System specifications and testing model for increasing the rated power output, rotor diameter, hub height, and maximum tip speed of horizontal axis wind turbines is designed and implemented on the system advisor model simulator. Its performance is tested on offshore wind turbine’s direct-drive and single stage-low speed generators. Although this simulator produces impressive results, it has some limitations in the operation of wind turbines. The terrain and topography of wind turbines are not considered in the simulation process. It also does not assess the electrical transients and physical stress of wind turbine components. Despite its limitations, four large offshore wind turbines and wind farms have been successfully simulated. It is found that the 9 MW, 10 MW, 11 MW and their respective wind farms generate more energy and better capacity factor on the direct-drive than single stage-low speed generator. Furthermore, a rectangular layout of 20 wind turbines considerably impacted the excellent performance of this generator on the wind farms. Another notable outcome of the study is that higher system specifications do not always generate feasible results for wind turbines despite favourable weather conditions. For the Vestas 8 MW wind turbine, the viable percentages for increasing the size of its rated power output, rotor diameter, hub height and maximum tip speed is only 12.5%, 25% and 37.5%. The viability of these three upgrades has been confirmed by suitable graphs of power curves and feasible energy production results. Thus, these percentages confirm an 8 MW wind turbine’s attainable design limits for generating realistic energy production and capacity factor. On the contrary, a 50% increase in the above four system specifications yielded unviable capacity factor and energy production results. This is because this upgrade is too high to work successfully on the current wind turbine technology. Furthermore, the shape of the power curve from the 50% specifications is not the typical curve for wind turbines. It has been observed that increasing the value of maximum tip speed beyond 143 m/s and the rotor diameter beyond 246 m give rise to an unusual power curve. Concerning wind speed for high energy production, an average daily minimum and maximum wind speed of 4.58 m/s and 15.08 m/s yielded good results. Given the prevailing trend of designing large wind turbines, findings in this study are particularly helpful in understanding how capacity factor, energy production and energy losses are affected by the size of system specifications. Not only that, but these findings also have fundamental concepts that can be used to optimize the design of large offshore wind turbines. The study is equally valuable for determining suitable weather conditions and wind power potential for large offshore wind farm sites. / Dissertation (MEng (Electrical Engineering))--University of Pretoria, 2020. / Electrical, Electronic and Computer Engineering / MEng (Electrical Engineering) / Unrestricted

Wind farm layout optimization is a multidisciplinary undertaking, requiring students and researchers to integrate many skillsets in order to optimize turbine placement. There is currently a lack of useful benchmarking exercises for participants in the field to compare the efficacy of their methods. This work details the construction and completion of a set of four case studies meant to satisfy this need, with the hope of providing some insight into useful layout optimization approaches. These case studies are intended to also serve as instructive introductory exercises with which newcomers researching wind energy may incrementally practice and increase their abilities.The first two case studies were released globally and attracted participants from around the world who attempted the optimization problems. A detailed analysis of their results is presented herein.The second two case studies are currently being worked on by researchers in the field, with initial feed back regarding the formulations also included.

Wind farm layout optimization is a multidisciplinary undertaking, requiring students and researchers to integrate many skillsets in order to optimize turbine placement. There is currently a lack of useful benchmarking exercises for participants in the field to compare the efficacy of their methods. This work details the construction and completion of a set of four case studies meant to satisfy this need, with the hope of providing some insight into useful layout optimization approaches. These case studies are intended to also serve as instructive introductory exercises with which newcomers researching wind energy may incrementally practice and increase their abilities.The first two case studies were released globally and attracted participants from around the world who attempted the optimization problems. A detailed analysis of their results is presented herein.The second two case studies are currently being worked on by researchers in the field, with initial feed back regarding the formulations also included.

Externally applied loads from high winds or impacts may cause structural damage to the wind-turbine blade, and this may further affect the aerodynamic performance of the blade. Wind-turbine blades experience high vibration levels or amplitudes under high winds. Vibrations negatively affect the wind flow on the blade. This project considers the structural dynamic analysis of a small-scale wind turbine with a particular focus on the blade; it involves the finite element model development, model validation and structural analysis of the validated model. The analysis involves a small-scale wind-turbine structural response when subjected to different loading inputs. The analysis is specifically focused on on-shore systems. The use of small-scale wind-turbine systems is common however, apart from initial structural analysis during design stages, these systems have not been studied sufficiently to establish their behaviour under a variation of real-life loading conditions. On-shore wind turbines are often designed for low-wind speeds and their structural strength may be compromised. In addition, these systems experience widely-varying wind speeds from one location to another to an extent that it is extremely difficult to achieve a uniform structural performance. The main reason for solving this problem is to evaluate the structural response of the blade, with special emphasis on an 800 W Kestrel e230i. This involves the calculation of the distribution of blade deflections and stresses over the wind-turbine blade under different loading conditions. To solve the problem, a three-dimensional model of a Kestrel e230i blade was firstly developed in Autodesk Inventor Professional using geometrical measurements that were taken in the mechanical engineering laboratory. A 3D finite element model was developed in ANSYS using approximate material properties for fiberglass obtained from the literature. The model was then validated by comparing its responses with those from a number of static tests, plus a simple impact test for comparison of the first natural frequency. Finally, a number of numerical tests were conducted on the validated finite element model to determine its structural responses. The purpose of the numerical analysis was to obtain the equivalent von Mises stress and deformation produced in the blade. It was determined that under the examined different loading conditions, a higher stress contour was found to occur around the mid-span of the blade. The calculated maximum flexural stress on the blade was observed to be less than the allowable flexural stress for fiberglass which is 1,770 MPa. As expected, the highest deformation occurred at blade tip. The first critical speed of the assembled three-bladed wind turbine was found to be at 4.3 rpm. The first mode shape was observed to be in the flap-wise bending direction and for a range of rotor speeds between zero and 608 rpm, three out of a total of five mode shapes were in the flap-wise bending direction. Future studies should address issues relating blade vibrations with generated power, validation of dynamic tests, fluid-structural interaction and introduction of bio-inspired blade system. Although the performance of the bioinspired blade has not been studied in great detail, preliminary studies indicate that this system has a superior performance. / Mechanical and Industrial Engineering / M. Tech. (Electrical and Mining Engineering)

The wind industry is always seeking ways to better understand the performance of a wind turbine and improve its efficiency. During the operation phase and maintenance, wind turbines go through regular optimization. Due to the regular change in wind speed and direction, wind turbines need to be regulated and positioned accordingly. For a specific wind speed, there are a specific set of pitch angle positions. The study aims to quantify the errors in pitch angle positions and validate how much would the loss be if it deviates from its ideal pitch angle position. In this study, airfoil data from an NREL 5 MW turbine is used. Qblade is used in the simulation for error estimation. The simulation is based on BEM theory. A wind turbine blade is developed based on the given airfoil data. Multi-parameter BEM simulation is conducted for a range of wind speed, pitch angle, and rpm. Later the ideal pitch angle position for each wind speed bin is recorded. During the simulation process, downscaling the 5 MW to a 1.5 MW turbine was executed. Validation of the downscaling method was also executed. It showed good agreement with the obtained SCADA data of a working turbine. Later, pitch angle errors are introduced in the simulation.  The results are presented in two cases. Case 1 showed that at below-rated wind speed, there is a significant loss in power production if the error in pitch angle up to 1 degree.  Case 2 also shows error up to 5 degrees in region 2. This study contributes to a better understanding of the effect of pitch angle errors and their loss of power. This study took into account steady wind condition only and does not include climatic conditions or turbulence. A further study focusing on simulating in a high-fidelity setting, including real-time wind or topography conditions, is recommended to achieve a further understanding of the pitch angle errors in a wind turbine.

The increasing global participation of wind power in the overall generation ca- pacity makes it one of the most promising renewable resources. Advances in power electronics have enabled this market growth and penetration. Through a literature review, this work explores the challenges and opportunities presented by offshore wind farms, as well as the different solutions proposed concerning power electron- ics converters, collection and transmission schemes, as well as control and protection techniques. A novel power converter solution for the parallel connection of high power offshore wind turbines, suitable for HVDC collection and transmission, is presented. For the parallel operation of energy sources in an HVDC grid, DC link voltage con- trol is required. The proposed system is based on a full-power rated uncontrolled diode bridge rectifier in series with a partially-rated fully-controlled thyristor bridge rectifier. The thyristor bridge acts as a voltage regulator to ensure the flow of the desired current through each branch, where a reactor is placed in series for filtering of the DC current. AC filters are installed on the machine side to mitigate harmonic content. The mathematical modeling of the system is derived and the control design procedure is discussed. Guidelines for equipment and device specifications are pre- sented. Different setups for an experimental framework are suggested and discussed, including a conceptual application for hardware-in-the-loop real-time simulation and testing.

Vortex identification techniques are used to analyze the flow structure in a 4 x 3 array of scale model wind turbines. Q-criterion, Δ-criterion, and λ2-criterion are applied to Particle Image Velocimetry data gathered fore and aft of the last row centerline turbine. Q-criterion and λ2-criterion provide a clear indication of regions where vortical activity exists while the Δ-criterion does not. Galilean decomposition, Reynolds decomposition, vorticity, and swirling strength are used to further understand the location and behavior of the vortices. The techniques identify and display the high magnitude vortices in high shear zones resulting from the blade tips. Using Galilean and Reynolds decomposition, swirling motions are shown enveloping vortex regions in agreement with the identification criteria. The Galilean decompositions are 20% and 50% of a convective velocity of 7 m/s. As the vortices convect downstream, these vortices weaken in magnitude to approximately 25% of those present in the near wake. A high level of vortex activity is visualized as a result of the top tip of the wind turbine blade; the location where the highest vertical entrainment commences.

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This thesis summarizes the simulation and analysis performed for the MassCEC project described herein. The intent was to perform a “dry run” of the new IEC offshore wind turbine design standard, IEC 61400-3-1 and to illustrate the use of that standard in the Massachusetts Offshore Wind Energy Area. IEC 61400-3-1 is a design standard used to ensure wind turbine structural performance over the design life of the machine. Each installed wind turbine must be certified by a Certified Verification Agent using this standard before installation. The certification process typically uses a structural dynamics model to predict a turbine’s structural response in the presence of a range of operational conditions and meteorological oceanographic conditions, which are codified into Design Load Cases. The area in question is located approximately 24 km of south of Martha’s Vineyard with an assumed water depth of 40 m. The National Renewable Energy Laboratory’s FAST software (V8.12) was used to perform simulations of a large subset of the DLCs. Wind data files were generated using NREL’s TurbSim and IECWind. This thesis discusses the instructions of the standard, preparation for simulation of Design Load Cases, and analysis of results. Results from simulations show the application of the standard in detail as applied to a reference turbine. Limitations and ambiguities of the standard in the simulation of control failure cases are analyzed. The application of the standard to hurricane loading is also analyzed alongside an example case for a Category 5 hurricane. The standard is found to be fundamentally reasonable in application to a reference turbine in the Massachusetts Offshore Wind Energy Area.