. The electric vehicle and heat pump are considered as the controllable loads which can compensate the power for the forecast error of renewable energy sources. As a result, power generation cost of the smart grid can reduce through coordinated with distributed generations and thermal units scheduling process. The electric vehicles of the smart house are considered as the spinning reserve in the scheduling process which lead to lessen the additional operation of thermal units. Finally, obtained results of the proposed system have been compared with the conventional method. The conventional method does not consider the electric vehicle in the smart houses. The acquired results demonstrate that total power generation cost of the smart grid has been reduced by the proposed method considering forecast error. Effectiveness of the proposed method has been verified by the extensive simulation results using MATLAB® software
High flexible Hydropower Generation concepts for future grids
Hell, Johann
2017-04-01
The ongoing changes in electric power generation are resulting in new requirements for the classical generating units. In consequence a paradigm change in operation of power systems is necessary and a new approach in finding solutions is needed. The presented paper is dealing with the new requirements on current and future energy systems with the focus on hydro power generation. A power generation landscape for some European regions is shown and generation and operational flexibility is explained. Based on the requirements from the Transmission System Operator in UK, the transient performance of a Pumped Storage installation is discussed.
Surface Modeling, Grid Generation, and Related Issues in Computational Fluid Dynamic (CFD) Solutions
Choo, Yung K. (Compiler)
1995-01-01
The NASA Steering Committee for Surface Modeling and Grid Generation (SMAGG) sponsored a workshop on surface modeling, grid generation, and related issues in Computational Fluid Dynamics (CFD) solutions at Lewis Research Center, Cleveland, Ohio, May 9-11, 1995. The workshop provided a forum to identify industry needs, strengths, and weaknesses of the five grid technologies (patched structured, overset structured, Cartesian, unstructured, and hybrid), and to exchange thoughts about where each technology will be in 2 to 5 years. The workshop also provided opportunities for engineers and scientists to present new methods, approaches, and applications in SMAGG for CFD. This Conference Publication (CP) consists of papers on industry overview, NASA overview, five grid technologies, new methods/ approaches/applications, and software systems.
Characterization of a Power Electronic Grid Simulator for Wind Turbine Generator Compliance Testing
DEFF Research Database (Denmark)
Glasdam, Jakob Bærholm; Gevorgian, V.; Wallen, R.
2014-01-01
This paper presents the commissioning results and testing capabilities of a multi-megawatt power electronic grid simulator situated in National Renewable Energy Laboratory’s (NREL’s) new testing facility. The commissioning is done using a commercial type 4 multi-megawatt sized wind turbine...... generator (WTG) installed in NREL’s new 5 MW dynamometer and a kilowatt sized type 1 WTG connected to the existing 2.5 MW dynamometer at NREL. The paper demonstrates the outstanding testing capability of the grid simulator and its application in the grid code compliance evaluation of WTGs including balanced...
Interconnector capacity allocation in offshore grids with variable wind generation
DEFF Research Database (Denmark)
Schröder, Sascha Thorsten
2013-01-01
the interconnector capacity should be allocated for wind generation and for international power trading. The main difficulty arises from the stochastic nature of wind generation: in a case with radial connections to the national coast, the wind park owner has the possibility of aggregating the offshore wind park....... It is concluded that treating offshore generation as a single price zone within the interconnector reduces the wind operator’s ability to pool it with other generation. Furthermore, a single offshore price zone between two markets will always receive the lower spot market price of the neighbouring zones, although...
Directory of Open Access Journals (Sweden)
Shoaib Rauf
2017-01-01
Full Text Available Smart grid for the past few years has been the prime focus of research in power systems. The aim is to eliminate load shedding and problematic blackout conditions, further offering cheap and continuous supply of electricity for both large and small consumers. Another benefit is to integrate renewable energy resources with existing dump grid in more efficient and cost-effective manner. In past few years, growing demand for sustainable energy increases the consumption of solar PV. Since generation from solar PV is in DC and most of the appliances at home could be operated on DC, AC-DC hybrid distribution system with energy management system is proposed in this paper. EMS helps to shift or control the auxiliary load and compel the users to operate specific load at certain time slots. These techniques further help to manage the excessive load during peak and off peak hours. It demonstrates the practical implementation of DC-AC network with integration of solar PV and battery storage with existing infrastructure. The results show a remarkable improvement using hybrid AC-DC framework in terms of reliability and efficiency. All this functioning together enhances the overall efficiency; hence, a secure, economical, reliable, and intelligent system leads to a smart grid.
Solar photovoltaic systems and their use as grid-connected generators in the United Kingdom
Energy Technology Data Exchange (ETDEWEB)
Munro, D K; Hacker, R J; Thornycroft, J M [Halcrow Gilbert Associates Ltd., Swindon (United Kingdom)
1995-10-01
There is an increasing interest in the use of building-integrated solar photovoltaic generators as grid-connected generators. This paper discusses the experience with this technology in Europe. Typical systems and their integration into domestic and non-domestic buildings are described. Information is provided on the energy output that can be expected from the systems and the economics of their use. The paper provides an overview of the requirements for photovoltaic systems as grid-connected generation plant in the United Kingdom. (Author)
Impact of Rural Grid-Connected Photovoltaic Generation Systems on Power Quality
Directory of Open Access Journals (Sweden)
Rita Pinto
2016-09-01
Full Text Available Photovoltaic (PV generation systems have been increasingly used to generate electricity from renewable sources, attracting a growing interest. Recently, grid connected PV micro-generation facilities in individual homes have increased due to governmental policies as well as greater attention by industry. As low voltage (LV distribution systems were built to make energy flow in one direction, the power feed-in of PV generation in rural low-voltage grids can influence power quality (PQ as well as facility operation and reliability. This paper presents results on PQ analysis of a real PV generation facility connected to a rural low-voltage grid. Voltage fluctuations and voltage harmonic contents were observed. Statistical analysis shows a negative impact on PQ produced by this PV facility and also that only a small fraction of the energy available during a sunny day is converted, provoking losses of revenue and forcing the converter to work in an undesirable operating mode. We discuss the disturbances imposed upon the grid and their outcome regarding technical and economic viability of the PV system, as well as possible solutions. A low-voltage grid strengthening has been suggested and implemented. After that a new PQ analysis shows an improvement in the impact upon PQ, making this facility economically viable.
Statistics for PV, wind and biomass generators and their impact on distribution grid planning
Nykamp, Stefan; Molderink, Albert; Hurink, Johann L.; Smit, Gerardus Johannes Maria
2012-01-01
The integration of renewable energy generation leads to major challenges for distribution grid operators. When the feed-in of photovoltaic (PV), biomass and wind generators exceed significantly the local consumption, large investments are needed. To improve the knowledge on the interaction between
Control of power converters in distributed generation applications under grid fault conditions
DEFF Research Database (Denmark)
Rodriguez, Pedro; Luna, Alvaro; Munoz-Aguilar, Raul
2011-01-01
The operation of distributed power generation systems under grid fault conditions is a key issue for the massive integration of renewable energy systems. Several studies have been conducted to improve the response of such distributed generation systems under voltage dips. In spite of being less s...
On the use of Schwarz-Christoffel conformal mappings to the grid generation for global ocean models
Xu, S.; Wang, B.; Liu, J.
2015-10-01
In this article we propose two grid generation methods for global ocean general circulation models. Contrary to conventional dipolar or tripolar grids, the proposed methods are based on Schwarz-Christoffel conformal mappings that map areas with user-prescribed, irregular boundaries to those with regular boundaries (i.e., disks, slits, etc.). The first method aims at improving existing dipolar grids. Compared with existing grids, the sample grid achieves a better trade-off between the enlargement of the latitudinal-longitudinal portion and the overall smooth grid cell size transition. The second method addresses more modern and advanced grid design requirements arising from high-resolution and multi-scale ocean modeling. The generated grids could potentially achieve the alignment of grid lines to the large-scale coastlines, enhanced spatial resolution in coastal regions, and easier computational load balance. Since the grids are orthogonal curvilinear, they can be easily utilized by the majority of ocean general circulation models that are based on finite difference and require grid orthogonality. The proposed grid generation algorithms can also be applied to the grid generation for regional ocean modeling where complex land-sea distribution is present.
Directory of Open Access Journals (Sweden)
Malek Jasemi
2016-11-01
Full Text Available Nowadays, due to technical and economic reasons, the distributed generation (DG units are widely connected to the low and medium voltage network and created a new structure called micro-grid. Renewable energies (especially wind and solar based DGs are one of the most important generations units among DG units. Because of stochastic behavior of these resources, the optimum and safe management and operation of micro-grids has become one of the research priorities for researchers. So, in this study, the optimal operation of a typical micro-grid is investigated in order to maximize the penetration of renewable energy sources with the lowest operation cost with respect to the limitations for the load supply and the distributed generation resources. The understudy micro-grid consists of diesel generator, battery, wind turbines and photovoltaic panels. The objective function comprises of fuel cost, start-up cost, spinning reserve cost, power purchasing cost from the upstream grid and the sales revenue of the power to the upstream grid. In this paper, the uncertainties of demand, wind speed and solar radiation are considered and the optimization will be made by using the GAMS software and mixed integer planning method (MIP. Article History: Received May 21, 2016; Received in revised form July 11, 2016; Accepted October 15, 2016; Available online How to Cite This Article: Jasemi, M., Adabi, F., Mozafari, B., and Salahi, S. (2016 Optimal Operation of Micro-grids Considering the Uncertainties of Demand and Renewable Energy Resources Generation, Int. Journal of Renewable Energy Development, 5(3,233-248. http://dx.doi.org/10.14710/ijred.5.3.233-248
SmaggIce 2.0: Additional Capabilities for Interactive Grid Generation of Iced Airfoils
Kreeger, Richard E.; Baez, Marivell; Braun, Donald C.; Schilling, Herbert W.; Vickerman, Mary B.
2008-01-01
The Surface Modeling and Grid Generation for Iced Airfoils (SmaggIce) software toolkit has been extended to allow interactive grid generation for multi-element iced airfoils. The essential phases of an icing effects study include geometry preparation, block creation and grid generation. SmaggIce Version 2.0 now includes these main capabilities for both single and multi-element airfoils, plus an improved flow solver interface and a variety of additional tools to enhance the efficiency and accuracy of icing effects studies. An overview of these features is given, especially the new multi-element blocking strategy using the multiple wakes method. Examples are given which illustrate the capabilities of SmaggIce for conducting an icing effects study for both single and multi-element airfoils.
Grid-connected solar power generation a utility's view
International Nuclear Information System (INIS)
Weiner, D.; Meron, G.; Fisher, D.
1994-01-01
The purpose of this paper is to analyze these new means of production from the electric utility point of view. This analysis will take into account the experience gained by Israel Electric Corporation while operating three demonstration plants. In addition, a techno-economic evaluation photovoltaic and thermal systems is presented and compared to that of conventional generation
Kamhawi, Hilmi N.
2012-01-01
This report documents the work performed from March 2010 to March 2012. The Integrated Design and Engineering Analysis (IDEA) environment is a collaborative environment based on an object-oriented, multidisciplinary, distributed framework using the Adaptive Modeling Language (AML) as a framework and supporting the configuration design and parametric CFD grid generation. This report will focus on describing the work in the area of parametric CFD grid generation using novel concepts for defining the interaction between the mesh topology and the geometry in such a way as to separate the mesh topology from the geometric topology while maintaining the link between the mesh topology and the actual geometry.
Research on simulated devices for Solar photovoltaic grid-connected generation system
Directory of Open Access Journals (Sweden)
quan-zhu Zhang
2017-01-01
Full Text Available On the standpoint of energy conservation and emission reduction, one device simulated photovoltaic grid-connected generation system based on SPWM was designed in the paper. And DC/AC inverter could transduce efficiently direct current to alternating current. The MCU(Micro-Control-Unit, in this system could achieve the control method for maximum-power-point and tracking for frequency and phase. Moreover, the MCU could implement PWM (Plus-Width Modulating through programming. The system showed clearly the whole photovoltaic grid-connected generation system using simulated methods and ways.
Special issue on advancing grid-connected renewable generation systems
DEFF Research Database (Denmark)
Blaabjerg, Frede; Yang, Yongheng
2017-01-01
Renewables are heavily involved in power generation, as an essential component for today’s energy paradigm. Energy structure—both national and international—has been undergoing significant changes over the past few decades. For instance, in Denmark, power generation is shifting from fossil......-fuel-based to renewable-based in terms of energy sources, from centralized to decentralized in terms of architectures, and from sole to miscellaneous in terms of energy varieties [1]. In this energy evolution, the power electronic technology plays an enabling role in the integration and advancements of renewables......—such as wind turbine, photovoltaics, fuel cells, and other emerging energy systems. At the same time, various control strategies are necessary to guide the energy integration (i.e., to enhance the energy transition), and on the other hand, to flexibly, reliably, and efficiently utilize the energy. Tremendous...
Simulation of Photovoltaic generator Connected To a Grid
Directory of Open Access Journals (Sweden)
F. Slama
2014-03-01
Full Text Available This paper presents the mathematical and the total Matlab-simulink model of the various components, of the photovoltaic power station connected to a network, (PSCN, namely the model of the photovoltaic generator. It is a comprehensive behavioural study which performed according to varying conditions of solar insulation and temperature. The photovoltaic generator and the inverter of single-phase current are modeled. The former by using a mathematical model that gives the values of maximum power according to the variation of the weather conditions, and the latter by a source of voltage controlled by voltage in order to inject a sinusoidal current and to estimate or predict the energy injected monthly or annually into the network.
Mesh Generation via Local Bisection Refinement of Triangulated Grids
2015-06-01
Science and Technology Organisation DSTO–TR–3095 ABSTRACT This report provides a comprehensive implementation of an unstructured mesh generation method...and Technology Organisation 506 Lorimer St, Fishermans Bend, Victoria 3207, Australia Telephone: 1300 333 362 Facsimile: (03) 9626 7999 c© Commonwealth...their behaviour is critically linked to Maubach’s method and the data structures N and T . The top- level mesh refinement algorithm is also presented
Global Renewable Energy-Based Electricity Generation and Smart Grid System for Energy Security
Islam, M. A.; Hasanuzzaman, M.; Rahim, N. A.; Nahar, A.; Hosenuzzaman, M.
2014-01-01
Energy is an indispensable factor for the economic growth and development of a country. Energy consumption is rapidly increasing worldwide. To fulfill this energy demand, alternative energy sources and efficient utilization are being explored. Various sources of renewable energy and their efficient utilization are comprehensively reviewed and presented in this paper. Also the trend in research and development for the technological advancement of energy utilization and smart grid system for future energy security is presented. Results show that renewable energy resources are becoming more prevalent as more electricity generation becomes necessary and could provide half of the total energy demands by 2050. To satisfy the future energy demand, the smart grid system can be used as an efficient system for energy security. The smart grid also delivers significant environmental benefits by conservation and renewable generation integration. PMID:25243201
Global renewable energy-based electricity generation and smart grid system for energy security.
Islam, M A; Hasanuzzaman, M; Rahim, N A; Nahar, A; Hosenuzzaman, M
2014-01-01
Energy is an indispensable factor for the economic growth and development of a country. Energy consumption is rapidly increasing worldwide. To fulfill this energy demand, alternative energy sources and efficient utilization are being explored. Various sources of renewable energy and their efficient utilization are comprehensively reviewed and presented in this paper. Also the trend in research and development for the technological advancement of energy utilization and smart grid system for future energy security is presented. Results show that renewable energy resources are becoming more prevalent as more electricity generation becomes necessary and could provide half of the total energy demands by 2050. To satisfy the future energy demand, the smart grid system can be used as an efficient system for energy security. The smart grid also delivers significant environmental benefits by conservation and renewable generation integration.
Global Renewable Energy-Based Electricity Generation and Smart Grid System for Energy Security
Directory of Open Access Journals (Sweden)
M. A. Islam
2014-01-01
Full Text Available Energy is an indispensable factor for the economic growth and development of a country. Energy consumption is rapidly increasing worldwide. To fulfill this energy demand, alternative energy sources and efficient utilization are being explored. Various sources of renewable energy and their efficient utilization are comprehensively reviewed and presented in this paper. Also the trend in research and development for the technological advancement of energy utilization and smart grid system for future energy security is presented. Results show that renewable energy resources are becoming more prevalent as more electricity generation becomes necessary and could provide half of the total energy demands by 2050. To satisfy the future energy demand, the smart grid system can be used as an efficient system for energy security. The smart grid also delivers significant environmental benefits by conservation and renewable generation integration.
International Nuclear Information System (INIS)
Hughes, Larry; Bell, Jeff
2006-01-01
The increasing popularity of on-site power generation is driving the demand for methods to compensate customer-generators that supply electricity to the grid. Although many practices exist for providing such compensation, confusion surrounds the terms often used to describe such practices (notably, net metering and net billing). To help clarify this situation, the following paper proposes a taxonomy that distinguishes between 16 distinct compensation practices
Ferlemann, Paul G.; Gollan, Rowan J.
2010-01-01
Computational design and analysis of three-dimensional hypersonic inlets with shape transition has been a significant challenge due to the complex geometry and grid required for three-dimensional viscous flow calculations. Currently, the design process utilizes an inviscid design tool to produce initial inlet shapes by streamline tracing through an axisymmetric compression field. However, the shape is defined by a large number of points rather than a continuous surface and lacks important features such as blunt leading edges. Therefore, a design system has been developed to parametrically construct true CAD geometry and link the topology of a structured grid to the geometry. The Adaptive Modeling Language (AML) constitutes the underlying framework that is used to build the geometry and grid topology. Parameterization of the CAD geometry allows the inlet shapes produced by the inviscid design tool to be generated, but also allows a great deal of flexibility to modify the shape to account for three-dimensional viscous effects. By linking the grid topology to the parametric geometry, the GridPro grid generation software can be used efficiently to produce a smooth hexahedral multiblock grid. To demonstrate the new capability, a matrix of inlets were designed by varying four geometry parameters in the inviscid design tool. The goals of the initial design study were to explore inviscid design tool geometry variations with a three-dimensional analysis approach, demonstrate a solution rate which would enable the use of high-fidelity viscous three-dimensional CFD in future design efforts, process the results for important performance parameters, and perform a sample optimization.
SmartGrid: Future networks for New Zealand power systems incorporating distributed generation
International Nuclear Information System (INIS)
Nair, Nirmal-Kumar C.; Zhang Lixi
2009-01-01
The concept of intelligent electricity grids, which primarily involves the integration of new information and communication technologies with power transmission lines and distribution cables, is being actively explored in the European Union and the United States. Both developments share common technological developmental goals but also differ distinctly towards the role of distributed generation for their future electrical energy security. This paper looks at options that could find relevance to New Zealand (NZ), in the context of its aspiration of achieving 90% renewable energy electricity generation portfolio by 2025. It also identifies developments in technical standardization and industry investments that facilitate a pathway towards an intelligent or smart grid development for NZ. Some areas where policy can support research in NZ being a 'fast adapter' to future grid development are also listed. This paper will help policy makers quickly review developments surrounding SmartGrid and also identify its potential to support NZ Energy Strategy in the electricity infrastructure. This paper will also help researchers and power system stakeholders for identifying international standardization, projects and potential partners in the area of future grid technologies.
Energy Technology Data Exchange (ETDEWEB)
Safari, S.; Jazi, B., E-mail: jaziada@kashanu.ac.ir [Department of Laser and Photonics, Faculty of Physics, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of); Jahanbakht, S. [Department of Communications Engineering, Faculty of Electrical And Computer Engineering, University of Kashan, Kashan, Islamic Republic of Iran (Iran, Islamic Republic of)
2016-08-15
In this work, two stream instability in a metallic waveguide with elliptical cross-section and with a hollow annular dielectric layer is studied for generation and amplification of THz electromagnetic waves. Dispersion relation of waves and their dependents to geometric dimensions and characteristics of the electron beam are analyzed. In continuation, the diagrams of growth rate for some operating frequencies are presented, so that effective factors on the growth rates, such as geometrical dimensions, dielectric constant of dielectric layer, accelerating voltage, and applied current intensity are analyzed. It is shown that while an electron beam is responsible for instability, another electron beam plays a stabilizing role.
A testing procedure for wind turbine generators based on the power grid statistical model
DEFF Research Database (Denmark)
Farajzadehbibalan, Saber; Ramezani, Mohammad Hossein; Nielsen, Peter
2017-01-01
In this study, a comprehensive test procedure is developed to test wind turbine generators with a hardware-in-loop setup. The procedure employs the statistical model of the power grid considering the restrictions of the test facility and system dynamics. Given the model in the latent space...
DEFF Research Database (Denmark)
Petersen, Lennart; Iov, Florin
2017-01-01
This study focuses on distributed voltage control coordination between renewable generation plants in medium-voltage distribution grids (DGs). A distributed offline coordination concept has been defined in a previous publication, leading to satisfactory voltage regulation in the DG. However, here...
Grid-generated He II turbulence in a finite channel - experiment
International Nuclear Information System (INIS)
Niemela, J.J.; Skrbek, L.; Stalp, S.R.
2001-01-01
We present experimental data on decaying turbulence, generated by towing a grid through a stationary sample of He II. We describe in detail the experimental apparatus and physical principles that allow observation of up to six orders of magnitude of decaying vortex line density over three orders of magnitude in time using the second sound attenuation technique. (orig.)
Chaudhry, Hina
2013-01-01
This study is a part of the smart grid initiative providing electric vehicle charging infrastructure. It is a refueling structure, an energy generating photovoltaic system and charge point electric vehicle charging station. The system will utilize advanced design and technology allowing electricity to flow from the site's normal electric service…
Identification of Synchronous Generator Electric Parameters Connected to the Distribution Grid
Directory of Open Access Journals (Sweden)
Frolov M. Yu.
2017-04-01
Full Text Available According to modern trends, the power grids with distributed generation will have an open system architecture. It means that active consumers, owners of distributed power units, including mobile units, must have free access to the grid, like when using internet, so it is necessary to have plug and play technologies. Thanks to them, the system will be able to identify the unit type and the unit parameters. Therefore, the main aim of research, described in the paper, was to develop and research a new method of electric parameters identification of synchronous generator. The main feature of the proposed method is that parameter identification is performed while the generator to the grid, so it fits in the technological process of operation of the machine and does not influence on the connection time of the machine. For the implementation of the method, it is not necessary to create dangerous operation modes for the machine or to have additional expensive equipment and it can be used for salient pole machines and round rotor machines. The parameter identification accuracy can be achieved by more accurate account of electromechanical transient process, and making of overdetermined system with many more numbers of equations. Parameter identification will be made with each generator connection to the grid. Comparing data obtained from each connection, the middle values can be find by numerical method, and thus, each subsequent identification will accurate the machine parameters.
Online Energy Management System for Distributed Generators in a Grid-Connected Microgrid
DEFF Research Database (Denmark)
Hernández, Adriana Carolina Luna; Aldana, Nelson Leonardo Diaz; Graells, Moises
2015-01-01
A microgrid is an energy subsystem composed of generation units, energy storage, and loads that requires power management in order to supply the load properly according to defined objectives. This paper proposes an online energy management system for a storage based grid-connected microgrid...
Economic Power Dispatch of Distributed Generators in a Grid-Connected Microgrid
DEFF Research Database (Denmark)
Hernández, Adriana Carolina Luna; Aldana, Nelson Leonardo Diaz; Andrade, Fabio
2015-01-01
Grid-connected microgrids with storage systems are reliable configurations for critical loads which can not tolerate interruptions of energy supply. In such cases, some of the energy resources should be scheduled in order to coordinate optimally the power generation according to a defined objective...
Geometry Laboratory (GEOLAB) surface modeling and grid generation technology and services
Kerr, Patricia A.; Smith, Robert E.; Posenau, Mary-Anne K.
1995-01-01
The facilities and services of the GEOmetry LABoratory (GEOLAB) at the NASA Langley Research Center are described. Included in this description are the laboratory functions, the surface modeling and grid generation technologies used in the laboratory, and examples of the tasks performed in the laboratory.
Thermal Behavior of Doubly-Fed Induction Generator Wind Turbine System during Balanced Grid Fault
DEFF Research Database (Denmark)
Zhou, Dao; Blaabjerg, Frede; Lau, Mogens
2014-01-01
Ride-through capabilities of the doubly-fed induction generator (DFIG) during grid fault have been studied a lot. However, the thermal performance of the power device during this transient period is seldom investigated. In this paper, the dynamic model for the DFIG and the influence of the rotor...
A novel proposal of cooperation between a cage induction generator and the three-phase grid
Directory of Open Access Journals (Sweden)
Szular Zbigniew
2016-01-01
Full Text Available In the paper, a new concept of the cooperation between a cage induction generator and the three-phase grid is presented. The induction generator is excited by a capacitor battery connected to the stator winding terminals. In order to ensure a stable operation, the battery capacity should be continuously adjusted. Three appropriate selected capacitors are connected to the stator winding terminals by means of two bi-directional controlled switches. The generator output voltage is stabilized by a suitable control of these switches. The stator winding terminals are also connected to the diode bridge rectifier. Energy in the DC bus is converted to the parameters of the three-phase grid (400 V, 50 Hz by means of a three-phase voltage source inverter. Examples of numerical calculation results of the proposed energy generation system are presented in the end part of the paper.
Unbalanced voltage control of virtual synchronous generator in isolated micro-grid
Cao, Y. Z.; Wang, H. N.; Chen, B.
2017-06-01
Virtual synchronous generator (VSG) control is recommended to stabilize the voltage and frequency in isolated micro-grid. However, common VSG control is challenged by widely used unbalance loads, and the linked unbalance voltage problem worsens the power quality of the micro-grid. In this paper, the mathematical model of VSG was presented. Based on the analysis of positive- and negative-sequence equivalent circuit of VSG, an approach was proposed to eliminate the negative-sequence voltage of VSG with unbalance loads. Delay cancellation method and PI controller were utilized to identify and suppress the negative-sequence voltages. Simulation results verify the feasibility of proposed control strategy.
Decentralized electricity generation by using photovoltaic grid-connected solar system
International Nuclear Information System (INIS)
Tyutyundziev, N.; Vitanov, P.; Radkov, R.; Grottke, M.
2006-01-01
AcadPV is the first demonstration installation connected permanently to LV grid in Sofia, Bulgaria aiming at assessment of PV efficiencies and cost-effectiveness. A thorough analysis has been carried out in order to select PV system site, supporting construction design and orientation. The PV generator is divided to 3 PV subfields equipped by 3 SUNPOWER inverters connected to 3 separated phases of the grid. The performance of 10kWp PV system has been evaluated during the first year of operation and compared to PV simulation software results
User's manual for the HYPGEN hyperbolic grid generator and the HGUI graphical user interface
Chan, William M.; Chiu, Ing-Tsau; Buning, Pieter G.
1993-01-01
The HYPGEN program is used to generate a 3-D volume grid over a user-supplied single-block surface grid. This is accomplished by solving the 3-D hyperbolic grid generation equations consisting of two orthogonality relations and one cell volume constraint. In this user manual, the required input files and parameters and output files are described. Guidelines on how to select the input parameters are given. Illustrated examples are provided showing a variety of topologies and geometries that can be treated. HYPGEN can be used in stand-alone mode as a batch program or it can be called from within a graphical user interface HGUI that runs on Silicon Graphics workstations. This user manual provides a description of the menus, buttons, sliders, and typein fields in HGUI for users to enter the parameters needed to run HYPGEN. Instructions are given on how to configure the interface to allow HYPGEN to run either locally or on a faster remote machine through the use of shell scripts on UNIX operating systems. The volume grid generated is copied back to the local machine for visualization using a built-in hook to PLOT3D.
Energy Technology Data Exchange (ETDEWEB)
Tian, Tian; Chernyakhovskiy, Ilya; Brancucci Martinez-Anido, Carlo
2016-04-01
This document is the Spanish version of 'Greening the Grid- Forecasting Wind and Solar Generation Improving System Operations'. It discusses improving system operations with forecasting with and solar generation. By integrating variable renewable energy (VRE) forecasts into system operations, power system operators can anticipate up- and down-ramps in VRE generation in order to cost-effectively balance load and generation in intra-day and day-ahead scheduling. This leads to reduced fuel costs, improved system reliability, and maximum use of renewable resources.
Zhao, Yu; Shi, Chen-Xiao; Kwon, Ki-Chul; Piao, Yan-Ling; Piao, Mei-Lan; Kim, Nam
2018-03-01
We propose a fast calculation method for a computer-generated hologram (CGH) of real objects that uses a point cloud gridding method. The depth information of the scene is acquired using a depth camera and the point cloud model is reconstructed virtually. Because each point of the point cloud is distributed precisely to the exact coordinates of each layer, each point of the point cloud can be classified into grids according to its depth. A diffraction calculation is performed on the grids using a fast Fourier transform (FFT) to obtain a CGH. The computational complexity is reduced dramatically in comparison with conventional methods. The feasibility of the proposed method was confirmed by numerical and optical experiments.
Energy Technology Data Exchange (ETDEWEB)
Wolde-Ghiorgis, W. [Addis Ababa Univ., Addis Ababa (Ethiopia). Dept. of Electrical and Computer Engineering
2008-07-01
This presentation addressed issues and prospects that help resolve constraints facing wind energy development in developing countries, with particular reference to on grid-integrated, and possibly off-grid power generation. The limitations to wind energy-development include a lack of a sizable and interconnected grids and a lack of financing. As such, even if harnessable wind energy potential is discovered at conveniently located inland sites, producing electricity would still be a challenge. This is the situation faced by less developed countries such as Ethiopia where the population and energy demands are increasing. There are also additional constraints to be addressed, recognized and resolved. This paper demonstrated that the use of clean development mechanisms (CDM) could attract support from interested industrialized countries to initiate off-grid wind power generation schemes. Off-grid wind power generation is considered to be a viable option for CDM financing. Cost comparisons and operational safety favour off-grid wind power generation. 5 refs., 3 tabs.
Wang, F.; Duarte, J.L.; Hendrix, M.A.M.
2009-01-01
Distributed power generation is expected to deliver power into the grid without interruption during voltage dips. To improve system ride-through capabilities, a generalized active power control strategy is proposed for grid-interfacing inverters. Specifically, a current reference generation strategy
Energy Technology Data Exchange (ETDEWEB)
Gaztanaga Arantzamendi, H
2006-12-15
The present PhD deals with an original micro-grid concept and its application as a Renewable Energy Source's (RES) grid integration scheme. This micro-grid is composed of RES generators as well as support systems that incorporate additional functionalities in order to improve RES integration into the grid. According to this concept, two practical micro-grid applications have been studied in detail: a residential micro-grid and a wind farm supported by DFACTS systems (STATCOM and DVR). In both applications, the control structures which are implemented at different levels and applied to the different micro-grid elements have been developed, analyzed by means of off-line simulations and finally validated in real-time conditions with physical reduced-scale prototypes. (author)
Dynamic analysis of combined photovoltaic source and synchronous generator connected to power grid
Mahabal, Divya
In the world of expanding economy and technology, the energy demand is likely to increase even with the global efforts of saving and increasing energy efficiency. Higher oil prices, effects of greenhouse gases, and concerns over other environmental impacts gave way to Distributed Generation (DG). With adequate awareness and support, DG's can meet these rising energy demands at lower prices compared to conventional methods. Extensive research is taking place in different areas like fuel cells, photovoltaic cells, wind turbines, and gas turbines. DG's when connected to a grid increase the overall efficiency of the power grid. It is believed that three-fifth of the world's electricity would account for renewable energy by middle of 21st century. This thesis presents the dynamic analysis of a grid connected photovoltaic (PV) system and synchronous generator. A grid is considered as an infinite bus. The photovol-taic system and synchronous generator act as small scale distributed energy resources. The output of the photovoltaic system depends on the light intensity, temperature, and irradiance levels of sun. The maximum power point tracking and DC/AC converter are also modeled for the photovoltaic system. The PV system is connected to the grid through DC/AC system. Different combinations of PV and synchronous generator are modeled with the grid to study the dynamics of the proposed system. The dynamics of the test system is analyzed by subjecting the system to several disturbances under various conditions. All modules are individually modeled and con-nected using MATLAB/Simulink software package. Results from the study show that, as the penetration of renewable energy sources like PV increases into the power system, the dynamics of the system becomes faster. When considering cases such as load switching, PV cannot deliver more power as the performance of PV depends on environmental conditions. Synchronous generator in power system can produce the required amount of
Active and reactive power neurocontroller for grid-connected photovoltaic generation system
Directory of Open Access Journals (Sweden)
I. Abadlia
2016-03-01
Full Text Available Many researchers have contributed to the development of a firm foundation for analysis and design of control applications in grid-connected renewable energy sources. This paper presents an intelligent control algorithm fond on artificial neural networks for active and reactive power controller in grid-connected photovoltaic generation system. The system is devices into two parts in which each part contains an inverter with control algorithm. A DC/DC converter in output voltage established by control magnitude besides maximum power point tracker algorithm always finds optimal power of the PV array in use. A DC/AC hysteresis inverter designed can synchronize a sinusoidal current output with the grid voltage and accurate an independent active and reactive power control. Simulation results confirm the validation of the purpose. Neurocontroller based active and reactive power presents an efficiency control that guarantees good response to the steps changing in active and reactive power with an acceptable current/voltage synchronism. In this paper the power circuit and the control system of the presented grid-connected photovoltaic generation system is simulated and tested by MatLab/Simulink.
Directory of Open Access Journals (Sweden)
Yongli Wang
2018-03-01
Full Text Available With the application of distributed generation and the development of smart grid technology, micro-grid, an economic and stable power grid, tends to play an important role in the demand side management. Because micro-grid technology and demand response have been widely applied, what Demand Response actions can realize the economic operation of micro-grid has become an important issue for utilities. In this proposed work, operation optimization modeling for micro-grid is done considering distributed generation, environmental factors and demand response. The main contribution of this model is to optimize the cost in the context of considering demand response and system operation. The presented optimization model can reduce the operation cost of micro-grid without bringing discomfort to the users, thus increasing the consumption of clean energy effectively. Then, to solve this operational optimization problem, genetic algorithm is used to implement objective function and DR scheduling strategy. In addition, to validate the proposed model, it is employed on a smart micro-grid from Tianjin. The obtained numerical results clearly indicate the impact of demand response on economic operation of micro-grid and development of distributed generation. Besides, a sensitivity analysis on the natural gas price is implemented according to the situation of China, and the result shows that the natural gas price has a great influence on the operation cost of the micro-grid and effect of demand response.
Fair division of generation profile and fuel consumption in isolated micro-grids
DEFF Research Database (Denmark)
Kosek, Anna Magdalena; Heussen, Kai
2014-01-01
leads to more stressed loading conditions of diesel generators. We propose a control strategy employing fair division of generator allocation using a compensation procedure based on social choice methods. A co-simulation set up with separate power system and control strategy simulators is used...... to provide a proof-of-concept case study of an isolated micro-grid with two wind turbines and three diesel generators. In comparison with a simple master- slave allocation, the proposed coordination scheme improves the distribution of fuel allocation by 27,5%, reduces under-load time by 43,5% and decreases...
There is need in new generation smart grid for the space and ground energy systems
Directory of Open Access Journals (Sweden)
Ageev Alexander
2018-01-01
Full Text Available The aim of the article is to considerate the opportunities of synchronization of the space and ground systems that generate and transfer energy on the basis of new generation smart grid using. The authors substantiate the necessity of new intellectual monitoring services that assess the processes took place in "generation-transportation-distribution-consumption" space and ground systems. This is made in order to improve the dynamic indicators of the energy system and to avoid the emergencies. The authors also give a prognosis of the dynamic indicators of the electric power super-system in analyzing metastable conditions in different energy modes.
DEFF Research Database (Denmark)
Guo, Yougui; Zeng, Ping; Li, Lijuan
2010-01-01
Voltage oriented control PR is combined with space vector modulation and phase locked loop to control the grid side converter in wind power generation system in this paper. First the mathematical models of grid side converter and LCL filter as well as grid are given. Then the control strategy...... of grid side converter-based wind power generation system is given in detail. Finally the simulation model consisting of the grid side converter wind power generation system is set up. The simulation results have verified that the control strategy is feasible to be used for control of gird currents......, active power, reactive power and DC-link voltage in wind power generation system. It has laid a good basis for the real system development....
Alfieri, Luisa
2015-12-01
Power quality (PQ) disturbances are becoming an important issue in smart grids (SGs) due to the significant economic consequences that they can generate on sensible loads. However, SGs include several distributed energy resources (DERs) that can be interconnected to the grid with static converters, which lead to a reduction of the PQ levels. Among DERs, wind turbines and photovoltaic systems are expected to be used extensively due to the forecasted reduction in investment costs and other economic incentives. These systems can introduce significant time-varying voltage and current waveform distortions that require advanced spectral analysis methods to be used. This paper provides an application of advanced parametric methods for assessing waveform distortions in SGs with dispersed generation. In particular, the Standard International Electrotechnical Committee (IEC) method, some parametric methods (such as Prony and Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT)), and some hybrid methods are critically compared on the basis of their accuracy and the computational effort required.
Second-Generation High-Temperature Superconductor Wires for the Electric Power Grid
Malozemoff, A. P.
2012-08-01
Superconductors offer major advantages for the electric power grid, including high current and power capacity, high efficiency arising from the lossless current flow, and a unique current-limiting functionality arising from a superconductor-to-resistive transition. These advantages can be brought to bear on equipment such as underground power cables, fault current limiters, rotating machinery, transformers, and energy storage. The first round of significant commercial-scale superconductor power-equipment demonstrations, carried out during the past decade, relied on a first-generation high-temperature superconductor (HTS) wire. However, during the past few years, with the recent commercial availability of high-performance second-generation HTS wires, power-equipment demonstrations have increasingly been carried out with these new wires, which bring important advantages. The foundation is being laid for commercial expansion of this important technology into the power grid.
Wang, Kai; Zhang, Bu-han; Zhang, Zhe; Yin, Xiang-gen; Wang, Bo
2011-11-01
Most existing research on the vulnerability of power grids based on complex networks ignores the electrical characteristics and the capacity of generators and load. In this paper, the electrical betweenness is defined by considering the maximal demand of load and the capacity of generators in power grids. The loss of load, which reflects the ability of power grids to provide sufficient power to customers, is introduced to measure the vulnerability together with the size of the largest cluster. The simulation results of the IEEE-118 bus system and the Central China Power Grid show that the cumulative distributions of node electrical betweenness follow a power-law and that the nodes with high electrical betweenness play critical roles in both topological structure and power transmission of power grids. The results prove that the model proposed in this paper is effective for analyzing the vulnerability of power grids.
Hager, B. H.; Mazarico, E.; Touma, J.; Wisdom, J.
2003-12-01
Quantitative understanding of Earth's heat budget has eluded a list of distinguished physicists and geochemists ranging from Lord Kelvin to Don L Anderson. The global heat flux is substantially greater than that generated by the estimated inventory of radioactive heat sources, so simple energy balance considerations demand an additional heat source. Secular cooling is commonly invoked to balance Earth's energy budget, but the required cooling rates are difficult to reconcile with both traditional convection calculations and petrologic estimates of ancient upper mantle temperatures. A non-geochemical heat source seems plausible. Indeed, Tuoma and Wisdom (Astron. J., 122, 2001) showed that tidal dissipation of rotational energy associated with resonant coupling could provide a substantial heat pulse to the CMB. D'' Layer Activation (DLA) by dumping of rotational energy could have important geodynamical consequences that we explore here. DLA could lead to a sudden (but modest) increase in the temperature of preexisting plumes, leading to a sudden increase in melt volume without the need for a troublesome plume head. The dissipation depends on non-hydrostatic CMB ellipticity, which itself is a result of mantle convection, leading to the possibility of an important feedback mechanism - DLA would lead to an increase in CMB ellipticity, further increasing the geodynamic importance of DLA.
Daniel, Michael T.
Here in the early 21st century humanity is continuing to seek improved quality of life for citizens throughout the world. This global advancement is providing more people than ever with access to state-of-the-art services in areas such as transportation, entertainment, computing, communication, and so on. Providing these services to an ever-growing population while considering the constraints levied by continuing climate change will require new frontiers of clean energy to be developed. At the time of this writing, offshore wind has been proven as both a politically and economically agreeable source of clean, sustainable energy by northern European nations with many wind farms deployed in the North, Baltic, and Irish Seas. Modern offshore wind farms are equipped with an electrical system within the farm itself to aggregate the energy from all turbines in the farm before it is transmitted to shore. This collection grid is traditionally a 3-phase medium voltage alternating current (MVAC) system. Due to reactive power and other practical constraints, it is preferable to use a medium voltage direct current (MVDC) collection grid when siting farms >150 km from shore. To date, no offshore wind farm features an MVDC collection grid. However, MVDC collection grids are expected to be deployed with future offshore wind farms as they are sited further out to sea. In this work it is assumed that many future offshore wind farms may utilize an MVDC collection grid to aggregate electrical energy generated by individual wind turbines. As such, this work presents both per-phase and per-pole power electronic converter systems suitable for interfacing individual wind turbines to such an MVDC collection grid. Both interfaces are shown to provide high input power factor at the wind turbine while providing DC output current to the MVDC grid. Common mode voltage stress and circulating currents are investigated, and mitigation strategies are provided for both interfaces. A power sharing
Directory of Open Access Journals (Sweden)
Noroozian
2009-06-01
Full Text Available This paper presents the modeling and simulation of a proton exchange membrane fuel cell (PEMFC generation system for off-grid and on-grid operation and configuration. A fuel cell DG system consists of a fuel cell power plant, a DC/DC converter and a DC/AC inverter. The dynamic model for fuel cell array and its power electronic interfacing are presented also a multi-input single output (MISO DC/DC converter and its control scheme is proposed and analyzed. This DC/DC converter is capable of interfacing fuel cell arrays to the DC/AC inverter. Also the mathematical model of the inverter is obtained by using average technique. Then the novel control strategy of DC/AC inverter for different operating conditions is demonstrated. The simulation results show the effectiveness of the suggested control systems under both on-grid and off-grid operation modes.
A sparse grid based method for generative dimensionality reduction of high-dimensional data
Bohn, Bastian; Garcke, Jochen; Griebel, Michael
2016-03-01
Generative dimensionality reduction methods play an important role in machine learning applications because they construct an explicit mapping from a low-dimensional space to the high-dimensional data space. We discuss a general framework to describe generative dimensionality reduction methods, where the main focus lies on a regularized principal manifold learning variant. Since most generative dimensionality reduction algorithms exploit the representer theorem for reproducing kernel Hilbert spaces, their computational costs grow at least quadratically in the number n of data. Instead, we introduce a grid-based discretization approach which automatically scales just linearly in n. To circumvent the curse of dimensionality of full tensor product grids, we use the concept of sparse grids. Furthermore, in real-world applications, some embedding directions are usually more important than others and it is reasonable to refine the underlying discretization space only in these directions. To this end, we employ a dimension-adaptive algorithm which is based on the ANOVA (analysis of variance) decomposition of a function. In particular, the reconstruction error is used to measure the quality of an embedding. As an application, the study of large simulation data from an engineering application in the automotive industry (car crash simulation) is performed.
A three-dimensional algebraic grid generation scheme for gas turbine combustors with inclined slots
Yang, S. L.; Cline, M. C.; Chen, R.; Chang, Y. L.
1993-01-01
A 3D algebraic grid generation scheme is presented for generating the grid points inside gas turbine combustors with inclined slots. The scheme is based on the 2D transfinite interpolation method. Since the scheme is a 2D approach, it is very efficient and can easily be extended to gas turbine combustors with either dilution hole or slot configurations. To demonstrate the feasibility and the usefulness of the technique, a numerical study of the quick-quench/lean-combustion (QQ/LC) zones of a staged turbine combustor is given. Preliminary results illustrate some of the major features of the flow and temperature fields in the QQ/LC zones. Formation of co- and counter-rotating bulk flow and shape temperature fields can be observed clearly, and the resulting patterns are consistent with experimental observations typical of the confined slanted jet-in-cross flow. Numerical solutions show the method to be an efficient and reliable tool for generating computational grids for analyzing gas turbine combustors with slanted slots.
Liu, Xiaonan; Ma, Jialiang; Xu, Shiming; Wang, Bin
2017-08-01
Regional ocean models usually utilize orthogonal curvilinear grids that are fit to the coastline of the modeled regions. While the orthogonality of the grid is required from the perspective of the numerical algorithms, the alignment to the irregular coastlines improves the characterization of the land-sea distribution and the ocean simulation. In this article, we carry out fractal analysis of two representative coastal regions and discuss the trade-offs between the orthogonality and coastline alignment during the grid generation of these regions. A new grid generation method based on Schwarz-Christoffel conformal mappings is proposed, with automatic coastal boundary retrieval algorithm that generates resolution dependent boundary for grid generation and alleviates the human efforts involved in traditional methods. We show that for the southeastern Pacific region, the coastline is smooth with low fractal dimension and there exists effective trade-off with a coastline boundary that adjusts to the desired grid resolution. On the contrary, there is no effective trade-off for southeast China seas where the coastline is of higher fractal dimension, and a coarser coastline boundary is recommended for better orthogonality with little loss in coastline alignment. Further numerical study of coastal trapped Kelvin waves for the typical regions demonstrate that the new coastline-fitting grids achieve smaller error in numerical dispersion and higher accuracy. Through analysis, we conclude that for grid generation for regional ocean modeling, modelers should bring into consideration of the multi-scale fractal characteristics of the coastline.
Development of stable Grid service at the next generation system of KEKCC
Nakamura, T.; Iwai, G.; Matsunaga, H.; Murakami, K.; Sasaki, T.; Suzuki, S.; Takase, W.
2017-10-01
A lot of experiments in the field of accelerator based science are actively running at High Energy Accelerator Research Organization (KEK) by using SuperKEKB and J-PARC accelerator in Japan. In these days at KEK, the computing demand from the various experiments for the data processing, analysis, and MC simulation is monotonically increasing. It is not only for the case with high-energy experiments, the computing requirement from the hadron and neutrino experiments and some projects of astro-particle physics is also rapidly increasing due to the very high precision measurement. Under this situation, several projects, Belle II, T2K, ILC and KAGRA experiments supported by KEK are going to utilize Grid computing infrastructure as the main computing resource. The Grid system and services in KEK, which is already in production, are upgraded for the further stable operation at the same time of whole scale hardware replacement of KEK Central Computer System (KEKCC). The next generation system of KEKCC starts the operation from the beginning of September 2016. The basic Grid services e.g. BDII, VOMS, LFC, CREAM computing element and StoRM storage element are made by the more robust hardware configuration. Since the raw data transfer is one of the most important tasks for the KEKCC, two redundant GridFTP servers are adapted to the StoRM service instances with 40 Gbps network bandwidth on the LHCONE routing. These are dedicated to the Belle II raw data transfer to the other sites apart from the servers for the data transfer usage of the other VOs. Additionally, we prepare the redundant configuration for the database oriented services like LFC and AMGA by using LifeKeeper. The LFC servers are made by two read/write servers and two read-only servers for the Belle II experiment, and all of them have an individual database for the purpose of load balancing. The FTS3 service is newly deployed as a service for the Belle II data distribution. The service of CVMFS stratum-0 is
A Vertical-Axis Off-Grid Squirrel-Cage Induction Generator Wind Power System
Directory of Open Access Journals (Sweden)
Peifeng Xu
2016-10-01
Full Text Available In order to broaden the limited utilization range of wind power and improve the charging and discharging control performance of the storage battery in traditional small wind power generation systems, a wind power system based on a vertical-axis off-grid induction generator is proposed in this paper. The induction generator not only can run in a wide wind speed range but can also assist the vertical-axis wind turbine to realize self-starting at low wind speed. Combined with the maximum power point tracking method, the slip frequency control strategy is employed to regulate the pulse width modulation (PWM converter to control the output power of the proposed system when the wind speed and load change. The charge and discharge of the storage battery is realized by the segmented current-limiting control strategy by means of an electric power unloader device connected to the DC bus. All these implement a balanced and stable operation of the proposed power generation system. The experimental research on the 5.5 kW prototype system is developed, and the corresponding results verify the correctness and feasibility of the system design and control strategy. Some comparison experiments with a magnetic suspension permanent magnet synchronous generator (PMSG demonstrate the application prospect of the proposed vertical-axis off-grid induction generator wind power system.
DEFF Research Database (Denmark)
Zhou, Dao; Blaabjerg, Frede; Franke, Toke
2014-01-01
The modern grid requirement has caused that the wind power system behaves more like conventional rotating generators and it is able to support certain amount of the reactive power. For a typical doubly-fed induction generator wind turbine system, the reactive power can be supported either through...... for the generator and the wind power converter in terms of the reactive power done by the rotor-side converter or the grid-side converter with various grid filters. Afterwards, the annual energy loss is also estimated based on yearly wind profile. Finally, experimental results of the loss distribution are performed...... the rotor-side converter or the grid-side converter. This paper firstly compares the current ripples and supportive reactive power ranges between the conventional L and optimized LCL filter, if the reactive power is injected from the grid-side converter. Then, the loss distribution is evaluated both...
DEFF Research Database (Denmark)
Zhou, Dao; Blaabjerg, Frede; Franke, Toke
2015-01-01
The modern grid requirement has caused that the wind power system behaves more like conventional rotating generators, and it is able to support certain amount of the reactive power. For a typical doubly fed induction generator (DFIG) wind turbine system, the reactive power can be supported either...... for the generator and the wind power converter in terms of the reactive power done by the rotor-side converter or the grid-side converter with various grid filters. Afterward, the annual energy loss is also estimated based on yearly wind profile. Finally, experimental results of the loss distribution are performed...... through the rotor-side converter or the grid-side converter. This paper first compares the current ripples and supportive reactive power ranges between the conventional L and optimized LCL filter, if the reactive power is injected from the grid-side converter. Then, the loss distribution is evaluated both...
RMS Current of a Photovoltaic Generator in Grid-Connected PV Systems: Definition and Application
Directory of Open Access Journals (Sweden)
P. J. Pérez
2008-01-01
Full Text Available This paper includes a definition of a new and original concept in the photovoltaic field, RMS current of a photovoltaic generator for grid-connected systems. The RMS current is very useful for calculating energy losses in cables used in a PV generator. As well, a current factor has been defined in order to simplify RMS current calculation. This factor provides an immediate (quick and easy calculation method for the RMS current that does not depend on the case particular conditions (orientation, location, etc.. RMS current and current factor values have been calculated for different locations and modules.
Research on grid connection control technology of double fed wind generator
Ling, Li
2017-01-01
The composition and working principle of variable speed constant frequency doubly fed wind power generation system is discussed in this thesis. On the basis of theoretical analysis and control on the modeling, the doubly fed wind power generation simulation control system is designed based on a TMS320F2407 digital signal processor (DSP), and has done a large amount of experimental research, which mainly include, variable speed constant frequency, constant pressure, Grid connected control experiment. The running results show that the design of simulation control system is reasonable and can meet the need of experimental research.
DEFF Research Database (Denmark)
Ghzaiel, Walid; Jebali-Ben Ghorbal, Manel; Slama-Belkhodja, Ilhem
2013-01-01
and to take the decision of either keep the DG connected, or disconnect it from the utility grid. The proposed method is based on a fast and easy grid fault detection method. A virtual damping resistance is used to drive the system to the resonance in order to extract the grid impedance parameters, both...... the power quality and even damage some sensitive loads connected at the point of the common coupling (PCC). This paper presents detection-estimation method of the grid impedance variation. This estimation tehnique aims to improve the dynamic of the distributed generation (DG) interfacing inverter control...
Modified Perfect Harmonics Cancellation Control of a Grid Interfaced SPV Power Generation
Singh, B.; Shahani, D. T.; Verma, A. K.
2015-03-01
This paper deals with a grid interfaced solar photo voltaic (SPV) power generating system with modified perfect harmonic cancellation (MPHC) control for power quality improvement in terms of mitigation of the current harmonics, power factor correction, control of point of common coupling (PCC) voltage with reactive power compensation and load balancing in a three phase distribution system. The proposed grid interfaced SPV system consists of a SPV array, a dc-dc boost converter and a voltage source converter (VSC) used for the compensation of other connected linear and nonlinear loads at PCC. The reference grid currents are estimated using MPHC method and control signals are derived by using pulse width modulation (PWM) current controller of VSC. The SPV power is fed to the common dc bus of VSC and dc-dc boost converter using maximum power point tracking (MPPT). The dc link voltage of VSC is regulated by using dc voltage proportional integral (PI) controller. The analysis of the proposed SPV power generating system is carried out under dc/ac short circuit and severe SPV-SX and SPV-TX intrusion.
International Nuclear Information System (INIS)
Poudineh, Rahmatallah; Jamasb, Tooraj
2014-01-01
The need for investment in capital intensive electricity networks is on the rise in many countries. A major advantage of distributed resources is their potential for deferring investments in distribution network capacity. However, utilizing the full benefits of these resources requires addressing several technical, economic and regulatory challenges. A significant barrier pertains to the lack of an efficient market mechanism that enables this concept and also is consistent with business model of distribution companies under an unbundled power sector paradigm. This paper proposes a market-oriented approach termed as “contract for deferral scheme” (CDS). The scheme outlines how an economically efficient portfolio of distributed generation, storage, demand response and energy efficiency can be integrated as network resources to reduce the need for grid capacity and defer demand driven network investments. - Highlights: • The paper explores a practical framework for smart electricity distribution grids. • The aim is to defer large capital investments in the network by utilizing and incentivising distributed generation, demand response, energy efficiency and storage as network resources. • The paper discusses a possible new market model that enables integration of distributed resources as alternative to grid capacity enhancement
Simulation of off-grid generation options for remote villages in Cameroon
International Nuclear Information System (INIS)
Nfah, E.M.; Ngundam, J.M.; Vandenbergh, M.; Schmid, J.
2008-01-01
Off-grid generation options have been simulated for remote villages in Cameroon using a load of 110 kWh/day and 12 kWp. The energy costs of proposed options were simulated using HOMER, a typical village load profile, the solar resource of Garoua and the flow of river Mungo. For a 40% increase in the cost of imported power system components, the cost of energy was found to be 0.296 EUR/kWh for a micro-hydro hybrid system comprising a 14 kW micro-hydro generator, a 15 kW LPG generator and 36 kWh of battery storage. The cost of energy for photovoltaic (PV) hybrid systems made up of an 18 kWp PV generator, a 15 kW LPG generator and 72 kWh of battery storage was also found to be 0.576 EUR/kWh for remote petrol price of 1 EUR/l and LPG price of 0.70 EUR/m 3 . The micro-hydro hybrid system proved to be the cheapest option for villages located in the southern parts of Cameroon with a flow rate of at least 200l/s, while the PV hybrid system was the cheapest option for villages in the northern parts of Cameroon with an insolation level of at least 5.55 kWh/m 2 /day. For a single-wire grid extension cost of 5000 EUR/km, operation and maintenance costs of 125 EUR/yr/km and a local grid power price of 0.1 EUR/kWh, the breakeven grid extension distances were found to be 15.4 km for micro-hydro/LPG generator systems and 37.4 km for PV/LPG generator systems respectively. These results could be used in Cameroon's National Energy Action Plan for the provision of energy services in the key sectors involved in the fight against poverty. (author)
Ellipticities of Elliptical Galaxies in Different Environments
Chen, Cheng-Yu; Hwang, Chorng-Yuan; Ko, Chung-Ming
2016-10-01
We studied the ellipticity distributions of elliptical galaxies in different environments. From the ninth data release of the Sloan Digital Sky Survey, we selected galaxies with absolute {r}\\prime -band magnitudes between -21 and -22. We used the volume number densities of galaxies as the criterion for selecting the environments of the galaxies. Our samples were divided into three groups with different volume number densities. The ellipticity distributions of the elliptical galaxies differed considerably in these three groups of different density regions. We deprojected the observed 2D ellipticity distributions into intrinsic 3D shape distributions, and the result showed that the shapes of the elliptical galaxies were relatively spherically symmetric in the high density region (HDR) and that relatively more flat galaxies were present in the low density region (LDR). This suggests that the ellipticals in the HDRs and LDRs have different origins or that different mechanisms might be involved. The elliptical galaxies in the LDR are likely to have evolved from mergers in relatively anisotropic structures, such as filaments and webs, and might contain information on the anisotropic spatial distribution of their parent mergers. By contrast, elliptical galaxies in the HDR might be formed in more isotropic structures, such as galaxy clusters, or they might encounter more torqueing effects compared with galaxies in LDRs, thereby becoming rounder.
Flexible voltage support control for three-phase distributed generation inverters under grid fault
DEFF Research Database (Denmark)
Camacho, Antonio; Castilla, Miguel; Miret, Jaume
2013-01-01
Operators describe the behavior of the energy source, regulating voltage limits and reactive power injection to remain connected and support the grid under fault. On the basis that different kinds of voltage sags require different voltage support strategies, a flexible control scheme for three phase grid...... connected inverters is proposed. In three phase balanced voltage sags, the inverter should inject reactive power in order to raise the voltage in all phases. In one or two phase faults, the main concern of the distributed generation inverter is to equalize voltages by reducing the negative symmetric...... sequence and clear the phase jump. Due to system limitations, a balance between these two extreme policies is mandatory. Thus, over-voltage and undervoltage can be avoided, and the proposed control scheme prevents disconnection while achieving the desired voltage support service. The main contribution...
Generating grid states from Schrödinger-cat states without postselection
Weigand, Daniel J.; Terhal, Barbara M.
2018-02-01
Grid (or comb) states are an interesting class of bosonic states introduced by Gottesman, Kitaev, and Preskill [D. Gottesman, A. Kitaev, and J. Preskill, Phys. Rev. A 64, 012310 (2001), 10.1103/PhysRevA.64.012310] to encode a qubit into an oscillator. A method to generate or "breed" a grid state from Schrödinger cat states using beam splitters and homodyne measurements is known [H. M. Vasconcelos, L. Sanz, and S. Glancy, Opt. Lett. 35, 3261 (2010), 10.1364/OL.35.003261], but this method requires postselection. In this paper we show how postprocessing of the measurement data can be used to entirely remove the need for postselection, making the scheme much more viable. We bound the asymptotic behavior of the breeding procedure and demonstrate the efficacy of the method numerically.
Reliability Oriented Design Tool For the New Generation of Grid Connected PV-Inverters
DEFF Research Database (Denmark)
Sintamarean, Nicolae Cristian; Blaabjerg, Frede; Wang, Huai
2015-01-01
is achieved and is further used as an input to the lifetime model. The proposed reliability-oriented design tool is used to study the impact of mission profile (MP) variation and device degradation (aging) in the PV inverter lifetime. The obtained results indicate that the MP of the field where the PV...... inverter is operating has an important impact (up to 70%) on the converter lifetime expectation, and it should be considered in the design stage to better optimize the converter design margin. In order to have correct lifetime estimation, it is crucial to consider also the device degradation feedback (in......This paper introduces a reliability-oriented design tool for a new generation of grid-connected photovoltaic (PV) inverters. The proposed design tool consists of a real field mission profile (RFMP) model (for two operating regions: USA and Denmark), a PV panel model, a grid-connected PV inverter...
Directory of Open Access Journals (Sweden)
Youngho Cho
2017-09-01
Full Text Available This study investigates the emerging harmonic stability concerns to be addressed by grid planners in generation interconnection studies, owing to the increased adoption of renewable energy resources connected to the grid via power electronic converters. The wideband and high-frequency electromagnetic transient (EMT characteristics of these converter-interfaced generators (CIGs and their interaction with the grid impedance are not accurately captured in the typical dynamic studies conducted by grid planners. This paper thus identifies the desired components to be studied and subsequently develops a practical process for integrating a new CIG into a grid with the existing CIGs. The steps of this process are as follows: the impedance equation of a CIG using its control dynamics and an interface filter to the grid, for example, an LCL filter (inductor-capacitor-inductor type, is developed; an equivalent impedance model including the existing CIGs nearby and the grid observed from the point of common coupling are derived; the system stability for credible operating scenarios is assessed. Detailed EMT simulations validate the accuracy of the impedance models and stability assessment for various connection scenarios. By complementing the conventional EMT simulation studies, the proposed analytical approach enables grid planners to identify critical design parameters for seamlessly integrating a new CIG and ensuring the reliability of the grid.
Power Quality Improvement Utilizing Photovoltaic Generation Connected to a Weak Grid
Energy Technology Data Exchange (ETDEWEB)
Muljadi, Eduard [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Tumbelaka, Hanny H. [Petra Christian University; Gao, Wenzhong [UNiversity of Denver
2017-11-07
Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids and may have been considered as the culprit of poor power quality affecting other loads in particular sensitive loads connected to the same point of common coupling (PCC). This paper is intended to demystify the renewable generation, and turns the negative perception into positive revelation of the superiority of PV generation to the power quality improvement in a microgrid system. The main objective of this work is to develop a control method for the PV inverter so that the power quality at the PCC will be improved under various disturbances. The method is to control the reactive current based on utilizing the grid current to counteract the negative impact of the disturbances. The proposed control method is verified in PSIM platform. Promising results have been obtained.
Karaliolios, P.; Slootweg, J.G.; Kling, W.L.
2010-01-01
Notwithstanding the positive environmental impact, the increasing penetration of Distributed Generation (DG) units connected to the distribution network raises new topics concerning the expected response of these during outages. Grid disturbances especially at the transmission level can cause the
DEFF Research Database (Denmark)
Guo, Yougui; Zeng, Ping; Li, Lijuan
2011-01-01
Adaptive hysteresis band current control(AHB CC) is used to control the three-phase grid currents by means of grid side converter in wind power generation system in this paper. AHB has reached the good purpose with PLL (Lock phase loop). First the mathematical models of each part are given......, transformer and grid, and control parts, etc. The simulation results have verified that the control strategy is feasible to fit for control of gird currents, active power, reactive power and DC-link voltage in wind power generation system....
Fujii, K.
1983-01-01
A method for generating three dimensional, finite difference grids about complicated geometries by using Poisson equations is developed. The inhomogenous terms are automatically chosen such that orthogonality and spacing restrictions at the body surface are satisfied. Spherical variables are used to avoid the axis singularity, and an alternating-direction-implicit (ADI) solution scheme is used to accelerate the computations. Computed results are presented that show the capability of the method. Since most of the results presented have been used as grids for flow-field computations, this is indicative that the method is a useful tool for generating three-dimensional grids about complicated geometries.
Visualization of grid-generated turbulence in He II using PTV
Mastracci, B.; Guo, W.
2017-12-01
Due to its low viscosity, cryogenic He II has potential use for simulating large-scale, high Reynolds number turbulent flow in a compact and efficient apparatus. To realize this potential, the behavior of the fluid in the simplest cases, such as turbulence generated by flow past a mesh grid, must be well understood. We have designed, constructed, and commissioned an apparatus to visualize the evolution of turbulence in the wake of a mesh grid towed through He II. Visualization is accomplished using the particle tracking velocimetry (PTV) technique, where μm-sized tracer particles are introduced to the flow, illuminated with a planar laser sheet, and recorded by a scientific imaging camera; the particles move with the fluid, and tracking their motion with a computer algorithm results in a complete map of the turbulent velocity field in the imaging region. In our experiment, this region is inside a carefully designed He II filled cast acrylic channel measuring approximately 16 × 16 × 330 mm. One of three different grids, which have mesh numbers M = 3, 3.75, or 5 mm, can be attached to the pulling system which moves it through the channel with constant velocity up to 600 mm/s. The consequent motion of the solidified deuterium tracer particles is used to investigate the energy statistics, effective kinematic viscosity, and quantized vortex dynamics in turbulent He II.
DEFF Research Database (Denmark)
Li, H.; Zhao, B.; Yang, C.
2011-01-01
based on normal form theory is proposed. The transient models of the wind turbine generation system including the flexible drive train model are derived based on the direct transient stability estimation method. A method of critical clearing time (CCT) calculation is developed for the transient......Increasing levels of wind energy in modern electrical power system is initiating a need for accurate analysis and estimation of transient stability of wind turbine generation systems. This paper investigates the transient behaviors and possible direct methods for transient stability evaluation...... of a grid-connected wind turbine with squirrel cage induction generator (SCIG). Firstly, by using an equivalent lump mass method, a three-mass wind turbine equivalent model is proposed considering both the blades and the shaft flexibility of the wind turbine drive train system. Combined with the detailed...
Sonora: A New Generation Model Atmosphere Grid for Brown Dwarfs and Young Extrasolar Giant Planets
Marley, Mark S.; Saumon, Didier; Fortney, Jonathan J.; Morley, Caroline; Lupu, Roxana Elena; Freedman, Richard; Visscher, Channon
2017-01-01
Brown dwarf and giant planet atmospheric structure and composition has been studied both by forward models and, increasingly so, by retrieval methods. While indisputably informative, retrieval methods are of greatest value when judged in the context of grid model predictions. Meanwhile retrieval models can test the assumptions inherent in the forward modeling procedure. In order to provide a new, systematic survey of brown dwarf atmospheric structure, emergent spectra, and evolution, we have constructed a new grid of brown dwarf model atmospheres. We ultimately aim for our grid to span substantial ranges of atmospheric metallilcity, C/O ratios, cloud properties, atmospheric mixing, and other parameters. Spectra predicted by our modeling grid can be compared to both observations and retrieval results to aid in the interpretation and planning of future telescopic observations. We thus present Sonora, a new generation of substellar atmosphere models, appropriate for application to studies of L, T, and Y-type brown dwarfs and young extrasolar giant planets. The models describe the expected temperature-pressure profile and emergent spectra of an atmosphere in radiative-convective equilibrium for ranges of effective temperatures and gravities encompassing 200 less than or equal to T(sub eff) less than or equal to 2400 K and 2.5 less than or equal to log g less than or equal to 5.5. In our poster we briefly describe our modeling methodology, enumerate various updates since our group's previous models, and present our initial tranche of models for cloudless, solar metallicity, and solar carbon-to-oxygen ratio, chemical equilibrium atmospheres. These models will be available online and will be updated as opacities and cloud modeling methods continue to improve.
Design of extraction system on grid of plasma generator electrode for pulsed electron irradiator
International Nuclear Information System (INIS)
Agus Purwadi; Bambang Siswanto; Lely Susita RM; Suprapto; Anjar Anggraini H; Ihwanul Azis
2016-01-01
It has been carried out design and study of electron extraction particularly for obtaining the electron extraction current via grid on the Plasma Generator Chamber (PGC) caused by the existence of extraction voltage U_a. Electrons of plasma surface emitted to acceleration region through emission window and then extracted acceleration by extraction voltage U_a through foil window to atmospheric region for being applied to any target. Applied extraction voltage U_a on PEI device influences the forming and energy value of electron extraction current I_e then the PGC dimension influences the product of thermal electron emission current I_e_0. It has been determinated the PGC geometry and dimension of producing electron extraction current based on arc discharge plasma current to desire on any plasma density. From the calculation yield for the value of plasma density n_e = 78 x 10"1"0 cm"-"3 and the arc discharge current Id = 80 A (pulse width τ = 100µs) used the PGC size of (80 x 20 x 40) cm"3. Emission window area of (65 x 15) cm"2 located on the low part surface of PGC is covered by a grid sheet made of stainless steel of rectangular shape and the distance of one grid hole to another is 0,25 mm each others. Current value of I_e beside depends on plasma parameters also depends on the size of grid holes. The optimum of geometry and size is rectangular with its side size of p ≈ 0,50 mm with the plasma parameters optimum (density value n_e = 10"1"6 m"-"3 and electron temperature T_e = 6 eV). From the initial experiment yields obtained that the electron extraction efficiency value α = 37,25 % on extraction voltage V = 3 kV. (author)
Chatterjee, A.; Ghoshal, S. P.; Mukherjee, V.
In this paper, a conventional thermal power system equipped with automatic voltage regulator, IEEE type dual input power system stabilizer (PSS) PSS3B and integral controlled automatic generation control loop is considered. A distributed generation (DG) system consisting of aqua electrolyzer, photovoltaic cells, diesel engine generator, and some other energy storage devices like flywheel energy storage system and battery energy storage system is modeled. This hybrid distributed system is connected to the grid. While integrating this DG with the onventional thermal power system, improved transient performance is noticed. Further improvement in the transient performance of this grid connected DG is observed with the usage of superconducting magnetic energy storage device. The different tunable parameters of the proposed hybrid power system model are optimized by artificial bee colony (ABC) algorithm. The optimal solutions offered by the ABC algorithm are compared with those offered by genetic algorithm (GA). It is also revealed that the optimizing performance of the ABC is better than the GA for this specific application.
Directory of Open Access Journals (Sweden)
Gianluca Brando
2016-09-01
Full Text Available In the context of grid connected photovoitaic (PV generation systems, there are two paramount aspects regarding the Maximum Power Point Tracking (MPPT of the photovoltaic units and the continuity of the service. The most diffused MPPT algorithms are based on either perturb and observe, or on an incremental conductance approach and need both PV current and voltage measurements. Several topology reconfigurable converters are also associated with the PV plants, guaranteeing fault-tolerant features. The generation continuity can also be assured by interleaved inverters, which keep the system operating at reduced maximum power in case of failure. In this paper, an evolution of a hysteresis based MPPT algorithm is presented, based on the measurement of only one voltage, together with a novel space vector modulation suitable for a two-channel three-phase grid connected interleaved inverter. The proposed MMPT algorithm and modulation technique are tested by means of several numerical analyses on a PV generation system of about 200 kW maximum power. The results testify the validity of the proposed strategies, showing good performance, even during a fault occurrence and in the presence of deep shading conditions.
International Nuclear Information System (INIS)
Carelli, M. D.
2002-01-01
An international consortium of industry, laboratory, university and utility establishments, led by Westinghouse, is developing a Generation IV Reactor, International Reactor Innovative and Secure (IRIS). IRIS is a modular, integral, light water cooled, low-to-medium power (100-350 MWe) reactor which addresses the requirements defined by the US DOE for Generation IV reactors, i.e., fuel cycle sustainability, enhanced reliability and safety, and improved economics. It features innovative, advanced engineering, but it does not require new technology development since it relies on the proven technology of light water reactors. This paper presents the current reference IRIS design, which features a 1000 MWt thermal core with proven 5%-enriched uranium oxide fuel and four-year long straight burn fuel cycle, integral reactor vessel housing helical tube steam generators and immersed spool pumps. Other major contributors to the high level of safety and economic attractiveness are the safety by design and optimized maintenance approaches, which allow elimination of some classes of accidents, lower capital cost, long operating cycle, and high capacity factors. The path forward for possible future extension to a eight-year cycle will be also discussed. IRIS has a large potential worldwide market because of its proven technology, modularity, low financing, compatibility with existing grids and very limited infrastructure requirements. It is especially appealing to developing countries because of ease of operation and because its medium power is more adaptable to smaller grids. (author)
Generation-Side Power Scheduling in a Grid-Connected DC Microgrid
DEFF Research Database (Denmark)
Hernández, Adriana Carolina Luna; Aldana, Nelson Leonardo Diaz; Meng, Lexuan
2015-01-01
In this paper, a constrained mixed-integer programming model for scheduling the active power supplied by the generation units in storage-based DC microgrids is presented. The optimization problem minimizes operating costs taking into account a two-stage mode operation of the energy storage system...... so that a more accurate model for optimization of the microgrid operation can be obtained. The model is used in a particular grid-connected DC microgrid that includes two renewable energy sources and an energy storage system which supply a critical load. The results of the scheduling process...
DEFF Research Database (Denmark)
Blaabjerg, Frede; Vilathgamuwa, D. M.; Loh, Poh Chiang
2009-01-01
Distributed generation (DG) systems are usually connected to the grid using power electronic converters. Power delivered from such DG sources depends on factors like energy availability and load demand. The converters used in power conversion do not operate with their full capacity all the time......-stage buck-boost inverter, recently proposed Z-source inverter (ZSI) is a good candidate for future DG systems. This paper presents a controller design for a ZSI-based DG system to improve power quality of distribution systems. The proposed control method is tested with simulation results obtained using...
Hydrodynamic simulation of elliptic flow
Kolb, P F; Ruuskanen, P V; Heinz, Ulrich W
1999-01-01
We use a hydrodynamic model to study the space-time evolution transverse to the beam direction in ultrarelativistic heavy-ion collisions with nonzero impact parameters. We focus on the influence of early pressure on the development of radial and elliptic flow. We show that at high energies elliptic flow is generated only during the initial stages of the expansion while radial flow continues to grow until freeze-out. Quantitative comparisons with SPS data from semiperipheral Pb+Pb collisions suggest the applicability of hydrodynamical concepts already $\\approx$ 1 fm/c after impact.
Newton flows for elliptic functions
Helminck, G.F.; Twilt, F.
2015-01-01
Newton flows are dynamical systems generated by a continuous, desingularized Newton method for mappings from a Euclidean space to itself. We focus on the special case of meromorphic functions on the complex plane. Inspired by the analogy between the rational (complex) and the elliptic (i.e., doubly
Demand response impacts on off-grid hybrid photovoltaic-diesel generator microgrids
Directory of Open Access Journals (Sweden)
Aaron St. Leger
2015-08-01
Full Text Available Hybrid microgrids consisting of diesel generator set(s and converter based power sources, such as solar photovoltaic or wind sources, offer an alternative to generator based off-grid power systems. The hybrid approach has been shown to be economical in many off-grid applications and can result in reduced generator operation, fuel requirements, and maintenance. However, the intermittent nature of demand and renewable energy sources typically require energy storage, such as batteries, to properly operate the hybrid microgrid. These batteries increase the system cost, require proper operation and maintenance, and have been shown to be unreliable in case studies on hybrid microgrids. This work examines the impacts of leveraging demand response in a hybrid microgrid in lieu of energy storage. The study is performed by simulating two different hybrid diesel generator—PV microgrid topologies, one with a single diesel generator and one with multiple paralleled diesel generators, for a small residential neighborhood with varying levels of demand response. Various system designs are considered and the optimal design, based on cost of energy, is presented for each level of demand response. The solar resources, performance of solar PV source, performance of diesel generators, costs of system components, maintenance, and operation are modeled and simulated at a time interval of ten minutes over a twenty-five year period for both microgrid topologies. Results are quantified through cost of energy, diesel fuel requirements, and utilization of the energy sources under varying levels of demand response. The results indicate that a moderate level of demand response can have significant positive impacts to the operation of hybrid microgrids through reduced energy cost, fuel consumption, and increased utilization of PV sources.
Distributed Generation Integration in the Electric Grid: Energy Storage System for Frequency Control
Directory of Open Access Journals (Sweden)
Maurizio Delfanti
2014-01-01
Full Text Available During the last few years generation from renewable energy sources (RESs has grown considerably in European electrical networks. Transmission system operators are greatly concerned about the impact of RESs on the operational security and efficiency of their networks and more in general of the ENTSO-E interconnected system. Grid codes are to be revised in order to harmonise the rules regarding the connection of RES power plants. A main issue concerns frequency control: frequency is greatly affected by RESs intermittency and its deviations must be limited as much as possible in order to guarantee a suitable level of power quality. To improve frequency stability, in the future, Grid codes could extend frequency control requirements also to RES units, whereas today they are applied only to conventional power plants. Energy storage systems can be a possible solution to increase the flexibility and performance of RES power plants: they allow generators to modulate their power injections without wasting renewable energy. In this paper, the authors studied the suitability of extending frequency control to RES units integrating them with energy storage systems. In particular, the paper focuses on the impact of frequency control on the storage lifetime by analysing the power charge/discharge in response to real frequency oscillations.
A novel method for automated grid generation of ice shapes for local-flow analysis
Ogretim, Egemen; Huebsch, Wade W.
2004-02-01
Modelling a complex geometry, such as ice roughness, plays a key role for the computational flow analysis over rough surfaces. This paper presents two enhancement ideas in modelling roughness geometry for local flow analysis over an aerodynamic surface. The first enhancement is use of the leading-edge region of an airfoil as a perturbation to the parabola surface. The reasons for using a parabola as the base geometry are: it resembles the airfoil leading edge in the vicinity of its apex and it allows the use of a lower apparent Reynolds number. The second enhancement makes use of the Fourier analysis for modelling complex ice roughness on the leading edge of airfoils. This method of modelling provides an analytical expression, which describes the roughness geometry and the corresponding derivatives. The factors affecting the performance of the Fourier analysis were also investigated. It was shown that the number of sine-cosine terms and the number of control points are of importance. Finally, these enhancements are incorporated into an automated grid generation method over the airfoil ice accretion surface. The validations for both enhancements demonstrate that they can improve the current capability of grid generation and computational flow field analysis around airfoils with ice roughness.
Renewable energy technology for off-grid power generation solar hybrid system
International Nuclear Information System (INIS)
Mohd Azhar Abd Rahman
2006-01-01
Off-grid power generation is meant to supply remote or rural area, where grid connection is almost impossible in terms of cost and geography, such as island, aborigine's villages, and areas where nature preservation is concern. Harnessing an abundance renewable energy sources using versatile hybrid power systems can offer the best, least-cost alternative solution for extending modern energy services to remote and isolated communities. The conventional method for off-grid power generation is using diesel generator with a renewable energy (RE) technology utilizing solar photovoltaic, wind, biomass, biogas and/or mini/micro hydro. A hybrid technology is a combination of multiple source of energy; such as RE and diesel generator and may also include energy storage such as battery. In our design, the concept of solar hybrid system is a combination of solar with diesel genset and battery as an energy storage. The main objective of the system are to reduce the cost of operation and maintenance, cost of logistic and carbon dioxide (CO 2 ) emission. The operational concept of solar hybrid system is that solar will be the first choice of supplying load and excess energy produced will be stored in battery. Genset will be a secondary source of energy. The system is controlled by a microprocessor-based controlled to manage the energy supplied and load demand. The solar hybrid system consists of one or two diesel generator with electronic control system, lead-acid battery system, solar PV, inverter module and system controller with remote monitoring capability. The benefits of solar hybrid system are: Improved reliability, Improved energy services, reduced emissions and pollution, provide continuous power supply, increased operational life, reduced cost, and more efficient use of power. Currently, such system has been installed at Middle and Top Station of Langkawi Cable Car, Langkawi and Aborigines Village Kg Denai, Rompin, Pahang. The technology is considered new in Malaysia
Renewable Distributed Generation Models in Three-Phase Load Flow Analysis for Smart Grid
Directory of Open Access Journals (Sweden)
K. M. Nor
2013-11-01
Full Text Available The paper presents renewable distributed generationÂ (RDG models as three-phase resource in load flow computation and analyzes their effect when they are connected in composite networks. The RDG models that have been considered comprise of photovoltaic (PV and wind turbine generation (WTG. The voltage-controlled node and complex power injection node are used in the models. These improvement models are suitable for smart grid power system analysis. The combination of IEEE transmission and distribution data used to test and analyze the algorithm in solving balanced/unbalanced active systems. The combination of IEEE transmission data and IEEE test feeder are used to test the the algorithm for balanced and unbalanced multi-phase distribution system problem. The simulation results show that by increased number and size of RDG units have improved voltage profile and reduced system losses.
International Nuclear Information System (INIS)
Jou, Hurng-Liahng; Chang, Yi-Hao; Wu, Jinn-Chang; Wu, Kuen-Der
2015-01-01
Highlights: • The operation strategy for grid-connected PV generation system integrated with battery energy storage is proposed. • The PV system is composed of an inverter and two DC-DC converter. • The negative impact of grid-connected PV generation systems on the grid can be alleviated by integrating a battery. • The operation of the developed system can be divided into nine modes. - Abstract: The operation strategy for a lab-scale grid-connected photovoltaic generation system integrated with battery energy storage is proposed in this paper. The photovoltaic generation system is composed of a full-bridge inverter, a DC–DC boost converter, an isolated bidirectional DC–DC converter, a solar cell array and a battery set. Since the battery set acts as an energy buffer to adjust the power generation of the solar cell array, the negative impact on power quality caused by the intermittent and unstable output power from a solar cell array is alleviated, so the penetration rate of the grid-connected photovoltaic generation system is increased. A lab-scale prototype is developed to verify the performance of the system. The experimental results show that it achieves the expected performance
Energy Technology Data Exchange (ETDEWEB)
Alvarez-Bel, C.; Escriva-Escriva, G.; Alcazar-Ortega, M. [Institute for Energy Engineering, Universitat Politecnica de Valencia, Valencia (Spain)
2013-11-15
The aim of this research resides in the development of an energy management and control system to control a micro-grid based on the use of renewable generation and demand resources to introduce the application of demand response concepts to the management of micro-grids in order to effectively integrate the demand side as an operation resource for the grid and improve energy efficiency of the elements. As an additional result, the evaluation of reductions in the total amount of CO2 emitted into the atmosphere due to the improvement of the energy efficiency of the system is assessed.
Integration of permanent magnet synchronous generator wind turbines into power grid
Abedini, Asghar
The world is seeing an ever-increasing demand for electrical energy. The future growth of electrical power generation needs to be a mix of technologies including fossil fuels, hydro, nuclear, wind, and solar. The federal and state energy agencies have taken several proactive steps to increase the share of renewable energy in the total generated electrical power. In 2005, 11.1% of the total 1060 GW electricity generation capacity was from Renewable Energy Sources (RES) in the US. The power capacity portfolio included 9.2% from hydroelectric, 0.87% from wind, and 0.7% from biomass. Other renewable power capacity included 2.8 GW of geothermal, 0.4 GW of solar thermal, and 0.2 GW of solar PV. Although the share of renewable energy sources is small compared with the total power capacity, they are experiencing a high and steady growth. The US is leading the world in wind energy growth with a 27% increase in 2006 and a projected 26% increase in 2007, according to the American Wind Energy Association (AWEA). The US Department of Energy benchmarked a goal to meet 5% of the nation's energy need by launching the Wind Powering America (WPA) program. Although renewable energy sources have many benefits, their utilization in the electrical grid does not come without cost. The higher penetration of RES has introduced many technical and non-technical challenges, including power quality, reliability, safety and protection, load management, grid interconnections and control, new regulations, and grid operation economics. RES such as wind and PV are also intermittent in nature. The energy from these sources is available as long as there is wind or sunlight. However, these are energies that are abundant in the world and the power generated from these sources is pollution free. Due to high price of foundation of wind farms, employing variable speed wind turbines to maximize the extracted energy from blowing wind is more beneficial. On the other hand, since wind power is intermittent
DEFF Research Database (Denmark)
Yao, Jun; Li, Qing; Chen, Zhe
2013-01-01
in the multiple synchronous rotating reference frames. In order to counteract the adverse effects of the voltage harmonics upon the DFIG, the SGSC generates series compensation control voltages to keep the stator voltage sinusoidal and symmetrical, which allows the use of the conventional vector control strategy......This paper presents a coordinated control method for a doubly-fed induction generator (DFIG)-based wind-power generation system with a series grid-side converter (SGSC) under distorted grid voltage conditions. The detailed mathematical models of the DFIG system with SGSC are developed...
Impact of Distributed Generation Grid Code Requirements on Islanding Detection in LV Networks
Directory of Open Access Journals (Sweden)
Fabio Bignucolo
2017-01-01
Full Text Available The recent growing diffusion of dispersed generation in low voltage (LV distribution networks is entailing new rules to make local generators participate in network stability. Consequently, national and international grid codes, which define the connection rules for stability and safety of electrical power systems, have been updated requiring distributed generators and electrical storage systems to supply stabilizing contributions. In this scenario, specific attention to the uncontrolled islanding issue has to be addressed since currently required anti-islanding protection systems, based on relays locally measuring voltage and frequency, could no longer be suitable. In this paper, the effects on the interface protection performance of different LV generators’ stabilizing functions are analysed. The study takes into account existing requirements, such as the generators’ active power regulation (according to the measured frequency and reactive power regulation (depending on the local measured voltage. In addition, the paper focuses on other stabilizing features under discussion, derived from the medium voltage (MV distribution network grid codes or proposed in the literature, such as fast voltage support (FVS and inertia emulation. Stabilizing functions have been reproduced in the DIgSILENT PowerFactory 2016 software environment, making use of its native programming language. Later, they are tested both alone and together, aiming to obtain a comprehensive analysis on their impact on the anti-islanding protection effectiveness. Through dynamic simulations in several network scenarios the paper demonstrates the detrimental impact that such stabilizing regulations may have on loss-of-main protection effectiveness, leading to an increased risk of unintentional islanding.
Grid-Forming-Mode Operation of Boost-Power-Stage Converter in PV-Generator-Interfacing Applications
Directory of Open Access Journals (Sweden)
Jukka Viinamäki
2017-07-01
Full Text Available The application of constant power control and inclusion of energy storage in grid-connected photovoltaic (PV energy systems may increase the use of two-stage system structures composed of DC–DC-converter-interfaced PV generator and grid-connected inverter connected in cascade. A typical PV-generator-interfacing DC–DC converter is a boost-power-stage converter. The renewable energy system may operate in three different operation modes—grid-forming, grid-feeding, and grid-supporting modes. In the last two operation modes, the outmost feedback loops are taken from the input terminal of the associated power electronic converters, which usually does not pose stability problems in terms of their input sources. In the grid-forming operation mode, the outmost feedback loops have to be connected to the output terminal of the associated power electronic converters, and hence the input terminal will behave as a negative incremental resistor at low frequencies. This property will limit the operation of the PV interfacing converter in either the constant voltage or constant current region of the PV generator for ensuring stable operation. The boost-power-stage converter can be applied as a voltage or current-fed converter limiting the stable operation region accordingly. The investigations of this paper show explicitly that only the voltage-fed mode would provide feasible dynamic and stability properties as a viable interfacing converter.
Directory of Open Access Journals (Sweden)
Krishnan Arthishri
2017-05-01
Full Text Available In this study, a three-phase diode bridge rectifier and a single-phase voltage source inverter topology has been proposed for feeding single-phase utility grid employing a three-phase induction generator fed from wind energy. A self-excited induction generator configuration has been chosen for wide speed operation of wind turbine system, which gives the scope for extracting maximum power available in the wind. In addition to maximum power point tracking (MPPT, the generator can be loaded to its rated capacity for feeding single-phase utility grid using a three-phase induction machine, whereas it is not possible with existing configurations because of the absence of power converters. For the proposed system, MPPT algorithm has been devised by continuously monitoring the grid current and a proportional resonant controller has been employed for grid synchronisation of voltage source inverter with single-phase grid. A MATLAB/Simulink model of the proposed system has been developed to ascertain its successful working by predetermining the overall performance characteristics. The present proposal has also been tested with sag, swell and distortion in the grid voltage. The control strategy has been implemented using field programmable gate array (FPGA controller with modularised programming approach. The efficacy of the system has been demonstrated with the results obtained from an experimental set-up in the laboratory.
Evaluation small scale, grid connected wind and solar distributed generation systems in Jordan
International Nuclear Information System (INIS)
Naji, G. J.; Tahboub, K. K.; Jalham, I. S.
2011-01-01
In this paper, the potential of utilizing wind and solar Private Distributed Generation (PDG) for utility interactive systems is investigated for 11 selected stations (sites) in Jordan. Six customer categories are considered: residential, office, commercial mall, school, hospital and hotel. The main goal of this study was to evaluate the potential of utilizing different grid connected PDG under different conditions such as their location, size, served building category, number of people who share and own the equipment and system type whether wind, solar or hybrid based. It was found that solar systems are still not attractive for all location due to their associated high cost, while wind systems would vary widely depending on the customer category, location and the size of the equipment. Based on the Benefit to Cost ratio criterion, the most attractive sites for installing wind PDGS for residential communities are Ras Muneef, Mafraq, Aqaba, Irbid and H5, while it doesn't seem attractive at Amman,Shoubak, Ghor Essafi, Deir Alla, Maan and H4. On the other hand, the wind on-grid PDGS is very attractive at Ras Muneef, mafraq and Aqaba for commercial buildings, less attractive at H5 and irbid, while it's not attractive at the other sites. The attraction for hybrid PDG systems is closer to those of wind systems alone. (authors).
A report on the performance of a grid connected photovoltaic power generation system
International Nuclear Information System (INIS)
Mohd Azhar Abdul Rahman; Mohd Surif Abdul Wahab; Azmi Omar
2000-01-01
Malaysia is located almost on the equator and is blessed with an abundance of sunlight almost all year round. So obviously, with the right planning and strategies that are coupled to the right technology and development in the market, the potential for photovoltaic system as an alternative source of power in this country looks promising and is constantly gaining ground and popularity. Sunlight is free and the photovoltaic system is also emission and pollution free which is a guest boost to the current worldwide effort to reduce the global environmental problems. Utility giant Tenaga Nasional Berhad is in line with the Government aspiration to promote the development of solar photovoltaic in the country, who believe in the success and acceptance potential of the photovoltaic system as an alternative source of power generation for long term energy option. In March 1998, a contract was awarded by Tenaga Nasional Berhad to its research subsidiary, Tenaga Nasional Research and Development Sdn. Bhd. to undertake a pilot research project on the development of a grid connected photovoltaic system. This research project is co-funded by the Electric Supply Industry Trust fund. One of the main objective of this research project is to seek the best approach to popularize the Grid Connected Photovoltaic System for domestic as well as suitable commercial premises in this country. This paper will report the initial findings of the project in terms of technical capability and commercial liability. (Author)
Guhathakurta, Puragra; Toloba, Elisa; Peng, Eric W.; Li, Biao; Gwyn, Stephen; Ferrarese, Laura; Cote, Patrick; Chu, Jason; Sparkman, Lea; Chen, Stephanie; Yagati, Samyukta; Muller, Meredith; Next Generation Virgo Survey Collaboration
2015-01-01
We present results from an ongoing study of globular cluster (GC) satellites of low-luminosity dwarf elliptical (dE) galaxies in the Virgo cluster. Our 21 dE targets and candidate GC satellites around them in the apparent magnitude range g ~ 20-24 were selected from the Next Generation Virgo Survey (NGVS) and followed up with medium-resolution Keck/DEIMOS spectroscopy (resolving power: R ~ 2000; wavelength coverage: 4800-9500 Angstrom). In addition, the remaining space available on the nine DEIMOS multi-slit masks were populated with "filler" targets in the form of distant Milky Way halo star candidates in a comparable apparent magnitude range. A combination of radial velocity information (measured from the Keck/DEIMOS spectra), color-color information (from four-band NGVS photometry), and sky position information was used to sort the sample into the following categories: (1) GC satellites of dEs, (2) other non-satellite GCs in the Virgo cluster (we dub them "orphan" GCs), (3) foreground Milky Way stars that are members of the Sagittarius stream, the Virgo overdensity, or the field halo population, and (4) distant background galaxies. We stack the GC satellite population across all 21 host dEs and carry out dynamical modeling of the stacked sample in order to constrain the average mass of dark matter halos that these dEs are embedded in. We study rotation in the system of GC satellites of dEs in the handful of more populated systems in our sample - i.e., those that contain 10 or more GC satellites per dE. A companion AAS poster presented at this meeting (Chu, J. et al. 2015) presents chemical composition and age constraints for these GC satellites relative to the nuclei of the host dEs based on absorption line strengths in co-added spectra. The orphan GCs are likely to be intergalactic GCs within the Virgo cluster (or, equivalently, GCs in the remote outer envelope of the cluster's central galaxy, the giant elliptical M87).This project is funded in part by the
GSIMF: a web service based software and database management system for the next generation grids
International Nuclear Information System (INIS)
Wang, N; Ananthan, B; Gieraltowski, G; May, E; Vaniachine, A
2008-01-01
To process the vast amount of data from high energy physics experiments, physicists rely on Computational and Data Grids; yet, the distribution, installation, and updating of a myriad of different versions of different programs over the Grid environment is complicated, time-consuming, and error-prone. Our Grid Software Installation Management Framework (GSIMF) is a set of Grid Services that has been developed for managing versioned and interdependent software applications and file-based databases over the Grid infrastructure. This set of Grid services provide a mechanism to install software packages on distributed Grid computing elements, thus automating the software and database installation management process on behalf of the users. This enables users to remotely install programs and tap into the computing power provided by Grids
International Nuclear Information System (INIS)
Rivarolo, M.; Greco, A.; Massardo, A.F.
2013-01-01
Highlights: ► We model a poly-generation grid including thermal storage and renewable generators. ► We analyze the impact of random renewable generators on the grid performance. ► We carry out the grid optimization using a time-dependent thermo-economic approach. ► We present the importance of the storage system to optimize the RES impact. - Abstract: In this paper, the impact of not controllable renewable energy generators (wind turbines and solar photovoltaic panels) on the thermo-economic optimum performance of poly-generation smart grids is investigated using an original time dependent hierarchical approach. The grid used for the analysis is the one installed at the University of Genoa for research activities. It is based on different prime movers: (i) 100 kWe micro gas turbine, (ii) 20 kWe internal combustion engine powered by gases to produce both electrical and thermal (hot water) energy and (iii) a 100 kWth adsorption chiller to produce cooling (cold water) energy. The grid includes thermal storage tanks to manage the thermal demand load during the year. The plant under analysis is also equipped with two renewable non-controllable generators: a small size wind turbine and photovoltaic solar panels. The size and the management of the system studied in this work have been optimized, in order to minimize both capital and variable costs. A time-dependent thermo-economic hierarchical approach developed by the authors has been used, considering the time-dependent electrical, thermal and cooling load demands during the year as problem constraints. The results are presented and discussed in depth and show the strong interaction between fossil and renewable resources, and the importance of an appropriate storage system to optimize the RES impact taking into account the multiproduct character of the grid under investigation.
Integration operators for generating RDF/OWL-based user defined mediator views in a grid environment
Tawil, Abdel-Rahman H.; Taweel, Adel; Naeem, Usman; Montebello, Matthew; Bashroush, Rabih; Al-Nemrat, Ameer
2014-01-01
Research and development activities relating to the grid have generally focused on applications where data is stored in files. However, many scientific and commercial applications are highly dependent on Information Servers (ISs) for storage and organization of their data. A data-information system that supports operations on multiple information servers in a grid environment is referred to as an interoperable grid system. Different perceptions by end-users of interoperable systems in a grid ...
Directory of Open Access Journals (Sweden)
Mingchao Xia
2013-09-01
Full Text Available A low carbon, high efficiency and high quality power supply scheme for Distributed Generation (DG in a micro-grid is presented. A three-phase, four-leg DG grid-interfacing converter based on the improved structure of a Unified Power Quality Conditioner (UPQC, including a series converter and a parallel converter is adopted, and improved indirect and direct control strategies are proposed. It can be observed that these strategies effectively compensate for voltage sags, voltage swells and voltage distortion, as well as voltage power quality problems resulting from the nonlinear and unbalanced loads in a micro-grid. While solving the coupling interference from series–parallel, the grid-interfacing converter can achieve proper load power sharing in a micro-grid. In particular, an improved minimum-energy compensation method is proposed that can overcome the conventional compensation algorithm defects, ensure the load voltage’s phase angle stability, improve the voltage compensating ability and range, reduce the capacity and cost of converters, and reduce the shock of micro-grid switching between grid-connected mode and islanded mode. Moreover, the advantages/disadvantages and application situation of the two improved control strategies are analyzed. Finally, the performance of the proposed control strategies has been verified through a MATLAB/Simulink simulation under various operating conditions.
Modified Grid-Connected CSI for Hybrid PV/Wind Power Generation System
Directory of Open Access Journals (Sweden)
D. Amorndechaphon
2012-01-01
Full Text Available The principle of a power conditioning unit for hybrid PV/wind power generation system is proposed. The proposed power conditioner is based on the current source inverter (CSI topology. All energy sources are connected in parallel with a DC-bus through the modified wave-shaping circuits. To achieve the unity power factor at the utility grid, the DC-link current can be controlled via the wave-shaping circuits with the sinusoidal PWM scheme. In this work, the carrier-based PWM scheme is also proposed to minimize the utility current THD. The power rating of the proposed system can be increased by connecting more PV/wind modules through their wave-shaping circuits in parallel with the other modules. The details of the operating principles, the system configurations, and the design considerations are described. The effectiveness of the proposed CSI is demonstrated by simulation results.
Materials Innovation for Next-Generation T&D Grid Components. Workshop Summary Report
Energy Technology Data Exchange (ETDEWEB)
Taylor, Emmanuel [Energetics Incorporated, Columbia, MD (United States); Kramer, Caroline [Energetics Incorporated, Columbia, MD (United States); Marchionini, Brian [Energetics Incorporated, Columbia, MD (United States); Sabouni, Ridah [Energetics Incorporated, Columbia, MD (United States); Cheung, Kerry [U.S. Department of Energy (DOE), Washington, DC (United States). Office of Electricity Delivery and Energy Reliability (OE); Lee, Dominic F [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-10-01
The Materials Innovations for Next-Generation T&D Grid Components Workshop was co-sponsored by the U.S. Department of Energy (DOE) Office of Electricity Delivery and Energy Reliability and the Oak Ridge National Laboratory (ORNL) and held on August 26 27, 2015, at the ORNL campus in Oak Ridge, Tennessee. The workshop was planned and executed under the direction of workshop co-chair Dr. Kerry Cheung (DOE) and co-chair Dr. Dominic Lee (ORNL). The information contained herein is based on the results of the workshop, which was attended by nearly 50 experts from government, industry, and academia. The research needs and pathways described in this report reflect the expert opinions of workshop participants, but they are not intended to represent the views of the entire electric power community.
Adaptive Droop Control Applied to Distributed Generation Inverters Connected to the Grid
DEFF Research Database (Denmark)
Blaabjerg, Frede; Teodorescu, Remus; Vásquez, Juan C.
2008-01-01
This paper proposes a novel control for voltage source inverters connected to the grid. The control scheme is based on the droop method, and it uses some estimated variables from the grid such as the voltage and the frequency, and the magnitude and angle of the grid impedance. Hence, the inverter...
Grids for Kids gives next-generation IT an early start
2008-01-01
"Grids for Kids gives children a crash course in grid computing," explains co-organiser Anna Cook of the Enabling Grids for E-sciencE project. "We introduce them to concepts such as middleware, parallel processing and supercomputing, and give them opportunities for hands-on learning.
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede
2016-01-01
With a still increase of grid-connected Photovoltaic (PV) systems, challenges have been imposed on the grid due to the continuous injection of a large amount of fluctuating PV power, like overloading the grid infrastructure (e.g., transformers) during peak power production periods. Hence, advanced...
Cartographic Production for the FLaSH Map Study: Generation of Rugosity Grids, 2008
Robbins, Lisa L.; Knorr, Paul O.; Hansen, Mark
2010-01-01
Project Summary This series of raster data is a U.S. Geological Survey (USGS) Data Series release from the Florida Shelf Habitat Project (FLaSH). This disc contains two raster images in Environmental Systems Research Institute, Inc. (ESRI) raster grid format, jpeg image format, and Geo-referenced Tagged Image File Format (GeoTIFF). Data is also provided in non-image ASCII format. Rugosity grids at two resolutions (250 m and 1000 m) were generated for West Florida shelf waters to 250 m using a custom algorithm that follows the methods of Valentine and others (2004). The Methods portion of this document describes the specific steps used to generate the raster images. Rugosity, also referred to as roughness, ruggedness, or the surface-area ratio (Riley and others, 1999; Wilson and others, 2007), is a visual and quantitative measurement of terrain complexity, a common variable in ecological habitat studies. The rugosity of an area can affect biota by influencing habitat, providing shelter from elements, determining the quantity and type of living space, influencing the type and quantity of flora, affecting predator-prey relationships by providing cover and concealment, and, as an expression of vertical relief, can influence local environmental conditions such as temperature and moisture. In the marine environment rugosity can furthermore influence current flow rate and direction, increase the residence time of water in an area through eddying and current deflection, influence local water conditions such as chemistry, turbidity, and temperature, and influence the rate and nature of sedimentary deposition. State-of-the-art computer-mapping techniques and data-processing tools were used to develop shelf-wide raster and vector data layers. Florida Shelf Habitat (FLaSH) Mapping Project (http://coastal.er.usgs.gov/flash) endeavors to locate available data, identify data gaps, synthesize existing information, and expand our understanding of geologic processes in our dynamic
Energy Technology Data Exchange (ETDEWEB)
Szabo, S; Bodis, K; Huld, T [European Commission Joint Research Centre, Institute for Energy, Renewable Energy Unit, 2749 via Enrico Fermi, TP450, 21027 Ispra (Vatican City State, Holy See) (Italy); Moner-Girona, M, E-mail: Sandor.Szabo@ec.europa.eu [UNEP Energy Branch Division of Technology, Industry and Economics, 15 rue de Milan, F-75441, Paris CEDEX09 (France)
2011-07-15
Three rural electrification options are analysed showing the cost optimal conditions for a sustainable energy development applying renewable energy sources in Africa. A spatial electricity cost model has been designed to point out whether diesel generators, photovoltaic systems or extension of the grid are the least-cost option in off-grid areas. The resulting mapping application offers support to decide in which regions the communities could be electrified either within the grid or in an isolated mini-grid. Donor programs and National Rural Electrification Agencies (or equivalent governmental departments) could use this type of delineation for their program boundaries and then could use the local optimization tools adapted to the prevailing parameters.
International Nuclear Information System (INIS)
Szabo, S; Bodis, K; Huld, T; Moner-Girona, M
2011-01-01
Three rural electrification options are analysed showing the cost optimal conditions for a sustainable energy development applying renewable energy sources in Africa. A spatial electricity cost model has been designed to point out whether diesel generators, photovoltaic systems or extension of the grid are the least-cost option in off-grid areas. The resulting mapping application offers support to decide in which regions the communities could be electrified either within the grid or in an isolated mini-grid. Donor programs and National Rural Electrification Agencies (or equivalent governmental departments) could use this type of delineation for their program boundaries and then could use the local optimization tools adapted to the prevailing parameters.
Statistics about elliptic curves over finite prime fields
Gekeler, Ernst-Ulrich
2006-01-01
We derive formulas for the probabilities of various properties (cyclicity, squarefreeness, generation by random points) of the point groups of randomly chosen elliptic curves over random prime fields.
Energy Technology Data Exchange (ETDEWEB)
Lee, S.-J.; Kim, K.-H.; Park, H.-Y.; Seo, H.-R.; Park, M.; Yu, I.-K. [Changwon National Univ., SarimDong (Korea, Republic of). Dept. of Electrical Engineering
2007-07-01
In photovoltaics, the sun's light energy is captured to create electricity. One of the key issues about a photovoltaic (PV) generation system is to keep the output power of photovoltaic cells maximized under any weather conditions. In a conventional maximum power point tracking (MPPT) control method, both voltage and current coming out from PV array require feedback. The system may fail to track the MPP of a PV array when unexpected weather conditions happen. This paper proposed a novel PV output senseless (POS) control method to solve the problem. The proposed POS MPPT control method only had one factor to consider, the load current. To verify this theory, a POS MPPT control was applied to a manufactured PV generation system, and the results of the the simulated and experimental data under real weather conditions were compared and analyzed. Several tables and diagrams were presented, including the circuit diagram of a manufactured PV generation system connected to grid as well as the the specifications of the PV array and PCS used for the experiment. Reasonable results were obtained in this study. In addition, the scheme was found to be very useful in maximizing power from PV array to load with feedback of only the load current. 8 refs., 3 tabs., 15 figs.
Energy Technology Data Exchange (ETDEWEB)
Mueller, H.; Poeller, M. [DIgSILENT GmbH, 72810 Gomaringen (Germany); Basteck, A.; Tilscher, M.; Pfister, J. [Voith Turbo GmbH and Co. KG, 74564 Crailsheim (Germany)
2006-07-01
This paper analyzes grid integration aspects of a new type of variable-speed wind turbine, the directly coupled synchronous generator with hydro-dynamically controlled gearbox. In contrast to existing wind generators using synchronous generators, the generator of this concept is directly connected to the AC grid, without the application of any power electronics converter. Variable speed operation of the turbine is mechanically achieved by a gear box with continuously controllable variable gear box ratio. For this purpose, a detailed dynamic model of a 2 MW wind turbine with a Voith WinDrive has been implemented using the modelling environment of the simulation software DIgSILENT PowerFactory. For investigating grid compatibility aspects of this new wind generator concept, a model of a 50 MW wind farm, with typical layout, based on 25 wind turbines of the 2 MW-class has been analyzed. This paper focuses on the compatibility of the new concept with existing connection standards, such as the E.ON grid code. Of special interest are typical stability phenomena of synchronous generators, such as transient and oscillatory stability as well as power quality issues like voltage flicker. The results of stability studies are presented and possible advantages of the new concept with special focus on offshore applications are discussed.
Reliable Grid Condition Detection and Control of Single-Phase Distributed Power Generation Systems
DEFF Research Database (Denmark)
Ciobotaru, Mihai
standards addressed to the grid-connected systems will harmonize the combination of the DPGS and the classical power plants. Consequently, the major tasks of this thesis were to develop new grid condition detection techniques and intelligent control in order to allow the DPGS not only to deliver power...... to the utility grid but also to sustain it. This thesis was divided into two main parts, namely "Grid Condition Detection" and "Control of Single-Phase DPGS". In the first part, the main focus was on reliable Phase Locked Loop (PLL) techniques for monitoring the grid voltage and on grid impedance estimation...... techniques. Additionally, a new technique for detecting the islanding mode has been developed and successfully tested. In the second part, the main reported research was concentrated around adaptive current controllers based on the information provided by the grid condition detection techniques. To guarantee...
Energy Technology Data Exchange (ETDEWEB)
Gevorgian, Vahan; Koralewicz, Przemyslaw; Wallen, Robb; Muljadi, Eduard
2017-02-01
The rapid expansion of wind power has led many transmission system operators to demand modern wind power plants to comply with strict interconnection requirements. Such requirements involve various aspects of wind power plant operation, including fault ride-through and power quality performance as well as the provision of ancillary services to enhance grid reliability. During recent years, the National Renewable Energy Laboratory (NREL) of the U.S. Department of Energy has developed a new, groundbreaking testing apparatus and methodology to test and demonstrate many existing and future advanced controls for wind generation (and other renewable generation technologies) on the multimegawatt scale and medium-voltage levels. This paper describes the capabilities and control features of NREL's 7-MVA power electronic grid simulator (also called a controllable grid interface, or CGI) that enables testing many active and reactive power control features of modern wind turbine generators -- including inertial response, primary and secondary frequency responses, and voltage regulation -- under a controlled, medium-voltage grid environment. In particular, this paper focuses on the specifics of testing the balanced and unbalanced fault ride-through characteristics of wind turbine generators under simulated strong and weak medium-voltage grid conditions. In addition, this paper provides insights on the power hardware-in-the-loop feature implemented in the CGI to emulate (in real time) the conditions that might exist in various types of electric power systems under normal operations and/or contingency scenarios. Using actual test examples and simulation results, this paper describes the value of CGI as an ultimate modeling validation tool for all types of 'grid-friendly' controls by wind generation.
Optimal Dispatch of Unreliable Electric Grid-Connected Diesel Generator-Battery Power Systems
Xu, D.; Kang, L.
2015-06-01
Diesel generator (DG)-battery power systems are often adopted by telecom operators, especially in semi-urban and rural areas of developing countries. Unreliable electric grids (UEG), which have frequent and lengthy outages, are peculiar to these regions. DG-UEG-battery power system is an important kind of hybrid power system. System dispatch is one of the key factors to hybrid power system integration. In this paper, the system dispatch of a DG-UEG-lead acid battery power system is studied with the UEG of relatively ample electricity in Central African Republic (CAR) and UEG of poor electricity in Congo Republic (CR). The mathematical models of the power system and the UEG are studied for completing the system operation simulation program. The net present cost (NPC) of the power system is the main evaluation index. The state of charge (SOC) set points and battery bank charging current are the optimization variables. For the UEG in CAR, the optimal dispatch solution is SOC start and stop points 0.4 and 0.5 that belong to the Micro-Cycling strategy and charging current 0.1 C. For the UEG in CR, the optimal dispatch solution is of 0.1 and 0.8 that belongs to the Cycle-Charging strategy and 0.1 C. Charging current 0.1 C is suitable for both grid scenarios compared to 0.2 C. It makes the dispatch strategy design easier in commercial practices that there are a few very good candidate dispatch solutions with system NPC values close to that of the optimal solution for both UEG scenarios in CAR and CR.
International Nuclear Information System (INIS)
Xi, Lei; Yu, Tao; Yang, Bo; Zhang, Xiaoshun; Qiu, Xuanyu
2016-01-01
Highlights: • A novel distributed autonomous virtual tribes control system is proposed. • WPH-VTC strategy is designed to solve the distributed virtual tribes control. • Stochastic consensus game on mixed homogeneous and heterogeneous multi-agent are resolved. • The optimal total power reference and its dispatch are resolved simultaneously in a dynamic way. • The utilization rate of renewable energy is increased with a reduced carbon emissions. - Abstract: This paper proposes a novel electric power autonomy to satisfy the requirement of power generation optimization of smart grid and decentralized energy management system. A decentralized virtual tribes control (VTC) is developed which can effectively coordinate the regional dispatch centre and the distributed energy. Then a wolf pack hunting (WPH) strategy based VTC (WPH-VTC) is designed through combining the multi-agent system stochastic game and multi-agent system collaborative consensus, which is called the multi-agent system stochastic consensus game, to achieve the coordination and optimization of the decentralized VTC, such that different types of renewable energy can be effectively integrated into the electric power autonomy. The proposed scheme is implemented on a flexible and dynamic multi-agent stochastic game-based VTC simulation platform, which control performance is evaluated on a typical two-area load–frequency control power system and a practical Guangdong power grid model in southern China. Simulation results verify that it can improve the closed-loop system performances, increase the utilization rate of the renewable energy, reduce the carbon emissions, and achieve a fast convergence rate with significant robustness compared with those of existing schemes.
Directory of Open Access Journals (Sweden)
Matthew Perry
2017-06-01
Full Text Available A tool has been developed to statistically increase the temporal resolution of solar irradiance time series. Fine temporal resolution time series are an important input into the planning process for solar power plants, and lead to increased understanding of the likely short-term variability of solar energy. The approach makes use of the spatial variability of hourly gridded datasets around a location of interest to make inferences about the temporal variability within the hour. The unique characteristics of solar irradiance data are modelled by classifying each hour into a typical weather situation. Low variability situations are modelled using an autoregressive process which is applied to ramps of clear-sky index. High variability situations are modelled as a transition between states of clear sky conditions and different levels of cloud opacity. The methods have been calibrated to Australian conditions using 1 min data from four ground stations for a 10 year period. These stations, together with an independent dataset, have also been used to verify the quality of the results using a number of relevant metrics. The results show that the method generates realistic fine resolution synthetic time series. The synthetic time series correlate well with observed data on monthly and annual timescales as they are constrained to the nearest grid-point value on each hour. The probability distributions of the synthetic and observed global irradiance data are similar, with Kolmogorov-Smirnov test statistic less than 0.04 at each station. The tool could be useful for the estimation of solar power output for integration studies.
Energy Technology Data Exchange (ETDEWEB)
Lucas, H; Ferroukhi, R [et al.; IRENA Policy Advisory Services and Capacity Building Directorate, Abu Dhabi (United Arab Emirates)
2012-01-15
Over the past years, interest has grown in the potential for the renewable energy industry to create jobs. Governments are seeking win-win solutions to the dual challenge of high unemployment and climate change. By 2010, USD 51 billion had been pledged to renewables in stimulus packages, and by early 2011 there were 119 countries with some kind of policy target and/or support policy for renewable energy, such as feed-in tariffs, quota obligations, favourable tax treatment and public loans or grants, many of which explicitly target job creation as a policy goal. Policy-makers in many countries are now designing renewable energy policies that aim to create new jobs, build industries and benefit particular geographic areas. But how much do we know for certain about the job creation potential for renewable energy? This working paper aims to provide an overview of current knowledge on five questions: (1) How can jobs in renewable energy be characterised?; (2) How are they shared out across the technology value chain and what skill levels are required?; (3) How many jobs currently exist and where are they in the world?; (4) How many renewable energy jobs could there be in the future?; and (5) What policy frameworks can be used to promote employment benefits from renewable energy? This paper focuses on grid-connected electricity generation technologies and biofuels. Since the employment potential of off-grid applications is large, it will be covered by a forthcoming study by IRENA on job creation in the context of energy access, based on a number of case studies.
Empirical Analysis of the Variability of Wind Generation in India: Implications for Grid Integration
Energy Technology Data Exchange (ETDEWEB)
Phadke, Amol; Abhyankar, NIkit; Rao, Poorvi
2014-06-17
We analyze variability in load and wind generation in India to assess its implications for grid integration of large scale wind projects using actual wind generation and load data from two states in India, Karnataka and Tamil Nadu. We compare the largest variations in load and net load (load ?wind, i.e., load after integrating wind) that the generation fleet has to meet. In Tamil Nadu, where wind capacity is about 53percent of the peak demand, we find that the additional variation added due to wind over the current variation in load is modest; if wind penetration reaches 15percent and 30percent by energy, the additional hourly variation is less than 0.5percent and 4.5percent of the peak demand respectively for 99percent of the time. For wind penetration of 15percent by energy, Tamil Nadu system is found to be capable of meeting the additional ramping requirement for 98.8percent of the time. Potential higher uncertainty in net load compared to load is found to have limited impact on ramping capability requirements of the system if coal plants can me ramped down to 50percent of their capacity. Load and wind aggregation in Tamil Nadu and Karnataka is found to lower the variation by at least 20percent indicating the benefits geographic diversification. These findings suggest modest additional flexible capacity requirements and costs for absorbing variation in wind power and indicate that the potential capacity support (if wind does not generate enough during peak periods) may be the issue that has more bearing on the economics of integrating wind
Directory of Open Access Journals (Sweden)
Ali Reza Dehghanzadeh
2018-03-01
Full Text Available This paper studies the power electronic converters for grid connection of axial flux permanent magnetic synchronous generators (AFPMSG based variable speed wind turbine. In this paper, a new variable speed wind turbine with AFPMSG and Z-source inverter is proposed to improve number of switches and topology reliability. Besides, dynamic modeling of AFPMSG is presented to analyze grid connection of the proposed topology. The Z-source inverter controls maximum power point tracking (MPPT and delivering power to the grid. Therefore other DC–DC chopper is not required to control the rectified output voltage of generator in view of MPPT. As a result, the proposed topology requires less power electronic switches and the suggested system is more reliable against short circuit. The ability of proposed energy conversion system with AFPMSG is validated with simulation results and experimental results using PCI-1716 data acquisition system.
Minimum short-circuit ratios for grid interconnection of wind farms with induction generators
Energy Technology Data Exchange (ETDEWEB)
Reginatto, Romeu; Rocha, Carlos [Western Parana State University (UNIOESTE), Foz do Iguacu, PR (Brazil). Center for Engineering and Exact Sciences], Emails: romeu@unioeste.br, croberto@unioeste.br
2009-07-01
This paper concerns the problem of determining the minimum value for the short-circuit ratio which is adequate for the interconnection of a given wind farms to a given grid point. First, a set of 3 criteria is defined in order to characterize the quality/safety of the interconnection: acceptable terminal voltage variations, a minimum active power margin, and an acceptable range for the internal voltage angle. Then, the minimum short circuit ratio requirement is determined for 6 different induction generator based wind turbines, both fixed-speed (with and without reactive power compensation) and variable-speed (with the following control policies: reactive power, power factor, and terminal voltage regulation). The minimum short-circuit ratio is determined and shown in graphical results for the 6 wind turbines considered, for X/R in the range 0-15, also analyzing the effect of more/less stringent tolerances for the interconnection criteria. It is observed that the tighter the tolerances the larger the minimum short-circuit ratio required. For the same tolerances in the interconnection criteria, a comparison of the minimum short circuit ratio required for the interconnection of both squirrel-cage and doubly-fed induction generators is presented, showing that the last requires much smaller values for the short-circuit ratio. (author)
Energy Technology Data Exchange (ETDEWEB)
Mineev, Mark [Los Alamos National Laboratory
2008-01-01
The planar elliptic extension of the Laplacian growth is, after a proper parametrization, given in a form of a solution to the equation for areapreserving diffeomorphisms. The infinite set of conservation laws associated with such elliptic growth is interpreted in terms of potential theory, and the relations between two major forms of the elliptic growth are analyzed. The constants of integration for closed form solutions are identified as the singularities of the Schwarz function, which are located both inside and outside the moving contour. Well-posedness of the recovery of the elliptic operator governing the process from the continuum of interfaces parametrized by time is addressed and two examples of exact solutions of elliptic growth are presented.
Manonmani, N; Subbiah, V; Sivakumar, L
2015-01-01
The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs) supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs). The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation.
Directory of Open Access Journals (Sweden)
N. Manonmani
2015-01-01
Full Text Available The key objective of wind turbine development is to ensure that output power is continuously increased. It is authenticated that wind turbines (WTs supply the necessary reactive power to the grid at the time of fault and after fault to aid the flowing grid voltage. At this juncture, this paper introduces a novel heuristic based controller module employing differential evolution and neural network architecture to improve the low-voltage ride-through rate of grid-connected wind turbines, which are connected along with doubly fed induction generators (DFIGs. The traditional crowbar-based systems were basically applied to secure the rotor-side converter during the occurrence of grid faults. This traditional controller is found not to satisfy the desired requirement, since DFIG during the connection of crowbar acts like a squirrel cage module and absorbs the reactive power from the grid. This limitation is taken care of in this paper by introducing heuristic controllers that remove the usage of crowbar and ensure that wind turbines supply necessary reactive power to the grid during faults. The controller is designed in this paper to enhance the DFIG converter during the grid fault and this controller takes care of the ride-through fault without employing any other hardware modules. The paper introduces a double wavelet neural network controller which is appropriately tuned employing differential evolution. To validate the proposed controller module, a case study of wind farm with 1.5 MW wind turbines connected to a 25 kV distribution system exporting power to a 120 kV grid through a 30 km 25 kV feeder is carried out by simulation.
Energy Technology Data Exchange (ETDEWEB)
Laverdure, N
2005-12-15
Wind energy is now an energy that can not be ignored. Because of intrinsic characteristics (scattered primary energy, generators with different technologies, use of power electronics interface), wind energy system integration in distribution grids leads to real problems in terms of impacts. With recent standard changes, it is necessary to study the possibilities of each technology of wind turbines to answer or not to these new constraints. This PhD thesis focuses on a comparison of the main present wind turbines concerning three points of discussion: energy quality, fault ride through, ancillary services (voltage and frequency). It insists on the possibilities in terms of control laws for variable speed wind turbines. (author)
Energy Technology Data Exchange (ETDEWEB)
Laverdure, N
2005-12-15
Wind energy is now an energy that can not be ignored. Because of intrinsic characteristics (scattered primary energy, generators with different technologies, use of power electronics interface), wind energy system integration in distribution grids leads to real problems in terms of impacts. With recent standard changes, it is necessary to study the possibilities of each technology of wind turbines to answer or not to these new constraints. This PhD thesis focuses on a comparison of the main present wind turbines concerning three points of discussion: energy quality, fault ride through, ancillary services (voltage and frequency). It insists on the possibilities in terms of control laws for variable speed wind turbines. (author)
Directory of Open Access Journals (Sweden)
Dan Wang
2016-04-01
Full Text Available In recent years, the increasing penetration level of wind energy into power systems has brought new issues and challenges. One of the main concerns is the issue of dynamic response capability during outer disturbance conditions, especially the fault-tolerance capability during asymmetrical faults. In order to improve the fault-tolerance and dynamic response capability under asymmetrical grid fault conditions, an optimal integrated control scheme for the grid-side voltage-source converter (VSC of direct-driven permanent magnet synchronous generator (PMSG-based wind turbine systems is proposed in this paper. The optimal control strategy includes a main controller and an additional controller. In the main controller, a double-loop controller based on differential flatness-based theory is designed for grid-side VSC. Two parts are involved in the design process of the flatness-based controller: the reference trajectories generation of flatness output and the implementation of the controller. In the additional control aspect, an auxiliary second harmonic compensation control loop based on an improved calculation method for grid-side instantaneous transmission power is designed by the quasi proportional resonant (Quasi-PR control principle, which is able to simultaneously restrain the second harmonic components in active power and reactive power injected into the grid without the respective calculation for current control references. Moreover, to reduce the DC-link overvoltage during grid faults, the mathematical model of DC-link voltage is analyzed and a feedforward modified control factor is added to the traditional DC voltage control loop in grid-side VSC. The effectiveness of the optimal control scheme is verified in PSCAD/EMTDC simulation software.
DEFF Research Database (Denmark)
Li, H.; Ye, R.; Han, L.
2010-01-01
In order to entirely analyze the transient performances of a grid-connected doubly fed induction generator (DFIG) wind turbine under the different operational states, based on the transient models of DFIG, a two-mass wind turbine electrical equivalent model considering the torsional flexibility o...
Kirmani, Sheeraz; Kumar, Brijesh
2018-01-01
“Electric Power Quality (EPQ) is a term that refers to maintaining the near sinusoidal waveform of power distribution bus voltages and currents at rated magnitude and frequency”. Today customers are more aware of the seriousness that the power quality possesses, this prompt the utilities to assure good quality of power to their customer. The power quality is basically customer centric. Increased focus of utilities toward maintaining reliable power supply by employing power quality improvement tools has reduced the power outages and black out considerably. Good power quality is the characteristic of reliable power supply. Low power factor, harmonic pollution, load imbalance, fast voltage variations are some common parameters which are used to define the power quality. If the power quality issues are not checked i.e. the parameters that define power quality doesn't fall within the predefined standards than it will lead into high electricity bill, high running cost in industries, malfunctioning of equipments, challenges in connecting renewable. Capacitor banks, FACTS devices, harmonic filters, SVC’s (static voltage compensators), STATCOM (Static-Compensator) are the solutions to achieve the power quality. The performance of Wind turbine generators is affected by poor quality power, at the same time these wind power generating plant affects the power quality negatively. This paper presents the STATCOM-BESS (battery energy storage system) system and studies its impact on the power quality in a system which consists of wind turbine generator, non linear load, hysteresis controller for controlling the operation of STATCOM and grid. The model is simulated in the MATLAB/Simulink. This scheme mitigates the power quality issues, improves voltage profile and also reduces harmonic distortion of the waveforms. BESS level out the imbalances caused in real power due to intermittent nature of wind power available due to varying wind speeds.
Grids for Kids gives next-generation IT an early start
2008-01-01
Last week, the third in a growing series of Grids for Kids days was held at CERN, the European Organisation for Nuclear Research, involving children aged ten to twelve in games, tours and interactive presentations that introduced grid computing as a tool for researchers in everything from high energy physics to climate studies and genomics.
Modelling and Analysis of DFIG Wind Turbine Harmonics Generated in Grids
A.Chilambuchelvan; B.BabyPriya,
2010-01-01
In this paper an analytic technique for modelling harmonics is proposed for a DFIG wind turbine connected to the grid. An algorithm based on Hilbert transform for the analysis of harmonics in power systems isdeveloped. The simulation results prove the effectiveness of the Hilbert Transform (HT) for power harmonic analysis in DFIG wind turbine connected to a grid.
DEFF Research Database (Denmark)
Rodriguez, Pedro; Luna, Alvaro; Medeiros, G.
2010-01-01
This paper explores different strategies to set the reference current of a STATCOM under unbalanced grid voltage conditions. The aim of the proposed control strategies is to provide a set of reactive current references to be injected by the STATCOM under unbalanced grid faults. Their performance,...
MFE revisited : part 1: adaptive grid-generation using the heat equation
Zegeling, P.A.
1996-01-01
In this paper the moving-nite-element method (MFE) is used to solve the heat equation, with an articial time component, to give a non-uniform (steady-state) grid that is adapted to a given prole. It is known from theory and experiments that MFE, applied to parabolic PDEs, gives adaptive grids which
DEFF Research Database (Denmark)
Guo, Yougui; Zeng, Ping; Li, Lijuan
2011-01-01
Virtual flux oriented direct power control (VFDPC) is combined space vector modulation (SVM) with PI of DC-link voltage, active power and reactive power to control the grid side converter in wind power generation system in this paper. VFDPC has reached good performances with PLL (phase lock loop......, LCL filter, transformer grid, and control parts, such as PI controllers of DC-link voltage, active power, reactive power, and SVM, and so on. The simulation results have verified that the control strategy is feasible to fit for control of gird currents, active power, reactive power and DC-link voltage...
Research on DC Micro-grid system of photovoltaic power generation
Zheng, Yiming; Wang, Xiaohui
2018-01-01
The use of energy has become a topic of concern, the demand of people for power grows in number or quantity with the development of economy. It is necessary to consider using new forms of power supply-microgrid system for distributed power supply. The power supply mode can not only effectively solve the problem of excessive line loss in the large power grid, but also can increase the reliability of the power supply, and is economical and environmental friendly. With the increasing of DC loads, in order to improve the utilization efficiency, the DC microgrid power supply problems are begin to be researched and integrated with the renewable energy sources. This paper researched the development of microgrid, compared AC microgrid with DC microgrid, summarized the distribution of DC bus voltage level, the DC microgrid network form, the control mode and the main power electronics elements of DC microgrid of photovoltaic power generation system. Today, the DC microgrid system is still in the development stage without uniform voltage level standard, however, it will come into service in the future.
Voltage Control Scheme with Distributed Generation and Grid Connected Converter in a DC Microgrid
Directory of Open Access Journals (Sweden)
Jong-Chan Choi
2014-10-01
Full Text Available Direct Current (DC microgrids are expected to become larger due to the rapid growth of DC energy sources and power loads. As the scale of the system expends, the importance of voltage control will be increased to operate power systems stably. Many studies have been performed on voltage control methods in a DC microgrid, but most of them focused only on a small scale microgrid, such as a building microgrid. Therefore, a new control method is needed for a middle or large scale DC microgrid. This paper analyzes voltage drop problems in a large DC microgrid and proposes a cooperative voltage control scheme with a distributed generator (DG and a grid connected converter (GCC. For the voltage control with DGs, their location and capacity should be considered for economic operation in the systems. Accordingly, an optimal DG allocation algorithm is proposed to minimize the capacity of a DG for voltage control in DC microgrids. The proposed methods are verified with typical load types by a simulation using MATLAB and PSCAD/EMTDC.
A multi-objective control strategy for grid connection of DG (distributed generation) resources
Energy Technology Data Exchange (ETDEWEB)
Pouresmaeil, Edris; Montesinos-Miracle, Daniel; Bergas-Jane, Joan [Centre d' Innovacio Tecnologica en Convertidors Estatics i Accionaments (CITCEA-UPC), Departament d' Enginyeria Electrica, Universitat Politecnica de Catalunya, ETS d' Enginyeria Industrial de Barcelona (Spain); Gomis-Bellmunt, Oriol [Centre d' Innovacio Tecnologica en Convertidors Estatics i Accionaments (CITCEA-UPC), Departament d' Enginyeria Electrica, Universitat Politecnica de Catalunya, ETS d' Enginyeria Industrial de Barcelona (Spain); Catalonia Institute for Energy Research IREC, Barcelona (Spain)
2010-12-15
This paper presents a flexible control technique for connection of DG (distributed generation) resources to distribution networks, especially during ride-through on faulty grid. This strategy is derived from the abc/{alpha}{beta} and {alpha}{beta}/dq transformations of the ac system variables. The active and reactive currents injected by the DG source are controlled in the synchronously rotating orthogonal dq reference frame. The transformed variables are used to control the VSI (voltage source inverter) which connects the DG to the distribution network. Using a P.L.L. (phase locked loop) in circuit of proposed control technique, the angle of positive sequence has been detected, in order to synchronize the currents to the distribution network. The proposed control technique has the capability of providing active and reactive powers and harmonic currents to nonlinear loads with a fast dynamic response. Simulation results and mathematical analysis have been completed in order to achieve a reduced THD (total harmonic distortion), increased power factor and compensated load's active and reactive powers. The analyses show the high performance of this control strategy in DG applications in comparison with other existing strategies. (author)
Multilevel quadrature of elliptic PDEs with log-normal diffusion
Harbrecht, Helmut
2015-01-07
We apply multilevel quadrature methods for the moment computation of the solution of elliptic PDEs with lognormally distributed diffusion coefficients. The computation of the moments is a difficult task since they appear as high dimensional Bochner integrals over an unbounded domain. Each function evaluation corresponds to a deterministic elliptic boundary value problem which can be solved by finite elements on an appropriate level of refinement. The complexity is thus given by the number of quadrature points times the complexity for a single elliptic PDE solve. The multilevel idea is to reduce this complexity by combining quadrature methods with different accuracies with several spatial discretization levels in a sparse grid like fashion.
DEFF Research Database (Denmark)
Tan, Jin; Wang, Xiao Ru; Chen, Zhe
2013-01-01
In order to study the stability of a grid-connected direct-drive permanent magnet synchronous generator (PMSG) wind turbine systems, this paper presents the modal analysis of a PMSG wind turbine system. A PMSG model suitable for small signal stability analysis is presented. The modal properties...... of a grid-connected PMSG wind turbine system are studied. Then the comprehensive impacts of the shaft model, shaft parameters, operation points and lengths of the transmission line on the modal characteristic of the system are investigated by the eigenvalue analysis method. Meanwhile, the corresponding...... analysis. It offers a better understanding about the essence of the stability of grid-connected PMSG wind turbine system....
AUTHOR|(CDS)2082958; Hessey, Nigel
Due to the increasing demands of high energy physics experiments there is a need for particle detectors which enable high precision measurements. In this regard, the GridPix detector is a novel detector concept which combines the benefits of a pixel chip with an integrated gas amplification structure. The resulting unit is a detector sensitive to single electrons with a great potential for particle tracking and energy loss measurements. This thesis is focusing on the development of a new generation of GridPix detectors based on the Timepix3 chip, which implements a high resolution Time to Digital Converter (TDC) in each pixel. After an introductory chapter describing the motivation behind GridPix, the manuscript presents the physics of gaseous detectors in chapter 2 along with the gaseous detectors used for particle tracking in chapter 3. Chapters 4 and 5 are focusing on the tracking performance of GridPix detectors. Chapter 4 presents results obtained with a GridPix detector based on a small scale prototy...
Kammoun, Soulaymen; Sallem, Souhir; Ben Ali Kammoun, Mohamed
2017-11-01
The aim of this study is to enhance DFIG based Wind Energy Conversion Systems (WECS) dynamics during grid coupling. In this paper, a system modelling and a starting/coupling procedure for this generator to the grid are proposed. The proposed non-linear system is a variable structure system (VSS) and has two different states, before and after coupling. So, two different state models are given to the system to analyse transient stability during the coupling. The given model represents well the transient state of the machine, through which, a behaviour assessment of the generator before, during and after connection is given based on simulation results. For this, a 300 kW DFIG based wind generation system model was simulated on the Matlab/SIMULINK environment. We judge the proposed procedure to be practical, smooth and stability improved.
MFE revisited : part 1: adaptive grid-generation using the heat equation
Zegeling, P.A.
1996-01-01
In this paper the moving-nite-element method (MFE) is used to solve the heat equation, with an articial time component, to give a non-uniform (steady-state) grid that is adapted to a given prole. It is known from theory and experiments that MFE, applied to parabolic PDEs, gives adaptive grids which satisfy an equidistribution type law. This property is used to create non-uniform nite-element grids that are dictated by second-order derivatives of the solution. The proposed procedure could be u...
Elliptic Determinantal Processes and Elliptic Dyson Models
Katori, Makoto
2017-10-01
We introduce seven families of stochastic systems of interacting particles in one-dimension corresponding to the seven families of irreducible reduced affine root systems. We prove that they are determinantal in the sense that all spatio-temporal correlation functions are given by determinants controlled by a single function called the spatio-temporal correlation kernel. For the four families {A}_{N-1}, {B}_N, {C}_N and {D}_N, we identify the systems of stochastic differential equations solved by these determinantal processes, which will be regarded as the elliptic extensions of the Dyson model. Here we use the notion of martingales in probability theory and the elliptic determinant evaluations of the Macdonald denominators of irreducible reduced affine root systems given by Rosengren and Schlosser.
Directory of Open Access Journals (Sweden)
Soedibyo
2016-01-01
Full Text Available Photovoltaic and wind are renewable energy resources that widely used and grow rapidly in fulfilling electricity demand. Powers from both technologies depend on sunlight intensity and wind speed. For small scale power generation, DC voltage from both technologies is low and requires step-up converter to raise DC voltage ratio before converted into AC voltage. To optimize this system, step-up converter must have high ratio and efficiency to a distance of wide voltage input. This paper proposed an operation simulation and arrangement of DC-DC converter along with DC-AC from hybrid source PV-Wind which integrated to grid utilities without using storage device. High Gain Integrated Cascade Boost (HGICB is DC-DC converter that has quadratic voltage ratio and used in this research. Then DC link connected to Voltage Source Inverter (VSI which interconnected with utility grid and controlled by current control method. The total installed capacity of hybrid source is 4.4 kW. Wind turbine uses PMSG along with full bridge rectifier. To maximize and stabilize the generated power, MPPT fuzzy is used. Result from the simulation shows that converter capable to maintain maximum power whether from PV and wind turbine which canalized to utility grid in various irradiation condition, wind speed, and grid load alteration.
Croatia's rural areas - renewable energy based electricity generation for isolated grids
Directory of Open Access Journals (Sweden)
Protic Sonja Maria
2014-01-01
Full Text Available Several Western Balkan states face the consequences of the Yugoslavian war, which left hometowns with dilapidated electricity grid connections, a high average age of power plant capacities and low integration of renewable energy sources, grid bottlenecks and a lack of competition. In order to supply all households with electricity, UNDP Croatia did a research on decentralized supply systems based on renewable energy sources. Decentralized supply systems offer cheaper electricity connections and provide faster support to rural development. This paper proposes a developed methodology to financially compare isolated grid solutions that primarily use renewable energies to an extension of the public electricity network to small regions in Croatia. Isolated grid supply proves to be very often a preferable option. Furthermore, it points out the lack of a reliable evaluation of non-monetizable aspects and promotes a new interdisciplinary approach.
A Method for a Multi-Platform Approach to Generate Gridded Surface Evaporation
Badger, A.; Livneh, B.; Small, E. E.; Abolafia-Rosenzweig, R.
2017-12-01
Evapotranspiration is an integral component of the surface water balance. While there are many estimates of evapotranspiration, there are fewer estimates that partition evapotranspiration into evaporation and transpiration components. This study aims to generate a CONUS-scale, observationally-based soil evaporation dataset by using the time difference of surface soil moisture by Soil Moisture Active Passive (SMAP) satellite with adjustments for transpiration and a bottom flux out of the surface layer. In concert with SMAP, the Moderate-Resolution Imaging Spectroradiometer (MODIS) satellite, North American Land Data Assimilation Systems (NLDAS) and the Hydrus-1D model are used to fully analyze the surface water balance. A biome specific estimate of the total terrestrial ET is calculated through a variation of the Penman-Monteith equation with NLDAS forcing and NLDAS Noah Model output for meteorological variables. A root density restriction and SMAP-based soil moisture restriction are applied to obtain terrestrial transpiration estimates. By forcing Hydrus-1D with NLDAS meteorology and our terrestrial transpiration estimates, an estimate of the flux between the soil surface and root zone layers (qbot) will dictate the proportion of water that is available for soil evaporation. After constraining transpiration and the bottom flux from the surface layer, we estimate soil evaporation as the residual of the surface water balance. Application of this method at Fluxnet sites shows soil evaporation estimates of approximately 03 mm/day and less than ET estimates. Expanding this methodology to produce a gridded product for CONUS, and eventually a global-scale product, will enable a better understanding of water balance processes and contribute a dataset to validate land-surface model's surface flux processes.
Directory of Open Access Journals (Sweden)
Marian Sobierajski
2015-12-01
Full Text Available The paper discusses the performance of the 15 kW photovoltaic micro installation located on the roof of building D-1 of the Faculty of Electrical Engineering at Wroclaw University of Technology. The micro installation is connected to the low voltage grid, which supplies the new, air-conditioned building D-20. The paper discusses the energy and power generation output in yearly, monthly, and daily intervals. The micro installation’s output in the summer morning peaks is compared with the daily wind generation against the background of the demand, generation, regulation reserve, and overhauls in the National Power System.
International Nuclear Information System (INIS)
Aghajani, G.R.; Shayanfar, H.A.; Shayeghi, H.
2015-01-01
Highlights: • Using DRPs to cover the uncertainties resulted from power generation by WT and PV. • Proposing the use of price-offer packages and amount of DR for implement DRPs. • Considering a multi-objective scheduling model and use of MOPSO algorithm. - Abstract: In this paper, a multi-objective energy management system is proposed in order to optimize micro-grid (MG) performance in a short-term in the presence of Renewable Energy Sources (RESs) for wind and solar energy generation with a randomized natural behavior. Considering the existence of different types of customers including residential, commercial, and industrial consumers can participate in demand response programs. As with declare their interruptible/curtailable demand rate or select from among different proposed prices so as to assist the central micro-grid control in terms of optimizing micro-grid operation and covering energy generation uncertainty from the renewable sources. In this paper, to implement Demand Response (DR) schedules, incentive-based payment in the form of offered packages of price and DR quantity collected by Demand Response Providers (DRPs) is used. In the typical micro-grid, different technologies including Wind Turbine (WT), PhotoVoltaic (PV) cell, Micro-Turbine (MT), Full Cell (FC), battery hybrid power source and responsive loads are used. The simulation results are considered in six different cases in order to optimize operation cost and emission with/without DR. Considering the complexity and non-linearity of the proposed problem, Multi-Objective Particle Swarm Optimization (MOPSO) is utilized. Also, fuzzy-based mechanism and non-linear sorting system are applied to determine the best compromise considering the set of solutions from Pareto-front space. The numerical results represented the effect of the proposed Demand Side Management (DSM) scheduling model on reducing the effect of uncertainty obtained from generation power and predicted by WT and PV in a MG.
User centric monitoring (UCM) information service for the next generation of Grid-enabled scientists
International Nuclear Information System (INIS)
Alexander, D A; Li, C; Lauret, J; Fine, V
2008-01-01
Nuclear and high-energy physicists routinely execute data processing and data analysis jobs on a Grid and need to be able to easily and remotely monitor the execution of these jobs. Existing Grid monitoring tools provide abundant information about the whole system, but are geared towards production jobs and well suited for Grid administrators, while the information tailored towards an individual user is not readily available in a user-friendly and user-centric way. Such User Centric information includes monitoring information such as the status of the submitted job, queue position, time of the start/finish, percentage of being done, error messages, standard output, and reasons for failure. We proposed to develop a framework based on Grid service technology that allows scientists to track and monitor their jobs easily from a user-centric view. The proposed framework aims to be flexible so that it can be applied by any Grid Virtual Organization (VO) with various ways of collecting the user-centric job monitoring information built into the framework. Furthermore, the framework provides a rich and reusable set of methods of presenting the information to the user from within a Web browser and other clients. In this presentation, we will give an architectural overview of the UCM service, show an example implementation in the RHIC/STAR experiment context and discuss limitations and future collaborative work
User centric monitoring (UCM) information service for the next generation of Grid-enabled scientists
Energy Technology Data Exchange (ETDEWEB)
Alexander, D A; Li, C [Tech-X Corporation, 5621 Arapahoe Avenue Suite A, Boulder, CO 80303 (United States); Lauret, J; Fine, V [Physics Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)], E-mail: alexanda@txcorp.com
2008-07-15
Nuclear and high-energy physicists routinely execute data processing and data analysis jobs on a Grid and need to be able to easily and remotely monitor the execution of these jobs. Existing Grid monitoring tools provide abundant information about the whole system, but are geared towards production jobs and well suited for Grid administrators, while the information tailored towards an individual user is not readily available in a user-friendly and user-centric way. Such User Centric information includes monitoring information such as the status of the submitted job, queue position, time of the start/finish, percentage of being done, error messages, standard output, and reasons for failure. We proposed to develop a framework based on Grid service technology that allows scientists to track and monitor their jobs easily from a user-centric view. The proposed framework aims to be flexible so that it can be applied by any Grid Virtual Organization (VO) with various ways of collecting the user-centric job monitoring information built into the framework. Furthermore, the framework provides a rich and reusable set of methods of presenting the information to the user from within a Web browser and other clients. In this presentation, we will give an architectural overview of the UCM service, show an example implementation in the RHIC/STAR experiment context and discuss limitations and future collaborative work.
ICT Requirements and Challenges for Provision of Grid Services from Renewable Generation Plants
DEFF Research Database (Denmark)
Shahid, Kamal; Olsen, Rasmus Løvenstein; Petersen, Lennart
2018-01-01
The penetration of renewable energy into the electricity supply mix necessitates the traditional power grid to become more resilient, reliable and efficient. One way of ensuring this is to require renewable power plants to have similar regulating properties as conventional power plants...... applications – in terms of data payloads, sampling rates, latency and reliability. Therefore, this paper presents a brief survey on the control and communication architectures for controlling renewable power plants in the future power grid, including the communication network technologies, requirements...... and to coordinate their grid support services (GSS) as well. Among other requirements, the coordination of GSS will highly depend on the communication between renewable plants and system operators’ control rooms, thereby imposing high responsibility on the under lying communication infrastructure. Despite...
Triaxiality in elliptical galaxies
Energy Technology Data Exchange (ETDEWEB)
Benacchio, L; Galletta, G [Padua Univ. (Italy). Ist. di Astronomia
1980-12-01
The existence of a triaxial shape for elliptical galaxies has been considered in recent years to explain the new kinematical and geometrical findings, i.e. (a) the low rotation/velocity dispersion ratio found also in some flat systems, (b) the presence of twisting in the isophotes, (c) the recently found correlation between maximum twisting and maximum flattening, (d) the presence of rotation along the minor axis. A simple geometrical model of elliptical galaxies having shells with different axial ratios c/a, b/a has been produced to interpret three fundamental key-features of elliptical galaxies: (i) the distribution of the maximum flattening observed; (ii) the percentage of ellipticals showing twisting; and (iii) the correlation between maximum twisting and maximum flattening. The model has been compared with observational data for 348 elliptical systems as given by Strom and Strom. It is found that a triaxial ellipsoid with coaxial shells having axial ratios c/a and b/a mutually dependent in a linear way can satisfy the observations.
DEFF Research Database (Denmark)
Yao, Jun; Zhou, Te; Hu, Weihao
2015-01-01
This article presents an enhanced control strategy for a direct-driven permanent synchronous generator based wind-power generation system with a flywheel energy storage unit. The behaviors of the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit under......, the DC-link voltage oscillations can be effectively suppressed during the unbalanced grid fault by controlling the flywheel energy storage unit. Furthermore, a proportional–integral-resonant controller is designed for the flywheel motor to eliminate the oscillations in the DC-link voltage. Finally......, the proposed coordinated control strategy for the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit has been validated by the simulation results of a 1-MW direct-driven permanent magnet synchronous generator wind power generation system with a flywheel energy...
Ellipticity dependence of the near-threshold harmonics of H2 in an elliptical strong laser field.
Yang, Hua; Liu, Peng; Li, Ruxin; Xu, Zhizhan
2013-11-18
We study the ellipticity dependence of the near-threshold (NT) harmonics of pre-aligned H2 molecules using the time-dependent density functional theory. The anomalous maximum appearing at a non-zero ellipticity for the generated NT harmonics can be attributed to multiphoton effects of the orthogonally polarized component of the elliptical driving laser field. Our calculation also shows that the structure of the bound-state, such as molecular alignment and bond length, can be sensitively reflected on the ellipticity dependence of the near-threshold harmonics.
Newton flows for elliptic functions: A pilot study
Twilt, F.; Helminck, G.F.; Snuverink, M.; van den Brug, L.
2008-01-01
Elliptic Newton flows are generated by a continuous, desingularized Newton method for doubly periodic meromorphic functions on the complex plane. In the special case, where the functions underlying these elliptic Newton flows are of second-order, we introduce various, closely related, concepts of
The GLOBE-Consortium: The Erasmus Computing Grid and The Next Generation Genome Viewer
T.A. Knoch (Tobias)
2005-01-01
markdownabstractThe Set-Up of the 20 Teraflop Erasmus Computing Grid: To meet the enormous computational needs of live-science research as well as clinical diagnostics and treatment the Hogeschool Rotterdam and the Erasmus Medical Center are currently setting up one of the largest desktop
Short circuit behavior of distribution grids with a large share of distributied generation units
Coster, E.J.; Karaliolios, P.; Xyngi, I.; Slootweg, J.G.; Popov, M.; Kling, W.L.; Sluis, van der L.
2011-01-01
increasing rapidly. Most of these units are connected to the distribution grid. With the increasing penetration level the impact of these units on for instance power flows, fault levels and protective systems cannot be neglected anymore. To allow an increasing penetration level of DG without causing
Generation of a Composite Grid for Turbine Flows and Consideration of a Numerical Scheme.
1986-11-01
section (a) Grids on blade-to-blade surface. WIWcr fb eatv r.t35eaiy aiso lsnbaet-baesrae Figure~~~~~~~~ 4. "eo’ycotuso.4det-ld urae(rmtre-ieso5 .2lcdcmp
RECTC/RECTCF, 2. Order Elliptical Partial Differential Equation, Arbitrary Boundary Conditions
International Nuclear Information System (INIS)
Hackbusch, W.
1983-01-01
1 - Description of problem or function: A general linear elliptical second order partial differential equation on a rectangle with arbitrary boundary conditions is solved. 2 - Method of solution: Multi-grid iteration
Kato, Takeyoshi; Sugimoto, Hiroyuki; Suzuoki, Yasuo
We established a procedure for estimating regional electricity demand and regional potential capacity of distributed generators (DGs) by using a grid square statistics data set. A photovoltaic power system (PV system) for residential use and a co-generation system (CGS) for both residential and commercial use were taken into account. As an example, the result regarding Aichi prefecture was presented in this paper. The statistical data of the number of households by family-type and the number of employees by business category for about 4000 grid-square with 1km × 1km area was used to estimate the floor space or the electricity demand distribution. The rooftop area available for installing PV systems was also estimated with the grid-square statistics data set. Considering the relation between a capacity of existing CGS and a scale-index of building where CGS is installed, the potential capacity of CGS was estimated for three business categories, i.e. hotel, hospital, store. In some regions, the potential capacity of PV systems was estimated to be about 10,000kW/km2, which corresponds to the density of the existing area with intensive installation of PV systems. Finally, we discussed the ratio of regional potential capacity of DGs to regional maximum electricity demand for deducing the appropriate capacity of DGs in the model of future electricity distribution system.
Prospect of solar-PV/biogas/diesel generator hybrid energy system of an off-grid area in Bangladesh
Mandal, Soumya; Yasmin, Hosna; Sarker, M. R. I.; Beg, M. R. A.
2017-12-01
The study presents an analysis and suggests about how renewable sources of energy can be an alternative option to produce electricity in an off-grid area. A case study is done by surveying 235 households in an off-grid area. Techno-economic analysis of the hybrid energy system is employed by using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Four solar-PV modules (each of 1kW), two biogas generators (each of 3kW), three diesel generators (each of 5kW), five batteries (each of 160 Ah) and 5kW converter is found to be the best configuration in terms of Cost of Energy (COE), environmental conditions and Renewable Fraction (RF). The Cost of Energy (COE), Net Present Cost (NPC), capital cost of this configuration is found BDT15.382, BDT10007224, and BDT2582433 respectively. The renewable fraction of this system is found 75% which indicates a lower emission compared with thegrid based system and stand-alone diesel system. Although the COE is higher than grid electricity, this system offers a cheaper option than using kerosene oil and solar home systems (SHSs).
Jaithwa, Ishan
Deployment of smart grid technologies is accelerating. Smart grid enables bidirectional flows of energy and energy-related communications. The future electricity grid will look very different from today's power system. Large variable renewable energy sources will provide a greater portion of electricity, small DERs and energy storage systems will become more common, and utilities will operate many different kinds of energy efficiency. All of these changes will add complexity to the grid and require operators to be able to respond to fast dynamic changes to maintain system stability and security. This thesis investigates advanced control technology for grid integration of renewable energy sources and STATCOM systems by verifying them on real time hardware experiments using two different systems: d SPACE and OPAL RT. Three controls: conventional, direct vector control and the intelligent Neural network control were first simulated using Matlab to check the stability and safety of the system and were then implemented on real time hardware using the d SPACE and OPAL RT systems. The thesis then shows how dynamic-programming (DP) methods employed to train the neural networks are better than any other controllers where, an optimal control strategy is developed to ensure effective power delivery and to improve system stability. Through real time hardware implementation it is proved that the neural vector control approach produces the fastest response time, low overshoot, and, the best performance compared to the conventional standard vector control method and DCC vector control technique. Finally the entrepreneurial approach taken to drive the technologies from the lab to market via ORANGE ELECTRIC is discussed in brief.
RF generator interlock by plasma grid bias current - An alternate to Hα interlock
Bandyopadhyay, M.; Gahlaut, A.; Yadav, R. K.; Pandya, K.; Tyagi, H.; Vupugalla, M.; Bhuyan, M.; Bhagora, J.; Chakraborty, A.
2017-08-01
ROBIN is inductively coupled plasma (ICP) based negative hydrogen ion source, operated with a 100kW, 1MHz Tetrode based RF generator (RFG). Inductive plasma ignition by the RFG in ROBIN is associated with electron seeding by a hot filament and a gas puff. RFG is triggered by the control system to deliver power just at the peak pressure of the gas puff. Once plasma is ignited due to proper impedance matching, a bright light, dominated by Hα (˜656nm wavelength) radiation is available inside RF driver which is used as a feedback signal to the RFG to continue its operation. If impedance matching is not correct, plasma is not produced due to lack of power coupling and bright light is not available. During such condition, reflected RF power may damage the RFG. Therefore, to protect the RFG, it needs to be switched off automatically within 200ms by the control system in such cases. This plasma light based RFG interlock is adopted from BATMAN ion source. However, in case of vacuum immersed RF ion source in reactor grade NBI system, such plasma light based interlock may not be feasible due to lack of adequate optical fiber interfaces. In reactor grade NBI system, neutron and gamma radiations have impact on materials which may lead to frequent maintenance and machine down time. The present demonstration of RFG interlock by Bias Current (BC) in ROBIN testbed gives an alternate option in this regard. In ROBIN, a bias plate (BP) is placed in the plasma chamber near the plasma grid (PG). BP is electrically connected to the plasma chamber wall of the ion source and PG is isolated from the wall. A high current ˜85 A direct current (DC) power supply of voltage in the range of 0 - 33V is connected between the PG and the BP in such a way that PG can be biased positively with respect to the BP or plasma chamber. This arrangement is actually made to absorb electrons and correspondingly reduce co-extracted electron current during beam extraction. However, in case of normal plasma
Energy Technology Data Exchange (ETDEWEB)
Hoefer, Reinhard [Process Management Consulting GmbH, Koeln (Germany)
2009-07-15
The deregulation of the energy market has had its effects on power generation, metering and control. New solutions must be developed for ensuring future power supply. Smart grids are an option for integrating the various sectors. (orig.)
Superconducting elliptical cavities
Sekutowicz, J K
2011-01-01
We give a brief overview of the history, state of the art, and future for elliptical superconducting cavities. Principles of the cell shape optimization, criteria for multi-cell structures design, HOM damping schemes and other features are discussed along with examples of superconducting structures for various applications.
Global Renewable Energy-Based Electricity Generation and Smart Grid System for Energy Security
Islam, M. A.; Hasanuzzaman, M.; Rahim, N. A.; Nahar, A.; Hosenuzzaman, M.
2014-01-01
Energy is an indispensable factor for the economic growth and development of a country. Energy consumption is rapidly increasing worldwide. To fulfill this energy demand, alternative energy sources and efficient utilization are being explored. Various sources of renewable energy and their efficient utilization are comprehensively reviewed and presented in this paper. Also the trend in research and development for the technological advancement of energy utilization and smart grid system for fu...
Spatial scan statistics using elliptic windows
DEFF Research Database (Denmark)
Christiansen, Lasse Engbo; Andersen, Jens Strodl; Wegener, Henrik Caspar
2006-01-01
The spatial scan statistic is widely used to search for clusters. This article shows that the usually applied elimination of secondary clusters as implemented in SatScan is sensitive to smooth changes in the shape of the clusters. We present an algorithm for generation of a set of confocal elliptic...
DEFF Research Database (Denmark)
Yao, Jun; Yu, Mengting; Hu, Weihao
2016-01-01
This paper investigates an improved control strategy for a doubly-fed induction generator (DFIG) based wind-power generation system with series grid-side converter (SGSC) under network unbalance and harmonic grid voltage distortion conditions. The integrated mathematical modeling of the DFIG system...... with SGSC is established by taking both the negative-sequence and harmonic components of the grid voltages into consideration with multiple synchronous rotating reference frames. Under network unbalance and harmonic distortion situations, stator voltage can be kept symmetrical and sinusoidal by the control...
Directory of Open Access Journals (Sweden)
Mahdi Majidniya
2017-01-01
Full Text Available An Internal Reforming Solid Oxide Fuel Cell (IRSOFC is modeled thermodynamically; a Horizontal Axis Wind Turbine (HAWT is designed; the combined IRSOFC-HAWT system should create a reliable source of electricity for the demand of a village located in Manjil, Iran. The output power of HAWT is unstable, but by controlling the fuel rate for the IRSOFC it is possible to have a stable power output from the combined system. When the electricity demand is over the peak or the wind speed is low/unstable/significantly high, the generated power may not be sufficient. To solve this problem, two scenarios are considered: connecting to the grid or using a Pumped Hydro Storage (PHS. For the second scenario, the extra produced electricity is saved when the production is more than demand and can be used when the extra power is needed. The economic analysis is done based on the economic conditions in Iran. The results will show a period of return about 9.5 and 13 years with the levelized cost of electricity about 0.0747 and 0.0882 $/kWh for the first and second scenarios, respectively. Furthermore, effects of some parameters such as the electricity price and the real interest rate are discussed.
Cardenas, Jesus Alvaro
An energy and environmental crisis will emerge throughout the world if we continue with our current practices of generation and distribution of electricity. A possible solution to this problem is based on the Smart grid concept, which is heavily influenced by Information and Communication Technology (ICT). Although the electricity industry is mostly regulated, there are global models used as roadmaps for Smart Grids' implementation focusing on technologies and the basic generation-distribution-transmission model. This project aims to further enhance a business model for a future global deployment. It takes into consideration the many factors interacting in this energy provision process, based on the diffusion of technologies and literature surveys on the available documents in the Internet as well as peer-reviewed publications. Tariffs and regulations, distributed energy generation, integration of service providers, consumers becoming producers, self-healing devices, and many other elements are shifting this industry into a major change towards liberalization and deregulation of this sector, which has been heavily protected by the government due to the importance of electricity for consumers. We propose an Energy Management Business Model composed by four basic elements: Supply Chain, Information and Communication Technology (ICT), Stakeholders Response, and the resulting Green Efficient Energy (GEE). We support the developed model based on the literature survey, we support it with the diffusion analysis of these elements, and support the overall model with two surveys: one for peers and professionals, and other for experts in the field, based on the Smart Grid Carnegie Melon Maturity Model (CMU SEI SGMM). The contribution of this model is a simple path to follow for entities that want to achieve environmental friendly energy with the involvement of technology and all stakeholders.
Directory of Open Access Journals (Sweden)
Adikanda Parida
2016-12-01
Full Text Available In this paper, a wind power generation scheme using a grid connected doubly fed induction generator (DFIG augmented with solar PV has been proposed. A reactive power-based rotor speed and position estimation technique with reduced machine parameter sensitivity is also proposed to improve the performance of the DFIG controller. The estimation algorithm is based on model reference adaptive system (MRAS, which uses the air gap reactive power as the adjustable variable. The overall generation reliability of the wind energy conversion system can be considerably improved as both solar and wind energy can supplement each other during lean periods of either of the sources. The rotor-side DC-link voltage and active power generation at the stator terminals of the DFIG are maintained constant with minimum storage battery capacity using single converter arrangement without grid-side converter (GSC. The proposed scheme has been simulated and experimentally validated with a practical 2.5 kW DFIG using dSPACE CP1104 module which produced satisfactory results.
Almasoudi, Fahad M.; Alatawi, Khaled S.; Matin, Mohammad
2017-08-01
Implementation of transformerless inverters in PV grid-tied system offer great benefits such as high efficiency, light weight, low cost, etc. Most of the proposed transformerless inverters in literature are verified for only real power application. Currently, international standards such as VDE-AR-N 4105 has demanded that PV grid-tied inverters should have the ability of controlling a specific amount of reactive power. Generation of reactive power cannot be accomplished in single phase transformerless inverter topologies because the existing modulation techniques are not adopted for a freewheeling path in the negative power region. This paper enhances a previous high efficiency proposed H6 trnasformerless inverter with SiC MOSFETs and demonstrates new operating modes for the generation of reactive power. A proposed pulse width modulation (PWM) technique is applied to achieve bidirectional current flow through freewheeling state. A comparison of the proposed H6 transformerless inverter using SiC MOSFETs and Si MOSFTEs is presented in terms of power losses and efficiency. The results show that reactive power control is attained without adding any additional active devices or modification to the inverter structure. Also, the proposed modulation maintains a constant common mode voltage (CM) during every operating mode and has low leakage current. The performance of the proposed system verifies its effectiveness in the next generation PV system.
Directory of Open Access Journals (Sweden)
Zhu Jun
2015-01-01
Full Text Available This paper reviews the present situation of the application of wind turbines generator system(WTGS at home and abroad, describes the strategic significance and the value of sustainable development of the wind power in the country, illustrates the problems, a variety of reasons and responses on large-scale off-grid of WTGS, compares the advantages and disadvantages of various methods, gives full consideration to the actual demand for WTGS works and characteristics and points out the further research.
Energy Technology Data Exchange (ETDEWEB)
Inoue, K [National Aerospace Laboratory, Tokyo (Japan)
1992-05-01
For the purpose of developing a fan for an engine with ultra-high by-pass ratio, the design code of three-dimensional cascade of blades based on the Navier-Stokes equation has already been developed. This paper describes a method created by calculation grids which are part of this design code. This method is to generate boundary fitted grids to calculate the flow field across a cascade of blades placed radially in the axially symmetric space between hub and casing. In this method, one-period domain of the cascade of blades is mapped on a box in computational space by a series of combined streching transformation and conformal mapping. The grid in physical space is then obtained by successive inverse conformal mapping on the grid points in computational space. The grid obtained in this method is H-type and has a periodicity which includes the inclination of grid lines at the periodic boundary. As an example of the grid generated by this method, grids for primary and secondary models of the fan with ultra-high by-pass ratio are shown. 6 refs., 12 figs.
Energy Technology Data Exchange (ETDEWEB)
Inoue, K [National Aerospace Laboratory, Tokyo (Japan)
1992-05-01
For the purpose of developing a fan for an engine with ultra-high by-pass ratio, the design code of three-dimensional cascade of blades based on the Navier-Stokes equation has already been developed. This paper describes a method created by calculation grids which are part of this design code. This method is to generate boundary fitted grids to calculate the flow field across a cascade of blades placed radially in the axially symmetric space between hub and casing. In this method, one-period domain of the cascade of blades is mapped on a box in computational space by a series of combined streching transformation and conformal mapping. The grid in physical space is then obtained by successive inverse conformal mapping on the grid points in computational space. The grid obtained in this method is H-type and has a periodicity which includes the inclination of grid lines at the periodic boundary. As an example of the grid generated by this method, grids for primary and secondary models of the fan with ultra-high by-pass ratio are shown. 6 refs., 12 figs.
Energy Technology Data Exchange (ETDEWEB)
Singh, Ruchi; Vyakaranam, Bharat GNVSR
2012-02-14
This document is one of a series of reports estimating the benefits of deploying technologies similar to those implemented on the Smart Grid Investment Grant (SGIG) projects. Four technical reports cover the various types of technologies deployed in the SGIG projects, distribution automation, demand response, energy storage, and renewables integration. A fifth report in the series examines the benefits of deploying these technologies on a national level. This technical report examines the impacts of addition of renewable resources- solar and wind in the distribution system as deployed in the SGIG projects.
Energy Technology Data Exchange (ETDEWEB)
Friedrich, Uwe
2011-07-01
In future, electricity grids will have to transport large quantities of electricity from renewable energy sources fed centrally and decentrally. Plus, we need greater reserves, storage facilities and flexibility in the electricity market due to the fluctuating supply. In the ''Modellstadt Mannheim'' project, a virtual energy marketplace is being developed for energy generators, consumers and grid operators. Customers can see the source and price of their electricity and influence them directly via the timing and extent of their consumption and the delivery from their own generation systems. This approach also includes gas, water and district heating. (orig.)
Next generation molten NaI batteries for grid scale energy storage
Small, Leo J.; Eccleston, Alexis; Lamb, Joshua; Read, Andrew C.; Robins, Matthew; Meaders, Thomas; Ingersoll, David; Clem, Paul G.; Bhavaraju, Sai; Spoerke, Erik D.
2017-08-01
Robust, safe, and reliable grid-scale energy storage continues to be a priority for improved energy surety, expanded integration of renewable energy, and greater system agility required to meet modern dynamic and evolving electrical energy demands. We describe here a new sodium-based battery based on a molten sodium anode, a sodium iodide/aluminum chloride (NaI/AlCl3) cathode, and a high conductivity NaSICON (Na1+xZr2SixP3-xO12) ceramic separator. This NaI battery operates at intermediate temperatures (120-180 °C) and boasts an energy density of >150 Wh kg-1. The energy-dense NaI-AlCl3 ionic liquid catholyte avoids lifetime-limiting plating and intercalation reactions, and the use of earth-abundant elements minimizes materials costs and eliminates economic uncertainties associated with lithium metal. Moreover, the inherent safety of this system under internal mechanical failure is characterized by negligible heat or gas production and benign reaction products (Al, NaCl). Scalability in design is exemplified through evolution from 0.85 to 10 Ah (28 Wh) form factors, displaying lifetime average Coulombic efficiencies of 99.45% and energy efficiencies of 81.96% over dynamic testing lasting >3000 h. This demonstration promises a safe, cost-effective, and long-lifetime technology as an attractive candidate for grid scale storage.
International Nuclear Information System (INIS)
Tarroja, Brian; AghaKouchak, Amir; Samuelsen, Scott
2016-01-01
Here we translate the impacts of climate change on hydropower generation, and discuss implications on greenhouse gas (GHG) emissions and operation in California. We integrate a model of major surface-water reservoirs with an electric grid dispatch model, and perturb it by projected runoff based on representative concentration pathways (RCP4.5 and RCP8.5). Results show that climate change and variability is expected to decrease the average annual hydropower generation by 3.1% under RCP4.5, but have negligible impact under the RCP8.5. Model simulations indicate more inflow, caused by more future extremes, in the future that does not necessarily translate to more energy production because of reservoir spillage of water. While overall volume of future available water for energy production may be similar or higher, the delivery of this volume is expected to be significantly more variable in the future climate than the historical average, which has many implications for hydropower generation. Our results show that the expected changes in future climate leads to increases in grid GHG emissions, load-following capacity, fuel usage, and costs for the RCP4.5 due to generation shortfall, and very slight increases in the same metrics for the RCP8.5 case due to variability causing decreased efficiencies in load-following power plants. - Highlights: • Climate change caused increased overall volume inflow levels to hydropower reservoirs. • Extreme precipitation events caused reservoir spillage and inability to fully use increased inflow. • Hydropower generation decreased for RCP 4.5 and remained similar to historical for RCP 8.5. • Increased climate variability caused decreased efficiencies in load-following power plants.
International Nuclear Information System (INIS)
Hou, Guofu; Sun, Honghang; Jiang, Ziying; Pan, Ziqiang; Wang, Yibo; Zhang, Xiaodan; Zhao, Ying; Yao, Qiang
2016-01-01
Graphical abstract: Comparison of life cycle GHG emissions of various power sources. - Highlights: • The LCA study of grid-connected PV generation with silicon solar modules in China has been performed. • The energy payback times range from 1.6 to 2.3 years. • The GHG emissions are in the range of 60.1–87.3 g-CO_2,eq/kW h. • The PV manufacturing process occupied about 85% or higher of total energy usage and total GHG emission. • The SoG-Si production process accounted for more than 35% of total energy consumption and GHG emissions. - Abstract: The environmental impacts of grid-connected photovoltaic (PV) power generation from crystalline silicon (c-Si) solar modules in China have been investigated using life cycle assessment (LCA). The life cycle inventory was first analyzed. Then the energy consumption and greenhouse gas (GHG) emission during every process were estimated in detail, and finally the life-cycle value was calculated. The results showed that the energy payback time (T_E_P_B_T) of grid-connected PV power with crystalline silicon solar modules ranges from 1.6 to 2.3 years, while the GHG emissions now range from 60.1 to 87.3 g-CO_2,eq/kW h depending on the installation methods. About 84% or even more of the total energy consumption and total GHG emission occupied during the PV manufacturing process. The solar grade silicon (SoG-Si) production is the most energy-consuming and GHG-emitting process, which accounts for more than 35% of the total energy consumption and the total GHG emission. The results presented in this study are expected to provide useful information to enact reasonable policies, development targets, as well as subsidies for PV technology in China.
Dynamic Modeling and Grid Interaction of a Tidal and River Generator
Energy Technology Data Exchange (ETDEWEB)
Muljadi, Eduard; Gevorgian, Vahan; Donegan, James; Marnagh, Cian; McEntee, Jarlath
2017-07-13
This presentation provides a high-level overview of the deployment of a river generator installed in a small system. The turbine dynamics of a river generator, electrical generator, and power converter are modeled in detail. Various simulations can be exercised, and the impact of different control algorithms, failures of power switches, and corresponding impacts can be examined.
Ellipticity of near-threshold harmonics from stretched molecules.
Li, Weiyan; Dong, Fulong; Yu, Shujuan; Wang, Shang; Yang, Shiping; Chen, Yanjun
2015-11-30
We study the ellipticity of near-threshold harmonics (NTH) from aligned molecules with large internuclear distances numerically and analytically. The calculated harmonic spectra show a broad plateau for NTH which is several orders of magnitude higher than that for high-order harmonics. In particular, the NTH plateau shows high ellipticity at small and intermediate orientation angles. Our analyses reveal that the main contributions to the NTH plateau come from the transition of the electron from continuum states to these two lowest bound states of the system, which are strongly coupled together by the laser field. Besides continuum states, higher excited states also play a role in the NTH plateau, resulting in a large phase difference between parallel and perpendicular harmonics and accordingly high ellipticity of the NTH plateau. The NTH plateau with high intensity and large ellipticity provides a promising manner for generating strong elliptically-polarized extreme-ultraviolet (EUV) pulses.
Anisotropic elliptic optical fibers
Kang, Soon Ahm
1991-05-01
The exact characteristic equation for an anisotropic elliptic optical fiber is obtained for odd and even hybrid modes in terms of infinite determinants utilizing Mathieu and modified Mathieu functions. A simplified characteristic equation is obtained by applying the weakly guiding approximation such that the difference in the refractive indices of the core and the cladding is small. The simplified characteristic equation is used to compute the normalized guide wavelength for an elliptical fiber. When the anisotropic parameter is equal to unity, the results are compared with the previous research and they are in close agreement. For a fixed value normalized cross-section area or major axis, the normalized guide wavelength lambda/lambda(sub 0) for an anisotropic elliptic fiber is small for the larger value of anisotropy. This condition indicates that more energy is carried inside of the fiber. However, the geometry and anisotropy of the fiber have a smaller effect when the normalized cross-section area is very small or very large.
Energy Technology Data Exchange (ETDEWEB)
Arifujjaman, Md.
2011-07-01
In order to recover the maximum energy from small scale wind turbine systems many parameters have to be controlled. The aim of this paper is to propose a control strategy for the grid connected PMG-based small wind turbine systems. A mathematical model of small wind turbine systems was developed and the system simulated. Results show demonstrated that the control strategy is highly efficient. Sure enough it reduces the dependence on system variables, diminishes the system complexity, its furling and maximum power point controllers are efficient and it provides a stable operation for multiple wind speeds. This study developed a modeling and control strategy which was proved to be feasible by simulation results.
Modelling and Analysis of Variable Speed Wind Turbines with Induction Generator during Grid Fault
DEFF Research Database (Denmark)
Bolik, Sigrid Mechthild
During recent years wind turbine technology has undergone rapid developments. Growth in size and the optimization of wind turbines has enabled wind energy to become increasingly competitive with conventional energy sources. As a result today's wind turbines participate actively in the power...... by any single modelling software program. In addition a huge range of in-house programs from different companies exist, the most widely known software for current research on the power grid are PSS/E, EMTDC/PSCAD and DigSilent. In general research and especially for control developments the software...... of the model. Investigations in optimisation of the implemented models are advised. Otherwise the presented models can be seen as basis for further modelling investigations. The developed models are open for further extension for different purpose, e.g. research of the harmonics. The introduced saturation...
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede
2018-01-01
strategies based on: 1) a power control method (P-CPG), 2) a current limit method (I-CPG) and 3) the Perturb and Observe algorithm (P&O-CPG). However, the operational mode changes (e.g., from the maximum power point tracking to a CPG operation) will affect the entire system performance. Thus, a benchmarking...... of the presented CPG strategies is also conducted on a 3-kW single-phase grid-connected PV system. Comparisons reveal that either the P-CPG or I-CPG strategies can achieve fast dynamics and satisfactory steady-state performance. In contrast, the P&O-CPG algorithm is the most suitable solution in terms of high...
Energy Technology Data Exchange (ETDEWEB)
Schnyder, G.; Mauchle, P.
2003-07-01
This is the third part of a ten-part final report for the Swiss Federal Office of Energy (SFOE) on a project that looked into potential problems relating to the Swiss electricity distribution grid with respect to the increasing number of distributed power generation facilities being put into service. The identification of special conditions for the grid's operation and future development that take increasing decentralised power production into account are discussed. The results of the project activities encompass the analysis and evaluation of various problem areas associated with planning and management of the grid during normal operation and periods of malfunction, as well as required modifications to safety systems and grid configurations. The first part of this second appendix to the main report examines the electrical conditions and requirements that have to be met by distributed production facilities. These include limits for voltage and frequency, synchronisation aspects, protection, reactive power questions and islanding. Also, recommendations are made on the assessment of grid reactions and on the avoidance of non-permissible effects on the grid's audio-frequency remote control apparatus. A second part examines the situation concerning the connection of distributed power units to the grid and grid topologies. The last chapter lists relevant standards and guidelines.
ANALYSIS AND VALIDATION OF GRID DEM GENERATION BASED ON GAUSSIAN MARKOV RANDOM FIELD
Directory of Open Access Journals (Sweden)
F. J. Aguilar
2016-06-01
Full Text Available Digital Elevation Models (DEMs are considered as one of the most relevant geospatial data to carry out land-cover and land-use classification. This work deals with the application of a mathematical framework based on a Gaussian Markov Random Field (GMRF to interpolate grid DEMs from scattered elevation data. The performance of the GMRF interpolation model was tested on a set of LiDAR data (0.87 points/m2 provided by the Spanish Government (PNOA Programme over a complex working area mainly covered by greenhouses in Almería, Spain. The original LiDAR data was decimated by randomly removing different fractions of the original points (from 10% to up to 99% of points removed. In every case, the remaining points (scattered observed points were used to obtain a 1 m grid spacing GMRF-interpolated Digital Surface Model (DSM whose accuracy was assessed by means of the set of previously extracted checkpoints. The GMRF accuracy results were compared with those provided by the widely known Triangulation with Linear Interpolation (TLI. Finally, the GMRF method was applied to a real-world case consisting of filling the LiDAR-derived DSM gaps after manually filtering out non-ground points to obtain a Digital Terrain Model (DTM. Regarding accuracy, both GMRF and TLI produced visually pleasing and similar results in terms of vertical accuracy. As an added bonus, the GMRF mathematical framework makes possible to both retrieve the estimated uncertainty for every interpolated elevation point (the DEM uncertainty and include break lines or terrain discontinuities between adjacent cells to produce higher quality DTMs.
Chan, William M.; Rogers, Stuart E.; Nash, Steven M.; Buning, Pieter G.; Meakin, Robert
2005-01-01
Chimera Grid Tools (CGT) is a software package for performing computational fluid dynamics (CFD) analysis utilizing the Chimera-overset-grid method. For modeling flows with viscosity about geometrically complex bodies in relative motion, the Chimera-overset-grid method is among the most computationally cost-effective methods for obtaining accurate aerodynamic results. CGT contains a large collection of tools for generating overset grids, preparing inputs for computer programs that solve equations of flow on the grids, and post-processing of flow-solution data. The tools in CGT include grid editing tools, surface-grid-generation tools, volume-grid-generation tools, utility scripts, configuration scripts, and tools for post-processing (including generation of animated images of flows and calculating forces and moments exerted on affected bodies). One of the tools, denoted OVERGRID, is a graphical user interface (GUI) that serves to visualize the grids and flow solutions and provides central access to many other tools. The GUI facilitates the generation of grids for a new flow-field configuration. Scripts that follow the grid generation process can then be constructed to mostly automate grid generation for similar configurations. CGT is designed for use in conjunction with a computer-aided-design program that provides the geometry description of the bodies, and a flow-solver program.
Directory of Open Access Journals (Sweden)
Lei Chen
2016-09-01
Full Text Available Concerning the development of a micro-grid integrated with multiple intermittent renewable energy resources, one of the main issues is related to the improvement of its robustness against short-circuit faults. In a sense, the superconducting fault current limiter (SFCL can be regarded as a feasible approach to enhance the transient performance of a micro-grid under fault conditions. In this paper, the fault transient analysis of a micro-grid, including distributed generation, energy storage and power loads, is conducted, and regarding the application of one or more flux-coupling-type SFCLs in the micro-grid, an integrated technical evaluation method considering current-limiting performance, bus voltage stability and device cost is proposed. In order to assess the performance of the SFCLs and verify the effectiveness of the evaluation method, different fault cases of a 10-kV micro-grid with photovoltaic (PV, wind generator and energy storage are simulated in the MATLAB software. The results show that, the efficient use of the SFCLs for the micro-grid can contribute to reducing the fault current, improving the voltage sags and suppressing the frequency fluctuations. Moreover, there will be a compromise design to fully take advantage of the SFCL parameters, and thus, the transient performance of the micro-grid can be guaranteed.
Incorporation of wind generation to the Mexican power grid: Steady state analysis
Energy Technology Data Exchange (ETDEWEB)
Tovar, J.H.; Guardado, J.L.; Cisneros, F. [Inst. Tecnologico de Morelia (Mexico); Cadenas, R.; Lopez, S. [Comision Federal de Electricidad, Morelia (Mexico)
1997-09-01
This paper describes a steady state analysis related with the incorporation of large amounts of eolic generation into the Mexican power system. An equivalent node is used to represent individual eolic generators in the wind farm. Possible overloads, losses, voltage and reactive profiles and estimated severe contingencies are analyzed. Finally, the conclusions of this study are presented.
International Nuclear Information System (INIS)
Boukettaya, Ghada; Krichen, Lotfi
2014-01-01
A global supervisory strategy for a micro-grid power generation system that comprises wind and photovoltaic generation subsystems, a flywheel storage system, and domestic loads connected both to the hybrid power generators and to the grid, is developed in this paper. The objectives of the supervisor control are, firstly, to satisfy in most cases the load power demand and, secondly, to check storage and grid constraints to prevent blackout, to reduce energy costs and greenhouse gas emissions, and to extend the life of the flywheel. For these purposes, the supervisor determines online the operation mode of the different generation subsystems, switching from maximum power conversion to power regulation. Decision criteria for the supervisor based on actual variables are presented. Finally, the performance of the supervisor is extensively assessed through computer simulation using a comprehensive nonlinear model of the studied system. - Highlights: • We supervise a micro-grid power generation system with an objective to produce clipping grid consumption. • The supervisor switch online from maximum power conversion to power regulation. • We provide services both for domestic users and for the distribution network manager. • The developed algorithm is tested and validated for different scenarios
The properties of radio ellipticals
International Nuclear Information System (INIS)
Sparks, W.B.; Disney, M.J.; Rodgers, A.W.
1984-01-01
Optical and additional radio data are presented for the bright galaxies of the Disney and Wall survey (1977 Mon. Not. R. Astron. Soc. 179, 235). These data form the basis of a statistical comparison of the properties of radio elliptical galaxies to radio-quiet ellipticals. The correlations may be explained by the depth of the gravitational potential well in which the galaxy resides governing the circumstances under which an elliptical galaxy rids itself of internally produced gas. (author)
Abdelli, Radia; Rekioua, Djamila; Rekioua, Toufik; Tounzi, Abdelmounaïm
2013-07-01
This paper presents a modulated hysteresis direct torque control (MHDTC) applied to an induction generator (IG) used in wind energy conversion systems (WECs) connected to the electrical grid through a back-to-back converter. The principle of this strategy consists in superposing to the torque reference a triangular signal, as in the PWM strategy, with the desired switching frequency. This new modulated reference is compared to the estimated torque by using a hysteresis controller as in the classical direct torque control (DTC). The aim of this new approach is to lead to a constant frequency and low THD in grid current with a unit power factor and a minimum voltage variation despite the wind variation. To highlight the effectiveness of the proposed method, a comparison was made with classical DTC and field oriented control method (FOC). The obtained simulation results, with a variable wind profile, show an adequate dynamic of the conversion system using the proposed method compared to the classical approaches. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.
An Efficient Mesh Generation Method for Fractured Network System Based on Dynamic Grid Deformation
Directory of Open Access Journals (Sweden)
Shuli Sun
2013-01-01
Full Text Available Meshing quality of the discrete model influences the accuracy, convergence, and efficiency of the solution for fractured network system in geological problem. However, modeling and meshing of such a fractured network system are usually tedious and difficult due to geometric complexity of the computational domain induced by existence and extension of fractures. The traditional meshing method to deal with fractures usually involves boundary recovery operation based on topological transformation, which relies on many complicated techniques and skills. This paper presents an alternative and efficient approach for meshing fractured network system. The method firstly presets points on fractures and then performs Delaunay triangulation to obtain preliminary mesh by point-by-point centroid insertion algorithm. Then the fractures are exactly recovered by local correction with revised dynamic grid deformation approach. Smoothing algorithm is finally applied to improve the quality of mesh. The proposed approach is efficient, easy to implement, and applicable to the cases of initial existing fractures and extension of fractures. The method is successfully applied to modeling of two- and three-dimensional discrete fractured network (DFN system in geological problems to demonstrate its effectiveness and high efficiency.
Column generation algorithms for virtual network embedding in flexi-grid optical networks.
Lin, Rongping; Luo, Shan; Zhou, Jingwei; Wang, Sheng; Chen, Bin; Zhang, Xiaoning; Cai, Anliang; Zhong, Wen-De; Zukerman, Moshe
2018-04-16
Network virtualization provides means for efficient management of network resources by embedding multiple virtual networks (VNs) to share efficiently the same substrate network. Such virtual network embedding (VNE) gives rise to a challenging problem of how to optimize resource allocation to VNs and to guarantee their performance requirements. In this paper, we provide VNE algorithms for efficient management of flexi-grid optical networks. We provide an exact algorithm aiming to minimize the total embedding cost in terms of spectrum cost and computation cost for a single VN request. Then, to achieve scalability, we also develop a heuristic algorithm for the same problem. We apply these two algorithms for a dynamic traffic scenario where many VN requests arrive one-by-one. We first demonstrate by simulations for the case of a six-node network that the heuristic algorithm obtains very close blocking probabilities to exact algorithm (about 0.2% higher). Then, for a network of realistic size (namely, USnet) we demonstrate that the blocking probability of our new heuristic algorithm is about one magnitude lower than a simpler heuristic algorithm, which was a component of an earlier published algorithm.
Control strategy of grid-connected photovoltaic generation system based on GMPPT method
Wang, Zhongfeng; Zhang, Xuyang; Hu, Bo; Liu, Jun; Li, Ligang; Gu, Yongqiang; Zhou, Bowen
2018-02-01
There are multiple local maximum power points when photovoltaic (PV) array runs under partial shading condition (PSC).However, the traditional maximum power point tracking (MPPT) algorithm might be easily trapped in local maximum power points (MPPs) and cannot find the global maximum power point (GMPP). To solve such problem, a global maximum power point tracking method (GMPPT) is improved, combined with traditional MPPT method and particle swarm optimization (PSO) algorithm. Under different operating conditions of PV cells, different tracking algorithms are used. When the environment changes, the improved PSO algorithm is adopted to realize the global optimal search, and the variable step incremental conductance (INC) method is adopted to achieve MPPT in optimal local location. Based on the simulation model of the PV grid system built in Matlab/Simulink, comparative analysis of the tracking effect of MPPT by the proposed control algorithm and the traditional MPPT method under the uniform solar condition and PSC, validate the correctness, feasibility and effectiveness of the proposed control strategy.
Energy Technology Data Exchange (ETDEWEB)
Makarov, Yuri V.; Huang, Zhenyu; Etingov, Pavel V.; Ma, Jian; Guttromson, Ross T.; Subbarao, Krishnappa; Chakrabarti, Bhujanga B.
2010-01-01
unique features make this work a significant step forward toward the objective of incorporating of wind, solar, load, and other uncertainties into power system operations. Currently, uncertainties associated with wind and load forecasts, as well as uncertainties associated with random generator outages and unexpected disconnection of supply lines, are not taken into account in power grid operation. Thus, operators have little means to weigh the likelihood and magnitude of upcoming events of power imbalance. In this project, funded by the U.S. Department of Energy (DOE), a framework has been developed for incorporating uncertainties associated with wind and load forecast errors, unpredicted ramps, and forced generation disconnections into the energy management system (EMS) as well as generation dispatch and commitment applications. A new approach to evaluate the uncertainty ranges for the required generation performance envelope including balancing capacity, ramping capability, and ramp duration has been proposed. The approach includes three stages: forecast and actual data acquisition, statistical analysis of retrospective information, and prediction of future grid balancing requirements for specified time horizons and confidence levels. Assessment of the capacity and ramping requirements is performed using a specially developed probabilistic algorithm based on a histogram analysis, incorporating all sources of uncertainties of both continuous (wind and load forecast errors) and discrete (forced generator outages and start-up failures) nature. A new method called the “flying brick” technique has been developed to evaluate the look-ahead required generation performance envelope for the worst case scenario within a user-specified confidence level. A self-validation algorithm has been developed to validate the accuracy of the confidence intervals.
Grid-connected in-stream hydroelectric generation based on the doubly fed induction machine
Lenberg, Timothy J.
Within the United States, there is a growing demand for new environmentally friendly power generation. This has led to a surge in wind turbine development. Unfortunately, wind is not a stable prime mover, but water is. Why not apply the advances made for wind to in-stream hydroelectric generation? One important advancement is the creation of the Doubly Fed Induction Machine (DFIM). This thesis covers the application of a gearless DFIM topology for hydrokinetic generation. After providing background, this thesis presents many of the options available for the mechanical portion of the design. A mechanical turbine is then specified. Next, a method is presented for designing a DFIM including the actual design for this application. In Chapter 4, a simulation model of the system is presented, complete with a control system that maximizes power generation based on water speed. This section then goes on to present simulation results demonstrating proper operation.
DEFF Research Database (Denmark)
Yang, Yongheng; Enjeti, Prasad; Blaabjerg, Frede
2013-01-01
Current grid standards seem to largely require low power (e.g. several kilowatts) single-phase photovoltaic (PV) systems to operate at unity power factor with maximum power point tracking, and disconnect from the grid under grid faults. However, in case of a wide-scale penetration of single......-phase PV systems in the distributed grid, the disconnection under grid faults can contribute to: a) voltage flickers, b) power outages, and c) system instability. In this paper, grid code modifications are explored for wide-scale adoption of PV systems in the distribution grid. More recently, Italy...... and Japan, have undertaken a major review of standards for PV power conversion systems connected to low voltage networks. In view of this, the importance of low voltage ride-through for single-phase PV power systems under grid faults along with reactive power injection is studied in this paper. Three...
Uniformization of elliptic curves
Ülkem, Özge; Ulkem, Ozge
2015-01-01
Every elliptic curve E defined over C is analytically isomorphic to C*=qZ for some q ∊ C*. Similarly, Tate has shown that if E is defined over a p-adic field K, then E is analytically isomorphic to K*=qZ for some q ∊ K . Further the isomorphism E(K) ≅ K*/qZ respects the action of the Galois group GK/K, where K is the algebraic closure of K. I will explain the construction of this isomorphism.
Elliptic partial differential equations
Han, Qing
2011-01-01
Elliptic Partial Differential Equations by Qing Han and FangHua Lin is one of the best textbooks I know. It is the perfect introduction to PDE. In 150 pages or so it covers an amazing amount of wonderful and extraordinary useful material. I have used it as a textbook at both graduate and undergraduate levels which is possible since it only requires very little background material yet it covers an enormous amount of material. In my opinion it is a must read for all interested in analysis and geometry, and for all of my own PhD students it is indeed just that. I cannot say enough good things abo
Parallelization of elliptic solver for solving 1D Boussinesq model
Tarwidi, D.; Adytia, D.
2018-03-01
In this paper, a parallel implementation of an elliptic solver in solving 1D Boussinesq model is presented. Numerical solution of Boussinesq model is obtained by implementing a staggered grid scheme to continuity, momentum, and elliptic equation of Boussinesq model. Tridiagonal system emerging from numerical scheme of elliptic equation is solved by cyclic reduction algorithm. The parallel implementation of cyclic reduction is executed on multicore processors with shared memory architectures using OpenMP. To measure the performance of parallel program, large number of grids is varied from 28 to 214. Two test cases of numerical experiment, i.e. propagation of solitary and standing wave, are proposed to evaluate the parallel program. The numerical results are verified with analytical solution of solitary and standing wave. The best speedup of solitary and standing wave test cases is about 2.07 with 214 of grids and 1.86 with 213 of grids, respectively, which are executed by using 8 threads. Moreover, the best efficiency of parallel program is 76.2% and 73.5% for solitary and standing wave test cases, respectively.
Dusty Feedback from Massive Black Holes in Two Elliptical Galaxies
Temi, P.; Brighenti, F.; Mathews, W. G.; Amblard, A.; Riguccini, L.
2013-01-01
Far-infrared dust emission from elliptical galaxies informs us about galaxy mergers, feedback energy outbursts from supermassive black holes and the age of galactic stars. We report on the role of AGN feedback observationally by looking for its signatures in elliptical galaxies at recent epochs in the nearby universe. We present Herschel observations of two elliptical galaxies with strong and spatially extended FIR emission from colder grains 5-10 kpc distant from the galaxy cores. Extended excess cold dust emission is interpreted as evidence of recent feedback-generated AGN energy outbursts in these galaxies, visible only in the FIR, from buoyant gaseous outflows from the galaxy cores.
Energy Technology Data Exchange (ETDEWEB)
Ouhrouche, Mohand [Department of Applied Sciences, University of Quebec at Chicoutimi, Quebec, G7H2B1 (Canada)
2009-03-15
Due to its simple construction, ruggedness and low cost, the induction generator driven by a wind turbine and feeding power to the grid appears to be an attractive solution to the problem of growing energy demand in the context of environmental issues. This paper investigates the integration of such a system into the main utility using RT-Lab trademark (Trademark of Opal-RT Technologies) software package running on a simple off-the-shelf PC. This real-time simulation platform is now adopted by many high-tech industries as a real-time laboratory package for rapid control prototyping and for Hardware-in-the-Loop applications. Real-time digital simulation results obtained during contingencies, such as islanding and unbalanced faults are presented and analysed. (author)
DEFF Research Database (Denmark)
Cha, Seung-Tae; Zhao, Haoran; Wu, Qiuwei
2012-01-01
into the islanding operation mode, while the centralized joint load frequency control (CJLFC) utilizing DGs handles the secondary frequency regulation. The BESS with the associated controllers has been modelled in Real-time digital simulator (RTDS) in order to identify the improvement of the frequency and voltage......This paper describes a coordinated control scheme of battery energy storage system (BESS) and distributed generations (DGs) for electric distribution grid operation. The BESS is designed to stabilize frequency and voltages as a primary control after the electric distribution system enters...... response. The modified IEEE 9-bus system, which is comprised of several DG units, wind power plant and the BESS, has been employed to illustrate the performance of the proposed coordinated flexible control scheme using RTDS in order to verify its practical efficacy....
Directory of Open Access Journals (Sweden)
Zetty Adibah Kamaruzzaman
2016-06-01
Full Text Available This paper presents the impact of grid-connected photovoltaic (PV generator on dynamic voltage stability of a power distribution system by considering solar intermittency, PV penetration level, and contingencies such as line outage and load increase. The IEEE 13 node test feeder is used as a test system, and a solar PV of 0.48 kV/0.5 MVA is integrated into the test system. Test results show that system voltage is stable at high PV penetration levels. Increase in load causes voltage instability, in which voltage drops below its allowable operating limit. Thus, increase in PV penetration level does not improve system voltage stability because the system experiences voltage collapse during line outage.
DEFF Research Database (Denmark)
Zhou, Dao; Blaabjerg, Frede; Lau, Mogens
2016-01-01
As wind farms are normally located in remote areas, many grid codes have been issued especially related to the reactive power support. Although the Doubly-Fed Induction Generator (DFIG) based power converter is able to control the active power and reactive power independently, the effects...... of providing reactive power on the lifetime of the power converter and the cost-of-energy of the whole system are seldom evaluated, even though it is an important topic. In this paper, the loss models of the DFIG system are established at various conditions of the reactive power injection. If the mission...... profile is taken into account, the lifespan of the power semiconductors as well as the cost of the reactive power can be calculated. It is concluded that an over-excited reactive power injection significantly reduces the power converter lifetime, only 1/4 of the case that there is no reactive power...
DEFF Research Database (Denmark)
Hernández, Adriana Carolina Luna; Aldana, Nelson Leonardo Diaz; Savaghebi, Mehdi
2017-01-01
Microgrids rely on energy management levels to optimally schedule their components. Conventionally, the research in this field has been focused on the optimal formulation of the generation or the demand side management separately without considering real case scenarios and validated only...... by simulation. This paper presents the power scheduling of a real site microgrid under a price-based demand response program defined in Shanghai, China managing generation and demand simultaneously. The proposed optimization problem aims to minimize operating cost by managing renewable energy sources as well...
Fast computation of complete elliptic integrals and Jacobian elliptic functions
Fukushima, Toshio
2009-12-01
As a preparation step to compute Jacobian elliptic functions efficiently, we created a fast method to calculate the complete elliptic integral of the first and second kinds, K( m) and E( m), for the standard domain of the elliptic parameter, 0 procedure to compute simultaneously three Jacobian elliptic functions, sn( u| m), cn( u| m), and dn( u| m), by repeated usage of the double argument formulae starting from the Maclaurin series expansions with respect to the elliptic argument, u, after its domain is reduced to the standard range, 0 ≤ u procedure is 25-70% faster than the methods based on the Gauss transformation such as Bulirsch’s algorithm, sncndn, quoted in the Numerical Recipes even if the acceleration of computation of K( m) is not taken into account.
Energy Technology Data Exchange (ETDEWEB)
Gottsponer, O.; Mauchle, P.
2003-07-01
This is the tenth and last part of a final report for the Swiss Federal Office of Energy (SFOE) on a project that looked into potential problems relating to the Swiss electricity distribution grid with respect to the increasing number of distributed power generation facilities being put into service. The identification of special conditions for the grid's operation and future development that take increasing decentralised power production into account are discussed. The results of the project activities encompass the analysis and evaluation of various problem areas associated with planning and management of the grid during normal operation and periods of malfunction, as well as required modifications to safety systems and grid configurations. This ninth appendix to the main report presents an overview and details of the literature and internet sources used in the project. Also, similar projects that discuss the problem area dealt with are briefly described. These include the Dispower, EDIson, DEMS, AMOEVES and ELSAD projects.
DEFF Research Database (Denmark)
Chittur Ramaswamy, Parvathy; Deconinck, Geert; Pillai, Jayakrishnan Radhakrishna
2013-01-01
This paper considers hourly reconfiguration of a low voltage distribution network with the objectives of minimizing power loss and voltage deviation. The uncertainty in photovoltaic (PV) generation which in turn will affect the optimum configuration is tackled with the help of scenario analysis. ......-dominated solutions, demonstrating their trade-offs. Finally, the best compromise solution can be selected depending on the decision maker's requirement....
Rotor Voltage Dynamics in the Doubly Fed Induction Generator During Grid Faults
DEFF Research Database (Denmark)
Lima, Francisco K. A.; Luna, Alvaro; Rodriguez, Pedro
2010-01-01
This paper presents a new control strategy for the rotor-side converter (RSC) of wind turbines (WTs) based on doubly fed induction generators (DFIG) that intends to improve its low-voltage ride through capability. The main objective of this work is to design an algorithm that would enable the sys...
DEFF Research Database (Denmark)
Luna, A.; Rocabert, J.; Candela, I.
2012-01-01
The Transmission System Operators are specially concerned about the Low Voltage Ride Through requirements of distributed generation power plants. Solutions based on the installation of STATCOMs and DVRs, as well as on advanced control functionalities for the existing power converters have contrib...
Constant Power Generation of Photovoltaic Systems Considering the Distributed Grid Capacity
DEFF Research Database (Denmark)
Yang, Yongheng; Blaabjerg, Frede; Wang, Huai
2014-01-01
With an imperative demand of clean and reliable electricity generation in some countries, the increasing adoption of new photovoltaic (PV) systems pushes the Distribution System Operators (DSOs) to expand the transmission/distributed lines. However, the potential cost brought by such extensions...
Cluster versus grid for operational generation of ATCOR's MODTRAN-based look up tables
Brazile, J.; Richter, R.; Schlapfer, D.; Schaepman, M.E.; Itten, K.I.
2008-01-01
A critical step in the product generation of satellite or airborne earth observation data is the correction of atmospheric features. Due to the complexity of the underlying physical model and the amount of coordinated effort required to provide, verify and maintain baseline atmospheric observations,
Directory of Open Access Journals (Sweden)
Farizal Farizal
2016-08-01
Full Text Available This research considers the problem of reducing CO2 emissions from the Java-Bali power grid system that consists of a variety of power-generating plants: coal-fired, natural gas, oil, and renewable energy (PV, geothermal, hydroelectric, wind, and landfill gas. The problem is formulated as linear programming and solved using LINGO 10. The model was developed for a nation to meet a specified CO2 emission target. Two carbon dioxide mitigation options are considered in this study, i.e. fuel balancing and fuel switching. In order to reduce the CO2 emissions by 26% in 2021, State Electric Supply Company (PLN has to generate up to 30% of electricity from renewable energy (RE, and the cost of electricity (COE is expected to increase to 617.77 IDR per kWh for a fuel balancing option, while for fuel switching option, PLN has to generate 29% of electricity from RE, and the COE is expected to increase to 535.85 IDR per kWh.
International Nuclear Information System (INIS)
Jansweijer, P.P.M.; Es, J.T. van.
1990-01-01
This report describes a fast pulse generator. This generator delivers a high-voltage pulse of at most 6000 V with a rise time being smaller than 50 nS. this results in a slew rate of more than 120.000 volts per μS. The pulse generator is used to control the grid of the injector of the electron accelerator MEA. The capacity of this grid is about 60 pF. In order to charge this capacity up to 6000 volts in 50 nS a current of 8 ampere is needed. The maximal pulse length is 50 μS with a repeat frequency of 500 Hz. During this 50 μS the stability of the pulse amplitude is better than 0.1%. (author). 20 figs
Elliptic curves for applications (Tutorial)
Lange, T.; Bernstein, D.J.; Chatterjee, S.
2011-01-01
More than 25 years ago, elliptic curves over finite fields were suggested as a group in which the Discrete Logarithm Problem (DLP) can be hard. Since then many researchers have scrutinized the security of the DLP on elliptic curves with the result that for suitably chosen curves only exponential
CSIR Research Space (South Africa)
Szewczuk, S
2009-06-01
Full Text Available agricultural products as the basis for new economic activities for the communities adjacent to the Hluleka Nature Reserve and Lucingweni village. To increase the demand for energy and electricity, from not only the domestic sector from the various villages... and clean forms of energy to enable productive economic activities to generate much needed income. However, the provision of energy must be cognisant of Africa's primary needs of also delivering potable drinking water and sanitation. Hence...
International Nuclear Information System (INIS)
Azoumah, Y; Yamegueu, D; Py, X
2012-01-01
Access to energy is known as a key issue for poverty reduction. The electrification rate of sub Saharan countries is one of the lowest among the developing countries. However this part of the world has natural energy resources that could help raising its access to energy, then its economic development. An original 'flexy energy' concept of hybrid solar pv/diesel/biofuel power plant, without battery storage, is developed in order to not only make access to energy possible for rural and peri-urban populations in Africa (by reducing the electricity generation cost) but also to make the electricity production sustainable in these areas. Some experimental results conducted on this concept prototype show that the sizing of a pv/diesel hybrid system by taking into account the solar radiation and the load/demand profile of a typical area may lead the diesel generator to operate near its optimal point (70-90 % of its nominal power). Results also show that for a reliability of a PV/diesel hybrid system, the rated power of the diesel generator should be equal to the peak load. By the way, it has been verified through this study that the functioning of a pv/Diesel hybrid system is efficient for higher load and higher solar radiation.
Azoumah, Y.; Yamegueu, D.; Py, X.
2012-02-01
Access to energy is known as a key issue for poverty reduction. The electrification rate of sub Saharan countries is one of the lowest among the developing countries. However this part of the world has natural energy resources that could help raising its access to energy, then its economic development. An original "flexy energy" concept of hybrid solar pv/diesel/biofuel power plant, without battery storage, is developed in order to not only make access to energy possible for rural and peri-urban populations in Africa (by reducing the electricity generation cost) but also to make the electricity production sustainable in these areas. Some experimental results conducted on this concept prototype show that the sizing of a pv/diesel hybrid system by taking into account the solar radiation and the load/demand profile of a typical area may lead the diesel generator to operate near its optimal point (70-90 % of its nominal power). Results also show that for a reliability of a PV/diesel hybrid system, the rated power of the diesel generator should be equal to the peak load. By the way, it has been verified through this study that the functioning of a pv/Diesel hybrid system is efficient for higher load and higher solar radiation.
Finley, Christopher
Power generation using wind turbines increases the electrical system balancing, regulation and ramp rate requirements due to the minute to minute variability in wind speed and the difficulty in accurately forecasting wind speeds. The addition of thermal energy storage, such as ice storage, to a building's space cooling equipment increases the operational flexibility of the equipment by allowing the owner to choose when the chiller is run. The ability of the building owner to increase the power demand from the chiller (e.g. make ice) or to decrease the power demand (e.g. melt ice) to provide electrical system ancillary services was evaluated.
High-Performance Constant Power Generation in Grid-Connected PV Systems
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede
2016-01-01
An advanced power control strategy by limiting the maximum feed-in power of PV systems has been proposed, which can ensure a fast and smooth transition between maximum power point tracking and Constant Power Generation (CPG). Regardless of the solar irradiance levels, high-performance and stable...... operation are always achieved by the proposed control strategy. It can regulate the PV output power according to any set-point, and force the PV systems to operate at the left side of the maximum power point without stability problems. Experimental results have verified the effectiveness of the proposed CPG...
Institute of Scientific and Technical Information of China (English)
许贤泽
2000-01-01
The finite element analysis is applied to structure and freedom-system analysis. Its grid generating method is important to the finite element modeling,which generates the grid automatically by the sectional division method and gets the finite element grid model, thus accomplishing the pre-work of the finite element analysis.%用有限元法对进行结构和自由度体系进行分析，其网格的生成是建立有限元模型的重要技术，利用分块分割法对网格自动划分，从而形成有限元网格模型，完成有限元分析的前处理。
Directory of Open Access Journals (Sweden)
Adebanji B.
2017-08-01
Full Text Available This paper presented an optimal sizing technique for an off-grid hybrid system consisting of Small Hydro SHP system Photovoltaic PV modules Battery BATT banks and Diesel Generator DG. The objective cost function Annualized Cost System and the Loss of Power Supply Probability LPSP were minimized with application of Genetic Algorithm GA in order to reduce the Cost of Energy COE generation. GA compared to other convectional optimization methods has the ability to attain global optimum easily. The decision variables are the number of small hydro turbines NSHP number of solar panels NPV number of battery banks NBATT and the capacity of DG PDG. The proposed method was applied to a typical rural village Itapaji-Ekiti in Nigeria. The monthly average solar irradiance data were converted into hourly solar irradiance data for uniformity. Sensitivity analysis was also performed to identify the most important parameter influencing the optimized hybrid system. The optimal sizing result of the HPS is 954 kW of SHP 290 kW of PV panels 9500 sets of 600Ah battery strings and 350 kW of DG. The optimal Loss of Power Supply Probability LPSP is 0.0054 and the Renewable Fraction RF is 0.62 which is indeed a significant improvement on the environment and comparatively better than any other combinations in the system.
Energy Technology Data Exchange (ETDEWEB)
Albuquerque, F.L.; Moraes, A.J.; Guimaraes, G.C.; Sanhueza, S.M.R.; Vaz, A.R. [Federal University of Uberlandia (UFU), MG (Brazil)
2009-07-01
In the case of photovoltaic solar systems (PV) acting as a distributed generation (DG), the DC energy obtained is fed through the power-conditioning unit (inverter) to the grid. The majority of contemporary inverters used in DG systems are current source inverters (CSI) operating at unity power factor. If, however, we assume that voltage source inverters (VSI) can be utilized instead of CSI, we can generate reactive power commensurate with the remaining unused capacity at any given point in time. According to the theory of instantaneous power, the reactive and active power of inverter can be regulated by changing the amplitude and the phase of the output voltage of the inverter. Based on this theory, the active power output and the reactive power compensation (RPC) of the system are realized simultaneously. When the insolation is weak or the PV modules are inoperative at night, the RPC feature of PV system can still be used to improve the utilization factor of the inverter. The MATLAB simulation results validate the feasibility of the method. (author)
The PWM strategies of grid-connected distributed generation active NPC inverters
DEFF Research Database (Denmark)
Ma, Lin; Xinmin, Jin; Kerekes, Tamas
2009-01-01
The Neutral Point Clamped topology due to high efficiency, low leakage current and EMI, its integration is widely used in the distributed generation (DG) systems. However the main disadvantage of the NPC inverter is given by an unequal distribution of the losses in the semiconductor devices, which...... leads to an unequal distribution of temperature. By using the Active NPC topology, the power losses distribution problem is alleviated. The modulation strategy is a key issue for losses distribution in this topology. In this paper two known strategies are discussed and a new proposed PWM strategy......, namely the Adjustable Losses Distribution (ALD) PWM strategy is proposed for better losses distribution in the Active NPC (ANPC) topology. Simulations using Simulink and the PLECS toolbox have been done for evaluating efficiency of different NPC topologies and some experimental results are presented...
Super short term forecasting of photovoltaic power generation output in micro grid
Gong, Cheng; Ma, Longfei; Chi, Zhongjun; Zhang, Baoqun; Jiao, Ran; Yang, Bing; Chen, Jianshu; Zeng, Shuang
2017-01-01
The prediction model combining data mining and support vector machine (SVM) was built. Which provide information of photovoltaic (PV) power generation output for economic operation and optimal control of micro gird, and which reduce influence of power system from PV fluctuation. Because of the characteristic which output of PV rely on radiation intensity, ambient temperature, cloudiness, etc., so data mining was brought in. This technology can deal with large amounts of historical data and eliminate superfluous data, by using fuzzy classifier of daily type and grey related degree. The model of SVM was built, which can dock with information from data mining. Based on measured data from a small PV station, the prediction model was tested. The numerical example shows that the prediction model is fast and accurate.
Control and Protection in Low Voltage Grid with Large Scale Renewable Electricity Generation
DEFF Research Database (Denmark)
Mustafa, Ghullam
of the inverter controllers must be developed to Voltage-Frequency (VF) mode; and the others in either PV or PQ modes. The operation of the MG with several PV inverters and single VF inverter is similar to the operation of MG with a synchronous machine as slack bus. The VF inverter establishes the voltage...... of renewable energy based DGs are reduced CO2 emission, reduced operational cost as almost no fuel is used for their operation and less transmission and distribution losses as these units are normally built near to the load centers. This has also resulted in some operational challenges due to the unpredictable...... nature of such power generation sources. Some of the operational challenges include voltage variations due to power fluctuations coming from the DG units. On the other hand, it has also opened up some opportunities. One of the opportunities is islanding operation of the distribution system with DG unit...
Directory of Open Access Journals (Sweden)
S V S Phani Kumar.Ch
2016-06-01
Full Text Available In recent years with the excessive consumption of electrical energy, the incongruity between generation and demand, the irrational structure of World’s energy as well as the environmental pollution have become progressively more evident. It has become crucial for ecological development to reduce the consumption of conventional energy and to enhance the development and utilization of renewable energy. Wind energy and Solar are unlimited supply of renewable energy and it has no pollution. But this concept suffer from the power quality issues from grid and generator side, this paper presents a control strategy for achieving maximum benefits from these grid-interfacing inverter when installed in 3-phase 4-wire distribution systems. The inverter can be controlled to perform as a multi-function device by incorporating active power filter functionality. The inverter can thus be utilized as: 1 power converter to inject power generated from RES to the grid and 2 shunt APF (Active Power Filter to compensate current unbalance, load current harmonics, load reactive power demand and load neutral current. All of these functions may be accomplished either individually or simultaneously. With such a control, the combination of grid-interfacing inverter and the 3-phase 4-wire linear/non-linear unbalanced load at point of common coupling appears as balanced linear load to the grid. The Paper propose design of 500kW Type I Wind Generation System 250kW each with Four Leg Inverter Controlled by d-q technique operated as DSTATCOM connected to 415V 4 wire Grid and also the results are compared with conventional Unit Vector Control. The proposed d-q method reduces the %THD of system to 1.97% from 24.12% where Unit Vector Control is of 3.94% which was on higher side , this is simulated in MATLAB/SIMULINK.
Energy Technology Data Exchange (ETDEWEB)
Makarov, Yuri V.; Huang, Zhenyu; Etingov, Pavel V.; Ma, Jian; Guttromson, Ross T.; Subbarao, Krishnappa; Chakrabarti, Bhujanga B.
2010-09-01
features make this work a significant step forward toward the objective of incorporating of wind, solar, load, and other uncertainties into power system operations. In this report, a new methodology to predict the uncertainty ranges for the required balancing capacity, ramping capability and ramp duration is presented. Uncertainties created by system load forecast errors, wind and solar forecast errors, generation forced outages are taken into account. The uncertainty ranges are evaluated for different confidence levels of having the actual generation requirements within the corresponding limits. The methodology helps to identify system balancing reserve requirement based on a desired system performance levels, identify system “breaking points”, where the generation system becomes unable to follow the generation requirement curve with the user-specified probability level, and determine the time remaining to these potential events. The approach includes three stages: statistical and actual data acquisition, statistical analysis of retrospective information, and prediction of future grid balancing requirements for specified time horizons and confidence intervals. Assessment of the capacity and ramping requirements is performed using a specially developed probabilistic algorithm based on a histogram analysis incorporating all sources of uncertainty and parameters of a continuous (wind forecast and load forecast errors) and discrete (forced generator outages and failures to start up) nature. Preliminary simulations using California Independent System Operator (California ISO) real life data have shown the effectiveness of the proposed approach. A tool developed based on the new methodology described in this report will be integrated with the California ISO systems. Contractual work is currently in place to integrate the tool with the AREVA EMS system.
International Nuclear Information System (INIS)
Yu Dayang; Zhang Bo; Liang Jun; Han Xueshan
2011-01-01
The large-scale wind power development in China has reached a bottleneck of grid integrating capability. As a result, excess wind electricity has to be rejected in the nighttime low demand hours, when the wind power is ramping up. To compensate for the fluctuation of wind power, new coal-fired power plants are being constructed along with the big wind projects in the North China grids. This study analyzed why adding coal-fired generation cannot remove the bottleneck of wind integration by modeling the operating problem of the wind integration. The peak-load adjusting factor of the regional grid is defined. Building more coal-fired power plants will not increase the adjusting factor of the current grid. Although it does help to increase the total integrated wind power in the short term, it will add difficulties to the long-term wind integration. Alternatively, the coordinated resource utilization is then suggested with the discussion of both the effective pumped hydro storage and the potential electric vehicle storage. - Highlights: → Adjusting factors indicate the grid wind integrating capability. → Building coal-fired generation restrains long-term wind integration. → HVDC and nuclear projects should be planned integrated with the wind. → Pumped storage and electric vehicles provide potential solutions.
C1,1 regularity for degenerate elliptic obstacle problems
Daskalopoulos, Panagiota; Feehan, Paul M. N.
2016-03-01
The Heston stochastic volatility process is a degenerate diffusion process where the degeneracy in the diffusion coefficient is proportional to the square root of the distance to the boundary of the half-plane. The generator of this process with killing, called the elliptic Heston operator, is a second-order, degenerate-elliptic partial differential operator, where the degeneracy in the operator symbol is proportional to the distance to the boundary of the half-plane. In mathematical finance, solutions to the obstacle problem for the elliptic Heston operator correspond to value functions for perpetual American-style options on the underlying asset. With the aid of weighted Sobolev spaces and weighted Hölder spaces, we establish the optimal C 1 , 1 regularity (up to the boundary of the half-plane) for solutions to obstacle problems for the elliptic Heston operator when the obstacle functions are sufficiently smooth.
Electromagnetic fields and Green functions in elliptical vacuum chambers
AUTHOR|(CDS)2084216; Biancacci, Nicolo; Migliorati, Mauro; Palumbo, Luigi; Vaccaro, Vittorio; CERN. Geneva. ATS Department
2017-01-01
In this paper, we discuss the electromagnetic interaction between a point charge travelling inside a waveguide of elliptical cross section, and the waveguide itself. By using a convenient expansion of the Mathieu functions, useful in particular for treating a variety of problems in applied mathematics and physics with elliptic geometry, we first obtain the longitudinal electromagnetic field of a point charge (Green function) in free space in terms of elliptical coordinates. This expression allows, then, to calculate the scattered field due to the boundary conditions in our geometry. By summing the contribution of the direct or primary field and the indirect field scattered by the boundary, after a careful choice of some expansion expressions, we derive a novel formula of the longitudinal electric field, in any transverse position of the elliptical cross section, generated by the charge moving along the longitudinal axis of the waveguide. The obtained expression is represented in a closed form, it can be diffe...
Wolsink, M.
2012-01-01
The rapid developing literature on ‘smart grids’ suggests that these will facilitate ‘distributed generation’ (DG) preferably from renewable sources. However, the current development of smart (micro)grids with substantial amount of DG ("DisGenMiGrids") suffers from a focus on mere ‘technology’.
Directory of Open Access Journals (Sweden)
David Caballero
2016-12-01
Full Text Available This paper proposes an active and reactive power control strategy based on predictive control approaches applied to gridconnected renewable energy systems. To accomplish this a multi-modular matrix converter topologies are used in combination with a simple but efficient grid synchronization strategy. The theoretical performance analysis is performed considering a six-phase wind energy generator system interconnected with the grid. Results based on a MATLAB/Simulink simulation environment are discussed and the most relevant characteristics of the proposed control technique are highlighted considering the total harmonic distortion and the mean squared error as a parameters of performance.
Directory of Open Access Journals (Sweden)
Senad Apelfröjd
2014-01-01
Full Text Available Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.
Apelfröjd, Senad; Eriksson, Sandra
2014-01-01
Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed.
2014-01-01
Results from experiments on a tap transformer based grid connection system for a variable speed vertical axis wind turbine are presented. The tap transformer based system topology consists of a passive diode rectifier, DC-link, IGBT inverter, LCL-filter, and tap transformer. Full range variable speed operation is enabled by using the different step-up ratios of a tap transformer. Simulations using MATLAB/Simulink have been performed in order to study the behavior of the system. A full experimental set up of the system has been used in the laboratory study, where a clone of the on-site generator was driven by an induction motor and the system was connected to a resistive load to better evaluate the performance. Furthermore, the system is run and evaluated for realistic wind speeds and variable speed operation. For a more complete picture of the system performance, a case study using real site Weibull parameters is done, comparing different tap selection options. The results show high system efficiency at nominal power and an increase in overall power output for full tap operation in comparison with the base case, a standard transformer. In addition, the loss distribution at different wind speeds is shown, which highlights the dominant losses at low and high wind speeds. Finally, means for further increasing the overall system efficiency are proposed. PMID:25258733
Directory of Open Access Journals (Sweden)
Daniel Ludois
2010-06-01
Full Text Available The application of high voltage dc (HVDC transmission for integrating large scale and/or off-shore wind generation systems with the electric grid is attractive in comparison to extra high voltage (EHV ac transmission due to a variety of reasons. While the technology of classical current sourced converters (CSC using thyristors is well established for realization of large HVDC systems, the technology of voltage sourced converters (VSC is emerging to be an alternative approach, particularly suitable for multi-terminal interconnections. More recently, a more modular scheme that may be termed ‘bridge of bridge’ converters (BoBC has been introduced to realize HVDC systems. While all these three approaches are functionally capable of realizing HVDC systems, the converter power circuit design trade-offs between these alternatives are not readily apparent. This paper presents an examination of these topologies from the point of view of power semiconductor requirements, reactive component requirements, operating losses, fault tolerance, multi-terminal operation, modularity, complexity, etc. Detailed analytical models will be used along with a benchmark application to develop a comparative evaluation of the alternatives that maybe used by wind energy/bulk transmission developers for performing engineering trade-off studies.
Energy Technology Data Exchange (ETDEWEB)
Mehrotra, Sanjay [Northwestern Univ., Evanston, IL (United States)
2016-09-07
The support from this grant resulted in seven published papers and a technical report. Two papers are published in SIAM J. on Optimization [87, 88]; two papers are published in IEEE Transactions on Power Systems [77, 78]; one paper is published in Smart Grid [79]; one paper is published in Computational Optimization and Applications [44] and one in INFORMS J. on Computing [67]). The works in [44, 67, 87, 88] were funded primarily by this DOE grant. The applied papers in [77, 78, 79] were also supported through a subcontract from the Argonne National Lab. We start by presenting our main research results on the scenario generation problem in Sections 1–2. We present our algorithmic results on interior point methods for convex optimization problems in Section 3. We describe a new ‘central’ cutting surface algorithm developed for solving large scale convex programming problems (as is the case with our proposed research) with semi-infinite number of constraints in Section 4. In Sections 5–6 we present our work on two application problems of interest to DOE.
On-design solutions of hypersonic flows past elliptic-cone derived waveriders
International Nuclear Information System (INIS)
Yoon, Bok Hyun
1992-01-01
The hypersonic flows past a class of elliptic-conederived waverider at the on-design condition are analyzed. A CFD(Computational Fluid Dynamics) algorithm due to Lawrence is utilized to numerically integrate the steady Euler equations. The singular behavior at the sharp leading-edge of a waverider where a bow shock is to be attached for the ideal situation makes the computation extremely difficult for convergence of numerical solution. Various types of grids are generated and tested for converged solutions. A new formula for more accurate waverider shape is established and by means of this new waverider configuration the reason for the shock stand-off which was detected in previous investigations is clarified in this paper. (Author)
Mousa, Mohamed G; Allam, S M; Rashad, Essam M
2018-01-01
This paper proposes an advanced strategy to synchronize the wind-driven Brushless Doubly-Fed Reluctance Generator (BDFRG) to the grid-side terminals. The proposed strategy depends mainly upon determining the electrical angle of the grid voltage, θ v and using the same transformation matrix of both the power winding and grid sides to ensure that the generated power-winding voltage has the same phase-sequence of the grid-side voltage. On the other hand, the paper proposes a vector-control (power-winding flux orientation) technique for maximum wind-power extraction under two schemes summarized as; unity power-factor operation and minimum converter-current. Moreover, a soft-starting method is suggested to avoid the employed converter over-current. The first control scheme is achieved by adjusting the command power-winding reactive power at zero for a unity power-factor operation. However, the second scheme depends on setting the command d-axis control-winding current at zero to maximize the ratio of the generator electromagnetic-torque per the converter current. This enables the system to get a certain command torque under minimum converter current. A sample of the obtained simulation and experimental results is presented to check the effectiveness of the proposed control strategies. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
International Nuclear Information System (INIS)
Patel, Amit; Sarkar, Prabir; Tyagi, Himanshu; Singh, Harpreet
2016-01-01
The environmental impact assessment of a process over its entire operational lifespan is an important issue. Estimation of life cycle emission helps in predicting the contribution of a given process to abate (or to pollute) the environmental emission scenario. Considering diminishing and time-dependent effect of emission, assessment of the overall effect of emissions is very complex. The paper presents a generalized methodology for arriving at a single emission discounting number for a process option, using the concept of time value of carbon emission flow. This number incorporates the effect of the emission resulting from the process over the entire operational lifespan. The advantage of this method is its quantitative aspect as well as its flexible nature. It can be applied to any process. The method is demonstrated with the help of an Intermediate Pyrolysis process when used to generate off-grid electricity and opting biochar route for disposing straw residue. The scenarios of very high net emission to very high net carbon sequestration is generated using process by careful selection of process parameters for different scenarios. For these different scenarios, the process discounting rate was determined and its outcome is discussed. The paper also proposes a process specific eco-label that mentions the discounting rates. - Highlight: • Methodology to obtain emission discounting rate for a process is proposed. • The method includes all components of life cycle emission converts into a time dependent discounting number. • A case study of Intermediate Pyrolysis is used to obtain such number for a range of processes. • The method is useful to determine if the effect from the operation of a process will lead to a net absorption of emission or net accumulation of emission in the environment.
Energy Technology Data Exchange (ETDEWEB)
Patel, Amit, E-mail: amitrp@iitrpr.ac.in [Indian Institute of Technology Ropar, Nangal Road, Rupnagar 140001, Punjab (India); Faculty of Technology and Engineering, The Maharaja Sayajirao University of Baroda, Vadodara 390001, Gujarat (India); Sarkar, Prabir; Tyagi, Himanshu; Singh, Harpreet [Indian Institute of Technology Ropar, Nangal Road, Rupnagar 140001, Punjab (India)
2016-07-15
The environmental impact assessment of a process over its entire operational lifespan is an important issue. Estimation of life cycle emission helps in predicting the contribution of a given process to abate (or to pollute) the environmental emission scenario. Considering diminishing and time-dependent effect of emission, assessment of the overall effect of emissions is very complex. The paper presents a generalized methodology for arriving at a single emission discounting number for a process option, using the concept of time value of carbon emission flow. This number incorporates the effect of the emission resulting from the process over the entire operational lifespan. The advantage of this method is its quantitative aspect as well as its flexible nature. It can be applied to any process. The method is demonstrated with the help of an Intermediate Pyrolysis process when used to generate off-grid electricity and opting biochar route for disposing straw residue. The scenarios of very high net emission to very high net carbon sequestration is generated using process by careful selection of process parameters for different scenarios. For these different scenarios, the process discounting rate was determined and its outcome is discussed. The paper also proposes a process specific eco-label that mentions the discounting rates. - Highlight: • Methodology to obtain emission discounting rate for a process is proposed. • The method includes all components of life cycle emission converts into a time dependent discounting number. • A case study of Intermediate Pyrolysis is used to obtain such number for a range of processes. • The method is useful to determine if the effect from the operation of a process will lead to a net absorption of emission or net accumulation of emission in the environment.
Rayson, Matthew D.; Ivey, Gregory N.; Jones, Nicole L.; Fringer, Oliver B.
2018-02-01
We apply the unstructured grid hydrodynamic model SUNTANS to investigate the internal wave dynamics around Scott Reef, Western Australia, an isolated coral reef atoll located on the edge of the continental shelf in water depths of 500,m and more. The atoll is subject to strong semi-diurnal tidal forcing and consists of two relatively shallow lagoons separated by a 500 m deep, 2 km wide and 15 km long channel. We focus on the dynamics in this channel as the internal tide-driven flow and resulting mixing is thought to be a key mechanism controlling heat and nutrient fluxes into the reef lagoons. We use an unstructured grid to discretise the domain and capture both the complex topography and the range of internal wave length scales in the channel flow. The model internal wave field shows super-tidal frequency lee waves generated by the combination of the steep channel topography and strong tidal flow. We evaluate the model performance using observations of velocity and temperature from two through water-column moorings in the channel separating the two reefs. Three different global ocean state estimate datasets (global HYCOM, CSIRO Bluelink, CSIRO climatology atlas) were used to provide the model initial and boundary conditions, and the model outputs from each were evaluated against the field observations. The scenario incorporating the CSIRO Bluelink data performed best in terms of through-water column Murphy skill scores of water temperature and eastward velocity variability in the channel. The model captures the observed vertical structure of the tidal (M2) and super-tidal (M4) frequency temperature and velocity oscillations. The model also predicts the direction and magnitude of the M2 internal tide energy flux. An energy analysis reveals a net convergence of the M2 energy flux and a divergence of the M4 energy flux in the channel, indicating the channel is a region of either energy transfer to higher frequencies or energy loss to dissipation. This conclusion is
Application of Chimera Composite Grid Scheme to Ship Appendages
National Research Council Canada - National Science Library
Lin, Cheng-Wen
1995-01-01
.... The chimera scheme of grid generation uses a system of relatively simple grids. The grids each define a particular component of the overall geometry, making the initial grid generation much simpler...
Bosman, M.G.C.
2012-01-01
The electricity supply chain is changing, due to increasing awareness for sustainability and an improved energy efficiency. The traditional infrastructure where demand is supplied by centralized generation is subject to a transition towards a Smart Grid. In this Smart Grid, sustainable generation
AbouEisha, Hassan M.; Moshkov, Mikhail; Calo, Victor M.; Paszynski, Maciej; Goik, Damian; Jopek, Konrad
2014-01-01
In this paper we present a dynamic programming algorithm for finding optimal elimination trees for computational grids refined towards point or edge singularities. The elimination tree is utilized to guide the multi-frontal direct solver algorithm
Smart grid technologies in local electric grids
Lezhniuk, Petro D.; Pijarski, Paweł; Buslavets, Olga A.
2017-08-01
The research is devoted to the creation of favorable conditions for the integration of renewable sources of energy into electric grids, which were designed to be supplied from centralized generation at large electric power stations. Development of distributed generation in electric grids influences the conditions of their operation - conflict of interests arises. The possibility of optimal functioning of electric grids and renewable sources of energy, when complex criterion of the optimality is balance reliability of electric energy in local electric system and minimum losses of electric energy in it. Multilevel automated system for power flows control in electric grids by means of change of distributed generation of power is developed. Optimization of power flows is performed by local systems of automatic control of small hydropower stations and, if possible, solar power plants.
International Nuclear Information System (INIS)
Choi, Dong Bae
2001-11-01
This book describes press smart grid from basics to recent trend. It is divided into ten chapters, which deals with smart grid as green revolution in energy with introduction, history, the fields, application and needed technique for smart grid, Trend of smart grid in foreign such as a model business of smart grid in foreign, policy for smart grid in U.S.A, Trend of smart grid in domestic with international standard of smart grid and strategy and rood map, smart power grid as infrastructure of smart business with EMS development, SAS, SCADA, DAS and PQMS, smart grid for smart consumer, smart renewable like Desertec project, convergence IT with network and PLC, application of an electric car, smart electro service for realtime of electrical pricing system, arrangement of smart grid.
Rational points on elliptic curves
Silverman, Joseph H
2015-01-01
The theory of elliptic curves involves a pleasing blend of algebra, geometry, analysis, and number theory. This book stresses this interplay as it develops the basic theory, thereby providing an opportunity for advanced undergraduates to appreciate the unity of modern mathematics. At the same time, every effort has been made to use only methods and results commonly included in the undergraduate curriculum. This accessibility, the informal writing style, and a wealth of exercises make Rational Points on Elliptic Curves an ideal introduction for students at all levels who are interested in learning about Diophantine equations and arithmetic geometry. Most concretely, an elliptic curve is the set of zeroes of a cubic polynomial in two variables. If the polynomial has rational coefficients, then one can ask for a description of those zeroes whose coordinates are either integers or rational numbers. It is this number theoretic question that is the main subject of this book. Topics covered include the geometry and ...
Near-Body Grid Adaption for Overset Grids
Buning, Pieter G.; Pulliam, Thomas H.
2016-01-01
A solution adaption capability for curvilinear near-body grids has been implemented in the OVERFLOW overset grid computational fluid dynamics code. The approach follows closely that used for the Cartesian off-body grids, but inserts refined grids in the computational space of original near-body grids. Refined curvilinear grids are generated using parametric cubic interpolation, with one-sided biasing based on curvature and stretching ratio of the original grid. Sensor functions, grid marking, and solution interpolation tasks are implemented in the same fashion as for off-body grids. A goal-oriented procedure, based on largest error first, is included for controlling growth rate and maximum size of the adapted grid system. The adaption process is almost entirely parallelized using MPI, resulting in a capability suitable for viscous, moving body simulations. Two- and three-dimensional examples are presented.
Energy Technology Data Exchange (ETDEWEB)
2012-07-01
The overall objective of this project was to design and build a combined heat and power plant based on an updraft gasifier and a 35 kW electrical output Stirling engine and further to test the flexibility of the plant with regards to fuel and application. In the project a containerized combined heat and power plant including a 200 kW updraft gasifier and a 35 kW electrical output Stirling engine was designed, the specified components were procured, the plant was installed in the three containers and the plant was erected at Amagerforbraendingen ready for the COP15 in November 2009. The potential of operating the Stirling engine in island-mode (without grid connection) was investigated by mathematical modelling. Using an absorption cooling plant connected to the Stirling CHP plant was also investigated. A technical feasibility study was undertaken and it was concluded that from the two available technologies (water/LiBr and Ammonia/water) the appropriate choice is depending on the required cooling temperature. Test runs focussed on investigating the fuel flexibility of two different configurations of Stirling engine CHP plants were carried out - respectively the updraft gasifier plant (the containerized plant and the DTU plant) and the pyrolysis plant (the plant situated at Barritskov). In order to perform these test runs a stable operation is required. On both the containerized plant and the pyrolysis plant this proved to be more challenging than expected and therefore the number of fuels tested was limited to willow chips at the containerized plant and dry wood residues, wood pellets and straw pellets on the pyrolysis plant. For all tested fuels it was possible to operate the plants, however different issues mainly related to the quality of the fuels were encountered. And so it can be concluded that the quality of the fuel is critical for the operation of both the updraft gasifier plant and the pyrolysis plant. A comprehensive desktop evaluation of the feasibility
Energy Technology Data Exchange (ETDEWEB)
Luechinger, P.
2003-07-01
This is the fifth part of a ten-part final report for the Swiss Federal Office of Energy (SFOE) on a project that looked into potential problems relating to the Swiss electricity distribution grid with respect to the increasing number of distributed power generation facilities being put into service. The identification of special conditions for the grid's operation and future development that take increasing decentralised power production into account are discussed. The results of the project activities encompass the analysis and evaluation of various problem areas associated with planning and management of the grid during normal operation and periods of malfunction, as well as required modifications to safety systems and grid configurations. This fourth appendix to the main report describes six ways of storing electricity, including accumulators, super caps, super-conducting magnetic and flywheel energy storage units. The accumulator technologies discussed include lead-acid, nickel-cadmium and sodium-sulphur batteries. Each of these types of power storage technologies is briefly described. The characteristics of these various types of storage are compared.
Energy and the Elliptical Orbit
Nettles, Bill
2009-03-01
In the January 2007 issue of The Physics Teacher, Prentis, Fulton, Hesse, and Mazzino describe a laboratory exercise in which students use a geometrical analysis inspired by Newton to show that an elliptical orbit and an inverse-square law force go hand in hand. The historical, geometrical, and teamwork aspects of the exercise are useful and important. This paper presents an exercise which uses an energy/angular momentum conservation model for elliptical orbits. This exercise can be done easily by an individual student and on regular notebook-sized paper.
Interstellar matter within elliptical galaxies
Jura, Michael
1988-01-01
Multiwavelength observations of elliptical galaxies are reviewed, with an emphasis on their implications for theoretical models proposed to explain the origin and evolution of the interstellar matter. Particular attention is given to interstellar matter at T less than 100 K (atomic and molecular gas and dust), gas at T = about 10,000 K, and gas at T = 10 to the 6th K or greater. The data are shown to confirm the occurrence of mass loss from evolved stars, significant accretion from companion galaxies, and cooling inflows; no evidence is found for large mass outflow from elliptical galaxies.
Elliptic net and its cryptographic application
Muslim, Norliana; Said, Mohamad Rushdan Md
2017-11-01
Elliptic net is a generalization of elliptic divisibility sequence and in cryptography field, most cryptographic pairings that are based on elliptic curve such as Tate pairing can be improved by applying elliptic nets algorithm. The elliptic net is constructed by using n dimensional array of values in rational number satisfying nonlinear recurrence relations that arise from elliptic divisibility sequences. The two main properties hold in the recurrence relations are for all positive integers m>n, hm +nhm -n=hm +1hm -1hn2-hn +1hn -1hm2 and hn divides hm whenever n divides m. In this research, we discuss elliptic divisibility sequence associated with elliptic nets based on cryptographic perspective and its possible research direction.
Coercive properties of elliptic-parabolic operator
International Nuclear Information System (INIS)
Duong Min Duc.
1987-06-01
Using a generalized Poincare inequality, we study the coercive properties of a class of elliptic-parabolic partial differential equations, which contains many degenerate elliptic equations considered by the other authors. (author). 16 refs
DEFF Research Database (Denmark)
Lar, Ionut Andrei; Radulescu, Mircea; Ritchie, Ewen
2012-01-01
A comparison between two current control methods of grid side inverter, PI current control and Robust Forward control is made. PI control is implemented in d-q synchronous frame while Forward is implemented in abc stationary frames.The report contains both simulations and experimental test wich...
Diffeomorphisms of elliptic 3-manifolds
Hong, Sungbok; McCullough, Darryl; Rubinstein, J Hyam
2012-01-01
This work concerns the diffeomorphism groups of 3-manifolds, in particular of elliptic 3-manifolds. These are the closed 3-manifolds that admit a Riemannian metric of constant positive curvature, now known to be exactly the closed 3-manifolds that have a finite fundamental group. The (Generalized) Smale Conjecture asserts that for any elliptic 3-manifold M, the inclusion from the isometry group of M to its diffeomorphism group is a homotopy equivalence. The original Smale Conjecture, for the 3-sphere, was proven by J. Cerf and A. Hatcher, and N. Ivanov proved the generalized conjecture for many of the elliptic 3-manifolds that contain a geometrically incompressible Klein bottle. The main results establish the Smale Conjecture for all elliptic 3-manifolds containing geometrically incompressible Klein bottles, and for all lens spaces L(m,q) with m at least 3. Additional results imply that for a Haken Seifert-fibered 3 manifold V, the space of Seifert fiberings has contractible components, and apart from a small...
Elliptic curves and primality proving
Atkin, A. O. L.; Morain, F.
1993-07-01
The aim of this paper is to describe the theory and implementation of the Elliptic Curve Primality Proving algorithm. Problema, numeros primos a compositis dignoscendi, hosque in factores suos primos resolvendi, ad gravissima ac utilissima totius arithmeticae pertinere, et geometrarum tum veterum tum recentiorum industriam ac sagacitatem occupavisse, tam notum est, ut de hac re copiose loqui superfluum foret.
Color gradients in elliptical galaxies
International Nuclear Information System (INIS)
Franx, M.; Illingworth, G.
1990-01-01
The relationship of the color gradients within ellipticals and the color differences between them are studied. It is found that the local color appears to be strongly related to the escape velocity. This suggests that the local escape velocity is the primary factor that determines the metallicity of the stellar population. Models with and without dark halos give comparable results. 27 refs
Second order degenerate elliptic equations
International Nuclear Information System (INIS)
Duong Minh Duc.
1988-08-01
Using an improved Sobolev inequality we study a class of elliptic operators which is degenerate inside the domain and strongly degenerate near the boundary of the domain. Our results are applicable to the L 2 -boundary value problem and the mixed boundary problem. (author). 18 refs
Elliptic Genera of Symmetric Products and Second Quantized Strings
Dijkgraaf, R; Verlinde, Erik; Verlinde, Herman L
1997-01-01
In this note we prove an identity that equates the elliptic genus partition function of a supersymmetric sigma model on the $N$-fold symmetric product $M^N/S_N$ of a manifold $M$ to the partition function of a second quantized string theory on the space $M \\times S^1$. The generating function of these elliptic genera is shown to be (almost) an automorphic form for $O(3,2,\\Z)$. In the context of D-brane dynamics, this result gives a precise computation of the free energy of a gas of D-strings inside a higher-dimensional brane.
Elliptical shape of the coma cluster
International Nuclear Information System (INIS)
Schipper, L.; King, I.R.
1978-01-01
The elliptical shape of the Coma cluster is examined quantitatively. The degree of ellipticity is high and depends to some extent on the radial distance of the sample from the Coma center as well as on the brightness of the sample. The elliptical shape does not appear to be caused by rotation; other possible causes are briefly discussed
A class of strongly degenerate elliptic operators
International Nuclear Information System (INIS)
Duong Minh Duc.
1988-04-01
Using a weighted Poincare inequality, we study (ω 1 ,...,ω n )-elliptic operators. This method is applicable to solve singular elliptic equations with conditions in W 1,2 on the boundary. We also get a result about the regularity of solutions of singular elliptic equations. An application to (ω 1 ,...ω n )-parabolic equations is given. (author). 33 refs
AbouEisha, Hassan M.
2014-06-06
In this paper we present a dynamic programming algorithm for finding optimal elimination trees for computational grids refined towards point or edge singularities. The elimination tree is utilized to guide the multi-frontal direct solver algorithm. Thus, the criterion for the optimization of the elimination tree is the computational cost associated with the multi-frontal solver algorithm executed over such tree. We illustrate the paper with several examples of optimal trees found for grids with point, isotropic edge and anisotropic edge mixed with point singularity. We show the comparison of the execution time of the multi-frontal solver algorithm with results of MUMPS solver with METIS library, implementing the nested dissection algorithm.
Aklin, Michaël; Bayer, Patrick; Harish, S P; Urpelainen, Johannes
2017-05-01
This article assesses the socioeconomic effects of solar microgrids. The lack of access to electricity is a major obstacle to the socioeconomic development of more than a billion people. Off-grid solar technologies hold potential as an affordable and clean solution to satisfy basic electricity needs. We conducted a randomized field experiment in India to estimate the causal effect of off-grid solar power on electricity access and broader socioeconomic development of 1281 rural households. Within a year, electrification rates in the treatment group increased by 29 to 36 percentage points. Daily hours of access to electricity increased only by 0.99 to 1.42 hours, and the confidence intervals are wide. Kerosene expenditure on the black market decreased by 47 to 49 rupees per month. Despite these strong electrification and expenditure effects, we found no systematic evidence for changes in savings, spending, business creation, time spent working or studying, or other broader indicators of socioeconomic development.
Controlling smart grid adaptivity
Toersche, Hermen; Nykamp, Stefan; Molderink, Albert; Hurink, Johann L.; Smit, Gerardus Johannes Maria
2012-01-01
Methods are discussed for planning oriented smart grid control to cope with scenarios with limited predictability, supporting an increasing penetration of stochastic renewable resources. The performance of these methods is evaluated with simulations using measured wind generation and consumption
Energy Technology Data Exchange (ETDEWEB)
Malte, C. T.
2007-07-01
The importance of renewable energy sources and combined heat and power generation for electricity production will further increase in the next years, not only in Germany but all over Europe. Beside the conventional more or less centrally organised generation and distribution structure, more and more distributed generation (DG) units of different technologies will come to the forefront. Today's centrally organised electricity supply structure is comparatively stable, relatively simple to control and guarantees a high degree of supply quality. But it requests large investments with a long commitment, is less flexible and can barely use efficiency potentials. Distribution grids (low and medium voltage) are essentially passive; this means that the network management is carried out at the higher voltage levels. As more and more DG units feed in the grid, the distribution grids have to become more 'active'. With a high share of wind power, combined heat and power as well as photovoltaic generation, more duties of grid management have to be carried out at the point of common coupling of DG units. This requests for more communication und new control strategies in the distribution grids. At the same time grids with DG have in the mid-term the potential to reduce the susceptibility for large scale black-outs, because, on one hand, with a high number of smaller and individually controlled DG units the breakdown of one unit does not have a major impact and, on the other hand, with a specific grid management the option exists to build up islanded grids during interruptions on the higher voltage levels and to continue to supply the connected customers. In the European research project 'DISPOWER' 38 institutions from all over Europe dealt these topics. In this context a new kind of energy management system for low voltage grids was developed: 'PoMS'. PoMS is the acronym for 'Power Flow and Power Quality Management System'. Major
Energy Technology Data Exchange (ETDEWEB)
Malte, C T
2007-07-01
The importance of renewable energy sources and combined heat and power generation for electricity production will further increase in the next years, not only in Germany but all over Europe. Beside the conventional more or less centrally organised generation and distribution structure, more and more distributed generation (DG) units of different technologies will come to the forefront. Today's centrally organised electricity supply structure is comparatively stable, relatively simple to control and guarantees a high degree of supply quality. But it requests large investments with a long commitment, is less flexible and can barely use efficiency potentials. Distribution grids (low and medium voltage) are essentially passive; this means that the network management is carried out at the higher voltage levels. As more and more DG units feed in the grid, the distribution grids have to become more 'active'. With a high share of wind power, combined heat and power as well as photovoltaic generation, more duties of grid management have to be carried out at the point of common coupling of DG units. This requests for more communication und new control strategies in the distribution grids. At the same time grids with DG have in the mid-term the potential to reduce the susceptibility for large scale black-outs, because, on one hand, with a high number of smaller and individually controlled DG units the breakdown of one unit does not have a major impact and, on the other hand, with a specific grid management the option exists to build up islanded grids during interruptions on the higher voltage levels and to continue to supply the connected customers. In the European research project 'DISPOWER' 38 institutions from all over Europe dealt these topics. In this context a new kind of energy management system for low voltage grids was developed: 'PoMS'. PoMS is the acronym for 'Power Flow and Power Quality Management System'. Major targets during development were that the system is
Elliptic Diophantine equations a concrete approach via the elliptic logarithm
Tzanakis, Nikos
2013-01-01
This book presents in a unified way the beautiful and deep mathematics, both theoretical and computational, on which the explicit solution of an elliptic Diophantine equation is based. It collects numerous results and methods that are scattered in literature. Some results are even hidden behind a number of routines in software packages, like Magma. This book is suitable for students in mathematics, as well as professional mathematicians.
Kumar, A.
2017-01-01
The Indian Smart Grid Forum defines a smart grid as "a power system capable of two-way communication between all the entities of the network-generation, transmission, distribution and the consumers". Like most work on smart grids, this view is also mainly technical. This paper aims to progress the
International Nuclear Information System (INIS)
Roche, Robin
2012-01-01
Due to the convergence of several profound trends in the energy sector, smart grids are emerging as the main paradigm for the modernization of the electric grid. Smart grids hold many promises, including the ability to integrate large shares of distributed and intermittent renewable energy sources, energy storage and electric vehicles, as well as the promise to give consumers more control on their energy consumption. Such goals are expected to be achieved through the use of multiple technologies, and especially of information and communication technologies, supported by intelligent algorithms. These changes are transforming power grids into even more complex systems, that require suitable tools to model, simulate and control their behaviors. In this dissertation, properties of multi-agent systems are used to enable a new systemic approach to energy management, and allow for agent-based architectures and algorithms to be defined. This new approach helps tackle the complexity of a cyber-physical system such as the smart grid by enabling the simultaneous consideration of multiple aspects such as power systems, the communication infrastructure, energy markets, and consumer behaviors. The approach is tested in two applications: a 'smart' energy management system for a gas turbine power plant, and a residential demand response system. An energy management system for gas turbine power plants is designed with the objective to minimize operational costs and emissions, in the smart power generation paradigm. A gas turbine model based on actual data is proposed, and used to run simulations with a simulator specifically developed for this problem. A meta-heuristic achieves dynamic dispatch among gas turbines according to their individual characteristics. Results show that the system is capable of operating the system properly while reducing costs and emissions. The computing and communication requirements of the system, resulting from the selected architecture, are
Energy Technology Data Exchange (ETDEWEB)
Bendel, C.; Dallinger, D.; Nestle, D.; Ringelstein, J. [ISET e.V., Kassel (Germany)
2008-07-01
In the context of growing installation of decentralized and fluctuating generation in the low voltage grid, energy management in this grid level becomes more and more important. In the research project DINAR, an approach therefor was developed and implemented. This approach combines automatic management of loads and decentralized generators by decentral decision, customer information and interaction, meter reading and low voltage grid measurement. This paper covers the developed concept and results from the field test in project DINAR as well as currently ongoing research activity on possible applications. (orig.)
Development of a superconducting elliptically polarized undulator
International Nuclear Information System (INIS)
Chen, S D; Liang, K S; Jan, J C; Hwang, C S
2010-01-01
A superconducting, elliptically polarized undulator (SEPU24) with a period of length 24 mm was developed to provide first-harmonic photons from a 0.8 GeV storage ring for extreme-ultraviolet (EUV) lithography experiment. In SEPU24, two layers of a magnet array structure - with and without rotated magnet arrays - are combined to generate a helical field that provides radiation with wavelength 13.5 nm in the in-band energy. The arrays of iron and aluminium poles were wound with a racetrack coil vertically as for the magnet pole array. The elliptical field is created when the up and down magnet-pole arrays pass excitation currents in alternate directions. SEPU24 is designed with a magnet of gap 6.8 mm, yielding magnetic flux density B x =B z =0.61 T of the helical field. A prototype magnet was fabricated with a diode for quench protection, and assembled in a test dewar to test the magnet performance. A cryogenic Hall-probe system with a precise linear stage was used to measure the distribution of the magnetic field. We describe the design concept and algorithm, the engineering design, the calculation of the magnetic field, the construction and testing of the 10-pole prototype magnet and related issues.
Dar, Zamiyad
The prices in the electricity market change every five minutes. The prices in peak demand hours can be four or five times more than the prices in normal off peak hours. Renewable energy such as wind power has zero marginal cost and a large percentage of wind energy in a power grid can reduce the price significantly. The variability of wind power prevents it from being constantly available in peak hours. The price differentials between off-peak and on-peak hours due to wind power variations provide an opportunity for a storage device owner to buy energy at a low price and sell it in high price hours. In a large and complex power grid, there are many locations for installation of a storage device. Storage device owners prefer to install their device at locations that allow them to maximize profit. Market participants do not possess much information about the system operator's dispatch, power grid, competing generators and transmission system. The publicly available data from the system operator usually consists of Locational Marginal Prices (LMP), load, reserve prices and regulation prices. In this thesis, we develop a method to find the optimum location of a storage device without using the grid, transmission or generator data. We formulate and solve an optimization problem to find the most profitable location for a storage device using only the publicly available market pricing data such as LMPs, and reserve prices. We consider constraints arising due to storage device operation limitations in our objective function. We use binary optimization and branch and bound method to optimize the operation of a storage device at a given location to earn maximum profit. We use two different versions of our method and optimize the profitability of a storage unit at each location in a 36 bus model of north eastern United States and south eastern Canada for four representative days representing four seasons in a year. Finally, we compare our results from the two versions of our
Halem, M.; Yesha, Y.; Tilmes, C.; Chapman, D.; Goldberg, M.; Zhou, L.
2007-05-01
Three decades of Earth remote sensing from NASA, NOAA and DOD operational and research satellites carrying successive generations of improved atmospheric sounder instruments have resulted in petabytes of radiance data with varying spatial and spectral resolutions being stored at different data archives in various data formats by the respective agencies. This evolution of sounders and the diversities of these archived data sets have led to data processing obstacles limiting the science community from readily accessing and analyzing such long-term climate data records. We address this problem by the development of a web based Service Oriented Atmospheric Radiance (SOAR) system built on the SOA paradigm that makes it practical for the science community to dynamically access, manipulate and generate long term records of L1 pre-gridded sounding radiances of coincident multi-sensor data for regions specified according to user chosen criteria. SOAR employs a modification of the standard Client Server interactions that allows users to represent themselves directly to the Process Server through their own web browsers. The browser uses AJAX to request Javascript libraries and DHTML interfaces that define the possible client interactions and communicates the SOAP messages to the Process server allowing for dynamic web dialogs with the user to take place on the fly. The Process Server is also connected to an underlying high performance compute cluster and storage system which provides much of the data processing capabilities required to service the client requests. The compute cluster employs optical communications to NOAA and NASA for accessing the data and under the governance of the Process Server invokes algorithms for on-demand spatial, temporal, and spectral gridding. Scientists can choose from a variety of statistical averaging techniques for compositing satellite observed sounder radiances from the AIRS, AMSU or MODIS instruments to form spatial-temporal grids for
Energy Technology Data Exchange (ETDEWEB)
Raju, A.B.; Fernandes, B.G.; Chatterjee, K. [Indian Institute of Technology, Mumbai (India). Dept. of Electrical Engineering
2004-07-01
In this paper, modelling and simulation of a grid connected variable speed wind energy conversion system (VSWECS) with reduced switch count power converter is presented. The system consists of a permanent magnet synchronous generator (PMSG), two-pulse width modulated B-4 power converters and a maximum power point tracker (MPPT). Mathematical models of each element of the system are developed separately and are then integrated to simulate the whole system for various wind velocities. The complete system is simulated using MATLAB/SIMULINK and simulation results are presented. (author)
DEFF Research Database (Denmark)
Liu, Hongzhi; Chen, Zhe
2012-01-01
This paper describes fault ride-through and grid support of offshore wind farms based on permanent magnet synchronous generator (PMSG) wind turbines connected to the onshore AC network through two alternative transmission systems: high voltage AC (HVAC) or high voltage DC (HVDC) based on voltage...... source converters (VSC). The proposed configurations of the PMSG-based offshore wind farm and VSC-based HVDC are given as well as their control strategies under both steady state and fault state. The PMSG-based offshore wind farm is integrated into a test power transmission system via either HVAC or VSC...
Elliptical and lenticular galaxies evolution
International Nuclear Information System (INIS)
Vigroux, L.
1981-01-01
Different evolutionnary models for elliptical and lenticular galaxies are discussed. In the first part, we show that, at least some peculiar early types galaxies exhibit some activity. Then we describe the observationnal constraints: the color-magnitude diagram, the color gradient and the high metallicity of intraclusters gas. Among the different models, only the dissipation collapse followed by a hot wind driven by supernovae explosion explain in a natural way these constraints. Finally, the origin of SO is briefly discussed [fr
Holomorphic bundles over elliptic manifolds
International Nuclear Information System (INIS)
Morgan, J.W.
2000-01-01
In this lecture we shall examine holomorphic bundles over compact elliptically fibered manifolds. We shall examine constructions of such bundles as well as (duality) relations between such bundles and other geometric objects, namely K3-surfaces and del Pezzo surfaces. We shall be dealing throughout with holomorphic principal bundles with structure group GC where G is a compact, simple (usually simply connected) Lie group and GC is the associated complex simple algebraic group. Of course, in the special case G = SU(n) and hence GC = SLn(C), we are considering holomorphic vector bundles with trivial determinant. In the other cases of classical groups, G SO(n) or G = Sympl(2n) we are considering holomorphic vector bundles with trivial determinant equipped with a non-degenerate symmetric, or skew symmetric pairing. In addition to these classical cases there are the finite number of exceptional groups. Amazingly enough, motivated by questions in physics, much interest centres around the group E8 and its subgroups. For these applications it does not suffice to consider only the classical groups. Thus, while often first doing the case of SU(n) or more generally of the classical groups, we shall extend our discussions to the general semi-simple group. Also, we shall spend a good deal of time considering elliptically fibered manifolds of the simplest type, namely, elliptic curves
Klotz, Wolf-Dieter
2005-01-01
Grid technology is widely emerging. Grid computing, most simply stated, is distributed computing taken to the next evolutionary level. The goal is to create the illusion of a simple, robust yet large and powerful self managing virtual computer out of a large collection of connected heterogeneous systems sharing various combinations of resources. This talk will give a short history how, out of lessons learned from the Internet, the vision of Grids was born. Then the extensible anatomy of a Grid architecture will be discussed. The talk will end by presenting a selection of major Grid projects in Europe and US and if time permits a short on-line demonstration.
International Nuclear Information System (INIS)
Takagi, T.; Miki, K.; Chen, B.C.J.; Sha, W.T.
1985-01-01
A new method is presented for numerically generating boundary-fitted coordinate systems for arbitrarily curved surfaces. The three-dimensional surface has been expressed by functions of two parameters using the geometrical modeling techniques in computer graphics. This leads to new quasi-one- and two-dimensional elliptic partial differential equations for coordinate transformation. Since the equations involve the derivatives of the surface expressions, the grids geneated by the equations distribute on the surface depending on its slope and curvature. A computer program GRID-CS based on the method was developed and applied to a surface of the second order, a torus and a surface of a primary containment vessel for a nuclear reactor. These applications confirm that GRID-CS is a convenient and efficient tool for grid generation on arbitrarily curved surfaces
International Nuclear Information System (INIS)
Passey, Robert; Spooner, Ted; MacGill, Iain; Watt, Muriel; Syngellakis, Katerina
2011-01-01
Distributed generation is being deployed at increasing levels of penetration on electricity grids worldwide. It can have positive impacts on the network, but also negative impacts if integration is not properly managed. This is especially true of photovoltaics, in part because it's output fluctuates significantly and in part because it is being rapidly deployed in many countries. Potential positive impacts on grid operation can include reduced network flows and hence reduced losses and voltage drops. Potential negative impacts at high penetrations include voltage fluctuations, voltage rise and reverse power flow, power fluctuations, power factor changes, frequency regulation and harmonics, unintentional islanding, fault currents and grounding issues. This paper firstly reviews each of these impacts in detail, along with the current technical approaches available to address them. The second section of this paper discusses key non-technical factors, such as appropriate policies and institutional frameworks, which are essential to effectively coordinate the development and deployment of the different technical solutions most appropriate for particular jurisdictions. These frameworks will be different for different jurisdictions, and so no single approach will be appropriate worldwide. - Highlights: → Distributed generation can have both positive and negative impacts on networks. → Technical solutions to address these negative impacts are discussed. → The required appropriate policies and institutional frameworks are discussed.
DEFF Research Database (Denmark)
Diaz de Cerio Mendaza, Iker; Pigazo, Alberto; Bak-Jensen, Birgitte
2013-01-01
at household level. Despite of the well-known flexible service that this kind of loads can provide, their flexibility is highly dependent of the domestic hot water and space heating demand and the driving habits of each user. This paper presents two methodologies employed to randomly generate thermal power......The changes in the Danish energy sector, consequence of political agreements, are expected to have direct impact in the actual power distribution systems. Large number of electric boiler, heat pumps and electric vehicles are planned and will cope large percentage of the future power consumption...... demand and electric vehicle driving profiles, to be used for power grid calculations. The generated thermal profiles relied on a statistical analysis made from real domestic hot water and space heating data from 25 households of a typical Danish residential area. The driving profiles instead were formed...
Energy Technology Data Exchange (ETDEWEB)
Schlebusch, V.; Wolff, M.; Nestle, D. [Inst. fuer Solare Energieversorgungstechnik e.V. (ISET), Kassel (Germany); Gjardy, G. [BTU Cottbus, Lehrstuhl Dezentrale Energiesysteme und Speichertechnik (DES), Cottbus (Germany); Borchard, Th. [RWTH Aachen, Inst. fuer Elektrische Anlagen und Energiewirtschaft (IAEW), Aachen (Germany); Bukvic-Schaefer, A.S. [Univ. Kassel, Fachgebiet Rationelle Energiewandlung (IEE-RE), Kassel (Germany); Erge, Th. [Fraunhofer-Inst. fuer Solare Energiesysteme (ISE), Freiburg (Germany); Klobasa, M. [Fraunhofer Inst. fuer System- und Innovationsforschung (ISI), Karlsruhe (Germany); Hollmann, M. [Univ. Paderborn, Fachgebiet Nachhaltige Energiekonzepte (NEK), Paderborn (Germany)
2006-07-01
In order to achieve the European Union objectives of increasing the share of energy from renewable sources and from combined heat and power plants, new distributed generation units with different supply characteristics will have to be integrated in the nearer future into the existing power supply system (medium and low voltage grids). The use of these new distributed power producers opens up whole new possibilities for optimizing the system integration which however do necessitate more advanced system management strategies. Therefore the main objective of the working group 'energy management and system strategies', within the thematic network 'Energie und Kommunikation', was to investigate a market compatible and integrated energy management consisting of specific resource scheduling for individual power producers and of dedicated load management concepts. With this background, the working group developed an advanced energy management concept for distributed generation units and loads and specified the corresponding communication requirements respectively. (orig.)
Intrinsic shapes of discy and boxy ellipticals
International Nuclear Information System (INIS)
Fasano, Giovanni
1991-01-01
Statistical tests for intrinsic shapes of elliptical galaxies have given so far inconclusive and sometimes contradictory results. These failures have been often charged to the fact that classical tests consider only the two axisymmetric shapes (oblate versus prolate), while ellipticals are truly triaxial bodies. On the other hand, recent analyses indicate that the class of elliptical galaxies could be a mixture of (at least) two families having different morphology and dynamical behaviour: (i) a family of fast-rotating, disc-like ellipticals (discy); (ii) a family of slow-rotating, box-shaped ellipticals (boxy). In this paper we review the tests for instrinsic shapes of elliptical galaxies using data of better quality (CCD) with respect to previous applications. (author)
Overdetermined elliptic problems in topological disks
Mira, Pablo
2018-06-01
We introduce a method, based on the Poincaré-Hopf index theorem, to classify solutions to overdetermined problems for fully nonlinear elliptic equations in domains diffeomorphic to a closed disk. Applications to some well-known nonlinear elliptic PDEs are provided. Our result can be seen as the analogue of Hopf's uniqueness theorem for constant mean curvature spheres, but for the general analytic context of overdetermined elliptic problems.
Flattening and radio emission among elliptical galaxies
International Nuclear Information System (INIS)
Disney, M.J.; Sparks, W.B.; Wall, J.V.
1984-01-01
In a sample of 132 bright elliptical galaxies it is shown that there is a strong correlation between radio activity and flattening in the sense that radio ellipticals are both apparently and inherently rounder than the average elliptical. Both extended and compact sources are subject to the same correlation. No galaxies with axial ratios below 0.65 are found to be radio emitters. (author)
Elliptic hypergeometric functions associated with root systems
Rosengren, Hjalmar; Warnaar, S. Ole
2017-01-01
We give a survey of elliptic hypergeometric functions associated with root systems, comprised of three main parts. The first two form in essence an annotated table of the main evaluation and transformation formulas for elliptic hypergeometric integeral and series on root systems. The third and final part gives an introduction to Rains' elliptic Macdonald-Koornwinder theory (in part also developed by Coskun and Gustafson).
Directory of Open Access Journals (Sweden)
Tilahun Nigussie
2017-07-01
Full Text Available Electricity supply in Ethiopia is extremely antiquated. Most of the remote rural areas of Ethiopia are not yet electrified. Electrifying these remote areas by extending grid system is difficult and costly. Melkey Hera village is one of a rural community situated in western Ethiopia. In this village, extension of the grid is not yet practical. As the current international trend in rural electrification is to utilize renewable energy resources; solar, wind, biomass, and micro hydro power systems can be seen as alternatives. Therefore, the target of this paper is to investigate the viability of a micro hydro, Photo Voltaic (PV and Diesel Generator-battery hybrid power system options to come up with the best techno-economic and optimum configuration for supplying electricity to this village. The study was performed by an assessment of the predicted village energy demand, the available renewable energy resources, and then using the software called HOMER. The best hybrid system type was described and the optimization of the system configuration was also done. Furthermore, through the simulation of different configuration of the supply system, the optimal mini-grid hybrid system design was established to combine hydro, solar PV, battery energy storage and diesel generator. This system demonstrated to be more reliable in operation, and the most cost-effective for the required level of service. The role of energy storage in system operation also demonstrated to offer additional operational advantages in-terms of reliability and cost savings. Overall, the design results show that the majority of energy obtained from hydropower, which accounts 79%, the PV module covers 20%, and diesel generator is only 1% of the total load consumption. The obtained hybrid system is cost competitive with $\\$$0.133/kWh, which is somewhat good to satisfy the community needs. However, this is more than current energy price in Ethiopia which $\\$$0.06/kWh. If due-merit given
Arbitrarily elliptical-cylindrical invisible cloaking
International Nuclear Information System (INIS)
Jiang Weixiang; Cui Tiejun; Yu Guanxia; Lin Xianqi; Cheng Qiang; Chin, J Y
2008-01-01
Based on the idea of coordinate transformation (Pendry, Schurig and Smith 2006 Science 312 1780), arbitrarily elliptical-cylindrical cloaks are proposed and designed. The elliptical cloak, which is composed of inhomogeneous anisotropic metamaterials in an elliptical-shell region, will deflect incoming electromagnetic (EM) waves and guide them to propagate around the inner elliptical region. Such EM waves will return to their original propagation directions without distorting the waves outside the elliptical cloak. General formulations of the inhomogeneous and anisotropic permittivity and permeability tensors are derived for arbitrarily elliptical axis ratio k, which can also be used for the circular cloak when k = 1. Hence the elliptical cloaks can make a large range of objects invisible, from round objects (when k approaches 1) to long and thin objects (when k is either very large or very small). We also show that the material parameters in elliptical cloaking are singular at only two points, instead of on the whole inner circle for circular cloaking, which are much easier to be realized in actual applications. Full-wave simulations are given to validate the arbitrarily elliptical cloaking
Elliptic-symmetry vector optical fields.
Pan, Yue; Li, Yongnan; Li, Si-Min; Ren, Zhi-Cheng; Kong, Ling-Jun; Tu, Chenghou; Wang, Hui-Tian
2014-08-11
We present in principle and demonstrate experimentally a new kind of vector fields: elliptic-symmetry vector optical fields. This is a significant development in vector fields, as this breaks the cylindrical symmetry and enriches the family of vector fields. Due to the presence of an additional degrees of freedom, which is the interval between the foci in the elliptic coordinate system, the elliptic-symmetry vector fields are more flexible than the cylindrical vector fields for controlling the spatial structure of polarization and for engineering the focusing fields. The elliptic-symmetry vector fields can find many specific applications from optical trapping to optical machining and so on.
Doppler Velocity Signatures of Idealized Elliptical Vortices
Directory of Open Access Journals (Sweden)
Wen-Chau Lee
2006-01-01
Full Text Available Doppler radar observations have revealed a class of atmospheric vortices (tropical cyclones, tornadoes, dust devils that possess elliptical radar reflectivity signatures. One famous example is Typhoon Herb (1996 that maintained its elliptical reflectivity structure over a 40-hour period. Theoretical work and dual-Doppler analyses of observed tropical cyclones have suggested two physical mechanisms that can explain the formation of two types of elliptical vortices observed in nature, namely, the combination of a circular vortex with either a wavenumber two vortex Rossby wave or a deformation field. The characteristics of these two types of elliptical vortices and their corresponding Doppler velocity signatures have not been previously examined.
Energy Technology Data Exchange (ETDEWEB)
Barbaro, M. [ENEA, Centro Ricerche `Ezio Clementel`, Bologna (Italy). Dipt. Innovazione
1997-11-01
A numerical method is described which generates an orthogonal curvilinear mesh, subject to the constraint that mesh lines are matched to all boundaries of a closed, simply connected two-dimensional region of arbitrary shape. The method is based on the solution, by an iterative finite-difference technique, of an elliptic differential system of equations for the Cartesian coordinates of the orthogonal grid nodes. The interior grid distribution is controlled by a technique which ensures that coordinate lines can be concentrated as desired. Examples of orthogonal meshes inscribed in various geometrical figures are included.
Dark matter in elliptical galaxies
Carollo, C. M.; Zeeuw, P. T. DE; Marel, R. P. Van Der; Danziger, I. J.; Qian, E. E.
1995-01-01
We present measurements of the shape of the stellar line-of-sight velocity distribution out to two effective radii along the major axes of the four elliptical galaxies NGC 2434, 2663, 3706, and 5018. The velocity dispersion profiles are flat or decline gently with radius. We compare the data to the predictions of f = f(E, L(sub z)) axisymmetric models with and without dark matter. Strong tangential anisotropy is ruled out at large radii. We conclude from our measurements that massive dark halos must be present in three of the four galaxies, while for the fourth galaxy (NGC 2663) the case is inconclusive.
Stellar Populations in Elliptical Galaxies
Angeletti, Lucio; Giannone, Pietro
The R1/n law for the radial surface brightness of elliptical galaxies and the "Best Accretion Model" together with the "Concentration Model" have been combined in order to determine the mass and dynamical structure of largely-populated star systems. Families of models depending on four parameters have been used to fit the observed surface radial profiles of some spectro-photometric indices of a sample of eleven galaxies. We present the best agreements of the spectral index Mg2 with observations for three selected galaxies representative of the full sample. For them we have also computed the spatial distributions of the metal abundances, which are essential to achieve a population synthesis.
The Closest Point Method and Multigrid Solvers for Elliptic Equations on Surfaces
Chen, Yujia
2015-01-01
© 2015 Society for Industrial and Applied Mathematics. Elliptic partial differential equations are important from both application and analysis points of view. In this paper we apply the closest point method to solve elliptic equations on general curved surfaces. Based on the closest point representation of the underlying surface, we formulate an embedding equation for the surface elliptic problem, then discretize it using standard finite differences and interpolation schemes on banded but uniform Cartesian grids. We prove the convergence of the difference scheme for the Poisson\\'s equation on a smooth closed curve. In order to solve the resulting large sparse linear systems, we propose a specific geometric multigrid method in the setting of the closest point method. Convergence studies in both the accuracy of the difference scheme and the speed of the multigrid algorithm show that our approaches are effective.
Directory of Open Access Journals (Sweden)
Ren-Shiou Liu
2016-08-01
Full Text Available In this paper, the problem of minimizing electricity cost and the peak system load in smart grids with distributed renewable energy resources is studied. Unlike prior research works that either assume all of the jobs are interruptible or power-shiftable, this paper focuses on more challenging scenarios in which jobs are non-interruptible and non-power-shiftable. In addition, as more and more newly-built homes have rooftop solar arrays, it is assumed that all users are equipped with a solar-plus-battery system in this paper. Thus, power can be drawn from the battery as needed to reduce the cost of electricity or to lower the overall system load. With a quadratic load-dependent cost function, this paper first shows that the electricity cost minimization problem in such a setting is NP-hard and presents a distributed demand-side management algorithm, called DDSM, to solve this. Experimental results show that the proposed DDSM algorithm is effective, scalable and converges to a Nash equilibrium in finite rounds.
International Nuclear Information System (INIS)
Xi, Lei; Yu, Tao; Yang, Bo; Zhang, Xiaoshun
2015-01-01
Highlights: • Proposing a decentralized smart generation control scheme for the automatic generation control coordination. • A novel multi-agent learning algorithm is developed to resolve stochastic control problems in power systems. • A variable learning rate are introduced base on the framework of stochastic games. • A simulation platform is developed to test the performance of different algorithms. - Abstract: This paper proposes a multi-agent smart generation control scheme for the automatic generation control coordination in interconnected complex power systems. A novel multi-agent decentralized win or learn fast policy hill-climbing with eligibility trace algorithm is developed, which can effectively identify the optimal average policies via a variable learning rate under various operation conditions. Based on control performance standards, the proposed approach is implemented in a flexible multi-agent stochastic dynamic game-based smart generation control simulation platform. Based on the mixed strategy and average policy, it is highly adaptive in stochastic non-Markov environments and large time-delay systems, which can fulfill automatic generation control coordination in interconnected complex power systems in the presence of increasing penetration of decentralized renewable energy. Two case studies on both a two-area load–frequency control power system and the China Southern Power Grid model have been done. Simulation results verify that multi-agent smart generation control scheme based on the proposed approach can obtain optimal average policies thus improve the closed-loop system performances, and can achieve a fast convergence rate with significant robustness compared with other methods
International Nuclear Information System (INIS)
Braun, P.; Ruether, R.
2010-01-01
For large commercial buildings, power load delivery limits are contracted with the local electricity distribution utility, and are usually fixed at one or more levels over the year, according to the seasonal building loads, and depending on the specific country regulations. Especially in warm and sunny climates, solar electricity generation using building-integrated photovoltaics (BIPV) can assist in reducing commercial building loads, offering peak-shaving (power) benefits on top of the on-site generation of electricity (energy). This on-site power delivery capability gives these consumers the possibility of renegotiating demand contracts with their distribution utility. Commercial buildings that operate during daytime quite often have an energy consumption profile that is well matched by solar radiation availability, and depending on the building's available surface areas, BIPV can generate considerable portions of the energy requirements. In this work we present the role of grid-connected BIPV in reducing the load demands of a large and urban commercial building located in a warm climate in Brazil. The building and adjacent car parking lots can accommodate a 1 MWp BIPV generator, which closely matches the building's typical maximum power demands. Based on real solar radiation data and simultaneous building electricity demands for the year 2007, simulation of the annual solar generation profile of this on-site generator showed that the 1 MWp BIPV system could account for around 30% of the total building's energy consumption. In addition to the energy benefit, maximum power demands were reduced due to a good match between midday air-conditioning cooling loads and solar radiation availability on both a daily and seasonal basis. Furthermore, we have simulated the effect of this considerably large urban-sited generator on the local distribution network load, and have shown that the 1 MWp BIPV installation can also offer considerable benefits to the local utility in
Energy Technology Data Exchange (ETDEWEB)
Koralewicz, Przemyslaw J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Gevorgian, Vahan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Wallen, Robert B [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-07-26
Power-hardware-in-the-loop (PHIL) is a simulation tool that can support electrical systems engineers in the development and experimental validation of novel, advanced control schemes that ensure the robustness and resiliency of electrical grids that have high penetrations of low-inertia variable renewable resources. With PHIL, the impact of the device under test on a generation or distribution system can be analyzed using a real-time simulator (RTS). PHIL allows for the interconnection of the RTS with a 7 megavolt ampere (MVA) power amplifier to test multi-megawatt renewable assets available at the National Wind Technology Center (NWTC). This paper addresses issues related to the development of a PHIL interface that allows testing hardware devices at actual scale. In particular, the novel PHIL interface algorithm and high-speed digital interface, which minimize the critical loop delay, are discussed.
Convex bodies with many elliptic sections
Arelio, Isaac; Montejano, Luis
2014-01-01
{We show in this paper that two normal elliptic sections through every point of the boundary of a smooth convex body essentially characterize an ellipsoid and furthermore, that four different pairwise non-tangent elliptic sections through every point of the $C^2$-differentiable boundary of a convex body also essentially characterize an ellipsoid.
Kinematically Decoupled Cores in Dwarf (Elliptical) Galaxies
Toloba, E.; Peletier, R. F.; Guhathakurta, P.; van de Ven, G.; Boissier, S.; Boselli, A.; Brok, M. d.; Falcón-Barroso, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Lisker, T.; Paudel, S.; Ryś, A.; Salo, H.
An overview is given of what we know about the frequency of kinematically decoupled cores in dwarf elliptical galaxies. New observations show that kinematically decoupled cores happen just as often in dwarf elliptical as in ordinary early-type galaxies. This has important consequences for the
Drinfeld currents of dynamical elliptic algebra
International Nuclear Information System (INIS)
Hou Boyu; Fan Heng; Yang Wenli; Cao Junpeng
2000-01-01
From the generalized Yang-Baxter relations RLL=LLR*, where R and R* are the dynamical R-matrix of A n-1 (1) type face model with the elliptic module shifted by the center of the algebra, using the Ding-Frenkel correspondence, the authors obtain the Drinfeld currents of dynamical elliptic algebra
International Nuclear Information System (INIS)
Lo Cascio, Ermanno; Borelli, Davide; Devia, Francesco; Schenone, Corrado
2017-01-01
Highlights: • Multi-objective optimization model for retrofitted and integrated natural gas pressure regulation stations. • Comparison of different incentive mechanisms for recovered energy based on the characteristics of preheating process. • Control strategies comparison: performances achieved with optimal control vs. ones obtained by thermal load tracking. - Abstract: A multi-objective optimization model for urban integrated electrical, thermal and gas grids is presented. The main system consists of a retrofitted natural gas pressure regulation station where a turbo-expander allows to recover energy from the process. Here, the natural gas must be preheated in order to avoid methane hydrates. The preheating phase could be based on fossil fuels, renewable or on a thermal mix. Depending on the system configuration, the proposed optimization model enables a proper differentiation based on how the natural gas preheating process is expected to be accomplished. This differentiation is addressed by weighting the electricity produced by the turbo-expander and linking it to proper remuneration tariffs. The effectiveness of the model has been tested on an existing plant located in the city of Genoa. Here, the thermal energy is provided by means of two redundant gas-fired boilers and a cogeneration unit. Furthermore, the whole system is thermally integrated with a district heating network. Numerical simulation results, obtained with the commercial proprietary software Honeywell UniSim Design Suite, have been compared with the optimal solutions achieved. The effectiveness of the model, in terms of economic and environmental performances, is finally quantified. For specific conditions, the model allows achieving an operational costs reduction of about 17% with the respect to thermal-load-tracking control logic.
Nicolas, F; Coëtmellec, S; Brunel, M; Allano, D; Lebrun, D; Janssen, A J E M
2005-11-01
The authors have studied the diffraction pattern produced by a particle field illuminated by an elliptic and astigmatic Gaussian beam. They demonstrate that the bidimensional fractional Fourier transformation is a mathematically suitable tool to analyse the diffraction pattern generated not only by a collimated plane wave [J. Opt. Soc. Am A 19, 1537 (2002)], but also by an elliptic and astigmatic Gaussian beam when two different fractional orders are considered. Simulations and experimental results are presented.
The Ising model: from elliptic curves to modular forms and Calabi-Yau equations
International Nuclear Information System (INIS)
Bostan, A; Boukraa, S; Hassani, S; Zenine, N; Van Hoeij, M; Maillard, J-M; Weil, J-A
2011-01-01
We show that almost all the linear differential operators factors obtained in the analysis of the n-particle contributions of the susceptibility of the Ising model for n ≤ 6 are linear differential operators associated with elliptic curves. Beyond the simplest differential operators factors which are homomorphic to symmetric powers of the second order operator associated with the complete elliptic integral E, the second and third order differential operators Z 2 , F 2 , F 3 , L-tilde 3 can actually be interpreted as modular forms of the elliptic curve of the Ising model. A last order-4 globally nilpotent linear differential operator is not reducible to this elliptic curve, modular form scheme. This operator is shown to actually correspond to a natural generalization of this elliptic curve, modular form scheme, with the emergence of a Calabi-Yau equation, corresponding to a selected 4 F 3 hypergeometric function. This hypergeometric function can also be seen as a Hadamard product of the complete elliptic integral K, with a remarkably simple algebraic pull-back (square root extension), the corresponding Calabi-Yau fourth order differential operator having a symplectic differential Galois group SP(4,C). The mirror maps and higher order Schwarzian ODEs, associated with this Calabi-Yau ODE, present all the nice physical and mathematical ingredients we had with elliptic curves and modular forms, in particular an exact (isogenies) representation of the generators of the renormalization group, extending the modular group SL(2,Z) to a GL(2,Z) symmetry group.
Energy Technology Data Exchange (ETDEWEB)
Richter, Marlies
2012-06-21
In the study presented here, four different control strategies for the control of the inverter currents of a doubly-fed induction generator (DFIG) system are analysed and evaluated by means of simulation using Matlab/Simulink registered. Special attention is paid to the behaviour of the generator during asymmetrical grid voltage dips. Different control schemes are employed to reduce torque and DC-link voltage oscillations and the resulting additional loads on the system during such dips. The field-oriented control (FOC) scheme is the one usually deployed for the control of DFIGs in wind power plants and is used as the reference system within this study. The inverter currents (of the rotor-side inverter and the grid-side inverter) are regulated by proportional-integral controllers (PI) in a rotating coordinate system in which they are represented by dq-components. These components are direct quantities. A positive-negative-sequence current control (PNC) strategy is used to control the positive-sequence currents and the negative-sequence currents separately in two contra-rotating coordinate systems using PI-controllers. In contrast to the first two control strategies, frequency-selective current controllers (FSC) serve to regulate the currents in a static coordinate system. In this case the currents are represented by {alpha}{beta}-components which are alternating quantities. Combining the FSC and PNC strategies will produce frequencyselective positive-negative-sequence current controllers (FSC(PN)). These control the currents in a static coordinate system. The currents are represented by alternating {alpha}{beta}-components as in frequency-selective control but separate reference values for the negative-sequence currents are provided as in positive-negative-sequence control. Theoretical reasoning suggests and simulations prove that the three proposed alternative control strategies can improve the behaviour of DFIG-systems during slight asymmetries in the grid
DEFF Research Database (Denmark)
Raboni, Pietro; Chaudhary, Sanjay K.; Chen, Zhe
2016-01-01
functions are formulated on the basis of the integral of an error. This difference makes them suitable for the cases where the entire step-response data series are unavailable. The performances of differently tuned regulators are compared considering a test system including a 100 kW Diesel Generator Set......Effects of low reactance to resistance ratio in distribution networks are widely studied but little work dealing with the tuning of voltage and reactive power regulators of small synchronous generators has been reported. This study endeavours the design of a proportional integral controller...
The elliptic genus and Hidden symmetry
International Nuclear Information System (INIS)
Jaffe, A.
2001-01-01
We study the elliptic genus (a partition function) in certain interacting, twist quantum field theories. Without twists, these theories have N=2 supersymmetry. The twists provide a regularization, and also partially break the supersymmetry. In spite of the regularization, one can establish a homotopy of the elliptic genus in a coupling parameter. Our construction relies on a priori estimates and other methods from constructive quantum field theory; this mathematical underpinning allows us to justify evaluating the elliptic genus at one endpoint of the homotopy. We obtain a version of Witten's proposed formula for the elliptic genus in terms of classical theta functions. As a consequence, the elliptic genus has a hidden SL(2,Z) symmetry characteristic of conformal theory, even though the underlying theory is not conformal. (orig.)
Multicolor surface photometry of 17 ellipticals
International Nuclear Information System (INIS)
Franx, M.; Illingworth, G.; Heckman, T.
1989-01-01
Multicolor two-dimensional surface photometry was used to obtain radial profiles for surface brightness, color, ellipticity, position angle, and the residuals from the fitted ellipses described by the cos(n phi) and sin(n phi) terms (where n = 3 and 4) for 17 elliptical galaxies. It is found that at radii as large as five times the seeing FWHM, seeing can affect the ellipticity at the 10 percent level and introduce uncertainty in the position angles of several degrees, particularly for very round ellipticals. The present profiles are found to agree well with previous data, with rms differences of 0.02 in ellipticity and 2 deg in position angle. The observed color gradients are consistent with a decrease in the metallicity by a factor of about 2 per decade in radius. 61 refs
Elliptical excisions: variations and the eccentric parallelogram.
Goldberg, Leonard H; Alam, Murad
2004-02-01
The elliptical (fusiform) excision is a basic tool of cutaneous surgery. To assess the design, functionality, ease of construction, and aesthetic outcomes of the ellipse. A systematic review of elliptical designs and their site-specific benefits and limitations. In particular, we consider the (1). context of prevailing relaxed skin tension lines and tissue laxity; and (2). removal of the smallest possible amount of tissue around the lesion and in the "dog-ears." Attention is focused on intuitive methods that can be reproducibly planned and executed. Elliptical variations are easily designed and can be adapted to many situations. The eccentric parallelogram excision is offered as a new technique that minimizes notching and focal tension in the center of an elliptical closure. Conclusion The elliptical (fusiform) excision is an efficient, elegant, and versatile technique that will remain a mainstay of the cutaneous surgical armamentarium.
Technology Roadmaps: Smart Grids
Energy Technology Data Exchange (ETDEWEB)
NONE
2011-07-01
The development of Technology Roadmaps: Smart Grids -- which the IEA defines as an electricity network that uses digital and other advanced technologies to monitor and manage the transport of electricity from all generation sources to meet the varying electricity demands of end users -- is essential if the global community is to achieve shared goals for energy security, economic development and climate change mitigation. Unfortunately, existing misunderstandings of exactly what smart grids are and the physical and institutional complexity of electricity systems make it difficult to implement smart grids on the scale that is needed. This roadmap sets out specific steps needed over the coming years to achieve milestones that will allow smart grids to deliver a clean energy future.
40 CFR 761.308 - Sample selection by random number generation on any two-dimensional square grid.
2010-07-01
... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Sample selection by random number... Â§ 761.79(b)(3) § 761.308 Sample selection by random number generation on any two-dimensional square... area created in accordance with paragraph (a) of this section, select two random numbers: one each for...
Directory of Open Access Journals (Sweden)
Saule Baurzhan
2017-03-01
Full Text Available Many power utilities in sub-Saharan Africa (SSA have inadequate generation capacity, unreliable services, and high costs. They also face capital constraints that restrict them from making the investments necessary for capacity expansion. Capacity shortages have compelled power utilities to use leased emergency power-generating units, mainly oil-fired diesel generators, as a short-term solution. An economic analysis is carried out to compare the economic net present value (ENPV of fuel savings, as well as the greenhouse gas (GHG savings, from investing capital in a solar PV power-generation plant with those from investing the same amount of funds into a diesel power plant. The results show that ENPV is negative for the solar PV plant, whereas it has a large positive value for the diesel plant. In addition, the diesel plant would be almost three times as effective in reducing GHG emissions as the same value of investment in the solar PV plant. Even with solar investment costs falling, it will take 12 to 24 years of continuous decline before solar PV becomes cost-effective for SSA. The capital cost of solar PV would need to drop to US$1058.4 per kW to yield the same level of ENPV as the diesel plant.
Domain decomposition multigrid for unstructured grids
Energy Technology Data Exchange (ETDEWEB)
Shapira, Yair
1997-01-01
A two-level preconditioning method for the solution of elliptic boundary value problems using finite element schemes on possibly unstructured meshes is introduced. It is based on a domain decomposition and a Galerkin scheme for the coarse level vertex unknowns. For both the implementation and the analysis, it is not required that the curves of discontinuity in the coefficients of the PDE match the interfaces between subdomains. Generalizations to nonmatching or overlapping grids are made.
International Nuclear Information System (INIS)
Kamel, Rashad M.
2013-01-01
Highlights: • This paper presented two fault ride through techniques for fixed speed wind systems. • The first technique is implemented by inserting a series resistance with the terminals of wind generator. • Second technique is performed by adapting the gear ratio to spill some mechanical power. - Abstract: This study presents two different Fault Ride Through (FRT) techniques to keep and restore stability of Fixed Speed Wind Generation system (FSWGs) installed in standalone Micro-Grid (MG). The first technique is an electrical FRT and is implemented by inserting a series resistance with the terminals of FSWGs during fault to maintain reasonable value of terminal voltage and consequently help stability restoration. The second controller is a mechanical FRT controller and is performed by change the gear ratio of wind generation systems to spill part of extracted mechanical power and consequently improving stability issue. Obtained results proved that each controller able to maintain the stability of FSWGs under the most severe disturbance conditions (400 ms three phase fault at FSWGs terminals). The first controller is faster than the second controller in restoring FSWGs stability. Superior results and performances are obtained when the two FRT techniques are employed simultaneously. Without employing any one of the two FRT techniques, FSWGs is not able to maintain or restore its stability after fault clearing. Consequently, MG will lose one of its micro-sources and cannot keep its stability during the standalone mode, unless load shedding strategy is activated. The two proposed controllers are simple, effective, and economical attractive
Energy Technology Data Exchange (ETDEWEB)
Drif, M. [Grupo de Investigacion IDEA, Departamento de Electronica, Escuela Politecnica Superior, Universidad de Jaen, Campus Las Lagunillas, 23071 Jaen (Spain); Centre de Developpement des Energies Renouvelables, BP 62, Route de l' Observatoire, 16340 Bouzareah, Algiers (Algeria); Perez, P.J.; Aguilera, J.; Aguilar, J.D. [Grupo de Investigacion IDEA, Departamento de Electronica, Escuela Politecnica Superior, Universidad de Jaen, Campus Las Lagunillas, 23071 Jaen (Spain)
2008-09-15
A new method for estimating the irradiance on a partially shaded photovoltaic generator system is proposed. The basic principle of this method consists of two parts: firstly, an approximation of the obstacles' outline or the local horizon by a set of linear functions. Here, a survey of the surroundings is based on the reading of the topographic coordinates of the only significant points of all the objects surrounding the photovoltaic generator. Secondly, the irradiance on the photovoltaic plane is estimated using an accurate model such as the Perez et al. model and assuming that the shading affects both the direct radiation and a part of the diffuse component (circumsolar component). The aim of this paper is to present the principles of the proposed method and the algorithm used for calculating the irradiance on shaded planes. In addition, the results of the comparison between the simulated and measured values of this method are presented. (author)
Syverud, Tron Hansen
2016-01-01
Hybrid electric power systems (HPS) have successfully been integrated in the road-traffic industry due to enhanced efficiency and environmental benefits. Recently this concept has been implemented in the marine sector. In this master thesis, the construction of a DC hybrid power system for a marine vessel is outlined in detail. The HPS is developed in Matlbat/Simulink and comprises two set of diesel generators with variable speed, six-pulse diode bridges, a battery bank, bidire...
Sharmin Sobhan; Tanvir Ahmad; Md. Jakaria Rahimi; Md. Habib Ullah; Shaila Arif
2016-01-01
Lack of access to electricity is one of the major impediments to the economic growth and development for any developing country. As well as limited reserve of conventional fuel and geo-location of Bangladesh arise the demand to find an effective alternative energy source for rural electrification. This document approaches a poultry-home based power generation model for rural Bangladesh and diagnosis its feasibility through HOMER, a micro power modelling and optimization software. The introduc...
CERN. Geneva
2004-01-01
The aim of Grid computing is to enable the easy and open sharing of resources between large and highly distributed communities of scientists and institutes across many independent administrative domains. Convincing site security officers and computer centre managers to allow this to happen in view of today's ever-increasing Internet security problems is a major challenge. Convincing users and application developers to take security seriously is equally difficult. This paper will describe the main Grid security issues, both in terms of technology and policy, that have been tackled over recent years in LCG and related Grid projects. Achievements to date will be described and opportunities for future improvements will be addressed.
Energy Technology Data Exchange (ETDEWEB)
NONE
1999-03-01
This survey includes the characteristics of small-scale power grids, feasibility studies on introduction of wind turbines in these grids, and statuses of application of wind turbines to isolated islands or the like in the advanced countries, in order to promote introduction of wind power generation systems in isolated islands or the like. It is concluded that small-capacity wind power generation systems can be possibly introduced in the intermediate- to large-scale grids in isolated islands, 1,500kW or larger in capacity, in the Tokyo, Kyushu and Okinawa Electric Power Companies' areas. A scheduled steamer ship for isolated islands can carry up to 10 ton track, and introduction of a small-scale wind turbine is more advantageous viewed from the transportation cost. Some foreign countries have the sites which have achieved a high percentage of grid connection of wind power units by stabilizing wind conditions and connecting them to the main high-voltage grids in different manners from those adopted in Japan. For developing wind turbine bodies, most of the foreign countries surveyed are concentrating their efforts on development and manufacture of large-size units, paying little attention on development of small-size wind turbines for isolated islands. For the future prospects, the promising concepts include adoption of wind turbines small in capacity and easy to transport and assemble, and hybrid systems combined with power storage units. (NEDO)
Energy Technology Data Exchange (ETDEWEB)
NONE
1999-03-01
This survey includes the characteristics of small-scale power grids, feasibility studies on introduction of wind turbines in these grids, and statuses of application of wind turbines to isolated islands or the like in the advanced countries, in order to promote introduction of wind power generation systems in isolated islands or the like. It is concluded that small-capacity wind power generation systems can be possibly introduced in the intermediate- to large-scale grids in isolated islands, 1,500kW or larger in capacity, in the Tokyo, Kyushu and Okinawa Electric Power Companies' areas. A scheduled steamer ship for isolated islands can carry up to 10 ton track, and introduction of a small-scale wind turbine is more advantageous viewed from the transportation cost. Some foreign countries have the sites which have achieved a high percentage of grid connection of wind power units by stabilizing wind conditions and connecting them to the main high-voltage grids in different manners from those adopted in Japan. For developing wind turbine bodies, most of the foreign countries surveyed are concentrating their efforts on development and manufacture of large-size units, paying little attention on development of small-size wind turbines for isolated islands. For the future prospects, the promising concepts include adoption of wind turbines small in capacity and easy to transport and assemble, and hybrid systems combined with power storage units. (NEDO)
Energy Technology Data Exchange (ETDEWEB)
Hoeckel, M.; Luechinger, P.
2003-07-01
This is the seventh part of a ten-part final report for the Swiss Federal Office of Energy (SFOE) on a project that looked into potential problems relating to the Swiss electricity distribution grid with respect to the increasing number of distributed power generation facilities being put into service. The identification of special conditions for the grid's operation and future development that take increasing decentralised power production into account are discussed. The results of the project activities encompass the analysis and evaluation of various problem areas associated with planning and management of the grid during normal operation and periods of malfunction, as well as required modifications to safety systems and grid configurations. This sixth appendix to the main report presents and discusses the results of simulations made on the basis of the real-life 16 kV medium-voltage distribution network operated by the Aargovian electricity utility AEW. This appendix describes the simulation methods used and the basic characteristics of medium-voltage networks and distributed generation facilities. Different types of load profiles, including domestic and industrial loads, are discussed. The results of the simulations are presented in graphical form and provide profiles of voltage and current, active and reactive power and further mains characteristics for varying load conditions. Also, daily profiles for situations with and without distributed generation are presented and short-circuit simulations and grid dynamics are discussed.
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-09-01
In relation to the demonstrative study of the photovoltaic power system that is planned in Libong island, Thailand, the FY 2000 results were reported. In this R and D, construction/demonstrative operation were planned for a photovoltaic power station with a generation output of 100kW, photovoltaic power system in school facilities, and system for transmitting/distributing power to houses by connecting the power station and power system. In this fiscal year, the field survey was conducted together with the alteration from Yao Yai island, for which the demonstrative study was planned at first, to Libong island. The electric equipment was selected which met the requests from Thailand and the results of the field survey, and the basic design of the photovoltaic power generation/transmission/distribution system was completed. Based on this, the design/manufacture of photovoltaic power generation modules, power control equipment, measuring equipment, etc. were made. At the construction site of photovoltaic power station, construction work such as land formation was conducted. Further, Thai engineers who visited Japan did the following: discussions about power system, presence at test/inspection of photovoltaic power generation modules, visits to photovoltaic power stations, wind power stations, etc. (NEDO)
Modeling groundwater flow to elliptical lakes and through multi-aquifer elliptical inhomogeneities
Bakker, Mark
2004-05-01
Two new analytic element solutions are presented for steady flow problems with elliptical boundaries. The first solution concerns groundwater flow to shallow elliptical lakes with leaky lake beds in a single-aquifer. The second solution concerns groundwater flow through elliptical cylinder inhomogeneities in a multi-aquifer system. Both the transmissivity of each aquifer and the resistance of each leaky layer may differ between the inside and the outside of an inhomogeneity. The elliptical inhomogeneity may be bounded on top by a shallow elliptical lake with a leaky lake bed. Analytic element solutions are obtained for both problems through separation of variables of the Laplace and modified-Helmholtz differential equations in elliptical coordinates. The resulting equations for the discharge potential consist of infinite sums of products of exponentials, trigonometric functions, and modified-Mathieu functions. The series are truncated but still fulfill the differential equation exactly; boundary conditions are met approximately, but up to machine accuracy provided enough terms are used. The head and flow may be computed analytically at any point in the aquifer. Examples are given of uniform flow through an elliptical lake, a well pumping near two elliptical lakes, and uniform flow through three elliptical inhomogeneities in a multi-aquifer system. Mathieu functions may be applied in a similar fashion to solve other groundwater flow problems in semi-confined aquifers and leaky aquifer systems with elliptical internal or external boundaries.
Wireless OAM transmission system based on elliptical microstrip patch antenna.
Chen, Jia Jia; Lu, Qian Nan; Dong, Fei Fei; Yang, Jing Jing; Huang, Ming
2016-05-30
The multiplexing transmission has always been a focus of attention for communication technology. In this paper, the radiation characteristics of circular microstrip patch antenna was firstly analyzed based on cavity model theory, and then spiral beams carrying orbital angular momentum (OAM) were generated, using elliptical microstrip patch antenna, with a single feed probe instead of a standard circular patch with two feedpoints. Moreover, by combining the proposed elliptic microstrip patch antenna with Universal Software Radio Peripheral (USRP), a wireless OAM transmission system was established and the real-time transmission of text, image and video in a real channel environment was realized. Since the wireless OAM transmission has the advantage of good safety and high spectrum utilization efficiency, this work has theoretical significance and potential application.
Electric sail elliptic displaced orbits with advanced thrust model
Niccolai, Lorenzo; Quarta, Alessandro A.; Mengali, Giovanni
2017-09-01
This paper analyzes the performance of an Electric Solar Wind Sail for generating and maintaining an elliptic, heliocentric, displaced non-Keplerian orbit. In this sense, this paper extends and completes recent studies regarding the performances of an Electric Solar Wind Sail that covers a circular, heliocentric, displaced orbit of given characteristics. The paper presents the general equations that describe the elliptic orbit maintenance in terms of both spacecraft attitude and performance requirements, when a refined thrust model (recently proposed for the preliminary mission design) is taken into account. In particular, the paper also discusses some practical applications on particular mission scenarios in which an analytic solution of the governing equations has been found.
Excursion Processes Associated with Elliptic Combinatorics
Baba, Hiroya; Katori, Makoto
2018-06-01
Researching elliptic analogues for equalities and formulas is a new trend in enumerative combinatorics which has followed the previous trend of studying q-analogues. Recently Schlosser proposed a lattice path model in the square lattice with a family of totally elliptic weight-functions including several complex parameters and discussed an elliptic extension of the binomial theorem. In the present paper, we introduce a family of discrete-time excursion processes on Z starting from the origin and returning to the origin in a given time duration 2 T associated with Schlosser's elliptic combinatorics. The processes are inhomogeneous both in space and time and hence expected to provide new models in non-equilibrium statistical mechanics. By numerical calculation we show that the maximum likelihood trajectories on the spatio-temporal plane of the elliptic excursion processes and of their reduced trigonometric versions are not straight lines in general but are nontrivially curved depending on parameters. We analyze asymptotic probability laws in the long-term limit T → ∞ for a simplified trigonometric version of excursion process. Emergence of nontrivial curves of trajectories in a large scale of space and time from the elementary elliptic weight-functions exhibits a new aspect of elliptic combinatorics.
Smart Grid Integration Laboratory
Energy Technology Data Exchange (ETDEWEB)
Troxell, Wade [Colorado State Univ., Fort Collins, CO (United States)
2011-12-22
The initial federal funding for the Colorado State University Smart Grid Integration Laboratory is through a Congressionally Directed Project (CDP), DE-OE0000070 Smart Grid Integration Laboratory. The original program requested in three one-year increments for staff acquisition, curriculum development, and instrumentation all which will benefit the Laboratory. This report focuses on the initial phase of staff acquisition which was directed and administered by DOE NETL/ West Virginia under Project Officer Tom George. Using this CDP funding, we have developed the leadership and intellectual capacity for the SGIC. This was accomplished by investing (hiring) a core team of Smart Grid Systems engineering faculty focused on education, research, and innovation of a secure and smart grid infrastructure. The Smart Grid Integration Laboratory will be housed with the separately funded Integrid Laboratory as part of CSU's overall Smart Grid Integration Center (SGIC). The period of performance of this grant was 10/1/2009 to 9/30/2011 which included one no cost extension due to time delays in faculty hiring. The Smart Grid Integration Laboratory's focus is to build foundations to help graduate and undergraduates acquire systems engineering knowledge; conduct innovative research; and team externally with grid smart organizations. Using the results of the separately funded Smart Grid Workforce Education Workshop (May 2009) sponsored by the City of Fort Collins, Northern Colorado Clean Energy Cluster, Colorado State University Continuing Education, Spirae, and Siemens has been used to guide the hiring of faculty, program curriculum and education plan. This project develops faculty leaders with the intellectual capacity to inspire its students to become leaders that substantially contribute to the development and maintenance of Smart Grid infrastructure through topics such as: (1) Distributed energy systems modeling and control; (2) Energy and power conversion; (3
Indian Academy of Sciences (India)
A computing grid interconnects resources such as high performancecomputers, scientific databases, and computercontrolledscientific instruments of cooperating organizationseach of which is autonomous. It precedes and is quitedifferent from cloud computing, which provides computingresources by vendors to customers ...
Indian Academy of Sciences (India)
IAS Admin
emergence of supercomputers led to the use of computer simula- tion as an .... Scientific and engineering applications (e.g., Tera grid secure gate way). Collaborative ... Encryption, privacy, protection from malicious software. Physical Layer.
Micro Grid: A Smart Technology
Naveenkumar, M; Ratnakar, N
2012-01-01
Distributed Generation (DG) is an approach that employs small-scale technologies to produce electricity close to the end users of power. Todays DG technologies often consist of renewable generators, and offer a number of potential benefits. This paper presents a design of micro grid as part of Smart grid technologies with renewable energy resources like solar, wind and Diesel generator. The design of the microgrid with integration of Renewable energy sources are done in PSCAD/EMTDC.This paper...
Elliptic hypergeometric functions and the representation theory
International Nuclear Information System (INIS)
Spiridonov, V.P.
2011-01-01
Full text: (author)Elliptic hypergeometric functions were discovered around ten years ago. They represent the top level known generalization of the Euler beta integral and Euler-Gauss 2 F 1 hypergeometric function. In general form they are defined by contour integrals involving elliptic gamma functions. We outline the structure of the simplest examples of such functions and discuss their relations to the representation theory of the classical Lie groups and their various deformations. In one of the constructions elliptic hypergeometric integrals describe purely group-theoretical objects having the physical meaning of superconformal indices of four-dimensional supersymmetric gauge field theories
International Workshop on Elliptic and Parabolic Equations
Schrohe, Elmar; Seiler, Jörg; Walker, Christoph
2015-01-01
This volume covers the latest research on elliptic and parabolic equations and originates from the international Workshop on Elliptic and Parabolic Equations, held September 10-12, 2013 at the Leibniz Universität Hannover. It represents a collection of refereed research papers and survey articles written by eminent scientist on advances in different fields of elliptic and parabolic partial differential equations, including singular Riemannian manifolds, spectral analysis on manifolds, nonlinear dispersive equations, Brownian motion and kernel estimates, Euler equations, porous medium type equations, pseudodifferential calculus, free boundary problems, and bifurcation analysis.
Equivalent Simplification Method of Micro-Grid
Cai Changchun; Cao Xiangqin
2013-01-01
The paper concentrates on the equivalent simplification method for the micro-grid system connection into distributed network. The equivalent simplification method proposed for interaction study between micro-grid and distributed network. Micro-grid network, composite load, gas turbine synchronous generation, wind generation are equivalent simplification and parallel connect into the point of common coupling. A micro-grid system is built and three phase and single phase grounded faults are per...
Directory of Open Access Journals (Sweden)
Gabriella Ferruzzi
2013-02-01
Full Text Available A new short-term probabilistic forecasting method is proposed to predict the probability density function of the hourly active power generated by a photovoltaic system. Firstly, the probability density function of the hourly clearness index is forecasted making use of a Bayesian auto regressive time series model; the model takes into account the dependence of the solar radiation on some meteorological variables, such as the cloud cover and humidity. Then, a Monte Carlo simulation procedure is used to evaluate the predictive probability density function of the hourly active power by applying the photovoltaic system model to the random sampling of the clearness index distribution. A numerical application demonstrates the effectiveness and advantages of the proposed forecasting method.
Generalized multiscale finite element methods. nonlinear elliptic equations
Efendiev, Yalchin R.; Galvis, Juan; Li, Guanglian; Presho, Michael
2013-01-01
In this paper we use the Generalized Multiscale Finite Element Method (GMsFEM) framework, introduced in [26], in order to solve nonlinear elliptic equations with high-contrast coefficients. The proposed solution method involves linearizing the equation so that coarse-grid quantities of previous solution iterates can be regarded as auxiliary parameters within the problem formulation. With this convention, we systematically construct respective coarse solution spaces that lend themselves to either continuous Galerkin (CG) or discontinuous Galerkin (DG) global formulations. Here, we use Symmetric Interior Penalty Discontinuous Galerkin approach. Both methods yield a predictable error decline that depends on the respective coarse space dimension, and we illustrate the effectiveness of the CG and DG formulations by offering a variety of numerical examples. © 2014 Global-Science Press.
Controlling smart grid adaptivity
Toersche, Hermen; Nykamp, Stefan; Molderink, Albert; Hurink, Johann L.; Smit, Gerardus Johannes Maria
2012-01-01
Methods are discussed for planning oriented smart grid control to cope with scenarios with limited predictability, supporting an increasing penetration of stochastic renewable resources. The performance of these methods is evaluated with simulations using measured wind generation and consumption data. Forecast errors are shown to affect worst case behavior in particular, the severity of which depends on the chosen adaptivity strategy and error model.
Partial differential operators of elliptic type
Shimakura, Norio
1992-01-01
This book, which originally appeared in Japanese, was written for use in an undergraduate course or first year graduate course in partial differential equations and is likely to be of interest to researchers as well. This book presents a comprehensive study of the theory of elliptic partial differential operators. Beginning with the definitions of ellipticity for higher order operators, Shimakura discusses the Laplacian in Euclidean spaces, elementary solutions, smoothness of solutions, Vishik-Sobolev problems, the Schauder theory, and degenerate elliptic operators. The appendix covers such preliminaries as ordinary differential equations, Sobolev spaces, and maximum principles. Because elliptic operators arise in many areas, readers will appreciate this book for the way it brings together a variety of techniques that have arisen in different branches of mathematics.
On mod 2 and higher elliptic genera
International Nuclear Information System (INIS)
Liu Kefeng
1992-01-01
In the first part of this paper, we construct mod 2 elliptic genera on manifolds of dimensions 8k+1, 8k+2 by mod 2 index formulas of Dirac operators. They are given by mod 2 modular forms or mod 2 automorphic functions. We also obtain an integral formula for the mod 2 index of the Dirac operator. As a by-product we find topological obstructions to group actions. In the second part, we construct higher elliptic genera and prove some of their rigidity properties under group actions. In the third part we write down characteristic series for all Witten genera by Jacobi theta-functions. The modular property and transformation formulas of elliptic genera then follow easily. We shall also prove that Krichever's genera, which come from integrable systems, can be written as indices of twisted Dirac operators for SU-manifolds. Some general discussions about elliptic genera are given. (orig.)
Smart grids - French Expertise
International Nuclear Information System (INIS)
2015-11-01
The adaptation of electrical systems is the focus of major work worldwide. Bringing electricity to new territories, modernizing existing electricity grids, implementing energy efficiency policies and deploying renewable energies, developing new uses for electricity, introducing electric vehicles - these are the challenges facing a multitude of regions and countries. Smart Grids are the result of the convergence of electrical systems technologies with information and communications technologies. They play a key role in addressing the above challenges. Smart Grid development is a major priority for both public and private-sector actors in France. The experience of French companies has grown with the current French electricity system, a system that already shows extensive levels of 'intelligence', efficiency and competitiveness. French expertise also leverages substantial competence in terms of 'systems engineering', and can provide a tailored response to meet all sorts of needs. French products and services span all the technical and commercial building blocks that make up the Smart Grid value chain. They address the following issues: Improving the use and valuation of renewable energies and decentralized means of production, by optimizing the balance between generation and consumption. Strengthening the intelligence of the transmission and distribution grids: developing 'Supergrid', digitizing substations in transmission networks, and automating the distribution grids are the focus of a great many projects designed to reinforce the 'self-healing' capacity of the grid. Improving the valuation of decentralized flexibilities: this involves, among others, deploying smart meters, reinforcing active energy efficiency measures, and boosting consumers' contribution to grid balancing, via practices such as demand response which implies the aggregation of flexibility among residential, business, and/or industrial sites. Addressing current technological challenges, in
Constructing elliptic curves from Galois representations
Snowden, Andrew; Tsimerman, Jacob
2017-01-01
Given a non-isotrivial elliptic curve over an arithmetic surface, one obtains a lisse $\\ell$-adic sheaf of rank two over the surface. This lisse sheaf has a number of straightforward properties: cyclotomic determinant, finite ramification, rational traces of Frobenius, and somewhere not potentially good reduction. We prove that any lisse sheaf of rank two possessing these properties comes from an elliptic curve.
Elliptic and parabolic equations for measures
Energy Technology Data Exchange (ETDEWEB)
Bogachev, Vladimir I [M. V. Lomonosov Moscow State University, Moscow (Russian Federation); Krylov, Nikolai V [University of Minnesota, Minneapolis, MN (United States); Roeckner, Michael [Universitat Bielefeld, Bielefeld (Germany)
2009-12-31
This article gives a detailed account of recent investigations of weak elliptic and parabolic equations for measures with unbounded and possibly singular coefficients. The existence and differentiability of densities are studied, and lower and upper bounds for them are discussed. Semigroups associated with second-order elliptic operators acting in L{sup p}-spaces with respect to infinitesimally invariant measures are investigated. Bibliography: 181 titles.
Recent trends in grid computing
International Nuclear Information System (INIS)
Miura, Kenichi
2004-01-01
Grid computing is a technology which allows uniform and transparent access to geographically dispersed computational resources, such as computers, databases, experimental and observational equipment etc. via high-speed, high-bandwidth networking. The commonly used analogy is that of electrical power grid, whereby the household electricity is made available from outlets on the wall, and little thought need to be given to where the electricity is generated and how it is transmitted. The usage of grid also includes distributed parallel computing, high through-put computing, data intensive computing (data grid) and collaborative computing. This paper reviews the historical background, software structure, current status and on-going grid projects, including applications of grid technology to nuclear fusion research. (author)
International Nuclear Information System (INIS)
Janchevska, Melita
2012-01-01
The master thesis “Spatial mapping of wind parks in Republic of Macedonia from aspect of power generation and connection to power grid” presents spatial aspects for setting of wind parks at favourable locations. The thesis presents a comprehensive analysis how to carry out the administrative procedures that are in force in Republic of Macedonia, a range of minimum allowed distances in setting of each of the wind plants within a wind parks, but also requirements for fulfilling the basic human rights in preserving quality of life of the people in rural areas where the wind parks are build. As a result, a compromise in setting of wind parks and a suitable solution of sustainable development should be reached. Therefore, the decision making process should be based on the following key factors: environmental, social and economic development of the area of concern. The production of wind power is strongly influenced by meteorological conditions and has an average factor of utilization of up to 30%. This low factor of utilization cannot be used for planning of the basic energy needs of the country, but it can contribute certainly towards the reduction of the participation of conventional power plants. Republic of Macedonia introduced feed-in tariffs as a subsiding mechanism for building and strong penetration of wind parks. Additional funding mechanisms include carbon financing and green-field credits, through development of projects in the framework of Clean Development Mechanism, which improves the economic feasibility of the project and increases the interest of the investors. The analysis of the relevant spatial aspects of setting wind parks in Republic of Macedonia based on balanced and sustainable spatial development is made with regards to the following thematic areas: exploiting the potential of wind energy, climate issues, geo morphological and geo seismically aspects, rational use of land, protection of agricultural land and forests, spatial allocation of
Application of synchronous grid-connected controller in the wind-solar-storage micro grid
Li, Hua; Ren, Yongfeng; Li, Le; Luo, Zhenpeng
2016-01-01
Recently, there has been an increasing interest in using distributed generators (DG) not only to inject power into the grid, but also to enhance the power quality. In this study, a space voltage pulse width modulation (SVPWM) control method is proposed for a synchronous grid-connected controller in a wind-solar-storage micro grid. This method is based on the appropriate topology of the synchronous controller. The wind-solar-storage micro grid is controlled to reconnect to the grid synchronous...
International Nuclear Information System (INIS)
Anderson, Dennis; Leach, Matthew
2004-01-01
If intermittent renewable energy technologies such as those based on solar, wind, wave and tidal resources are eventually to supply significant shares of total energy supplies, it is crucial that the energy storage problem is solved. There are several (long-recognised) possibilities ahead including compressed air, pumped storage, further developments in batteries, regenerable fuel cells, 'super-capacitors' and so forth. But one that is being revisited extensively by industry and research establishments is the production and storage of hydrogen from electricity at off-peak times, and in times when there would be a surplus of renewable energy, for reuse in the electricity, gas and transport markets; short-term and even seasonal and longer-term storage is technically feasible with this option. This paper looks at the costs of the option both in the near-term and the long-term relative to the current costs of electricity and natural gas supplies. While the costs of hydrogen would necessarily be greater than those of natural gas (though not disruptively so), when used in conjunction with emerging technologies for decentralised generation and combined heat and power there is scope for appreciable economies in electricity supply. A lot will depend on innovation at the systems level, and on how we operate our electricity and gas grids and regulate our electricity and gas industries. We have also suggested that we now need to experiment more, at the commercial level, and in the laboratories, with the hydrogen option
Directory of Open Access Journals (Sweden)
Rameez Asif
2014-01-01
Full Text Available We have analyzed the impact of digital and optical signal processing algorithms, that is, Volterra equalization (VE, digital backpropagation (BP, and optical phase conjugation with nonlinearity module (OPC-NM, in next generation 10 Gbit/s (also referred to as XG DP-QPSK long haul WDM (fixed-grid passive optical network (PON without midspan repeaters over 120 km standard single mode fiber (SMF link for downstream signals. Due to the compensation of optical Kerr effects, the sensitivity penalty is improved by 2 dB by implementing BP algorithm, 1.5 dB by VE algorithm, and 2.69 dB by OPC-NM. Moreover, with the implementation of NL equalization technique, we are able to get the transmission distance of 126.6 km SMF for the 1 : 1024 split ratio at 5 GHz channel spacing in the nonlinear region.
Effects of elliptical burner geometry on partially premixed gas jet flames in quiescent surroundings
Baird, Benjamin
to two reasons. The elliptical burners have enhanced turbulence generation that lowers their stability when compared to the circular burner. The 4:1 AR elliptical burner had greater stability due to a greater velocity decay rate and wider OH reaction zones particularly in the region between the two jets. The 3:1 AR elliptical and circular burners produced similar carbon monoxide and nitric oxide emission indexes over the range of equivalence ratios of 0.55 to 4.0, for laminar flames. (Abstract shortened by UMI.)
Directory of Open Access Journals (Sweden)
Dominik Falkowski
2013-03-01
Full Text Available The article summarizes a research project which was conducted in order to ensure what will be the influence of future investments and changes in the Polish Power System on the stability and functionality of the ENERGA SA distribution grid system. Development of the ENERGA SA distribution grid system was also included. Only stable states were tested for various cases of system load and generation in power plants (the Nuclear Power Plant in Żarnowiec was taken into account and also in wind farms. The system was also tested in N-1 and N-2 states. The result of this study is an overall evaluation of the ENERGA SA distribution grid condition, as well as the identification of potential weak points inside this structure.
Fabrication of elliptical SRF cavities
Singer, W.
2017-03-01
The technological and metallurgical requirements of material for high-gradient superconducting cavities are described. High-purity niobium, as the preferred metal for the fabrication of superconducting accelerating cavities, should meet exact specifications. The content of interstitial impurities such as oxygen, nitrogen, and carbon must be below 10 μg g-1. The hydrogen content should be kept below 2 μg g-1 to prevent degradation of the quality factor (Q-value) under certain cool-down conditions. The material should be free of flaws (foreign material inclusions or cracks and laminations) that can initiate a thermal breakdown. Traditional and alternative cavity mechanical fabrication methods are reviewed. Conventionally, niobium cavities are fabricated from sheet niobium by the formation of half-cells by deep drawing, followed by trim machining and electron beam welding. The welding of half-cells is a delicate procedure, requiring intermediate cleaning steps and a careful choice of weld parameters to achieve full penetration of the joints. A challenge for a welded construction is the tight mechanical and electrical tolerances. These can be maintained by a combination of mechanical and radio-frequency measurements on half-cells and by careful tracking of weld shrinkage. The main aspects of quality assurance and quality management are mentioned. The experiences of 800 cavities produced for the European XFEL are presented. Another cavity fabrication approach is slicing discs from the ingot and producing cavities by deep drawing and electron beam welding. Accelerating gradients at the level of 35-45 MV m-1 can be achieved by applying electrochemical polishing treatment. The single-crystal option (grain boundary free) is discussed. It seems that in this case, high performance can be achieved by a simplified treatment procedure. Fabrication of the elliptical resonators from a seamless pipe as an alternative is briefly described. This technology has yielded good
International Nuclear Information System (INIS)
Viterbo, J.
2012-01-01
The implementation of renewable energies represents new challenges for electrical systems. The objective: making power grids smarter so they can handle intermittent production. The advent of smart grids will allow flexible operations like distributing energy in a multidirectional manner instead of just one way and it will make electrical systems capable of integrating actions by different users, consumers and producers in order to maintain efficient, sustainable, economical and secure power supplies. Practically speaking, they associate sensors, instrumentation and controls with information processing and communication systems in order to create massively automated networks. Smart grids require huge investments: for example more than 7 billion dollars have been invested in China and in the Usa in 2010 and France is ranked 9. worldwide with 265 million dollars invested. It is expected that smart grids will promote the development of new business models and a change in the value chain for energy. Decentralized production combined with the probable introduction of more or less flexible rates for sales or purchases and of new supplier-customer relationships will open the way to the creation of new businesses. (A.C.)
Synchronization in single-phase grid-connected photovoltaic systems under grid faults
DEFF Research Database (Denmark)
Yang, Yongheng; Blaabjerg, Frede
2012-01-01
The highly increasing penetration of single-phase photovoltaic (PV) systems pushes the grid requirements related to the integration of PV power systems to be updated. These upcoming regulations are expected to direct the grid-connected renewable generators to support the grid operation and stabil......The highly increasing penetration of single-phase photovoltaic (PV) systems pushes the grid requirements related to the integration of PV power systems to be updated. These upcoming regulations are expected to direct the grid-connected renewable generators to support the grid operation...
Transverse magnetic scattering by parallel conducting elliptic cylinders
Sebak, A.
1991-10-01
A boundary value solution to the problem of transverse magnetic multiple scattering by M parallel perfectly conducting elliptic cylinders is presented. The solution is an exact one and based on the separation-of-variables technique and the addition theorem for Mathieu functions. It is expressed in terms of a system of simultaneous linear equations of infinite order, which is then truncated for numerical computations. Representative numerical results for the scattered field by two cylinders are then generated, for some selected sizes and orientations parameters, and presented.
Atomic processes in strong bichromatic elliptically polarized laser fields
Energy Technology Data Exchange (ETDEWEB)
Odžak, S., E-mail: senad.odzak@gmail.com; Hasović, E.; Gazibegović-Busuladžić, A.; Čerkić, A., E-mail: anercerkic@yahoo.com; Fetić, B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegovina); Kramo, A. [BHANSA, Aeronautical Meteorology Department, Kurta Schorka 36, 71000 Sarajevo (Bosnia and Herzegovina); Busuladžić, M. [Medical Faculty, University of Sarajevo, Čekaluša 90, 71000 Sarajevo (Bosnia and Herzegovina); Milošević, D. B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegovina); Academy of Sciences and Arts of Bosnia and Herzegovina, Bistrik 7, 71000 Sarajevo (Bosnia and Herzegovina); Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin (Germany)
2016-03-25
Nonlinear quantum-mechanical phenomena in strong laser fields, such as high-order harmonic generation (HHG) and above-threshold ionization (ATI) are significantly modified if the applied laser field is bichromatic and/or elliptically polarized. Numerical results obtained within the strong-field approximation are presented for two special cases. We show results for HHG by plasma ablation in a bichromatic linearly polarized laser field. We also consider the ATI process in bicircular field which consists of two coplanar counter-rotating circularly polarized fields.
Distribution of some sequences of points on elliptic curves
DEFF Research Database (Denmark)
Lange, Tanja; Shparlinski, Igor
2007-01-01
We estimate character sums over points on elliptic curves over a finite field of q elements. Pseudorandom sequences can be constructed by taking linear combinations with small coefficients (for example, from the set {−1, 0, 1}) of a fixed vector of points, which forms the seed of the generator. We...... consider several particular cases of this general approach which are of special practical interest and have occurred in the literature. For each of them we show that the resulting sequence has good uniformity of distribution properties....
On state estimation and fusion with elliptical constraints
Energy Technology Data Exchange (ETDEWEB)
Rao, Nageswara S. [ORNL; Liu, Qiang [ORNL
2017-11-01
We consider tracking of a target with elliptical nonlinear constraints on its motion dynamics. The state estimates are generated by sensors and sent over long-haul links to a remote fusion center for fusion. We show that the constraints can be projected onto the known ellipse and hence incorporated into the estimation and fusion process. In particular, two methods based on (i) direct connection to the center, and (ii) shortest distance to the ellipse are discussed. A tracking example is used to illustrate the tracking performance using projection-based methods with various fusers in the lossy long-haul tracking environment.
Ultraluminous Infrared Mergers: Elliptical Galaxies in Formation?
Genzel, R.; Tacconi, L. J.; Rigopoulou, D.; Lutz, D.; Tecza, M.
2001-12-01
We report high-quality near-IR spectroscopy of 12 ultraluminous infrared galaxy mergers (ULIRGs). Our new VLT and Keck data provide ~0.5" resolution, stellar and gas kinematics of these galaxies, most of which are compact systems in the last merger stages. We confirm that ULIRG mergers are ``ellipticals in formation.'' Random motions dominate their stellar dynamics, but significant rotation is common. Gasdynamics and stellar dynamics are decoupled in most systems. ULIRGs fall on or near the fundamental plane of hot stellar systems, and especially on its less evolution-sensitive, reff-σ projection. The ULIRG velocity dispersion distribution, their location in the fundamental plane, and their distribution of vrotsini/σ closely resemble those of intermediate-mass (~L*), elliptical galaxies with moderate rotation. As a group ULIRGs do not resemble giant ellipticals with large cores and little rotation. Our results are in good agreement with other recent studies indicating that disky ellipticals with compact cores or cusps can form through dissipative mergers of gas-rich disk galaxies while giant ellipticals with large cores have a different formation history. Based on observations at the European Southern Observatory, Chile (ESO 65.N-0266, 65.N-0289), and on observations at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, The University of California, and the National Aeronautics and Space Administration. The Keck Observatory was made possible by the general financial support by the W. M. Keck Foundation.
Energy Technology Data Exchange (ETDEWEB)
Hoeckel, M.; Luechinger, P.
2003-07-01
This is the sixth part of a ten-part final report for the Swiss Federal Office of Energy (SFOE) on a project that looked into potential problems relating to the Swiss electricity distribution grid with respect to the increasing number of distributed power generation facilities being put into service. The identification of special conditions for the grid's operation and future development that take increasing decentralised power production into account are discussed. The results of the project activities encompass the analysis and evaluation of various problem areas associated with planning and management of the grid during normal operation and periods of malfunction, as well as required modifications to safety systems and grid configurations. This fifth appendix to the main report presents and discusses the results of simulations made on the basis of the real-life 400 V low-voltage distribution network operated by the public utilities of the City of Zurich, Switzerland. This comprehensive appendix describes the simulation methods used and the basic characteristics of low-voltage networks and distributed generation facilities. The 6 simulation variants used are also described. The results of the simulations are presented in graphical form and provide profiles of voltage and current, active and reactive power and further mains characteristics for varying load conditions. Also, short-circuit simulations and harmonics analysis are discussed.
Gu, Bing; Xu, Danfeng; Rui, Guanghao; Lian, Meng; Cui, Yiping; Zhan, Qiwen
2015-09-20
Generation of vectorial optical fields with arbitrary polarization distribution is of great interest in areas where exotic optical fields are desired. In this work, we experimentally demonstrate the versatile generation of linearly polarized vector fields, elliptically polarized vector fields, and circularly polarized vortex beams through introducing attenuators in a common-path interferometer. By means of Richards-Wolf vectorial diffraction method, the characteristics of the highly focused elliptically polarized vector fields are studied. The optical force and torque on a dielectric Rayleigh particle produced by these tightly focused vector fields are calculated and exploited for the stable trapping of dielectric Rayleigh particles. It is shown that the additional degree of freedom provided by the elliptically polarized vector field allows one to control the spatial structure of polarization, to engineer the focusing field, and to tailor the optical force and torque on a dielectric Rayleigh particle.