<p>Until just a few years ago wind farms where excluded from many of the requirementsthat can be found in grid codes. But as the numbers of wind farms have grown as wellas the sizes of them, the requirements to connect them to the grid have becomemore stringent. In this thesis it has been investigated if it’s possible to design a controlsystem that controls the reactive power from an offshore wind farm, so that the gridcode requirements regarding reactive power are fulfilled. By controlling the reactivepower the dynamic variations in the voltage are decreased. The regulator should alsobe able to help the wind farm to handle the fault conditions that are described in thegrid code.An offshore wind farm outside the coast of Western Europe is now being planned.Data from this wind farm has been used in this thesis. The wind farm has a total of 54wind turbines with more than 300 MW all together. The reactive power is controlledvia the generators and also by disconnecting and connecting four shunt reactors.A model of the wind farm has been built in Simpow, as well as design of the regulator.Simpow is a simulation program developed by ABB that enables simulations of powersystems. Different scenarios have been simulated to see if it is possible to control thewind farm in the desired way. The results show that the wind farm manages to handlefault conditions as described in the grid, and it is also possible to control the reactivepower in a desirable way.</p>

Until just a few years ago wind farms where excluded from many of the requirementsthat can be found in grid codes. But as the numbers of wind farms have grown as wellas the sizes of them, the requirements to connect them to the grid have becomemore stringent. In this thesis it has been investigated if it’s possible to design a controlsystem that controls the reactive power from an offshore wind farm, so that the gridcode requirements regarding reactive power are fulfilled. By controlling the reactivepower the dynamic variations in the voltage are decreased. The regulator should alsobe able to help the wind farm to handle the fault conditions that are described in thegrid code.An offshore wind farm outside the coast of Western Europe is now being planned.Data from this wind farm has been used in this thesis. The wind farm has a total of 54wind turbines with more than 300 MW all together. The reactive power is controlledvia the generators and also by disconnecting and connecting four shunt reactors.A model of the wind farm has been built in Simpow, as well as design of the regulator.Simpow is a simulation program developed by ABB that enables simulations of powersystems. Different scenarios have been simulated to see if it is possible to control thewind farm in the desired way. The results show that the wind farm manages to handlefault conditions as described in the grid, and it is also possible to control the reactivepower in a desirable way.

The construction of traditional large-scale central power plants and the extension of power lines in Taiwan have tremendous difficulties in terms of land acquisition and environmental protection for a long time. In addition, one potential risk of energy supply is that over 95% of energy source is imported overseas. Therefore, the most important goal of Taiwan energy policy is to cut down the amount of energy import. To achieve the goal, it is important to explore innovatively local energy source by developing renewable and clean energy. Around the available renewable energy technologies, wind power technique is the most mature one in addition to hydraulic power generation. However due to limited land resources and restrictive regulations, it is expected that wind farm development in Taiwan can only be located offshore, instead of inland. Besides, a multi-functional wind farm site, which involves ocean farm ranch, is desirable to bring mutual benefits for both developers and local stake holders. The current study has used System Dynamics(SD) to analyze the influence of Multi-functional offshore wind farm on economic. We discuss the change of fish catch with building offshore wind farm¡Aand the change of economic output in open ocean with offshore wind farm combine marine ranching. It is therefore easy for the decision makers to comprehend the economical benefit difference if an offshore multi-functional wind farm were to develop in the future. The result of this study is building offshore wind farm will reduced the fishing revenue in a short time¡Abut the total fishing revenue will increased in a long time. The Multi-functional offshore wind farm has better economic output than offshore wind farm.

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ABSTRACT Wind energy is among the fastest growing renewable energy technologies in the world that has been increasing by about 30% a year globally. Wind energy has proven to be a clean, abundant and completely renewable source of energy. Owing to the rapidly increasing use of wind power, the aspect of integrating high level of penetrations wind power into the grid is becoming more and more of reality. Examples of large wind farms in the United States are the 781.5 MW Roscoe wind farm in Texas, the 735.5 MW Horse Hollow Wind Energy Center in Taylor and Nolan County, Texas, the 845 MW Shepherds Flat wind farm in Oregon and the 1550 MW Alta wind farm being developed in California. As most large wind farms in North America employ Doubly-fed Induction Generator (DFIG) wind turbines, their voltage-sourced converter-based back-to-backs offer independent control of the real and reactive power. The use of these control capabilities have been recently proposed for damping power swings, inter-area oscillations as well as subsynchronous resonance. There is, however, a question that is always associated with the use of voltage-sourced converter -based back-to-back wind farms for damping power system oscillations: what happens when there is no wind? The keyword to the answer is “combined”. The potential benefit of using these types of wind farms for damping power system oscillations should always be combined with conventional damping devices (power system stabilizers, thyristor controlled series capacitor, static synchronous series compensator, high voltage dc systems, etc.). This thesis reports the results of digital time-domain simulation studies that are carried out to investigate the potential use of supplemental controls of DFIG-based wind farms combined with a phase imbalanced hybrid series capacitive compensation scheme for damping power system oscillations. The thesis also addresses the recent concern over the case of large share of wind power generation which results in reducing the total inertia of the synchronous generators and degrading the system transient stability. In this regards, the results of the investigations have shown that in such a case; properly designed supplemental controllers for the wind farm converters could be an asset in improving the system transient stability rather than degrading it. Time-domain simulations are conducted on a benchmark model using the ElectroMagnetic Transients program (EMTP-RV).

Technical Due Diligence (TDD) is an extensive document review process in which a complete assessment is made of all potential risks to the realisation or successful operation of a wind farm project. The goal of this assessment is to determine thecommercial feasibility of the proposed project. TDD assessments are extensive undertakings, and potentially subject to the bias of the individual reviewer. This aim of this research project is to develop a methodology to assist in the completion of TDD reviews at the host company for this research project, Mecal Wind Farm Services B.V., which will reduce the subjectivity of the TDD analysis and allow for objective comparison between different projects. A methodology was developed which assists the TDD assessment process. This methodology uses the combined judgements of individual reviewer and project managerto apply a weighting to the risk assessments carried out as part of the review. Aspreadsheet tool was created, based on this methodology, to assist the completion ofTDD assessments at Mecal.The spread sheet tool was validated by reference to historic project data at Mecal. The output of the tool compared well with the outcome of the project, proving that theconcept and methodology of the tool is sound.

Optimization of wind farm layout is an expensive and complex task involving several engineering challenges. The layout of any wind farm directly impacts profitability and return of investment. Several software optimization modules in line with wind farm design tools in industry is currently attempting to place the turbines in locations with good wind resources while adhering to the constraints of a defined objective function. Assessment of these software tools needs to be performed clearly for assessing different tools in wind farm layout design process. However, there is still not a clear demonstration of benchmarking and comparison of these software tools even for simple test cases. This work compares two different optimization software namely openWind and WindPRO commercial software tools mutually.

abstract: Wind measurements are fundamental inputs for the evaluation of potential energy yield and performance of wind farms. Three-dimensional scanning coherent Doppler lidar (CDL) may provide a new basis for wind farm site selection, design, and control. In this research, CDL measurements obtained from multiple wind energy developments are analyzed and a novel wind farm control approach has been modeled. The possibility of using lidar measurements to more fully characterize the wind field is discussed, specifically, terrain effects, spatial variation of winds, power density, and the effect of shear at different layers within the rotor swept area. Various vector retrieval methods have been applied to the lidar data, and results are presented on an elevated terrain-following surface at hub height. The vector retrieval estimates are compared with tower measurements, after interpolation to the appropriate level. CDL data is used to estimate the spatial power density at hub height. Since CDL can measure winds at different vertical levels, an approach for estimating wind power density over the wind turbine rotor-swept area is explored. Sample optimized layouts of wind farm using lidar data and global optimization algorithms, accounting for wake interaction effects, have been explored. An approach to evaluate spatial wind speed and direction estimates from a standard nested Coupled Ocean and Atmosphere Mesoscale Prediction System (COAMPS) model and CDL is presented. The magnitude of spatial difference between observations and simulation for wind energy assessment is researched. Diurnal effects and ramp events as estimated by CDL and COAMPS were inter-compared. Novel wind farm control based on incoming winds and direction input from CDL's is developed. Both yaw and pitch control using scanning CDL for efficient wind farm control is analyzed. The wind farm control optimizes power production and reduces loads on wind turbines for various lidar wind speed and direction inputs, accounting for wind farm wake losses and wind speed evolution. Several wind farm control configurations were developed, for enhanced integrability into the electrical grid. Finally, the value proposition of CDL for a wind farm development, based on uncertainty reduction and return of investment is analyzed. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2013

Climate Change and Energy Security have been dominating the global energy agenda. In response the United Kingdom (UK) set a target of reducing emissions by 80% by 2050, and have accepted the European Directive to produce 15% of energy by renewable resources by 2020. Despite doubts in the last few years, the UK are on track to not only meet but exceed the target placed upon them, which sets them in good light for the long term 2050 emission reduction. This research investigated the barriers in the industry such as the planning process delays and public perception. Findings suggested that negative public perceptions still remain, with onshore projects gaining more attention than offshore projects. The planning system whilst showing an improvement in overall decision time still showed signs of delays in the pre-examination process. The research also highlighted signs of a predicted development plateau in onshore schemes, with approved capacity rates slowing in the year 2014. Furthermore, the political structure surrounding wind energy has become fragile, following recent comments from the Conservative party, suggesting they will see an end to onshore wind should they gain election in 2015. Therefore despite positive steps taken by the UK towards renewable energy targets, the future of wind energy is not certain.

The threatening impacts of climate change are driving a global revolution towards cleaner sources of energy. In South Africa, strategies for energy security and emissions reduction are focusing on renewables, wind energy being one of the most promising ones. The construction of wind energy projects has attached limitations in the identification of suitable areas that respect the environment and are technically feasible. Herein, site selection criteria has been grouped into the Site Identification group (SIG), and the Resource & Energy Generation group (R&E). The SIG incorporates technical, environmental and restricted criteria within a spatial frame; while R&E accounts for the wind resource, estimated energy generation and fitting to energy demand profiles under a spatial-temporal frame. The average wind resource is usually found to be analysed together within the technical factors to determine the feasibility of a site; however for this study, a different and independent treatment of the wind resource and its energy generation profile was undertaken. It consists of evaluating the unique hourly wind power profile of each site against the energy consumption profile for the same period. The need is for selecting places with the smallest variation between the electricity produced and the electricity demanded. The Production to Demand Difference (PDD) has been chosen as the indicator of such variations. Therefore, the new purpose is to identify spots where the combination of the PDD and the results from the SIG become smaller with time. The Mean Difference (MD) is also taken into account to obtain further information regarding the trends of the differences. Geoprocessing, overlays and mathematical combinations of datasets are all performed under a GIS environment. / Dissertation (MEng)--University of Pretoria, 2015. / tm2015 / Chemical Engineering / MEng / Unrestricted