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    Impact of Tower Shadow Effect and Wind Shear Effect on Wind Turbine Gearbox

    , M.Sc. Thesis Sharif University of Technology Taheri, Mohammad (Author) ; Durali, Mohammad (Supervisor)
    Use of renewable energy has already increased significantly. One of the renewable and suitable sources for replacement with fossil fuels is wind energy, especially wind turbines. But the design, construction, installation maintenance and operation of wind turbines are relatively expensive. One of the most expensive parts of a wind turbine is its gearbox. Wind turbines gearbox due to fluctuating loads unexpected is likely to suffer a premature fatigue. The purpose of this project is to calculate some of the oscillating loads applied to the gearbox and then to investigate the effect of these loads on the service life of the gearbox components. Tower shadow effect and wind shear effect are the... 

    A new correlation on the MEXICO experiment using a 3D enhanced blade element momentum technique

    , Article International Journal of Sustainable Energy ; Vol. 33, issue. 2 , 2014 , pp. 448-460 ; ISSN: 14786451 Mahmoodi, E ; Jafari, A ; Schaffarczyk, A. P ; Keyhani, A ; Mahmoudi, J ; Sharif University of Technology
    The blade element momentum (BEM) theory is based on the actuator disc (AD) model, which is probably the oldest analytical tool for analysing rotor performance. The BEM codes have very short processing times and high reliability. The problems of the analytical codes are well known to the researchers: the impossibility of describing inside the one-dimensional code the three-dimensional (3D) radial flows along the span-wise direction. In this work, the authors show how the 3D centrifugal pumping affects the BEM calculations of a wind turbine rotor. Actually to ascertain the accuracy of the analytical codes, the results are compared with rotor performance, blade loads and particle image... 

    Robustness investigation of the linear multi-variable control technique for power management of DFIG wind turbines

    , Article International Journal of Advanced Mechatronic Systems ; Volume 5, Issue 1 , 2013 , Pages 37-46 ; 17568412 (ISSN) Emami, S. A ; Banazadeh, A ; Sharif University of Technology
    Variable speed wind turbines are widely used in the modern power industry. These turbines that are usually driven by doubly fed induction generators (DFIGs) contain two groups of controlling variables; mechanical variables like pitch angle and electrical variables like rotor voltage. During the turbine operation, with variable wind velocity, power must be managed in two regimes; power optimisation and power limitation. In the current research, initially a non-linear simulation, based on the general wind turbine dynamic model is presented. Then, the desired controllers for both pitch angle and generator voltage components are constructed. After designing the controller, in order to... 

    A Pareto optimal multi-objective optimization for a horizontal axis wind turbine blade airfoil sections utilizing exergy analysis and neural networks

    , Article Journal of Wind Engineering and Industrial Aerodynamics ; Volume 136 , January , 2015 , Pages 62-72 ; 01676105 (ISSN) Mortazavi, S. M ; Soltani, M. R ; Motieyan, H ; Sharif University of Technology
    Elsevier  2015
    In this study a multi-objective genetic algorithm is utilized to obtain a Pareto optimal set of solutions for geometrical characteristics of airfoil sections for 10-meter blades of a horizontal axis wind turbine. The performance of the airfoil sections during the process of energy conversion is evaluated deploying a 2D incompressible unsteady CFD solver and the second law analysis. Artificial neural networks are trained employing CFD obtained data sets to represent objective functions in an algorithm which implements exergetic performance and integrity characteristics as optimization objectives. The results show that utilizing the second law approach along with Pareto optimality concept... 

    Starting improvement of micro-wind turbines operating in low wind speed regions

    , Article International Journal of Green Energy ; Volume 14, Issue 11 , 2017 , Pages 868-877 ; 15435075 (ISSN) Amir Nazmi Afshar, P ; Gooya, M ; Hosseini, S. V ; Pourrajabian, A ; Sharif University of Technology
    The study deals with the design and optimization of external and internal geometry of micro-wind turbines blades. A specified objective function which consists of the power coefficient and the starting time was defined and the genetic algorithm optimization technique in conjunction with the blade-element momentum theory was adopted to find the geometry of the blades including the distributions of the chord, the twist angle and also the shell thickness. Moreover, the allowable stress of the blades was considered as a constraint to the objective function. Results show that a reasonable compromise is achievable such that the starting time of the blades reduces noticeably in return for a small... 

    Power improvement of NREL 5-MW wind turbine using multi-DBD plasma actuators

    , Article Energy Conversion and Management ; Volume 146 , 2017 , Pages 96-106 ; 01968904 (ISSN) Ebrahimi, A ; Movahhedi, M ; Sharif University of Technology
    Elsevier Ltd  2017
    The present study numerically investigates the feasibility of using multiple dielectric barrier discharge (multi-DBD) plasma actuators as a novel approach for active flow control over a large horizontal axis wind turbine rotor. The National Renewable Energy Laboratory 5 MW offshore wind turbine is used as the baseline case. This turbine uses pitch control system to adjust the generated power above its rated wind speeds, but at lower speeds, this system remains inactive. In this paper, the operational condition speed is considered lower than the rated wind speed. The mathematical electro-static model is implemented to simulate the effects of plasma actuator on the external flow and the... 

    Experimental study on gyroscopic effect of rotating rotor and wind heading angle on floating wind turbine responses

    , Article International Journal of Environmental Science and Technology ; Volume 15, Issue 12 , 2018 , Pages 2531-2544 ; 17351472 (ISSN) Bahramiasl, S ; Abbaspour, M ; Karimirad, M ; Sharif University of Technology
    Limited fossil resources, daily increasing rate of demand for energy and the environmental pollution fact have made people revert to renewable sources of energy as a solution. One type of renewable energy is offshore wind energy which has high potential without any sound and visual noises. Recently, a lot of researchers have carried out on the issue of offshore wind turbine. Because of incapability of most of software programs to simulate gyroscopic effect of rotating rotors, in this articles a significant effort has been made to fabricate and test an offshore wind turbine under different rotor rotation velocities and different heading angle of wind so as to obtain the effects of these... 

    Aeroelastic modeling and dynamic analysis of a wind turbine rotor by considering geometric nonlinearities

    , Article Journal of Sound and Vibration ; Volume 432 , 2018 , Pages 653-679 ; 0022460X (ISSN) Rezaei, M. M ; Zohoor, H ; Haddadpour, H ; Sharif University of Technology
    Academic Press  2018
    Due to the increased flexibility of modern multi-megawatt wind turbine structures, more advanced analyses are needed to investigate the effects of geometric nonlinearities originating from large blade deformations under operational loads. The main objective of this paper is to study the related dynamics and the aeroelastic effects of these nonlinearities by using a multi-flexible-body aeroelastic model of an entire three-bladed wind turbine assembly instead of a more conventional single-blade model. A geometrically-exact beam formulation is employed to model the rotating blades connected to the wind turbine tower tip via hub and nacelle components; and the revolute joint constraint is... 

    Smooth switching in power control of wind turbines using a combination strategy of hysteresis and modified middle regions

    , Article Sustainable Energy Technologies and Assessments ; Volume 37 , 2020 Nouriani, A ; Moradi, H ; Sharif University of Technology
    Elsevier Ltd  2020
    This paper presents a new method for protecting the variable speed wind turbines in switching between different regions. With the objective of power maximization, the controller is applied in all regions. Since usually different methods and algorithms are used in different regions for controlling the wind turbines, smooth transition between these controllers is necessary for the safety and protection of turbine parts and structure. A two degree of freedom mechanical model is used and the simulations are performed and verified by FAST. The turbine is controlled by a rotor angular speed controller in the second region and an inverse dynamic pitch controller in the third region. The transient... 

    Modeling and control of variable speed wind turbine generators for frequency regulation

    , Article IEEE Transactions on Sustainable Energy ; Volume 11, Issue 2 , 2020 , Pages 916-927 Ravanji, M. H ; Canizares, C. A ; Parniani, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    Wind turbine generators (WTG) can participate in system frequency regulation via virtual inertial controllers (VIC). In the presence of frequency disturbances, VIC temporarily regulates the WTG power output forcing it to release/absorb kinetic energy into/from the grid. With increasing penetration of WTGs in power systems, grid operators require these generators to provide frequency regulation services; however, kinetic energy release/absorption can destabilize WTGs. Hence, to address these issues, a new large-perturbation nonlinear WTG model is proposed in this paper, based on the WTG internal response that is used to tune typical VICs. Novel worst case and optimal VIC tuning approaches are... 

    Experimental investigation of velocity profiles in the wake of an oscillating airfoil

    , Article 2007 5th Joint ASME/JSME Fluids Engineering Summer Conference, FEDSM 2007, San Diego, CA, 30 July 2007 through 2 August 2007 ; Volume 1 SYMPOSIA, Issue PART B , August , 2007 , Pages 1873-1882 ; 0791842886 (ISBN); 9780791842881 (ISBN) Soltani, M. R ; Mahmoudi, M ; Sharif University of Technology
    A series of experiments were carried out to study the unsteady wakes behind an oscillating airfoil. The airfoil is a section of a wind turbine blade oscillating in pitch about the quarter chord axis at various reduced frequencies, oscillation amplitude and mean angles of attack. Real time velocity profiles were obtained using total and static pressure at 35 vertically aligned points behind the airfoil via two similar rakes. The rakes were located at a distance of 1.5 chord length behind the model. The results show great influence of oscillation amplitude and reduced frequency on the wake velocity profiles. Copyright © 2007 by ASME  

    Effect of plunging amplitude on the performance of a wind turbine blade section

    , Article Aeronautical Journal ; Volume 111, Issue 1123 , 2007 , Pages 571-588 ; 00019240 (ISSN) Soltani, M. R ; Marzabadi, F. R ; Sharif University of Technology
    Royal Aeronautical Society  2007
    Extensive low speed wind-tunnel tests were conducted to study the unsteady aerodynamic behaviour of an airfoil sinusoidally oscillating in plunge. The experiments involved measuring the surface pressure distribution over a range of amplitudes, H = ±5 to ±15cm. In addition, steady state data were acquired and were used to furnish a baseline for further analysis and comparison. The model was oscillated with a constant reduced frequency, k = 0.058, at three mean angles of attack of 0°, 10° and 18°. The unsteady aerodynamic loads were calculated from the surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces of the model. The plunging displacements were... 

    Seawater desalination via waste heat recovery from generator of wind turbines: How economical is it to use a hybrid hdh-ro unit?

    , Article Sustainability (Switzerland) ; Volume 13, Issue 14 , 2021 ; 20711050 (ISSN) Rostamzadeh, H ; Rostami, S ; Amidpour, M ; He, W ; Han, D ; Sharif University of Technology
    MDPI AG  2021
    Over recent years, the concept of waste heat recovery from the generators of wind turbines for driving a thermal-driven desalination system was introduced, and its advantages were highlighted. However, any selection of a bottoming thermal-driven desalination system among different existing technologies should be taken under consideration before making an ultimate recommendation. Unfortunately, no comprehensive comparison is available in the literature to compare the performance as well as the cost aspects of using the waste thermal energy of the generator of a wind turbine for desalinating seawater, comparing them with those of a layout where the power of the wind turbine is directly... 

    Transient response of the flexible blade of horizontal-axis wind turbines in wind gusts and rapid yaw changes

    , Article Energy ; Volume 145 , 2018 , Pages 261-275 ; 03605442 (ISSN) Ebrahimi, A ; Sekandari, M ; Sharif University of Technology
    Elsevier Ltd  2018
    In this paper, the aeroelastic analysis of a large scale wind turbine rotor is performed with the aim of studying transient performance of turbine in extreme wind conditions, such as wind gusts and rapid yaw changes. The effect of the presence and/or lack of blade pitch control system on output power, rotor thrust, and blade deformation in sudden change of wind speed are investigated. The NREL 5 MW offshore wind turbine is used as the baseline case. In this regard, the modal approach is implemented for modeling the flexible blade structure with tension, bending and torsion degrees of freedom. The unsteady vortex lattice method is employed to obtain the aerodynamic loads. Moreover, the... 

    Proposal of a Modular Structure and a Load Sharing Strategy among Back to Back Converters for Wind Turbines

    , M.Sc. Thesis Sharif University of Technology Amouzegar Ashtiani, Nima (Author) ; Mokhtari, Hossein (Supervisor)
    The utilization of wind power has been increasing in recent years which lead to enhance the the usage of wind power capacity in the range of MegaWatt. However, due to the limitation ofswitching devices capacity, which exists in power electronic converters, improving the capacity of wind power generation is not accessible. Thus, a feasible solution for this problem is paralleling power electronics converters, which increases both the capacity of power generation and the reliability of wind turbine systems. Nevertheless, paralleling converters may cause a circulating-current which brings current discrepancy, current waveform distortion, power losses, increase in THD of currents, and reduction... 

    Dynamic Analysis of Floating Offshore Wind Turbines

    , M.Sc. Thesis Sharif University of Technology Imani, Hassan (Author) ; Abbaspour Tehrani Fard, Madjid (Supervisor)
    Use of wind energy is always one of the aims of man during the times. He used this energy for wheat grinding and sometimes for marine transportations. During recent decades, technology development forced human to harness this energy and use that for electricity production by employing onshore wind turbines. However, the modern engineering employed different arms of engineering such as marine engineering, civil engineering, mechanical engineering and electrical engineering for designing and installation of offshore wind turbines. But, huge water depths in offshore regions make the fixed leg turbines to be unacceptable solution. So, the floating wind turbines with mooring lines which attach... 

    Developing a model for integrating decisions in technology roadmapping by fuzzy PROMETHEE

    , Article Journal of Intelligent and Fuzzy Systems ; Volume 26, Issue 2 , 2014 , Pages 625-645 ; ISSN: 10641246 Ghazinoory, S ; Daneshmand Mehr, M ; Arasti, M. R ; Sharif University of Technology
    Roadmapping, a tool of strategic planning, visualize where and how an organization will be in the future. Visualization of strategic programs assists people in the organization to understand the strategy which is a key for implementing strategy successfully. A generic roadmap is included of three main layers such as; market, product and technology. Decision making in each layer are done separately because of the nature of each layer. Therefore, decisions in roadmapping can be done with different tools. Whiles, decisions in each layer of the roadmap cannot be done without considering the upper or lower layer decisions. In this study we propose Fuzzy PROMETHEE method for integrating decisions... 

    New strategy for optimization of output power of a DFIG wind turbine

    , Article International Aegean Conference on Electrical Machines and Power Electronics, ACEMP 2011 and Electromotion 2011 Joint Conference ; Sept , 2013 , Pages 69-72 ; 9781467350037 (ISBN) Abedinzadeh, T ; Ehsan, M ; Afsharirad, H ; Nazaraliloo, M ; Sharif University of Technology
    This paper presents a method to maximize the output power of a DFIG wind turbine. In this method, an optimization technique based on mathematical analysis has been used. The modeling of DFIG is performed using MATLAB. To evaluate the maximum output power of a DFIG, detailed expressions for output power and losses are derived as functions of generator slip, the magnitude and phase angle of rotor excitation voltage in various wind velocities. The outcomes of this method demonstrate that maximum output power of a DFIG wind turbine do not happen in the maximum input power (the mechanical power of wind turbine)  

    Dynamic modeling of a wind turbine with brushless doubly fed induction generator

    , Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 490-494 ; 9781467301114 (ISBN) Tohidi, S ; Zolghadri, M. R ; Oraee, H ; Oraee, A ; Sharif University of Technology
    Brushless Doubly Fed Induction Generator (BDFIG) has been recently proposed to be used in variable speed wind turbines. This paper intends to investigate the influence of certain model simplifications to obtain a reduced-order model of a wind turbine with BDFIG suitable for transient studies. To achieve this goal, small signal analysis is performed for a recently manufactured 250 kVA BDFIG to obtain system modes and their participation factors. Identifying highly damped modes, influences of neglecting dynamics of their participated states are studied through time-domain simulation in MATLAB/Simulink  

    Reliability comparison of direct-drive and geared-drive wind turbine concepts

    , Article Wind Energy ; Volume 13, Issue 1 , 2010 , Pages 62-73 ; 10954244 (ISSN) Arabian Hoseynabadi, H ; Tavner, P. J ; Oraee, H ; Sharif University of Technology
    This paper proposes for wind turbines (WTs) an analytical reliability method, used on other engineering systems, to compare the reliability of different turbine concepts. The main focus of the paper is to compare the reliability of geared generator and direct-drive concept WTs. Modification methods are also recommended for improving the availability of WTs and geared generator concept incorporating doubly fed induction generator