Special Issue "Wind Turbines 2013"
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A special issue of Energies (ISSN 1996-1073).
Deadline for manuscript submissions: closed (30 April 2013)
Special Issue Editor
Guest Editor
Prof. Dr. Frede Blaabjerg
Institute of Energy Technology, Aalborg University, Pontoppidanstraede 101, DK-9220 Aalborg East, Denmark
E-Mail: fbl@et.aau.dk
Phone: +45 9635 9254
Fax: +45 9815 1411
Interests: wind power research; power electronics; control of wind turbines and wind farms; interconnection to grid; generators; power converters; ride-through operation
Special Issue Information
Dear Colleagues,
This issue is an continuation of the previous successful special issue "Wind Turbines". Similarly, this issue also focuses on recent advances in the wind energy sector on a wide range of topics, including: wind resource mapping, wind intermittency issues, aerodynamics, foundations, aeroelasticity, wind turbine technologies, control of wind turbines, diagnostics, generator concepts incl gearless concepts, power electronic converters, grid interconnection, ride-through operation, protection, wind farm layouts - optimization and control, reliability, operations and maintenance, effects of wind farms on local and global climate, wind power stations, smart-grid and micro-grid related to wind turbine operation.
Prof. Dr. Frede Blaabjerg
Guest Editor
Submission
Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.
Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed Open Access monthly journal published by MDPI.
Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs).
Published Papers (5 papers)
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Received: 20 November 2012; in revised form: 20 February 2013 / Accepted: 20 February 2013 / Published: 25 February 2013
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Abstract: This paper presents an improved control strategy for both the rotor side converter (RSC) and grid side converter (GSC) of a doubly fed induction generator (DFIG)-based wind turbine (WT) system to enhance the low voltage ride through (LVRT) capability. Within the proposed control strategy, the RSC control introduces transient feed-forward compensation terms to mitigate the high frequency harmonic components and reduce the surge in the rotor currents. The proposed GSC control scheme also introduces a compensation term reflecting the instantaneous variation of the output power of the rotor side converter with consideration of the instantaneous power of grid filter impendence to keep the dc-link voltage nearly constant during the grid faults. To provide precise control, non-ideal proportional resonant (PR) controllers for both the RSC and GSC current regulation are employed to further improve dynamic performance. Simulations performed in Matlab/Simulink verify the effectiveness of the proposed control strategy.
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Received: 14 March 2013; in revised form: 17 April 2013 / Accepted: 23 April 2013 / Published: 29 April 2013
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Abstract: Large-eddy simulation is used to study the influence of free-atmosphere stratification on the structure of atmospheric boundary-layer flow inside and above very large wind farms, as well as the power extracted by the wind turbines. In the simulations, tuning-free Lagrangian scale-dependent dynamic models are used to model the subgrid-scale turbulent fluxes, while the turbine-induced forces are parameterized with an actuator-disk model. It is shown that for a given surface cover (with and without turbines) thermal stratification of the free atmosphere reduces the entrainment from the flow above compared with the unstratified case, leading to lower boundary-layer depth. Due to the fact that in very large wind farms vertical energy transport associated with turbulence is the only source of kinetic energy, lower entrainment leads to lower power production by the wind turbines. In particular, for the wind-turbine arrangements considered in the present work, the power output from the wind farms is reduced by about 35% when the potential temperature lapse rate in the free atmosphere increases from 1 to 10 K/km (within the range of values typically observed in the atmosphere). Moreover, it is shown that the presence of the turbines has significant effect on the growth of the boundary layer. Inspired by the obtained results, a simple one-dimensional model is developed to account for the effect of free-atmosphere stability on the mean flow and the power output from very large wind farms.
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Received: 11 April 2013; in revised form: 8 May 2013 / Accepted: 10 May 2013 / Published: 17 May 2013
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Abstract: This paper presents a coordinated control method for a doubly-fed induction generator (DFIG)-based wind-power generation system with a series grid-side converter (SGSC) under distorted grid voltage conditions. The detailed mathematical models of the DFIG system with SGSC are developed in the multiple synchronous rotating reference frames. In order to counteract the adverse effects of the voltage harmonics upon the DFIG, the SGSC generates series compensation control voltages to keep the stator voltage sinusoidal and symmetrical, which allows the use of the conventional vector control strategy for the rotor-side converter (RSC), regardless of grid voltage harmonics. Meanwhile, two control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in total active and reactive power entering the grid or suppressing the fifth- and seventh-order harmonic currents injected to the grid. Furthermore, the respective PI-R controller in the positive synchronous reference frame for the SGSC voltage control and PGSC current control have been developed to achieve precise and rapid regulation of the corresponding components. Finally, the proposed coordinated control strategy has been fully validated by the simulation results of a 2 MW DFIG-based wind turbine with SGSC under distorted grid voltage conditions.
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Received: 7 March 2013; in revised form: 20 May 2013 / Accepted: 22 May 2013 / Published: 5 June 2013
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Abstract: Three different horizontal axis wind turbine (HAWT) blade geometries with the same diameter of 0.72 m using the same NACA4418 airfoil profile have been investigated both experimentally and numerically. The first is an optimum (OPT) blade shape, obtained using improved blade element momentum (BEM) theory. A detailed description of the blade geometry is also given. The second is an untapered and optimum twist (UOT) blade with the same twist distributions as the OPT blade. The third blade is untapered and untwisted (UUT). Wind tunnel experiments were used to measure the power coefficients of these blades, and the results indicate that both the OPT and UOT blades perform with the same maximum power coefficient, Cp = 0.428, but it is located at different tip speed ratio, λ = 4.92 for the OPT blade and λ = 4.32 for the UOT blade. The UUT blade has a maximum power coefficient of Cp = 0.210 at λ = 3.86. After the tests, numerical simulations were performed using a full three-dimensional computational fluid dynamics (CFD) method using the k-ω SST turbulence model. It has been found that CFD predictions reproduce the most accurate model power coefficients. The good agreement between the measured and computed power coefficients of the three models strongly suggest that accurate predictions of HAWT blade performance at full-scale conditions are also possible using the CFD method.
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Received: 27 April 2013; in revised form: 29 May 2013 / Accepted: 30 May 2013 / Published: 14 June 2013
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Abstract: Radar services are occasionally affected by wind farms. This paper presents a comprehensive description of the effects that a wind farm may cause on the different radar services, and it compiles a review of the recent research results regarding the mitigation techniques to minimize this impact. Mitigation techniques to be applied at the wind farm and on the radar systems are described. The development of thorough impact studies before the wind farm is installed is presented as the best way to analyze in advance the potential for interference, and subsequently identify the possible solutions to allow the coexistence of wind farms and radar services.
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Last update: 13 November 2012
