Active Load Control Techniques for Wind Turbines Focusing on Mechanical Design of a Microtab System PDF Download

Author: Scott Jeremy Johnson
Publisher:
ISBN:
Category :
Languages : en
Pages : 338

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 43

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Book Description
With public concern over the security and reliability of our existing electricity infrastructure and the resurgence of wind energy, the wind industry offers an immediate, first point of entry for the application and demonstration of an active load control technology. An innovative microtab approach is being investigated and demonstrated for active aerodynamic load control applications under the mid-year LDRD (June-Sept. 2002) effort. With many of these million dollar turbines failing at only half the design lifespans, conventional techniques for stiffening rotors, enlarging generators and gearboxes, and reinforcing towers are insufficient to accommodate the demands for bigger, taller and more powerful turbines. The DOE through the National Renewable Energy Laboratory (NREL) supports R & D efforts to develop lighter, more efficient and longer lasting wind turbines and advance turbine components. However, as wind turbine systems continue to increase in size and complexity, fundamental research and technology development has not kept pace with needs. New technologies to increase turbine life spans and to reduce costs are needed to realize wind electricity generation potentials. It is becoming quite evident that without a better understanding of static and dynamic response to normal and abnormal operating loads coupled with sophisticated flow analysis and control techniques, large turbine operating life and component life will be severely limited. Promising technologies include active load control and load alleviation systems to mitigate peak loads from damaging key components. This project addresses science and engineering challenges of developing enabling technologies for active load control for turbine applications using an innovative, translational microtab approach. Figure 1.1 illustrates the microtabs as applied on a wind turbine system. Extending wind turbine operating life is a crucial component for reducing the cost of wind-generated electricity, enabling wind energy market penetration and improving the reliability of the nation's renewable electrical generation infrastructure. This project also provides enabling technologies for improving turbine efficiency and durability to support the DOE and NNSA missions of providing energy security and reliability without contributing to greenhouse gas emissions and for decreasing dependence on foreign fuel sources. In addition to wind generator applications, the realization of a ''smart'' controllable structure for load control using the microtab approach has the potential to revolutionize design of other complex systems. Driven by cost and safety, both passive and active flow control for steady and unsteady conditions have been actively investigated by NASA, DARPA, DOE and other research institutions for application on rotorcraft, UAVs, marine vessels and wind turbine applications. The potential to obtain revolutionary advances in aerodynamic hydrodynamic performance, safety, maneuverability and service life by decreasing loads is an attractive prospect across many industries.

Author:
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ISBN:
Category :
Languages : en
Pages : 132

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This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as 'smart structures' or 'smart rotor control'. This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device.

Author: Qiuwei Wu
Publisher: John Wiley & Sons
ISBN: 1119236266
Category : Science
Languages : en
Pages : 281

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An essential reference to the modeling techniques of wind turbine systems for the application of advanced control methods This book covers the modeling of wind power and application of modern control methods to the wind power control—specifically the models of type 3 and type 4 wind turbines. The modeling aspects will help readers to streamline the wind turbine and wind power plant modeling, and reduce the burden of power system simulations to investigate the impact of wind power on power systems. The use of modern control methods will help technology development, especially from the perspective of manufactures. Chapter coverage includes: status of wind power development, grid code requirements for wind power integration; modeling and control of doubly fed induction generator (DFIG) wind turbine generator (WTG); optimal control strategy for load reduction of full scale converter (FSC) WTG; clustering based WTG model linearization; adaptive control of wind turbines for maximum power point tracking (MPPT); distributed model predictive active power control of wind power plants and energy storage systems; model predictive voltage control of wind power plants; control of wind power plant clusters; and fault ride-through capability enhancement of VSC HVDC connected offshore wind power plants. Modeling and Modern Control of Wind Power also features tables, illustrations, case studies, and an appendix showing a selection of typical test systems and the code of adaptive and distributed model predictive control. Analyzes the developments in control methods for wind turbines (focusing on type 3 and type 4 wind turbines) Provides an overview of the latest changes in grid code requirements for wind power integration Reviews the operation characteristics of the FSC and DFIG WTG Presents production efficiency improvement of WTG under uncertainties and disturbances with adaptive control Deals with model predictive active and reactive power control of wind power plants Describes enhanced control of VSC HVDC connected offshore wind power plants Modeling and Modern Control of Wind Power is ideal for PhD students and researchers studying the field, but is also highly beneficial to engineers and transmission system operators (TSOs), wind turbine manufacturers, and consulting companies.

Author: I. Kade Wiratama
Publisher:
ISBN:
Category :
Languages : en
Pages :

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As a result of the significant growth of wind turbines in size, blade load control has become the main challenge for large wind turbines. Many advanced techniques have been investigated aiming at developing control devices to ease blade loading. Individual pitch control system, adaptive blades, trailing edge microtabs, morphing aerofoils, ailerons, trailing edge flaps, and telescopic blades are among these techniques. Most of the above advanced technologies are currently implemented in, or are under investigation to be utilised, for blade load alleviation. The present study aims at investigating the potential benefits of these advanced techniques in enhancing the energy capture capabilities rather than blade load alleviation. To achieve this goal the research is carried out in three directions: (i) development of a simulation software tool suitable for wind turbines utilising nonconventional control systems, (ii) development of a blade design optimisation tool capable of optimising the topology of blades equipped with nonconventional control systems, and (iii) carrying out design optimisation case studies with the objective of power extraction enhancement towards investigating the feasibility of advanced technologies, initially developed for load alleviation of large blades, for power extraction enhancement. Three nonconventional control systems, namely, microtab, trailing edge flap and telescopic blades are investigated. A software tool, AWTSim, is especially developed for aerodynamic simulation of wind turbines utilising blades equipped with microtabs and trailing edge flap as well as telescopic blades. As part of the aerodynamic simulation of these wind turbines, the control system must be also simulated. The simulation of the control system is carried out via solving an optimisation problem which gives the best value for the controlling parameter at each wind turbine run condition. Developing a genetic algorithm optimisation tool which is especially designed for wind turbine blades and integrating it with AWTSim, a design optimisation tool for blades equipped with nonconventional control system is constructed. The design optimisation tool, AWTSimD, is employed to carry out design case studies. The results of design case studies reveal that for constant speed rotors, optimised telescopic blades are more effective than flaps and microtabs in power enhancement. However, in comparison with flap and microtabs, telescopic blades have two disadvantages: (i) complexity in telescopic mechanism and the added weight and (ii) increased blade loading. It is also shown that flaps are more efficient than microtabs, and that the location and the size of flaps are key parameters in design. It is also shown that optimisation of the blade pretwist has a significant influence on the energy extraction enhancement. That is, to gain the maximum benefit of installing flaps and microtabs on blades, the baseline blades must be redesigned.

Author: Abdel Ghani Aissaoui
Publisher: BoD – Books on Demand
ISBN: 9535124951
Category : Technology & Engineering
Languages : en
Pages : 354

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Renewable energies constitute excellent solutions to both the increase of energy consumption and environment problems. Among these energies, wind energy is very interesting. Wind energy is the subject of advanced research. In the development of wind turbine, the design of its different structures is very important. It will ensure: the robustness of the system, the energy efficiency, the optimal cost and the high reliability. The use of advanced control technology and new technology products allows bringing the wind energy conversion system in its optimal operating mode. Different strategies of control can be applied on generators, systems relating to blades, etc. in order to extract maximal power from the wind. The goal of this book is to present recent works on design, control and applications in wind energy conversion systems.

Author: Kevin Lee Jackson
Publisher:
ISBN:
Category :
Languages : en
Pages : 326

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Author: Zheren Ma
Publisher:
ISBN:
Category :
Languages : en
Pages : 308

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Wind energy is one of the most abundant renewable energy sources that can meet future energy demands. Despite its fast growth, wind energy is still a marginal player in electricity generation. The key issues preventing wider deployment of wind turbines include low energy conversion efficiency, high maintenance cost, wind intermittency and unpredictability etc. These issues lead to considerably higher cost of wind power compared to that of traditional power sources. This work is focused on control designs to overcome the above challenges. First, control algorithms are developed for energy capture maximization. During partial load operation, wind turbine rotor speed is continuously adjusted to remain optimal operation by manipulating the electromagnetic torque applied to the generator. In this dissertation, a dynamic programming based real-time controller (DPRC) and a gain modified optimal torque controller (GMOTC) are developed for faster convergence to optimal power operation under volatile wind speed and better robustness against modeling uncertainties. Secondly, fatigue loading mitigation techniques are developed to reduce the maintenance cost of a wind turbine. During partial load operation, a generator torque-based fatigue mitigation method is devised to reduce the impact of exacerbated tower bending moments associated with the resonance effect. During full load operation, a H2 optimization has been carried out for gain scheduling of a Proportional-Integral blade pitch controller. It improves speed regulation and reduces drivetrain fatigue loading with less oscillations of turbine rotor speed and generator torque. Thirdly, battery energy storage systems (BESS) have been integrated with wind turbines to mitigate wind intermittence and make wind power dispatchable as traditional power sources. Equipped with a probabilistic wind speed forecasting model, a new power scheduling and real-time control approach has been proposed to improve the performance of the integrated system. Finally, control designs are oriented to wind turbine participation in grid primary frequency regulation. The fast active power injection/absorption capability of wind turbine enables it to rapidly change its power output for stablizing the grid frequency following an sudden power imbalance event. In addition to quick response to grid frequency deviation event, the proposed controller guarantees turbine stability with smooth control actions.

Author: Aubryn Murray Cooperman
Publisher:
ISBN: 9781267967886
Category :
Languages : en
Pages :

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Increases in wind turbine size have made controlling loads on the blades an important consideration for future turbine designs. One approach that could reduce extreme loads and minimize load variation is to incorporate active control devices into the blades that are able to change the aerodynamic forces acting on the turbine. A wind tunnel model has been constructed to allow testing of different active aerodynamic load control devices. Two such devices have been tested in the UC Davis Aeronautical Wind Tunnel: microtabs and microjets. Microtabs are small surfaces oriented perpendicular to an airfoil surface that can be deployed and retracted to alter the lift coefficient of the airfoil. Microjets produce similar effects using air blown perpendicular to the airfoil surface. Results are presented here for both static and dynamic performance of the two devices. Microtabs, located at 95% chord on the lower surface and 90% chord on the upper surface, with a height of 1% chord, produce a change in the lift coefficient of 0.18, increasing lift when deployed on the lower surface and decreasing lift when deployed on the upper surface. Microjets with a momentum coefficient of 0.006 at the same locations produce a change in the lift coefficient of 0.19. The activation time for both devices is less than 0.3 s, which is rapid compared to typical gust rise times.The potential of active device to mitigate changes in loads was tested using simulated gusts. The gusts were produced in the wind tunnel by accelerating the test section air speed at rates of up to 7 ft/s2. Open-loop control of microtabs was tested in two modes: simultaneous and sequential tab deployment. Activating all tabs along the model span simultaneously was found to produce a change in the loads that occurred more rapidly than a gust. Sequential tab deployment more closely matched the rates of change due to gusts and tab deployment. A closed-loop control system was developed for the microtabs using a simple feedback control based on lift measurements from a six-component balance. An alternative input to the control system that would be easier to implement on a turbine was also investigated: the lift force was estimated using the difference in surface pressure at 15% chord. Both control system approaches were found to decrease lift deviations by around 50% during rapid changes in the free stream air speed.

Author: Mayank Chetan
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 0

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Wind energy over the years has positioned itself to become a primary source of renewable energy and this is attributed to the reduction in the Levelized Cost of Energy (LCOE). Historically, this is accomplished by an increase in tower heights which allow access to higher wind speeds, and also by increasing rotor diameters which allow for more power capture. However, there are significant challenges that come with these large turbines like aeroelastic instabilities of the blades due to their long and slender nature, and the need for more robust turbine components that can withstand the larger loads associated with large turbines. This has motivated the development of design strategies that incorporate different methods of load alleviation to achieve optimized wind turbine designs that can result in lower LCOE. This dissertation presents various methods of designing wind turbine rotors that take advantage of passive and active load reduction strategies. First, classical flutter is addressed for the design of large blades. Flutter is an aeroelastic instability that contributes to fatigue damage, or in the worst case can least to sudden catastrophic turbine failure. A comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two- and three-bladed wind turbine blade designs is carried out. Further, a study is performed to evaluate mitigation of flutter in the design process via structural redesign by evaluating the effect of leadingvi edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass. This flutter structural mitigation study is conducted for two wind turbine designs, one a two-bladed rotor and the other a three-bladed rotor. Second, a new rotor design methodology is developed to integrate active load control in the form of controllable gurney flaps. A comprehensive sequential iterative design procedure is developed that integrates aerodynamics, structural, and baseline turbine control system design with advanced active load control into a design process. This procedure also takes into account the contribution of loads on all major components of the turbine. To realize the best LCOE reduction solution, new methods to evaluate blade structural properties are developed wherein, the reductions in damage equivalent loads (i.e.; fatigue loads) due to a generic active load control system are mapped to structural design improvements in terms of blade mass reduction, cost reduction in other major turbine components, and LCOE reductions that result from integration and redesign of the turbine with the active load control system. Third, using the design methodologies established, newer rotor designs with a larger rotor radius are explored to examine the impacts of the active load control system. These rotors take advantage of the fatigue load reductions due to the controllable gurney flaps integrated into the design. The effect of the controllable gurney flaps is evaluated for various blade and non-blade component loads on the turbine. This methodology results in larger rotors that have increased energy capture and reduced LCOE’s. For this study, two different turbine operating strategies are followed, one limits the turbine power to that of the baseline while the other allows the turbine to extract more power at higher wind speeds. Finally, a method is introduced to support the realization of new passive and active load mitigation strategies by improving prototype wind turbine development. A novel method of developing a multi-fidelity digital twin structural model of a wind turbine blade is presented. The digital twin model development methodology, presented herein, involves a novel calibration process to integrate a wide range of information including design specifications, manufacturing information, and structural testing data (modal and static) to produce a multi-fidelity digital twin structural model: a detailed high-fidelity model (i.e., 3D FEA) and consistent beam-type models for aeroelastic simulation. Digital twin models are useful to cost-effectively evaluate the performance of new technologies in the field like novel downwind rotors and controllable gurney flaps. Finally, the new methodology is demonstrated for an as-built two-bladed downwind prototype rotor resulting in a multi-fidelity digital twin model which has a 1% match in mass properties, 3.2% in blade frequencies, and 6% in deflection to the as-built blade. The rotor examined is the SUMR – Demonstrator (SUMR-D), which was installed on the Controls Advanced Research Testbed (CART-2) wind turbine at the National Wind Technology Center. The digital twin model developed here was utilized to design controllers to safely operate SUMR-D in field tests, which are providing additional data for further evaluation and development of the multi-fidelity digital twin structural model.