A numerical method for the simulation of compressible turbulent flows is presented. This method includes a novel hybrid grid generation for airfoil cascades and an unstructured mesh flow solver. The mesh tool incorporates a mapping technique and a grid smoothing method. The mapping technique is used to build an initial volume mesh and the grid smoothing method is used to improve the quality of the initial mesh. The grid smoothing is based on the optimization of mesh-quality parameters. The further improvement of the smoothed mesh is achieved by an edge-swapping and node-insertion technique. The unstructured flow solver is developed for a hybrid grid. This flow solver uses a rotational frame of reference. The convective and viscous fluxes are numerically solved by an upwind scheme and an averaged nodal gradient. A higher-order spatial accuracy is achieved by a piece-wise linear reconstruction. An explicit multi-stage method is employed for integration in time. The Menter’s k −τ model is implemented to simulate the turbulence effects. The flow solver is validated against the analytical and experimental results. A parametric study is performed for a high speed centrifugal compressor.

Recent enthusiasm in grid computing has resulted in a tremendous amount of research in resource scheduling techniques for tasks in a (scientific) workflow. There are many factors that may affect the scheduling results, one of which is whether the application is computing-intensive or data-intensive. Most of the grid scheduling researches focus on a single aspect of the environments. In this thesis, we base on our previous work, a probability-based framework for dynamic resource scheduling, and consider data transmission overhead in our scheduling algorithms. The goal is to dynamically assign resources to tasks so as to maximize the probability of completing the entire workflow within a desired total response time. We propose two algorithms for the dynamic resource scheduling in grid environment, namely largest deadline completion probability (LDCP) and smallest deadline completion probability (SDCP). Furthermore, considering the data transmission overhead, we propose a suite of push-based scheduling algorithms, which schedule all the immediate descendant tasks when a task is completed. These are algorithms will be compared to the pull-demand scheduling algorithms in our previous work and workflow-based algorithms proposed by other researchers. We use GridSim toolkit to model the grid environment and evaluate the performance of the various scheduling algorithms.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 142-156). Available also in a digital version from Dissertation Abstracts.

No description available.

As an increasing number of distributed power generation systems (DPGS) are being connected to the utility grid, there is a growing requirement for the DPGS to be able to ride through short grid disturbances. This requires improvements to be made to the grid-side control scheme of the DPGS. An important part of the grid-side control scheme is the grid synchronization method, which is responsible for tracking the phase angle of the grid voltage vector. The state-of-the-art grid synchronization methods being used today are phase-locked loops. This thesis presents a modified phase-locked loop which is more robust towards grid disturbances. It consists of a multi-block adaptive notch filter (ANF) integrated into a conventional three-phase synchronous reference frame phase-locked loop (SRF-PLL). The addition of the multi-block ANF to the system allows it to become frequency adaptive. Also, since the multi-block ANF consists of multiple ANF blocks in parallel with one another, the system is able to remove multiple input signal distortions. Thus, the proposed system is able to eliminate the double frequency ripple that is caused in the conventional three-phase SRF-PLL by input unbalance, as well as harmonic errors, despite the presence of frequency variations in the input signal. Simulation results found using Matlab/Simulink, and experimental results found using the dSPACE DS1103 DSP board, demonstrate the feasibility of the modified SRF-PLL. Also, the modified SRF-PLL is compared to a conventional three-phase SRF-PLL, as well as to a conventional three-phase SRF-PLL with a simple notch filter, and the advantages of the modified SRF-PLL are discussed. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2008-12-17 12:38:02.589

Environmentally friendly renewable energy technologies such as wind and solar energy systems are among the fleet of new generating technologies driving the demand for distributed generation of electricity. Power Electronics has initiated the next tech¬nological revolution and enables the connection of distributed generation (DG) systems to the grid. The challenge is to achieve system functionality without extensive custom engineering, yet still have high system reliability and generation placement flexibility. Nowadays, it is a general trend to increase the electricity production using DG systems. If these systems are not properly controlled, their connection to the utility network can generate problems on the grid side. Therefore, considerations about power generation, safe running and grid synchronization must be done before connecting these systems to the utility network. This thesis introduces a new grid-synchronization, or more visibly a new “power signal processor” adaptive notch filtering (ANF) tool that can potentially stimulate much interest in the field and provide improvement solutions for grid-connected operation of DG systems. The processor is simple and offers high degree of immunity and insensitivity to power system disturbances, harmonics and other types of pollutions that exist in the grid signal. The processor is capable of decomposing three-phase quantities into symmetrical components, extracting harmonics, tracking the frequency variations, and providing means for voltage regulation and reactive power control. In addition, this simple and powerful synchronization tool will simplify the control issues currently challenging the integration of distributed energy technologies onto the electricity grid. All converter-interfaced equipments like FACTS (flexible ac transmission systems) and Custom Power Controllers will benefit from this technique. The theoretical analysis is presented, and simulation and experimental results confirm the validity of the analytical work. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2009-01-27 11:37:07.279

Due to recent concerns regarding energy conservation and dependence on fossil fuels, the efficient integration of electric vehicle populations’ in the future smart grid has become a significant area of research. Despite the heavy penetration of smart meters throughout North America and Europe a lack of research exists utilizing real consumption data. Making use of smart meter data, a model of a prototypical residential feeder was created to observe the effects of increased electric vehicle penetration on the selected feeder. Simulations of the current operation of the feeder were performed along with modeled uncoordinated, coordinated, and coordinated vehicle to grid charging of electric vehicles. As expected, it was found that the normal operation of the feeder is subject to several inefficiencies which are made worse by uncoordinated charging of electric vehicles. Significant improvements in the considered operational parameters were found as a result of the coordinated charging of vehicles using a quadratic programming based control algorithm. Further it was found, that the use of coordinated vehicle to grid connections only produces marginal benefits over standard connections. Leading to the conclusion that development of charging controls is more significant to the mitigation of electric vehicle charging effects than the integration of vehicle to grid connections. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2014-01-31 16:02:37.201

No description available.

Nearly every aspect of modern life today, from businesses, transportation, and healthcare, depends on the power grid operating safely and reliably. While the recent push for a “Smart Grid” has shown promise for increased efficiency, security has often been an afterthought, leaving this critical infrastructure vulnerable to a variety of cyber attacks. For instance, devices crucial to the safe operation of the power grid are left in remote substations with their configuration interfaces completely open, providing a vector for outsiders as well as insiders to launch an attack. This paper develops the framework for an overlay network of gateway devices that provide authenticated access control and security monitoring for these vulnerable interfaces. We develop a working prototype of such a device and simulate the performance of deployment throughout a substation. Our results suggest that such a system can be deployed with negligible impact on normal operations, while providing important security mechanisms. By doing so, we demonstrate that our proposal is a practical and efficient solution for retro-fitting security onto crucial power system devices.

The basis of a novel bipolar transistor structure was proposed by Dr R. Aubusson of Middlesex Polytechnic in 1977. The novelty lies in replacing the conventional overlay transistor's P+ base grid with a refractory metal grid, in order (a) to lower the base resistance and (b) to autoregister the emitter. It was claimed that the linearity of the transistor would also be improved. A number of questions raised by this idea have been investigated, the methods and conclusions of which are presented here. Plausible structures, using the metal base grid, are proposed and compared with conventional structures. Some advantages are seen to be possible. The current understanding of distortion analysis applied to transistors is reviewed. The main ideas are presented in a unified manner and are extended to higher order. A number of the transistor's second order effects are analysed in a novel fashion. The metal base grid transistor is analysed and compared with conventional transistors, with favourable results. Practical aspects of fabricating the metal base grid transistor were investigated. A procedure for deposition has been determined and is presented here along with the film physical and electrical characteristics. Analysis of the tungsten-silicon interface shows the suitability of the metallization as a base grid. Suitable means of delineating the tungsten film have been assessed and a working procedure determined. Subsequent deposition of various insulators has been investigated and the problems associated with the readily oxidized tungsten film have been overcome. Formation of the emitter, requiring further high temperature processing, has been assessed in view of the limitations imposed by the preformed base metallization. In summary, it has been shown that the novel structure can be constructed and that significant performance improvement is to be expected, although a full realization was not possible within the resource constraints of the project.