Multiblock grid generation for jet engine configurations
Stewart, Mark E. M.
1992-01-01
The goal was to create methods for generating grids with minimal human intervention that are applicable to a wide range of problems and compatible with existing numerical methods and with existing and proposed computers. The following topics that are related to multiblock grid generation are briefly covered in viewgraph form: finding a domain decomposition, dimensioning grids, grid smoothing, manipulating grids and decompositions, and some specializations for jet engine configurations.
Multiblock grid generation with automatic zoning
Eiseman, Peter R.
1995-01-01
An overview will be given for multiblock grid generation with automatic zoning. We shall explore the many advantages and benefits of this exciting technology and will also see how to apply it to a number of interesting cases. The technology is available in the form of a commercial code, GridPro(registered trademark)/az3000. This code takes surface geometry definitions and patterns of points as its primary input and produces high quality grids as its output. Before we embark upon our exploration, we shall first give a brief background of the environment in which this technology fits.
Pontoon Bridge Hydrodynamic Computations by Multi-block Grid Generation Technique
Institute of Scientific and Technical Information of China (English)
PAN Xiao-qiang; SHEN Qing
2006-01-01
To investigate the hydrodynamic characteristic of pontoon bridge, the multi-block grid generation technique with numerical methods for viscous fluid dynamics is applied to numerical simulations on the hydrodynamic characteristic of a ribbon ferrying raft model at a series of towing speeds. Comparison of the simulated results with the experimental data indicates that the simulated results are acceptable. It shows that the multi-block grid generation technique is effective in the computation on pontoon bridge hydrodynamics.
Algorithms for the automatic generation of 2-D structured multi-block grids
Schoenfeld, Thilo; Weinerfelt, Per; Jenssen, Carl B.
1995-01-01
Two different approaches to the fully automatic generation of structured multi-block grids in two dimensions are presented. The work aims to simplify the user interactivity necessary for the definition of a multiple block grid topology. The first approach is based on an advancing front method commonly used for the generation of unstructured grids. The original algorithm has been modified toward the generation of large quadrilateral elements. The second method is based on the divide-and-conquer paradigm with the global domain recursively partitioned into sub-domains. For either method each of the resulting blocks is then meshed using transfinite interpolation and elliptic smoothing. The applicability of these methods to practical problems is demonstrated for typical geometries of fluid dynamics.
A multiblock grid generation technique applied to a jet engine configuration
Stewart, Mark E. M.
1992-01-01
Techniques are presented for quickly finding a multiblock grid for a 2D geometrically complex domain from geometrical boundary data. An automated technique for determining a block decomposition of the domain is explained. Techniques for representing this domain decomposition and transforming it are also presented. Further, a linear optimization method may be used to solve the equations which determine grid dimensions within the block decomposition. These algorithms automate many stages in the domain decomposition and grid formation process and limit the need for human intervention and inputs. They are demonstrated for the meridional or throughflow geometry of a bladed jet engine configuration.
Su, T. Y.; Appleby, R. A.; Chen, H. C.
1991-01-01
The BCON is a menu-driven graphics interface program whose input consists of strings or arrays of points generated from a computer aided design (CAD) tool or any other surface geometry source. The user needs to design the block topology and prepare the surface geometry definition and surface grids separately. The BCON generates input files that contain the block definitions and the block relationships required for generating a multiblock volume grid with the EAGLE grid generation package. The BCON also generates the block boundary conditions file which is used along with the block relationship file as input for the general multiblock Euler (GMBE) code (GMBE, volumes 1 and 3).
Singularity classification as a design tool for multiblock grids
Jones, Alan K.
1992-01-01
A major stumbling block in interactive design of 3-D multiblock grids is the difficulty of visualizing the design as a whole. One way to make this visualization task easier is to focus, at least in early design stages, on an aspect of the grid which is inherently easy to present graphically, and to conceptualize mentally, namely the nature and location of singularities in the grid. The topological behavior of a multiblock grid design is determined by what happens at its edges and vertices. Only a few of these are in any way exceptional. The exceptional behaviors lie along a singularity graph, which is a 1-D construct embedded in 3-D space. The varieties of singular behavior are limited enough to make useful symbology on a graphics device possible. Furthermore, some forms of block design manipulation that appear appropriate to the early conceptual-modeling phase can be accomplished on this level of abstraction. An overview of a proposed singularity classification scheme and selected examples of corresponding manipulation techniques is presented.
Getting a Grip on Grid Generation
2002-01-01
GridPro is an automatic, object-oriented, multi-block grid generator that provides ease of use, high quality, rapid production, and parametric design. When paired with a 3-D graphic user interface called az- Manager, GridPro presents users with an extremely efficient, interactive capability to build topology, edit surfaces, set computational fluid dynamics (CFD) boundary conditions, and view multi-block grids. The origins of the GridPro technology date back to a 1989 SBIR contract with NASA's Glenn Research Center, in which Glenn was seeking a multi-block grid generation program that would run automatically upon identifying a pattern of grid blocks supplied by a user. The technology is currently used in many engineering fields, including aerospace, turbo- machinery, automotive, and chemical industries.
GENIE(++): A Multi-Block Structured Grid System
Williams, Tonya; Nadenthiran, Naren; Thornburg, Hugh; Soni, Bharat K.
1996-01-01
The computer code GENIE++ is a continuously evolving grid system containing a multitude of proven geometry/grid techniques. The generation process in GENIE++ is based on an earlier version. The process uses several techniques either separately or in combination to quickly and economically generate sculptured geometry descriptions and grids for arbitrary geometries. The computational mesh is formed by using an appropriate algebraic method. Grid clustering is accomplished with either exponential or hyperbolic tangent routines which allow the user to specify a desired point distribution. Grid smoothing can be accomplished by using an elliptic solver with proper forcing functions. B-spline and Non-Uniform Rational B-splines (NURBS) algorithms are used for surface definition and redistribution. The built in sculptured geometry definition with desired distribution of points, automatic Bezier curve/surface generation for interior boundaries/surfaces, and surface redistribution is based on NURBS. Weighted Lagrance/Hermite transfinite interpolation methods, interactive geometry/grid manipulation modules, and on-line graphical visualization of the generation process are salient features of this system which result in a significant time savings for a given geometry/grid application.
Structured grid generator on parallel computers
Energy Technology Data Exchange (ETDEWEB)
Muramatsu, Kazuhiro; Murakami, Hiroyuki; Higashida, Akihiro; Yanagisawa, Ichiro
1997-03-01
A general purpose structured grid generator on parallel computers, which generates a large-scale structured grid efficiently, has been developed. The generator is applicable to Cartesian, cylindrical and BFC (Boundary-Fitted Curvilinear) coordinates. In case of BFC grids, there are three adaptable topologies; L-type, O-type and multi-block type, the last of which enables any combination of L- and O-grids. Internal BFC grid points can be automatically generated and smoothed by either algebraic supplemental method or partial differential equation method. The partial differential equation solver is implemented on parallel computers, because it consumes a large portion of overall execution time. Therefore, high-speed processing of large-scale grid generation can be realized by use of parallel computer. Generated grid data are capable to be adjusted to domain decomposition for parallel analysis. (author)
Multiblock, Multigrid Solution Of Euler Equations
Melson, N. Duane; Cannizzaro, Frank E.; Von Lavante, E.
1994-01-01
Method of numerical solution of Euler equations of three-dimensional flow of compressible fluid involves combination of multiblock and multigrid strategies. In multiblock strategy, flow field divided, into multiple smaller, more computationally-convenient zones and computational grid fitted to applicable flow boundaries generated in each block. In multigrid strategy used here, different quantities computed, variously, on finer or coarser grids. Minimizing cost of computation by using fewest grid points yielding acceptably accurate values of affected variable. Multigrid strategy found effective in accelerating convergence to steady state, while multiblock strategy provides geometric flexibility.
TIGGERC: Turbomachinery Interactive Grid Generator for 2-D Grid Applications and Users Guide
Miller, David P.
1994-01-01
A two-dimensional multi-block grid generator has been developed for a new design and analysis system for studying multiple blade-row turbomachinery problems. TIGGERC is a mouse driven, interactive grid generation program which can be used to modify boundary coordinates and grid packing and generates surface grids using a hyperbolic tangent or algebraic distribution of grid points on the block boundaries. The interior points of each block grid are distributed using a transfinite interpolation approach. TIGGERC can generate a blocked axisymmetric H-grid, C-grid, I-grid or O-grid for studying turbomachinery flow problems. TIGGERC was developed for operation on Silicon Graphics workstations. Detailed discussion of the grid generation methodology, menu options, operational features and sample grid geometries are presented.
TIGGERC: Turbomachinery interactive grid generator energy distributor and restart code
Miller, David P.
1992-01-01
A two dimensional multi-block grid generator was developed for a new design and analysis system for studying multi-blade row turbomachinery problems with an axisymmetric viscous/inviscid 'average passage' through flow code. TIGGERC is a mouse driven, fully interactive grid generation program which can be used to modify boundary coordinates and grid packing. TIGGERC generates grids using a hyperbolic tangent or algebraic distribution of grid points on the block boundaries and the interior points of each block grid are distributed using a transfinite interpolation approach. TIGGERC generates a blocked axisymmetric H grid, C grid, I grid, or O grid for studying turbomachinery flow problems. TIGGERC was developed for operation on small high speed graphic workstations.
Generation of Multiblock Copolymers by PCR : Synthesis, Visualization and Nanomechanical Properties
Alemdaroglu, Fikri E.; Zhuang, Wei; Zöphel, Lukas; Wang, Jie; Berger, Rüdiger; Rabe, Jürgen P.; Herrmann, Andreas
2009-01-01
PCR was successfully implemented into polymer chemistry to produce linear multiblock structures up to pentablock architectures. Salient features of the generated DNA polymer hybrids were the ultrahigh molecular weights and their structural accuracy. Besides pushing the limits in block copolymer synt
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.
Peng, Ao-Ping; Li, Zhi-Hui; Wu, Jun-Lin; Jiang, Xin-Yu
2016-12-01
Based on the previous researches of the Gas-Kinetic Unified Algorithm (GKUA) for flows from highly rarefied free-molecule transition to continuum, a new implicit scheme of cell-centered finite volume method is presented for directly solving the unified Boltzmann model equation covering various flow regimes. In view of the difficulty in generating the single-block grid system with high quality for complex irregular bodies, a multi-block docking grid generation method is designed on the basis of data transmission between blocks, and the data structure is constructed for processing arbitrary connection relations between blocks with high efficiency and reliability. As a result, the gas-kinetic unified algorithm with the implicit scheme and multi-block docking grid has been firstly established and used to solve the reentry flow problems around the multi-bodies covering all flow regimes with the whole range of Knudsen numbers from 10 to 3.7E-6. The implicit and explicit schemes are applied to computing and analyzing the supersonic flows in near-continuum and continuum regimes around a circular cylinder with careful comparison each other. It is shown that the present algorithm and modelling possess much higher computational efficiency and faster converging properties. The flow problems including two and three side-by-side cylinders are simulated from highly rarefied to near-continuum flow regimes, and the present computed results are found in good agreement with the related DSMC simulation and theoretical analysis solutions, which verify the good accuracy and reliability of the present method. It is observed that the spacing of the multi-body is smaller, the cylindrical throat obstruction is greater with the flow field of single-body asymmetrical more obviously and the normal force coefficient bigger. While in the near-continuum transitional flow regime of near-space flying surroundings, the spacing of the multi-body increases to six times of the diameter of the single
Ghaffari, Farhad; Luckring, James M.; Thomas, James L.; Bates, Brent L.; Biedron, Robert T.
1991-01-01
Three-dimensional thin-layer Navier-Stokes computations are presented for the F/A-18 configuration. The modeled configuration includes an accurate surface representation of the fuselage, leading-edge-extension, as well as the wing with and without leading-edge-flap deflection. A multi-block structured volume grid with various topologies is generated using transfinite interpolation technique. The flowfield domain is divided into twenty blocks, each representing a particular geometrical complexity of the configuration. The results are obtained from an algorithm for solving the compressible Navier-Stokes equations that incorporates an upwind-biased, flux-difference-splitting approach. In addition, a newly developed capability that allows for generalized surface patching among blocks is employed. Turbulent results are presented for flow conditions that correspond to recent NASA F/A-18 High Alpha Research Vehicle flight experiments. Good correlations between the computations and the flight test results are disclosed for both surface flow patterns as well as surface pressure distributions.
Applications of algebraic grid generation
Eiseman, Peter R.; Smith, Robert E.
1990-01-01
Techniques and applications of algebraic grid generation are described. The techniques are univariate interpolations and transfinite assemblies of univariate interpolations. Because algebraic grid generation is computationally efficient, the use of interactive graphics in conjunction with the techniques is advocated. A flexible approach, which works extremely well in an interactive environment, called the control point form of algebraic grid generation is described. The applications discussed are three-dimensional grids constructed about airplane and submarine configurations.
Institute of Scientific and Technical Information of China (English)
Zi-niu Wu
2003-01-01
For nonlinear hyperbolic problems, conservation of the numerical scheme is importantfor convergence to the correct weak solutions. In this paper the conservation of the well-known compact scheme up to fourth order of accuracy on a single and uniform grid isstudied, and a conservative interface treatment is derived for compact schemes on patchedgrids. For a pure initial value problem, the compact scheme is shown to be equivalent toa scheme in the usual conservative form. For the case of a mixed initial boundary valueproblem, the compact scheme is conservative only if the rounding errors are small enough.For a patched grid interface, a conservative interface condition useful for mesh refinementand for parallel computation is derived and its order of local accuracy is analyzed.
Treiber, David A.; Muilenburg, Dennis A.
1995-01-01
The viability of applying a state-of-the-art Euler code to calculate the aerodynamic forces and moments through maximum lift coefficient for a generic sharp-edge configuration is assessed. The OVERFLOW code, a method employing overset (Chimera) grids, was used to conduct mesh refinement studies, a wind-tunnel wall sensitivity study, and a 22-run computational matrix of flow conditions, including sideslip runs and geometry variations. The subject configuration was a generic wing-body-tail geometry with chined forebody, swept wing leading-edge, and deflected part-span leading-edge flap. The analysis showed that the Euler method is adequate for capturing some of the non-linear aerodynamic effects resulting from leading-edge and forebody vortices produced at high angle-of-attack through C(sub Lmax). Computed forces and moments, as well as surface pressures, match well enough useful preliminary design information to be extracted. Vortex burst effects and vortex interactions with the configuration are also investigated.
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
An electrostatic analog for generating cascade grids
Adamczyk, J. J.
1980-01-01
Accurate and efficient numerical simulation of flows through turbomachinery blade rows depends on the topology of the computational grids. These grids must reflect the periodic nature of turbomachinery blade row geometries and conform to the blade shapes. Three types of grids can be generated that meet these minimal requirements: through-flow grids, O-type grids, and C-type grids. A procedure which can be used to generate all three types of grids is presented. The resulting grids are orthogonal and can be stretched to capture the essential physics of the flow. A discussion is also presented detailing the extension of the generation procedure to three dimensional geometries.
Algebraic grid generation for complex geometries
Shih, T. I.-P.; Bailey, R. T.; Nguyen, H. L.; Roelke, R. J.
1991-01-01
An efficient computer program called GRID2D/3D has been developed to generate single and composite grid systems within geometrically complex two- and three-dimensional (2D and 3D) spatial domains that can deform with time. GRID2D/3D generates single grid systems by using algebraic grid generation methods based on transfinite interpolation. The distribution of grid points within the spatial domain is controlled by stretching functions and grid lines can intersect boundaries of the spatial domain orthogonally. GRID2D/3D generates composite grid systems by patching together two or more single grid systems. The patching can be discontinuous or continuous. For 2D spatial domains the boundary curves are constructed by using either cubic or tension spline interpolation. For 3D spatial domains the boundary surfaces are constructed by using a new technique, developed in this study, referred to as 3D bidirectional Hermite interpolation.
GridTool: A surface modeling and grid generation tool
Samareh-Abolhassani, Jamshid
1995-01-01
GridTool is designed around the concept that the surface grids are generated on a set of bi-linear patches. This type of grid generation is quite easy to implement, and it avoids the problems associated with complex CAD surface representations and associated surface parameterizations. However, the resulting surface grids are close to but not on the original CAD surfaces. This problem can be alleviated by projecting the resulting surface grids onto the original CAD surfaces. GridTool is designed primary for unstructured grid generation systems. Currently, GridTool supports VGRID and FELISA systems, and it can be easily extended to support other unstructured grid generation systems. The data in GridTool is stored parametrically so that once the problem is set up, one can modify the surfaces and the entire set of points, curves and patches will be updated automatically. This is very useful in a multidisciplinary design and optimization process. GridTool is written entirely in ANSI 'C', the interface is based on the FORMS library, and the graphics is based on the GL library. The code has been tested successfully on IRIS workstations running IRIX4.0 and above. The memory is allocated dynamically, therefore, memory size will depend on the complexity of geometry/grid. GridTool data structure is based on a link-list structure which allows the required memory to expand and contract dynamically according to the user's data size and action. Data structure contains several types of objects such as points, curves, patches, sources and surfaces. At any given time, there is always an active object which is drawn in magenta, or in their highlighted colors as defined by the resource file which will be discussed later.
Energy Technology Data Exchange (ETDEWEB)
Bischof, C.H.; Mauer, A. [Argonne National Lab., IL (United States). Mathematics and Computer Science Division; Jones, W.T. [Computer Sciences Corp., Hampton, VA (United States)] [and others
1995-12-31
Automatic differentiation (AD) is a methodology for developing reliable sensitivity-enhanced versions of arbitrary computer programs with little human effort. It can vastly accelerate the use of advanced simulation codes in multidisciplinary design optimization, since the time for generating and verifying derivative codes is greatly reduced. In this paper, we report on the application of the recently developed ADIC automatic differentiation tool for ANSI C programs to the CSCMDO multiblock three-dimensional volume grid generator. The ADIC-generated code can easily be interfaced with Fortran derivative codes generated with the ADIFOR AD tool FORTRAN 77 programs, thus providing efficient sensitivity-enhancement techniques for multilanguage, multidiscipline problems.
Kite Generator System: Grid Integration and Validation
Ahmed, Mariam; Hably, Ahmad; Bacha, Seddik; Ovalle, Andres
2014-01-01
International audience; In this paper, the problem of grid integration of a kite generator system (KGS), is handled. The mechanical power generated by the kite's traction is translated into an electrical one via a permanent magnet synchronous machine. This power is then injected in the grid or used to supply an isolated load after passing a power electronics interface. Control schemes have been developed for grid connected or stand-alone operation and tested on a hardware-in-the-loop simulator.
Computing Aerodynamic Performance of a 2D Iced Airfoil: Blocking Topology and Grid Generation
Chi, X.; Zhu, B.; Shih, T. I.-P.; Slater, J. W.; Addy, H. E.; Choo, Yung K.; Lee, Chi-Ming (Technical Monitor)
2002-01-01
The ice accrued on airfoils can have enormously complicated shapes with multiple protruded horns and feathers. In this paper, several blocking topologies are proposed and evaluated on their ability to produce high-quality structured multi-block grid systems. A transition layer grid is introduced to ensure that jaggedness on the ice-surface geometry do not to propagate into the domain. This is important for grid-generation methods based on hyperbolic PDEs (Partial Differential Equations) and algebraic transfinite interpolation. A 'thick' wrap-around grid is introduced to ensure that grid lines clustered next to solid walls do not propagate as streaks of tightly packed grid lines into the interior of the domain along block boundaries. For ice shapes that are not too complicated, a method is presented for generating high-quality single-block grids. To demonstrate the usefulness of the methods developed, grids and CFD solutions were generated for two iced airfoils: the NLF0414 airfoil with and without the 623-ice shape and the B575/767 airfoil with and without the 145m-ice shape. To validate the computations, the computed lift coefficients as a function of angle of attack were compared with available experimental data. The ice shapes and the blocking topologies were prepared by NASA Glenn's SmaggIce software. The grid systems were generated by using a four-boundary method based on Hermite interpolation with controls on clustering, orthogonality next to walls, and C continuity across block boundaries. The flow was modeled by the ensemble-averaged compressible Navier-Stokes equations, closed by the shear-stress transport turbulence model in which the integration is to the wall. All solutions were generated by using the NPARC WIND code.
National Aeronautics and Space Administration — Structured multiblock grid of HIRENASD wing with medium grid density, about 10 mill grid points, 9.5 mill cells. Starting from coarse AIAA AEPW structured grid,...
IGES transformer and NURBS in grid generation
Yu, Tzu-Yi; Soni, Bharat K.
1993-01-01
In the field of Grid Generation and the CAD/CAM, there are numerous geometry output formats which require the designer to spend a great deal of time manipulating geometrical entities in order to achieve a useful sculptured geometrical description for grid generation. Also in this process, there is a danger of losing fidelity of the geometry under consideration. This stresses the importance of a standard geometry definition for the communication link between varying CAD/CAM and grid system. The IGES (Initial Graphics Exchange Specification) file is a widely used communication between CAD/CAM and the analysis tools. The scientists at NASA Research Centers - including NASA Ames, NASA Langley, NASA Lewis, NASA Marshall - have recognized this importance and, therefore, in 1992 they formed the committee of the 'NASA-IGES' which is the subset of the standard IGES. This committee stresses the importance and encourages the CFD community to use the standard IGES file for the interface between the CAD/CAM and CFD analysis. Also, two of the IGES entities -- the NURBS Curve (Entity 126) and NURBS Surface (Entity 128) -- which have many useful geometric properties -- like the convex hull property, local control property and affine invariance, also widely utilized analytical geometries can be accurately represented using NURBS. This is important in today grid generation tools because of the emphasis of the interactive design. To satisfy the geometry transformation between the CAD/CAM system and Grid Generation field, the CAGI (Computer Aided Geometry Design) developed, which include the Geometry Transformation, Geometry Manipulation and Geometry Generation as well as the user interface. This paper will present the successful development IGES file transformer and application of NURBS definition in the grid generation.
A numerical grid generation technique
Gilding, B.H.
1988-01-01
The paper describes a technique for the generation of boundary-fitted curvilinear coordinate systems for the numerical solution of partial differential equations in two space dimensions. The technique is algebraic, has a transfinite character, and is based on the blending of shearing transformations
Institute of Scientific and Technical Information of China (English)
胡斌; 潘光; 杜晓旭; 黄桥高; 王一云
2012-01-01
文章首先建立了全附体潜艇的几何模型,基于分块网格技术耦合生成了全附体的SUBOFFAFF-8潜艇外流场高质量结构化网格,采用RANS雷诺时均方法和SST k-ω湍流模型,并基于有限体积法(FVM),对潜艇粘性绕流场进行了数值计算研究.给出了潜艇纵中剖面线上压力系数、壁面剪应力系数,指挥台围壳和上尾翼表面三个不同高度处压力系数的纵向分布,以及模型总阻力的数值计算结果；并与DTMB水池试验结果进行了对比.结果表明,文中采用的数值模拟方法精度较高,合理有效,为深入研究全附体潜艇粘性绕流场奠定了基础.%Sections 1 and 2 of the full paper explain how we apply CFD (computational fluid dynamics) to calculating the viscous flow around a full-appendage submarine. Their core consists of; ( 1 ) we establish the geometric model of the SUBOFF AFF-8 full-appendage submarine and generate the high-quality multi-block structural grid of its flow field; (2) we use the Reynolds time-averaged method, the SST k-w turbulence model and the finite volume method to numerically calculate the steady viscous flow around the submarine; (3) we give the longitudinal distributions of the pressure coefficient and wall shear stress coefficient along the upper meridian line and also the pressure coefficients at the three heights of the fairwater and the stern respectively; we also give the calculation results of the total resistance of the submarine and compare them with the experimental results obtained from the DTMB tow tank in the U. S. The simulation results, given in Figs. 4 through 9 and Table 1, and their analysis show preliminarily that the calculation results obtained with our method agree well with the experimental results obtained from the DTMB tow tank; this indicates that our numerical calculation method has high precision and is valid and effective, thus laying a solid foundation for the further study of the viscous flow around a
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.
OVERGRID: A Unified Overset Grid Generation Graphical Interface
Chan, William M.; Akien, Edwin W. (Technical Monitor)
1999-01-01
This paper presents a unified graphical interface and gridding strategy for performing overset grid generation. The interface called OVERGRID has been specifically designed to follow an efficient overset gridding strategy, and contains general grid manipulation capabilities as well as modules that are specifically suited for overset grids. General grid utilities include functions for grid redistribution, smoothing, concatenation, extraction, extrapolation, projection, and many others. Modules specially tailored for overset grids include a seam curve extractor, hyperbolic and algebraic surface grid generators, a hyperbolic volume grid generator, and a Cartesian box grid generator, Grid visualization is achieved using OpenGL while widgets are constructed with Tcl/Tk. The software is portable between various platforms from UNIX workstations to personal computers.
Grid generation software engineering at Los Alamos
Energy Technology Data Exchange (ETDEWEB)
Clark, G.L.; Ankeny, L.A.
1988-01-01
We have collected and re-engineered a small library of computer codes for general-purpose grid generation in one-, two-, and three-dimensional domains. The design intent was to produce easy-to-use general purpose codes that are portable to as many different hardware and software environments as practical, that are consistent in programming style and user interface, and that cover a gamut of applications. The paper describes some of the features of the codes, emphasizing the perspective of the potential user or programmer, rather than that of the researcher interested in mathematical techniques. 7 refs., 3 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...
Grid Voltage Synchronization for Distributed Generation Systems under Grid Fault Conditions
DEFF Research Database (Denmark)
Luna, Alvaro; Rocabert, J.; Candela, I.
2015-01-01
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 on the installat......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...
Grid generation: Algebraic and partial differential equations techniques revisited
Soni, Bharat K.
A systematic procedure for grid generation which can provide compuational grids for a wide range of geometries related to internal/external flow configuration is developed by combining the best features of algebraic and elliptic grid generation systems. The algebraic and elliptic grid generation system are well developed in the literature. A revisit to these techniques is given in this paper in view of economy and efficiency of the grid generation process. A technique to automatically calculate slopes and twist vectors required in hermite transfinite interpolation is developed. The weighted transfinite interpolation is combined with automatically created Bezier, B-spline curves, and Non-Uniform Rational B-spline (NURB) curves to generate well-distributed, smooth and near orthogonal grid patches (sub-blocks). A novel approach to evaluate control functions for elliptic generation systems is developed. This approach allows a quick refinement utilizing elliptic system. Computational examples are presented to demonstrate the success of these methodologies.
Structured adaptive grid generation using algebraic methods
Yang, Jiann-Cherng; Soni, Bharat K.; Roger, R. P.; Chan, Stephen C.
1993-01-01
The accuracy of the numerical algorithm depends not only on the formal order of approximation but also on the distribution of grid points in the computational domain. Grid adaptation is a procedure which allows optimal grid redistribution as the solution progresses. It offers the prospect of accurate flow field simulations without the use of an excessively timely, computationally expensive, grid. Grid adaptive schemes are divided into two basic categories: differential and algebraic. The differential method is based on a variational approach where a function which contains a measure of grid smoothness, orthogonality and volume variation is minimized by using a variational principle. This approach provided a solid mathematical basis for the adaptive method, but the Euler-Lagrange equations must be solved in addition to the original governing equations. On the other hand, the algebraic method requires much less computational effort, but the grid may not be smooth. The algebraic techniques are based on devising an algorithm where the grid movement is governed by estimates of the local error in the numerical solution. This is achieved by requiring the points in the large error regions to attract other points and points in the low error region to repel other points. The development of a fast, efficient, and robust algebraic adaptive algorithm for structured flow simulation applications is presented. This development is accomplished in a three step process. The first step is to define an adaptive weighting mesh (distribution mesh) on the basis of the equidistribution law applied to the flow field solution. The second, and probably the most crucial step, is to redistribute grid points in the computational domain according to the aforementioned weighting mesh. The third and the last step is to reevaluate the flow property by an appropriate search/interpolate scheme at the new grid locations. The adaptive weighting mesh provides the information on the desired concentration
Institute of Scientific and Technical Information of China (English)
李桂波; 杨国伟
2011-01-01
从并行计算流体力学程序的稳定性和效率两大问题入手,针对多块结构网格的通用数据传输方法和基于遗传优化算法的负载平衡方法,并在已有串行多块结构网格程序基础上发展了相应的并行程序.该并行程序以物理区域分割为基础,采用MPI实现消息传递,适用于各种不同的并行机体系结构,具有很好的可移植性.大量数值实验证明,本文发展的并行程序具有良好的稳定性和并行效率,可以进一步应用于大规模实际工程计算.%In order to improve stability and efficiency of computational fluid dynamics ( CFD) program , a general data transfer method and a genetic algorithm load balance strategy-based, are presented in this paper, A parallel program is developed on the basis of existing serial program for the multiblock structured grid. This parallel program whose message transport mechanism is based on the MPI can be run on different parallel computer architectures and has better portability.Many numerical experiments show that the parallel program is stable and efficient and can be further applied to massively engineering computations.
MESH2D GRID GENERATOR DESIGN AND USE
Energy Technology Data Exchange (ETDEWEB)
Flach, G.; Smith, F.
2012-01-20
Mesh2d is a Fortran90 program 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). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j{sub 0}) coordinates along index i are permitted to undulate or otherwise vary. 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. The overall mesh is constructed from grid zones that are typically then subdivided into a collection of smaller grid cells. The grid zones usually correspond to distinct materials or larger-scale geometric shapes. The structured grid zones are identified through uppercase indices (I,J). Subdivision of zonal regions into grid cells can be done uniformly, or nonuniformly using either a polynomial or geometric skewing algorithm. Grid cells may be concentrated backward, forward, or toward both ends. Figure 1 illustrates the above concepts in the context of a simple four zone grid.
The turbulent flow generated by inhomogeneous multiscale grids
Zheng, Shaokai; Bruce, Paul J. K.; Graham, J. Michael R.; Vassilicos, John Christos
2015-11-01
A group of inhomogeneous multiscale grids have been designed and tested in a low speed wind tunnel in an attempt to generate bespoke turbulent shear flows. Cross-wire anemometry measurements were performed in different planes parallel to the grid and at various streamwise locations to study turbulence development behind each of the different geometry grids. Two spatially separated single hot wires were also used to measure transverse integral length scale at selected locations. Results are compared to previous studies of shearless mixing layer grids and fractal grids, including mean flow profiles and turbulence statistics.
Surface and Volume Grid Generation in Parametric Form
Yu, Tzuyi; Soni, Bharat K.; Benjamin, Ted; Williams, Robert
1996-01-01
The algorithm for surface modeling and volume grid generation using parametric Non-Uniform Rational B-splines (NURBS) geometric representation are presented. The enhanced re-parameterization algorithm which can yield a desired physical distribution on the curve, surface, and volume is also presented. This approach bridges the gap between computer aided design surface/volume definition and surface/volume grid generation.
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....
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.
A Computational Differential Geometry Approach to Grid Generation
Liseikin, Vladimir D
2007-01-01
The process of breaking up a physical domain into smaller sub-domains, known as meshing, facilitates the numerical solution of partial differential equations used to simulate physical systems. This monograph gives a detailed treatment of applications of geometric methods to advanced grid technology. It focuses on and describes a comprehensive approach based on the numerical solution of inverted Beltramian and diffusion equations with respect to monitor metrics for generating both structured and unstructured grids in domains and on surfaces. In this second edition the author takes a more detailed and practice-oriented approach towards explaining how to implement the method by: Employing geometric and numerical analyses of monitor metrics as the basis for developing efficient tools for controlling grid properties. Describing new grid generation codes based on finite differences for generating both structured and unstructured surface and domain grids. Providing examples of applications of the codes to the genera...
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.
An Efficient Grid Generation Method for Arbitrary Domains
Orme, Melissa; Huang, Changzheng
1997-11-01
This paper describes an efficient grid generation method for arbitrary or multiply connected domains. Our method, essentially based on the edge swapping techniques, combines the advantages of the Delaunay triangulation method and the advancing front method. The latter two methods are in popular use nowadays. But both suffer some limitations. Delaunay method generates high quality grid but grid may cut across the boundary in concave regions. Advancing front method works for general domain but may encounter difficulties where fronts have to be merged. The current method garantees the boundary integrity and attains the nice Delaunay features into the domain. This is achieved by carefully documenting the grid information so that each edge is readily identified to be inside or outside the domain; and (2) continuously swapping out those bad edges that destroy the Delaunay properties. The computer program built on this method allows users to control the grid density distribution by specifying typical grid sizes on a few chosen points. Interesting examples are demonstrated here. One of them is a circular domain with three letters APS inside. (see figure 1 and figure 2 ). Given a grid size for APS and another size for the circle, the program automatically generates a smooth triangular grid regardless of the complex multiply connected geometry.
A turbulent premixed flame on fractal-grid generated turbulence
Soulopoulos, Nikos; Beyrau, Frank; Hardalupas, Yannis; Taylor, A M K P; Vassilicos, J Christos
2010-01-01
A space-filling, low blockage fractal grid is used as a novel turbulence generator in a premixed turbulent combustion experiment. In contrast to the power law decay of a standard turbulence grid, the downstream turbulence intensity of the fractal grid increases until it reaches a peak at some distance from the grid before it finally decays. The effective mesh size and the solidity are the same as those of a standard square mesh grid with which it is compared. It is found that, for the same flow rate and stoichiometry, the fractal generated turbulence enhances the burning rate and causes the flame to further increase its area. Using a flame fractal model, an attempt is made to highlight differences between the flames established at the two different turbulent fields.
Grid generation and inviscid flow computation about aircraft geometries
Smith, Robert E.
1989-01-01
Grid generation and Euler flow about fighter aircraft are described. A fighter aircraft geometry is specified by an area ruled fuselage with an internal duct, cranked delta wing or strake/wing combinations, canard and/or horizontal tail surfaces, and vertical tail surfaces. The initial step before grid generation and flow computation is the determination of a suitable grid topology. The external grid topology that has been applied is called a dual-block topology which is a patched C (exp 1) continuous multiple-block system where inner blocks cover the highly-swept part of a cranked wing or strake, rearward inner-part of the wing, and tail components. Outer-blocks cover the remainder of the fuselage, outer-part of the wing, canards and extend to the far field boundaries. The grid generation is based on transfinite interpolation with Lagrangian blending functions. This procedure has been applied to the Langley experimental fighter configuration and a modified F-18 configuration. Supersonic flow between Mach 1.3 and 2.5 and angles of attack between 0 degrees and 10 degrees have been computed with associated Euler solvers based on the finite-volume approach. When coupling geometric details such as boundary layer diverter regions, duct regions with inlets and outlets, or slots with the general external grid, imposing C (exp 1) continuity can be extremely tedious. The approach taken here is to patch blocks together at common interfaces where there is no grid continuity, but enforce conservation in the finite-volume solution. The key to this technique is how to obtain the information required for a conservative interface. The Ramshaw technique which automates the computation of proportional areas of two overlapping grids on a planar surface and is suitable for coding was used. Researchers generated internal duct grids for the Langley experimental fighter configuration independent of the external grid topology, with a conservative interface at the inlet and outlet.
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.
SAUNA: A system for grid generation and flow simulation using hybrid structured/unstructured grids
Childs, P. N.; Shaw, J. A.; Peace, A. J.; Georgala, J. M.
1992-05-01
The development of a flow simulation facility for predicting the aerodynamics of complex configurations wherein the grid is composed of both structured and unstructured regions is described. Issues relating to the generation and analysis of such grids and to the accurate and efficient computation of both inviscid and viscous flows thereon are considered. Further the development of a comprehensive post-processing and visualization facility is explored. Techniques are illustrated throughout by application to realistic aircraft geometries.
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.
Marshall Space Flight Center surface modeling and grid generation applications
Williams, Robert W.; Benjamin, Theodore G.; Cornelison, Joni W.
1995-03-01
The Solid Rocket Motors (SRM) used by NASA to propel the Space Shuttle employ gimballing nozzles as a means for vehicular guidance during launch and ascent. Gimballing a nozzle renders the pressure field of the exhaust gases nonaxisymmetric. This has two effects: (1) it exerts a torque and side load on the nozzle; and (2) the exhaust gases flow circumferentially in the aft-dome region, thermally loading the flexible boot, case-to-nozzle joint, and casing insulation. The use of CFD models to simulate such flows is imperative in order to assess SRM design. The grids for these problems were constructed by obtaining information from drawings and tabulated coordinates. The 2D axisymmetric grids were designed and generated using the EZ-Surf and GEN2D surface and grid generation codes. These 2D grids were solved using codes such as FDNS, GASP, and MINT. These axisymmetric grids were rotated around the center-line to form 3D nongimballed grids. These were then gimballed around the pivot point and the gaps or overlaps resurfaced to obtain the final domains, which contained approximately 366,000 grid points. The 2D solutions were then rotated and manipulated as appropriate for geometry and used as initial guesses in the final solution. The analyses were used in answering questions about flight criteria.
A Parallel Multiblock Mesh Movement Scheme For Complex Aeroelastic Applications
Potsdam, Mark A.; Guruswamy, Guru P.
2000-01-01
A scheme has been developed for the movement of multiblock, structured grids due to surface deformation arising from aeroelastics, control surface movement, or design optimization. Elements of the method include a blending of a surface spline approximation and nearest surface point movement for block boundaries. Transfinite interpolation is employed for volume grid deformation. The scheme is demonstrated on a range of simple and complex aeroelastic aircraft applications using Navier-Stokes computational fluid dynamics and modal structural analyses on parallel processors. Results are robust and accurate, requiring only minimal user input specification.
FASTWO - A 2-D interactive algebraic grid generator
Luh, Raymond Ching-Chung; Lombard, C. K.
1988-01-01
This paper presents a very simple and effective computational procedure, FASTWO, for generating patched composite finite difference grids in 2-D for any geometry. Major components of the interactive graphics based method that is closely akin to and borrows many tools from transfinite interpolation are highlighted. Several grids produced by FASTWO are shown to illustrate its powerful capability. Comments about extending the methodology to 3-D are also given.
Triangle geometry processing for surface modeling and cartesian grid generation
Aftosmis, Michael J [San Mateo, CA; Melton, John E [Hollister, CA; Berger, Marsha J [New York, NY
2002-09-03
Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.
Geometry definition and grid generation for a complete fighter aircraft
Edwards, Thomas A.
1986-01-01
Recent advances in computing power and numerical solution procedures have enabled computational fluid dynamicists to attempt increasingly difficult problems. In particular, efforts are focusing on computations of complex three-dimensional flow fields about realistic aerodynamic bodies. To perform such computations, a very accurate and detailed description of the surface geometry must be provided, and a three-dimensional grid must be generated in the space around the body. The geometry must be supplied in a format compatible with the grid generation requirements, and must be verified to be free of inconsistencies. A procedure for performing the geometry definition of a fighter aircraft that makes use of a commercial computer-aided design/computer-aided manufacturing system is presented. Furthermore, visual representations of the geometry are generated using a computer graphics system for verification of the body definition. Finally, the three-dimensional grids for fighter-like aircraft are generated by means of an efficient new parabolic grid generation method. This method exhibits good control of grid quality.
Elliptic grid generation based on Laplace equations and algebraic transformations
Energy Technology Data Exchange (ETDEWEB)
Spekreuse, S.P. [National Aerospace Lab., Amsterdam (Netherlands)
1995-04-01
An elliptic grid generation method is presented to generate boundary conforming grids in domains in 2D and 3D physical space and on minimal surfaces and parametrized surfaces in 3D physical space. The elliptic grid generation method is based on the use of a composite mapping. This composite mapping consists of a nonlinear transfinite algebraic transformation and an elliptic transformation. The elliptic transformation is based on the Laplace equations for domains, or on the Laplace-Beltrami equations for surfaces. The algebraic transformation maps the computational space one to-one onto a parameter space. The elliptic transformation maps the parameter space one-to-one onto the domains or surfaces. The composition of these two mapping is a differentiable one-to-one mapping from computational space onto the domains or surfaces and has a nonvanishing Jacobian. This composite mapping defines the grid point distribution in the interior of the domains or surfaces. For domains and minimal surfaces, the composite mapping obeys a nonlinear elliptic Poisson system with control functions completely defined by the algebraic transformation. The solution of the Poisson systems is obtained by Picard iteration and black-box multigrid solvers. For parametrized curved surfaces, it is not necessary to define and solve a nonlinear elliptic Poisson system. Instead a linear elliptic system and an inversion problem is solved to generate the grid in the interior of the surface.
Algebraic surface grid generation in three-dimensional space
Warsi, Saif
1992-01-01
An interactive program for algebraic generation of structured surface grids in three dimensional space was developed on the IRIS4D series workstations. Interactive tools are available to ease construction of edge curves and surfaces in 3-D space. Addition, removal, or redistribution of points at arbitrary locations on a general 3-D surface or curve is possible. Also, redistribution of surface grid points may be accomplished through use of conventional surface splines or a method called 'surface constrained transfinite interpolation'. This method allows the user to redistribute the grid points on the edges of a surface patch; the effect of the redistribution is then propagated to the remainder of the surface through a transfinite interpolation procedure where the grid points will be constrained to lie on the surface. The program was written to be highly functional and easy to use. A host of utilities are available to ease the grid generation process. Generality of the program allows the creation of single and multizonal surface grids according to the user requirements. The program communicates with the user through popup menus, windows, and the mouse.
Grid Monitoring and Advanced Control of Distributed Power Generation Systems
Timbus, Adrian Vasile
2007-01-01
The movement towards a clean technology for energy production and the constraints in reducing the CO2 emissions are some factors facilitating the growth of distributed power generation systems based on renewable energy resources. Consequently, large penetration of distributed generators has been 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...
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)
Homogeneous Turbulence Generated by Multi-scale Grids
Energy Technology Data Exchange (ETDEWEB)
Krogstad, Per-Age [Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Davidson, Peter, E-mail: per.a.krogstad@ntnu.no [University of Cambridge, Cambridge CB2 1PZ (United Kingdom)
2011-12-22
We investigate wind tunnel turbulence generated by a conventional and two multi-scale grids. The conventional and multi-scale grids were all designed to produce turbulence with the same integral scale, so that a direct comparison could be made between the different flows. The decay of the turbulent energy was mapped in detail from a distance from the grid less than one mesh width, down to distances of the order of 200 meshes using a combination of laser doppler and hot wire anemometry tools. The turbulent decay rate behind our multi-scale grids was found to be virtually identical to that behind the equivalent conventional grid after the initial transition had been completed. In particular, all flows exhibit a power-law decay of energy, u{sup 2} {approx} t{sup -n}, where n is very close to the classical Saffman exponent of n = 6/5 in the far field. Our results are at odds with some other experiments performed on multi-scale grids, where significantly higher energy decay exponents have been reported.
Column generation based planning in smart grids using TRIANA
Toersche, Hermen; Molderink, Albert; Hurink, Johann L.; Smit, Gerardus Johannes Maria
2013-01-01
Column generation is applied to the TRIANA smart grid framework's planner and combined with distributed dynamic programming. Simulations show that this improves the resulting planning compared to methods described in previous work (extra peak reduction of 7.3%; large fluctuation reduction) at the
The Next-Generation Power Electronics Technology for Smart Grids
Akagi, Hirofumi
This paper presents an overview of the next-generation power electronics technology for the Japanese-version smart grid. It focuses on a grid-level battery energy storage system, a grid-level STATCOM (STATic synchronous COMpensator), and a 6.6-kV BTB (Back-To-Back) system for power flow control between two power distribution feeders. These power electronic devices play an important role in achieving load frequency control and voltage regulation. Their circuit configurations based on modular multilevel cascade PWM converters are characterized by flexible system design, low voltage steps, and low EMI (Electro-Magnetic Interference) emission. Their downscaled laboratory models are designed, constructed, and tested to verify the viability and effectiveness of the circuit configurations and control methods.
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
Eggs illusion: Local shape deformation generated by a grid pattern.
Qian, Kun; Mitsudo, Hiroyuki
2016-12-01
In this study, we report a new visual shape illusion, the eggs illusion, in which circular disks located at the midpoints between adjacent grid intersections are perceived as being deformed to ellipses. In Experiment 1, we examined the eggs illusion by using a matching method and found that grid luminance and patch size play a critical role in producing the illusory deformation. In Experiment 2, we employed several types of elliptic or circular patches to examine the conditions in which the illusory deformation was cancelled or weakened. We observed that the illusory deformation was dependent on local grid orientation. Based on these results, we found several common features between the eggs illusion and the scintillating grid illusion. This resemblance suggests a possibility that similar mechanisms underlie the two phenomena. In addition to the scintillating grid illusion, we also considered several known perceptual phenomena that might be related to the eggs illusion, i.e., the apparent size illusion, the shape-contrast effect, and the Orbison illusion. Finally, we discuss the role of orientation processing in generating the eggs illusion.
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper presents new weighting functions in grid generation and new discretizing scheme of momentum equations in numerical simulation of river flow. By using the new weighting functions, the curvilinear grid could be concentrated as desired near the assigned points or lines in physical plane. By using the new discretizing scheme, the difficulties caused by movable boundary and dry riverbed can be overcome. As an application, the flow in the Wuhan Section of Yangtze River is simulated. The computational results are in good agreement with the measured results. The new method is applicable to the numerical simulation of 2-D river flow with irregular region and moveable boundary.
Vortex shedding effects in grid-generated turbulence
Melina, G.; Bruce, P. J. K.; Vassilicos, J. C.
2016-08-01
The flow on the centerline of grid-generated turbulence is characterized via hot-wire anemometry for three grids with different geometry: a regular grid (RG60), a fractal grid (FSG17), and a single-square grid (SSG). Due to a higher value of the thickness t0 of its bars, SSG produces greater values of turbulence intensity Tu than FSG17, despite SSG having a smaller blockage ratio. However, the higher Tu for SSG is mainly due to a more pronounced vortex shedding contribution. The effects of vortex shedding suppression along the streamwise direction x are studied by testing a three-dimensional configuration, formed by SSG and a set of four splitter plates detached from the grid (SSG+SP). When vortex shedding is damped, the centerline location of the peak of turbulence intensity xpeak moves downstream and Tu considerably decreases in the production region. For FSG17 the vortex shedding is less intense and it disappears more quickly, in terms of x /xpeak , when compared to all the other configurations. When vortex shedding is attenuated, the integral length scale Lu grows more slowly in the streamwise direction, this being verified both for FSG17 and for SSG+SP. In the production region, there is a correlation between the vortex shedding energy and the skewness and the flatness of the velocity fluctuations. When vortex shedding is not significant, the skewness is highly negative and the flatness is much larger than 3. On the opposite side, when vortex shedding is prominent, the non-Gaussian behavior of the velocity fluctuations becomes masked.
Atmospheric wind field conditions generated by active grids
Knebel, Pascal; Kittel, Achim; Peinke, Joachim
2011-08-01
An active grid for turbulence generation of several rotatable axes with surmounted vanes that can be driven via stepper or servo motors is presented. We investigate the impact of different excitation protocols for the grid. Using such protocols that already have the intermittent structure of turbulence, higher intermittent flows can be achieved. This concept can also be used to generate turbulent flows of high turbulence intensities (>25%) exhibiting integral length scales beyond the typical size of the test section of the wind tunnel. Similar two-point correlations measured by the intermittent statistics of velocity increments that are characteristic for flows of high Reynolds number, i.e. in the atmospheric boundary layer, can be reproduced.
Numerical Grid Generation and Potential Airfoil Analysis and Design
1988-01-01
field vectors tangent to the coordinate curve passing across these surfaces. The most common form is transfinite interpolation, which is es- sentially an...interpolation between curves or surfaces rather than points. It is called " transfinite " because it matches coordinate values on an entire curve or...surface. For example, Erikson [5] applies transfinite interpolation for three -dimensional grid generation about wing - body configurations. Some
Interfacing a small thermophotovoltaic generator to the grid
Durisch, W.; Grob, B.; Mayor, J.-C.; Panitz, J.-C.; Rosselet, A.
1999-03-01
A prototype thermophotovoltaic generator and grid-interfacing device have been developed to demonstrate the feasibility of grid-connected operation. For this purpose a conventional butane burner (rated power 1.35 kWth) was equipped with a ceramic composite emitter made of rare earth oxides. A water layer between emitter and photocells was used to protect the photocells against overheating. It absorbs the nonconvertible emitter radiation and is heated up thereby. The hot water so produced in larger units of this type could be used in a primary recirculation loop to transfer heat to a secondary domestic hot water system. For the photovoltaic generator, commercial grade silicon solar cells with 16% efficiency (under standard test conditions) were used. With the radiation of the emitter, a current of 4.6 A at a maximum power point voltage of 3.3 V was produced, corresponding to a DC output of 15 W and a thermal to DC power conversion efficiency of 1.1%. A specially developed high efficiency DC/DC converter and a modified, commercially available inverter were used to feed the generated power to the local grid. Under the experimental conditions in question the DC/DC-converter and the grid-inverter had efficiencies of 98 and 91%, respectively resulting in an overall interface efficiency of 89%. From modeling of the measured electrical characteristics of the photo cell generator under solar and emitter radiation, it is concluded that the photo current was about three times higher under the filtered emitter radiation. Under these conditions the electrical losses of the photocells were significantly higher than under sunlight.
A finite volume method for numerical grid generation
Beale, S. B.
1999-07-01
A novel method to generate body-fitted grids based on the direct solution for three scalar functions is derived. The solution for scalar variables , and is obtained with a conventional finite volume method based on a physical space formulation. The grid is adapted or re-zoned to eliminate the residual error between the current solution and the desired solution, by means of an implicit grid-correction procedure. The scalar variables are re-mapped and the process is reiterated until convergence is obtained. Calculations are performed for a variety of problems by assuming combined Dirichlet-Neumann and pure Dirichlet boundary conditions involving the use of transcendental control functions, as well as functions designed to effect grid control automatically on the basis of boundary values. The use of dimensional analysis to build stable exponential functions and other control functions is demonstrated. Automatic procedures are implemented: one based on a finite difference approximation to the Cristoffel terms assuming local-boundary orthogonality, and another designed to procure boundary orthogonality. The performance of the new scheme is shown to be comparable with that of conventional inverse methods when calculations are performed on benchmark problems through the application of point-by-point and whole-field solution schemes. Advantages and disadvantages of the present method are critically appraised. Copyright
Three Dimensional Grid Generation for Complex Configurations - Recent Progress
1988-03-01
component. For example, a locally embedded C grid around a w.,, - rntinued outboard of the tip where it is constructed around an imaginary extension of...structure in the field topology and the inserts show the locally embedded C grids around the wing and canard. Figure 9 illustrates the effect of grid point...nature of the grid is evident with locally embedded C grids around the wing and canard and a polar grid around the body. The grid point distribution in
Grid: A next generation data parallel C++ QCD library
Boyle, Peter; Cossu, Guido; Portelli, Antonin
2015-01-01
In this proceedings we discuss the motivation, implementation details, and performance of a new physics code base called Grid. It is intended to be more performant, more general, but similar in spirit to QDP++\\cite{QDP}. Our approach is to engineer the basic type system to be consistently fast, rather than bolt on a few optimised routines, and we are attempt to write all our optimised routines directly in the Grid framework. It is hoped this will deliver best known practice performance across the next generation of supercomputers, which will provide programming challenges to traditional scalar codes. We illustrate the programming patterns used to implement our goals, and advances in productivity that have been enabled by using new features in C++11.
Adaptive Grid Generation Using Elliptic Generating Equations with Precise Coordinate Controls
1986-07-08
Sciences Meeting, 6-9 January 1986,. Reno, NV. Abstract not available. V COMMUNICATIONS IN APPLIED NUMERICAL METHODS . Vol. 4, 471-481 (1988) ON THE...COMMUNICATIONS IN APPLIED NUMERICAL METHODS , Vol. 7, 345-354 (1991) HYBRID ADAPTIVE POISSON GRID GENERATION AND GRID SMOOTHNESS PATRICK J. ROACHE, KAMBIZ...U.S.A. 0045-7825/90/S3.50 @ 1990. Elsevier Science Publishers By. (North-Holland) Atcepted for publication in Communications in Applied Numerical Methods . COMPLETED
Three-dimensional grid generation about a submarine
Abolhassani, Jamshid Samareh; Smith, Robert E.
1988-01-01
A systematic multiple-block grid method has been developed to compute grids about submarines. Several topologies are proposed, and an oscillatory transfinite interpolation is used in the grid construction.
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...
Grid generation and flow computation about a Martian entry vehicle
Stewart, J. E.; Tiwari, S. N.
1990-01-01
A number of vehicles are currently being proposed for a manned mission to Mars. One of these vehicles has a modified blunt-nosed cone configuration. Experimental results were obtained for this vehicle in 1968. They show lift-over-drag ratios comparable to those needed for Mars entry. Computations are performed to verify the earlier results and to further describe the flight characteristics of this vehicle. An analytical method is used to define the surface of this vehicle. A single-block volume grid is generated around the vehicle using the algebraic Two-Boundary Grid Generation algorithm (TBGG) and transfinite interpolation. Euler solutions are then obtained from a Langley Aerodynamic Upward Relaxation Algorithm (LAURA) at Mach 6.0 and angles of attack of 0, 6, and 12 deg. The lift coefficient determined from the LAURA code agree very well with the experimental results. The drag and pitching moment coefficients, however, are underestimated by the code since viscous effects are not considered. Contour plots of the flowfield show no evidence of separation for angles of attack up to 12 deg.
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...
Oscillating grids turbulence generator for turbulent transport studies
Directory of Open Access Journals (Sweden)
A. Eidelman
2002-01-01
Full Text Available An oscillating grids turbulence generator was constructed for studies of two new effects associated with turbulent transport of particles, turbulent thermal diffusion and clustering instability. These effects result in formation of large-scale and small-scale inhomogeneities in the spatial distribution of particles. The advantage of this experimental set-up is the feasibility to study turbulent transport in mixtures with controllable composition and unlimited observation time. For flow measurements we used Particle Image Velocimetry with the adaptive multi-pass algorithm to determine a turbulent velocity field and its statistical characteristics. Instantaneous velocity vector maps, flow streamlines and probability density function of velocity field demonstrate properties of turbulence generated in the device.
Parallel and Streaming Generation of Ghost Data for Structured Grids
Energy Technology Data Exchange (ETDEWEB)
Isenburg, M; Lindstrom, P; Childs, H
2008-04-15
Parallel simulations decompose large domains into many blocks. A fundamental requirement for subsequent parallel analysis and visualization is the presence of ghost data that supplements each block with a layer of adjacent data elements from neighboring blocks. The standard approach for generating ghost data requires all blocks to be in memory at once. This becomes impractical when there are fewer processors - and thus less aggregate memory - available for analysis than for simulation. We describe an algorithm for generating ghost data for structured grids that uses many fewer processors than previously possible. Our algorithm stores as little as one block per processor in memory and can run on as few processors as are available (possibly just one). The key idea is to slightly change the size of the original blocks by declaring parts of them to be ghost data, and by later padding adjacent blocks with this data.
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
Shih, T. I.-P.; Bailey, R. T.; Nguyen, H. L.; Roelke, R. J.
1990-01-01
An efficient computer program, called GRID2D/3D was developed to generate single and composite grid systems within geometrically complex two- and three-dimensional (2- and 3-D) spatial domains that can deform with time. GRID2D/3D generates single grid systems by using algebraic grid generation methods based on transfinite interpolation in which the distribution of grid points within the spatial domain is controlled by stretching functions. All single grid systems generated by GRID2D/3D can have grid lines that are continuous and differentiable everywhere up to the second-order. Also, grid lines can intersect boundaries of the spatial domain orthogonally. GRID2D/3D generates composite grid systems by patching together two or more single grid systems. The patching can be discontinuous or continuous. For continuous composite grid systems, the grid lines are continuous and differentiable everywhere up to the second-order except at interfaces where different single grid systems meet. At interfaces where different single grid systems meet, the grid lines are only differentiable up to the first-order. For 2-D spatial domains, the boundary curves are described by using either cubic or tension spline interpolation. For 3-D spatial domains, the boundary surfaces are described by using either linear Coon's interpolation, bi-hyperbolic spline interpolation, or a new technique referred to as 3-D bi-directional Hermite interpolation. Since grid systems generated by algebraic methods can have grid lines that overlap one another, GRID2D/3D contains a graphics package for evaluating the grid systems generated. With the graphics package, the user can generate grid systems in an interactive manner with the grid generation part of GRID2D/3D. GRID2D/3D is written in FORTRAN 77 and can be run on any IBM PC, XT, or AT compatible computer. In order to use GRID2D/3D on workstations or mainframe computers, some minor modifications must be made in the graphics part of the program; no
Automatic Mesh Generation on a Regular Background Grid
Institute of Scientific and Technical Information of China (English)
LO S.H; 刘剑飞
2002-01-01
This paper presents an automatic mesh generation procedure on a 2D domainbased on a regular background grid. The idea is to devise a robust mesh generation schemewith equal emphasis on quality and efficiency. Instead of using a traditional regular rectangulargrid, a mesh of equilateral triangles is employed to ensure triangular element of the best qualitywill be preserved in the interior of the domain.As for the boundary, it is to be generated by a node/segment insertion process. Nodes areinserted into the background mesh one by one following the sequence of the domain boundary.The local structure of the mesh is modified based on the Delaunay criterion with the introduc-tion of each node. Those boundary segments, which are not produced in the phase of nodeinsertion, will be recovered through a systematic element swap process. Two theorems will bepresented and proved to set up the theoretical basic of the boundary recovery part. Exampleswill be presented to demonstrate the robustness and the quality of the mesh generated by theproposed technique.
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...... the current ratings of the converter is introduced. Moreover, a novel flexible algorithm has been proposed in order to regulate easily the injection of positive and negative currents for general purpose applications....
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...
Enhancement of turbulent flame speed of V-shaped flames in fractal-grid-generated turbulence
Verbeek, A.A.; Willems, P.A.; Stoffels, G.G.M.; Geurts, B.J.; Meer, van der T.H.
2016-01-01
A variety of fractal grids is used to investigate how fractal-grid-generated turbulence affects the turbulent flame speed for premixed flames. The grids are placed inside a rectangular duct and a V-shaped flame is stabilized downstream of the duct, using a metal wire. This flame is characterized usi
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
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......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...... 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 (SGT......) 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....
On the applications of algebraic grid generation methods based on transfinite interpolation
Nguyen, Hung Lee
1989-01-01
Algebraic grid generation methods based on transfinite interpolation called the two-boundary and four-boundary methods are applied for generating grids with highly complex boundaries. These methods yield grid point distributions that allow for accurate application to regions of sharp gradients in the physical domain or time-dependent problems with small length scale phenomena. Algebraic grids are derived using the two-boundary and four-boundary methods for applications in both two- and three-dimensional domains. Grids are developed for distinctly different geometrical problems and the two-boundary and four-boundary methods are demonstrated to be applicable to a wide class of geometries.
Specialized CFD Grid Generation Methods for Near-Field Sonic Boom Prediction
Park, Michael A.; Campbell, Richard L.; Elmiligui, Alaa; Cliff, Susan E.; Nayani, Sudheer N.
2014-01-01
Ongoing interest in analysis and design of low sonic boom supersonic transports re- quires accurate and ecient Computational Fluid Dynamics (CFD) tools. Specialized grid generation techniques are employed to predict near- eld acoustic signatures of these con- gurations. A fundamental examination of grid properties is performed including grid alignment with ow characteristics and element type. The issues a ecting the robustness of cylindrical surface extrusion are illustrated. This study will compare three methods in the extrusion family of grid generation methods that produce grids aligned with the freestream Mach angle. These methods are applied to con gurations from the First AIAA Sonic Boom Prediction Workshop.
Nakamura, S.
1982-01-01
A fast method for generating three-dimensional grids for fuselage-wing transonic flow calculations using parabolic difference equations is described. No iterative scheme is used in the three-dimensional sense; grids are generated from one grid surface to the next starting from the fuselage surface. The computational procedure is similar to the iterative solution of the two-dimensional heat conduction equation. The proposed method is at least 10 times faster than the elliptic grid generation method and has much smaller memory requirements. Results are presented for a fuselage and wing of NACA-0012 section and thickness ratio of 10 percent. Although only H-grids are demonstrated, the present technique should be applicable to C-grids and O-grids in three dimensions.
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
A mathematical basis for automated structured grid generation with close coupling to the flow solver
Energy Technology Data Exchange (ETDEWEB)
Barnette, D.W.
1998-02-01
The first two truncation error terms resulting from finite differencing the convection terms in the two-dimensional Navier-Stokes equations are examined for the purpose of constructing two-dimensional grid generation schemes. These schemes are constructed such that the resulting grid distributions drive the error terms to zero. Two sets of equations result, one for each error term, that show promise in generating grids that provide more accurate flow solutions and possibly faster convergence. One set results in an algebraic scheme that drives the first truncation term to zero, and the other a hyperbolic scheme that drives the second term to zero. Also discussed is the possibility of using the schemes in sequentially constructing a grid in an iterative algorithm involving the flow solver. In essence, the process is envisioned to generate not only a flow field solution but the grid as well, rendering the approach a hands-off method for grid generation
DEFF Research Database (Denmark)
Zhu, Rongwu; Chen, Zhe; Wu, Xiaojie
2015-01-01
For the grid-connected doubly-fed induction generator (DFIG)-based wind turbine, because of the stator connected to the grid directly, the stator flux easily suffers from the effects of grid voltage variations, such as grid disturbances and grid faults. Moreover, since the magnetic field is excited...... by the rotor current, stator flux is also affected by the rotor current. Therefore this study systematically studies the dynamic performances of stator flux under consecutive grid voltage variations and varying rotor currents, and its influence on the performances of the DFIG during grid faults. The analyses...... reveal that the stator flux can be accumulated by the consecutive variations of the stator voltage, and the instants of grid voltage variations can lead to different amplitudes of the stator flux. In addition, the conventional vector control strategy and the active damping strategy are compared...
Automated grid generation from models of complex geologic structure and stratigraphy
Energy Technology Data Exchange (ETDEWEB)
Gable, C.; Trease, H.; Cherry, T.
1996-04-01
The construction of computational grids which accurately reflect complex geologic structure and stratigraphy for flow and transport models poses a formidable task. With an understanding of stratigraphy, material properties and boundary and initial conditions, the task of incorporating this data into a numerical model can be difficult and time consuming. Most GIS tools for representing complex geologic volumes and surfaces are not designed for producing optimal grids for flow and transport computation. We have developed a tool, GEOMESH, for generating finite element grids that maintain the geometric integrity of input volumes, surfaces, and geologic data and produce an optimal (Delaunay) tetrahedral grid that can be used for flow and transport computations. GEOMESH also satisfies the constraint that the geometric coupling coefficients of the grid are positive for all elements. GEOMESH generates grids for two dimensional cross sections, three dimensional regional models, represents faults and fractures, and has the capability of including finer grids representing tunnels and well bores into grids. GEOMESH also permits adaptive grid refinement in three dimensions. The tools to glue, merge and insert grids together demonstrate how complex grids can be built from simpler pieces. The resulting grid can be utilized by unstructured finite element or integrated finite difference computational physics codes.
Grid Monitoring and Advanced Control of Distributed Power Generation Systems
DEFF Research Database (Denmark)
Timbus, Adrian Vasile
. First part of the thesis investigates possible algorithms for fast and accurate identi cation of utility network variables such as voltage amplitude, frequency, phase angle and line impedance. Special attention has been paid to grid synchronization algorithm in terms of accurate estimation of grid...... of grid voltage and the frequency of utility network. As a result, fast and accurate identi cation of both variables has been achieved. In addition, positive and negative sequence components of grid voltage can also be calculated. Simple, yet powerful ltering techniques, based on second order generalized...... integrator (SOGI) and delay signal cancellation (DSC) have been used to separate the sequence components. Simulation and experimental results attest the accuracy and e ectiveness of the developed algorithms in identifying the frequency, phase angle and magnitude of grid voltages during severe distortions...
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...... such as heat pumps, requirements of the transmission grid are lowered thereby reducing or eliminating needs of grid reinforcement. It is important that load balance is kept at local level and not just at an aggregate level....
Multi-block and path modelling procedures
DEFF Research Database (Denmark)
Høskuldsson, Agnar
2008-01-01
The author has developed a unified theory of path and multi-block modelling of data. The data blocks are arranged in a directional path. Each data block can lead to one or more data blocks. It is assumed that there is given a collection of input data blocks. Each of them is supposed to describe one...
Geometry modeling and grid generation using 3D NURBS control volume
Yu, Tzu-Yi; Soni, Bharat K.; Shih, Ming-Hsin
1995-01-01
The algorithms for volume grid generation using NURBS geometric representation are presented. The parameterization algorithm is enhanced to yield a desired physical distribution on the curve, surface and volume. This approach bridges the gap between CAD surface/volume definition and surface/volume grid generation. Computational examples associated with practical configurations have shown the utilization of these algorithms.
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...
Grid generation and compressible flow computations about a high-speed civil transport configuration
Abolhassani, J. S.; Stewart, J. E.; Farr, N.; Smith, R. E.; Kerr, P. W.; Everton, E. L.
1991-01-01
Techniques and software are discussed for generating grids about a high-speed civil transport configuration. The configuration is defined by a computer-aided design system in wing, fuselage, tail and engine-nacelle components. Grid topology and the surfaces outlining the blocks of the topology are computed with interactive software. The volume grid is computed using software based on transfinite interpolation and Lagrangian blending functions. Several volume grids for inviscid and viscous flow have been generated using this system of codes. Demonstration flowfields around this vehicle are described.
Directory of Open Access Journals (Sweden)
Do Nguyet Quang
2014-02-01
Full Text Available In smart grid communication implementation, network traffic pattern is one of the main factors that affect the system’s performance. Examining different traffic patterns in smart grid is therefore crucial when analyzing the network performance. Due to the heterogeneous and hybrid nature of smart grid, the type of traffic distribution in the network is still unknown. The traffic that popularly used for simulation and analysis no longer reflects the real traffic in a multi-technology and bi-directional communication system. Hence, in this study, a single-board computer is implemented as a traffic generator which can generate network traffic similar to those generated by various applications in the fully operational smart grid. By placing in a strategic and appropriate position, a collection of traffic generators allow network administrators to investigate and test the effect of heavy traffic on performance of smart grid communication system.
Combining multiblock and detailed fluid flow models (LOVI) - MASIT17
Energy Technology Data Exchange (ETDEWEB)
Alopaeus, V.; Moilanen, P.; Visuri, O.; Laakkonen, M.; Aittamaa, J. (Helsinki University of Technology, Faculty of Chemistry and Materials Sciences, Department of Biotechnology and Chemical Technology, Espoo (Finland)); Heiskanen, K.; Wierink, G. (Helsinki University of Technology, Faculty of Chemistry and Materials Sciences, Department of Materials Science and Engineering, Espoo (Finland)); Manninen, M.; Seppaelae, M. (VTT Technical Research Centre of Finland, Espoo (Finland))
2008-07-01
The goal of this research project is to develop models for scale-up, design and operation of heterogeneous reactors. By computing a detailed fluid flow field and using it in a multiblock-model the computing times can be kept reasonable. Our modelling is based on phenomenological models verified on experimental results. Several experimental apparatuses have been used to study gas-liquid flow (tapered channel, 14/200dm3 stirred vessels and the 'giraffe') and bubble-particle interactions. A particle imaging velocimetry (PIV) apparatus is being purchased during 2008 to study fluid flow fields. There has been extensive experimental activity. During this project phenomenological models have been verified, numerical methods for the calculation of population balances have been improved, a novel local mixing time analysis method has been developed and automated multiblock generation algorithms have been developed. A method of evaluating CFD results with a single glance with a two-block model has been introduced. Fermentation process of Galilaeus and the flotation cell of Outotec have been modelled. (orig.)
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.......5-MW DFIG model and by experiments on a 30-kW DFIG test system....
Performance Of Microturbine Generation System in Grid Connected and Islanding Modes of Operation
Gaonkar, Dattatraya N.
2010-01-01
The Distributed generation based on microturbine technology is new and a fast growing business. These DG systems are quickly becoming an energy management solution that saves money, resources, and environment in one compact and scalable package- be it stationary or mobile, remote or interconnected with the utility grid. In this thesis the MTG system model suitable for grid connected and islanding operation has been presented.The detailed modeling of a single-shaft MTG system suitable for grid...
Gaussian curvature analysis allows for automatic block placement in multi-block hexahedral meshing.
Ramme, Austin J; Shivanna, Kiran H; Magnotta, Vincent A; Grosland, Nicole M
2011-10-01
Musculoskeletal finite element analysis (FEA) has been essential to research in orthopaedic biomechanics. The generation of a volumetric mesh is often the most challenging step in a FEA. Hexahedral meshing tools that are based on a multi-block approach rely on the manual placement of building blocks for their mesh generation scheme. We hypothesise that Gaussian curvature analysis could be used to automatically develop a building block structure for multi-block hexahedral mesh generation. The Automated Building Block Algorithm incorporates principles from differential geometry, combinatorics, statistical analysis and computer science to automatically generate a building block structure to represent a given surface without prior information. We have applied this algorithm to 29 bones of varying geometries and successfully generated a usable mesh in all cases. This work represents a significant advancement in automating the definition of building blocks.
Demand response impacts on off-grid hybrid photovoltaic-diesel generator microgrids
Aaron St. Leger
2015-01-01
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 prope...
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.
Applications of Lagrangian blending functions for grid generation around airplane geometries
Abolhassani, Jamshid S.; Sadrehaghighi, Ideen; Tiwari, Surendra N.; Smith, Robert E.
1990-01-01
A simple procedure has been developed and applied for the grid generation around an airplane geometry. This approach is based on a transfinite interpolation with Lagrangian interpolation for the blending functions. A monotonic rational quadratic spline interpolation has been employed for the grid distributions.
Application of Lagrangian blending functions for grid generation around airplane geometries
Abolhassani, Jamshid S.; Sadrehaghighi, Ideen; Tiwari, Surendra N.
1990-01-01
A simple procedure was developed and applied for the grid generation around an airplane geometry. This approach is based on a transfinite interpolation with Lagrangian interpolation for the blending functions. A monotonic rational quadratic spline interpolation was employed for the grid distributions.
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...
Heskes, P.J.M.
2011-01-01
Today’s Distributed Generators (DG) and load appliances are increasingly build up with power electronics. This trend is expected to grow further in the future. Also developments are ongoing to improve the performance and efficiency of grid components by means of power electronics and several grid co
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.
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
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
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
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
2-D boundary-fitted coordinate grid generation for casting with complex shape
Directory of Open Access Journals (Sweden)
Wang Ye
2013-05-01
Full Text Available In order to overcome the zigzag grids generated by conventional finite difference method on complicated casting boundaries in the simulation of casting process, the generation program for 2-D boundary-fitted coordinate grid has been developed by solving a set of partial differential equations (PDE numerically. The STL format files were treated as input data for 2-D physical regions. The equipartition method for boundary points was used to improve the self-adaptability of grid according to the characteristic of the STL format files. The program was demonstrated through some examples. The comparison between the conventional finite difference method and the proposed method shows that this program is effective and flexible for generation of boundary-fitted grid in any arbitrary 2-D complex domain, and the grid is in accordance with the variety of boundary curvature finely. The program also provides two types of boundary-fitted grids for double-connected region, O-type and C-type. The limitation of the step-like boundary with the rectangle grid could be avoided effectively. Therefore, the computational accuracy and efficiency would be improved and the computational time would be saved significantly by the application of boundary-fitted grids.
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......Ancillary services for distributed generation systems become a challenging issue to smartly integrate renewable energy sources into the grid. Voltage control is one of these ancillary services which can ride through and support the voltage under grid faults. Grid codes from the Transmission System...... 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...
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.
A Parallel Computational Fluid Dynamics Unstructured Grid Generator
1993-12-01
and parallel processing. I had a great deal of help in this effort. I would especially like to thank my advisor, LtCol Hobart, and my committee members...Mathematics Sciences Section at Oak Ridgr ’ -ratory, especially Barry Peyton and Dave MacKay for their help in providing me with their parallel recursive...solvers is due, in part, to the evoluion Of unstructured grids. Problem This research develops a parallel algorithm to create a two-dimensional
Three-dimensional elliptic grid generation with fully automatic boundary constraints
Kaul, Upender K.
2010-08-01
A new procedure for generating smooth uniformly clustered three-dimensional structured elliptic grids is presented here which formulates three-dimensional boundary constraints by extending the two-dimensional counterpart presented by the author earlier. This fully automatic procedure obviates the need for manual specification of decay parameters over the six bounding surfaces of a given volume grid. The procedure has been demonstrated here for the Mars Science Laboratory (MSL) geometries such as aeroshell and canopy, as well as the Inflatable Aerodynamic Decelerator (IAD) geometry and a 3D analytically defined geometry. The new procedure also enables generation of single-block grids for such geometries because the automatic boundary constraints permit the decay parameters to evolve as part of the solution to the elliptic grid system of equations. These decay parameters are no longer just constants, as specified in the conventional approach, but functions of generalized coordinate variables over a given bounding surface. Since these decay functions vary over a given boundary, orthogonal grids around any arbitrary simply-connected boundary can be clustered automatically without having to break up the boundaries and the corresponding interior or exterior domains into various blocks for grid generation. The new boundary constraints are not limited to the simply-connected regions only, but can also be formulated around multiply-connected and isolated regions in the interior. The proposed method is superior to other methods of grid generation such as algebraic and hyperbolic techniques in that the grids obtained here are C2 continuous, whereas simple elliptic smoothing of algebraic or hyperbolic grids to enforce C2 continuity destroys the grid clustering near the boundaries. US patent 7231329.
Algebraic Grid Generation for an Afterbody with Finite Span, Tapered Fins.
1986-10-01
of conformal mapping and transfinite interpolation. The method is an extension of previous work for the generation of a 3-D grid about an afterbody...a combination of conformal mapping and transfinite interpolation. The method is an extension of previous work for the generation of a 3-D grid about...intersection - see Fig. 5 zF fin airfoil thickness - see Fig. 5 F ,r normalized coordinates used in transfinite interpolation I - -~r~nw~t#~JtAJ4Ufwig
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)
Aerodynamic analysis of flapping foils using volume grid deformation code
Energy Technology Data Exchange (ETDEWEB)
Ko, Jin Hwan [Seoul National University, Seoul (Korea, Republic of); Kim, Jee Woong; Park, Soo Hyung; Byun, Do Young [Konkuk University, Seoul (Korea, Republic of)
2009-06-15
Nature-inspired flapping foils have attracted interest for their high thrust efficiency, but the large motions of their boundaries need to be considered. It is challenging to develop robust, efficient grid deformation algorithms appropriate for the large motions in three dimensions. In this paper, a volume grid deformation code is developed based on finite macro-element and transfinite interpolation, which successfully interfaces to a structured multi-block Navier-Stokes code. A suitable condition that generates the macro-elements with efficiency and improves the robustness of grid regularity is presented as well. As demonstrated by an airfoil with various motions related to flapping, the numerical results of aerodynamic forces by the developed method are shown to be in good agreement with those of an experimental data or a previous numerical solution
Elliptic grid generation with orthogonality and spacing control on an arbitrary number of boundaries
White, J. A.
1990-01-01
A procedure for the generation of two and quasi-three-dimensional grids with control of orthogonality and spacing with respect to any and/or all boundaries of the domain is described. The elliptic grid generation equations of Thompson are solved implicitly. Control of the grid behavior is achieved through the introduction of forcing functions terms in the manner of Steger and Sorenson or in a modification of the method of Hilgenstock. The forcing function terms are constructed on the boundaries and propagated into the domain using transfinite Lagrangian bivariate interpolation. An anisotropic transfinite stencil is introduced and is shown to produce excellent grid behavior particularly in the vicinity of corner singularities. Emphasis is placed on the generation of viscous grids and the method is shown to be suited for use in the generation of grids for internal as well as external flow geometries. A FORTRAN program named PISCES has been written to implement the algorithm. Examples of grids for internal and external flows are given that highlight the characteristics and behavior of the algorithm.
Modeling and Stress Analysis of Doubly-Fed Induction Generator during Grid Voltage Swell
DEFF Research Database (Denmark)
Zhou, Dao; Song, Yipeng; Blaabjerg, Frede
2016-01-01
The Doubly-Fed Induction Generator (DFIG) based wind turbine system is presently dominant in the wind turbine market. Due to heavy load switch-off and faults in the power grid, voltage swells may occur and this phenomenon is currently given sufficient insights. This paper starts to describe...... the transient voltage swell and its recovery. It is concluded that although both higher swell level and higher rotor speed cause higher rotor electromotive force, the doubly-fed induction generator can successfully ride through the grid fault due to the relatively small swell level required by the modern grid...
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.
Orthogonal grid generation of an irregular region using a local polynomial collocation method
Wu, Nan-Jing; Tsay, Ting-Kuei; Yang, Tun-Chi; Chang, Hung-Yuan
2013-06-01
In this study, a 2-D orthogonal grid generation model is developed by solving the governing equations of coordinate transformation with a local polynomial collocation method accompanied with the moving least squares (MLS) approach. This method was developed in a way that on the boundaries both the governing equation and boundary condition are satisfied, so it is more robust and accurate than conventional collocation methods. Though the method used to solve the coordinate transforming equations is meshless, it does not deteriorate the value of present work, because most numerical models in modern use are grid-dependent, and grid generation of service to these models is still strongly desired, particularly for finite difference models in irregular domains. Before applying to grid generation problems, the performance of present method is tested by a bench mark potential flow problem. Additional to two basic grid generation problems, a bottleneck problem of previous works, which contains zero-degree corners in the domain, is carried out. Finally, the model is applied to the orthogonal grid generation in a multi-connected domain. The correctness is testified by checking the orthogonality of the generated results.
Inrush Current Limitation in Wind Generators by SCR Based Soft-starter during grid connection
Directory of Open Access Journals (Sweden)
Sanjay Mishra
2013-10-01
Full Text Available High Inrush current & harmonics is a generic problem wind generators during grid connection.The designed SCR based soft-starter successfully limits the high inrush current during the connection of the wind-turbine system to the grid. The proposed SCR based soft starter using will be simulating in PSCAD on a three-phase induction generator. Expected results will show a significant reduction in high inrush current and smooth connection of the three phase induction generator to the grid with small impact on the power quality. A small-scale wind turbine coupled three phase induction generator is an attractive choice for an isolated grid hybrid power system in remote areas because of its low cost, compactness, ruggedness, high reliability, low inertia and ease in control. In this work, a SCR based soft starter for limiting the high inrush current during the connection of the small-scale wind turbine coupled three phase induction generator to an isolated weak grid has been proposed. Soft-starter is designed to reduce inrush current or surge in current while achieving a proper synchronism between the generator and the grid.
How to perform multiblock component analysis in practice
De Roover, Kim; Ceulemans, Eva; Timmerman, Marieke E.
To explore structural differences and similarities in multivariate multiblock data (e.g., a number of variables have been measured for different groups of subjects, where the data for each group constitute a different data block), researchers have a variety of multiblock component analysis and
Multi-resolution unstructured grid-generation for geophysical applications on the sphere
Engwirda, Darren
2015-01-01
An algorithm for the generation of non-uniform unstructured grids on ellipsoidal geometries is described. This technique is designed to generate high quality triangular and polygonal meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric and ocean simulation, and numerical weather predication. Using a recently developed Frontal-Delaunay-refinement technique, a method for the construction of high-quality unstructured ellipsoidal Delaunay triangulations is introduced. A dual polygonal grid, derived from the associated Voronoi diagram, is also optionally generated as a by-product. Compared to existing techniques, it is shown that the Frontal-Delaunay approach typically produces grids with near-optimal element quality and smooth grading characteristics, while imposing relatively low computational expense. Initial results are presented for a selection of uniform and non-uniform ellipsoidal grids appropriate for large-scale geophysical applications. The use of user...
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.
An automatic grid generation approach over free-form surface for architectural design
Institute of Scientific and Technical Information of China (English)
苏亮; 祝顺来; 肖南; 高博青
2014-01-01
An essential step for the realization of free-form surface structures is to create an efficient structural gird that satisfies not only the architectural aesthetics, but also the structural performance. Employing the main stress trajectories as the representation of force flows on a free-form surface, an automatic grid generation approach is proposed for the architectural design. The algorithm automatically plots the main stress trajectories on a 3D free-form surface, and adopts a modified advancing front meshing technique to generate the structural grid. Based on the proposed algorithm, an automatic grid generator named “St-Surmesh” is developed for the practical architectural design of free-form surface structure. The surface geometry of one of the Sun Valleys in Expo Axis for the Expo Shanghai 2010 is selected as a numerical example for validating the proposed approach. Comparative studies are performed to demonstrate how different structural grids affect the design of a free-form surface structure.
DEFF Research Database (Denmark)
Hansen, Anca Daniela; Michalke, G.
2009-01-01
. 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......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...
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.
Message passing for integrating and assessing renewable generation in a redundant power grid
Energy Technology Data Exchange (ETDEWEB)
Zdeborova, Lenka [Los Alamos National Laboratory; Backhaus, Scott [Los Alamos National Laboratory; Chertkov, Michael [Los Alamos National Laboratory
2009-01-01
A simplified model of a redundant power grid is used to study integration of fluctuating renewable generation. The grid consists of large number of generator and consumer nodes. The net power consumption is determined by the difference between the gross consumption and the level of renewable generation. The gross consumption is drawn from a narrow distribution representing the predictability of aggregated loads, and we consider two different distributions representing wind and solar resources. Each generator is connected to D consumers, and redundancy is built in by connecting R {le} D of these consumers to other generators. The lines are switchable so that at any instance each consumer is connected to a single generator. We explore the capacity of the renewable generation by determining the level of 'firm' generation capacity that can be displaced for different levels of redundancy R. We also develop message-passing control algorithm for finding switch sellings where no generator is overloaded.
Message passing for integrating and assessing renewable generation in a redundant power grid
Energy Technology Data Exchange (ETDEWEB)
Zdeborova, Lenka [Los Alamos National Laboratory; Backhaus, Scott [Los Alamos National Laboratory; Chertkov, Michael [Los Alamos National Laboratory
2009-01-01
A simplified model of a redundant power grid is used to study integration of fluctuating renewable generation. The grid consists of large number of generator and consumer nodes. The net power consumption is determined by the difference between the gross consumption and the level of renewable generation. The gross consumption is drawn from a narrow distribution representing the predictability of aggregated loads, and we consider two different distributions representing wind and solar resources. Each generator is connected to D consumers, and redundancy is built in by connecting R {le} D of these consumers to other generators. The lines are switchable so that at any instance each consumer is connected to a single generator. We explore the capacity of the renewable generation by determining the level of 'firm' generation capacity that can be displaced for different levels of redundancy R. We also develop message-passing control algorithm for finding switch sellings where no generator is overloaded.
DEFF Research Database (Denmark)
Høskuldsson, Agnar; Svinning, K.
2006-01-01
Here is presented a unified approach to modelling multi-block regression data. The starting point is a partition of the data X into L data blocks, X = (X-1, X-2,...X-L), and the data Y into M data-blocks, Y = (Y-1, Y-2,...,Y-M). The methods of linear regression, X -> Y, are extended to the case...... these methods can be extended to a network of data blocks. Examples of the optimisation procedures in a network are shown. The examples chosen are the ones that are useful to work within industrial production environments. The methods are illustrated by simulated data and data from cement production....
A 3-D grid generation method by an algebraic homotopy technique
Energy Technology Data Exchange (ETDEWEB)
Chew, S.C.; Tsai, H.M. [Defence Science Organization (Singapore)
1996-12-31
A generalized form of the algebraic homotype procedure to generate 3-D grids is described. The formulation by-passes some of the difficulties encountered in the 2-D and quasi 3-D version as previously proposed. As an extension to the technique to ensure grid orthogonality, an approach akin to the advancing front method is used. However, since the procedure is derived from homotopic relations for blending between inner and outer boundaries, the generated grids will match the initially specified outer boundaries. The inherent weaknesses of the homotopic method due to its completely localized nature are also addressed. Overall the present procedure gives the user further control of orthogonality and clustering over the popular transfinite interpolation technique. The rapidity and generality of the technique makes the scheme effective. Grid examples are presented to illustrate the capability and versatility of the method.
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
Islanding operation of distribution systems with distributed generations (DG) is becoming a viable option for economical and technical reasons. However, there are various issues to be resolved before it can be a reality. One of the main issues is control of the DG. Control strategies, that may work...... 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....... Separate strategies are used to control the GTG while it is connected to the grid and while it is islanded. Switching between the control strategies is achieved through a state detection algorithm that includes islanding and grid re-connection detections. An existing islanding detection technique has been...
Elliptic Grid Generation of Spiral-Bevel Pinion Gear Typical of OH-58 Helicopter Transmission
Kaul, Upender K.; Huff, Edward M.
2002-01-01
This paper discusses the source term treatment in the numerical solution of elliptic partial differential equations for an interior grid generation problem in generalized curvilinear coordinates. The geometry considered is that of a planar cross-section of a generic spiral-bevel gear tooth typical of a pinion in the OH-58 helicopter transmission. The source terms used are appropriate for an interior grid domain where all the boundaries are prescribed via a combination of Dirichlet and Neumann boundary conditions. New constraints based on the Green's Theorem are derived which uniquely determine the coefficients in the source terms. These constraints are designed for boundary clustered grids where gradients in physical quantities need to be resolved adequately. However, it is seen that the present formulation works satisfactorily for mild clustering also. Thus, a fully automated elliptic grid generation technique is made possible where there is no need for a parametric study of these parameters since the new relations fix these free parameters uniquely.
Generalized Monge-Kantorovich optimization for grid generation and adaptation in LP
Energy Technology Data Exchange (ETDEWEB)
Delzanno, G L [Los Alamos National Laboratory; Finn, J M [Los Alamos National Laboratory
2009-01-01
The Monge-Kantorovich grid generation and adaptation scheme of is generalized from a variational principle based on L{sub 2} to a variational principle based on L{sub p}. A generalized Monge-Ampere (MA) equation is derived and its properties are discussed. Results for p > 1 are obtained and compared in terms of the quality of the resulting grid. We conclude that for the grid generation application, the formulation based on L{sub p} for p close to unity leads to serious problems associated with the boundary. Results for 1.5 {approx}< p {approx}< 2.5 are quite good, but there is a fairly narrow range around p = 2 where the results are close to optimal with respect to grid distortion. Furthermore, the Newton-Krylov methods used to solve the generalized MA equation perform best for p = 2.
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......) control. In order to improve control performance of the overall system, electromagnetic power and active power oscillations elimination strategies are proposed respectively. Lastly, the effective of the proposed control strategy is verified by the simulation results of a 2 MW DFIG system....
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...
Design, Digital Control, and Simulation of a Grid-Connected Photovoltaic Generation System
Feshara, Hazem; Elharony, Mohamed; Sharaf, Soliman
2016-01-01
This paper presents simulation and digital control of a three-phase grid-connected photovoltaic (PV) generation system. The technique used for maximum power point tracking (MPPT) of photovoltaic power is sliding mode (SM) control. Control of power extraction from DC link capacitor is presented. Space vector pulse width modulation (SVPWM) inverter is utilized to deliver power to utility grid. Simulation is performed using PLECS standalone software package and simulation results are shown. Comp...
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......Islands and rural areas can decrease their cost of energy by exploiting renewable energy as compared to diesel- only generation. Operation of such isolated micro-grids requires allocation of units for grid stability. Depending on the control strategy employed, the fluctuating renewable production...... 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...
Interconnector capacity allocation in offshore grids with variable wind generation
DEFF Research Database (Denmark)
Schröder, Sascha Thorsten
2013-01-01
. 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...
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.
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...
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
Reliable Grid Condition Detection and Control of Single-Phase Distributed Power Generation Systems
DEFF Research Database (Denmark)
Ciobotaru, Mihai
The constant growth of Distributed Power Generation Systems (DPGS) presents an efficient and economic way of generating electricity closer to the load(s). The DPGS can contribute to an efficient and renewable electricity future by potentially: increasing the use of renewable sources of energy......; improving the efficiency of the electricity system by reducing transmission and distribution losses; improving the security of the electricity supply through increased diversity of supply and reduced vulnerability to simultaneous system failures. However, the new trend of using DPGS comes also with a suite...... of new challenges. One of the challenges is the interaction between the DPGS and the utility grid. As a consequence, grid interconnection requirements applying to distributed generation are continuously updated in order to maintain the quality and the stability of the utility grid. The new upcoming...
Optimal DG Source Allocation for Grid Connected Distributed Generation with Energy Storage System
Directory of Open Access Journals (Sweden)
S. Ezhilarasan
2015-05-01
Full Text Available This study proposes an Energy Management System (EMS for allocation of DG source in a grid connected hybrid power system. Modeling and simulation for EMS is implemented using MATLAB/SIMULINK package. The objective of proposed EMS for micro grid is to optimize the fuel cost, improving the energy utilization efficiency and to manage the peak load demand by scheduling the generation according to the availability of the fuel. The proposed intelligent energy management system is designed to optimize the availability of energy to the load according to the level of priority and to manage the power flow. The developed management system performance was assessed using a hybrid system having PV panels, Wind Turbine (WT, battery and biomass gasifier. Real time field test has been conducted and the parameters i.e., solar irradiance, temperature, wind speed are gathered from 4.05 KW off grid and 2.0 KW On grid Solar Photovoltaic systems (SPV system and wind turbine. The dynamic behavior of the proposed model is examined under different operating conditions. The simulation results of proposed EMS using fuzzy logic expert system shows the minimization on the operating cost and emission level of micro grid by optimal scheduling of power generation and maintains the State of Charge (SOC of batteries in desired value which improves the battery life. The proposed multi objective intelligent energy management system aims to minimize the operational cost and the environmental impact of a micro grid.
Mitigation of Power Quality Problems in Grid-Interactive Distributed Generation System
Bhende, C. N.; Kalam, A.; Malla, S. G.
2016-04-01
Having an inter-tie between low/medium voltage grid and distributed generation (DG), both exposes to power quality (PQ) problems created by each other. This paper addresses various PQ problems arise due to integration of DG with grid. The major PQ problems are due to unbalanced and non-linear load connected at DG, unbalanced voltage variations on transmission line and unbalanced grid voltages which severely affect the performance of the system. To mitigate the above mentioned PQ problems, a novel integrated control of distribution static shunt compensator (DSTATCOM) is presented in this paper. DSTATCOM control helps in reducing the unbalance factor of PCC voltage. It also eliminates harmonics from line currents and makes them balanced. Moreover, DSTATCOM supplies the reactive power required by the load locally and hence, grid need not to supply the reactive power. To show the efficacy of the proposed controller, several operating conditions are considered and verified through simulation using MATLAB/SIMULINK.
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 ...
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.
Comparative Study of on and off Grid Tied Integrated Diesel/Solar (PV) Battery Generation System
Okedu, Kenneth; Uhunmwangho, Roland; Bassey, Ngang
2015-01-01
This paper presents a proposed hybrid system based on diesel generator and solar photovoltaic (PV) as an effective option to power a small remote community. The cost of running diesel generator speedily due to erratic power supply in a small remote community that is not grid connected is highly expensive and not environmentally friendly. A solar PV was used to reduce or augment the continuous diesel generator sets, resulting in reduced cost of operation and maintenance. A proper solar radiati...
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.
Aerodynamic study of sounding rocket flows using Chimera and patched multiblock meshes
Directory of Open Access Journals (Sweden)
João Alves de Oliveira Neto
2011-01-01
Full Text Available Aerodynamic flow simulations over a typical sounding rocket are presented in this paper. The work is inserted in the effort of developing computational tools necessary to simulate aerodynamic flows over configurations of interest for Instituto de Aeronáutica e Espaço of Departamento de Ciência e Tecnologia Aeroespacial. Sounding rocket configurations usually require fairly large fins and, quite frequently, have more than one set of fins. In order to be able to handle such configurations, the present paper presents a novel methodology which combines both Chimera and patched multiblock grids in the discretization of the computational domain. The flows of interest are modeled using the 3-D Euler equations and the work describes the details of discretization procedure, which uses a finite difference approach for structure, body-conforming, multiblock grids. The method is used to calculate the aerodynamics of a sounding rocket vehicle. The results indicate that the present approach can be a powerful aerodynamic analysis and design tool.
Performance Analysis of a Hybrid Overset Multi-Block Application on Multiple Architectures
Djomehri, M. Jahed; Biswas, Rupak
2003-01-01
This paper presents a detailed performance analysis of a multi-block overset grid compu- tational fluid dynamics app!ication on multiple state-of-the-art computer architectures. The application is implemented using a hybrid MPI+OpenMP programming paradigm that exploits both coarse and fine-grain parallelism; the former via MPI message passing and the latter via OpenMP directives. The hybrid model also extends the applicability of multi-block programs to large clusters of SNIP nodes by overcoming the restriction that the number of processors be less than the number of grid blocks. A key kernel of the application, namely the LU-SGS linear solver, had to be modified to enhance the performance of the hybrid approach on the target machines. Investigations were conducted on cacheless Cray SX6 vector processors, cache-based IBM Power3 and Power4 architectures, and single system image SGI Origin3000 platforms. Overall results for complex vortex dynamics simulations demonstrate that the SX6 achieves the highest performance and outperforms the RISC-based architectures; however, the best scaling performance was achieved on the Power3.
Energy Technology Data Exchange (ETDEWEB)
Talukdar, P.; Steven, M.; Issendorff, F.V.; Trimis, D. [Institute of Fluid Mechanics (LSTM), University of Erlangen-Nuremberg, Cauerstrasse 4, D 91058 Erlangen (Germany)
2005-10-01
The finite volume method of radiation is implemented for complex 3-D problems in order to use it for combined heat transfer problems in connection with CFD codes. The method is applied for a 3-D block structured grid in a radiatively participating medium. The method is implemented in non-orthogonal curvilinear coordinates so that it can handle irregular structure with a body-fitted structured grid. The multiblocking is performed with overlapping blocks to exchange the information between the blocks. Five test problems are considered in this work. In the first problem, present work is validated with the results of the literature. To check the accuracy of multiblocking, a single block is divided into four blocks and results are validated against the results of the single block simulated alone in the second problem. Complicated geometries are considered to show the applicability of the present procedure in the last three problems. Both radiative and non-radiative equilibrium situations are considered along with an absorbing, emitting and scattering medium. (author)
Generating grids directly on CAD database surfaces using a parametric evaluator approach
Gatzhe, Timothy D.; Melson, Thomas G.
1995-01-01
A very important, but often overlooked step in grid generation is acquiring a suitable geometry definition of the vehicle to be analyzed. In the past, geometry was usually obtained by generating a number of cross-sections of each component. A number of recent efforts have focussed on non-uniform rational B-spline surfaces (NURBS) to provide as single type of analytic surface to deal with inside the grid generator. This approach has required the development of tools to read other types of surfaces and convert them, either exactly or by approximation, into a NURBS surface. This paper describes a more generic parametric evaluator approach, which does not rely on a particular surface type internal to the grid generation system and is less restrictive in the number of surface types that can be represented exactly. This approach has been implemented in the McDonnell Douglas grid generation system, MACGS, and offers direct access to all types of surfaces from a Unigraphics part file.
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.
Locally-orthogonal, unstructured grid-generation for general circulation modelling on the sphere
Engwirda, Darren
2016-01-01
An algorithm for the generation of non-uniform, locally-orthogonal staggered unstructured grids on spheroidal geometries is described. This technique is designed to generate high-quality staggered Voronoi/Delaunay dual meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather predication. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of guaranteed-quality, unstructured spheroidal Delaunay triangulations is introduced. A locally-orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. The initial staggered Voronoi/Delaunay tessellation is iteratively improved through hill-climbing optimisation techniques. It is shown that this approach typically produces grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. Initial results are presented for a se...
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.
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...
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.
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…
Chiappini, D.; Donno, A.
2016-06-01
In this paper we present a comparison of three different grids generated with a fractal method and used for fluid dynamic simulations through a kinetic approach. We start from the theoretical element definition and we introduce some optimizations in order to fulfil requirements. The study is performed with analysing results both in terms of friction factor at different Reynolds regimes and streamlines paths.
Bailey, R. T.; Shih, T. I.-P.; Nguyen, H. L.; Roelke, R. J.
1990-01-01
An efficient computer program, called GRID2D/3D, was developed to generate single and composite grid systems within geometrically complex two- and three-dimensional (2- and 3-D) spatial domains that can deform with time. GRID2D/3D generates single grid systems by using algebraic grid generation methods based on transfinite interpolation in which the distribution of grid points within the spatial domain is controlled by stretching functions. All single grid systems generated by GRID2D/3D can have grid lines that are continuous and differentiable everywhere up to the second-order. Also, grid lines can intersect boundaries of the spatial domain orthogonally. GRID2D/3D generates composite grid systems by patching together two or more single grid systems. The patching can be discontinuous or continuous. For continuous composite grid systems, the grid lines are continuous and differentiable everywhere up to the second-order except at interfaces where different single grid systems meet. At interfaces where different single grid systems meet, the grid lines are only differentiable up to the first-order. For 2-D spatial domains, the boundary curves are described by using either cubic or tension spline interpolation. For 3-D spatial domains, the boundary surfaces are described by using either linear Coon's interpolation, bi-hyperbolic spline interpolation, or a new technique referred to as 3-D bi-directional Hermite interpolation. Since grid systems generated by algebraic methods can have grid lines that overlap one another, GRID2D/3D contains a graphics package for evaluating the grid systems generated. With the graphics package, the user can generate grid systems in an interactive manner with the grid generation part of GRID2D/3D. GRID2D/3D is written in FORTRAN 77 and can be run on any IBM PC, XT, or AT compatible computer. In order to use GRID2D/3D on workstations or mainframe computers, some minor modifications must be made in the graphics part of the program; no
DEFF Research Database (Denmark)
Ghzaiel, Walid; Jebali-Ben Ghorbal, Manel; Slama-Belkhodja, Ilhem;
2013-01-01
The penetration of the distributed power generation systems (DPGSs) based on renewable sources (PV, WT) is strongly dependent on the quality of the power injected to the utility grid. However, the grid impedance variation, mainly caused by grid faults somewhere in the electric network, can degrade...... 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...... 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...
Understanding the Temporal and Spatial Variability of New Generation Gridded TMYs
Energy Technology Data Exchange (ETDEWEB)
Lopez, Anthony
2017-04-26
Presentation at ASHRAE about the spatial and temporal variability of gridded TMYs, discussing advanced GIS and Web services that allow for direct access to data, surface-based observations for thousands of stations, climate reanalysis data, and products derived from satellite data; new developments in NREL's solar databases based on both observed data and satellite-derived gridded data, status of TMY3 weather files, and NREL's plans for the next-generation TMY weather files; and also covers what is new and different in the Climatic Design Conditions Table in the 2013 ASHRAE Handbook of Fundamentals.
Eichman, Joshua David
Renewable resources including wind, solar, geothermal, biomass, hydroelectric, wave and tidal, represent an opportunity for environmentally preferred generation of electricity that also increases energy security and independence. California is very proactive in encouraging the implementation of renewable energy in part through legislation like Assembly Bill 32 and the development and execution of Renewable Portfolio Standards (RPS); however renewable technologies are not without challenges. All renewable resources have some resource limitations, be that from location, capacity, cost or availability. Technologies like wind and solar are intermittent in nature but represent one of the most abundant resources for generating renewable electricity. If RPS goals are to be achieved high levels of intermittent renewables must be considered. This work explores the effects of high penetration of renewables on a grid system, with respect to resource availability and identifies the key challenges from the perspective of the grid to introducing these resources. The HiGRID tool was developed for this analysis because no other tool could explore grid operation, while maintaining system reliability, with a diverse set of renewable resources and a wide array of complementary technologies including: energy efficiency, demand response, energy storage technologies and electric transportation. This tool resolves the hourly operation of conventional generation resources (nuclear, coal, geothermal, natural gas and hydro). The resulting behavior from introducing additional renewable resources and the lifetime costs for each technology is analyzed.
Voltage Stability Improvement of Grid Connected Wind Driven Induction Generator Using Svc
Directory of Open Access Journals (Sweden)
Ruchi Aggarwal
2014-05-01
Full Text Available Voltage stability is one of the major problem associated with wind power generating system which may be due to fluctuating nature of wind, heavy load, fault occurrence or insufficient reactive power supply. The wind power generating system most commonly employed with squirrel cage induction generator(SCIG that needs the support of an external device such as capacitor bank, FACTS devices etc. to support reactive power in order to remain connected with the grid during voltage dips. The voltage stability of a wind driven induction generator can be improved by using FACTS devices such as SVC, STATCOM.In this paper svc is used for voltage stability improvement.
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.
MULTI-BLOCK CHAINING-BASED AUTHENTICATION MODE
Institute of Scientific and Technical Information of China (English)
Huang Yuhua; Hu Aiqun; Zhong Ziguo
2006-01-01
A fast authentication mode based on Multi-Block Chaining (MBC) is put forward; and its security is proved. The MBC mode is for new generation block cipher algorithms. Its speed is about 13% faster than that of the authentication modes in common use (for example, cipher block chaining-message authentication code mode). The dependence test results meet the requirement. The MBC mode is complete; its degree of avalanche effect is about 0.9993; its degree of strict avalanche criterion is 0.992 or so. The frequency test results indicate that the output generated by the MBC mode has uniformity. The binary matrix rank test results imply that it is linear independent among disjoint sub-matrices of the output. Maurer's universal statistical test results show that the output could be significantly compressed without loss of information. Run test, spectral test,non-overlapping template matching test, overlapping template matching test, Lempel-Ziv compression test,linear complexity test, serial test, approximate entropy test, cumulative sums test, random excursions test and random excursions variant test results fulfill the requirements of all. Therefore the MBC mode has good pseudo-randomness. Thus the security of MBC mode is verified by the way of statistical evaluation.
Institute of Scientific and Technical Information of China (English)
Zhang Laiping; Zhao Zhong; Chang Xinghua; He Xin
2013-01-01
A hybrid grid generation technique and a multigrid/parallel algorithm are presented in this paper for turbulence flow simulations over three-dimensional (3D) complex geometries.The hybrid grid generation technique is based on an agglomeration method of anisotropic tetrahedrons.Firstly,the complex computational domain is covered by pure tetrahedral grids,in which anisotropic tetrahedrons are adopted to discrete the boundary layer and isotropic tetrahedrons in the outer field.Then,the anisotropic tetrahedrons in the boundary layer are agglomerated to generate prismatic grids.The agglomeration method can improve the grid quality in boundary layer and reduce the grid quantity to enhance the numerical accuracy and efficiency.In order to accelerate the convergence history,a multigrid/parallel algorithm is developed also based on anisotropic agglomeration approach.The numerical results demonstrate the excellent accelerating capability of this multigrid method.
Thomson, Dana R; Stevens, Forrest R; Ruktanonchai, Nick W; Tatem, Andrew J; Castro, Marcia C
2017-07-19
Household survey data are collected by governments, international organizations, and companies to prioritize policies and allocate billions of dollars. Surveys are typically selected from recent census data; however, census data are often outdated or inaccurate. This paper describes how gridded population data might instead be used as a sample frame, and introduces the R GridSample algorithm for selecting primary sampling units (PSU) for complex household surveys with gridded population data. With a gridded population dataset and geographic boundary of the study area, GridSample allows a two-step process to sample "seed" cells with probability proportionate to estimated population size, then "grows" PSUs until a minimum population is achieved in each PSU. The algorithm permits stratification and oversampling of urban or rural areas. The approximately uniform size and shape of grid cells allows for spatial oversampling, not possible in typical surveys, possibly improving small area estimates with survey results. We replicated the 2010 Rwanda Demographic and Health Survey (DHS) in GridSample by sampling the WorldPop 2010 UN-adjusted 100 m × 100 m gridded population dataset, stratifying by Rwanda's 30 districts, and oversampling in urban areas. The 2010 Rwanda DHS had 79 urban PSUs, 413 rural PSUs, with an average PSU population of 610 people. An equivalent sample in GridSample had 75 urban PSUs, 405 rural PSUs, and a median PSU population of 612 people. The number of PSUs differed because DHS added urban PSUs from specific districts while GridSample reallocated rural-to-urban PSUs across all districts. Gridded population sampling is a promising alternative to typical census-based sampling when census data are moderately outdated or inaccurate. Four approaches to implementation have been tried: (1) using gridded PSU boundaries produced by GridSample, (2) manually segmenting gridded PSU using satellite imagery, (3) non-probability sampling (e.g. random-walk, "spin
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)
DEFF Research Database (Denmark)
Yao, Jun; Li, Hui; Chen, Zhe
2013-01-01
This paper presents an enhanced control method for a doubly fed induction generator (DFIG)-based wind-power generation system with series grid-side converter (SGSC) under unbalanced grid voltage conditions. The behaviors of the DFIG system with SGSC during network unbalance are described. By inje......This paper presents an enhanced control method for a doubly fed induction generator (DFIG)-based wind-power generation system with series grid-side converter (SGSC) under unbalanced grid voltage conditions. The behaviors of the DFIG system with SGSC during network unbalance are described....... By injecting a series control voltage generated from the SGSC to balance the stator voltage, the adverse effects of voltage unbalance upon the DFIG, such as stator and rotor current unbalances, electromagnetic torque, and power pulsations, can be removed, and then the conventional vector control strategy...... for the rotor-side converter remains in full force under unbalanced conditions. Meanwhile, three control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in the total active power or reactive power, or eliminating negative-sequence current injected...
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.
ADAPTIVE LAYERED CARTESIAN CUT CELL METHOD FOR THE UNSTRUCTURED HEXAHEDRAL GRIDS GENERATION
Institute of Scientific and Technical Information of China (English)
WU Peining; TAN Jianrong; LIU Zhenyu
2007-01-01
Adaptive layered Cartesian cut cell method is presented to solve the difficulty of the unstructured hexahedral anisotropic Cartesian grids generation from the complex CAD model. Vertex merging algorithm based on relaxed AVL tree is investigated to construct topological structure for stereo lithography (STL) files, and a topology-based self-adaptive layered slicing algorithm with special features control strategy is brought forward. With the help of convex hull, a new points-in-polygon method is employed to improve the Cartesian cut cell method. By integrating the self-adaptive layered slicing algorithm and the improved Cartesian cut cell method, the adaptive layered Cartesian cut cell method gains the volume data of the complex CAD model in STL file and generates the unstructured hexahedral anisotropic Cartesian grids.
DEFF Research Database (Denmark)
Høskuldsson, Agnar; Svinning, K.
2006-01-01
Here is presented a unified approach to modelling multi-block regression data. The starting point is a partition of the data X into L data blocks, X = (X-1, X-2,...X-L), and the data Y into M data-blocks, Y = (Y-1, Y-2,...,Y-M). The methods of linear regression, X -> Y, are extended to the case...... of a linear relationship between each X-i and Y-j. X-i -> Y-j. A modelling strategy is used to decide if the residual X-i should take part in the modelling of one or more Y(j)s. At each step the procedure of finding score vectors is based on well-defined optimisation procedures. The principle of optimisation...... is based on that the score vectors should give the sizes of the resulting Y(j)s loading vectors as large as possible. The partition of X and Y are independent of each other. The choice of Y-j can be X-j, Y-i = X-i, thus including the possibility of modelling X -> X-i,i=1,...,L. It is shown how...
Enhanced method for the generation of binary Fresnel holograms based on grid-cross downsampling
Institute of Scientific and Technical Information of China (English)
W. K. Cheung; Peter Tsang; T. C. Poon; Changhe Zhou
2011-01-01
Past research has demonstrated that digital Fresnel holograms can be binarized in a non-iterative manner by downsampling the source image with a grid lattice prior to the hologram generation process. The reconstructed image of a hologram that is binarized with this approach is superior in quality compared with that obtained with direct thresholding, half-toning, and error diffusion. Despite the success, the downsampling mechanism results in a prominent texture of regularly spaced voids in the shaded regions. To alleviate this problem, an enhanced non-iterative method for the generation of binary Fresnel holograms is presented. Our method is based on a multi-direction line-sampling formed by a combined grid and cross lattice, which is capable of preserving a more solid texture in the shaded regions and enhancing the visual quality of the reconstructed image. Computer simulations and optical reconstructions are shown to demonstrate the effectiveness of our proposed technique.%Past research has demonstrated that digital Fresnel holograms can be binarized in a non-iterative manner by downsampling the source image with a grid lattice prior to the hologram generation process.The reconstructed image of a hologram that is binarized with this approach is superior in quality compared with that obtained with direct thresholding,half-toning,and error diffusion.Despite the success,the downsampling mechanism results in a prominent texture of regularly spaced voids in the shaded regions.To alleviate this problem,an enhanced non-iterative method for the generation of binary Fresnel holograms is presented.Our method is based on a multi-direction line-sampling formed by a combined grid and cross lattice,which is capable of preserving a more solid texture in the shaded regions and enhancing the visual quality of the reconstructed image.Computer simulations and optical reconstructions are shown to demonstrate the effectiveness of our proposed technique.
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 ...... fluctuation, and may even damage the rotor converter, if the design is not considered carefully....
2015-01-01
A simple power electronic interface based on the line-commutated inverter (LCI) has been developed in order to inject sinusoidal current to the grid for single-phase grid-connected photovoltaic (PV) energy generation systems. The proposed inverter facilitates controlling the injecting/grid current with a controllable power factor in contrast to the conventional LCI system. It is achieved that the total harmonic distortion (THD) of the injecting currents for the different firin...
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.
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.
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.
Directory of Open Access Journals (Sweden)
B. Chitti Babu
2014-12-01
Full Text Available A fast and exact detection of phase and fundamental frequency of grid voltage/current is essential for calculating accurate reference signal in order to implement the control algorithm of inverter-interfaced distributed generation (DG system and realize precise harmonic compensation. However, the methods adapted in the literature based on phase locked loop (PLL exhibits large phase error, be difficult to implement, and their performance is also indistinct under conditions where the grid frequency varies or the supply is distorted with low frequency harmonics. This paper explores an improved phase detection system for DG system based on Sliding Discrete Fourier Transform (SDFT. The proposed SDFT based phase detection shows a robust phase tracking capability with fast transient response under adverse situation of the grid. Moreover, SDFT phase detection system is more efficient as it requires small number of operations to extract a single frequency component, thereby reducing computational complexity and simpler than DFT. The superior performance of proposed SDFT phase detection system is analyzed and the obtained results are compared with Discrete Fourier Transform (DFT filtering to confirm the feasibility of the study under different grid environment such as high frequency harmonic injection, frequency deviation, and phase variation etc.
Generation of reproducible turbulent inflows for wind tunnel applications using active grids
Kroeger, Lars; Guelker, Gerd; Peinke, Joachim
2016-11-01
Turbulent flows are omnipresent in nature. In the case of wind energy applications, reproducible measurements in situ are quite difficult, therefore research in turbulence demands for experimental setups with reproducible turbulent flow fields. To simulate the situation from the outside in a wind tunnel an active grid can be used. It consists of horizontal and vertical rotating axes with attached square flaps which could be moved individually. This dynamically driven setup and the possibility to repeat the motions of the active grid axes permits to generate reproducible, statistically well defined turbulence with a wide range of statistical behavior. The objective of this work is to create turbulence with two active grids of different dimensions, to establish comparable setups in our available wind tunnel facilities. In this study the wake of the active grids was investigated by high speed PIV and hotwire measurements. To determine the similarities and limitations between the setups of different dimensions the hotwire data is compared using higher order statistics, increment analysis and the power spectra. The PIV data is used to observe spatial correlations and the prevailing length scales in the turbulent wakes. First results regarding this comparison are shown.
Directory of Open Access Journals (Sweden)
Suroso Suroso
2014-12-01
Full Text Available Renewable power generation using photovoltaic is very interesting to be developed to deal with the problems of conventional energy sources and environmental issues. The photovoltaic power generation can operate both in stand-alone and grid-connected operations. This paper presents an application of the five-level common-emitter current-source inverter (CE-CSI for grid connected photovoltaic system without batteries as energy storage system. In the proposed system, the five-level CE-CSI works generating a sinusoidal output current from photovoltaic system to be injected into the power grid. The transformer is used in the system to step-down the grid voltage to meet the voltage level of the photovoltaic system, and also works as a galvanic insulation between the power grid and the inverter system. Two conditions of the power grid voltage, i.e. a pure sinusoidal and a distorted power grid, are tested through computer simulation using PSIM software. Furthermore, experimental test result of the five-level inverter is also presented. The test results show that the five-level CE-CSI works well injecting a sinusoidal current into the power grid with low harmonic contents, and with unity power factor operation. The results also show that the distorted grid voltage affects the harmonic contents of the current injected by the inverter.
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.
Szmelter, J.; Marchant, M. J.; Evans, A.; Weatherill, N. P.
A cell vertex finite volume Jameson scheme is used to solve the 2D compressible, laminar, viscous fluid flow equations on locally embedded multiblock meshes. The proposed algorithm is applicable to both the Euler and Navier-Stokes equations. It is concluded that the adaptivity method is very successful in efficiently improving the accuracy of the solution. Both the mesh generator and the flow equation solver which are based on a quadtree data structure offer good flexibility in the treatment of interfaces. It is concluded that methods under consideration lead to accurate flow solutions.
A Novel Algorithm of Forecasting the Potential Development of Generation in the Distribution Grid
Directory of Open Access Journals (Sweden)
Michał Bajor
2014-06-01
Full Text Available The paper presents a novel method of forecasting the potential for the development of various types of generation, including renewable, connecting to the distribution grid. The proposed algorithm is based on the idea of identifying different factors influencing the possibility of developing various types of generation in different time horizons. Descriptions of subsequent stages of the forecasting procedure, used terms and the software implementing the algorithm, developed by the authors, are also included in the paper. Finally, comments regarding the reliability of the results obtained using the method are described.
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.
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.
Engwirda, Darren
2017-01-01
An algorithm for the generation of non-uniform, locally orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered VoronoiDelaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a priori bounds on element size and shape. Grid quality is further improved through the application of hill-climbing-type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid-type finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution-type studies is discussed in detail.
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...
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...
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.
A Grid Generator for Novel PDP Device%新型PDP器件网格发生
Institute of Scientific and Technical Information of China (English)
杨兰兰; 屠彦
2001-01-01
Agrid generator is designed in this project. This grid generator is mainly applied to generate the meshes of two-dimensional model of PDP. This grid generator can be used in various structures. It can deal with not only the different barrier boundary shape of new type PDP, but also the normal model of AC-PDP. The grid generating is the basis of numerical simulation and it has a direct relationship with the calculation result. Here necessalry data information for calculation is recorded. The result is shown both in graphics mode and data bank.%本文使用Visual C++语言编写的网格发生软件，主要用于产生新型PDP器件的二维空间结构模型的网格。该网格发生器不仅能够处理新型PDP结构模型边界情况的多样性，还能处理一般的对向放电式和表面放电式AC-PDP结构。网格产生是数值模拟显示单元放电情况的基础。因此，本软件除了能够处理各种不同的结构形式外，还记录了后续计算中需用到的各种有用的数据信息，具有较强的通用性。同时，还对网格产生情况进行了可视化输出。
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.
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
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...... model, an electrothermal model, and the lifetime model of the power semiconductor devices. An accurate long-term simulation model able to consider the one-year RFMP (solar irradiance and ambient temperature) is developed. Thus, the one-year estimation of the converter device thermal loading distribution...... 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...
Supramolecular Multiblock Copolymers Featuring Complex Secondary Structures.
Elacqua, Elizabeth; Manning, Kylie B; Lye, Diane S; Pomarico, Scott K; Morgia, Federica; Weck, Marcus
2017-09-06
This contribution introduces main-chain supramolecular ABC and ABB'A block copolymers sustained by orthogonal metal coordination and hydrogen bonding between telechelic polymers that feature distinct secondary structure motifs. Controlled polymerization techniques in combination with supramolecular assembly are used to engineer heterotelechelic π-sheets that undergo high-fidelity association with both helical and coil-forming synthetic polymers. Our design features multiple advances to achieve our targeted structures, in particular, those emulating sheet-like structural aspects using poly(p-phenylenevinylene)s (PPVs). To engineer heterotelechelic PPVs in a sheet-like design, we engineer an iterative one-pot cross metathesis-ring-opening metathesis polymerization (CM-ROMP) strategy that affords functionalized Grubbs-II initiators that subsequently polymerize a paracyclophanediene. Supramolecular assembly of two heterotelechelic PPVs is used to realize a parallel π-sheet, wherein further orthogonal assembly with helical motifs is possible. We also construct an antiparallel π-sheet, wherein terminal PPV blocks are adjacent to a flexible coil-like poly(norbornene) (PNB). The PNB is designed, through supramolecular chain collapse, to expose benzene and perfluorobenzene motifs that promote a hairpin turn via charge-transfer-aided folding. We demonstrate that targeted helix-(π-sheet)-helix and helix-(π-sheet)-coil assemblies occur without compromising intrinsic helicity, while both parallel and antiparallel β-sheet-like structures are realized. Our main-chain orthogonal assembly approach allows the engineering of multiblock copolymer scaffolds featuring diverse secondary structures via the directional assembly of telechelic building blocks. The targeted assemblies, a mix of sequence-defined helix-sheet-coil and helix-sheet-helix architectures, are Nature-inspired synthetic mimics that expose α/β and α+β protein classes via de novo design and cooperative assembly
A Vector Control for Grid-connected Wind Power Generation with Doubly Fed Induction Generator
Kai, Takaaki; Tanaka, Yuji; Kaneda, Hirotoshi; Kobayashi, Daichi; Tanaka, Akio
Recently, doubly fed induction generator (DFIG) and synchronous generator are mostly applied for wind power generation due to high efficiently for wind energy capture. An inverter system is required to control wind turbine speed and power factor in those generators. The inverter rating of the synchronous generator equals to generator rating. However, DFIG has the advantage that the inverter rating is about 25% to the generator rating. The paper describes a vector control of DFIG inter-connected to power line. The performance of proposed vector control is examined using power system simulation software PSCAD/EMTDC for the DFIG inter-connected to 6.6kv distribution line. The results show good dynamic responses and high accuracy to the stator active power control and the stator reactive power control.
Mitigation of Output Power Fluctuations in Utility Grid using Three Phase Distribution Generation
Directory of Open Access Journals (Sweden)
K.Sri Chandan,
2010-12-01
Full Text Available Renewable electricity generation has never seen the level of investment and incentives that have been put in place by governments around the world during the last decade. However, despite the envisaged environmental and security of supply benefits that the harvesting of indigenous, renewable sources might bring about, their integration into the power system creates significant challenges to both the network operators and developers. The power quality challenges become even greater when large volumes of renewable generation capacity are connected to distribution networks, traditionally designed to be passive circuits with unidirectional power flows. This paper presents two schemes to meet the different power quality challenges in the utility grid due to Distribution Generation. In this first scheme is DSTATCOM and second is three phase Distributed Generation. This work is aimed at demonstrating, from the planning perspective, the benefits that the adoption of the different compensators might bring the system to a ‘fit and forget’ approach.
Kai, Takaaki; Tanaka, Yuji; Kaneda, Hirotoshi; Kobayashi, Daichi; Tanaka, Akio
Recently, doubly fed induction generator (DFIG) and synchronous generator are mostly applied for wind power generation, and variable speed control and power factor control are executed for high efficiently for wind energy capture and high quality for power system voltage. In variable speed control, a wind speed or a generator speed is used for maximum power point tracking. However, performances of a wind generation power fluctuation due to wind speed variation have not yet investigated for those controls. The authors discuss power smoothing by those controls for the DFIG inter-connected to 6.6kV distribution line. The performances are verified using power system simulation software PSCAD/EMTDC for actual wind speed data and are examined from an approximate equation of wind generation power fluctuation for wind speed variation.
Dynamic Response of a Grid Connected Wind Farm with Different Types of Generators
Directory of Open Access Journals (Sweden)
Helmy Mohammed El_ Zoghby
2012-01-01
Full Text Available For a wide areas wind farm, which composed of different zones of different wind turbines and different generators , this paper aims to simulate a wind farm model that icludes a wind turbine and three different types of generators , which are three phase synchronous generator, three phase squirrel-cage induction generator and three phase doubly-fed induction generator ,these generators are the main machines that generally used in the field of wind energy generation. All generators are connected in parallel at the point of common coupling (pcc and connected to the utility grid . This model is a simple representation of the actual model of zafarana wind farm, which is the biggest wind farm in Egypt and further to use it in different kinds of simulations, and display the difference in response among all generators, where all generators are 500 kw power rating , and subjected to the same operating conditions . After modeling the system, the transient response of the system will be studied and analyzed at different operating cases as: Case.1 constant wind speed operation Case.2 variable wind speed operation Case.3 sudden change in turbine mechanical power Case.4 sudden change in wind speed. So this paper introduces a survey on the dynamic response of a large wind farm of different generators at different operating conditions Keywords: modeling, synchronous generator, induction generator, wind farm, simulation model, transient analysis.
Application of multi-block methods in cement production
DEFF Research Database (Denmark)
Svinning, K.; Høskuldsson, Agnar
2008-01-01
Compressive strength at 1 day of Portland cement as a function of the microstructure of cement was statistically modelled by application of multi-block regression method. The observation X-matrix was partitioned into four blocks, the first block representing the mineralogy, the second particle size...
Meter-long multiblock copolymer microfibers via interfacial bioorthogonal polymerization.
Liu, Shuang; Zhang, Han; Remy, Roddel A; Deng, Fei; Mackay, Michael E; Fox, Joseph M; Jia, Xinqiao
2015-05-01
High-molecular-weight multiblock copolymers are synthesized as robust polymer fibers via interfacial bioorthogonal polymerization employing the rapid cycloaddition of s-tetrazines with strained trans-cyclooctenes. When cell-adhesive peptide is incorporated in the tetrazine monomer, the resulting protein-mimetic polymer fibers provide guidance cues for cell attachment and elongation.
FACTS Devices Using Neuro Fuzzy Controller in Stabilization of Grid Connected Wind Generator.
Directory of Open Access Journals (Sweden)
ROHI KACHROO
2012-05-01
Full Text Available Wind power is one of the renewable energy sources. It has various advantages like, cost competitiveness, environmentally clean and safeness. Large wind farms have stability problems when they are integrated to the power system. A thorough analysis is required to identify the stability problems and to develop measures to improve it. Mostly used wind generator is a fixed speed induction generator, which requires reactive power to maintain air gap flux. Reactive ower equipments are used to enable recovery of large wind farms from severe system disturbances. In this paper shunt and series FACTS evices, Static Synchronous Compensator (STATCOM and Static ynchronous Series Compensator are used for the purpose of stabilizing grid connected wind generator against the grid-side disturbances. The essential feature of the FACTS devices is their ability to absorb or inject the reactive power. Since stability is a non linear process so system performance can be improved by using nonlinear controllers. Neurofuzzy controller (NFC is a non linear controller. NFC has fasterresponse than conventional PI controllers
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.
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.
Effect of Contraction on Turbulence and Temperature Fluctuations Generated by a Warm Grid
Mills, Robert R., Jr.; Corrsin, Stanley
1959-01-01
Hot-wire anemometer measurements were made of several statistical properties of approximately homogeneous and isotropic fields of turbulence and temperature fluctuations generated by a warm grid in a uniform airstream sent through a 4-to-1 contraction. These measurements were made both in the contraction and in the axisymmetric domain farther downstream. In addition to confirming the well-known turbulence anisotropy induced by strain, the data show effects on the skewnesses of both longitudinal velocity fluctuation (which has zero skewness in isotropic turbulence) and its derivative. The concomitant anisotropy in the temperature field accelerates the decay of temperature fluctuations.
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...
Power Generation and Voltage Regulation of 132KV Karbala grid using DFIG Wind Turbine Generator
Directory of Open Access Journals (Sweden)
Qasim Kamil Mohsin
2015-06-01
Full Text Available Due to increasing demand on electrical energy in Iraq and to have clean energy that is environmental friendly, wind energy would be one of the most important and promising sources of renewable energy to achieve this goal. This paper discussed the reasons to use the Doubly-Feed Induction Generator (DFIG amongst the available types of wind turbine generators, and in section (III illustrate Motivations to select place to the wind farm construction. using decupling method (the vector control strategy to change reactive power of DFIG 2MW connected to middle of the 132KV transmission line (Karbala north – Alahkader without effect about the active power generated from DFIG itself with fixed wind speed value assumed to provide the voltage regulation, and control of the transmission line In addition to power generating. By using PSCAD/EMTDC, different simulation results are presented based on various scenarios.
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.
On Grid-connected of Distributed Generation in Smart Distribution Grid%智能配电网中分布式电源并网的思考
Institute of Scientific and Technical Information of China (English)
王淼; 董仲星; 刘宗歧
2012-01-01
智能配电网是统一坚强智能电网的重要组成，是智能电网中连接主网和面向用户供电的重要组成部分。而接纳大规模分布式电源的灵活运行和操作，是智能配电网建成的重要特征之一。本文综合阐述和分析了分布式电源并网的相关内容，介绍了分布式发电技术及相关特性，结合具体算例，重点分析了并网带来的影响，指出智能配电网优化规划的问题和主要研究思路和方法，综合分析分布式并网的保护与控制，为未来分布式电源并网的深入研究和工程实践做铺垫。%Smart distribution grid is an important part of smart grid, which is the connection of main network and customers in smart grid. The acceptation of large-scale distributed generationrs is one of the symbols of the success of smart distribution network. This paper describes the related content about the distributed generation and its parallel operation on power system. Features of distributed generation are raised at first. Then example, the paper focuses on the influence caused by distributed generation synchronization. The technologies and ideas about smart distribution network planning with DGs are discussed in detail, as well as the protection of the parallel operation. This indeed sheds light on unified smart grid construction and its futuristic research of smart grid with distributed generation.
Directory of Open Access Journals (Sweden)
Aolin Liu
2013-05-01
Full Text Available 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 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 for the rotor-side converter (RSC, regardless of grid voltage harmonics. Meanwhile, two control targets for the parallel grid-side converter (PGSC are identified, including eliminating the oscillations in total active and reactive power entering the grid or suppressing the fifth- and seventh-order harmonic currents injected to the grid. Furthermore, the respective PI-R controller in the positive synchronous reference frame for the SGSC voltage control and PGSC current control have been developed to achieve precise and rapid regulation of the corresponding components. Finally, the proposed coordinated control strategy has been fully validated by the simulation results of a 2 MW DFIG-based wind turbine with SGSC under distorted grid voltage conditions.
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.
Foam Multi-Dimensional General Purpose Monte Carlo Generator With Self-Adapting Symplectic Grid
Jadach, Stanislaw
2000-01-01
A new general purpose Monte Carlo event generator with self-adapting grid consisting of simplices is described. In the process of initialization, the simplex-shaped cells divide into daughter subcells in such a way that: (a) cell density is biggest in areas where integrand is peaked, (b) cells elongate themselves along hyperspaces where integrand is enhanced/singular. The grid is anisotropic, i.e. memory of the axes directions of the primary reference frame is lost. In particular, the algorithm is capable of dealing with distributions featuring strong correlation among variables (like ridge along diagonal). The presented algorithm is complementary to others known and commonly used in the Monte Carlo event generators. It is, in principle, more effective then any other one for distributions with very complicated patterns of singularities - the price to pay is that it is memory-hungry. It is therefore aimed at a small number of integration dimensions (<10). It should be combined with other methods for higher ...
Energy Technology Data Exchange (ETDEWEB)
Li, H.; Yang, C.; Chen, H.W. [The State Key Laboratory of Equipment and System Safety of Power Transmission and Distribution and New Technology, Electrical Engineering College of Chongqing University, Chongqing 400044 (China); Zhao, B. [The State Key Laboratory of Equipment and System Safety of Power Transmission and Distribution and New Technology, Electrical Engineering College of Chongqing University, Chongqing 400044 (China); Sichuan Electric Vocational and Technical College, Chengdu 610072 (China); Chen, Z. [Institute of Energy Technology, Aalborg University, Aalborg East DK-9220 (Denmark)
2011-05-15
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 electromagnetic transient models of a SCIG, the transient behaviors of the wind turbine generation system during a three-phase fault are simulated and compared with the traditional models. Secondly, in order to quickly estimate the transient stability limit of the wind turbine generation system, a direct method 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 stability estimation of the wind turbine generation system. Finally, the CCT at various initial mechanical torques for different dynamical models are calculated and compared with the trial and error method by simulation, when the SCIG stator terminal is subjected to a three-phase short-circuit fault. The results have shown the proposed method and models are correct and valid. (author)
Renewable Distributed Generation Models in Three-Phase Load Flow Analysis for Smart Grid
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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.
Anupindi, Kameswararao; Delorme, Yann; Shetty, Dinesh A; Frankel, Steven H
2013-12-01
Computational fluid dynamics (CFD) simulations are becoming a reliable tool to understand hemodynamics, disease progression in pathological blood vessels and to predict medical device performance. Immersed boundary method (IBM) emerged as an attractive methodology because of its ability to efficiently handle complex moving and rotating geometries on structured grids. However, its application to study blood flow in complex, branching, patient-specific anatomies is scarce. This is because of the dominance of grid nodes in the exterior of the fluid domain over the useful grid nodes in the interior, rendering an inevitable memory and computational overhead. In order to alleviate this problem, we propose a novel multiblock based IBM that preserves the simplicity and effectiveness of the IBM on structured Cartesian meshes and enables handling of complex, anatomical geometries at a reduced memory overhead by minimizing the grid nodes in the exterior of the fluid domain. As pathological and medical device hemodynamics often involve complex, unsteady transitional or turbulent flow fields, a scale resolving turbulence model such as large eddy simulation (LES) is used in the present work. The proposed solver (here after referred as WenoHemo), is developed by enhancing an existing in-house high order incompressible flow solver that was previously validated for its numerics and several LES models by Shetty et al. [Journal of Computational Physics 2010; 229 (23), 8802-8822]. In the present work, WenoHemo is systematically validated for additional numerics introduced, such as IBM and the multiblock approach, by simulating laminar flow over a sphere and laminar flow over a backward facing step respectively. Then, we validate the entire solver methodology by simulating laminar and transitional flow in abdominal aortic aneurysm (AAA). Finally, we perform blood flow simulations in the challenging clinically relevant thoracic aortic aneurysm (TAA), to gain insights into the type of
Energy Technology Data Exchange (ETDEWEB)
Bendel, C.; Nestle, D. [Institut fuer Solare Energieversorgungstechnik (ISET), Kassel (Germany); Malcher, S. [EUS Gesellschaft fuer Innovative Energieumwandlung und -Speicherung mbH, Dortmund (Germany)
2005-07-01
Currently decentralized electrical generation units (DG units) are connected to the network in Europe with an increasing number and generation capacity. Currently the operator of a DG unit or the availability of fluctuation primary energy determines the power and time of the generation fed into the grid. The distribution system operator (DSO) is blind'' towards the current power of the DG units in his grid because of the lack of observability and controllability of these generators in the low voltage level. Therefore a new strategy for the integration of DG units into grid operation will be required. This strategy will include energy management with controllable generators as well as controllable loads. In the concept developed in the project DINAR the point of common coupling (PCC), which acts as the technical as well as legal interface between grid operator on the one side and operator of the generator on the other side, will be extended by a communication interface. This allows a technically efficient design of an energy management system and avoids fundamental organizational changes to the current grid regime. The design of such a bidirectional energy management interface as a new implementation of the PCC is also presented within the article. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Bendel, C.; Nestle, D. [Institut fuer Solare Energieversorgungstechnik (ISET), Kassel (Germany); Malcher, S. [EUS Gesellschaft fuer Innovative Energieumwandlung und -Speicherung mbH, Dortmund (Germany)
2005-07-01
Currently decentralized electrical generation units (DG units) are connected to the network in Europe with an increasing number and generation capacity. Currently the operator of a DG unit or the availability of fluctuation primary energy determines the power and time of the generation fed into the grid. The distribution system operator (DSO) is ''blind'' towards the current power of the DG units in his grid because of the lack of observability and controllability of these generators in the low voltage level. Therefore a new strategy for the integration of DG units into grid operation will be required. This strategy will include energy management with controllable generators as well as controllable loads. In the concept developed in the project DINAR the point of common coupling (PCC), which acts as the technical as well as legal interface between grid operator on the one side and operator of the generator on the other side, will be extended by a communication interface. This allows a technically efficient design of an energy management system and avoids fundamental organizational changes to the current grid regime. The design of such a bidirectional energy management interface as a new implementation of the PCC is also presented within the article. (orig.)
Design and Modeling of Grid Connected Hybrid Renewable Energy Power Generation
Directory of Open Access Journals (Sweden)
M. Kishore Reddy,
2014-09-01
Full Text Available This paper proposes a design and modeling of grid connected hybrid renewable energy power generation. The energy system having a photo voltaic (PV panel, Srg wind turbine and fuel cell (sofc for continuous power flow management. Fuel cells (storage & generating are added to ensure uninterrupted power supply due to the discontinuous nature of solar and wind resources. Renewable energy generated during times of plenty can be stored for use during periods when sufficient electricity is not available. But storing this energy is a difficult task: batteries and similar technologies perform well over short timescales, but over periods of weeks or months a different approach is necessary. Energy storage in the form of hydrogen is one such possibility: excess electricity is fed into an electrolyser to split water into its constituent parts, oxygen and hydrogen. The hydrogen is then used in fuel cells to produce electricity when needed which will overcome the problem of storage. This work is mainly concentrated on the design, analysis and modelling of Fuel cells and Analysis and modelling of Switched Reluctance Generator (SRG in the application of Wind Energy Generation and pv cell. Also an effective approach is proposed in this thesis to ensure renewable energy diversity and effective utilization. The pv cell, wind and fuel cell renewable energy system is digitally simulated using the MATLAB/SIMULINK software environment and fully validated for efficient energy utilizations and enhanced interface power quality under different operating conditions and load excursions
2013-01-01
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 vo...
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
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.
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...... active power control methods are required. As a cost-effective solution to avoid overloading, a Constant Power Generation (CPG) control scheme by limiting the feed-in power has been introduced into the currently active grid regulations. In order to achieve a CPG operation, this paper presents three CPG...
DEFF Research Database (Denmark)
Sangwongwanich, Ariya; Yang, Yongheng; Blaabjerg, Frede
2016-01-01
strategies based on: 1) a power control (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 proposed 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&OCPG algorithm is the most suitable solution in terms of high...... active power control methods are required. As a cost-effective solution to avoid overloading, a Constant Power Generation (CPG) control scheme by limiting the feed-in power has been introduced into the currently active grid regulations. In order to achieve a CPG operation, this paper proposes three CPG...
Energy Technology Data Exchange (ETDEWEB)
Luensdorf, Ontje [OFFIS Oldenburg (Germany); Sonnenschein, Michael [Oldenburg Univ. (Germany); Mohrmann, Michael; Hofmann, Lutz [Hannover Univ. (Germany). IEH FG EE; Gronstedt, Phillip; Kurrat, Michael [TU Braunschweig (Germany). elenia
2011-07-01
The integration of renewable energy generation facilities increases the decentralization of electricity supply as well as feed-in fluctuations. Due to grid stability concerns, the integration capability of distribution grids is limited. The Energy Research Alliance of Lower Saxony (FEN) has developed the grid-driven operation mode, which can be used to reduce the feed-in fluctuations by increasing the flexibility of electricity generation, consumption and storage. This article presents simulation results of the grid-driven operation mode in distribution grids with high penetrations of distributed energy generation facilities. (orig.)
Directory of Open Access Journals (Sweden)
Dahai Zhang
2017-02-01
Full Text Available This paper analyses the effects of doubly fed induction generator (DFIG tidal current turbines on a distribution grid under unbalanced voltage conditions of the grid. A dynamic model of an electrical power system under the unbalanced network is described in the paper, aiming to compare the system performance when connected with and without DFIG at the same location in a distribution grid. Extensive simulations of investigating the effect of DFIG tidal current turbine on stability of the distribution grid are performed, taking into account factors such as the power rating, the connection distance of the turbine and the grid voltage dip. The dynamic responses of the distribution system are examined, especially its ability to ride through fault events under unbalanced grid voltage conditions. The research has shown that DFIG tidal current turbines can provide a good damping performance and that modern DFIG tidal current power plants, equipped with power electronics and low-voltage ride-through capability, can stay connected to weak electrical grids even under the unbalanced voltage conditions, whilst not reducing system stability.
Directory of Open Access Journals (Sweden)
UNLU, M.
2015-05-01
Full Text Available A simple power electronic interface based on the line-commutated inverter (LCI has been developed in order to inject sinusoidal current to the grid for single-phase grid-connected photovoltaic (PV energy generation systems. The proposed inverter facilitates controlling the injecting/grid current with a controllable power factor in contrast to the conventional LCI system. It is achieved that the total harmonic distortion (THD of the injecting currents for the different firing angles/power factors and reference currents is about 5% or less than 5%. Thus, the grid-connected standards for injecting current are satisfied without filter equipment unlike the conventional LCI system. The proposed system has been built in MATLAB/Simulink and examined experimentally on PV array of 160 W. The simulation and experimental results are better performance than the conventional line-commutated inverter methods reported in the literature. The proposed LCI has a simple and robust structure, and it can be easily synchronized with grid thanks to self-latching property of SCRs. Therefore, it is a good alternative for the power transferring from PV panels to the utility grid in grid-connected PV systems.
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.
Modelling and Analysis of Variable Speed Wind Turbines with Induction Generator during Grid Fault
DEFF Research Database (Denmark)
Bolik, Sigrid Mechthild
operators as well as the challenges wind turbine manufacturers such as Vestas faced. Modelling has an important role in the research and development of system changes because it allows many difficult questions to be answered. The varieties of challenges that must be addressed in such modelling are not met...... 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....... The improvement of the large doubly-fed induction generator model as an interface between the mechanical and electrical characteristics of a wind turbine takes a central part in this research process. Chapter 3 presents the development and implementation of a detailed analytical three-phase induction machine...
Mathematical model of an off-grid hybrid solar and wind power generating system
Directory of Open Access Journals (Sweden)
Blasone M.
2014-01-01
Full Text Available The dynamics of an off-grid power generating system, coupled to a storage unit and to household appliances, is described by means of an analytic hydrodynamic analog. Following this analogy, by noticing that the eﬀux rate from a leaking bucket is described, in terms of the liquid content, by Torricelli's formula, we denote as “Torricelli's smart consumer” a user being able to calibrate its energy consumption rate with respect to the energy level in the storage unit as if the hydrodynamic model would strictly apply. Simple solutions to the nonlinear dynamic problem associated to this type of smart consumer are found and generalization to other types of smart consumers are sought.
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...... systems in CPG operation mode are also discussed in this paper. Additionally, the loss of energy is calculated to reveal the viability of the proposed CPG control method. Operation examples of a PV system are presented to show the effectiveness of the CPG control method to unload the distributed grid....... and increased maintenances introduce new obstacles. In view of this concern, the DSOs starts to reduce PV installations in order to avoid an extension of the power infrastructure. Besides, another alternative solution is to limit the maximum feed-in power of the existing PV systems to a certain level. It can...
Generation of Gridded Daily Weather Ensembles for Decision Support in the Argentine Pampas
Verdin, A.; Rajagopalan, B.; Kleiber, W.; Katz, R. W.; Podesta, G. P.
2014-12-01
We introduce a stochastic weather generator for the variables of minimum temperature, maximum temperature, and precipitation occurrence. Temperature variables are modeled in vector autoregressive framework, conditional on precipitation occurrence. Precipitation occurrence arises via a probit model, and both temperature and occurrence are spatially correlatedusing spatial Gaussian processes. Additionally, local climate is included by spatially-varying model coefficients, allowing spatially-evolving relationships between variables. The method is illustrated on a network of stations in the Pampas region of Argentina where nonstationary relationships and historical spatial correlation challenge existing approaches. The covariancestructure of this network of stations is then used to produce daily gridded weather scenarios which can be used to drive hydrologic models. Inclusion of other covariates such as seasonal total precipitation and global climate drivers allows the potential for decadal projections, an increasingly useful tool for decision support.
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.
Directory of Open Access Journals (Sweden)
Md. Raju Ahmed
2014-11-01
Full Text Available Electricity is the most usable form of energy, and one of the most crucial strategic issues for the sustainable development of a country. The projection of demand of electricity is an integral part of the planning process. Severe power crisis compelled the government to enter into contractual agreements for high-cost temporary solution such as rental power and small IPPS, on an emergency basis, most of these are diesel or liquid-fuel based. Load shading is an acute problem for the country. The country is confronting a simultaneous shortage of electricity. However, the country has substantial amount of renewable energy resources. The overview of power generation section of Bangladesh is presented; the potentiality of renewable energy sources in Bangladesh is discussed. Finally, a grid connected hybrid renewable energy system is proposed to overcome the problem of power crisis using sustainable clean energy at rural area.
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...... contributed to enhance their response under faulty and distorted scenarios, and hence to fulfill these requirements. In order to achieve satisfactory results it is necessary to count on accurate and fast grid voltage synchronization algorithms, which are able to work under unbalanced and distorted conditions....... This paper analyzes and compares the synchronization capability of three advanced synchronization systems: the Decoupled Double Synchronous Reference Frame-Phase-Locked Loop, the Dual Second Order Generalized Integgrator- Phase-Locked Loop and the Three-Phase Enhanced Phase-Locked Loop, designed to work...
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.
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.
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
DEFF Research Database (Denmark)
Yao, Jun; Li, Qing; Chen, Zhe
2013-01-01
currents injected to the grid. Furthermore, the respective PI-R controller in the positive synchronous reference frame for the SGSC voltage control and PGSC current control have been developed to achieve precise and rapid regulation of the corresponding components. Finally, the proposed coordinated control......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...... 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...
Macromolecular metallurgy of binary mesocrystals via designed multiblock terpolymers.
Xie, Nan; Liu, Meijiao; Deng, Hanlin; Li, Weihua; Qiu, Feng; Shi, An-Chang
2014-02-26
Self-assembling block copolymers provide access to the fabrication of various ordered phases. In particular, the ordered spherical phases can be used to engineer soft mesocrystals with domain size at the 5-100 nm scales. Simple block copolymers, such as diblock copolymers, form a limited number of mesocrystals. However multiblock copolymers are capable to form more complex mesocrystals. We demonstrate that designed B1AB2CB3 multiblock terpolymers, in which the A- and C-blocks form spherical domains and the packing of these spheres can be controlled by changing the lengths of the middle and terminal B-blocks, self-assemble into various binary mesocrystals with space group symmetries of a large number of binary ionic crystals, including NaCl, CsCl, ZnS, α-BN, AlB2, CaF2, TiO2, ReO3, Li3Bi, Nb3Sn(A15), and α-Al2O3. This approach can be generalized to other terpolymers as well as to tetrapolymers to obtain ternary mesocrystals. Our study provides a new concept of macromolecular metallurgy for producing crystal phases in a mesoscale and thus makes multiblock copolymers a robust platform for the engineering of functional materials.
Multiblock PLS analysis of an industrial pharmaceutical process.
Lopes, J A; Menezes, J C; Westerhuis, J A; Smilde, A K
2002-11-20
The performance of an industrial pharmaceutical process (production of an active pharmaceutical ingredient by fermentation, API) was modeled by multiblock partial least squares (MBPLS). The most important process stages are inoculum production and API production fermentation. Thirty batches (runs) were produced according to an experimental planning. Rather than merging all these data into a single block of independent variables (as in ordinary PLS), four data blocks were used separately (manipulated and quality variables for each process stage). With the multiblock approach it was possible to calculate weights and scores for each independent block. It was found that the inoculum quality variables were highly correlated with API production for nominal fermentations. For the nonnominal fermentations, the manipulations of the fermentation stage explained the amount of API obtained (especially the pH and biomass concentration). Based on the above process analysis it was possible to select a smaller set of variables with which a new model was built. The amount of variance predicted of the final API concentration (cross-validation) for this model was 82.4%. The advantage of the multiblock model over the standard PLS model is that the contributions of the two main process stages to the API volumetric productivity were determined.
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...... is able to inject independently active and reactive power to the grid. The controller provides a proper dynamics decoupled from the grid impedance. Simulation results are provided in order to show the feasibility of the control proposed....
Performance of a grid-connected wind generation system with a robust susceptance controller
Energy Technology Data Exchange (ETDEWEB)
Rahim, A.H.M.A. [Department of Electrical Engineering, K.F. University of Petroleum and Minerals, KFUPM Box 349, Dhahran 31261 (Saudi Arabia); Nowicki, E.P. [Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB (Canada)
2011-01-15
Wind turbine driven induction generators are vulnerable to transient disturbances like wind gusts and low voltages on the system. The fixed capacitor at the generator terminal or the limited support from the grid may not be able to provide the requisite reactive power under these abnormal conditions. This paper presents a susceptance control strategy for a variable speed wound-rotor induction generator which can cater for the reactive power requirement. The susceptance is adjusted through a robust feedback controller included in the terminal voltage driven automatic excitation control circuit. The fixed parameter robust controller design is carried out in frequency domain using multiplicative uncertainty modeling and H{sub {infinity}} norms. The robustness of the controller has been evaluated through optimally tuned PID controllers. Simulation results show that the robust controller can effectively restore normal operation following emergencies like sudden load changes, wind gusts and low voltage conditions. The proposed robust controller has been shown to have adequate fault ride through capabilities in order to be able to meet connection requirements defined by transmission system operators. (author)
Grid synchronization technology for grid converters of wind power generation%风力发电并网变流器同步技术研究
Institute of Scientific and Technical Information of China (English)
范守婷; 王政
2012-01-01
研究了用于风力发电系统电网侧变流器并网同步技术,分析并比较了四种同步技术的工作原理及实现方法,即单同步坐标系软件锁相环(SSRF-SPLL)、增强型锁相环(EPLL)、双同步坐标系解耦软件锁相环(DDSRF-SPLL)以及基于双二阶广义积分器的锁频环(DSOGI-FLL).基于Matlab/Simulink软件平台,分别搭建了这四种并网同步技术的仿真模型,并在理想电网电压和不平衡电网电压情况下,对不同方法运行性能进行了比较.结果表明,SSRF-SPLL控制算法实现最为简单,但其仅在电网电压理想工况下有效.而其他三种方案不仅适合于理想电压工况,而且在电网故障情况下也能对电网电压实现准确监测.而在动态性能方面,EPLL方法性能较差,DDSRF-SPLL较前者好,但是其控制算法复杂.DSOGI-FLL方法在电网频率和相位检测性能方面最好,而且控制算法简单.%This paper studies the grid synchronization techniques for the grid converters of wind power generation. It analyzes and compares the working principles and implementing approaches of four grid synchronizing techniques, namely the single synchronous reference frame software phase locked loop (SSRF-SPLL), enhanced PLL (EPLL), decoupled double synchronous reference frame SPLL(DDSRF-SPLL), and dual second order generalized integrator frequency locked loop (DSOGI-FLL). Based on the Matlab/Simulink platform, the simulation models of the four techniques are established, and their operating performance are compared under both the normal and the faulty grid voltage conditions. The simulation results verify that the SSRF-SPLL method is the simplest, but is effective only when the grid voltage is symmetrical, while the other three methods are not only suitable for the normal grid voltage condition) but also can detect the grid voltage frequency and phase effectively under various faulty grid conditions. Considering the dynamic performance during the generalized
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.
A model combining oscillations and attractor dynamics for generation of grid cell firing
Directory of Open Access Journals (Sweden)
Michael E Hasselmo
2012-05-01
Full Text Available Different models have been able to account for different features of the data on grid cell firing properties, including the relationship of grid cells to cellular properties and network oscillations. This paper describes a model that combines elements of two major classes of models of grid cells: models using interference of oscillations and models using attractor dynamics. This model includes a population of units with oscillatory input representing input from the medial septum. These units are termed heading angle cells because their connectivity depends upon heading angle in the environment as well as the spatial phase coded by the cell. These cells project to a population of grid cells. The sum of the heading angle input results in standing waves of circularly symmetric input to the grid cell population. Feedback from the grid cell population increases the activity of subsets of the heading angle cells, resulting in the network settling into activity patterns that resemble the patterns of firing fields in a population of grid cells. The properties of heading angle cells firing as conjunctive grid-by-head-direction cells can shift the grid cell firing according to movement velocity. The pattern of interaction of oscillations requires use of separate populations that fire on alternate cycles of the net theta rhythmic input to grid cells, similar to recent neurophysiological data on theta cycle skipping in medial entorhinal cortex.
GRIDGEN Version 1.0: a computer program for generating unstructured finite-volume grids
Lien, Jyh-Ming; Liu, Gaisheng; Langevin, Christian D.
2015-01-01
GRIDGEN is a computer program for creating layered quadtree grids for use with numerical models, such as the MODFLOW–USG program for simulation of groundwater flow. The program begins by reading a three-dimensional base grid, which can have variable row and column widths and spatially variable cell top and bottom elevations. From this base grid, GRIDGEN will continuously divide into four any cell intersecting user-provided refinement features (points, lines, and polygons) until the desired level of refinement is reached. GRIDGEN will then smooth, or balance, the grid so that no two adjacent cells, including overlying and underlying cells, differ by more than a user-specified level tolerance. Once these gridding processes are completed, GRIDGEN saves a tree structure file so that the layered quadtree grid can be quickly reconstructed as needed. Once a tree structure file has been created, GRIDGEN can then be used to (1) export the layered quadtree grid as a shapefile, (2) export grid connectivity and cell information as ASCII text files for use with MODFLOW–USG or other numerical models, and (3) intersect the grid with shapefiles of points, lines, or polygons, and save intersection output as ASCII text files and shapefiles. The GRIDGEN program is demonstrated by creating a layered quadtree grid for the Biscayne aquifer in Miami-Dade County, Florida, using hydrologic features to control where refinement is added.
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.
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.
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
Gutzwiller, David; Gontier, Mathieu; Demeulenaere, Alain
2014-11-01
Multi-Block structured solvers hold many advantages over their unstructured counterparts, such as a smaller memory footprint and efficient serial performance. Historically, multi-block structured solvers have not been easily adapted for use in a High Performance Computing (HPC) environment, and the recent trend towards hybrid GPU/CPU architectures has further complicated the situation. This paper will elaborate on developments and innovations applied to the NUMECA FINE/Turbo solver that have allowed near-linear scalability with real-world problems on over 250 hybrid GPU/GPU cluster nodes. Discussion will focus on the implementation of virtual partitioning and load balancing algorithms using a novel meta-block concept. This implementation is transparent to the user, allowing all pre- and post-processing steps to be performed using a simple, unpartitioned grid topology. Additional discussion will elaborate on developments that have improved parallel performance, including fully parallel I/O with the ADIOS API and the GPU porting of the computationally heavy CPUBooster convergence acceleration module. Head of HPC and Release Management, Numeca International.
Energy Technology Data Exchange (ETDEWEB)
Boccard, Julien, E-mail: julien.boccard@unige.ch; Rudaz, Serge
2016-05-12
Many experimental factors may have an impact on chemical or biological systems. A thorough investigation of the potential effects and interactions between the factors is made possible by rationally planning the trials using systematic procedures, i.e. design of experiments. However, assessing factors' influences remains often a challenging task when dealing with hundreds to thousands of correlated variables, whereas only a limited number of samples is available. In that context, most of the existing strategies involve the ANOVA-based partitioning of sources of variation and the separate analysis of ANOVA submatrices using multivariate methods, to account for both the intrinsic characteristics of the data and the study design. However, these approaches lack the ability to summarise the data using a single model and remain somewhat limited for detecting and interpreting subtle perturbations hidden in complex Omics datasets. In the present work, a supervised multiblock algorithm based on the Orthogonal Partial Least Squares (OPLS) framework, is proposed for the joint analysis of ANOVA submatrices. This strategy has several advantages: (i) the evaluation of a unique multiblock model accounting for all sources of variation; (ii) the computation of a robust estimator (goodness of fit) for assessing the ANOVA decomposition reliability; (iii) the investigation of an effect-to-residuals ratio to quickly evaluate the relative importance of each effect and (iv) an easy interpretation of the model with appropriate outputs. Case studies from metabolomics and transcriptomics, highlighting the ability of the method to handle Omics data obtained from fixed-effects full factorial designs, are proposed for illustration purposes. Signal variations are easily related to main effects or interaction terms, while relevant biochemical information can be derived from the models. - Highlights: • A new method is proposed for the analysis of Omics data generated using design of
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)
OTAHAL,THOMAS J.; GALLIS,MICHAIL A.; BARTEL,TIMOTHY J.
2000-06-27
This paper presents an investigation of a technique for using two-dimensional bodies composed of simple polygons with a body decoupled uniform Cmtesian grid in the Direct Simulation Monte Carlo method (DSMC). The method employs an automated grid pre-processing scheme beginning form a CAD geometry definition file, and is based on polygon triangulation using a trapezoid algorithm. A particle-body intersection time comparison is presented between the Icarus DSMC code using a body-fitted structured grid and using a structured body-decoupled Cartesian grid with both linear and logarithmic search techniques. A comparison of neutral flow over a cylinder is presented using the structured body fitted grid and the Cartesian body de-coupled grid.
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)
Do Nguyet Quang; Ong Hang See; Lai Lee Chee; Che Yung Xuen; Shashiteran A/L. Karuppiah
2014-01-01
In smart grid communication implementation, network traffic pattern is one of the main factors that affect the system’s performance. Examining different traffic patterns in smart grid is therefore crucial when analyzing the network performance. Due to the heterogeneous and hybrid nature of smart grid, the type of traffic distribution in the network is still unknown. The traffic that popularly used for simulation and analysis no longer reflects the real traffic in a multi-technology and bi-dir...
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)
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...
DEFF Research Database (Denmark)
Cha, Seung-Tae; Zhao, Haoran; Wu, Qiuwei
2012-01-01
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...
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...
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 o...
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...
a Hadoop-Based Algorithm of Generating dem Grid from Point Cloud Data
Jian, X.; Xiao, X.; Chengfang, H.; Zhizhong, Z.; Zhaohui, W.; Dengzhong, Z.
2015-04-01
Airborne LiDAR technology has proven to be the most powerful tools to obtain high-density, high-accuracy and significantly detailed surface information of terrain and surface objects within a short time, and from which the Digital Elevation Model of high quality can be extracted. Point cloud data generated from the pre-processed data should be classified by segmentation algorithms, so as to differ the terrain points from disorganized points, then followed by a procedure of interpolating the selected points to turn points into DEM data. The whole procedure takes a long time and huge computing resource due to high-density, that is concentrated on by a number of researches. Hadoop is a distributed system infrastructure developed by the Apache Foundation, which contains a highly fault-tolerant distributed file system (HDFS) with high transmission rate and a parallel programming model (Map/Reduce). Such a framework is appropriate for DEM generation algorithms to improve efficiency. Point cloud data of Dongting Lake acquired by Riegl LMS-Q680i laser scanner was utilized as the original data to generate DEM by a Hadoop-based algorithms implemented in Linux, then followed by another traditional procedure programmed by C++ as the comparative experiment. Then the algorithm's efficiency, coding complexity, and performance-cost ratio were discussed for the comparison. The results demonstrate that the algorithm's speed depends on size of point set and density of DEM grid, and the non-Hadoop implementation can achieve a high performance when memory is big enough, but the multiple Hadoop implementation can achieve a higher performance-cost ratio, while point set is of vast quantities on the other hand.
MFE revisited : part 1: adaptive grid-generation using the heat equation
Zegeling, P.A.
2001-01-01
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
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)
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,...
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
, something that would permit the injection of power to the grid during the fault, as the new grid codes demand. A theoretical study of the dynamical behavior of the rotor voltage is also developed, in order to show that the voltage at the rotor terminals required for the control strategy implementation...
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.
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.
The fluid dynamic approach to equidistribution methods for grid generation and adaptation
Energy Technology Data Exchange (ETDEWEB)
Delzanno, Gian Luca [Los Alamos National Laboratory; Finn, John M [Los Alamos National Laboratory
2009-01-01
The equidistribution methods based on L{sub p} Monge-Kantorovich optimization [Finn and Delzanno, submitted to SISC, 2009] and on the deformation [Moser, 1965; Dacorogna and Moser, 1990, Liao and Anderson, 1992] method are analyzed primarily in the context of grid generation. It is shown that the first class of methods can be obtained from a fluid dynamic formulation based on time-dependent equations for the mass density and the momentum density, arising from a variational principle. In this context, deformation methods arise from a fluid formulation by making a specific assumption on the time evolution of the density (but with some degree of freedom for the momentum density). In general, deformation methods do not arise from a variational principle. However, it is possible to prescribe an optimal deformation method, related to L{sub 1} Monge-Kantorovich optimization, by making a further assumption on the momentum density. Some applications of the L{sub p} fluid dynamic formulation to imaging are also explored.
Institute of Scientific and Technical Information of China (English)
Masoud Aliakbar GOLKAR; Amin HAJIZADEH
2009-01-01
This paper presents a control strategy of a hybrid fuel cell/battery distributed generation (HDG) system in distribution systems. The overall structure of the HDG system is given, dynamic models for the solid oxide fuel cell (SOFC) power plant,battery bank and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units and fuel cell to control the power flow from the hybrid power plant to the utility grid are presented. To distribute the power between the fuel cell power plant and the battery energy storage, a neuro-fuzzy controller has been developed. Also, for controlling the active and reactive power independently in distribution systems, the current control strategy based on two fuzzy logic controllers has been presented. A Matlab/Simulink simulation model is developed for the HDG system by combining the individual component models and their controllers. Simulation results show the overall system performance including load-following and power management of the HDG system.
Control and Protection in Low Voltage Grid with Large Scale Renewable Electricity Generation
DEFF Research Database (Denmark)
Mustafa, Ghullam
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...... of the wind speed and solar irradiation fluctuations are tackled. The CIGRE Low Voltage (LV) network comprising two solar PV generating units of 3 kW and 4 kW, one 5.5 kW fixed-pitch fix speed WTG and two battery units each producing energy of 30kwh and 21kwh has been chosen for the study. The study...... the distribution system and the transmission grid has been proposed here. The algorithms, models and methodologies developed during this research study have been tested in a CIGRE low voltage distribution network. The simulation results show that they are able to correctly identify the states of the distribution...
Institute of Scientific and Technical Information of China (English)
Heng NIAN; Yi-peng SONG
2015-01-01
This paper presents a multiple target implementation technique for a doubly fed induction generator (DFIG) under unbalanced and distorted grid voltage based on direct power control (DPC). Based on the mathematical model of DFIG under unbalanced and distorted voltage, the proportional and integral (PI) regulator is adopted to regulate the DFIG average active and reactive powers, while the vector PI (VPI) resonant regulator is used to achieve three alternative control targets: (1) balanced and sinusoidal stator current; (2) smooth instantaneous stator active and reactive powers; (3) smooth electromagnetic torque and instantaneous stator reactive power. The major advantage of the proposed control strategy over the conventional method is that neither negative and harmonic sequence decomposition of grid voltage nor complicated control reference calculation is required. The insensitivity of the proposed control strategy to DFIG parameter deviation is analyzed. Finally, the DFIG experimental system is developed to validate the availability of the proposed DPC strategy under unbalanced and distorted grid voltage.
Control strategy for a Doubly-Fed Induction Generator feeding an unbalanced grid or stand-alone load
Energy Technology Data Exchange (ETDEWEB)
Pena, Ruben [University of Concepcion, Electrical Engineering Department, P.O. Box 160-C, Concepcion (Chile); Cardenas, Roberto; Escobar, Enrique [University of Magallanes, Electrical Engineering Department, P.O. Box 113-D, Punta Arenas (Chile); Clare, Jon; Wheeler, Pat [University of Nottingham, School of Electrical and Electronic Engineering, Nottingham NG7 2RD (United Kingdom)
2009-02-15
In this paper, the control systems for the operation of a Doubly-Fed Induction Generator (DFIG), feeding an unbalanced grid/stand-alone load, are presented. The scheme uses two back-to-back PWM inverters connected between the stator and the rotor, namely the rotor side and stator side converters respectively. The stator current and voltage unbalances are reduced or eliminated by injecting compensation currents into the grid/load using the stator side converter. The proposed control strategy is based on two revolving axes rotating synchronously at {+-}{omega}{sub e}. From these axes, the d-q components of the negative and positive-sequence currents, in the stator and grid/load, are obtained. The scheme compensates the negative-sequence currents in the grid/load by supplying negative-sequence currents via the stator side converter. Experimental results obtained from a 2-kW experimental prototype are presented and discussed in this work. The proposed control methodology is experimentally validated for stand-alone and weak grid-connected conditions and the results show the excellent performance of the strategy used. (author)
交互式棱柱网格生成方法%Interactive Prismatic Grid Generation Method
Institute of Scientific and Technical Information of China (English)
孙岩
2016-01-01
针对流动数值模拟中边界层区域棱柱网格生成与修改困难的问题, 提出一种基于物面边界约束的交互式棱柱网格生成方法. 该方法交互生成物面边界点的空间推进面网格; 将边界点空间推进面网格的每层网格点看成边界网格点运动得到, 计算对应的边界网格点位移; 利用径向基函数插值将边界网格点位移光滑传递给内部网格点, 获得内部网格点的空间推进网格; 建立所有网格点之间的连接关系, 构造棱柱网格单元. 基于V型槽、飞机机头等外形对文中方法进行测试, 并对该方法存在的一些问题进行了讨论; 利用该方法生成一个大展弦比翼身组合体模型的棱柱/四面体混合计算网格, 并在 PHENGLEI 计算平台上进行了数值模拟, 结果表明, 该方法能够生成高质量的粘性棱柱网格.%An interactive method for prismatic grid generation based on surface boundary constraint is presented to solve the problem that it is hard to generate and modify prismatic grid in boundary layer in numerical simula-tion of fluid dynamics. First, the space advancing grid of surface boundary nodes is generated interactively in present method; second, the displacement of surface boundary nodes is calculated based on the thought that each layer of space advancing grid is acquired through motion of surface boundary nodes; third, the space advancing grid of surface interior nodes is generated by smoothly propagating the displacement of surface boundary nodes to surface interior nodes through the use of radial basis function interpolation; at last, the prismatic grid cells are created through establishing connections of all grid nodes. The present method is tested based on V-shape groove and airplane head, and some problems in the present method are discussed; the present method is also used to generate a prismatic/tetrahedral hybrid computational grid for a high respect ratio wing-body model; the hybrid
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.
Solving the linear radiation problem using a volume method on an overset grid
DEFF Research Database (Denmark)
Read, Robert; Bingham, Harry B.
2012-01-01
with analytical solutions for several test cases. The dynamic behaviour of a cylinder and barge on variable bathymetry has been investigated on a multi-block grid in two dimensions. Simulations have been performed to evaluate the induced flow field and radiation forces generated by these bodies in response...... of numerical results with established analytical solutions. The linear radiation problem is considered in this paper. A two-dimensional computational tool has been developed to calculate the force applied to a floating body of arbitrary form in response to a prescribed displacement. Fourier transforms...... of the time-dependent displacement and force are applied, and the ratio of the resulting signals used to determine the radiation added mass and damping of the body as a function of frequency. The present software implementation has been validated by comparing numerical results from the linear model...
Grid cells generate an analog error-correcting code for singularly precise neural computation.
Sreenivasan, Sameet; Fiete, Ila
2011-09-11
Entorhinal grid cells in mammals fire as a function of animal location, with spatially periodic response patterns. This nonlocal periodic representation of location, a local variable, is unlike other neural codes. There is no theoretical explanation for why such a code should exist. We examined how accurately the grid code with noisy neurons allows an ideal observer to estimate location and found this code to be a previously unknown type of population code with unprecedented robustness to noise. In particular, the representational accuracy attained by grid cells over the coding range was in a qualitatively different class from what is possible with observed sensory and motor population codes. We found that a simple neural network can effectively correct the grid code. To the best of our knowledge, these results are the first demonstration that the brain contains, and may exploit, powerful error-correcting codes for analog variables.
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.
A New Method of Reference Signal Generation Applied To UPQC-PHEV For Grid Integration of WECS-SCIG
Directory of Open Access Journals (Sweden)
Girish B M
2017-02-01
Full Text Available In this paper a new reference signal generation control technique is proposed for integration of Unified Power Quality Conditioner (UPQC with Plug-in Hybrid Electric Vehicle (PHEV for overcoming voltage sag and other voltage fault conditions on wind farms which is connected to grid. The interaction of wind generators and grid causes increased short circuit current which leads to instability during fault conditions. The new control technique which generate reference signals for series active power filter (Series APF and shunt active power filter (Shunt APF of UPQC by using PHEV as an Energy Storage System (ESS which will take care of all types of voltage faults occurred in the system and provide energy storage to DC link between Series APF and Shunt APF parts of UPQC. The control scheme proposed also maintains transaction of active and reactive power of Wind Energy Conversion System based on Squirrel Cage Induction Generators (WECS-SCIG and grid. The fuzzy logic provides fast and dynamic response to clear faults occurred in the system.
Bilgili, Ata; Smith, Keston W.; Lynch, Daniel R.
2006-06-01
A brief summary of Delaunay unstructured triangular grid refinement algorithms, including the recent "off-centers" method, is provided and mesh generation requirements that are imperative to meet the criteria of the circulation modeling community are defined. A Matlab public-domain two-dimensional (2-D) mesh generation package (BatTri) based on these requirements is then presented and its efficiency shown through examples. BatTri consists of a graphical mesh editing interface and several bathymetry-based refinement algorithms, complemented by a set of diagnostic utilities to check and improve grid quality. The final output mesh node locations, node depths and element incidence list are obtained starting from only a basic set of bathymetric data. This simple but efficient setup allows fast interactive mesh customization and provides circulation modelers with problem-specific flexibility while satisfying the usual requirements on mesh size and element quality. A test of the "off-centers" method performed on 100 domains with randomly generated coastline and bathymetry shows an overall 25% reduction in the number of elements with only slight decrease in element quality. More importantly, this shows that BatTri is easily upgradeable to meet the future demands by the addition of new grid generation algorithms and Delaunay refinement schemes as they are made available.
Olynick, David P.; Hassan, H. A.; Moss, James N.
1988-01-01
A grid generation and adaptation procedure based on the method of transfinite interpolation is incorporated into the Direct Simulation Monte Carlo Method of Bird. In addition, time is advanced based on a local criterion. The resulting procedure is used to calculate steady flows past wedges and cones. Five chemical species are considered. In general, the modifications result in a reduced computational effort. Moreover, preliminary results suggest that the simulation method is time step dependent if requirements on cell sizes are not met.
Streamline integration as a method for two-dimensional elliptic grid generation
Wiesenberger, Matthias; Einkemmer, Lukas
2016-01-01
We propose a new numerical algorithm to construct a structured numerical grid of a doubly connected domain that is bounded by the contour lines of a given function. It is based on the integration of the streamlines of the two vector fields that form the basis of the coordinate system. These vector fields are either built directly from the given function or from the solution of a suitably chosen elliptic equation (which can be solved once an initial grid has been constructed). We are able to construct conformal, orthogonal and curvilinear coordinates. The method is parallelizable and the metric elements can be computed with high accuracy. Furthermore, it is easy to implement as only the integration of well-behaved ordinary differential equations and the inversion of a linear elliptic equation are required. All our grids are orthogonal to the boundary of the domain, which is the major advantage over previously suggested grids. We assess the quality of our grids with the solution of an elliptic equation and the ...
Generalized detection of a turbulent front generated by an oscillating grid
Holzner, Markus; Liberzon, Alexander; Guala, Michele; Tsinober, Arkady; Kinzelbach, Wolfgang
2006-11-01
This report presents experimental results on the propagation of a turbulent front induced by an oscillating grid starting from rest. The purpose of this preliminary investigation is to implement and validate detection methods of the turbulent/non-turbulent interface, which are based on flow measurements (velocity and vorticity) and scalar intensity, for oscillating grid turbulence. This is done using particle image velocimetry (PIV) and fluorescent dye visualization, separately. The results of both techniques describe the spreading of the turbulent front, confirming the known dependency of the front location, H, on time, t. It is demonstrated, that the level-based detection of a turbulent front can be applied to an unsteady flow, such as grid turbulence advancing into a fluid at rest.
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...
Terasaka, K; Yoshimura, S; Kato, Y; Furuta, K; Aramaki, M; Morisaki, T; Tanaka, M Y
2014-11-01
High-impedance Wire Grid (HIWG) detector has been developed to study spatiotemporal behavior of a hot electron clump generated in an electron cyclotron resonance (ECR) plasma. By measuring the floating potentials of the wire electrodes, and generating structure matrix made of geometrical means of the floating potentials, the HIWG detector reconstructs the spatial distribution of high-temperature electron clump at an arbitrary instant of time. Time slices of the spike event in floating potential revealed the growth and decay process of a hot spot occurs in an ECR plasma.
Institute of Scientific and Technical Information of China (English)
穆钢; 崔杨; 刘嘉; 严干贵; 郑太一; 徐广鑫
2013-01-01
随着大规模风电场的建设和并网,电源(风电)与电网之间的尖锐矛盾逐渐显现.一些电网由于输电能力的限制,导致部分新建机组不能并网或已投运风电机组弃风,这种电网被定义为有待用风电机组且传输能力受限的电网.对于电网调度员来说,只有入网风电机组的装机容量是可调度的.由于风电的波动特性,即使知道用于传输风电的电网传输空间,也难以决定应该接入多少风电机组以充分利用电网传输空间.文中通过对风电波动特性的分析,提出了源网协调调度方法.该方法可在保证电网安全的条件下,最大限度地利用电网用于传输风电的空间,以提高电网和风能利用率.%With the construction and incorporation of large-scale wind farms,the contradiction between the source (wind generators) and the grid is highlighted increasingly.Due to grid constraints,some installed wind generators cannot be incorporated into grids,and the wind curtailment happens in some commissioning wind generators.This grid can be defined as "a transmission constrained grid with surplus wind generators".For a grid dispatcher,only the specific capacity of wind generators can be dispatched.Even if the grid transmission space used to transmit wind power is known,due to the fluctuation characteristics of wind power,it is difficult to determine how much specific capacity of wind generators is suitable for sufficiently utilizing this space.This paper proposes a method to coordinate the source and the grid by the fluctuation characteristic analysis of wind power.The method can maximize the grid transmission space for wind power to improve the utilization of grids and wind energy while ensuring the grid security.
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
of PV panels, ii) guaranteeing a power factor unit in the side of the grid, iii) ensuring the global asymptotic stability of the closed loop system. Based on the nonlinear model of the whole system, the controller is carried out using a Lyapunov approach. It is formally shown, using a theoretical...
Control strategies of grid-side PWM inverter for distributed power generation systems
DEFF Research Database (Denmark)
Lar, I.; Radulescu, M. M.; Ritchie, Ewen;
2011-01-01
A comparison between two predictive control methods of grid side inverter, Robust Dead Beat control and Robust Forward control is made. The report contains both simulations and experimental test wich were made at a reduced scale (2.2 kW). The harmonic monitoring has shown that Dead Beat control p...
NREL Controllable Grid Interface for Testing MW-Scale Wind Turbine Generators (Poster)
Energy Technology Data Exchange (ETDEWEB)
McDade, M.; Gevorgian, V.; Wallen, R.; Erdman, W.
2013-04-01
In order to understand the behavior of wind turbines experiencing grid disturbances, it is necessary to perform a series of tests and accurate transient simulation studies. The latest edition of the IEC 61400-21 standard describes methods for such tests that include low voltage ride-through (LVRT), active power set-point control, ramp rate limitations, and reactive power capability tests. The IEC methods are being widely adopted on both national and international levels by wind turbine manufacturers, certification authorities, and utilities. On-site testing of wind turbines might be expensive and time consuming since it requires both test equipment transportation and personnel presence in sometimes remote locations for significant periods of time because such tests need to be conducted at certain wind speed and grid conditions. Changes in turbine control software or design modifications may require redoing of all tests. Significant cost and test-time reduction can be achieved if these tests are conducted in controlled laboratory environments that replicate grid disturbances and simulation of wind turbine interactions with power systems. Such testing capability does not exist in the United States today. An initiative by NREL to design and construct a 7-MVA grid simulator to operate with the existing 2.5 MW and new upcoming 5-MW dynamometer facilities will fulfill this role and bring many potential benefits to the U.S. wind industry with the ultimate goal of reducing wind energy integration costs.
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 compu
Introduction to grid computing
Magoules, Frederic; Tan, Kiat-An; Kumar, Abhinit
2009-01-01
A Thorough Overview of the Next Generation in ComputingPoised to follow in the footsteps of the Internet, grid computing is on the verge of becoming more robust and accessible to the public in the near future. Focusing on this novel, yet already powerful, technology, Introduction to Grid Computing explores state-of-the-art grid projects, core grid technologies, and applications of the grid.After comparing the grid with other distributed systems, the book covers two important aspects of a grid system: scheduling of jobs and resource discovery and monitoring in grid. It then discusses existing a
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.
Tunable elastin-mimetic multiblock hybrid copolymers for biomedical applications
Grieshaber, Sarah Elizabeth
Elastin-mimetic hybrid polymers (EMHPs) have been developed to capture the multiblock molecular architecture of tropoelastin, allowing tunability in chemical, structural, biological, and mechanical properties. Multiblock EMHPs containing flexible synthetic segments were first synthesized via step growth polymerization of diazido-poly(ethylene glycol) (PEG) and alkyne-terminated AKA3KA (K = lysine, A = alanine) (AK2) peptide employing copper (I)-catalyzed alkyne-azide cycloaddition reaction (CuAAC, or orthogonal click chemistry). Covalent crosslinking of the EMHPs with hexamethylene diisocyanate (HMDI) through the lysine residues in the peptide domain afforded an elastomeric hydrogel (xEMHP) with a compressive modulus of 0.12 +/- 0.018 MPa when hydrated. xEMHPs exhibited minimal cytotoxicity to primary porcine vocal fold fibroblasts. The modular nature of the synthesis allowed facile adjustment of the peptide sequence to modulate the structural and the biological properties of EMHPs. Thus, EMHPs containing integrin-binding peptides were constructed using di-azido-PEG and an alkyne-terminated AK2 peptide with a terminal, integrin-binding GRGDSP domain via the step growth click coupling reaction. Hydrogels formed by covalent crosslinking of the RGD-containing EMHPs had a compressive modulus of 1.06 +/- 0.1MPa when hydrated. Neonatal human dermal fibroblasts (NHDFs) were able to adhere to the hydrogels within 1 h, and to spread and develop F-actin filaments 24 h post seeding. NHDF proliferation was only observed on hydrogels containing RGD domains, demonstrating the importance of integrin engagement for cell growth and the potential use of these EMHPs as tissue engineering scaffolds. The tunability of the EMHP system was further investigated by development of self-assembling, pH-responsive multiblock polymers composed of alternating domains of poly(acrylic acid) (PAA) and a peptide derived from the hydrophobic domains of elastin with the sequence (VPGVG)2 (VG2). The
Crook, Andrew J.; Delaney, Robert A.
1991-01-01
A procedure is studied for generating three-dimensional grids for advanced turbofan engine fan section geometries. The procedure constructs a discrete mesh about engine sections containing the fan stage, an arbitrary number of axisymmetric radial flow splitters, a booster stage, and a bifurcated core/bypass flow duct with guide vanes. The mesh is an h-type grid system, the points being distributed with a transfinite interpolation scheme with axial and radial spacing being user specified. Elliptic smoothing of the grid in the meridional plane is a post-process option. The grid generation scheme is consistent with aerodynamic analyses utilizing the average-passage equation system developed by Dr. John Adamczyk of NASA Lewis. This flow solution scheme requires a series of blade specific grids each having a common axisymmetric mesh, but varying in the circumferential direction according to the geometry of the specific blade row.
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.)
Energy Technology Data Exchange (ETDEWEB)
Sahan, Benjamin
2010-11-13
Power electronic converters for adapting the volatile photovoltaic dc generators to the relatively stiff requirements of the distribution and transmission grids are rapidly gaining importance. The inverter technology is principally based on two types of concepts: Voltage Source Inverters and Current Source Inverters. Especially self-commutated Current Source Inverters did not achieve significance until today. This raises the question of the basic criteria which could either prevent the use of those inverters or even promote them. The two basic concepts are first subjected to a systematic comparison. For this purpose dimensionless benchmark factors are used. At the same time different exemplarily setups are described and documented by measurements. A Current Source Inverter system for integration into high-voltage PV modules is presented, which features a single-stage approach and thus achieves a very high efficiency and compact dimensions. Moreover, new types of inverter topology are considered with indirect (controlled) current dc links. Combining low frequency with only a very few high frequency switches opens up new possibilities for power electronics design, e.g. the use of Normally-on SiC-JFETs. This, however, contradicts the common paradigm to only use normally-off switches in power electronics. Apart from this, new approaches for the use of robust and cost efficient thyristor circuits are presented. These are enabled to fulfill the new grid codes even with injected leading reactive power into the electricity grid which contributes to its stability. (orig.)
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.
Energy Technology Data Exchange (ETDEWEB)
Schnyder, G.; Mauchle, P. [Schnyder Ingenieure AG, Huenenberg (Switzerland); Hoeckel, M.; Luschinger, P. [Berner Fachhochschule (HTI Biel), Biel (Switzerland); Firtz, O.; Haederli, C.; Jaggy, E. [ABB Schweiz AG, Corporate Research, Baden-Daettwil (Switzerland)
2003-07-01
This first part of a ten-part final report for the Swiss Federal Office of Energy (SFOE) presents the main findings of 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 analyses, based on simulation calculations on specific medium and low voltage grids, are discussed. The results of simulations are discussed that involved grids partly fed by already existing distributed power plants and, additionally, by a varying number of further distributed production units. In addition to an intensive evaluation of the normal grid status, considerations and analyses were carried out concerning isolated operation ('islanding') and transitions from one grid status to another. The findings obtained from these studies are discussed, including effects such as voltage-fluctuation caused by power flow, harmonics caused by inverters and grid resonance effects.
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.
Directory of Open Access Journals (Sweden)
Lucas Cuadra
2017-07-01
Full Text Available In this work, we describe an approach that allows for optimizing the structure of a smart grid (SG with renewable energy (RE generation against abnormal conditions (imbalances between generation and consumption, overloads or failures arising from the inherent SG complexity by combining the complex network (CN and evolutionary algorithm (EA concepts. We propose a novel objective function (to be minimized that combines cost elements, related to the number of electric cables, and several metrics that quantify properties that are beneficial for SGs (energy exchange at the local scale and high robustness and resilience. The optimized SG structure is obtained by applying an EA in which the chromosome that encodes each potential network (or individual is the upper triangular matrix of its adjacency matrix. This allows for fully tailoring the crossover and mutation operators. We also propose a domain-specific initial population that includes both small-world and random networks, helping the EA converge quickly. The experimental work points out that the proposed method works well and generates the optimum, synthetic, small-world structure that leads to beneficial properties such as improving both the local energy exchange and the robustness. The optimum structure fulfills a balance between moderate cost and robustness against abnormal conditions. Our approach should be considered as an analysis, planning and decision-making tool to gain insight into smart grid structures so that the low level detailed design is carried out by using electrical engineering techniques.
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)
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.
Murthy, S. S.; Singh, Bhim; Sandeep, Vuddanti
2016-06-01
This paper deals with the design and development of a novel single-phase two winding self-excited squirrel cage induction generator (SEIG) for off-grid renewable energy based power generation. The principles underlying the design process and experience with SPEED design tool are described to design a 5 kW, 50 Hz, 230 V, 4 pole single phase AC generator. All possible configurations to reduce harmonic components of induced e.m.f. are attempted for desired performance and to get an optimum design keeping in view the manufacturing constraints. The development of a prototype based on this design has been completed with the help of an industry. Typical test results on the prototype are presented to demonstrate its performance. Computed results are obtained with a design based computational procedure for performance analysis and a critical comparison is made with test results.
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.
Structure-Property Relationships of Poly(lactide)-based Triblock and Multiblock Copolymers
Panthani, Tessie Rose
Replacing petroleum-based plastics with alternatives that are degradable and synthesized from annually renewable feedstocks is a critical goal for the polymer industry. Achieving this goal requires the development of sustainable analogs to commodity plastics which have equivalent or superior properties (e.g. mechanical, thermal, optical etc.) compared to their petroleum-based counterparts. This work focuses on improving and modulating the properties of a specific sustainable polymer, poly(lactide) (PLA), by incorporating it into triblock and multiblock copolymer architectures. The multiblock copolymers in this work are synthesized directly from dihydroxy-terminated triblock copolymers by a simple step-growth approach: the triblock copolymer serves as a macromonomer and addition of stoichiometric quantities of either an acid chloride or diisocyanate results in a multiblock copolymer. This work shows that over wide range of compositions, PLA-based multiblock copolymers have superior mechanical properties compared to triblock copolymers with equivalent chemical compositions and morphologies. The connectivity of the blocks within the multiblock copolymers has other interesting consequences on properties. For example, when crystallizable poly(L-lactide)-based triblock and multiblock copolymers are investigated, it is found that the multiblock copolymers have much slower crystallization kinetics. Additionally, the total number of blocks connected together is found to effect the linear viscoelastic properties as well as the alignment of lamellar domains under uniaxial extension. Finally, the synthesis and characterization of pressure-sensitive adhesives based upon renewable PLA-containing triblock copolymers and a renewable tackifier is detailed. Together, the results give insight into the effect of chain architecture, composition, and morphology on the mechanical behavior, thermal properties, and rheological properties of PLA-based materials.
Directory of Open Access Journals (Sweden)
H. Zhou
2011-10-01
Full Text Available A tsunami generated by large-volume landslide can propagate across the ocean and flood communities around the basin. The evolution of landslide-generated tsunamis is affected by the effects of frequency dispersion and involves processes of different temporal and spacial scales. In this paper, we develop a numerical approach employing the weakly nonlinear and fully nonlinear Boussinesq-type theories and nested computational grids. The propagation in a large domain is simulated with the weakly nonlinear model in a geographical reference frame. The nearshore wave evolution and runup are computed with the fully nonlinear model. Nested grids are employed to zoom simulations from larger to smaller domains at successively increasing resolutions. The models and the nesting scheme are validated for theoretical analysis, laboratory experiments and a historical tsunami event. By applying this approach, we also investigate the potential tsunami impact on the US east coast due to the possible landslide on La Palma Island. The scenario employed in this study represents an event of extremely low probability.
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.
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.
Finite Macro-Element Mesh Deformation in a Structured Multi-Block Navier-Stokes Code
Bartels, Robert E.
2005-01-01
A mesh deformation scheme is developed for a structured multi-block Navier-Stokes code consisting of two steps. The first step is a finite element solution of either user defined or automatically generated macro-elements. Macro-elements are hexagonal finite elements created from a subset of points from the full mesh. When assembled, the finite element system spans the complete flow domain. Macro-element moduli vary according to the distance to the nearest surface, resulting in extremely stiff elements near a moving surface and very pliable elements away from boundaries. Solution of the finite element system for the imposed boundary deflections generally produces smoothly varying nodal deflections. The manner in which distance to the nearest surface has been found to critically influence the quality of the element deformation. The second step is a transfinite interpolation which distributes the macro-element nodal deflections to the remaining fluid mesh points. The scheme is demonstrated for several two-dimensional applications.
Forecasting Wind and Solar Generation: Improving System Operations, Greening the Grid
Energy Technology Data Exchange (ETDEWEB)
Tian; Tian; Chernyakhovskiy, Ilya
2016-01-01
This document discusses improving system operations with forecasting 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.
Multi-block methods in multivariate process control
DEFF Research Database (Denmark)
Kohonen, J.; Reinikainen, S.P.; Aaljoki, K.
2008-01-01
In chemometric studies all predictor variables are usually collected in one data matrix X. This matrix is then analyzed by PLS regression or other methods. When data from several different sub-processes are collected in one matrix, there is a possibility that the effects of some sub-processes may...... vanish. If there is, for instance, mechanic data from one process and spectral data from another, the influence of the mechanic sub-process may not be detected. An application of multi-block (MB) methods, where the X-data are divided into several data blocks is presented in this study. By using MB...... methods the effect of a sub-process can be seen and an example with two blocks, near infra-red, NIR, and process data, is shown. The results show improvements in modelling task, when a MB-based approach is used. This way of working with data gives more information on the process than if all data...
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.
Interactions of Copepods with Fractal-Grid Generated Turbulence based on Tomo-PIV and 3D-PTV
Sun, Zhengzhong; Krizan, Daniel; Longmire, Ellen
2014-11-01
A copepod escapes from predation by sensing fluid motion caused by the predator. It is thought that the escape reaction is elicited by a threshold value of the maximum principal strain rate (MPSR) in the flow. The present experimental work attempts to investigate and quantify the MPSR threshold value. In the experiment, copepods interact with turbulence generated by a fractal grid in a recirculating channel. The turbulent flow is measured by time-resolved Tomo-PIV, while the copepod motion is tracked simultaneously through 3D-PTV. Escape reactions are detected based on copepod trajectories and velocity vectors, while the surrounding hydrodynamic information is retrieved from the corresponding location in the 3D instantaneous flow field. Measurements are performed at three locations downstream of the fractal grid, such that various turbulence levels can be achieved. Preliminary results show that the number of escape reactions decreases at locations with reduced turbulence levels, where shorter jump distances and smaller change of swimming orientation are exhibited. Detailed quantitative results of MPSR threshold values and the dynamics of copepod escape will be presented. Supported by NSF-IDBR Grant #0852875.
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.
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.
DEFF Research Database (Denmark)
Li, H.; Zhao, B.; Yang, C.
2011-01-01
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...... electromagnetic transient models of a SCIG, the transient behaviors of the wind turbine generation system during a three-phase fault are simulated and compared with the traditional models. Secondly, in order to quickly estimate the transient stability limit of the wind turbine generation system, a direct method...... 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...
DEFF Research Database (Denmark)
Yang, Yongheng; Enjeti, Prasad; Blaabjerg, Frede;
2013-01-01
-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......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...... 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...
DEFF Research Database (Denmark)
Golestan, Saeed; Guerrero, Josep M.; Abusorrah, Abdullah
2017-01-01
The quadrature signal generation based phase-locked loops (QSG-PLLs) are highly popular for synchronization purposes in single-phase systems. The main difference among these PLLs often lies in the technique they use for creating the fictitious quadrature component. One of the easiest QSG approaches...... is delaying the original single-phase signal by a quarter of a cycle. The PLL with such QSG technique is often called the transfer delay based PLL (TD-PLL). The TD-PLL benefits from a simple structure, rather fast dynamic response, and a good detection accuracy when the grid frequency is at its nominal value......, but it suffers from a phase offset error and double frequency oscillatory error in the estimated phase and frequency in the presence of frequency drifts. In this paper, a simple yet effective approach to remove the aforementioned errors of the TD-PLL is proposed. The resultant PLL structure is called...
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...
Camera, Corrado; Bruggeman, Adriana; Hadjinicolaou, Panos; Pashiardis, Stelios; Lange, Manfred
2014-05-01
High-resolution gridded daily datasets are essential for natural resource management and the analysis of climate changes and their effects. This study aimed to create gridded datasets of daily precipitation and daily minimum and maximum temperature, for the future (2020-2050). The horizontal resolution of the developed datasets is 1 x 1 km2, covering the area under control of the Republic of Cyprus (5.760 km2). The study is divided into two parts. The first consists of the evaluation of the performance of different interpolation techniques for daily rainfall and temperature data (1980-2010) for the creation of the gridded datasets. Rainfall data recorded at 145 stations and temperature data from 34 stations were used. For precipitation, inverse distance weighting (IDW) performs best for local events, while a combination of step-wise geographically weighted regression and IDW proves to be the best method for large scale events. For minimum and maximum temperature, a combination of step-wise linear multiple regression and thin plate splines is recognized as the best method. Six Regional Climate Models (RCMs) for the A1B SRES emission scenario from the EU ENSEMBLE project database were selected as sources for future climate projections. The RCMs were evaluated for their capacity to simulate Cyprus climatology for the period 1980-2010. Data for the period 2020-2050 from the three best performing RCMs were downscaled, using the change factors approach, at the location of observational stations. Daily time series were created with a stochastic rainfall and temperature generator. The RainSim V3 software (Burton et al., 2008) was used to generate spatial-temporal coherent rainfall fields. The temperature generator was developed in R and modeled temperature as a weakly stationary process with the daily mean and standard deviation conditioned on the wet and dry state of the day (Richardson, 1981). Finally gridded datasets depicting projected future climate conditions were
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)
Institute of Scientific and Technical Information of China (English)
Yong Kiel Sung; Yong Joo Kim; Sung Wan Kim
1999-01-01
The synthesis and characterization of amphiphilic copolymers of poly(dimethyl siloxane)(PDMS),poly(ethylene oxide)(PEO), and heparin(Hep) were investigated. These multiblock copolymers were identified using 1H-NMR, FTIR, end group analysis, and sulfur elemental analysis. The multiblock copolymers were characterized by using DSC and X-ray diffractometry. The glass transition temperature,crystalline melting characteristics, annealing effect, and cold crystallization of the block copolymers were determined by DSC. The crystallinity of the block copolymers was also determined by X-ray diffraction method.
Energy Technology Data Exchange (ETDEWEB)
Macedo, Wilson Negrao; Ziles, Roberto [Universidade de Sao Paulo (USP), SP (Brazil). Programa Interunidades de Pos-Graduacao em Energia. Lab. de Sistemas Fotovoltaicos], e-mail: wnmacedo@iee.usp.br, e-mail: Zilles@iee.usp.br
2004-07-01
In this work an approach of the particularities of the distributed generation with photovoltaic systems as well as the interaction of these systems with the electric grid is done, base aspects related to your operation and the several forms of conceive a grid connected photovoltaic system (SFCR) are taking into accounted. It shows through the different forms of consolidate the connection with the electric grid, which besides the inverter be the key element of this kind system, SFCRs' Interaction with the electric grid is enough influenced by the incentive policies or given treatment for this application in each place in particular. That aspect can influence in the demand by the owner of the installation, mostly if this is a captive consumer that now becomes an electric power producer. (author)
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.
Automated volumetric grid generation for finite element modeling of human hand joints
Energy Technology Data Exchange (ETDEWEB)
Hollerbach, K.; Underhill, K. [Lawrence Livermore National Lab., CA (United States); Rainsberger, R. [XYZ Scientific Applications, Inc., Livermore, CA (United States)
1995-02-01
We are developing techniques for finite element analysis of human joints. These techniques need to provide high quality results rapidly in order to be useful to a physician. The research presented here increases model quality and decreases user input time by automating the volumetric mesh generation step.
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. ...
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...... under such conditions. Its response will be analyzed with respect the synchronization needs that can be extracted from the standards....
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.
Energy Technology Data Exchange (ETDEWEB)
Hoeffler, Felix [Koeln Univ. (Germany). Energiewirtschaftliches Inst.; Max-Planck-Institute for Research on Collective Goods, Bonn (Germany); Wambach, Achim [Cologne Univ. (Germany). Dept. of Economics
2013-06-15
Liberalization of network industries frequently separates the network from the other parts of the industry. This is important in particular for the elec- tricity industry where private firms invest into generation facilities, while network investments usually are controlled by regulators. We discuss two regulatory regimes. First, the regulator can only decide on the network extension. Second, she can additionally use a ''capacity market'' with payments contingent on private generation investment. For the first case, we find that even absent asymmetric information, a lack of regulatory commitment can cause inefficiently high or inefficiently low investments. For the second case, we develop a standard handicap auction which implements the first best under asymmetric information, if there are no shadow costs of public funds. With shadow costs, no simple mechanism can implement the second best outcome.
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.
Structured grid technology to enable flow simulation in an integrated system environment
Remotigue, Michael Gerard
An application-driven Computational Fluid Dynamics (CFD) environment needs flexible and general tools to effectively solve complex problems in a timely manner. In addition, reusable, portable, and maintainable specialized libraries will aid in rapidly developing integrated systems or procedures. The presented structured grid technology enables the flow simulation for complex geometries by addressing grid generation, grid decomposition/solver setup, solution, and interpretation. Grid generation is accomplished with the graphical, arbitrarily-connected, multi-block structured grid generation software system (GUM-B) developed and presented here. GUM-B is an integrated system comprised of specialized libraries for the graphical user interface and graphical display coupled with a solid-modeling data structure that utilizes a structured grid generation library and a geometric library based on Non-Uniform Rational B-Splines (NURBS). A presented modification of the solid-modeling data structure provides the capability for arbitrarily-connected regions between the grid blocks. The presented grid generation library provides algorithms that are reliable and accurate. GUM-B has been utilized to generate numerous structured grids for complex geometries in hydrodynamics, propulsors, and aerodynamics. The versatility of the libraries that compose GUM-B is also displayed in a prototype to automatically regenerate a grid for a free-surface solution. Grid decomposition and solver setup is accomplished with the graphical grid manipulation and repartition software system (GUMBO) developed and presented here. GUMBO is an integrated system comprised of specialized libraries for the graphical user interface and graphical display coupled with a structured grid-tools library. The described functions within the grid-tools library reduce the possibility of human error during decomposition and setup for the numerical solver by accounting for boundary conditions and connectivity. GUMBO is
Buscheck, T. A.; Bielicki, J. M.; Randolph, J.; Chen, M.; Hao, Y.; Sun, Y.
2013-12-01
Abstract We present an approach to use CO2 to (1) generate dispatchable renewable power that can quickly respond to grid fluctuations and be cost-competitive with natural gas, (2) stabilize the grid by efficiently storing large quantities of energy, (3) enable seasonal storage of solar thermal energy for grid integration, (4) produce brine for power-plant cooling, all which (5) increase CO2 value, rendering CO2 capture to be commerically viable, while (6) sequestering huge quantities of CO2. These attributes reduce carbon intensity of electric power, and enable cost-competitive, dispatchable power from major sources of renewable energy: wind, solar, and geothermal. Conventional geothermal power systems circulate brine as the working fluid to extract heat, but the parasitic power load for this circulation can consume a large portion of gross power output. Recently, CO2 has been considered as a working fluid because its advantageous properties reduce this parasitic loss. We expand on this idea by using multiple working fluids: brine, CO2, and N2. N2 can be separated from air at lower cost than captured CO2, it is not corrosive, and it will not react with the formation. N2 also can improve the economics of energy production and enable energy storage, while reducing operational risk. Extracting heat from geothermal reservoirs often requires submersible pumps to lift brine, but these pumps consume much of the generated electricity. In contrast, our approach drives fluid circulation by injecting supplemental, compressible fluids (CO2, and N2) with high coefficients of thermal expansion. These fluids augment reservoir pressure, produce artesian flow at the producers, and reduce the parasitic load. Pressure augmentation is improved by the thermosiphon effect that results from injecting cold/dense CO2 and N2. These fluids are heated to reservoir temperature, greatly expand, and increase the artesian flow of brine and supplemental fluid at the producers. Rather than using
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...
Robust Current Control of Doubly Fed Wind Turbine Generator under Unbalanced Grid Voltage Conditions
DEFF Research Database (Denmark)
Wang, Yun; Gong, Wenming; Wu, Qiuwei
2014-01-01
This paper presents the design of a H ∞ current controller for doubly fed induction generators (DFIGs) in order to maintain stable operation under unbalanced voltage conditions. The H ∞ current controller has a multi-input and multi-output (MIMO) structure and is designed using the loop shaping...... method. Case studies have been carried out in order to verify the efficacy of the proposed H ∞ current controller for DFIGs. The case study results show that the proposed H ∞ current controller can realize different control objectives, i.e. stable stator current, stable stator active power and stable...
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...
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...... references are calculated. In addition, the allocation principles for the PGSC’s current references are proposed by taking into account the PGSC's current rating limit. The impact of PGSC’s current limit on the proposed control strategies have been investigated in detail. Furthermore, a PI regulator...
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.
Angerman, HJ; ten Brinke, G
The subject of this paper is inspired by microphase-separated copolymer melts in which a small-scale structure is present inside one of the phases of a large-scale structure. Such a situation can arise in a diblock copolymer melt, if one of the blocks of the diblock is in itself a multiblock
Smirnova, YG; ten Brinke, G; Erukhimovich, IY; Smirnova, Yuliya G.; Erukhimovich, Igor Ya.
2006-01-01
The phase behavior of A(fmN)(B(N/2)A(N/2))B(1-f)mN multiblock copolymer melts is studied within the weak segregation theory. The interplay between ordering on different length scales is shown to cause dramatic changes both in the ordered phase symmetry and periodicity upon small variation of the arc
Angerman, HJ; ten Brinke, G
2003-01-01
The subject of this paper is inspired by microphase-separated copolymer melts in which a small-scale structure is present inside one of the phases of a large-scale structure. Such a situation can arise in a diblock copolymer melt, if one of the blocks of the diblock is in itself a multiblock copolym
Smirnova, YG; ten Brinke, G; Erukhimovich, IY; Smirnova, Yuliya G.; Erukhimovich, Igor Ya.
2006-01-01
The phase behavior of A(fmN)(B(N/2)A(N/2))B(1-f)mN multiblock copolymer melts is studied within the weak segregation theory. The interplay between ordering on different length scales is shown to cause dramatic changes both in the ordered phase symmetry and periodicity upon small variation of the arc
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.
Kato, Takeyoshi; Yamawaki, Hiroshi; Suzuoki, Yasuo
Power output fluctuation of photovoltaic power generation systems (PVSs) may cause negative impacts on the existing electric power system when the penetration of PVSs is quite large. A micro-grid consisting of clustered PVSs and a battery system would be one of the promising measures against negative impacts of clustered PVSs, while the capacity of battery system should be reduced as much as possible from the economic point of view. Because of the difference in output fluctuation among PVSs in the various locations, the total output fluctuations of PVSs would be relaxed due to the so-called “smoothing-effect”. By using data on solar irradiance simultaneously observed at five points, this study evaluates the total output fluctuation of several micro-grids and the required capacity of battery system, taking the smoothing effect into account. The main results are as follows. The balancing control is accomplished with the acceptable error by using the small capacity of battery system, while small output fluctuation still remains in each micro-grid. In such the situation, because the total fluctuation of five micro-grids is not so large, the acceptable error in balancing control can be increased by a few percentages, resulting in reduction in the required maximum power of battery system by a few ten percentages.
Directory of Open Access Journals (Sweden)
Benson, Etienne
2015-05-01
Full Text Available The fact that industrial infrastructures are embedded in complex environments animated by unexpected agencies is often invisible to their users — at least those who live in rich, industrialized societies with reliable systems for distributing water, power, and other goods and services. This article investigates how that invisibility is generated through a case study of electric power transmission in California in the early twentieth century. In the 1910s, the Pacific Light and Power Company constructed a 150,000-volt transmission line that delivered power from the Big Creek hydroelectric complex in the Sierra Nevada to customers in Los Angeles, more than 240 miles (386 kilometers away. When the Southern California Edison Company upgraded this line to 220,000 volts in the early 1920s, the rate of disruptive “flashovers” on the line jumped dramatically. After months of investigation, the cause was determined to be excrement from birds perching on the transmission towers. To render this and other sources of interruption invisible to users, two techniques were used: insulation and interconnection. These kinds of humble techniques of separation and resilience are ubiquitous in modern infrastructure. By creating and maintaining divisions, they make it possible for new kinds of agency to emerge. Infrastructures become animate: responsive to their environments in ways that allow them to persist in the face of continual change.
DEFF Research Database (Denmark)
Golestan, Saeed; Monfared, Mohammad; Guerrero, Josep M.
2013-01-01
design procedure based on the pole-zero cancellation, and the extended symmetrical optimum theory is proposed. During the design procedure, the effects of grid frequency variations and the presence of distortion in the grid voltage are taken into account. Finally, to confirm the effectiveness......The reference current generation (RCG) is a crucial part in the control of a shunt active power filter (APF). A variety of RCG techniques have been proposed in literature. Among these, the instantaneous reactive power theory, called pq theory, is probably the most widely used technique. The pq...
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’.
DEFF Research Database (Denmark)
Zhou, Dao; Blaabjerg, Frede; Franke, Toke
2015-01-01
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...
DEFF Research Database (Denmark)
Zhou, Dao; Blaabjerg, Frede; Franke, Toke
2014-01-01
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...
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.
Directory of Open Access Journals (Sweden)
Rongxiang Yuan
2016-04-01
Full Text Available In the traditional paradigm, large power plants provide active and reactive power required for the transmission system and the distribution network purchases grid power from it. However, with more and more distributed energy resources (DERs connected at distribution levels, it is necessary to schedule DERs to meet their demand and participate in the electricity markets at the distribution level in the near future. This paper proposes a comprehensive operational scheduling model to be used in the distribution management system (DMS. The model aims to determine optimal decisions on active elements of the network, distributed generations (DGs, and responsive loads (RLs, seeking to minimize the day-ahead composite economic cost of the distribution network. For more detailed simulation, the composite cost includes the aspects of the operation cost, emission cost, and transmission loss cost of the network. Additionally, the DMS effectively utilizes the reactive power support capabilities of wind and solar power integrated in the distribution, which is usually neglected in previous works. The optimization procedure is formulated as a nonlinear combinatorial problem and solved with a modified differential evolution algorithm. A modified 33-bus distribution network is employed to validate the satisfactory performance of the proposed methodology.
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.
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)
Ludois, D.; Venkataramanan, G. [Department of Electrical and Computer Engineering, University of Wisconsin-Madison 1415 Engineering Dr. Madison WI 53706 (United States)
2010-06-15
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 may be used by wind energy/bulk transmission developers for performing engineering trade-off studies. (author)
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.
Bezemer, J.M.; Radersma, R.; Grijpma, Dirk W.; Dijkstra, Pieter J.; van Blitterswijk, Clemens; Feijen, Jan
2000-01-01
The entrapment of lysozyme in amphiphilic multiblock copolymer microspheres by emulsification and subsequent solvent removal processes was studied. The copolymers are composed of hydrophilic poly(ethylene glycol) (PEG) blocks and hydrophobic poly(butylene terephthalate) (PBT) blocks. Direct solvent
Directory of Open Access Journals (Sweden)
E.Rajendran
2013-10-01
Full Text Available Wind energy is a leader area of application for variable-speed generators operating on the constant grid frequency. This paper depicts the power quality enhancement in wind power system using permanent magnet synchronous generator (PMSG and Quasi Z-source Inverter. The PMSG is connected to the power network by means of a quasi z-source inverter (qZSI. The PMSG are used by these technologies due to extraordinary characteristics such as a smaller amount weight and volume, superior performance, eradicate the gear box and no need of peripheral power in permanent magnet excitation. The PMSG overcome the induction generator and other generators, because of their splendid performances without take up the grid power. But Induction Generator always needs the grid connectionfor getting power to start. In this paper the quasi Z-source inverter is a present that is a novel topology conjugated from the traditional Z source Inverter. The qZSI inherits all the advantages of the ZSI, that is performs buck-boost, inversion and power control in wind energy conversion system (WECS Moreover, the proposed qZSI the matchless advantages of less component ratings and stable dc current from the source. All over boost control methods are built for the ZSI can be used by the qZSI .This Paper presents hysteresis current control technique for the quasi Z- source inverter.
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...... were made at a reduced scale ( 2.2 kW). The constant power test showed that both method have good results which can respect existing grid codes. The constant power test showed that both method have good results which can respect existing grid codes....
2016-03-24
tensor . The...release. Figure 2. Examples of previous anisotropic surfaces include the original holographic tensor impedance surface created by the author (left... tensor that can be extracted from the properties of each unit cell. This impedance tensor can be mapped back onto the surface, and simulations of
Arc Length Based Grid Distribution For Surface and Volume Grids
Mastin, C. Wayne
1996-01-01
Techniques are presented for distributing grid points on parametric surfaces and in volumes according to a specified distribution of arc length. Interpolation techniques are introduced which permit a given distribution of grid points on the edges of a three-dimensional grid block to be propagated through the surface and volume grids. Examples demonstrate how these methods can be used to improve the quality of grids generated by transfinite interpolation.
Arc length based grid distribution for surface and volume grids
Energy Technology Data Exchange (ETDEWEB)
Mastin, C.W. [NASA Langley Research Center, Hampton, VA (United States)
1996-12-31
Techniques are presented for distributing grid points on parametric surfaces and in volumes according to a specified distribution of arc length. Interpolation techniques are introduced which permit a given distribution of grid points on the edges of a three-dimensional grid block to be propagated through the surface and volume grids. Examples demonstrate how these methods can be used to improve the quality of grids generated by transfinite interpolation.
Directory of Open Access Journals (Sweden)
Shota Somekawa
2015-06-01
Full Text Available The ability to control the micelle size of poly(lactic acid and poly(ethylene glycol (PLA–PEG block copolymers is important for controlling their circulation in blood cell recognition, drug release and therapeutic effects. We successfully controlled the micelle size by changing the block number of copolymers (multiblock index. PLA–PEG multiblock copolymers with multiblock indexes ranging from 1.35 to 2.78 were synthesized by direct polycondensation with tin chloride/p-toluenesulfonic acid binary catalysts, using PEG with a molecular weight (Mw of 3200 Da. The Mw of PLA–PEG copolymers increased with an increase in the multiblock index, while micelle size, measured by dynamic light scattering, decreased greatly from 349 to 28 nm. In addition, the X-ray diffraction peak of the PLA crystal disappeared when the multiblock index was increased. These results indicate that a multiblock structure is useful for controlling micelle size without changing the PLA/PEG composition or PEG molecular weight, which strongly influences other micelle features.
Energy Technology Data Exchange (ETDEWEB)
Mahmoud, Marwan M.; Ibrik, Imad H. [Energy Research Centre, An-Najah National University, Nablus, P.O. Box 721, West Bank (Palestine)
2006-04-01
As a contribution to the development program of rural areas in Palestine, this paper presents three energy supply alternatives for a remote village represented in PV system, diesel generator and electric grid. Design of these systems and the associated costs of their utilization are illustrated. A computer-aided dynamic economic evaluation method with five indicators is used to compare the economic-effectiveness of these energy systems. The results show that, utilizing of PV systems for rural electrification in Palestine is economically more feasible than using diesel generators or extension of the high voltage electric grid. The obtained results represents also a helpful reference for energy planers in Palestine and justify the consideration of PV systems more seriously. (author)
Energy Technology Data Exchange (ETDEWEB)
Ibrik, Imad [An-Najah National Univ., Nablus (PS). Energy Research Centre; Lecumberri, Marta
2010-07-01
The energy situation in Palestine is somewhat unique when compared to other countries in the Middle East. There are virtually no available natural resources, and due to the ongoing political situation, the Palestinians rely (or have to rely) almost totally on Israel for their energy needs. This paper presents three energy supply alternatives for a remote village represented in PV system, diesel generator and electric grid. Design of these systems and the associated costs of their utilization are illustrated. Economic evaluation methods are used to compare the economic-effectiveness of these energy systems. The results show that, utilizing of PV systems for rural electrification in Palestine is economically more useful than using diesel generators or extension of the high voltage electric grid. The obtained results represents also a helpful reference for energy planers in Palestine and justify the consideration of PV systems more seriously. (orig.)
Quintana Barcia, Pablo José
2016-01-01
This PhD Thesis, entitled “Power Electronic Supplies For Public Lighting Systems With Distributed Generation Capability: Solution Proposals For Power And Control Stages, Characterization And Minimization Of The Impact In Grid Quality”, has been developed as one of the core research activities of the Efficient Energy Conversion, Industrial Electronics and Lighting Engineering group (CE3I2), from the Electrical Engineering Department (DIEECS) of the University of Oviedo. This work targets th...
Energy Technology Data Exchange (ETDEWEB)
Zhou, Fang; Qin, Xiaoshuai; Li, Yancai; Ren, Lixia; Zhao, Yunhui, E-mail: zhaoyunhui@tju.edu.cn; Yuan, Xiaoyan
2015-08-30
Highlights: • QAS-containing fluorosilicone multi-block copolymers were synthesized. • The block length of PHFBMA in the copolymers was tailored via RAFT polymerization. • Surface roughness of the copolymers decreased with the increased PHFBMA content. • A certain length of PHFBMA block enhanced C−N{sup +} percentage on the surface. - Abstract: Symmetrically structured fluorosilicone multi-block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(hexafluorobutyl methacrylate) (PHFBMA) were sequentially synthesized via reversible addition–fragmentation chain transfer polymerization, using a polydimethylsiloxane (PDMS) chain transfer agent with dithiocarbonate groups at both ends. Then, the CBABC-type block copolymers were quaternized with n-octyliodide to tether quaternary ammonium salt (QAS) groups in the PDMAEMA blocks for the antimicrobial use. The obtained fluorosilicone copolymers showed clear variations in the C-N{sup +} composition and surface morphology on their films depending on the content of the PHFBMA blocks, which were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The results indicated that the symmetrical CBABC structure favored PDMS and QAS tethered blocks migrating to the film surface. With the mass percentage of the PHFBMA increased from 0 to 32.5%, the surface roughness of the copolymer film decreased gradually with a tendency to form a smooth surface. Owing to the surface properties, fluorosilicone multi-block copolymers containing a certain amount of PHFBMA with higher C-N{sup +} content and relatively smooth morphology demonstrated obvious antimicrobial activity against Gram-positive bacteria, Bacillus subtilis and Gram-negative bacteria, Escherichia coli. The functionalized multi-block copolymers based on fluorosilicone and QAS groups would have potential applications in antimicrobial coatings.
Collapse transitions in thermosensitive multi-block copolymers: A Monte Carlo study
Energy Technology Data Exchange (ETDEWEB)
Rissanou, Anastassia N., E-mail: rissanou@tem.uoc.gr [Department of Mathematics and Applied Mathematics, University of Crete, GR-71003 Heraklion Crete, Greece and Archimedes Center for Analysis, Modeling and Computation, University of Crete, P.O. Box 2208, GR-71003 Heraklion Crete (Greece); Tzeli, Despoina S. [Department of Materials Science and Technology, University of Crete, GR-71003 Heraklion Crete (Greece); Anastasiadis, Spiros H. [Department of Chemistry, University of Crete, P.O. Box 2208, 710 03 Heraklion Crete (Greece); Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, GR-71110 Heraklion Crete (Greece); Bitsanis, Ioannis A. [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, GR-71110 Heraklion Crete (Greece)
2014-05-28
Monte Carlo simulations are performed on a simple cubic lattice to investigate the behavior of a single linear multiblock copolymer chain of various lengths N. The chain of type (A{sub n}B{sub n}){sub m} consists of alternating A and B blocks, where A are solvophilic and B are solvophobic and N = 2nm. The conformations are classified in five cases of globule formation by the solvophobic blocks of the chain. The dependence of globule characteristics on the molecular weight and on the number of blocks, which participate in their formation, is examined. The focus is on relative high molecular weight blocks (i.e., N in the range of 500–5000 units) and very differing energetic conditions for the two blocks (very good—almost athermal solvent for A and bad solvent for B). A rich phase behavior is observed as a result of the alternating architecture of the multiblock copolymer chain. We trust that thermodynamic equilibrium has been reached for chains of N up to 2000 units; however, for longer chains kinetic entrapments are observed. The comparison among equivalent globules consisting of different number of B-blocks shows that the more the solvophobic blocks constituting the globule the bigger its radius of gyration and the looser its structure. Comparisons between globules formed by the solvophobic blocks of the multiblock copolymer chain and their homopolymer analogs highlight the important role of the solvophilic A-blocks.
The generation of straight lines algorithms on hexagonal grid%六角网格上的直线生成算法
Institute of Scientific and Technical Information of China (English)
刘勇奎; 沈红; 周晓敏
2001-01-01
经研究表明，屏幕上的点最佳分布是按六角网格形式分布的。文中首先讨论了六角网格的特点，并从图形图象处理的角度分析了它的优点，然后提出了在六角网格上的直线生成算法，此算法仅用了整数运算。%Many studies have shown that the best disposition of a discrete set of points on the plane can be reached if the points are on a hexagonal grid. This paper first discusses character of the hexagonal grid and gives its advantages over the square grid in view of displaying graphics and images. Then it describes an algorithm for the generation of straight lines on hexagonal grid. It uses only integer arithmetic.
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)
Premnath, Kannan N [Department of Mechanical Engineering, University of Colorado Denver, 1200 Larimer Street, Denver, CO 80217 (United States); Pattison, Martin J [HyPerComp Inc., 2629 Townsgate Road, Suite 105, Westlake Village, CA 91361 (United States); Banerjee, Sanjoy, E-mail: kannan.premnath@ucdenver.edu, E-mail: kannan.np@gmail.com [Department of Chemical Engineering, City College of New York, City University of New York, New York, NY 10031 (United States)
2013-10-15
Lattice Boltzmann method (LBM) is a kinetic based numerical scheme for the simulation of fluid flow. While the approach has attracted considerable attention during the last two decades, there is a need for systematic investigation of its applicability for complex canonical turbulent flow problems of engineering interest, where the nature of the numerical properties of the underlying scheme plays an important role for their accurate solution. In this paper, we discuss and evaluate a LBM based on a multiblock approach for efficient large eddy simulation of three-dimensional external flow past a circular cylinder in the transitional regime characterized by the presence of multiple scales. For enhanced numerical stability at higher Reynolds numbers, a multiple relaxation time formulation is considered. The effect of subgrid scales is represented by means of a Smagorinsky eddy-viscosity model, where the model coefficient is computed locally by means of a dynamic procedure, providing better representation of flow physics with reduced empiricism. Simulations are performed for a Reynolds number of 3900 based on the free stream velocity and cylinder diameter for which prior data is available for comparison. The presence of laminar boundary layer which separates into a pair of shear layers that evolve into turbulent wakes impose particular challenge for numerical methods for this condition. The relatively low numerical dissipation introduced by the inherently parallel and second-order accurate LBM is an important computational asset in this regard. Computations using five different grid levels, where the various blocks are suitably aligned to resolve multiscale flow features show that the structure of the recirculation region is well reproduced and the statistics of the mean flow and turbulent fluctuations are in satisfactory agreement with prior data. (paper)
并网光伏电站置信容量评估%Capacity Credit Evaluation of Grid-Connected Photovoltaie Generation
Institute of Scientific and Technical Information of China (English)
方鑫; 郭强; 张东霞; 梁双
2012-01-01
To evaluate the capacity credit of photovoltaic (PV) generation is one of urgent problems to be considered when large-scale PV station is connected to traditional power grid. The capacity credit of PV generation is evaluated by the generation capacity that could be reduced in traditional power grid after the grid-connection of PV station. For this purpose, a new method for evaluating the capacity credit of PV generation is proposed. Firstly, an annual output fluctuating model of PV generation, in which the occurrence probabilities of different weather types, the maximum proportions of solar radiation under various whether conditions, the fluctuation radiation range due to clouds mask and the temperature coefficient random variation range are taken into account, is built; secondly, based on sequential Monte-Carlo simulation, a method to calculate generation reliability of power grid is put forward and its objective function is established based on the loss of load expectation (LOLE) before and after the grid-connection of PV station, and then the particle swarm optimization is utilized to search optimal combination of traditional generation sets to make the generation reliability level of power grid conforming with that before the grid-connection of PV station. Both correctness and effectiveness of the proposed model and algorithm are verified by simulation results of IEEE-RTS79 system..%衡量光伏发电的置信容量是大规模光伏电站接入电网时需要考虑的问题之一.以光伏发电接入后系统可以减少的发电容量来评估光伏发电的置信容量,建立了考虑不同天气类型概率、最大辐射强度、云遮波动以及温度系数波动的年光伏出力波动模型.提出了基于序贯蒙特卡罗仿真的电力系统发电可靠性的计算方法,并以光伏发电接入前后的系统电力不足期望(loss of load expectation,LOLE)为基础,建立了目标函数,并用粒子群优化算法搜索光伏发电接入后系
Laizet, S; Vassilicos, J C
2014-01-01
We focus in this paper on the effect of the resolution of Direct Numerical Simulations (DNS) on the spatio-temporal development of the turbulence downstream of a single square grid. The aims of this study are to validate our numerical approach by comparing experimental and numerical one-point statistics downstream of a single square grid and then investigate how the resolution is impacting the dynamics of the flow. In particular, using the Q-R diagram, we focus on the interaction between the strain-rate and rotation tensors, the symmetric and skew-symmetric parts of the velocity gradient tensor respectively. We first show good agreement between our simulations and hot-wire experiment for one-point statistics on the centreline of the single square grid. Then, by analysing the shape of the Q-R diagram for various streamwise locations, we evaluate the ability of under-resolved DNS to capture the main features of the turbulence downstream of the single square grid.
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 w...
Energy Technology Data Exchange (ETDEWEB)
Reno, Matthew J.; Riehm, Andrew Charles; Hoekstra, Robert John; Munoz-Ramirez, Karina; Stamp, Jason Edwin; Phillips, Laurence R.; Adams, Brian M.; Russo, Thomas V.; Oldfield, Ron A.; McLendon, William Clarence, III; Nelson, Jeffrey Scott; Hansen, Clifford W.; Richardson, Bryan T.; Stein, Joshua S.; Schoenwald, David Alan; Wolfenbarger, Paul R.
2011-02-01
Design and operation of the electric power grid (EPG) relies heavily on computational models. High-fidelity, full-order models are used to study transient phenomena on only a small part of the network. Reduced-order dynamic and power flow models are used when analysis involving thousands of nodes are required due to the computational demands when simulating large numbers of nodes. The level of complexity of the future EPG will dramatically increase due to large-scale deployment of variable renewable generation, active load and distributed generation resources, adaptive protection and control systems, and price-responsive demand. High-fidelity modeling of this future grid will require significant advances in coupled, multi-scale tools and their use on high performance computing (HPC) platforms. This LDRD report demonstrates SNL's capability to apply HPC resources to these 3 tasks: (1) High-fidelity, large-scale modeling of power system dynamics; (2) Statistical assessment of grid security via Monte-Carlo simulations of cyber attacks; and (3) Development of models to predict variability of solar resources at locations where little or no ground-based measurements are available.
Application of Generators Unplanned Outage Monitoring of Shanxi Power Grid%山西电网机组非计划停运监测应用研究
Institute of Scientific and Technical Information of China (English)
徐宏锐
2015-01-01
To solve the problem of generators unplanned outage in Shanxi power grid, we developed the monitoring module of harmonious dispatch supporting system by using its on-line monitoring function. By analyzing, we can predict in advance the potential risks and the cause of generators unplanned outage. The application effectively filled the blank of the impact on the security and stability of Shanxi Power Grid, which not only prepared for the power balance in days or a few days ago, but also made a strong technical support for the safe and stable operation of the power grid.%针对山西电网发电机组非停事件,利用和谐调度系统在线监测功能,开发了和谐系统机组非停监测模块,并将其应用到了非停原因分析中.通过分析,可以提前判断机组非停的潜在风险及故障原因.有效填补了机组非停影响电网安全稳定的空白,为日内或日前电网平衡做好充分准备,且为电网安全稳定运行提供有力的技术保障.
Directory of Open Access Journals (Sweden)
Ahmad Bashar Ataji
2016-03-01
Full Text Available This paper addresses the grid-connected variable speed doubly-fed induction generator, and proposes a new decoupled control to replace the conventional decoupled active and reactive powers (P-Q control. The proposed decoupled control is based on decoupling the stator active and reactive currents, in contrast with the conventional decoupled P-Q control, which is based on decoupling the stator active and reactive powers by forcing the stator d- or q-voltage to zero. The proposed decoupled control has all the advantages of the conventional decoupled P-Q control such as constant switching frequency and robustness against slip angle inaccuracy, and it has some additional advantages: The proposed control requires less machine parameters; for the controller design, it requires the stator-to-rotor turns ratio only; for the online calculation, it does not requires any machine parameter. The proposed decoupled control is more flexible and robust since the control is independent of the grid voltage orientation. It is robust against variation in the grid voltage amplitude. Several experiments are carried out using a 1.1 kW doubly-fed induction generator (DFIG, and the results support the proposed decoupled control and demonstrate some of its advantages.
Directory of Open Access Journals (Sweden)
W. Yan
2015-07-01
Full Text Available A multiblock copolymer termed as PCL-PIBMD, consisting of crystallizable poly(ε-caprolactone (PCL segments and crystallizable poly(3S-isobutyl-morpholine-2,5-dione (PIBMD segments, has been reported as a material showing a thermally-induced shape-memory effect. While PIBMD crystalline domains act as netpoints to determine the permanent shape, both PCL crystalline domains and PIBMD amorphous domains, which have similar transition temperatures (Ttrans can act as switching domains. In this work, the influence of the deformation temperature (Tdeform = 50 or 20°C, which was above or below Ttrans, on the structural changes of PCL-PIBMD during uniaxial deformation and the shapememory properties were investigated. Furthermore, the relative contribution of crystalline PCL and PIBMD amorphous phases to the fixation of the temporary shape were distinguished by a toluene vapor treatment approach. The results indicated that at 50°C, both PCL and PIBMD amorphous phases can be orientated during deformation, resulting in thermallyinduced crystals of PCL domains and joint contribution to the switching domains. In contrast at 20°C, the temporary shape was mainly fixed by PCL crystals generated via strain-induced crystallization.
Bewley, Thomas; Cessna, Joseph; Belitz, Paul
2008-11-01
The abstract field of n-dimensional sphere packing theory is well developed (for a comprehensive review, see Sphere Packings, Lattices and Groups by Conway and Sloane). This theory forms the theoretical underpinning of the error-correcting codes used in both deep space communications and in computer memory. The present work extends this elegant theory to two important and immensely practical problems in computational fluid dynamics: (a) the generation of efficient grids for the coordination of grid-based derivative-free optimization algorithms in n dimensions, and (b) the effective n-dimensional interconnection of massively-parallel clusters of computational nodes. As we will illustrate and quantify, the first problem benefits tremendously from dense sphere packings with large kissing numbers >> 2n, whereas the latter problem benefits tremendously from rare sphere packings with kissing number = n+1.
Directory of Open Access Journals (Sweden)
Badrinarayan Bansilal Pimple
2015-02-01
Full Text Available This study proposes a polar voltage control-based direct torque control method to reduce the effects of unbalanced grid voltage on doubly-fed induction generator (DFIG-based wind turbine system. Under unbalanced grid voltage, the stator flux has a negative sequence component which leads to second harmonic pulsation in torque, stator active power, stator reactive power, stator current and rotor current. In the control scheme, the negative sequence rotor voltage vector is controlled to compensate the negative sequence stator flux by negative sequence rotor flux. Simulation study is carried out on a 2 MW DFIG system using MATLAB/SIMULINK. Feasibility of the proposed control strategy is experimentally verified on a 1.5 kW DFIG system.
Gajendiran, Mani; Balashanmugam, Pannerselvam; Kalaichelvan, P. T.; Balasubramanian, Sengottuvelan
2016-06-01
The effect of π-back-bonding between AuNPs and the carbonyl group of multiblock copolyester on tuberculosis multi-drug delivery has been investigated. The carbonyl group of copolyester has vacant p orbitals and these vacant orbitals accept electron clouds from the filled d orbitals of Au0 to form π-back-bonding, which enhances the electron density for the carbonyl oxygen. This high electron density results in the strong binding of drug molecules with multiblock copolyesters and hence sustained drug release is achieved for a longer duration when compared to polymer systems without AuNPs. A new series of tartarate-linked poly(lactic-co-glycolic acid) (PLGA)—polyethylene glycol (PEG)-based multiblock copolymers has been synthesized using a solvent-free melt reaction. The biocompatibility of multiblock copolyesters and AuNP nanoconjugates was investigated with an in vitro cytotoxicity study on the Vero cell line. Three major tuberculosis drugs, namely, rifampicin-, isoniazid- and pyrazinamide-loaded AuNP multiblock copolymer NPs were prepared by probe sonication followed by the self-assembly method. An in vitro drug release experiment was carried out and the amount of the three drugs released at various time intervals was determined simultaneously by the HPLC technique. The nanoconjugates exhibit 33%-40% RIF, 71%-95% INH, 77%-99% PYZ loading efficiencies, while the polymer NPs exhibit relatively lesser values. The nanoconjugates show sustained drug release for up to 264 h.
National Aeronautics and Space Administration — New cell centered grids are generated to complement the node-centered ones uploaded. Six tarballs containing the coarse, medium, and fine mixed-element and pure tet....
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
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.
Directory of Open Access Journals (Sweden)
Hossein Shahinzadeh
2015-03-01
Full Text Available In recent years, several factors such as environmental pollution which is caused by fossil fuels and various diseases caused by them from one hand and concerns about the dwindling fossil fuels and price fluctuation of the products and resulting effects of these fluctuations in the economy from other hand has led most countries to seek alternative energy sources for fossil fuel supplies. Such a way that in 2006, about 18% of the consumed energy of the world is obtained through renewable energies. Iran is among the countries that are geographically located in hot and dry areas and has the most sun exposure in different months of the year. Except in the coasts of Caspian Sea, the percentage of sunny days throughout the year is between 63 to 98 percent in Iran. On the other hand, there are dispersed and remote areas and loads far from national grid which is impossible to provide electrical energy for them through transmission from national grid, therefore, for such cases the renewable energy technologies could be used to solve the problem and provide the energy. In this paper, technical and economic feasibility for the use of renewable energies for independent systems of the grid for a dispersed load in the area on the outskirts of Isfahan (Sepahan with the maximum energy consumption of 3Kwh in a day is studied and presented. In addition, the HOMER simulation software is used as the optimization tool.
Ackermann, Doreen; Wang, Weiqun; Streipert, Benjamin; Geib, Birgit; Grün, Lothar; König, Simone
2012-05-01
The comparison of proteins separated on 2DE is difficult due to gel-to-gel variability. Here, a method named comparative fluorescence gel electrophoresis (CoFGE) is presented, which allows the generation of an artificial protein grid in parallel to the separation of an analytical sample on the same gel. Different fluorescent stains are used to distinguish sample and marker on the gel. The technology combines elements of 1DE and 2DE. Special gel combs with V-shaped wells are placed in a stacking gel above the pI strip. Proteins separated on the pI strip are electrophoresed at the same time as marker proteins (commercially available purified protein of different molecular weight) placed in V-wells. In that way, grids providing approximately 100 nodes as landmarks for the determination of protein spot coordinates are generated. Data analysis is possible with commercial 2DE software capable of warping. The method improves comparability of 2DE protein gels, because they are generated in combination with regular in-gel anchor points formed by protein standards. This was shown here for two comparative experiments with three gels each using Escherichia coli lysate. For a set of 47 well-defined samples spots, the deviation of the coordinates was improved from 7% to less than 1% applying warping using the marker grid. Conclusively, as long as the same protein markers, the same size of pI-strips and the same technology are used, gel matching is reproducibly possible. This is an important advancement for projects involving comparison of 2DE-gels produced over several years and in different laboratories. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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-HVDC...
Indian Academy of Sciences (India)
2016-05-01
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 on demand. In this article,we describe the grid computing model and enumerate themajor differences between grid and cloud computing.
Energy Technology Data Exchange (ETDEWEB)
Rauthe, Monika; Steiner, Heiko; Riediger, Ulf; Mazurkiewicz, Alex; Gratzki, Annegret [Deutscher Wetterdienst, Offenbach am Main (Germany)
2013-10-15
A new precipitation climatology (DWD/BfG-HYRAS-PRE) is presented which covers the river basins in Germany and neighbouring countries. In order to satisfy hydrological requirements, the gridded dataset has a high spatial resolution of 1 km{sup 2} and a daily temporal resolution that is based on up to 6200 precipitation stations within the spatial domain. The period of coverage extends from 1951 to 2006 for which gridded, daily precipitation fields were calculated from the station data using the REGNIE method. This is a combination between multiple linear regression considering orographical conditions and inverse distance weighting. One of the main attributes of the REGNIE method is the preservation of the station values for their respective grid cells. A detailed validation of the data set using cross-validation and Jackknifing showed both seasonally- and spatially-dependent interpolation errors. These errors, through further applications of the HYRAS data set within the KLIWAS project and other studies, provide an estimate of its certainty and quality. The mean absolute error was found to be less than 2 mm/day, but with both spatial and temporal variability. Additionally, the need for a high station network density was shown. Comparisons with other existing data sets show good agreement, with areas of orographical complexity displaying the largest differences within the domain. These errors are largely due to uncertainties caused by differences in the interpolation method, the station network density available, and the topographical information used. First climatological applications are presented and show the high potential of this new, high-resolution data set. Generally significant increases of up to 40% in winter precipitation and light decreases in summer are shown, whereby the spatial variability of the strength and significance of the trends is clearly illustrated. (orig.)
STUDY ON THE SYNTHESIS AND PROPERTIES OF POLY(ESTER-IMIDE-ETHER) MULTIBLOCK COPOLYMERS
Institute of Scientific and Technical Information of China (English)
Zu-yao Shan; Zhen-yi Li
2000-01-01
A new class of poly(ester-imide-ether) multiblock copolymers was synthesized by transes-terification and melt copolymerization of dimethyl terephthalate (DMT) and N-(4-carbomethoxyphenyl)-4-(carbomethoxy)-phthalimide with ethylene glycol (EG) and polytetramethylene glycol (PTMG). The structure of the above copolymers was characterized by 1H-NMR and IR spectroscopy. Some properties of the coplymers were also examined. It was found that their mechanical properties and heat stability, compared with poly(ether-ester) copolymers, were obviously improved.
SYNTHESIS AND CHARACTERIZATION OF Si-CONTAINING POLYESTER-POLYETHER MULTIBLOCK COPOLYMERS
Institute of Scientific and Technical Information of China (English)
LI Zhenyi; ZHU Jin
1996-01-01
A series of Si-containing polyester-polyether multiblock copolymers were synthesized by transesterification and melt copolycondensation of organosilicon monomers [1, 1, 3, 3-tetramethyl-1, 3-bis (p-carbomethoxyphenyl) disiloxane] (I) or dimethyl bis (p-carbomethoxyphenyl) silane] (II) and dimethyl terephthalate (DMT), with 1, 4-butanediol, polytetramethylene glycol (PTMG) respectively. The organosilicon monomers were prepared by Grinard reaction, oxidation and esterification. The structures of the above monomers (Ⅰ), (Ⅱ) and the copolymers were characterized by MS anal. and 1H-NMR.
STUDY ON SOME PROPERTIES OF Si-CONTAINING POLYESTER-POLYETHER MULTIBLOCK COPOLYMERS
Institute of Scientific and Technical Information of China (English)
LI Zhenyi; ZHU Jin
1997-01-01
Some physical properties of the polyester-polyether multiblock copolymers with Si-containing hard segment were further examined by a series of physical methods. The hydrophobicity of the copolymers was improved with the incorporation of increasing amount of orgauosilicone, XPS test proved that silicon element was enriched at the surface of the Si-containing polyester-polyether copolymers. It was also found that their heat resistance and gas permeability for O2 and N2 were greatly improved. The study on semipermeability of films made of the Si-containing copolymers was also followed with interest.
2010-01-01
The technique to derive a dc-ac full bridge switching converter for a PV grid-connected system are proposed in this paper. An analysis of islanding phenomena due to load variations of R and RLC connections can be easily derived by using the state-space averaging technique and the piecewise technique with feedback current control by setting up the duty cycle with sinusoidal terms around constant value of 0.5. The solution of the two proposed models can be handled via MATLAB/SIMULINK in fast sp...
Visualization of big SPH simulations via compressed octree grids
Reichl, Florian
2013-10-01
Interactive and high-quality visualization of spatially continuous 3D fields represented by scattered distributions of billions of particles is challenging. One common approach is to resample the quantities carried by the particles to a regular grid and to render the grid via volume ray-casting. In large-scale applications such as astrophysics, however, the required grid resolution can easily exceed 10K samples per spatial dimension, letting resampling approaches appear unfeasible. In this paper we demonstrate that even in these extreme cases such approaches perform surprisingly well, both in terms of memory requirement and rendering performance. We resample the particle data to a multiresolution multiblock grid, where the resolution of the blocks is dictated by the particle distribution. From this structure we build an octree grid, and we then compress each block in the hierarchy at no visual loss using wavelet-based compression. Since decompression can be performed on the GPU, it can be integrated effectively into GPU-based out-of-core volume ray-casting. We compare our approach to the perspective grid approach which resamples at run-time into a view-aligned grid. We demonstrate considerably faster rendering times at high quality, at only a moderate memory increase compared to the raw particle set. © 2013 IEEE.
太阳能光伏发电并网模拟装置的研究%Research on simulated devices for photovoltaic grid-connected generation system
Institute of Scientific and Technical Information of China (English)
彭其泽; 张全柱
2012-01-01
On the standpoint of energy conservation and emission reduction, one device simulating the 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.%从节能减排的角度出发,设计了一种基于SPWM技术的光伏并网发电模拟装置,DC/AC逆变可以有效地进行直流至交流的转换.系统通过单片机编程的方式实现了最大功率点控制、频率和相位的跟踪.同时单片机还能通过编程方式实现PWM脉冲宽度调制.本系统最大的特点是用模拟的方式简明地介绍了整个光伏并网发电系统.
DEFF Research Database (Denmark)
Diaz de Cerio Mendaza, Iker; Pigazo, Alberto; Bak-Jensen, Birgitte
2013-01-01
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......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...... 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...
Saiyad Tausif Ali *; Gaurav Pawar; Pragati Rathi; Mandar Pathak
2016-01-01
3G Power grid system is dual side stream of electricity and automated construct information and distributed advanced energy delivery network. In this 3G Power grid system avoided the thermal and hydro sources of energy. By using the solar power and wind power energy will generate electricity according with the condition of nature. 3G Power grid system provides the facility of generating as well as marketing of electricity not only for the producers but also for consumers. By using megabytes o...
Analysis of the static properties of cluster formations in symmetric linear multiblock copolymers.
Fytas, N G; Theodorakis, P E
2011-06-15
We use molecular dynamics simulations to study the static properties of a single linear multiblock copolymer chain under poor solvent conditions varying the block length N, the number of blocks n, and the solvent quality by variation of the temperature T. We study the most symmetrical case, where the number of blocks of monomers of type A, n(A), equals that of monomers B, n(B) (n(A) = n(B) = n/2), the length of all blocks is the same irrespective of their type, and the potential parameters are also chosen symmetrically, as for a standard Lennard-Jones fluid. Under poor solvent conditions the chains collapse and blocks with monomers of the same type form clusters, which are phase separated from the clusters with monomers of the other type. We study the dependence of the size of the clusters formed on n, N and T. Furthermore, we discuss our results with respect to recent simulation data on the phase behaviour of such macromolecules, providing a complete picture for the cluster formations in single multiblock copolymer chains under poor solvent conditions.
光伏发电并网系统相量模型建模研究%Research on Phasor Model of Grid Connection PV Generation System
Institute of Scientific and Technical Information of China (English)
邱革非; 张春刚; 仲泽坤; 字杨
2015-01-01
A grid connection photovoltaic power generation system model is built in this paper.By this model, power characters of power grid which is connected with PV generation systems can be researched without igno-rance of the characters of PV generation system.Based on phasor analyzing method,PV generation system with power output controlling unit is built in detail,so that it can reflect actual controlling characteristics of PV system truthfully.Compared with existing grid connection PV models,it has the advantage of faster simulation,which can be applied to power system researches on power transferring and controlling characteristics of power system based on phasor analysis.%建立了一个既适用于电力系统网络功率分析，同时也能够在仿真过程中较为细致地反映光伏发电系统实际并网运行特性的并网光伏发电系统模型。文中以相量分析为基础对包含功率控制单元在内的发电系统进行了较为详细的相量建模，使得所建立的发电系统模型能够更为真实地体现光伏发电系统功率输出及控制特性，且由于模型系针对电力系统能量关系的分析研究而建，相较于现有光伏发电并网模型具备仿真速度快的优势，弥补了现存模型存在的缺点，可以方便地融合到以相量分析方法为基础的电力系统运行及控制特性相关研究中。
Stankovic, Milica; Tomar, Jasmine; Hiemstra, Christine; Steendam, Rob; Frijlink, Henderik W.; Hinrichs, Wouter L. J.
2014-01-01
In this study, the in vitro release of proteins from novel, biodegradable phase-separated poly(ε-caprolactone-PEG)-block-poly(ε-caprolactone), [PCL-PEG]-b-[PCL]) multiblock copolymers with different block ratios and with a low melting temperature (49-55 °C) was studied. The effect of block ratio and
Institute of Scientific and Technical Information of China (English)
邓秋玲; 彭晓; 张桂湘
2012-01-01
为了能够在电网故障下对直驱风电系统传递给电网的功率进行持续控制,避免变流器保护跌落和提高瞬态故障穿越能力,对故障电压基波正负序分量进行快速而准确的检测是必要的。提出了一种不平衡和畸变电压运行条件下风电系统网侧变流器的新型电网同步化技术,即双二阶通用积分器-锁频环（DSOGI-FLL）。这个新的检测器包括正交信号发生器、正负序分量计算器和锁频环3个基本函数模块。对DSOGI-FLL进行的仿真和试验结果表明这种新型软件锁相环便于数字实现,能对不对称和畸变电网电压进行快速、准确检测和稳定跟踪;DSOGI-FLL是直驱风电系统网侧变流器在电网电压不平衡和畸变条件下的一个合适的电网同步化方法。%It is essential for accurate and fast detection of fundamental frequency positive- and negative-sequence component of the utility voltage under grid fault to keep the control over the power exchange with the grid to avoid trip of the converter protections and to allow the ride-through of the transient fault. We proposed a new technique for grid synchronization of grid-side converter in direct drive wind power generation system under unbalanced and distorted conditions, i. e. , the dual second order generalized integrator frequency-locked loop（DSOGI-FLL）. The proposed detector includes three fundamental function blocks, namely, the quadrature-signals generator （QSG）, positive- and negative- sequence calculator （PNSC） and frequency-locked loop （FLL）. Moreover, the DSOGI-FLL was studied by simulation and experiment. The obtained simulation and experiment results demonstrate that this new software phase-locked loop is easy to implement by digital and can detect and track asymmetrical and distorted grid voltage rapidly and accurately, and the results indicate that the DSOGI-FLL is a very suitable solution for grid synchronization of grid-side converter
Fan, Wei; Shi, Wen; Zhang, Wenting; Jia, Yinnong; Zhou, Zhengyuan; Brusnahan, Susan K; Garrison, Jered C
2016-10-01
This work continues our efforts to improve the diagnostic and radiotherapeutic effectiveness of nanomedicine platforms by developing approaches to reduce the non-target accumulation of these agents. Herein, we developed multi-block HPMA copolymers with backbones that are susceptible to cleavage by cathepsin S, a protease that is abundantly expressed in tissues of the mononuclear phagocyte system (MPS). Specifically, a bis-thiol terminated HPMA telechelic copolymer containing 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Three maleimide modified linkers with different sequences, including cathepsin S degradable oligopeptide, scramble oligopeptide and oligo ethylene glycol, were subsequently synthesized and used for the extension of the HPMA copolymers by thiol-maleimide click chemistry. All multi-block HPMA copolymers could be labeled by (177)Lu with high labeling efficiency and exhibited high serum stability. In vitro cleavage studies demonstrated highly selective and efficient cathepsin S mediated cleavage of the cathepsin S-susceptible multi-block HPMA copolymer. A modified multi-block HPMA copolymer series capable of Förster Resonance Energy Transfer (FRET) was utilized to investigate the rate of cleavage of the multi-block HPMA copolymers in monocyte-derived macrophages. Confocal imaging and flow cytometry studies revealed substantially higher rates of cleavage for the multi-block HPMA copolymers containing the cathepsin S-susceptible linker. The efficacy of the cathepsin S-cleavable multi-block HPMA copolymer was further examined using an in vivo model of pancreatic ductal adenocarcinoma. Based on the biodistribution and SPECT/CT studies, the copolymer extended with the cathepsin S susceptible linker exhibited significantly faster clearance and lower non-target retention without compromising tumor targeting. Overall, these results indicate that
Directory of Open Access Journals (Sweden)
Mohammed Al-Smairan
2012-01-01
Full Text Available In the development of energy sources in remote regions in Jordan at the brink of the 21st century, it is necessary to view the use of solar energy in all applications as one of the most promising new and renewable energy sources. As a contribution to the development program of remote areas in Jordan Badia, this paper presents three energy supply alternatives (photovoltaic system, diesel generator and electric grid for a dump site for providing the electrical loads to the dump site according to their energy requirements. The result of this study shows that remote dump site in Jordan Badia will require about 5.32 kWh/day or 1940 kWh/yr to meet their basic power requirements for such loads as lighting and electronic appliances-radios and fans. Four dynamic indicators were used to compare the economic-effectiveness of these energy systems. It is found that providing electricity to a dump site in a remote zone using photovoltaic systems is very beneficial and competitive with the other types of conventional energy sources, especially considering the decreasing prices of these systems and their increasing efficiencies and reliability. They have also the advantage of maintaining a clean environment. It is recommended that solar photovoltaic-based dump site electrification application should be encouraged by the government, especially for those rural sites without access to a grid supply.
Swinbank, Richard; Purser, James
2006-01-01
Recent years have seen a resurgence of interest in a variety of non-standard computational grids for global numerical prediction. The motivation has been to reduce problems associated with the converging meridians and the polar singularities of conventional regular latitude-longitude grids. A further impetus has come from the adoption of massively parallel computers, for which it is necessary to distribute work equitably across the processors; this is more practicable for some non-standard grids. Desirable attributes of a grid for high-order spatial finite differencing are: (i) geometrical regularity; (ii) a homogeneous and approximately isotropic spatial resolution; (iii) a low proportion of the grid points where the numerical procedures require special customization (such as near coordinate singularities or grid edges). One family of grid arrangements which, to our knowledge, has never before been applied to numerical weather prediction, but which appears to offer several technical advantages, are what we shall refer to as "Fibonacci grids". They can be thought of as mathematically ideal generalizations of the patterns occurring naturally in the spiral arrangements of seeds and fruit found in sunflower heads and pineapples (to give two of the many botanical examples). These grids possess virtually uniform and highly isotropic resolution, with an equal area for each grid point. There are only two compact singular regions on a sphere that require customized numerics. We demonstrate the practicality of these grids in shallow water simulations, and discuss the prospects for efficiently using these frameworks in three-dimensional semi-implicit and semi-Lagrangian weather prediction or climate models.
Institute of Scientific and Technical Information of China (English)
陈树勇; 陈会员; 唐晓骏; 宋云亭; 曾令全
2013-01-01
The putting into operation of energy base, where wind power is bundled with thermal-generated power, can bring great economic benefits, meanwhile it will also leads to the variation of both security and stability in the power grid located in the energy base. It is hard to ensure stable operation of the power grid by only tripping conventional thermal generation units after certain serious faults or the cost of tripping conventional thermal generation units is too high. In allusion to it, firstly, the difference between the transient characteristics of thermal generation units and that of wind power generation units as well as the impacts of the two kinds of transient characteristics on system transient stability are analyzed; secondly, it is pointed out that there are two main reasons causing post-fault system instability: one of them is the accelerating energy produced during fault process and the another one is the sharp decline of the capability of outward power transmission system due to the weakening of outward power transmission channel; thirdly, an optimal scheme for tripping thermal units and wind power units after the serious faults is proposed. Simulation results of a certain energy base in West China, where the thermal-generated power is bundled with wind power, show that under the premise of ensuring post-fault secure and stable operation of the power grid, using the proposed optimal generator tripping scheme the quantity of generators to be tripped can be evidently reduced and the restoration characteristics of post-fault power grid can be improved, thus both security and economy of the power grid can be obviously enhanced.%风火打捆能源基地的投入运行,在带来巨大经济效益的同时也引起电网安全稳定性发生变化.某些严重故障后,仅切除常规火电机组难以保证系统稳定运行或代价过大.首先分析了风电机组和火电机组暂态特性的差异性以及各自对系统暂态稳定的影响.然后指
Chung, S. H.; Lee-Taylor, J.; Asher, W.; Hodzic, A.; Madronich, S.; Aumont, B.; Pankow, J. F.; Barsanti, K. C.
2012-12-01
A major weakness in current air quality and climate models is the ability to simulate secondary organic aerosol (SOA) levels and physiochemical properties accurately. A new approach to model SOA formation is the carbon number (nc) polarity grid (CNPG) framework. The CNPG framework makes use of a nc vs. polarity grid for representing relevant organic compounds and their time-dependent concentrations. The nc vs polarity grid is well suited for modeling SOA because nc together with some suitable measure of total molecular polarity provides the minimum yet sufficient formation for estimating the parameters required to calculate partitioning coefficients. Furthermore, CNPG allows consideration of the effects of variation in the activity coefficients of the partitioning compounds, variation in the mean molecular weight of the absorbing organic phase, water uptake, and the possibility of phase separation in the organic aerosol phase. In this work, we use the GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) chemistry mechanism to produce the chemical structures of SOA precursor oxidization products and their time-dependent concentrations. The SIMPOL group contribution method is used to calculate the enthalpy of vaporization ΔHvap for each product. The total molecular polarity is then calculated as ΔHvap,diff, the difference between each compound's ΔHvap and that of its carbon-number equivalent straight-chain hydrocarbon. The gas- and particle-phase concentrations of each compound are mapped onto the nc vs polarity grid as a function of time to evaluate the time evolution of SOA-relevant oxidation products and to help guide lumping strategies for reducing complexity. In addition to using ΔHvap,diff, use of other measures of polarity will also be explored. Initial SOA precursor studies include toluene (C7) + n-heptadecane (C17) and α-pinene, under atmospherically relevant conditions. Results will be discussed in the context of the
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.
Liu, Chang; Lv, Xiangyu; Guo, Li; Cai, Lixia; Jie, Jinxing; Su, Kuo
2017-05-01
With the increasing of penetration of distributed in the smart grid, the problems that the power loss increasing and short circuit capacity beyond the rated capicity of circuit breaker will become more serious. In this paper, a methodology (Modified BPSO) is presented for network reconfiguration which is based on hybrid approach of Tabu Search and BPSO algorithms to prevent the local convergence and to decrease the calculation time using double fitnesses to consider the constraints. Moreover, an average load simulated method (ALS method) load variation considered is proposed that the average load value is used to instead of the actual load to calculation. Finally, from a case study, the results of simulation certify the approaches will decrease drastically the losses and improve the voltage profiles obviously, at the same time, the short circuit capacity is also decreased into less the shut-off capacity of circuit breaker. The power losses won’t be increased too much even if the short circuit capacity constraint is considered; voltage profiles are better with the constraint of short circuit capacity considering. The ALS method is simple and calculated time is speed.
1974-01-01
One of the 150 lead grids used in the multiwire proportional chamber g-ray detector. The 0.75 mm diameter holes are spaced 1 mm centre to centre. The grids were made by chemical cutting techniques in the Godet Workshop of the SB Physics.
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.
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.
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
Directory of Open Access Journals (Sweden)
H. Hadj Abdallah
2005-09-01
Full Text Available This work presents a method for solving the problem of load flow in electric power systems including a wind power station with asynchronous generators. For this type of power station, the generated active power is only known and consequently the absorbed reactive power must be determined. So we have used the circular diagram at each iteration and by considering this node as a consuming node in the load flow program. Since the wind speed is not constant, the generated power is neither constant. To predict the state of the network in real time, we have used the artificial neural networks after a stage of training using a rich base of data.
Mechanism Research on Renewable Energy Generation and Integration in Smart Grid%智能电网环境下可再生能源发电并网机制研究
Institute of Scientific and Technical Information of China (English)
吕春泉; 厉一梅; 刘宏志; 刘清宇; 张鲲; 许文秀; 曾鸣
2011-01-01
The development of the smart grid and renewable energy generation technology is one of the important solutions to energy crisis,and meanwhile,the construction of smart grid also provides potential opportunities for the safe renewable energy integration into grid.Based on the basic characteristics of smart grid and renewable energy,research was made related with renewable energy integration into smart grid,and the main operation mechanisms were proposed to provide the theoretical support for grid-connected renewable energy generation.%发展智能电网及可再生能源发电技术逐渐成为解决当前能源危机的重要途径之一,同时智能电网的建设也为可再生能源发电的安全并网提供了可能。基于智能电网和可再生能源的基本特征,分析研究了智能电网环境下可再生能源并网运行的相关问题,提出了可再生能源发电并网的主要运行机制,为可再生能源发电并网提供一定的理论支撑。
Directory of Open Access Journals (Sweden)
Fatemeh Azarinejadian
2014-10-01
Full Text Available Presenting proper and efficient energy management system (EMS in the Microgrids (MG is an important issue for gaining assurance to optimize energy usage based on price preference and system technical constraints. Nowadays by utilizing renewable energy resources and energy storage systems in MG, in addition to reducing the pollution caused by fossil fuels, the safety and power system reliability can also be improved. The proposed algorithm to implement an EMS shall increase the MG ability in both islanded and grid connected operating mode to supply non-responsive load demands from the economic points of view. Implementing EMS over the MG of Institute de Recerca on Energia de Catalunya (IREC based on artificial bee colony (ABC optimization approach to economic dispatch between various generation units, considering their offer price is main novelty of this paper. The obtained results from the proposed algorithm when compared with the EMS algorithm based on mixed integer non-linear programming (MINLP demonstrate the reduction of about 18% of the total generation; and it also improves the efficiency of the demand/ generation side management.
Directory of Open Access Journals (Sweden)
Lei Chen
2017-01-01
Full Text Available In regard to the rapid development of renewable energy sources, more and more photovoltaic (PV generation systems have been connected to main power networks, and it is critical to enhance their transient performance under short-circuit faults conditions. This paper proposes and studies the coordinated control of a flux-coupling-type superconducting fault current limiter (SFCL and a superconducting magnetic energy storage (SMES, to improve the fault ride through (FRT capability and smooth the power fluctuation of a grid-connected PV generation system. Theoretical analyses of the device structure, operating principle and control strategy are conducted, and a detailed simulation model of 100 kW class PV generation system is built in MATLAB/SIMULINK. During the simulations of the symmetrical and asymmetrical faults, the maximum power point tracking (MPPT control is disabled, and four different cases including without auxiliary, with SFCL, with SMES, and with SFCL-SMES, are compared. From the demonstrated results, the combination of without MPPT and with SFCL-SMES can more efficiently improve the point of common coupling (PCC voltage sag, inhibit the DC-link overvoltage and alleviate the power fluctuation. Finally, a preliminary parameter optimization method is suggested for the SFCL and the SMES, and it is helpful to promote their future application in the real PV projects.
Camera, Corrado; Bruggeman, Adriana; Hadjinicolaou, Panos; Michaelides, Silas; Lange, Manfred A.
2015-04-01
Space-time variability of precipitation plays a key role as a driver of many processes in different environmental fields like hydrology, ecology, biology, agriculture, and natural hazards. The objective of this study was to compare two approaches for statistical downscaling of precipitation from climate models. The study was applied to the island of Cyprus, an orographically complex terrain. The first approach makes use of a spatial temporal Neyman-Scott Rectangular Pulses (NSRP) model and a previously tested interpolation scheme (Camera et al., 2014). The second approach is based on the use of the single site NSRP model and a simplified gridded scheme based on scaling coefficients obtained from past observations. The rainfall generators were evaluated on the period 1980-2010. Both approaches were subsequently used to downscale three RCMs from the EU ENSEMBLE project to calculate climate projections (2020-2050). The main advantage of the spatial-temporal approach is that it allows creating spatially consistent daily maps of precipitation. On the other hand, due to the assumptions made using a stochastic generator based on homogeneous Poisson processes, it shows a smoothing out of all the rainfall statistics (except mean and variance) all over the study area. This leads to high errors when analyzing indices related to extremes. Examples are the number of days with rainfall over 50 mm (R50 - mean error 65%), the 95th percentile value of rainy days (RT95 - mean error 19%), and the mean annual rainfall recorded on days with rainfall above the 95th percentile (RA95 - mean error 22%). The single site approach excludes the possibility of using the created gridded data sets for case studies involving spatial connection between grid cells (e.g. hydrologic modelling), but it leads to a better reproduction of rainfall statistics and properties. The errors for the extreme indices are in fact much lower: 17% for R50, 4% for RT95, and 2% for RA95. Future projections show a
Institute of Scientific and Technical Information of China (English)
雷鹏
2014-01-01
one kind of single-phase off-grid household photovoltaic ( PV) generating appliance was researched in this paper.An off-grid household photovoltaic generating appliance is a device that is connected to home electrical loads directly and provides elec-tric power supply for family.%介绍一种单相离网式交流户用光伏发电装置的功能、结构，能直接与户用负载联接，独立对负荷供电。
A finite element approach to self-consistent field theory calculations of multiblock polymers
Ackerman, David M; Fredrickson, Glenn H; Ganapathysubramanian, Baskar
2016-01-01
Self-consistent field theory (SCFT) has proven to be a powerful tool for modeling equilibrium microstructures of soft materials, particularly for multiblock polymers. A very successful approach to numerically solving the SCFT set of equations is based on using a spectral approach. While widely successful, this approach has limitations especially in the context of current technologically relevant applications. These limitations include non-trivial approaches for modeling complex geometries, difficulties in extending to non-periodic domains, as well as non-trivial extensions for spatial adaptivity. As a viable alternative to spectral schemes, we develop a finite element formulation of the SCFT paradigm for calculating equilibrium polymer morphologies. We discuss the formulation and address implementation challenges that ensure accuracy and efficiency. We explore higher order chain contour steppers that are efficiently implemented with Richardson Extrapolation. This approach is highly scalable and suitable for s...
Plant-wide process monitoring based on mutual information-multiblock principal component analysis.
Jiang, Qingchao; Yan, Xuefeng
2014-09-01
Multiblock principal component analysis (MBPCA) methods are gaining increasing attentions in monitoring plant-wide processes. Generally, MBPCA assumes that some process knowledge is incorporated for block division; however, process knowledge is not always available. A new totally data-driven MBPCA method, which employs mutual information (MI) to divide the blocks automatically, has been proposed. By constructing sub-blocks using MI, the division not only considers linear correlations between variables, but also takes into account non-linear relations thereby involving more statistical information. The PCA models in sub-blocks reflect more local behaviors of process, and the results in all blocks are combined together by support vector data description. The proposed method is implemented on a numerical process and the Tennessee Eastman process. Monitoring results demonstrate the feasibility and efficiency.
Directory of Open Access Journals (Sweden)
F. Malek
2014-08-01
Full Text Available The chemical recycling of the poly(ethylene terephthalate, (PET, has been successfully carried out by glycolysis in the presence of bis (2-hydroxyethyl terephthalate (BHET resulting in the formation of hydroxytelechelic oligomers. These oligomers were then treated with carboxytelechelic poly(ε-caprolactone oligomers of Mn = 2300 and Mn = 730 g•mol–1 molecular weight, in the absence or presence of the titanium tetrabutyloxide (Ti(OBu4 as a catalyst to get multiblock copolyesters. The chemical structure of the synthesized copolyesters was investigated by size exclusion chromatography (SEC and proton Nuclear Magnetic Resonance (1H NMR spectroscopy. Moreover the differential scanning calorimetry (DSC was used to explore their thermal properties. The ester-ester interchange reaction was observed between the two oligopolyesters, was studied and discussed in detail.
Sequence-controlled methacrylic multiblock copolymers via sulfur-free RAFT emulsion polymerization
Engelis, Nikolaos G.; Anastasaki, Athina; Nurumbetov, Gabit; Truong, Nghia P.; Nikolaou, Vasiliki; Shegiwal, Ataulla; Whittaker, Michael R.; Davis, Thomas P.; Haddleton, David M.
2017-02-01
Translating the precise monomer sequence control achieved in nature over macromolecular structure (for example, DNA) to whole synthetic systems has been limited due to the lack of efficient synthetic methodologies. So far, chemists have only been able to synthesize monomer sequence-controlled macromolecules by means of complex, time-consuming and iterative chemical strategies such as solid-state Merrifield-type approaches or molecularly dissolved solution-phase systems. Here, we report a rapid and quantitative synthesis of sequence-controlled multiblock polymers in discrete stable nanoscale compartments via an emulsion polymerization approach in which a vinyl-terminated macromolecule is used as an efficient chain-transfer agent. This approach is environmentally friendly, fully translatable to industry and thus represents a significant advance in the development of complex macromolecule synthesis, where a high level of molecular precision or monomer sequence control confers potential for molecular targeting, recognition and biocatalysis, as well as molecular information storage.
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.
Boelens, O.J.; Laban, M.; Beek, van C.M.; Leeden, van der R.
2001-01-01
In this report the contribution of the National Aerospace Laboratory NLR to the ’CFD Drag Pre- diction Workshop’ organized by the AIAA in Anaheim, CA, on June 9-10, 2001, is presented. This contribution consists of both the results of all test cases and a discussion on the accurate computation of dr
1992-10-01
AS A RELAXATION SCHEME Consider solving Equation (61) using the Gauss- Seidel method . In Equation (61) D is a block diagonal matrix, M+ is a block...zero, the Gauss- Seidel method is D 1’m + 1.m =-Rn+1.mDX1 - [-* Xi- Im+I. (66) After completing this forward pass the Xl-m are known, and a backward
Boccard, Julien; Rudaz, Serge
2016-05-12
Many experimental factors may have an impact on chemical or biological systems. A thorough investigation of the potential effects and interactions between the factors is made possible by rationally planning the trials using systematic procedures, i.e. design of experiments. However, assessing factors' influences remains often a challenging task when dealing with hundreds to thousands of correlated variables, whereas only a limited number of samples is available. In that context, most of the existing strategies involve the ANOVA-based partitioning of sources of variation and the separate analysis of ANOVA submatrices using multivariate methods, to account for both the intrinsic characteristics of the data and the study design. However, these approaches lack the ability to summarise the data using a single model and remain somewhat limited for detecting and interpreting subtle perturbations hidden in complex Omics datasets. In the present work, a supervised multiblock algorithm based on the Orthogonal Partial Least Squares (OPLS) framework, is proposed for the joint analysis of ANOVA submatrices. This strategy has several advantages: (i) the evaluation of a unique multiblock model accounting for all sources of variation; (ii) the computation of a robust estimator (goodness of fit) for assessing the ANOVA decomposition reliability; (iii) the investigation of an effect-to-residuals ratio to quickly evaluate the relative importance of each effect and (iv) an easy interpretation of the model with appropriate outputs. Case studies from metabolomics and transcriptomics, highlighting the ability of the method to handle Omics data obtained from fixed-effects full factorial designs, are proposed for illustration purposes. Signal variations are easily related to main effects or interaction terms, while relevant biochemical information can be derived from the models.
Directory of Open Access Journals (Sweden)
Sharmin Sobhan
2016-06-01
Full Text Available 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 introduction on renewable energy and its importance is followed by present energy state in Bangladesh and prospect of biogas electrification technology, specially focused on poultry litter base system. Theoretical foundations on formation of biogas and electricity generation process are also presented. Main objective of the study is to diminish energy scarcity and connect rural people with the country’s development through electrification
2016-01-01
Environmental, economical and technical benefits of photovoltaic (PV) systems make them to be used in many countries. The main characteristic of PV systems is the fluctuations of their output power. Hence, high penetration of PV systems into electric network could be detrimental to overall system performance. Furthermore, the fluctuations in the output power of PV systems make it difficult to predict their output, and to consider them in generation planning of the units. The main objective of...
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.
PQ Control Based Grid Connected DG Systems
Directory of Open Access Journals (Sweden)
P Siva Srinivas1 ,
2015-10-01
Full Text Available Distributed generation (DG generally refer to small scale electric power generators produce electricity that is bound to an electric distribution system. Distributed generation systems such as photovoltaic (PV or wind energy systems are parts of the future smart grids. By applying intelligent techniques these future grids change as smarter grids. During the past few years electrical energy consumption to the investment is increased when compared to cost on transmission and distribution resulting in compromised reliability and high energy costs. So there is need to change from conventional grid to smart grid. Micro grids consist of small power sources called distributed generation system. Many distributed generation systems such as photovoltaic systems are grid interfaced through power electronic voltage source inverters. In this paper a boost inverter technique is explained and distributed generation sources such as PV and fuel cell are connected in series with the help of PQ controller technique the above system is evaluated.
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
Popovic, Zorana B.; Kim, Moonil; Rutledge, David B.
1988-01-01
Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not require an external locking signal, and the combining is done in free space. In addition, the loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequency-locking without an external locking signal, with an ERP of 37 W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.
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...
光伏并网发电实验系统设计%Design of experimental system for grid-connected photovoltaic power generation
Institute of Scientific and Technical Information of China (English)
刘佐濂; 杨汝; 何清平; 崔海霞
2011-01-01
设计开发了1套光伏并网发电实验系统.该系统由太阳能电池板及控制器、模拟负载、PC机和参数测量设备组成,系统可独立运行和模拟并网运行,控制器电路采用DC/DC/AC架构,实验装置可以测量系统的最大功率点跟踪能力、频率跟踪能力、逆变器的效率和逆变器的失真度等重要指标,具有二次开发功能,适合学生开展设计性实验.系统采用开放形式,直观性好,针对性强,结构原理清楚.%A experimental system for grid-connected photovoltaic power generation is designed. It consists of solar panels, simulating load, PC and a measuring equipment of parameter. The system can operate independently and simulate grid-connected operation. DC/DC/AC structure is applied to main control circuit. Some important indexes are measured by this experimental system, such as the capacities of maximum power point tracking and frequency tracking, the efficiency and the distortion of the inverter, etc. The secondary developing function of the system suits students to carry out the designing experiments. This system applies open form; there is good visuality, strong relevance and clear structure.
Foster, Ian
2001-08-01
The term "Grid Computing" refers to the use, for computational purposes, of emerging distributed Grid infrastructures: that is, network and middleware services designed to provide on-demand and high-performance access to all important computational resources within an organization or community. Grid computing promises to enable both evolutionary and revolutionary changes in the practice of computational science and engineering based on new application modalities such as high-speed distributed analysis of large datasets, collaborative engineering and visualization, desktop access to computation via "science portals," rapid parameter studies and Monte Carlo simulations that use all available resources within an organization, and online analysis of data from scientific instruments. In this article, I examine the status of Grid computing circa 2000, briefly reviewing some relevant history, outlining major current Grid research and development activities, and pointing out likely directions for future work. I also present a number of case studies, selected to illustrate the potential of Grid computing in various areas of science.
Equivalent Simplification Method of Micro-Grid
Directory of Open Access Journals (Sweden)
Cai Changchun
2013-09-01
Full Text Available 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 performed for the test of the equivalent model of micro-grid. The simulation results show that the equivalent model of micro-grid is effective, and the dynamic of equivalent model is similar with the detailed model of micro-grid. The equivalent simplification method for the micro-grid network and distributed components is suitable for the study of micro-grid.
Joint Grid System Used in Embedding Technique
Institute of Scientific and Technical Information of China (English)
李孝伟; 范绪箕
2003-01-01
The joint grid system, which consists of the developed collar grid, the virtual grid and other grids, wasused in the embedding technique to solve the problem of finding interpolating cells of the internal and externalboundary points near the joint regions. With different boundary plane generated along different fixed surface, thecollar grid obtained using hyperbolic partial equations can ensure to generate high-quality grids and to provide realinterpolating cells for the boundary points in the blanking regions. The virtual grid was used to convert solid wallboundary conditions into an interface condition, however, no fluid flow computations were conducted within thevirtual grid. The computational result of body-strake-wing shows that the current developed embedding techniquewith joint grid system can effectively treat the geometry and can more accurately predict the flow over complexcon-figuration with intersecting surfaces.
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.
Institute of Scientific and Technical Information of China (English)
Chi Wu; Zuo-wei Xie; Guang-zhao Zhang; Guo-fu Zi
2001-01-01
It had very long been a dream in polymer science to synthesize long multi-block polymer chains with an ordered chain sequence and controllable block lengths. Using ionic or living free radical polymerization or furnishing each end of polymer blocks with a reactive functional group, one can only prepare heteropolymer chains with few long blocks, such as diblock and triblock copolymers. The most plausible result so far was a pentablock copolymer. Recently, using a combination of polymer physics and synthetic chemistry, we have invented self-assembly assisted polycondensation (SAAP). This communication reports the results of using this novel method to connect 10-100 triblock polymer chains together to form long multi-block heteropolymer chains with an ordered sequence and controllable block lengths.``
Energy Technology Data Exchange (ETDEWEB)
Metzger, C. [Netzkomponenten, Qualitaetssicherung, EAM Energie AG, Kassel (Germany); Nestle, D. [Bereich Anlagentechnik und Leistungselektronik, Inst. fuer Solare Energieversorgungstechnik (Iset) e.V., Kassel (Germany)
2005-02-21
Due to continuous increase of decentralized energy generation (DEG), e.g. photovoltaic devices, smallest cogeneration plants, grid instability can occure in case of emergency supply by Diesel generators. In this case the device runs the risk to be pushed away from the grid. So for a stable grid operation a monitoring system is installed, which recognizes network instability, and when the grid becomes stable again, the inverter connects the DEG with the normal operating power grid. Test operation and transient cases are discussed in detail in this contribution. (GL) [German] Durch die stetige Zunahme von dezentralen Energieerzeugern, z.B. Photovoltaik-Anlagen, Kleinst-BHKW, kann es bei der Ersatzstromversorgung durch das Dieselaggregat zu Netz-Stabilitaetsproblemen kommen. Hier besteht die Gefahr, dass das Aggregat durch die dezentralen Erzeuger vom Netz gedraengt wird. Um dies zu verhindern, sind organisatorische Massnahmen oder neue Betriebsweisen der Aggregate erforderlich, die im Rahmen des Projektes Sidena (Sicherheitsaspekte dezentraler netzgekoppelter Energieerzeugungsanlagen) zusammen mit dem Institut fuer Solare Energieversorgungstechnik e. V. (Iset) untersucht wurden. (orig.)
Institute of Scientific and Technical Information of China (English)
王琬; 曾博; 刘宗歧; 张建华
2011-01-01
This paper reveals influence mechanism and operation theory of grid- connected photovoltaic (PV) generation on traditional power grid planning modes, and analyzes the improvement in security, reliability, economics and environmental benefits of power grid with grid - connected PV generation. A series of comprehensive quantitative indices, such as remission degree of power transmission, the improvement rate of system voltage and environment, are proposed to establish a comprehensive evaluation indices system for PV generation grid - connected planning. A new methodology to evaluate the stability degree of solar energy by introducing the concepts of unavailability frequency and average unavailability duration of solar resource is proposed. The weights are determined based on information entropy method, and analytical hierarchy process (AHP) is used to comprehensively evaluate PV generation grid - connected planning. Simulation results show that the proposed evaluation system can reflect the influences of grid - connected PV generation on power grid planning and operation effectively, which provides important reference for the further practices.%在揭示光伏发电并网对传统电网规划模式的影响机制与作用原理的基础上,深入分析光伏电源接入对电网安全性、可靠性、经济性、环境效益的改善效果,提出传输功率缓解度、系统电压改善率、环境改善率等一系列综合性量化指标,构建了一套较完整的光伏发电并网规划综合评价指标体系.提出了光能不可用频率和光能不可用平均持续时间两项新指标以评价光伏系统能量供给的稳定程度.采用基于信息熵修正的权重确定方法,并利用群决策层次分析法实现对光伏发电并网规划的综合评判决策.仿真计算结果表明,本文方法能够全面、有效地反映光伏电源并网后对电网规划运行的影响,可为灵活规划光伏电源位置和容量提供重要的参考依据.
Synchrony-optimized power grids
Pinto, Rafael S
2014-01-01
We investigate synchronization in power grids, which we assume to be modeled by a network of Kuramoto oscillators with inertia. More specifically, we study the optimization of the power grid topology to favor the network synchronization. We introduce a rewiring algorithm which consists basically in a hill climb scheme where the edges of the network are swapped in order enhance the main measures of synchronization. As a byproduct of the optimization algorithm, we typically have also the anticipation of the synchronization onset for the optimized network. We perform several robustness tests for the synchrony-optimized power grids, including the impact of consumption peaks. In our analyses, we investigate synthetic random networks, which we consider as hypothetical decentralized power generation situations, and also a network based in the actual power grid of Spain, which corresponds to the current paradigm of centralized power grids. The synchrony-optimized power grids obtained by our algorithm have some intere...
Energy Technology Data Exchange (ETDEWEB)
Erge, T.; Bohnenstengel, J.; Bopp, G.; Dornburg, H.; Reimelt, R.; Roessler, E.; Schaetzle, R.; Wimmer, D.; Wittek, I.
1997-12-31
This BMBF-sponsored project, which was carried out from August 1994 to April 1997, has achieved its goal of characterizing the electromagnetic properties of solar generators of grid-coupled photovoltaic power systems. The focus of the study was on systems and components that are typically used in the household sector (range of power output 1-10 kW{sub p}), and which have become widely distributed, especially also among private house-owners and builders, not lastly by the 1000-roofs photovoltaics programme. As far as time permitted within the framework of this project, current trends in inverter technology (string-type inverters and modular inverters) were also taken into account.- The main conclusion from the project is as follows: Photovoltaic plants are principally capable of generating higher-frequency electromagnetic disturbances (both in line-transmitted and radiated form). Moreover, given certain boundary conditions, these disturbances may be emitted to the environment both via the AC side and via the DC side/solar generator. (orig./AKF) [Deutsch] In dem seit August 1994 bis April 1997 laufenden BMBF-Projekt wurde das Ziel einer Charakterisierung der elektromagnetischen Eigenschaften des Solargenerators netzgekoppelter photovoltaischer Stromversorgungsanlagen erreicht. Schwerpunkt der Untersuchungen waren dabei Anlagen und Komponenten, die typischerweise im Hausbereich eingesetzt werden (Leistungsbereich 1-10 kW{sub p}) und die nicht zuletzt durch das 1000 Daecher-Photovoltaikprogramm weite Verbreitung gerade auch bei privaten Hauseigentuemern und Bauherren gefunden haben. Soweit im Rahmen der Projektlaufzeit noch moeglich, wurden auch aktuelle Tendenzen der Wechselrichtertechnik (String- und Modulwechselrichter) beruecksichtigt. Wesentlichstes Ergebnis der Projektarbeiten ist die Aussage, dass photovoltaische Anlagen grundsaetzlich in der Lage sind, hoeherfrequente elektromagnetische Stoerungen (sowohl leitungsgebunden als auch gestrahlt) zu erzeugen, und
光伏发电系统不对称故障功率控制%Power Control of Photovoltaic Generation system under Unbalanced Grid Faults
Institute of Scientific and Technical Information of China (English)
夏刚; 杜跃明; 楼晓轩; 华赟; 李芳; 沈琦; 王强钢; 周念成
2013-01-01
The the characteristics of instance output power of photovoltaic inverters is analyzed under unbalanced grid faults and the power control algorithm of photovoltaic generation is put forward based on the derivation of total harmonic distortion of instruction current. The optimal parameters model of photovoltaic generation is then established with minimum integrated fluctuation amplitude of the active and reactive power as a goal when the restriction of output current harmonic distortion of photovoltaic inverters is taken into account. Finally, the overall model of photovoltaic generation system based on deadbeat current tracking is realized and the feasibility of proposed control strategy is verified with PSCAD/EMTDC simulation software.%研究电网不对称故障下光伏逆变器的瞬时输出功率特性，结合指令电流的总谐波畸变率的解析推导，提出光伏发电的功率控制算法。考虑光伏逆变器输出电流谐波畸变率限值约束，以有功和无功功率波动的综合幅值最小为目标，建立光伏发电功率控制参数的优化模型。基于无差拍电流跟踪建立光伏发电系统整体模型，利用PSCAD/EMTDC仿真平台验证了该控制策略的可行性。
Ramazani, F; Hiemstra, C; Steendam, R; Kazazi-Hyseni, F; Van Nostrum, C F; Storm, G; Kiessling, F; Lammers, T; Hennink, W E; Kok, R J
2015-09-01
Sunitinib is a multi-targeted receptor tyrosine kinase (RTK) inhibitor that blocks several angiogenesis related pathways. The aim of this study was to develop sunitinib-loaded polymeric microspheres that can be used as intravitreal formulation for the treatment of ocular diseases. A series of novel multi-block copolymers composed of amorphous blocks of poly-(D,L-lactide) (PDLLA) and polyethylene glycol (PEG) and of semi-crystalline poly-(L-lactide) (PLLA) blocks were synthesized. Sunitinib-loaded microspheres were prepared by a single emulsion method using dichloromethane as volatile solvent and DMSO as co-solvent. SEM images showed that the prepared microspheres (∼ 30 μm) were spherical with a non-porous surface. Sunitinib-loaded microspheres were studied for their degradation and in-vitro release behavior. It was found that increasing the percentage of amorphous soft blocks from 10% to 30% accelerated the degradation of the multi-block copolymers. Sunitinib microspheres released their cargo for a period of at least 210 days by a combination of diffusion and polymer erosion. The initial burst (release in 24h) and release rate could be tailored by controlling the PEG-content of the multi-block copolymers. Sunitinib-loaded microspheres suppressed angiogenesis in a chicken chorioallantoic membrane (CAM) assay. These microspheres therefore hold promise for long-term suppression of ocular neovascularization.
Saiz, P.; Andreeva, J.; Cirstoiu, C.; Gaidioz, B.; Herrala, J.; Maguire, E. J.; Maier, G.; Rocha, R.
2008-07-01
Thanks to the Grid, users have access to computing resources distributed all over the world. The Grid hides the complexity and the differences of its heterogeneous components. In such a distributed system, it is clearly very important that errors are detected as soon as possible, and that the procedure to solve them is well established. We focused on two of its main elements: the workload and the data management systems. We developed an application to investigate the efficiency of the different centres. Furthermore, our system can be used to categorize the most common error messages, and control their time evolution.
On Multigrid for Overlapping Grids
Energy Technology Data Exchange (ETDEWEB)
Henshaw, W
2004-01-13
The solution of elliptic partial differential equations on composite overlapping grids using multigrid is discussed. An approach is described that provides a fast and memory efficient scheme for the solution of boundary value problems in complex geometries. The key aspects of the new scheme are an automatic coarse grid generation algorithm, an adaptive smoothing technique for adjusting residuals on different component grids, and the use of local smoothing near interpolation boundaries. Other important features include optimizations for Cartesian component grids, the use of over-relaxed Red-Black smoothers and the generation of coarse grid operators through Galerkin averaging. Numerical results in two and three dimensions show that very good multigrid convergence rates can be obtained for both Dirichlet and Neumann/mixed boundary conditions. A comparison to Krylov based solvers shows that the multigrid solver can be much faster and require significantly less memory.
Directory of Open Access Journals (Sweden)
Minh Quan Duong
2015-06-01
Full Text Available A common problem in wind power plants involves fixed-speed wind turbines. In fact, being equipped with a squirrel-cage induction generator (SCIG, they tend to drain a relevant amount of reactive power from the grid, potentially causing voltage drops and possible voltage instability. To improve SCIG power quality and transient stability, this paper investigates a new control strategy for pitch angle control based on proportional-integral (PI controller and a fuzzy logic controller (FLC, considering both normal and fault ride-through (FRT schemes. In the literature, often, the mechanical torque output is assumed constant for a specific wind speed. This might not be accurate, because the mechanical torque-speed typical of a wind turbine depends also on the power coefficient or pitch angle. In this paper, an analytic model of transient stability is proposed using the equivalent circuit of the SCIG and using the concepts of stable and unstable electrical-mechanical equilibrium. The method has been evaluated by comparing the results obtained by the analytic method with the dynamic simulation. The results show that the proposed hybrid controller is effective at smoothing the output power and complying with FRT requirements for SCIG in the power system.
Institute of Scientific and Technical Information of China (English)
詹红霞; 王秋红; 彭勇
2012-01-01
针对光伏发电系统并网技术的特点,分析了系统并网后对配电网继电保护的影响,提出了通过利用母线保护物理对象的函数关系来构建光伏发电系统并网的交流母线保护的ANN模型的新方法。采用该方法解决了光伏发电系统并网造成交流母线保护误动作的问题。%Based on the characteristics of grid-connected technology of photovoltaic power generation system,the effect of grid-connected on relay protection of distribution network is analyzed.A new method for constructing ANN model of alternating bus protection of grid-connected photovoltaic power generation system by using function relationship of physical object is proposed.The malfunction problem of alternating bus protection of grid-connected photovoltaic power generation system can be resolved by the proposed method.
Energy Technology Data Exchange (ETDEWEB)
Hoeckel, M.; Haldi, R.
2003-07-01
This is the fourth 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 third appendix to the main report describes five types of distributed production facilities - photovoltaics (PV), wind power, hydropower, combined heat and power units and fuel-cell-based power generation. Each of these types of power generation equipment is briefly described and its particular characteristics are discussed. In particular, the effects of PV inverters on the mains is examined, as are the active and reactive power aspects of hydropower installations. Also the state-of-the-art of wind technologies are looked at and the various types of combined heat and power units and fuel cells are described.
Shasharina, Svetlana; Wang, Nanbor
2004-11-01
Simulations and experiments in the fusion and plasma physics community generate large datasets at remote sites. Visualization and analysis of these datasets are difficult because of the incompatibility among the various data formats adopted by simulation, experiments, and analysis tools, and the large sizes of analyzed data. Grids and Web Services technologies are capable of providing solutions for such heterogeneous settings, but need to be customized to the field-specific needs and merged with distributed technologies currently used by the community. This paper describes how we are addressing these issues in the Fusion Grid Service under development. We also present performance results of relevant data transfer mechanisms including binary SOAP, DIME, GridFTP and MDSplus and CORBA. We will describe the status of data converters (between HDF5 and MDSplus data types), developed in collaboration with MIT (J. Stillerman). Finally, we will analyze bottlenecks of MDSplus data transfer mechanism (work performed in collaboration with General Atomics (D. Schissel and M. Qian).
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.
Energy Technology Data Exchange (ETDEWEB)
Neuner, R. [SCHOTT Solar GmbH, Alzenau (Germany). PV Building Solutions
2008-07-01
SCHOTT Solar is the manufacturer of wafers, solar cells and solar current modules. It also produces power modules for all relevant applications and provides modules and components for the building integration of photovoltaic systems (BIPV). The solar current technology photovoltaic system (PV) will take a top position in the network with the other innovative technologies and products for using the preference energy carriers ''solar energy, wind power, biomass and water power''. More than 70% of the solar current applications worldwide are already ''building-oriented''. However, clearly less then 1% are ''building-integrated'' in terms of their function. Solar current power modules in standard geometrics and standard design are predominantly assembled and operated on inclined and flat roofs above the conventional roofing material as additional independent energy systems in the grid. Measured, i.e. non-standardised modules for facade integration and glass roofing, e.g. of train station halls or entry portals are becoming more interesting for architects and city planners. Free surface plants are justified for large plant construction of photovoltaic systems in the power segment - typically above 200 kWp and a surface demand of more than 2,000 m-2 per system. Based on the primary energy solar power the building envelope is the carrier of corresponding solar-technical energy converters in times of decentral energy generation and supply. Apart from the passive use of the solar radiation energy the active solar current technology ''photovoltaic'' plays a predominant role. The operators of photovoltaic plants, private and public investors, architects and planners expect financial planning security of appropriate photovoltaic input tariffs as well as high production security. Solar current plants with high-quality photovoltaic components offer amongst other the chance (1) to extend the decentral
Automatic Transaction Compensation for Reliable Grid Applications
Institute of Scientific and Technical Information of China (English)
Fei-Long Tang; Ming-Lu Li; Joshua Zhexue Huang
2006-01-01
As grid technology is expanding from scientific computing to business applications, service oriented grid computing is aimed at providing reliable services for users and hiding complexity of service processes from them. The grid services for coordinating long-lived transactions that occur in business applications play an important role in reliable grid applications. In this paper, the grid transaction service (GridTS) is proposed for dealing with long-lived business transactions. We present a compensation-based long-lived transaction coordination algorithm that enables users to select results from committed sub-transactions. Unlike other long-lived transaction models that require application programmers to develop corresponding compensating transactions, GridTS can automatically generate compensating transactions on execution of a long-lived grid transaction. The simulation result has demonstrated the feasibility of GridTS and effectiveness of the corresponding algorithm.
Institute of Scientific and Technical Information of China (English)
马草原; 孙展展; 葛森; 蒋峰景
2016-01-01
设计并改进供电效率和综合供电效率评估指标，运用复杂网络理论分析直接接入主电网的分布式电源对电网供电效率的影响。基于综合供电效率指标对含分布式发电的电网进行不同故障模式下的脆弱度评估，且对IEEE39节点系统进行仿真，比较分析不同故障模式下在分布式发电加入前后的电网脆弱度，以验证指标的有效性。定性评估分布式发电接入后对电网脆弱度的影响，对实现高效、清洁能源的大力发展和应用具有重要的理论和现实意义。%This paper designs and improves the evaluation index of power supply efficiency and integrated power effi -ciency , and the influence on the power supply efficiency of distributed generation directly access to the main power grid is analyzed by using complex network theory .The vulnerability assessment under different fault modes of power grid containing distributed generation is done based on an integrated power supply efficiency index , and the IEEE39 nodes system is tested as well , and comparatively analyze the power grid vulnerability at distributed generation to join before and after under different fault modes in order to verify the validity of indicators .The qualitative assessment of the impact on the grid vulnerability as the distributed generation access to grid has important theoretical and practical significance to develop and apply the high -efficient and clean energy .
Multi-Block Enhancement for Lagrangian Dendritic Mesh setup in Altair5
Energy Technology Data Exchange (ETDEWEB)
Douglass, Rodney W [Los Alamos National Laboratory
2010-12-15
Initial mesh setup for an ASC mUlti-physics code at LANL is done using Altair5. Altair5 assumes that the final mesh is composed of logical structured mesh blocks linked together at mesh boundaries to form, ultimately, an unstructured mesh. Within these blocks, meshes may have dendrites, that is, local regions where two zones share common edges (in two-dimensions, or faces in three-dimensions) with a single zone. In many cases, contiguous subsets of the initial set of blocks may have the same material assigned to them, but without smoothing the mesh would form a computationally challenging initial mesh. Some of these blocks may also have zones with nodes on domain boundaries. This paper reports on the implementation of multiblock smoothing in Altair5, which allows for dendrites and for moving boundary nodes. Dendritic nodes are constrained to be located at the average of their neighbor nodes while boundary nodes are constrained to move along the boundary geometry. Two fundamentally different smoothing methods were implemented. First, a variational principle is presented that balances zonal size and distortion via a user selected weighting with constraints imposed using penalty methods for dendritic nodes and Lagrange multipliers for boundary nodes. Second, the Laplace-Beltrami smoother is presented. This is a general elliptic smoother which can easily be modified to give Laplacian and Winslow-Crowley mesh smoothing. Results are shown for several test meshes of interest.
Process-directed self-assembly of multiblock copolymers: Solvent casting vs spray coating
Tang, Q.; Tang, J.; Müller, M.
2016-07-01
Using computer simulation of a soft, coarse-grained model and self-consistent field theory we investigate how collapsed, globular chain conformations in the initial stages of structure formation, which are produced by spray-coating, affect the single-chain structure and morphology of microphase-separated multiblock copolymers. Comparing spray-coated films with films that start from a disordered state of Gaussian chains, we observe that the collapsed molecular conformations in the initial stage give rise to (1) a smaller fraction of blocks that straddle domains (bridges), (2) a significant reduction of the molecular extension normal to the internal interfaces, and (3) a slightly larger lamellar domain spacing in the final morphology. The relaxation of molecular conformations towards equilibrium is very protracted for both processes - solvent casting and spray coating. These findings illustrate that the process conditions of the copolymer materials may significantly affect materials properties (such as mechanical properties) because the system does not reach thermal equilibrium on the relevant time scales.
Feron, Gilles; Ayed, Charfedinne; Qannari, El Mostafa; Courcoux, Philippe; Laboure, Hélène; Guichard, Elisabeth
2014-01-01
For human beings, the mouth is the first organ to perceive food and the different signalling events associated to food breakdown. These events are very complex and as such, their description necessitates combining different data sets. This study proposed an integrated approach to understand the relative contribution of main food oral processing events involved in aroma release during cheese consumption. In vivo aroma release was monitored on forty eight subjects who were asked to eat four different model cheeses varying in fat content and firmness and flavoured with ethyl propanoate and nonan-2-one. A multiblock partial least square regression was performed to explain aroma release from the different physiological data sets (masticatory behaviour, bolus rheology, saliva composition and flux, mouth coating and bolus moistening). This statistical approach was relevant to point out that aroma release was mostly explained by masticatory behaviour whatever the cheese and the aroma, with a specific influence of mean amplitude on aroma release after swallowing. Aroma release from the firmer cheeses was explained mainly by bolus rheology. The persistence of hydrophobic compounds in the breath was mainly explained by bolus spreadability, in close relation with bolus moistening. Resting saliva poorly contributed to the analysis whereas the composition of stimulated saliva was negatively correlated with aroma release and mostly for soft cheeses, when significant. PMID:24691625
Feron, Gilles; Ayed, Charfedinne; Qannari, El Mostafa; Courcoux, Philippe; Laboure, Hélène; Guichard, Elisabeth
2014-01-01
For human beings, the mouth is the first organ to perceive food and the different signalling events associated to food breakdown. These events are very complex and as such, their description necessitates combining different data sets. This study proposed an integrated approach to understand the relative contribution of main food oral processing events involved in aroma release during cheese consumption. In vivo aroma release was monitored on forty eight subjects who were asked to eat four different model cheeses varying in fat content and firmness and flavoured with ethyl propanoate and nonan-2-one. A multiblock partial least square regression was performed to explain aroma release from the different physiological data sets (masticatory behaviour, bolus rheology, saliva composition and flux, mouth coating and bolus moistening). This statistical approach was relevant to point out that aroma release was mostly explained by masticatory behaviour whatever the cheese and the aroma, with a specific influence of mean amplitude on aroma release after swallowing. Aroma release from the firmer cheeses was explained mainly by bolus rheology. The persistence of hydrophobic compounds in the breath was mainly explained by bolus spreadability, in close relation with bolus moistening. Resting saliva poorly contributed to the analysis whereas the composition of stimulated saliva was negatively correlated with aroma release and mostly for soft cheeses, when significant.
A dynamic multiblock approach to solving the unsteady Euler equations about complex configurations
Arabshahi, Abdollah
The objective is the development of a numerical method which can accurately and economically solve the unsteady Euler equations for three-dimensional flow fields around complex configurations, particularly a generic aircraft with a store in the captive and vertical launch position. A cell centered finite volume spatial discretization is applied to the three-dimensional, time-dependent, Euler equations written in general time-dependent curvilinear coordinates. Two algorithms are presented for solving the system of Euler equations. The first algorithm is based on flux-vector splitting while the second algorithm is based on flux-difference splitting using Roe averaged variables. For both algorithms, an implicit upwind biased approach is employed to integrate the spatially discretized equations in time. The multiblock technique utilizes the concept of decomposing the flow field between the surfaces of the configuration and some outer far field boundary into a set of blocks. Calculated results compared with experimental data indicate that the present Euler solver can calculate transonic flow fields efficiently and accurately over complex geometries. Furthermore, the results demonstrate how computational fluid dynamics (CFD) can be used to accurately simulate steady and, for the first time, unsteady fluid flow over a complete wing-pylon-store configuration with the store in the captive and vertical launch positions.
Release of small water-soluble drugs from multiblock copolymer microspheres: a feasibility study.
Sohier, J; van Dijkhuizen-Radersma, R; de Groot, K; Bezemer, J M
2003-03-01
Poly(ethylene glycol)-terephthalate/poly(butylene terephthalate) (PEGT/PBT) multiblock copolymer was investigated as a possible matrix for controlled delivery of small water-soluble drugs. Two molecules were selected as sustained release candidates from microspheres: leuprorelin acetate (peptide of Mw = 1270 D) and vitamin B(12) (Mw = 1355 D). First, vitamin B(12)-loaded microspheres were prepared using a double emulsion method and preparation parameters were varied (surfactant in the first emulsion and copolymer composition). The resulting microsphere structure, entrapment efficiency and release rate were evaluated. Vitamin B(12)-loaded microsphere parameters could easily be tailored to achieve specific requirements. The addition of surfactant in the first preparation process led to a significant increase of the microsphere entrapment efficiency, whereas the decrease of the PEGT copolymer content allowed the release rates from microspheres to be precisely decreased. However, leuprorelin acetate-loaded microspheres did not show the same characteristics when prepared with the same parameters, possibly because of a high water solubility discrepancy between the vitamin B(12) and the peptide. This study shows the suitability of PEGT/PBT microspheres as a controlled release system for vitamin B(12), but not for leuprorelin acetate. It also underlines the necessity of tailored development for each individual drug and emphasizes the risk of using model molecules. Copyright 2002 Elsevier Science B.V.
Numerical simulation of flow over backward-facing step using parallel multi-block compact method
Energy Technology Data Exchange (ETDEWEB)
Esfahanian, V.; Torabi, F.; Khajavi Rad, A.; Babaee, H. [Univ. of Tehran, Mechanical Engineering Dept., Tehran (Iran, Islamic Republic of)]. E-mail: evahid@ut.ac.ir
2005-07-01
In this study the accurate location of separation and reattachment points in the flow over backward-facing step have been determined for 100
Hadade, Ioan; di Mare, Luca
2016-08-01
Modern multicore and manycore processors exhibit multiple levels of parallelism through a wide range of architectural features such as SIMD for data parallel execution or threads for core parallelism. The exploitation of multi-level parallelism is therefore crucial for achieving superior performance on current and future processors. This paper presents the performance tuning of a multiblock CFD solver on Intel SandyBridge and Haswell multicore CPUs and the Intel Xeon Phi Knights Corner coprocessor. Code optimisations have been applied on two computational kernels exhibiting different computational patterns: the update of flow variables and the evaluation of the Roe numerical fluxes. We discuss at great length the code transformations required for achieving efficient SIMD computations for both kernels across the selected devices including SIMD shuffles and transpositions for flux stencil computations and global memory transformations. Core parallelism is expressed through threading based on a number of domain decomposition techniques together with optimisations pertaining to alleviating NUMA effects found in multi-socket compute nodes. Results are correlated with the Roofline performance model in order to assert their efficiency for each distinct architecture. We report significant speedups for single thread execution across both kernels: 2-5X on the multicore CPUs and 14-23X on the Xeon Phi coprocessor. Computations at full node and chip concurrency deliver a factor of three speedup on the multicore processors and up to 24X on the Xeon Phi manycore coprocessor.
A finite element approach to self-consistent field theory calculations of multiblock polymers
Ackerman, David M.; Delaney, Kris; Fredrickson, Glenn H.; Ganapathysubramanian, Baskar
2017-02-01
Self-consistent field theory (SCFT) has proven to be a powerful tool for modeling equilibrium microstructures of soft materials, particularly for multiblock polymers. A very successful approach to numerically solving the SCFT set of equations is based on using a spectral approach. While widely successful, this approach has limitations especially in the context of current technologically relevant applications. These limitations include non-trivial approaches for modeling complex geometries, difficulties in extending to non-periodic domains, as well as non-trivial extensions for spatial adaptivity. As a viable alternative to spectral schemes, we develop a finite element formulation of the SCFT paradigm for calculating equilibrium polymer morphologies. We discuss the formulation and address implementation challenges that ensure accuracy and efficiency. We explore higher order chain contour steppers that are efficiently implemented with Richardson Extrapolation. This approach is highly scalable and suitable for systems with arbitrary shapes. We show spatial and temporal convergence and illustrate scaling on up to 2048 cores. Finally, we illustrate confinement effects for selected complex geometries. This has implications for materials design for nanoscale applications where dimensions are such that equilibrium morphologies dramatically differ from the bulk phases.
Institute of Scientific and Technical Information of China (English)
竺炜; 李娟; 蒋银华; 王琴英; 于文海
2015-01-01
Due to the lack of full quantified and monotonic grid security index, the grid security as inequality constraints cannot be optimized simultaneously in traditional economic power generation optimization models. The study found that the grid mapping elasticity potential energy not only can be used a grid security quantitative index, its change trend is also consistent with the grid power loss whenR/X of lines are less difference, and tends to be minimal when the lines load rate is balanced. Moreover, taken the grid mapping elasticity potential energy into consideration of the objective function of optimization model, it can achieve integrated optimization of generation economy, transmission economy and grid security. IEEE 39-bus system examples show the applicability of the integrated optimization model. The researches have practical implications to main power grid operation and planning.%由于缺乏全程量化及单调的电网安全性指标，传统的经济发电优化模型中，一般将安全性作为不等式约束条件，无法同时对电网安全性进行优化。研究发现，电网的映射弹性势能不但可以作为电网安全性的定量指标，当线路阻抗比相差不大时，其变化还与主网的网损变化同趋，且在线路负载率均衡时趋于最小；将其纳入经济发电优化模型的目标函数，可解决发输电经济性和电网安全性综合优化的问题。IEEE39节点系统算例验证了该综合优化模型的适用性。研究对主网的运行与规划具有现实意义。
Study on SPLL of Grid-connected PV Generation System%光伏并网发电系统软件锁相技术的研究
Institute of Scientific and Technical Information of China (English)
李文杰; 孙志毅; 何秋生
2012-01-01
光伏并网发电系统是利用太阳能的主要技术之一,并网逆变器是实现其与电网连接的核心部分.为使光伏并网逆变器逆变输出电流能够更好地跟踪电网电压基波,完成同步锁相功能,本文以1kW单相光伏并网逆变器为研究平台,阐述光伏并网逆变器的工作原理和系统结构,分析并网逆变器的并网控制技术,提出一种基于坐标变换的双park鉴相器的软件锁相技术,最后通过Matlab仿真验证该方法的可行性.%Grid-connected PV system is one of the technologies to use the solar energy. Grid-connected inverter is a core part of linking the grid. In order to make the output current of grid-connected inverter track the grid voltage fundamental and complete the Genlock, this paper uses 1 Kw single-phase photovoltaic grid-connected inverter as research platform. The paper describes the working principle of the photovoltaic grid-connected inverter and the system architecture. It analyzes the control technology of grid-connected inverter and proposes a software phase-locked loop of a dual-park phase detector based on coordinate transformation. At last it verifies the feasibility of this method by Matlab simulation.
基于并网光伏发电系统的反孤岛研究%Anti-Islanding Research Based on Photovoltaic Grid-Connected Generation System
Institute of Scientific and Technical Information of China (English)
肖建东; 于淼; 黄孝鹏; 沈友建; 陈煊之
2015-01-01
Solar photovoltaic grid generation is a kind of green energy and it is more and more used in the market However,in the process of its development the island fault as a common problem has discovered, how to detect the fault effectively is more and more important.The positive feedback active frequency drift is put forward in this paper can detect island failure timely,in order to verify the results,we use Matlab/simulink to simulat this method,you can see from the simulation results,this method can detect the phenomenon ef-fectively,and shorten the fault detection time.%太阳能光伏并网发电是一种绿色环保的电能，在市场中的应用也越来越多。然而在快速发展的过程中出现了孤岛故障这个较为普遍的问题，及时有效地检测出孤岛故障显得越来越重要。该文提出的正反馈主动式频率偏移法能够及时地检测孤岛故障。为了验证这一结果，用Matlab/simulink对该方法进行了仿真。从仿真结果中可以看到，此方法确实能够及时有效地检测出这一现象，而且缩短了故障检测时间。
Saiz, P; Rocha, R; Andreeva, J
2007-01-01
We are offering a system to track the efficiency of different components of the GRID. We can study the performance of both the WMS and the data transfers At the moment, we have set different parts of the system for ALICE, ATLAS, CMS and LHCb. None of the components that we have developed are VO specific, therefore it would be very easy to deploy them for any other VO. Our main goal is basically to improve the reliability of the GRID. The main idea is to discover as soon as possible the different problems that have happened, and inform the responsible. Since we study the jobs and transfers issued by real users, we see the same problems that users see. As a matter of fact, we see even more problems than the end user does, since we are also interested in following up the errors that GRID components can overcome by themselves (like for instance, in case of a job failure, resubmitting the job to a different site). This kind of information is very useful to site and VO administrators. They can find out the efficien...
Ruggieri, F
2001-01-01
An overview of the objectives and status of the DataGrid Project is presented, together with a brief introduction to the Grid metaphor and some references to the Grid activities and initiatives related to DataGrid. High energy physics experiments have always requested state of the art computing facilities to efficiently perform several computing activities related with the handling of large amounts of data and fairly large computing resources. Some of the ideas born inside the community to enhance the user friendliness of all the steps in the computing chain have been, sometimes, successfully applied also in other contexts: one bright example is the World Wide Web. The LHC computing challenge has triggered inside the high energy physics community, the start of the DataGrid Project. The objective of the project is to enable next generation scientific exploration requiring intensive computation and analysis of shared large-scale databases. (12 refs).
Institute of Scientific and Technical Information of China (English)
黎金英; 艾欣; 邓玉辉
2015-01-01
In order to realize voltage and power control in microgrid,aiming at the diversity of micro generation sources,studies the distributed generation models of photovoltaic and fuel cell and their impact on micro grid,puts forward the hierarchical control strategy based on revised droop control method and feed back controller such as outer voltage loop,inner current loop and power loop for distributed generations in micro grid,using Matlab/Simulink simulation system,analyzes the operation characteristic of micro-grid in islanding and grid-connecting mode and change rule of power,frequency and voltage of micro grid under different work environment of the distributed generations, verifies the validity of hierarchical control strategy. The result shows that the hierarchical control strategy can make better coordination betwween the distributed generation, satisfies the requirements of power quality and operation stability of micro grid for it.%为了实现对微电网的电压与功率的控制,针对微电源类型的差异性,通过对光伏及燃料电池等分布式电源建立数学模型并进行仿真分析,研究其对微电网的影响.提出了基于电压外环、电流内环和功率环等反馈控制器和改进的下垂控制方法的微电网分布式电源分层控制策略.利用Matlab/simulink仿真系统,通过在并网和孤岛两种模式中微电网的运行特性及各分布式电源在不同工作环境下微电网的功率、频率和电压曲线的变化规律的分析,验证了分层控制策略的有效性.结果表明:分层控制策略能够使各分布式电源之间较好地协调,满足微电网对其运行稳定性和电能质量的要求.
电网跌落下双馈感应风力发电机的研究%A Research of Doubly-fed Induction Generator during Power Grid Voltage Dips
Institute of Scientific and Technical Information of China (English)
邬冬临; 佘岳; 胡婵娟; 谭宇; 杨印博
2012-01-01
根据风电场接入电网的规定，在电网发生故障的情况下风力发电机组应能保持与电网的连接。电网电压跌落是电网故障常见的情况之一。根据低电压穿越技术的基本特点，本文以双馈感应发电机组（DFIG）作为研究对象。通过改进转子侧的控制策略和增加Crowbar保护电路来实现低电压穿越并且搭建了DFIGMATLAB／SIMULINK仿真模型。通过仿真研究表明，改进的控制策略能使DFIG在电网跌落时实现不间断运行．验证了模型的合理性及控制策略的可行性，有效提高了DFIG风电机组运行的可靠性。%According to the provisions of wind farms connected to the grid, in case of power grid faults the wind generator need to be capable of maintaining a wind turbine with grid connection. Voltage dips is often the case of power grid faults. According to the low voltage ride through the basic principles of technology, a study for double-fed induction generator (DFIG) in this paper, it achieve low voltage ride through during voltage dip by improving the rotor side control strategy and the Crowbar protection circuitry, build a DFIG MATLAB / SIMULINK simulation model. The simulation studies show that the improved control strategy can DFIG grid drops in continuous operations to verify the model is reasonable and feasible control strategies, improve the operation of DFIG Wind turbine reliability.
Energy Technology Data Exchange (ETDEWEB)
Zumaran, David Richard Orosco
2000-12-01
This work presents an analysis of economic, tariff and regulating issues related to the introduction of Grid Connected Photovoltaic Systems in a deregulated electric market context; a case study for the peruvian electric market is realized. Based on the pricing system of the electric market, it is developed an economic assessment model that can be used by institutions interested in promoting this technology for generating electricity. (author)
Institute of Scientific and Technical Information of China (English)
刘然; 张欣媛; 郄亚娜; 吕庆; 赵世伟
2015-01-01
Simulating the process of blast furnace ironmaking through mathematical models is an effective way of new technology research and development.As an important pre-treatment process,numerical grid generation process technology is a prerequisite for the simulation of the blast furnace.Grid quality has an important impact on the blast furnace model simulation accuracy,efficiency and convergence.Therefore, the establishment of high-quality grid is very important for solving the mathematical model of blast furnace.A new method for grids-generation of balst furnace mathematical model based on body-fitted coordinate (BFC)is studied,including division of solution region,conversion and discretisation of elliptic equation and the concrete steps of the grid generation in MATLAB.In the process of BFC grid generation, using Poisson equation with source phase as the transformation equation can make the orthogonality and density of the grid to get better controlled.Treating the boundary of the deadman as boundary condition can simplify the solving process of the mathematical model.The principles of the algorithm are simple and easy to program, as well as, the efficiency of generating grids is higher and the grids can satisfy the requirements of the mathematical model.%利用数学模型对高炉冶炼过程进行模拟是高炉炼铁新工艺研发的有效方法，网格生成技术是数值模拟过程中重要的前处理过程，是高炉模拟计算的先决条件。生成网格的质量对高炉模型模拟的精度、效率以及收敛性具有重要影响，因此，建立优质的网格对高炉数学模型的求解具有重要意义。文中提出了一种适用于高炉数学模型的适体坐标系（BFC ）网格的生成方法，从求解区域的划分、椭圆型方程的转换、椭圆型方程的离散及BFC网格生成步骤等方面进行了研究，并把死料区的边界作为BFC网格计算的边界条件，使数学模型的求解过程得以简化。采
Nanomechanical properties of multi-block copolymer microspheres for drug delivery applications.
Moshtagh, P R; Rauker, J; Sandker, M J; Zuiddam, M R; Dirne, F W A; Klijnstra, E; Duque, L; Steendam, R; Weinans, H; Zadpoor, A A
2014-06-01
Biodegradable polymeric microspheres are interesting drug delivery vehicles for site-specific sustained release of drugs used in treatment of osteoarthritis. We study the nano-mechanical properties of microspheres composed of hydrophilic multi-block copolymers, because the release profile of the microspheres may be dependent on the mechanical interactions between the host tissues and the microspheres that aim to incorporate between the cartilage surfaces. Three different sizes of monodisperse microspheres, namely 5, 15, and 30μm, were tested in both dry and hydrated (swollen) states. Atomic force microscopy was used for measuring nanoindentation-based force-displacement curves that were later used for calculating the Young׳s moduli using the Hertz׳s contact theory. For every microsphere size and condition, the measurements were repeated 400-500 times at different surface locations and the histograms of the Young׳s modulus were plotted. The mean Young׳s modulus of 5, 15, and 30μm microspheres were respectively 56.1±71.1 (mean±SD), 94.6±103.4, and 57.6±58.6MPa under dry conditions and 226.4±54.2, 334.5±128.7, and 342.5±136.8kPa in the swollen state. The histograms were not represented well by the average Young׳s modulus and showed three distinct peaks in the dry state and one distinct peak in the swollen state. The peaks under dry conditions are associated with the different parts of the co-polymeric material at the nano-scale. The measured mechanical properties of swollen microspheres are within the range of the nano-scale properties of cartilage, which could favor integration of the microspheres with the host tissue.
Grid-Connected Fuzzy-PID Control of PV Power Generation System%光伏发电系统的并网模糊PID控制
Institute of Scientific and Technical Information of China (English)
贺运胜
2013-01-01
在三相两级式并网逆变器数学模型的基础上,将模糊PID控制策略引入光伏发电系统的并网控制中.通过数字仿真和物理仿真表明模糊控制与PID控制相结合的模糊PID控制,改善了光伏系统并网控制的动态过程,能够实现光伏系统的平滑并网.%ied in the grid control of PV system in this paper. The digital simulation and physical simulation show that the fuzzy-PID control strategy can improve the PV system grid control dynamic process and realize the smooth connection of the PV system with the power grid.
Institute of Scientific and Technical Information of China (English)
孔令国; 蔡国伟; 杨德友; 孙正龙
2013-01-01
针对光伏并网发电系统具有随机性,且不具备故障暂态电压支撑能力的特征,提出一种有效调节功率且改善低电压穿越能力的光储联合并网发电系统动态模型及协调控制策略.在电力系统仿真分析平台DIgSILENT/Power Factory中建立了光储联合并网发电系统协调控制及低电压穿越功能模型.应用协调控制策略实现储能系统和静止同步补偿器功率平衡,维持并网点电压稳定.利用气象和负荷数据,验证了上述模型及协调控制策略的有效性.%In allusion to the randomness of grid-connected PV generation system that does not possess the ability to support fault-caused transient voltage, a dynamic model and corresponding coordinated control strategy for grid-connected PV generation system with energy storage devices that can effectively regulate power output and improve low-voltage ride through (LVRT) are proposed. A coordinated control model of grid-connected PV generation system with energy storage devices and an LVRT model are built on power system simulation analysis platform DIgSILENT/Power Factory. Using coordinated control strategy, the power balance between energy storage devices and static synchronous compensator (STATCOM) is implemented to make the voltage at grid-connected point stable. Availability of the proposed model and coordinated control strategy is verified by meteorological data and load data.
Institute of Scientific and Technical Information of China (English)
周磊; 袁晓玲; 徐杰彦
2015-01-01
This paper analyzes the surplus generation of dis⁃tributed photovoltaic feed⁃in grid considering demand⁃side manage⁃ment(DSM). By DSM, the consumer would modify electricity con⁃suming mode to increase surplus generation of photovoltaic feed in grid and decrease power supplying in electrical peak time. Con⁃structing response model of consumers is constructed based on con⁃sumer psychology. Genetic algorithm is used to calculate economic incentive of surplus generation feed⁃in grid considering adjustable photovoltaic capacity of consumers and constrains of power output of photovoltaic. The economic incentive makes the surplus genera⁃tion feed⁃in grid increased and the peak load in daytime decreased, which improves the efficiency of power system.%在居民用户分布式光伏发电余电上网方面引入需求侧管理，促进居民用户改变用电方式，提升日间余电上网电量，降低电网高峰时段的供电压力。基于消费者心理学原理，建立了用户激励响应模型。考虑用户可调容量、光伏出力的约束条件，采用多目标遗传算法得出分布式光伏发电余电上网的经济激励，该激励可有效提高用户余电上网电量，削减日间高峰负荷，提高电网的运行效率。
Energy Technology Data Exchange (ETDEWEB)
Nehrir, M. Hashem [Montana State Univ., Bozeman, MT (United States)
2016-10-20
investigated the following: • Intelligent load control - demand response (DR) - for frequency stabilization in islanded MGs (partially supported by PNNL). • The impact of high penetration of solar photovoltaic (PV)-generated power at the distribution level (partially supported by PNNL). • The application of AI approaches to renewable (wind, PV) power forecasting (proposed by the reviewers of our proposal). • Application of AI approaches and DR for real-time MG power management (partially supported by NEC Labs-America) • Application of DR in dealing with the variability of wind power • Real-time MG power management using DR and storage (partially supported by NEC Labs-America) • Application of DR in enhancing the performance of load-frequency controller • MAS-based whole-sale and retail power market design for smart grid A
Institute of Scientific and Technical Information of China (English)
杨帆; 贲进; 潘思宇; 达利春
2014-01-01
With the development of cloud computing , remote sensing , geographic information system , earth-observation , navigation , the discrete global multi-resolution grid model has been developed strongly and quickly .In view of the existing research results , this paper put forward a method to construct a new type of hexagonal discrete global grid , by selecting high performance hexagon as the basic grid unit , Fuller polyhedral projection as the projection type , and a new discrete global grid generation algorithm is systematically discussed and the corresponding experimental results are given .Besides, the paper pointed out its characteristics in comparison with the Snyder polyhedral projection based grid .%随着云计算、航天遥感、地理信息、导航等技术的发展，用于空间信息剖分组织的全球多分辨率离散格网模型得到了长足发展。针对已有研究成果和当前研究现状，选取性能优异的六边形作为基本格网单元，Fuller多面体投影作为投影类型，提出了一种基于正八面体构建新型六边形球面离散格网的方法。全文系统地论述了此新型离散格网的生成算法并给出了相应实验结果，最后与基于Snyder等积多面体投影的格网进行比较，得出其特点和应用前景。
A hybrid grid method in an auxiliary coordinate system for irregular fluid-solid interface modelling
Qu, Yingming; Huang, Jianping; Li, Zhenchun; Li, Jinli
2017-03-01
Seismic wave propagation in a fluid-solid environment cannot be simulated with a single wave equation, but can be described by use of the acoustic and viscoelastic wave equations for their respective fluid and solid parts. Proper boundary conditions at the fluid-solid interface based on the relationship between pressure and stress are crucial when combining the two different wave equations. Traditional finite difference methods have had difficulties in dealing with the irregular fluid-solid interface topography. The Cartesian grids discretization leads to artificial reflections and diffractions during the conversion between acoustic wave and elastic waves. We propose a variable coordinate transformation methodology to simulate seismic waves in a fluid-solid environment. An irregular fluid-solid interface can be transformed into a horizontal interface, so that pressure and stress can be well converted. We also introduce a multiblock coordinate transformation (MCT) method which meshes each layer with curvilinear grids to transform the interface topography into a horizontal one, thereby allocating vertical sampling points adaptively. The grid size is determined adaptively based on the shape and the parameters of the target area, which reduces in size in when the layers are thin or exhibit low velocities. A Lebedev-standard staggered grid scheme is applied to the MCT method to reduce both the computational cost associated with the Lebedev grid scheme and the instability in the auxiliary coordinate system when using a standard staggered grid scheme.