Wind turbine aerodynamics are characterized by several coefficients, most notably the thrust, power, and axial induction, which is the fractional decrease of the free stream wind speed to the rotor plane. Current turbine designs aim to maximize these coefficients to reach what is generally considered to be maximum aerodynamic efficiency. Such rotors are referred to as a Betz-optimal rotor. This thesis examines a new method called “Low-Induction Rotors (LIR)” for increasing aerodynamic efficiency by decreasing the thrust loading of the blade. A family of low induction rotors (LIRs) can be derived from a reference wind turbine (RWT) by using the root bending moment as a constraint. Using the root bending moment of the RWT and imposed loading, new rotor lengths are derived. The family of low induction rotors are characterized by lower thrust loading across the blade. Prandtl’s bell shaped loading distribution was used to define the distribution of spanwise thrust since it is better fit for long-thin airfoils. Momentum Theory and Blade Element and Momentum theory were used to solve for the rotor power coefficient in two different ways, either including or excluding tip-losses. The family of rotors was then analyzed to determine power output. It was found that more power was produced as the rotor length increases and thrust loading decreased. The National Renewable Energy Lab’s AeroDyn software was used to conduct cp-λ sweeps on 6 selected rotors (128m, 137m, 147m, 156m, 167m, and 177m) to determine how power output was affected by changes in wind speed. The cp-λ analysis showed that the longer rotors with lower induction were less sensitive to changes in wind speed. The low induction rotors minimized a change in the coefficient of power as the pitch and tip speed ratio were changed. Low induction rotors are a promising field of wind energy, while maintaining the forces are the turbine hub, longer rotors with lower aerodynamic loading can be used to generate a more stable power supply.

Wind power generation does, on the one hand, contribute to a less polluting and more sustainable electric power generation mix. On the other hand, the uncertainty and the variability of the power output do challenge the operation of the power system: hourly variations in wind power generation are hardly predictable in a precise way. To decrease the need for balancing power, it might be beneficial from the overall system-perspective to subject power generating companies to stricter balancing incentives/rules. The way the market is designed has become crucial to exploit the existing flexibility in the power system and to increase the efficiency in its operation: inappropriate market designs can counteract all technical achievements. The work conducted for this thesis is embedded in a project on wind power integration and electricity market design following the aim to develop a simulation tool to analyse the consequences of changes in specific market rules. This thesis analyses wind power variations and forecast errors in the Swedish power system and explores the question whether internal ex-ante self-balancing can efficiently reduce the need for balancing power. Applying internal ex-ante self-balancing, every power generating company re-schedules its own power plants in order to balance its commitments towards other market actors with its newest production forecast. This is done shortly before the hour of delivery. To assess the value of this self-balancing, possible trading and scheduling decisions for power generating companies are modelled based on a hydro-thermal generation portfolio within the framework of the Nordic electricity market design. The model is based on a sequence of mixed-integer linear optimisation problems for the clearing of the different sub-markets. Both the data and the model have an hourly time resolution. In a case study, the model is applied on a simplified test-system. The need of real-time balancing by the transmission system operator, the total variable generation cost of the system, as well as the extent to which the power generating companies re-scheduled their production are then used as indicators to evaluate self-balancing. / <p>QC 20121017</p> / Short-term hydro power planning in power systems with large amounts of wind power / Elektra 36141: Korttidsplanering av vatten-värmekraftsystem vid stora mängder vindkraft: System-perspektivet

The goal of this Masters Thesis research is to evaluate alternative transmission systems from remote wind farms to the main grid using low-frequency AC technology. Low frequency means a frequency lower than nominal frequency (60/50Hz). The low-frequency AC network can be connected to the power grid at major substations via cyclo-converters that provide a low-cost interconnection and synchronization with the main grid. Cyclo-converter technology is utilized to minimize costs which result in systems of 20/16.66 Hz (for 60/50Hz systems respectively). Low frequency transmission has the potential to provide an attractive solution in terms of economics and technical merits.

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Call number: LD2668 .T4 1978 P63 / Master of Science

The demand and need for alternative obstruction marking has become a significant challenge for the wind power development in Sweden. While the development of wind turbines pushes for higher heights, the need to denote them as possible obstacles for aviation increase. To reduce undesired effects of the aviation warning lights in the landscape, various technologies for reducing the light emitted have been developed. One of these technologies control the lights’ output by dimming them based on measurements of the prevailing visibility in the vicinity of the wind farm.Visibility controlled obstruction lighting has not yet been used in Swedish wind farms. This thesis will investigate how a system can be applied from different viewpoints and what would be gained in a wind farm in northern Sweden.By reviewing literature, interviewing key-persons, studying a case with application of Finnish regulations and estimating the performance during different conditions, and discussing the results, conclusions could be drawn. The findings are general recommendations for acceptance, an aviation risk that need to be considered, indications of preferable regulation applications and approximations of the performance and possible gain.

Wind generation is one of the most successful sources of renewable energy for the production of electrical energy. Wind power offers relatively high capacities, with generation costs that are becoming competitive with conventional energy sources. However, a major problem to its effective use as a power source is the fact that it is both intermittent and diffuse as wind speed is highly variable and site-specific. This is translated in large voltage and frequency excursions and dynamically unstable situations when fast wind power changes. Very high wind speeds will result in sudden loss of wind generator production. The requirement to ensure that sufficient spinning reserve capacity exists within the system to compensate for sudden loss of generation becomes crucial. From the utilities operators’point of view, the primary objective is the security of the system, followed by the quality of the supplied power. In order to guard the system security and quality of supply and retain acceptable levels, a maximum allowed wind power penetration (wind margin) is normally assumed by the operators. Very conservative methods are used to assess the impact of wind power and the consequences turn to under-exploitation of the wind power potential in a given region. This thesis presents the study of actual methods of wind power assessment, divided into three parts: 1. Part I: Impact on the Security of Power Systems 2. Part II: Impact on the Power Quality 3. Part III: Impact on the Dynamic Security of Power Systems

Environmental concerns caused by burning fossil fuel and the safety concerns associated with nuclear power plants have led to increased interest and investment in wind power. Wind penetration in power systems is rapidly increasing world-wide and creating significant impacts on the overall system performance. The impact of wind generation on the overall system performance increases substantially as wind penetration in power systems continues to increase to relatively high levels. It becomes increasingly important to accurately model the wind behavior, the interaction with other wind sources and conventional sources, and incorporate the characteristics of the energy demand in order to carry out a realistic evaluation of system reliability. Analytical methods using annual wind models have generally been used for reliability evaluation of wind integrated power systems. These methods do not recognize the seasonal and diurnal load following capability of wind. In this thesis, the system adequacy indices are first evaluated on an annual and seasonal basis and then a technique is developed to incorporate the diurnal load following capability of wind. Power systems with high wind penetrations are often connected to multiple wind farms at different geographic locations. Wind speed correlations between the different wind farms largely affect the total wind power generation characteristics of such systems, and therefore should be an important parameter in the wind modeling process. Another concern that arises is the lack of time-synchronized data, especially at the planning phase, which limits the capability of system planners to accurately model multiple correlated wind farms using simple analytical methods. A simple and appropriate probabilistic analytical wind model which can be used for adequacy evaluation of multiple wind-integrated power systems is proposed in the thesis. A simple analytical method to develop an approximate wind model of multiple correlated wind farms when time-synchronized wind data is not available is also proposed in the thesis. The methods to incorporate correlations in the adequacy evaluations of wind integrated power systems presented in the thesis are expected to be highly useful for system planners and policy makers as wind penetration continues to increase.

This study was carried out with the aim of finding out the challenges towards Feed-in Tariff law instrument in order to promote renewable energy in Iran. The targets of the study were chosen among authorities and investors in the field of wind energy. Wind power was selected as the case study because of its more popularity among investors. Qualitative research design was used to conduct the study and semi-structured interviews served as the method. Although there were a few studies done with the focus on renewable energy challenges in Iran, however, none of them focused on the challenges through Feed-in Tariff law. The results show that the law's long administrative process, lack of communication between authorities and investors, and rather low remuneration rate are the barriers to promote renewable energy in Iran. Furthermore, lack of financial assistance and imposed political and economical sanctions against Iran play an important role in this regard.

More and more attention has been paid to the energy crisis due to the increasing energy demand from industrial and commercial applications. The utilisation of wind power, which is considered as one of the most promising renewable energy sources, has grown rapidly in the last three decades. In recent years, many power converter techniques have been developed to integrate wind power with the electrical grid. The use of power electronic converters allows for variable speed operation of wind turbines, and enhanced power extraction. This work, which is supported by EPSRC and Nheolis under the DHPA scheme, focuses on the design and analysis of control systems for wind power. In this work, two of the most popular AC-DC-AC topologies with permanent magnet synchronous generators (PMSG) have been developed. One consists of an uncontrollable rectifier, a boost converter and an inverter and a current control scheme is proposed to achieve the maximum power point tracking (MPPT). In the control strategy, the output current of the uncontrollable rectifier is controlled by a boost converter according to the current reference, which is determined by a climbing algorithm, to achieve MPPT. The synchronverter technology has been applied to control the inverter for the grid-connection. An experimental setup based on DSP has been designed to implement all the above mentioned experiments. In addition, a synchronverter-based parallel control strategy, which consists of a frequency droop loop and a voltage droop loop to achieve accurate sharing of real power and reactive power respectively, has been further studied. Moreover, a control strategy based on the synchronverter has been presented to force the inverter to have capacitive output impedance, so that the quality of the output voltage is improved. Abstract The other topology consists of a full-scale back-to-back converter, of which the rectifier is controllable. Two control strategies have been proposed to operate a three-phase rectifier to mimic a synchronous motor, following the idea of synchronverters to operate inverters to mimic synchronous generators. In the proposed schemes, the real power extracted from the source and the output voltage are the control variables, respectively, hence they can be employed in different applications. Furthermore, improved control strategies are proposed to self-synchronise with the grid. This does not only improve the performance of the system but also considerably reduces the complexity of the overall controller. All experiments have been implemented on a test rig based on dSPACE to demonstrate the excellent performance of the proposed control strategies with unity power factor, sinusoidal currents and good dynamics. Finally, an original control strategy based on the synchronverter technology has been proposed for back-to-back converters in wind power applications to make the whole system behave as a generator-motor-generator system.