Wind energy is a relatively young but rapidly expanding industry. In order for wind generation to be cost effective, it must produce energy at a minimum cost per dollar of investment. Performance characteristics such as power output versus wind speed must be optimized in order to compete with other energy sources. Also, if the utility uses wind power for a part of its generation, the output power of these turbines must have the same high quality and reliability when it enters the utility grid. The ability to vary operating speed is important in wind generation because it allows for an optimization of the transfer of power from the wind to the turbine shaft. Doubly-fed induction generators (DFIG) are an interesting solution for variable-speed systems with limited variable speed range, and are typically used in wind energy conversion systems. / The objectives of this thesis are to implement a decoupled P-Q control of a DFIG that does not rely on mechanical sensors and to design a speed and position sensorless algorithm that is robust to variations of the values of the machine parameters. The sensorless DFIG control algorithm presented in this thesis is based on a modified phasedlock loop with an improved positioning algorithm. With the measured stator voltages, stator and rotor currents, the speed and position of the DFIG are estimated. The speed is estimated independent of machine parameters, which results in a significant improvement in speed control robustness to parameter variations. In addition, the algorithm avoids using differentiation, which significantly improves its immunity to noise and does not require the measurement of the rotor voltages. Also, it is shown that the positioning algorithm has an improved operation in generator mode. Although the accuracy of the positioning algorithm is depended on machine parameters; it is shown with the designed controller that the P-Q decoupled control is robust to changes of machine parameters. Theoretical and simulation results are validated on an experimental setup.

Wind generation has become one of the most popular choices of technology for adding new generation capacity to power systems worldwide. Several factors have contributed to the increased integration of wind generation, including environmental concerns and the continual increase in fossil fuel prices. As well, recent regulations have moved toward limitations on greenhouse gases, especially in the European Union (EU). Similar laws are currently under consideration in the US and other parts of the world. Other factors have also promoted the use of wind energy, such as advances in manufacturing and control technology and the attractiveness of wind as a “green” source of energy. The large-scale integration of wind power into an electricity system introduces planning and operational challenges because of the intermittent nature of wind speed and the difficulty involved in predicting it. For these reasons, wind energy is often considered an unreliable energy source. Additional problems are associated with the integration of large-scale wind farms into an electrical grid, among which wind power fluctuation is the most challenging. To maximize the penetration level of wind energy in a grid, a reliable technology must be developed in order to eliminate or at least decrease wind power fluctuation. The primary goal of this thesis was to develop methods of maximizing the penetration level of wind energy conversion systems (WECSs) into a grid, which requires mitigating wind power fluctuation. A robust control technique has therefore been developed for mitigating wind power fluctuation. This control technique exploits historical environmental data collected over a number of years in order to evaluate the profile of the output power of a variety of wind energy conversion systems (WECSs). The developed control technique was applied to Types A and C WECSs modifying the pitch angle controller of Type A WECS and the back-to-back converter control of Type C WECS. The Attachment of a storage device to the WECSs after the control technique is applied was investigated from both an economic and a technical point of view. The optimum sizing and siting of the wind energy conversion system equipped with the proposed control technique was also studied. This research is expected to contribute to the advancement of WECS technology by presenting a feasible solution to the problems associated with the integration of large-scale WECSs into electrical grids.

Thesis (M.S.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 12, 2008) Includes bibliographical references (p. 64-66).

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Douglas S. Cairns. Includes bibliographical references (leaves 138-143).

Thesis (M.S.)--University of Wisconsin--Madison, 1996. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 143-162).

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 140-147).

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / Globally governments are faced with challenges in the energy sector which are exacerbated by uncertain financial markets and resource limitations. The over utilization of fossil fuels for electricity generation has had a profound impact on the climatic conditions on earth. Coal power stations release carbon dioxide (CO2) during the combustion process and studies show that concentrations have sharply risen in the atmosphere. Adverse environmental conditions like global warming exist as a result of high greenhouse gas (GHG) emissions in particular CO2. In 2015 Eskom constructed Sere Wind farm with a supply capability of 100 MW. Due to the lack of technical expertise and skills with regard to the new technology within Eskom, Siemens was offered a 5 year maintenance contract. Siemens also provides training on basic operation and maintenance (O&M) of the wind farm to Eskom staff. This excludes specialised training on Siemens Turbine Condition Monitoring (TCM) systems which is a critical part to develop optimum maintenance strategies. This shortage of specialised skills in the application of condition monitoring techniques within Eskom is a major concern. If the most cost effective maintenance strategies during the contract period are implemented, the long term plant health and design life of Sere wind farm will be reduced. There is a need to develop new condition monitoring techniques to complement or address the shortcomings of the existing systems. Developing these skills will increase the understanding of the technology and improve the operating and maintenance of Sere wind farm.

A wind turbine array was constructed in the wind tunnel at Portland State University in a standard Cartesian arrangement. Configurations of the turbine array were tested with rotor blades set to rotate in either a clockwise or counter-clockwise sense. Measurements of velocity were made with stereo particle-image velocimetry. Mean statistics of velocities and Reynolds stresses clearly show the effect of direction of rotation of rotor blades for both entrance and exit row turbines. Rotational sense of the turbine blades is visible in the mean spanwise velocity W and the Reynolds shear stress -[macron over vw]. The normalized anisotropy tensor was decomposed yielding invariants [lowercase eta] and [lowercase xi], which are plotted onto the Lumley triangle. Invariants of the normalized Reynolds stress anisotropy tensor indicate that distinct characters of turbulence exist in regions of the wake following the nacelle and the rotor blade tips. Eigendecomposition of the tensor yields principle components and corresponding coordinate system transformations. Characteristic spheroids are composed with the eigenvalues from the decomposition yielding shapes predicted by the Lumley triangle. Rotation of the coordinate system defined by the eigenvectors demonstrates streamwise trends, especially trailing the top rotor tip and below the hub of the rotors. Direction of rotation of rotor blades is evidenced in the orientation of characteristic spheroids according to principle axes. The characteristic spheroids of the anisotropy tensor and their relate alignments varies between cases clearly seen in the inflows to exit row turbines. There the normalized Reynolds stress anisotropy tensor shows cumulative effects of the rotational sense of upstream turbines. Comparison between the invariants of the Reynolds stress anisotropy tensor and terms from the mean mechanical energy equation indicate a correlation between the degree of anisotropy and the regions of the wind turbine wakes where turbulence kinetic energy is produced. The flux of kinetic energy into the momentum-deficit area of the wake from above the canopy is associated with prolate characteristic spheroids. Flux upward into the wake from below the rotor area is associate with oblate characteristic spheroids. Turbulence in the region of the flow directly following the nacelle of the wind turbines demonstrates more isotropy compared to the regions following the rotor blades. The power and power coefficients for wind turbines indicate that flow structures on the order of magnitude of the spanwise turbine spacing that increase turbine efficiency depending on particular array configuration.

No description available.

With the rising cost of petroleum, concerns about exhausting the fossil fuels we depend on for energy, and the subsequent impacts that the burning of these types of fuels have on the environment, countries around the world are paying close attention to the development of renewable types of energy. Consequently, researchers have been trying to develop ways to take advantage of different types of clean and renewable energy sources. Wind energy production, in particular, has been growing at an increasingly rapid rate, and will continue to do so in the future. In fact, it has become an integral part in supplying future energy needs, making further advancements in the field exceedingly critical. A 2 MW wind energy conversion system (WECS) is presented and has been simulated via the dynamic simulation software Simulink. This WECS consists of a 2 MW permanent magnet synchronous generator connected to the transmission grid through a power conversion scheme. The topology of this converter system consists of a passive AC/DC rectifier as well as a PWM DC/AC IGBT inverter, used to interface the DC link with the grid. The inverter has an integrated current control system for power factor correction to improve output power stability. The described WECS enhances grid-side tolerance by buffering wind power disturbances demonstrated by its capability to isolate the grid from wind speed fluctuations. It also optimizes wind energy capture through harmonic filtering, enhancing output power quality. These findings have the potential to lead to further advancements including the capability for island operation and integration to a smart grid.