The electric grid of Gotland is connected to the mainland via a 90 km HVDC Classic bipole of 2 * 130 MW. The HVDC link balances the load and production on the island to maintain the frequency within limits, the load varies between 50 and 180 MW throughout the year. The power production on the island comes mainly from wind power. Today, the installed power is about 170 MW but the wind power production will be further exploited and the plan is to add another 500 MW of wind power capacity to the existing plants. These plants will be connected to a new 130 kV transmission grid which will have a connection to the existing 70 kV grid at a new substation called Stenkumla. Along with the increased wind power production on the island comes the need of increased transmission capacity to the mainland. A VSC HVDC link of 500 MW is planned for this purpose and it will be connected to Stenkumla. As of today, it is not certain whether the two grids will be connected or not. Having connected grids is in the interest of the grid owner Gotlands Energi AB, GEAB since they then could utilize the technology of the new link and thereby ensure stableoperation during faults that today would lead to black out. In this thesis the feasibility of having connected grids was investigated and the study was divided into three main parts. •Reactive power and voltage profiles •Short circuit study •Converter trip study This study shows that under the assumptions made regarding production grid layout and proportion of WTG types there will be no need for adding reactive power compensation equipment. That is provided that demands are set on wind power plant contractors to have their equipment contributing with reactive power compensation, even during no load. A trip of the SvK VSC HVDC converter during full power production causes the most severe stress to the system. The major problem proved to be surviving the first 100 ms after converter trip without loosing angular stability and the most important measure to improve the stability was active power reduction of the wind turbines. The overall conclusion is that it is feasible to have connected grids during normal operation but demands has to be put on wind power plant contractors.

Las aplicaciones paralelas presentan diversos problemas de prestaciones al ser cambiadas para ejecutar en entornos Grid. Las características del sistema pueden ser diferentes en cada ejecución y en algunos casos dentro de una misma ejecución. Los recursos remotos comparten enlaces de red y, los procesos de la aplicación comparten las maquinas con otros procesos. En esos escenarios se propone el uso de la técnica de sintonización dinámica de prestaciones para ayudar las aplicaciones a adaptarse a los cambios en las características del sistema con la intención de resolver los problemas de prestaciones. Esta tesis analiza el problema de la ejecución de aplicaciones paralelas en entornos Grid, herramientas para el análisis de prestaciones disponibles y modelos adecuados para la sintonización dinámica de aplicaciones paralelas en este tipo de entorno. De este análisis, se propone una arquitectura para sintonización dinámica de aplicaciones paralelas en entornos Grid llamada GMATE. Esta arquitectura incluye diversas contribuciones. En el caso donde un gestor de recursos de alto nivel decide el mapeo de procesos de la aplicación, se proponen dos aproximaciones para el seguimiento de procesos que habilita GMATE a localizar donde las capas de software del Grid ha mapeado los procesos de la aplicación. Una aproximación consiste en la integración de GMATE a las capas de software del Grid. La otra integra los componentes requeridos de GMATE dentro de los binarios de la aplicación. El primer enfoque requiere derechos de administración en cuanto que el segundo incrementa el binario del la aplicación, lo que torna más lento el arranque de la misma. Para respetar las políticas de las organizaciones propietarias de los recursos, todas las comunicaciones usan el mismo certificado de seguridad de la aplicación. Esas comunicaciones son hechas con base en las capas del Grid. Esta aproximación habilita la arquitectura a monitorizar y sintonizar los procesos de la aplicación de forma dinámica a las restricciones de cortafuegos de las organizaciones y políticas de uso de la red en las mismas. Para bajar la necesidad de comunicaciones en la arquitectura GMATE, se encapsula parte de la lógica requerida para colectar las medidas y para cambiar los parámetros de la aplicación en componentes encuestados que ejecutan dentro de espacio de memoria del proceso de la aplicación. Para colectar medidas, se ha creado componentes sensores que disminuyen la necesidad de comunicaciones llevando el procesamiento de eventos para dentro del proceso de la aplicación. Diferente de la instrumentación tradicional, los sensores pueden retrasar la transmisión de los eventos y ejecutar operaciones básicas como sumas, temporizadores, promedios o generación de eventos basados en umbrales. Esas capacidades reducen los requerimientos de comunicaciones que son útiles en situaciones de bajo ancho de banda. Se propone también el encapsulamiento de la lógica de cambio en las aplicaciones en componentes actuadores. Los actuadores son instalados en el flujo de ejecución de la aplicación y posibilita la sincronización y baja intrusión en cambio de variables y ejecución de funciones para modificar la aplicación. La arquitectura propuesta posibilita la comunicación entre sensores y actuadores lo cual habilita la sintonizaciones sencillas sin necesidad de comunicaciones. Para aplicar la sintonización dinámica en entornos Grid, necesitamos de un modelo de prestaciones que pueda ser usado en entornos con heterogeneidad de red y procesadores para guiar el proceso. Se propone un modelo de prestaciones basado en una heurística para lograr usar el máximo número de esclavos y el mejor tamaño de grano en una ejecución Maestro-Esclavo en sistemas Grid. Se considera que una clase de aplicaciones pueden ser desarrolladas con la capacidad de cambiar el tamaño de grano en tiempo de ejecución y que esa acción cambia la relación entre cómputo y comunicación. En el escenario donde usuarios reciben un conjunto de recursos para una ejecución paralela, esos recursos pueden configurar un sistema de múltiples clústeres. La heurística del modelo presentado permite guiar la selección de los recursos para disminuir el tiempo total de ejecución de la aplicación. Se intenta buscar el punto donde el maestro usa el máximo número de esclavos posible asignando prioridad a aquellos más rápidos. Se presentan los resultados de sintonización del tamaño de grano y número de esclavos en ejecuciones Maestro-Esclavo en entornos Grid donde se logra bajar el tiempo total de ejecución de la aplicación y aumentando la eficiencia de uso de los recursos. Se presentan las implementaciones de las aplicaciones multiplicación de matrices, N-Body y cargas sintéticas las cuales tienen diferentes grados en la relación entre cómputo y comunicación en escenarios de cambio del tamaño de grano. / When moving to Grid Computing, parallel applications face several performance problems. The system characteristics are different in each execution and sometimes within the same execution. Remote resources share network links and in some cases, the processes share machines using per-core allocation. In such scenarios we propose to use automatic performance tuning techniques to help an application adapt itself thus a system changes in order to overcome performance bottlenecks. This thesis analyzes such problems of parallel application execution in Computational Grids, available tools for performance analysis and models to suit automatic dynamic tuning in such environments. From such an analysis, we propose system architecture for automatic dynamic tuning of parallel applications on computational Grids named GMATE. Its architecture includes several contributions. In cases where a Grid meta-scheduler decides application mapping, we propose two process tracking approaches that enable GMATE to locate where a Grid middleware maps application processes. One approach consists of the integration of GMATE components as Grid middleware. The other involves the need to embed a GMATE component inside application binaries. The first requires site administration privileges while the other increases the application binary which slows down application startup. To obey organizational policies, all communications use the same application security certificates for authentication. The same communications are performed using Grid middleware API. That approach enables the monitoring and tuning process to adapt dynamically to organizational firewall restrictions and network usage policies. To lower the communication needs of GMATE, we encapsulate part of the logic required to collect measurements and change application parameters in components that run inside the processing space. For measurements collection, we create sensor components that reduce the communication needs by event processing inside the process space. Different from traditional instrumentation, sensors can postpone the event transmission and perform basic operations such as summarizations, timers, averages or threshold based event generation. That reduces the communication requirements in cases where network bandwidth is expensive. We also encapsulate the modifications used to tune the application in components called actuators. Actuators may be installed at some point in the program flow execution and provide synchronization and low overhead control of application variables and function executions. As sensors and actuators can communicate with each other, we can perform simple tuning within process executions without the need for communication. As the dynamic tuning is performance model-centric, we need a performance model that can be used on heterogeneous processors and network such Grid Systems. We propose a heuristic performance model to find the maximum number of workers and best grain size of a Master-Worker execution in such systems. We assume that some classes of application may be built capable of changing grain size at runtime and that change action can modify an application's compute-communication ratio. When users request a set of resources for a parallel execution, they may receive a multi-cluster configuration. The heuristic model allows for shrinking the set of resources without decreasing the application execution time. The idea is to reach the maximum number of workers the master can use, giving high priority to the faster ones. We presented the results of the dynamic tuning of grain size and the number of workers in Master-Worker applications on Grid systems, lowering the total application execution time while raising system efficiency. We used the implementation of Matrix-Multiplication, N-Body and synthetic workloads to try out different compute-communication ratio changes in different grain size selections.

This thesis investigates the use of an operational formal architectural strategy to reinvigorate instances of failing city fabric. By introducing hierarchy and nodal destination elements into the urban grid, the existing field is transformed into a network of catalytic centers. Frame is employed as a permeable mediator between the existing grid and insertion, creating a permeable superblock that is both contextual and stimulating. The Over-the-Rhine district in Cincinnati, Ohio, is one of these failing city fabrics. Directly adjacent to downtown, this once vibrant neighborhood has experienced massive depopulation and deterioration. It’s population has dropped from 45,000 to less than 5,000. Currently, 66% of the buildings in the area are vacant or have been demolished. Over-The-Rhine lies between downtown and the University of Cincinnati. There is potential in creating a growth corridor between these two poles through Over-The-Rhine, stimulating the stagnant grid. A nodal infrastructural transit corridor is inserted between Downtown and the University of Cincinnati. Stops along the corridor act as point insertions in the fabric, forming nodal hierarchy. Incision activates the existing context through connection, deploying both a top down and bottom up approach. It creates a large centralized entity framed by and connected to context. It creates a range of scales, allowing for programmatic variety, an urban characteristic that the enclave lacks. It is strategic in working with the fabric, mediating flows and taking advantage of the porous grid condition. Each incision, in order to successfully attract from both downtown and the university, contains programmatic elements from each pole. This integration creates a complex interaction of program, as well as new partnerships between Downtown and University entities. It is a new approach for both Downtown and the University to address the failing fabric between.

Although modern society is critically reliant on power grids, even modern power grids are subject to unavoidable outages due to storms, lightning strikes, and equipment failures. The situation in developing countries is even worse, with frequent load shedding lasting several hours a day due to unreliable generation. We study the use of battery storage to allow a set of homes in a single residential neighbour- hood to avoid power outages. Due to the high cost of storage, our goal is to choose the smallest battery size such that, with high target probability, there is no loss of power despite a grid out- age. Recognizing that the most common approach today for mitigating outages is to use a diesel generator (genset), we study the related problem of minimizing the carbon footprint of genset operation. Drawing on recent results, we model both problems as buffer sizing problems that can be ad- dressed using stochastic network calculus. We show that this approach greatly improves battery sizing in contrast to prior approaches. Specifically, a numerical study shows that, for a neigh- bourhood of 100 homes, our approach computes a battery size, which is less than 10% more than the minimum possible size necessary to satisfy a one day in ten years loss probability (2.7 ∗ 10^4 ). Moreover, we are able to estimate the carbon footprint reduction, compared to an exact numerical analysis, within a factor of 1.7. We also study the genset scheduling problem when the rate of genset fuel consumption is given by an affine function instead of a linear function of the current power. We give alternate scheduling, an online scheduling strategy that has a competitive ratio of (k1 G/C +k2)/(k1+k2) , where G is the genset capacity, C is the battery charging rate, and k1, k2 are the affine function constants. Numerically, we show that for a real industrial load alternate scheduling is very close to the offline optimal strategy.

The development of future smart electricity grids is driven by efficiency and climate targets and economic benefit for producers, retailers and customers on the deregulated electricity market. Since most investments will be made by grid owners acting as regulated monopolies, it is unclear how they will get return on their investments. Can demand response programs create cost reductions for the grid owner that help motivate the investment in smart grids? Two cases of cost reduction opportunities are evaluated assuming that peak loads are reduced by a demand response program: optimization of cable dimensions for lower peak loads when building new grids, and avoided investments in reinforced capacity in the existing grid. Potential cost reductions are estimated for the two example cases, using financial and technical data for Fortum's local distribution grid in Stockholm. The result shows that reducing the capacity in the cables by 70-80 % only brings down investment costs by 3-4 %, since the common expense for excavation outweighs the incremental cost of cables. Over-capacity means increased redundancy and flexibility to increase load in the future, which are valuable features for a grid owner.Regarding investments in the existing grid, a substation that needs replacement because of overload is analyzed. Assuming a continued trend of steadily increasing load, a 34 % peak load reduction would delay the investment 20 years, which is in turn worth 900,000 SEK in 2010 prices.

This master thesis was provided by ABB Cooperate Research in Västerås. This study has two major purposes: (1) to identify the characteristics of a flywheel energy storage system (FESS), (2) take the first steps in the development of a simulation model of a FESS. For the first part of this master thesis a literature reviews was conducted with focus on energy storage technologies in general and FESS in particular. The model was developed in the simulation environment PSCAD/EMTDC; with the main purpose to provide working model for future studies of the electrical dynamics of a flywheel energy storage system. The main conclusion of the literature review was that FESS is a promising energy storage solution; up to multiple megawatt scale. However, few large scale installations have so far been built and it is not a mature technology. Therefore further research and development is needed in multiple areas, including high strength composite materials, magnetic bearings and electrical machines. The model was implemented with the necessary control system and tested in a simulation case showing the operational characteristics.

Renewable power sources with a relatively uneven or constant DC power production require synchronization methods to work with the current utility power grid. The solution to this synchronization problem has been solved with semiconductor based converters and advanced switching algorithms. To enable switching algorithms that work well with the grids amplitude, phase-shift and frequency, the current waveform has to be measured and estimated.    There are many sources of noise that will add distortion of the current waveform, making its appearance less similar to the grids. The distorted measurement affects the accuracy of the converters negatively. Therefore, using a filter algorithm to attenuate the grid noise is required.  This project uses a Kalman filter with the aim to decrease the noise and estimate the current phase shift for a three phase power-grid.  To achieve reliable and fast calculation, implementing the Kalman filter within a FPGA were done.The project contains results from both simulated MATLAB data and the FPGAs real time data. The method was able to estimate the grid within a few Hz frequency deviation and enable some noise reduction. For larger degree of harmonic distortion during steady state operation, the Kalman filter could remove more of the harmonic distortion. Limits and differences with MATLAB are discussed for the FPGA implemented Kalman filter.

With the world suffering from energy crisis, Smart Grid is the expanding research topic that deals vigorously with the current problems. It promotes decentralized renewable energy generation system, participate many local energy producers to energy market, adds vehicle to grid (V2G), minimize the energy loss in the electrical system, and participate many active consumers to the real market. It is an emerging project that needs an expert from many fields, thus it opens door of opportunities for many people around the globe. The present thesis deals with the communication scenario in smart grid. Communication is the backbone of Smart Grid and the thesis tries to highlight the available communication technologies for smart grid application. The thesis discuss most profitable communication technologies used for this purpose which are power line communication and wireless communication, in which power line communication aspects and characteristics are covered more than wireless communication for its use are seen more in upcoming days. In all the thesis will outline the opportunities and challenges of power line communication and wireless communication for smart grid application.

In the ATLAS experiment software plays a central role in data taking, reconstruction, and analysis. This thesis presents a set of analysis algorithms written for the ATLAS software framework Athena, towards H+ searches in the τ+jets channel. Data recorded by the ATLAS experiment for 900 GeV proton-proton collisions from 2009 and 7 TeV proton-proton collisions from 2010 are analyzed with these algorithms and compared to Monte Carlo. A search for top quarks is performed on 36 pb-1 of data, and the results are found to agree well with Monte Carlo.

Since 2002, the department of electricity at Uppsala university has pushed the Lysekil project. The project has a number of wave energy converters installed in the sea southwest of Lysekil. The purpose of this work is to design, build and test a DC-DC converter, which will later be used as a necessary part of the grid connection of a wave energy converter. Since a wave energy converter does not generate electricity at a constant frequency, it is not possible to use a gearbox. Instead, power is rectified and, if there are several wave power energy converters, are put together with the others before it is inverted and transformed to the correct voltage level, and finally connected to the grid [1]. The designed DC-DC converter is a converter of the type "inverting buck-boost", i.e. a converter that can both lower and raise the voltage, and inverts the polarity of the output. Although the voltage in normal circumstances will only be increased, the simulations showed that the efficiency and cost of components did not differ much between a "boost" and "buck-boost" converter, thus considered flexibility to be able to lower the voltage if needed. The project also includes a small part to the construction of a bridge rectifier, but as the most difficult moment in the project is the DC-DC converter, the greatest focus will be there.