Dissertations / Theses on the topic 'Wind turbines – Automatic control'
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1
Rodríguez, D'Derlée Johel José. "Control strategies for offshore wind farms based on PMSG wind turbines and HVdc connection with uncontrolled rectifier." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/34510.
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The selection of the bulk power transmission technology in offshore wind
farms is strongly related to the wind farm size and its distance to shore.
Several alternatives can be evaluated depending on the rated power of the
offshore wind farm, the transmission losses and the investment cost for
constructing the transmission system. However, when is necessary to
connect larger and more distant offshore wind farms; the best
technological solution tends to the transmission system based on highvoltage
and direct-current with line commutated converters (LCC-HVdc).
This dissertation proposes the use of diode-based rectifers as a technical
alternative to replace the thyristor-based rectifers in an LCC-HVdc link with
unidirectional power flow. This alternative shows advantages with regard
to lower conduction losses, lower installation costs and higher reliability.
Nonetheless, as a counterpart the offshore ac-grid control performed by
the thyristor-based HVdc rectifer is no longer available. This lack of control
is compensated by using new control strategies over an offshore wind
farm composed by wind turbines with permanent-magnet generators and
fully-rated converters. The control strategies have been based mainly on
the ability of the wind turbine grid-side converter to perform the control of
the offshore ac-grid voltage and frequency. The performance has been
evaluated by using PSCAD. Wherein, the most common grid disturbances
have been used to demonstrate the fault-ride-through capability as well as
the adequate steady state and transient response.Rodríguez D'derlée, JJ. (2013). Control strategies for offshore wind farms based on PMSG wind turbines and HVdc connection with uncontrolled rectifier [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34510
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Santos, Richard A. "Damage mitigating control for wind turbines." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256394.
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Tong, Xin. "Control of large offshore wind turbines." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/99841/.
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Several control strategies are proposed to improve overall performances of conventional (geared equipped) and hydrostatic offshore wind turbines. Firstly, to maximise energy capture of a conventional turbine, an adaptive torque control technique is proposed through simplifying the conventional extremum seeking control algorithm. Simulations are conducted on the popular National Renewable Energy Laboratory (NREL) monopile 5-MW baseline turbine. The results demonstrate that the simplified ESC algorithms are quite effective in maximising power generation. Secondly, a TMD (tuned mass damper) system is configured to mitigate loads on a monopile turbine tower whose vibrations are typically dominated by its first mode. TMD parameters are obtained via H2 optimisation based on a spatially discretised tower-TMD model. The optimal TMDs are assessed through simulations using the NREL monopile 5-MW baseline model and achieve substantial tower load reductions. In some cases it is necessary to damp tower vibrations induced by multiple modes and it is well-known that a single TMD is lack of robustness. Thus a control strategy is developed to suppress wind turbine’s vibrations (due to multiple modes) using multiple groups of TMDs. The simulation studies demonstrate the superiority of the proposed methods over traditional ones. Thirdly, the NREL 5-MW baseline turbine model is transformed into a hydrostatic wind turbine (HWT). An H∞ loop-shaping torque controller and a light detection and ranging-based linear-parameter-varying anti-windup pitch controller are designed for the HWT. The tests on a monopile HWT model indicate good tracking behaviours of the torque controller and much improved performances of the linear-parameter-varying pitch controller over a gain-scheduled PI pitch controller. Finally, the hydraulic reservoir of a barge HWT is made into a bidirectional-tuned- liquid-column-damper (BTLCD) to suppress barge pitch and roll motions. The simulation results validate the effectiveness of the optimal BTLCD reservoir in reducing the tower loads and power fluctuations.
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Lee, Donghoon. "Multi-flexible-body analysis for applications to wind turbine control design." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04052004-180040/unrestricted/lee%5Fdonghoon%5F200312%5Fphd.pdf.
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Fégeant, Olivier. "Noise from wind turbines /." Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3100.
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Lindeberg, Eivind. "Optimal Control of Floating Offshore Wind Turbines." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9933.
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Floating Offshore Wind Power is an emerging and promising technology that is particularly interesting from a Norwegian point of view because of our long and windy coast. There are however still several remaining challenges with this technology and one of them is a possible stability problem due to positive feedback from tilt motion of the turbine tower. The focus of this report is to develope a simulator for a floating offshore wind turbine that includes individual, vibrating blades. Several controllers are developed, aiming to use the blade pitch angle and the generator power to control the turbine speed and output power, while at the same time limit the low-frequent motions of the tower and the high-frequent motions of the turbine blades. The prime effort is placed on developing a solution using Model Predictive Control(MPC). On the issue of blade vibrations no great progress has been made. It is not possible to conclude from the simulation results that the designed controllers are able to reduce the blade vibrations. However, the MPC controller works very well for the entire operating range of the turbine. A "fuzzy"-inspired switching algorithm is developed and this handles the transitions between the different operating ranges of the turbine convincingly. The problem of positive feedback from the tower motion is handled well, and the simulations do not indicate that this issue should jeopardize the viability of floating offshore wind turbines.
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Cantoni, Lorenzo. "Load Control Aerodynamics in Offshore Wind Turbines." Thesis, KTH, Kraft- och värmeteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291417.
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Due to the increase of rotor size in horizontal axis wind turbine (HAWT) during the past 25 years in order to achieve higher power output, all wind turbine components and blades in particular, have to withstand higher structural loads. This upscalingproblem could be solved by applying technologies capable of reducing aerodynamic loads the rotor has to withstand, either with passive or active control solutions. These control devices and techniques can reduce the fatigue load upon the blades up to 40% and therefore less maintenance is needed, resulting in an important money savings for the wind farm manager. This project consists in a study of load control techniques for offshore wind turbines from an aerodynamic and aeroelastic point ofview, with the aim to assess a cost effective, robust and reliable solution which could operate maintenance free in quite hostile environments. The first part of this study involves 2D and 3D aerodynamic and aeroelastic simulations to validate the computational model with experimental data and to analyze the interaction between the fluid and the structure. The second part of this study is an assessment of the unsteady aerodynamic loads produced by a wind gust over the blades and to verify how a trailing edge flap would influence the aerodynamic control parameters for the selected wind turbine blade.På grund av ökningen av rotorstorleken hos horisontella vindturbiner (HAWT) under de senaste 25 åren, en design som har uppstod för att uppnå högre effekt, måste alla vindkraftkomponenter och blad stå emot högre strukturella belastningar. Detta uppskalningsproblem kan lösas genom att använda metoder som kan minska aerodynamiska belastningar som rotorn måste tåla, antingen med passiva eller aktiva styrlösningar. Dessa kontrollanordningar och tekniker kan minska utmattningsbelastningen på bladen med upp till 40 % och därför behövs mindre underhåll, vilket resulterar i viktiga besparingar för vindkraftsägaren. Detta projekt består av en studie av lastkontrolltekniker för havsbaserade vindkraftverk ur en aerodynamisk och aeroelastisk synvinkel, i syfte att bedöma en kostnadseffektiv, robust och pålitlig lösning som kan fungera underhållsfri i tuffa miljöer. Den första delen av denna studie involverar 2D- och 3D-aerodynamiska och aeroelastiska simuleringar för att validera beräkningsmodellen med experimentella data och för att analysera interaktionen mellan fluiden och strukturen. Den andra delen av denna studie är en bedömning av de ojämna aerodynamiska belastningarna som produceras av ett vindkast över bladen och för att verifiera hur en bakkantklaff skulle påverka de aerodynamiska styrparametrarna för det valda vindturbinbladet.
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Goodfellow, David. "Variable speed operation of wind turbines." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/7822.
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This work describes a control system in which a cycloconverter is connected between the secondary windings of a three phase induction machine and the a. c. mains supply to give variable speed sub- and super –synchronously. In order to control the system smoothly in an asynchronous mode a secondary emf signal generator has been designed, which enables the cycloconverter to operate in synchronism with the emf induced in the secondary windings of the machine. A computer programme has been written which calculates the required firing angles for the cycloconverter to produce secondary current in phase with the secondary emf in the machine. An electronic system has been built which ensures that these firing angles are used by the cycloconverter during actual operation. A cycloconverter has been built, using an effective six phases of mains supply, and has been successfully operated over a range of 20% about synchronous speed in both generating and motoring modes. Results show the ability of the cycloconverter to drive the machine up from standstill as a motor to just below 20% subsynchronous speed. An on-line computer simulation of a wind turbine has been developed which enables an assessment of variable speed generation applied to wind turbines to be achieved. This simulation, in connection with a d. c. machine and thyristor controller, can be used to drive the shaft of the induction machine and assess operation of the cycloconverter control scheme under actual wind turbine operating conditions.
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Momsen, Timothy Benjamin. "Hybrid additive manufacturing platform for the production of composite wind turbine blade moulds." Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/19091.
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This dissertation discusses the application of additive manufacturing technologies for production of a large-scale rapid prototyping machine, which will be used to produce moulds for prototype composite turbine blades for the emerging renewables energy industry within the Eastern Cape region in South Africa. The conceptualization and design of three complete printer builds resulted in the amalgamation of a final system, following stringent theoretical design, simulation, and feasibility analysis. Following the initial product design cycle stage, construction and performance testing of a large-scale additive manufacturing platform were performed. In-depth statistical analysis of the mechatronic system was undertaken, particularly related to print-head locational accuracy, repeatability, and effects of parameter variation on printer performance. The machine was analysed to assess feasibility for use in the mould-making industry with accuracy and repeatability metrics of 0.121 mm and 0.156 mm rivalling those produced by some of the more accurate fused deposition modellers commercially available. The research data gathered serves to confirm that rapid prototyping is a good alternative manufacturing method for wind turbine blade plug and mould production.
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Feng, Xiaoran. "Predictive control approaches to fault tolerant control of wind turbines." Thesis, University of Hull, 2014. http://hydra.hull.ac.uk/resources/hull:10517.
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This thesis focuses on active fault tolerant control (AFTC) of wind turbine systems. Faults in wind turbine systems can be in the form of sensor faults, actuator faults, or component faults. These faults can occur in different locations, such as the wind speed sensor, the generator system, drive train system or pitch system. In this thesis, some AFTC schemes are proposed for wind turbine faults in the above locations. Model predictive control (MPC) is used in these schemes to design the wind turbine controller such that system constraints and dual control goals of the wind turbine are considered. In order to deal with the nonlinearity in the turbine model, MPC is combined with Takagi-Sugeno (T-S) fuzzy modelling. Different fault diagnosis methods are also proposed in different AFTC schemes to isolate or estimate wind turbine faults. The main contributions of the thesis are summarized as follows: A new effective wind speed (EWS) estimation method via least-squares support vector machines (LSSVM) is proposed. Measurements from the wind turbine rotor speed sensor and the generator speed sensor are utilized by LSSVM to estimate the EWS. Following the EWS estimation, a wind speed sensor fault isolation scheme via LSSVM is proposed. A robust predictive controller is designed to consider the EWS estimation error. This predictive controller serves as the baseline controller for the wind turbine system operating in the region below rated wind speed. T-S fuzzy MPC combining MPC and T-S fuzzy modelling is proposed to design the wind turbine controller. MPC can deal with wind turbine system constraints externally. On the other hand, T-S fuzzy modelling can approximate the nonlinear wind turbine system with a linear time varying (LTV) model such that controller design can be based on this LTV model. Therefore, the advantages of MPC and T-S fuzzy modelling are both preserved in the proposed T-S fuzzy MPC. A T-S fuzzy observer, based on online eigenvalue assignment, is proposed as the sensor fault isolation scheme for the wind turbine system. In this approach, the fuzzy observer is proposed to deal with the nonlinearity in the wind turbine system and estimate system states. Furthermore, the residual signal generated from this fuzzy observer is used to isolate the faulty sensor. A sensor fault diagnosis strategy utilizing both analytical and hardware redundancies is proposed for wind turbine systems. This approach is proposed due to the fact that in the real application scenario, both analytical and hardware redundancies of wind turbines are available for designing AFTC systems. An actuator fault estimation method based on moving horizon estimation (MHE) is proposed for wind turbine systems. The estimated fault by MHE is then compensated by a T-S fuzzy predictive controller. The fault estimation unit and the T-S fuzzy predictive controller are combined to form an AFTC scheme for wind turbine actuator faults.
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Polverini, Silvia. "Analysis and control of floating offshore wind turbines." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13883/.
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With the continuous growing of wind energy as a clean source for electricity production there is an increasing interest in the location of wind turbines in offshore areas in which there are fewer space restrictions and less turbulent wind. This increases the interest to develop floating wind turbines, which are not mounted in the sea-bed and can be used in deep waters. For their low environmental impact, the demand for FOWTs could easily be fostered.
Floating turbines are large and complex mechanical structures as a consequence it is necessary to adapt control strategies to these systems, to ensure acceptable loads in order to guarantee a long lifetime.
In order to reduce fatigue loads, different design control approaches are studied.
To design the control, simplified models are needed.
The purpose of this thesis is to develop a simplified Floating Offshore Wind Turbine (FOWT) model considering aero-dynamical loads to assess the performance of the system.
The aerodynamic forces are derived and implemented in a more accurate simulator, FAST, to evaluate the overall loads acting on a FOWT. FAST is the acronym for Fatigue-Aerodynamics-Structure-Turbulence and it gives a full analysis of wind turbine models, using a high-fidelity numerical code.
The developed FAST computer program simulator is applied to investigate the reliability of simplistic wind turbine models by using MATLAB and Simulink interfaces.
Studying a simplification of the turbine model means identify the dominant physical dynamics behaviour that implies a good knowledge of wind turbine dynamics.
The simplified model is useful when a linear control theory is applied.
Due to the non-linearity of the problem, created by wind and sea kinematics, specific values are found using an empirical approach. Results are acceptable according to the approximations done.
Further developments are considered to obtain a more detailed model of wind turbine and changes to control strategy.
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Gase, Zachary M. "Below-Rated Control of Swept-Blade Wind Turbines." Scholarly Commons, 2016. https://scholarlycommons.pacific.edu/uop_etds/225.
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Modelling studies have shown that 1.5 and 3.0 MW wind turbines with blade sweep have an increased annual energy production (AEP) of approximately 5% when compared to straight-blade wind turbines. The objective of the research was to further increase below-rated, variable speed, power capture when using swept-blades. When operating in the variable speed region, the turbine’s torque is proportional to the square of the generator speed, and k is the proportionality constant (T = kΩ 2 ). Initial studies indicated that the value of k needed to be lowered from the original value to increase AEP. This proved to be slightly beneficial for the 3.0 MW turbine but not for the 1.5 MW turbine. The optimal tip speed ratio was too high for both turbines and limited the ability to increase AEP. Original swept-blade chords were designed to fit a linear pattern for manufacturing purposes, but it is believed this is no longer a necessary constraint. The blades were redesigned to have a non-linear chord distribution, which is based on the Betz optimal design method, and the resultant increase in solidity proved to be the solution for slowing down the blades’ rotational speed. The change in chord design proved to be beneficial for both 1.5 and 3.0 MW wind turbines and had immediate, measurable increases to AEP. An effort to further increase AEP was then conducted by using an alternative torque-speed controller, which used a different equation to relate speed and torque. This method only resulted in an increase of AEP for the 1.5 MW turbine. In conclusion, the highest recorded AEP increases from straight-blade values were 6.9% and 8.9% for the 1.5 and 3.0 MW turbines, respectively. The 1.5 MW turbine benefited from the custom controller and redesigned chords, whereas the 3.0 MW turbine only benefited from redesigned chords.
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Stock, Adam. "Augmented control for flexible operation of wind turbines." Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25253.
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In this thesis a novel controller for providing greater flexibility of operation of wind turbines known as the Power Adjusting Controller (PAC) is presented. The controller takes the form of an augmentation to a wind turbine's full envelope controller, allowing it to be applied to any horizontal axis, pitch regulated, variable speed wind turbine. Conventional wind turbine control seeks to maximise the power output of a wind turbine whilst minimising the loads on the turbine, controlling on the error in generator speed via demands to the blade pitch actuator and generator torque actuator. The PAC uses additions to the full envelope controller inputs and outputs to alter the power output of the turbine by an additional input value ∆P. It is ensured that the operation of the full envelope controller is not compromised by the PAC. Testing of the PAC using lumped parameter models of wind turbines and full aero-elastic models makes clear a requirement for a wind speed estimator within the PAC that incorporates the effects of dynamic inflow. A novel wind speed estimator that accounts for dynamic inflow by redefining blade element momentum theory solely in terms of the dynamics at the rotor is therefore developed and incorporated into the PAC. Limits are designed to ensure that the operating point of a wind turbine with the PAC is kept within a safe operational envelope, and a system of flags and sub-flags is developed to allow easy integration of the PAC into a hierarchical wind farm control structure. The effect of using the PAC on the wind turbine loads is investigated, with the ultimate loads introduced by operation of the PAC found to be within the range of normal operating loads and the impact of prolonged reduction of the power output found to reduce the lifetime damage equivalent loads in most cases.
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Dadashnialehi, Ehsan. "Modeling And Control of Variable Speed Wind Turbines." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1356372607.
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Trevelyan, Conrad. "Application of circulation control aerofoils to wind turbines." Thesis, Loughborough University, 2002. https://dspace.lboro.ac.uk/2134/34575.
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Circulation control aerofoils potentially offer an additional means of load and power control for horizontal axis wind turbines by virtue of their rapid response time. Their suitability for these tasks has been assessed with respect to the power which they absorb, their interaction with aerofoils used on modern wind turbines, the infrastructure or hardware which they require and the degree to which they can affect the loads experienced by the turbine blades and other major components. It has been determined that the type of circulation control aerofoil most suited to use on wind turbine blades are those of the jet flap type and it has been realised that an ability to shed, as well as increase loads is advantageous in this application. To this end the behaviour of both negatively and positively deflected jets have been investigated with a two-dimensional computational fluid dynamics code, validated in the course of this work for such modelling. Particular emphasis has been placed on minimising the input power requirements of the circulation control aerofoils and in proposing an overall system that has the required level of robustness and reliability. A 2MW turbine has been modelled with a blade element momentum theory code in order to compare performance with and without circulation control aerofoils. These initial results show that there may be some positive benefits to be gained, but that the energy demands of the system place a hard limit on the degree to which circulation control aerofoils can determine the forces experienced by the turbine.
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Zhang, Zijun. "Performance optimization of wind turbines." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3024.
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Improving performance of wind turbines through effective control strategies to reduce the power generation cost is highly desired by the wind industry. The majority of the literature on performance of wind turbines has focused on models derived from principles versed in physics. Physics-based models are usually complex and not accurate due to the fact that wind turbines involve mechanical, electrical, and software components. These components interact with each other and are subjected to variable loads introduced by the wind as well as the rotating elements of the wind turbine. Recent advances in data acquisition systems allow collection of large volumes of wind energy data. Although the prime purpose of data collection is monitoring conditions of wind turbines, the collected data offers a golden opportunity to address most challenging issues of wind turbine systems. In this dissertation, data mining is applied to construct accurate models based on the turbine collected data. To solve the data-driven models, evolutionary computation algorithms are applied. As data-driven based models are non-parametric, the evolutionary computation approach makes an ideal solution tool. Optimizing wind turbines with different objectives is studied to accomplish different research goals. Two research directions of wind turbines performance are pursued, optimizing a wind turbine performance and optimizing a wind farm performance. The goal of single wind turbine optimization is to improve wind turbine efficiency and its life-cycle. The performance optimization of a wind farm is to minimize the total cost of operating a wind farm based on the computed turbine scheduling strategies. The methodology presented in the dissertation is applicable to processes besides wind industry.
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Högberg, Lars. "Automated electric control of a vertical axis wind turbine in island operation." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-162559.
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At the Division of Electricity at Uppsala University, a wind power concept has been developed. The concept uses a vertical axis wind turbine with a direct driven generator. The turbine has fixed blades, making speed control the only way to regulate power absorption. The speed is controlled with the electric load. The turbine is not self-starting, but can be started using the generator as a motor. In this project, an unsupervised electric system with automatic control is designed and constructed. The starting point is a detailed study of the earlier developed control system. To be able to select the rating of the components, theoretical calculations are done. Simulations in MATLAB are performed to predict the behavior of the system. The resulting system is a working prototype in operation outside of Uppsala. The system starts the turbine using a new start-up strategy. Loading of the generator is controlled by primarily supplying a regular consumer with direct current and secondly dissipating additional power as heat. A circuit stopping the turbine, in case of different failures, is included in the system.
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Massey, Jason G. "Doubly fed induction machine control for wind energy conversion." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://handle.dtic.mil/100.2/ADA501680.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2009.Thesis Advisor(s): Julian, Alexander L. "June 2009." Description based on title screen as viewed on July 10, 2009. DTIC Identifiers: Wind energy conversion system, DFIG (Double Fed Induction Generator), VSI (Voltage Source Inverter), SVM (Space Vector Modulation), wind turbine, FPGA (Field Programmable Gate Array). Author(s) subject terms: Double Fed Induction Generator (DFIG), Voltage Source Inverter (VSI), Space Vector Modulation (SVM), Wind Turbine, Field Programmable Gate Array (FPGA), Wind Energy Conversion System. Includes bibliographical references (p. 91). Also available in print.
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Simley, Eric J. "Wind Speed Preview Measurement and Estimation for Feedforward Control of Wind Turbines." Thesis, University of Colorado at Boulder, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3721887.
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Wind turbines typically rely on feedback controllers to maximize power capture in below-rated conditions and regulate rotor speed during above-rated operation. However, measurements of the approaching wind provided by Light Detection and Ranging (lidar) can be used as part of a preview-based, or feedforward, control system in order to improve rotor speed regulation and reduce structural loads. But the effectiveness of preview-based control depends on how accurately lidar can measure the wind that will interact with the turbine.
In this thesis, lidar measurement error is determined using a statistical frequency-domain wind field model including wind evolution, or the change in turbulent wind speeds between the time they are measured and when they reach the turbine. Parameters of the National Renewable Energy Laboratory (NREL) 5-MW reference turbine model are used to determine measurement error for a hub-mounted circularly-scanning lidar scenario, based on commercially-available technology, designed to estimate rotor effective uniform and shear wind speed components. By combining the wind field model, lidar model, and turbine parameters, the optimal lidar scan radius and preview distance that yield the minimum mean square measurement error, as well as the resulting minimum achievable error, are found for a variety of wind conditions. With optimized scan scenarios, it is found that relatively low measurement error can be achieved, but the attainable measurement error largely depends on the wind conditions. In addition, the impact of the induction zone, the region upstream of the turbine where the approaching wind speeds are reduced, as well as turbine yaw error on measurement quality is analyzed.
In order to minimize the mean square measurement error, an optimal measurement prefilter is employed, which depends on statistics of the correlation between the preview measurements and the wind that interacts with the turbine. However, because the wind speeds encountered by the turbine are unknown, a Kalman filter-based wind speed estimator is developed that relies on turbine sensor outputs. Using simulated lidar measurements in conjunction with wind speed estimator outputs based on aeroelastic simulations of the NREL 5-MW turbine model, it is shown how the optimal prefilter can adapt to varying degrees of measurement quality.
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Poole, Sean. "The development of a segmented variable pitch small horizontal axis wind turbine with active pitch control." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020583.
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Small scale wind turbines operating in an urban environment produce dismal amounts of power when compared to their expected output [1-4]. This is largely due to the gusty wind conditions found in an urban environment, coupled with the fact that the wind turbines are not designed for these conditions. A new concept of a Segmented Variable Pitch (SVP) wind turbine has been proposed, which has a strong possibility to perform well in gusty and variable wind conditions. This dissertation explains the concept of a SVP wind turbine in more detail and shows analytical and experimental results relating to this concept. Also, the potential benefits of the proposed concept are mentioned. The results from this dissertation show that this concept has potential with promising results on possible turbine blade aerofoil configurations. Scaled model tests were completed and although further design optimisation is required, the tests showed good potential for the SVP concept. Lastly a proof-of-concept full scale model was manufactured and tested to prove scalability to full size from concept models. Along with the proof-of-concept full scale model, a wireless control system (to control the blade segments) was developed and tested.
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Tutivén, Gálvez Christian. "Fault detection and fault tolerant control in wind turbines." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/663289.
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Renewable energy is an important sustainable energy in the world. Up to now, as an essential part of low emissions energy in a lot of countries, renewable energy has been important to the national energy security, and played a significant role in reducing carbon emissions. It comes from natural resources, such as wind, solar, rain, tides, biomass, and geothermal heat. Among them, wind energy is rapidly emerging as a low carbon, resource efficient, cost effective sustainable technology in the world. Due to the demand of higher power production installations with less environmental impacts, the continuous increase in size of wind turbines and the recently developed offshore (floating) technologies have led to new challenges in the wind turbine systems.Wind turbines (WTs) are complex systems with large flexible structures that work under very turbulent and unpredictable environmental conditions for a variable electrical grid. The maximization of wind energy conversion systems, load reduction strategies, mechanical fatigue minimization problems, costs per kilowatt hour reduction strategies, reliability matters, stability problems, and availability (sustainability) aspects demand the use of advanced (multivariable and multiobjective) cooperative control systems to regulate variables such as pitch, torque, power, rotor speed, power factors of every wind turbine, etc. Meanwhile, with increasing demands for efficiency and product quality and progressing integration of automatic control systems in high-cost and safety-critical processes, the fields of fault detection and isolation (FDI) and fault tolerant control (FTC) play an important role. This thesis covers the theoretical development and also the implementation of different FDI and FTC techniques in WTs. The purpose of wind turbine FDI systems is to detect and locate degradations and failures in the operation of WT components as early as possible, so that maintenance operations can be performed in due time (e.g., during time periods with low wind speed). Therefore, the number of costly corrective maintenance actions can be reduced and consequently the loss of wind power production due to maintenance operations is minimized. The objective of FTC is to design appropriate controllers such that the resulting closed-loop system can tolerate abnormal operations of specific control components and retain overall system stability with acceptable system performance. Different FDI and FTC contributions are presented in this thesis and published in different JCR-indexed journals and international conference proceedings. These contributions embrace a wide range of realistic WTs faults as well as different WTs types (onshore, fixed offshore, and floating). In the first main contribution, the normalized gradient method is used to estimate the pitch actuator parameters to be able to detect faults in it. In this case, an onshore WT is used for the simulations. Second contribution involves not only to detect faults but also to isolate them in the pitch actuator system. To achieve this, a discrete-time domain disturbance compensator with a controller to detect and isolate pitch actuator faults is designed. Third main contribution designs a super-twisting controller by using feedback of the fore-aft and side-to-side acceleration signals of the WT tower to provide fault tolerance capabilities to the WT and improve the overall performance of the system. In this instance, a fixed-jacket offshore WT is used. Throughout the aforementioned research, it was observed that some faults induce to saturation of the control signal leading to system instability. To preclude that problem, the fourth contribution of this thesis designs a dynamic reference trajectory based on hysteresis. Finally, the fifth and last contribution is related to floating-barge WTs and the challenges that this WTs face. The performance of the proposed contributions are tested in simulations with the aero-elastic code FAST.La energía renovable es una energía sustentable importante en el mundo. Hasta ahora, como parte esencial de la energía de bajas emisiones en muchos países, la energía renovable ha sido importante para la seguridad energética nacional, y jugó un papel importante en la reducción de las emisiones de carbono. Proviene de recursos naturales, como el viento, la energía solar, la lluvia, las mareas, la biomasa y el calor geotérmico. Entre ellos, la energía eólica está emergiendo rápidamente como una tecnología sostenible de bajo carbono, eficiente en el uso de los recursos y rentable en el mundo. Debido a la demanda de instalaciones de producción de mayor potencia con menos impactos ambientales, el aumento continuo en el tamaño de las turbinas eólicas y las tecnologías offshore (flotantes) recientemente desarrolladas han llevado a nuevos desafíos en los sistemas de turbinas eólicas. Las turbinas eólicas son sistemas complejos con grandes estructuras flexibles que funcionan en condiciones ambientales muy turbulentas e impredecibles para una red eléctrica variable. La maximización de los sistemas de conversión de energía eólica, los problemas de minimización de la fatiga mecánica, los costos por kilovatios-hora de estrategias de reducción, cuestiones de confiabilidad, problemas de estabilidad y disponibilidad (sostenibilidad) exigen el uso de sistemas avanzados de control cooperativo (multivariable y multiobjetivo) para regular variables tales como paso, par, potencia, velocidad del rotor, factores de potencia de cada aerogenerador, etc. Mientras tanto, con las crecientes demandas de eficiencia y calidad del producto y la progresiva integración de los sistemas de control automático en los procesos de alto costo y de seguridad crítica, los campos de detección y aislamiento de fallos (FDI) y control tolerante a fallos (FTC) juegan un papel importante. Esta tesis cubre el desarrollo teórico y también la implementación de diferentes técnicas de FDI y FTC en turbinas eólicas. El propósito de los sistemas FDI es detectar y ubicar las degradaciones y fallos en la operación de los componentes tan pronto como sea posible, de modo que las operaciones de mantenimiento puedan realizarse a su debido tiempo (por ejemplo, durante periodos con baja velocidad del viento). Por lo tanto, se puede reducir el número de costosas acciones de mantenimiento correctivo y, en consecuencia, se reduce al mínimo la pérdida de producción de energía eólica debido a las operaciones de mantenimiento. El objetivo de la FTC es diseñar controladores apropiados de modo que el sistema de bucle cerrado resultante pueda tolerar operaciones anormales de componentes de control específicos y retener la estabilidad general del sistema con un rendimiento aceptable del sistema. Diferentes contribuciones de FDI y FTC se presentan en esta tesis y se publican en diferentes revistas indexadas a JCR y en congresos internacionales. Estas contribuciones abarcan una amplia gama de fallos WTs realistas, así como diferentes tipos de turbinas (en tierra, en alta mar ancladas al fondo del mar y flotantes). El rendimiento de las contribuciones propuestas se prueba en simulaciones con el código aeroelástico FAST.
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Schlipf, David [Verfasser]. "Lidar-Assisted Control Concepts for Wind Turbines / David Schlipf." München : Verlag Dr. Hut, 2016. http://d-nb.info/1094117714/34.
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Cardenas-Dobson, Roberto. "Control of wind turbines using a switched reluctance generator." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320626.
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Soraghan, Conaill Eoin. "Aerodynamic modelling and control of vertical axis wind turbines." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23210.
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Designing a structure which harnesses energy from the wind offshore is a radically different design challenge compared to that which the industry standard three-blade Danish model horizontal axis wind turbine (HAWT) has evolved to serve. Vertical axis wind turbines (VAWTs) may prove to be suitable candidates for the offshore sector due to the potential to locate heavy and complex mechanical components near the water surface providing ease of access and a low centre of gravity. Unlike their horizontal-axis counterparts, VAWT designs have not benefited from forty years of intense research and development. Therefore many challenges lie ahead for VAWT technology but lessons can be drawn from the development of HAWT technology. The main aims of this thesis are to create a design tool capable of investigating the performance of large scale, variable pitch VAWTs and to provide analyses of rotor design and control systems that would align utility scale VAWTs with aerodynamic performance and operational flexibility of state of the art HAWTs. The design tool developed is based on the double multiple streamtube (DMS) adaptation of blade element momentum theory and it incorporates tip loss effects, flow curvature, dynamic stall, flow expansion and variable pitch. Validation demonstrates good estimation of local wind flow conditions and aerodynamic performance for both fixed pitch and variable pitch rotors. The model has been developed to investigate in particular V-rotor performance and the potential of variable pitch for VAWTs. A contribution is made to DMS modelling, which involves capturing the effects of varying degrees of streamtube expansion occurring along the blade. This contribution is referred to as fanning and is particularly significant when implementing or designing pitch regimes. Three novel investigations are provided that contribute to fixed pitch VAWT rotor design and control. Firstly, a method for applying lift to drag ratio to VAWTs is introduced, which accounts for azimuthal variation in aerodynamic performance. Secondly, the impact of wind shear on V-rotor rotor design is analysed. Thirdly, a solution for smoothing power fluctuations from aggregated VAWTs is proposed, which is based on controlling the phase of each rotor so peaks in individual generated power do not occur simultaneously. A holistic approach to the way in which cyclic variable pitch can benefit VAWT operation is provided. Five control objectives are identified that span the entire operating envelope for any wind turbine, namely providing high torque during start-up, maximising power coefficient in below rated conditions, alleviating cyclic loading, power limiting in above rated conditions and aerodynamic braking in extremely high winds. Two test case turbines are designed, a similarly rated H-rotor and V-rotor, and for each turbine and each objective, a cyclic pitch regime is developed and analysed.
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Wang, Chen. "Control, stability analysis and grid integration of wind turbines." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/1291.
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In Chapters 2 and 3 of the thesis we propose a self-scheduled control method for a doublyfed induction generator driven by a wind turbine (DFIGWT), whose rotor is connected to the power grid via two back-to-back PWM power converters. We design a controller for this system using the linear matrix inequality based approach to linear parameter varying (LPV) systems, which takes into account the nonlinear dynamics of the system. We propose a two-loop hierarchical control structure. The inner-loop current controller, which considers the synchronous speed and the generator rotor speed as a parameter vector, achieves robust tracking of the rotor current reference signals. The outer-loop electrical torque controller aims for wind energy capture maximization, grid frequency support and generates the reference rotor current. We perform a controller reduction for the inner-loop LPV controller, which is not doable by conventional model-reduction techniques, because the controller is parameter-dependent. In simulation, the reduced order controller has been tested on a nonlinear 4th order DFIG model with a two-mass model for the drive-train. Stability and high performances have been achieved over the entire operating range of the DFIGWT. More importantly, simulation results have demonstrated the capability and contribution of the proposed two-loop control systems to grid frequency support. In Chapter 4 we investigate the integral input-to-state stability (iISS) property for passive nonlinear systems. We show that under mild assumptions, a passive nonlinear system which is globally asymptotically stable is also iISS. Moreover, the integral term from the definition of the iISS property has a very simple form (like an L1 norm). These theoretical results will be useful for our stability analysis of wind turbine systems in Chapter 5. In Chapter 5 we investigate the stability of a variable-speed wind turbine operating under low to medium wind speed. The turbine is controlled to capture as much wind energy as possible. We concentrate on the mechanical level of the turbine system, more precisely on the drive-train with the standard quadratic generator torque controller. We consider both the one-mass and the two-mass models for the drive-train, with the inputs being the deviation of the active torque from an arbitrary positive nominal value and the tracking error of the generator torque. We show that the turbine system is input-to-state stable for the one-mass model and iISS for the two-mass model. Using our abstract results from Chapter 4, we identify the iISS gain of this system. We also propose an adaptive search algorithm for the optimal gain of the quadratic torque controller.
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Robotham, Antony John. "The aerodynamic control of the V-type vertical axis wind turbine." n.p, 1989. http://ethos.bl.uk/.
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Sánchez, Sardi Héctor Eloy. "Prognostics and health aware model predictive control of wind turbines." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/463321.
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Wind turbines components are subject to considerable stresses and fatigue due to extreme environmental conditions to which they are exposed, especially those located offshore. Also, the most common faults present in wind turbine components have been investigated for years by the research community and that has led to propose a fault diagnosis and fault tolerant control wind turbine benchmark which include a set of faults that affect the sensors and actuators of several wind turbine components.
This thesis presents some contributions to the fields of fault diagnosis, fault-tolerant control, prognostics and its integration with wind turbine control which leads to proposing a control approach called health-aware model predictive control (HAMPC). The contributions are summarized below:
- Model-based fault diagnosis: to perform fault detection and isolation interval-based observers together with a set of analytical redundant relations (ARRs) are obtained based on a structural analysis and the fault signature matrix that relates the ARRs with the faults. - Fault tolerant control: it is proposed a fault tolerant control scheme that integrates fault detection and an algorithm for fault accommodation. The scheme has the objective to avoid the increment of blades and tower loads when a fault in the rotor azimuth angle sensor occurs using the individual pitch control technique (IPC).
- Wind turbine blades fatigue prognostics and degradation: fatigue is assessed using the rainflow counting algorithm which is used to estimate the accumulated damage and for degradation, it is used a stiffness degradation model of blades material which is used to make predictions of remaining useful life (RUL).
- Wind turbines health control: the module for the health of the system based on fatigue damage estimation and RUL predictions is integrated with model predictive control (MPC) leading to the proposed control approach (HAMPC).
The contributions presented in this thesis have been validated on a wind turbine study case that uses a 5MW wind turbine reference model implemented in a high fidelity wind turbine simulator (FAST).Els components dels aerogeneradors estan sotmesos a considerable estrès i fatiga, degut a les condicions ambientals extremes a les quals estan exposats, especialment els localitzats en alta mar. Per aquest motiu, al comunitat científica durant els últims anys ha investigat les averies més comunes presents en els aerogeneradors, fet que ha portat a proposar un cas d'estudi de diagnosi i control tolerant de fallades que inclou un conjunt de fallades que afecten a diversos components dels aerogeneradors. Aquesta tesi presenta algunes contribucions en els camps de la diagnosi de fallades, el control tolerant de fallades i la prognosi, així com la seva integració amb el control d'aerogeneradors, fet que ha portat a proposar una tècnica de control anomenada control predictiu basada en models conscients de la salut del sistema (HAMPC). Concretament les aportacions es poden resumir en: - Diagnosi de fallades basada en models: per a la detecció s'utilitzen observadors intervalars i l'aïllament de la fallada es fa en base el conjunt d'ARRs obtinguts de l'anàlisi estructural i de la matriu de signatures de fallades que relaciona les ARRs amb les fallades. - Control tolerant de fallades: es proposa un esquema de control tolerant a fallades que integra la detecció de fallades i algoritme d'acomodació de fallades, i té per objectiu evitar l'augment de càrregues en la pala i la torre quan es produeix una fallada en el sensor azimuth quan es fa un control individual de la inclinació de les pales (IPC). - Prognosi de la fatiga i la degradació de les pales: la fatiga s'avalua amb un algorisme denominat "rainflow counting" amb el qual es fa estimació del dany acumulat i per a la degradació es fa servir un model de degradació de la rigidesa del material amb el qual es fan prediccions de la vida útil restant (RUL). - Control de la salut d'aerogeneradors: s'ha integrat la gestió de la salut del sistema basat en danys per fatiga o prediccions de RUL amb control predictiu basat en models (MPC) donant lloc al control que anomenem HAMPC. Les contribucions presentades en aquesta tesi han sigut validades en un cas d'estudi d'aerogeneradors basat en un aerogenerador de referència de 5MW de potència implementat en el simulador d'aerogeneradors d'alta fidelitat conegut amb el nom de FAST.
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Iqbal, Muhammad Tariq. "Dynamic control strategies for fixed and variable speed wind turbines." Thesis, Imperial College London, 1994. http://hdl.handle.net/10044/1/7737.
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Homer, Jeffrey R. "Physics-based control-oriented modelling for floating offshore wind turbines." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54891.
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As offshore wind technology advances, floating wind turbines are becoming larger and moving further offshore, where wind is stronger and more consistent. Despite the increased potential for energy capture, wind turbines in these environments are susceptible to large platform motions, which in turn can lead to fatigue loading and shortened life, as well as harmful power fluctuations. To minimize these ill effects, it is possible to use advanced, multi-objective control schemes to minimize harmful motions, reject disturbances, and maximize power capture. Synthesis of such controllers requires simple but accurate models that reflect all of the pertinent dynamics of the system, while maintaining a reasonably low degree of complexity.
In this thesis, we present a simplified, control-oriented model for floating offshore wind turbines that contains as many as six platform degrees of freedom, and two drivetrain degrees of freedom. The model is derived from first principles and, as such, can be manipulated by its real physical parameters while maintaining accuracy across the highly non-linear operating range of floating wind turbine systems. We validate the proposed model against advanced simulation software FAST, and show that it is extremely accurate at predicting major dynamics of the floating wind turbine system.
Furthermore, the proposed model can be used to generate equilibrium points and linear state-space models at any operating point. Included in the linear model is the wave disturbance matrix, which can be used to accommodate for wave disturbance in advanced control schemes either through disturbance rejection or feedforward techniques. The linear model is compared to other available linear models and shows drastically improved accuracy, due to the presence of the wave disturbance matrix.
Finally, using the linear model, we develop four different controllers of increasing complexity, including a multi-objective PID controller, an LQR controller, a disturbance-rejecting H∞ controller, and a feedforward H∞ controller. We show through simulation that the controllers that use the wave disturbance information reduce harmful motions and regulate power better than those that do not, and reinforce the notion that multi-objective control is necessary for the success of floating offshore wind turbines.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Rogers, Mary C. M. "Control aspects of integrated design of wind turbines : a foundation." Thesis, University of Strathclyde, 1998. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21367.
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The configuration of a wind turbine and its control system dictate the dynamics of the machine. Since the dynamics of each part of the wind turbine affect those of the others, the machine should be considered as an integrated unit. The objective of the research reported here is to lay the foundations for the control aspects of integrated design by determining the dependence of the power controller performance of medium- and largescale, actively regulated, up-wind, horizontal-axis, grid-connected wind turbines on their configuration, that is, the dependence of the magnitude of the loads experienced by the drive train on the machine characteristics. There is a tendency amongst manufacturers to move from conventional, heavy and stiff machines to ones with lighter and more flexible components which makes machines more dynamically active and hence makes the power control task more difficult. Simple thoroughly derived linear and non-linear models of the significant wind turbine dynamics for power control are used to obtain a greater understanding of how machine parameters effect the overall behaviour of the power train. The dependence of the power controller performance of different full-span and tip-regulated machines is discussed. Finally, explanation of the results is illustrated with regard to the design of a 1 MW wind turbine.
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Al-Toma, Ahmed Selman Hadi. "Hybrid control schemes for permanent magnet synchronous generator wind turbines." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15194.
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Wind turbines require continuous monitoring and control in order to maintain the power output as the wind speed varies. Traditional control techniques using conventional equipment and devices have been used in small scale generators at a commercial or residential level. A range of techniques have been developed and used to control generation output and to satisfy grid code requirements. Such techniques have demonstrated good performance with constant wind speed and linear system parameters. At the same time classical control techniques, based on the linear Proportional Integral controller and low band-width modulation, present several technical issues during lower switching frequency operation as well as slow response to uncertainty in system parameters. It is important to note that wind turbines are non-linear in nature and therefore require robust controllers that can adjust to the changes in the external environment as well as operational conditions and disturbances. For this reason, advanced control schemes have been proposed to mitigate the effects of potential system disturbances. A variety of advanced control methods have recently been applied in response to wind energy conversion problems, such as fuzzy logic, slide mode, adaptive and predictive that have been applied to solve some of these problems. Such techniques are only valid for a specific operational range and do not cover the whole operational region with regard to rate of change of wind speed. Therefore, when considering large scale power generation from wind energy, high turbulence wind velocities and uncertainty in system parameters require the development of new hybrid controllers in order to address such problems. In order to improve the system performance and deal with uncertainties under different operational conditions, advanced control techniques such as model reference control and model predictive control are combined with fuzzy logic control. This thesis presents detailed analyses, modelling and simulation of novel and hybrid control schemes for variable speed wind turbines as operated in small or large scale such as 2 MW grid-connected Permanent Magnet Synchronous Generators. The proposed controllers show a reduction of steady state errors, reduced overshoot of the rotor speed and an increase in the active power that is generated. The results are compared to conventional controllers such as Proportional Integral controller in order to demonstrate the improved performance and the robustness of system.
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Morshed, Mohammad Javad. "Fault Ride-Through Control Paradigms for DFIG-Based Wind Turbines." Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10811697.
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This dissertation designs three different fault ride through (FRT) approaches to improve the performance of DFIG based WT during voltage sag conditions. First, an integral terminal sliding mode controller (ITSMC) was implemented for the rotor-side converter (RSC) and grid-side converter (GSC), and a fuzzy logic and a Posicast approach are also proposed to control the series grid side converter (SGSC). In the second approach, a fuzzy second order integral terminal sliding mode (FSOITSMC) approach for both RSC and GSC, along with a FSOITSMC-based Posicast controller for the SGSC, which is placed in series with the DFIG, have been applied to enhance the DFIG?s performance. Lastly, a fault ride through design has been applied for hybrid PV-Wind power generation systems. In the proposed configuration, the PV system was connected to the DC-link of the DFIG through a DC-DC converter. During voltage sag conditions, an SGSPI protection system is activated while the GSC acted as a STATCOM, thus injecting reactive power to the grid. The effectiveness of the proposed fault tolerant configuration approaches in riding through different types of grid faults is evaluated via detailed computer experiments. The merits of the proposed approach are further compared to those of the standard state of the art in voltage sag mitigation. Results clearly show that the proposed control paradigm is able to protect the converters from damages and ensure continuous connection of the WT to the grid during faults, hence maintaining power quality.
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Zhang, Cheng. "A contribution to the nonlinear control of floating wind turbines." Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0009.
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Les éoliennes flottantes permettent d’utiliser l’abondante ressource en vent présente au large des côtes, et sont considérées comme une source prometteuse d’énergie renouvelable. Cependant, en raison de dynamiques supplémentaires introduites par la plateforme flottante (notamment, le tangage), le contrôle d’une éolienne flottante doit être pensée afin de stabiliser le système tout en optimisant la production d’énergie. Ce travail est consacré à la commande non linéaire d’éoliennes flottantes dans la région III, la classe de lois de commande proposée nécessitant une connaissance réduite en terme de modélisation du système. Les objectifs de la commande sont de maintenir la puissance produite à sa valeur nominale, tout en li mitant le mouvement de tangage de la plateforme et les charges de fatigue sur la structure. Tout d’abord, une loi de commande adaptative basée sur le supertwisting est proposée, avec notamment une loi d’adaptation du gain très simple. Ensuite, en utilisant un contrôle collectif du pas des pales, ce nouvel algorithme de commande est appliqué sur un modèle d’éolienne flottante non linéaire et comparé à d’autres commandes adaptatives par modes glissants d’ordre 2. Dans un second temps, une machine synchrone à aimants permanents est supposée être installée dans l’éolienne flottante. L’utilisation du pas des pales (approche collective) et du couple du générateur permet d’atteindre les objectifs, à partir de lois de commande basées sur une approche adaptative par mode de glissement d’ordre 2. Une troisième partie est consacrée à l’étude d’une commande individuelle du pas des pales combinée à une commande collective. Il est montré qu’un tel algorithme limite la charge de fatigue des pales. Enfin, des lois de commande sont appliquées et comparées sur un système expérimental d’éolienne flottante placé dans un bassin à houle. Les performances des lois de commande basées sur les modes glissants sont évaluées par rapport à des approches de commande linéaire telles qu’un PI à gain variable, et une commande linéaire quadratiqueFloating wind turbines allow the use of the abundant wind resource in ocean area and are considered as a promising solution of renewable energy. However, due to the additional dynamics (especially the platform pitch motion) introduced by the floating platform, the control of a floating wind turbine must take such pitch motion into consideration to stabilize the system meanwhile optimizing the power output. This work is dedicated to the nonlinear control of floating wind turbines in region III, this class of controllers requiring reduced knowledge of system modeling and parameter. The control objectives are to maintain the power output at its rated value, to reduce the platform pitch motion and to limit the fatigue load. Firstly, a simplified adaptive super-twisting is proposed. Then, by using collective blade pitch control, this algorithm and other adaptive high order sliding model algorithms are applied on a nonlinear floating wind turbine model. Secondly, a permanent magnet synchronous generator is supposed to be installed in the floating wind turbine. Both collective blade pitch control and generator torque control based on adaptive high-order sliding mode control are used to achieve the control objectives. Thirdly, individual blade pitch control combined with collective blade pitch control is employed. Such algorithm further reduces the fatigue load of blades. Finally, the proposed simplified adaptive super-twisting algorithm is validated on an experimental floating wind turbine set-up (with a spar-buoy platform) in a wave tank, and the control performances are evaluated versus linear control approaches such as gain-scheduled PI and linear–quadratic regulators
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Rossander, Morgan. "Electromechanics of Vertical Axis Wind Turbines." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331844.
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Wind power is an established mean of clean energy production and the modern horizontal axis wind turbine has become a common sight. The need for maintenance is high and future wind turbines may need to be improved to enable more remote and offshore locations. Vertical axis wind turbines have possible benefits, such as higher reliability, less noise and lower centre of gravity. This thesis focuses on electromechanical interaction in the straight bladed Darrieus rotor (H-rotor) concept studied at Uppsala University. One of the challenges with vertical axis technology is the oscillating aerodynamic forces. A force measurement setup has been implemented to capture the forces on a three-bladed 12 kW open site prototype. The normal force showed good agreement with simulations. An aerodynamic torque could be estimated from the system. The total electrical torque in the generator was determined from electrical measurements. Both torque estimations lacked the expected aerodynamic ripple at three times per revolution. The even torque detected is an important result and more studies are required to confirm and understand it. The force measurement was also used to study the loads on the turbine in parked conditions. It was discovered that there is a strong dependence on wind direction and that there is a positive torque on the turbine at stand still. The results can assist to determine the best parking strategies for an H-rotor turbine. The studied concept also features diode rectification of the voltage from the permanent magnet synchronous generator. Diodes are considered a cheap and robust solution for rectification at the drawback of inducing ripple in the torque and output voltage. The propagation of the torque ripple was measured on the prototype and studied with simulations and analytical expressions. One key conclusion was that the mechanical driveline of the turbine is an effective filter of the diode induced torque ripple. A critical speed controller was implemented on the prototype. The controller was based on optimal torque control and according to the experiments and the simulations it was able to avoid a rotational speed span. Finally, the optimal torque control was evaluated for multiple turbines with diode rectification to a common DC-link. The setup can potentially reduce the overall complexity of wind farms. The simulations suggest that stability of the system can be obtained by controlling the DC-link load as a semi constant voltage. The thesis is based on nine papers of which six are treated in the thesis summary.
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Bourlis, Dimitrios. "Control algorithms and implementation for variable speed stall regulated wind turbines." Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/28800.
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In this research control algorithms and implementation for variable speed stall regulated wind turbines are presented. This type of wind turbine has a simpler and more robust construction and can have lower requirements for maintenance than the existing pitch regulated wind turbines. Due to these features these wind turbines can have reduced cost, which is a crucial parameter especially for large scale wind turbines. However, this type is not commercially available yet due to existing challenges in its control. In this research a complete control scheme for variable speed stall regulated wind turbines has been developed and implemented in a fully dynamic hardware-in-loop simulator for variable speed wind turbines. The simulator was developed as part of the project in order to validate the designed control algorithms. The developed control system uses novel adaptive methods in order to maximize the energy production of the wind turbines at below rated wind speeds as well as to control the power of the wind turbine at above rated wind speeds. In addition, several types of controllers including robust controllers have been used and tested, which resulted to novel control solutions for stall regulated wind turbines. The main advantage of the proposed control method is that it uses existing hardware without requiring additional sensors, so it more effectively exploits information coming from measurements available in existing wind turbine converters. Through software and hardware simulations the proposed control algorithms seem to be quite promising and give confidence for the future development of variable speed stall regulated wind turbines.
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Bagherieh, Omid. "Gain-scheduling control of floating offshore wind turbines on barge platforms." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44879.
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This thesis studies the application of gain-scheduling (GS) control techniques to floating offshore wind turbines on barge platforms. Modelling, control objectives, controller design and performance evaluations are presented for both low wind speed and high wind speed cases. Special emphasis is placed on the dynamics variation of the wind turbine system caused by plant nonlinearity with respect to wind speed.
The dynamics variation is represented by a linear parameter-varying (LPV) model. The LPV model for wind turbines is derived by linearizing the nonlinear dynamics at various operating wind speeds and by interpolating the linearized models.
In low wind speed, to achieve control objectives of maximizing power capture and minimizing platform movements, for the LPV model, the LPV GS design
technique is explored. In this region, the advantage of making use of blade pitch angle as a control input is also investigated. In high wind speed, to achieve control objectives of regulating power capture and minimizing platform movements, both LQR and LPV GS design techniques are explored.
To evaluate the designed controllers, simulation studies are conducted with a realistic 5 MW wind turbine model developed at National Renewable Energy Laboratory, and realistic wind and wave profiles. The average and root mean square values of power capture and platform pitch movement are adopted as performance measures, and compared among designed GS controllers and conventional controllers. The comparisons demonstrate the performance improvement achieved by GS control
techniques.
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Collet, David. "Fatigue-oriented data-driven individual pitch control strategies of wind turbines." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT063.
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Les éoliennes à axe horizontal, qui sont la figure de proue de l'énergie éolienne sont devenues une technologie mature. Bien que l'éolien est une tendance mondiale à la hausse, l'accroissement de la capacité installée faiblit dans certains pays, à cause des réductions des subventions. Dans un contexte de réchauffement climatique et de transition énergétique, il est de première importance d'optimiser le coût de l'éolien, de manière à rendre cette énergie compétitive face aux énergies fossiles, et ainsi permettre un développement de l'éolienne moins dépendant des subventions économiques. Le contrôle des éoliennes peut fortement contribuer à la réponse à cette problématique.Le contrôle individuel des pâles (IPC) d'éoliennes peut permettre de modifier les propriétés aérodynamiques du rotor, et ainsi réguler les charges déséquilibrées induites par des vents asymétriques. Réguler ces déséquilibres peut aider à réduire la fatigue des pièces de l'éoliennes en rotation, telle que les pâles. Par ailleurs, le contrôle IPC est connu pour accroître l'activité des actionneurs de pâles, induisant une fatigue additionnelle sur les actionneurs ainsi que les roulements portant les pâles. Par conséquent, le contrôle IPC peut avoir des effets positifs sur la fatigue de certaines pièces, mais négatifs sur d'autres. Pour optimiser le coût de l'énergie éolienne, il est nécessaire qu'un contrôleur IPC soit optimisé de manière à pondérer efficacement le compromis entre les fatigues des divers composants de l'éolienne.Pour répondre à cette problématique, une fonction de coût de la fatigue a été définie comme la somme pondérée de la fatigue de divers composants de l'éolienne. Un contrôleur IPC doit être conçu de manière à minimiser l'espérance du coût de la fatigue. Cependant, l'optimisation de la fatigue est une tâche complexe, car son expression en tant que fonction de coût ne suit pas les formes conventionnelles. Il est montré plusieurs fois au cours de cette thèse que les stratégies de contrôle conventionnelles limitent le potentiel de réduction de la fatigue. Par ailleurs, combiner plusieurs stratégies de contrôle conventionnelles paramétrées différemment pourrait permettre des réductions significatives de l'espérance du coût de la fatigue, par rapport à des stratégies conventionnelles à paramètre fixes. La problématique adressée dans cette thèse est donc l'adaptation des paramètres de stratégies de contrôle IPC conventionnelles, pour une réduction efficace de la fatigue d'éoliennes. Deux approches sont ainsi développées par la suite.La première consiste à approcher le coût de la fatigue par une fonction de coût orientée fatigue, grâce à une identification basée sur des données. Cette fonction de coût orientée fatigue utilisée dans un problème de contrôle optimal permet de paramétrer un problème d'optimisation standard, qui approche le problème d'optimisation de la fatigue autour de son optimum. Le problème d'optimisation orienté fatigue permet ainsi des réductions efficaces du coût de la fatigue.La commande prédictive (MPC) est une stratégie de contrôle qui permet d'optimiser une fonction de coût spécifique, en résolvant en ligne un problème de contrôle optimal. Ensuite, un contrôleur IPC MPC est obtenue à partir de l'expression du problème d'optimisation orienté fatigue. Ces contrôleurs ont ensuite été mis en oe uvre en boucle fermée sur un modèle d'éolienne simplifié, et ont montré un grand potentiel de réduction de l'espérance du coût de la fatigue, par rapport à un contrôleur MPC à paramètres fixés.La seconde solution est une méthodologie où un superviseur basé sur l'apprentissage, sélectionne les paramètres de contrôleurs candidats à partir des conditions de vent, de manière à réduire efficacement le coût de la fatigue d'une éolienne. Une preuve de concept comportant un superviseur simple a montré que des réductions significatives de la fatigue sont possibles, ce qui encourage aussi le développement de cette seconde approcheHorizontal axis wind turbines are the leading figure of the wind energy industry and is becoming a mature technology. Even though wind energy is globally trending, the yearly number of wind turbines installed is weakening in some countries, due to the reduction of economic subventions. In the context of global warming and energetic transition, it is of primal importance to optimize the levelized cost of wind energy, in order to make it economically competitive against fossil source of energies and allow wind energy to less rely on economic subventions. The control of wind turbines can strongly contribute to answer this issue.Individual blade Pitch Control (IPC) of wind turbines can allow to modify the aerodynamic properties of the rotor and regulate the unbalanced loads due to skewed wind in the rotor plane. Regulating these unbalanced loads can help in alleviating the fatigue damage of the rotating components of the turbine, such as the blades. On the other hand, IPC is known to induce oscillating loads on the blade pitch actuators and increase their excursions, which induces additional fatigue damage on the blade pitch actuators and blade bearings. Therefore, IPC can have positive effects on the fatigue damage of some components of the turbine, while having negative effects on others. For an efficient optimization of the levelized cost of wind energy, it is necessary that an IPC be optimized, in order to efficiently manage the trade-off between the fatigue damage of various components of a turbine.To address this issue, a fatigue cost function is defined as a weighted sum of wind turbine components fatigue damage, and possibly economic parameters. An IPC regulator must thus be designed in order to minimize this fatigue cost. However, the optimization of fatigue is a challenging task, as the fatigue damage expression does not suit standard forms. It is shown several times in this thesis that standard control strategies are limiting the potential reduction of the fatigue cost expectancy. While combining several standard control strategies designed with different parameters could allow significant reductions of the fatigue cost expectancy, compared to standard IPC control strategies with fixed parameters. The challenge addressed in this thesis is thus to adapt the parameters of standard IPC control strategies, in order to efficiently reduce the fatigue cost expectancy of wind turbines. Two approaches are thus developed in order to address this issue.The first one consists in approximating the fatigue cost function with a fatigue-oriented cost function, thanks to a data-driven identification based on parameterized quadratic forms. This fatigue-oriented cost function used in an optimal control problem allows to efficiently parameterize a standard optimization problem, which approximate the fatigue cost optimization problem around its optimum. Therefore, the fatigue-oriented optimal control problem allows efficient reductions of the fatigue cost expectancy.Model Predictive Control (MPC) is a control strategy which allows to optimize a specified cost function, by solving on-line an optimal control problem. Then, an IPC MPC is derived based on the fatigue-oriented optimal control problem expression. These controllers are thus standard MPCs whose parameters are adapted for fatigue cost reduction. These controllers are then implemented in closed-loop with a simplified wind turbine model and showed great potential in reducing the fatigue cost expectancy, compared to an MPC with fixed parameters.The second approach is a framework where a supervisory layer selects the parameters of candidate controllers based on wind conditions, in order to efficiently minimize the wind turbine fatigue cost expectancy. A proof of concept made with a simple supervisory layer showed that significant reduction of the fatigue cost are already possible, which encourages to also develop this second approach further
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Namik, Hazim. "Individual blade pitch and disturbance accommodating control of floating offshore wind turbines." Thesis, University of Auckland, 2012. http://hdl.handle.net/2292/11198.
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Floating wind turbines offer a feasible solution for going further offshore into deep waters. However, using a floating platform introduces additional motions that must be taken into account actively or passively. Therefore, the control system becomes an important component in controlling these motions. In this work, the development, implementation, and simulation of multi-objective state feedback and disturbance accommodating controllers applied on the three main floating concepts are described. The three concepts are the barge, tension leg, and spar-buoy floating platforms. These controllers utilise individual blade pitching to create asymmetric aerodynamic loads in addition to the symmetric loads created by collective blade pitching to increase the platform restoring moments. Simulation results, according to design load case 1.2 of the IEC 61400-3 standard for offshore wind turbines, show that state feedback controllers improve the performance relative to a collective blade pitch gain scheduled proportional-integral controller in terms of power and rotor speed regulation as well as reducing tower fore-aft and side-side bending loads. However, the magnitude of the improvements depends on the dynamics of each platform, its responsiveness to individual blade pitching and sensitivities to external wind and wave disturbances. Furthermore, interesting physical phenomena, such as the platform roll to pitch coupling caused by the controller, are identified. Disturbance accommodating controllers for rejecting wind speed perturbations further improve rotor speed regulation and reduce tower fore-aft bending loads except on the barge platform; the barge platform motion is dominated by incident waves and therefore rejecting wind speed perturbations has no noticeable impact. Wave moment disturbance rejection is also investigated but in a limited case study. While the approach taken can theoretically cancel the effects of incident wave moments, practically, the required actuation force cannot be generated by the wind turbine blades. Furthermore, using the blades for rejecting wave moments increases the tower bending due to the load path of the restoring moment through the tower. Out of the three investigated platforms, the tension leg platform with a disturbance accommodating controller has the best overall performance with fatigue loads close or less than that of an onshore wind turbine. The other two platforms, in their current design form, experience large tower fore-aft bending loads that would prevent them from being deployed in rough sea conditions.
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Chen, Hao. "Numerical study of trailing edge flow control for horizontal axis wind turbines." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13354/.
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Wind turbines have been developed for more than a century and nowadays wind turbines are still facing some challenges such as efficiency and maintenance problems. Load control is considered to be one of the most important parts for future horizontal axis wind turbine (HAWT) designs. Deploying effective flow control devices on the blades could either increase loads at off-design wind speed conditions or reduce the extreme loads, leading to either higher energy output or a more stable energy output from the wind turbine. This study reports a research into the performance of trailing edge flow control devices of HAWT by solving the Reynolds averaged Navier-Stokes equations. The validation case selected for this work is the NREL Phase VI blade with experimental data. The trailing edge flow control devices studied include microtabs and microjets installed near the trailing edge of the rotating blade. The divergent trailing edge is also included in the study as a passive flow control device due to its practical interest. These trailing edge devices are implemented on the fixed-pitch NREL Phase VI blade, using the original performance and flow characteristics as a benchmark. Both 2D and 3D simulations are carried out in order to investigate the suitability of the 2D blade sectional design analysis and control for the actual 3D rotating framework. Moreover, the study is extended to an active pitch-regulated offshore wind turbine, NREW 5MW wind turbine. Firstly the code to code comparison is carried out for validation purpose. Then the trailing edge flow control devices are also deployed on this wind turbine to find out their effectiveness. The results show there are significant differences when compared to the conclusions from the CFD study on the NREL Phase VI blade.
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Chen, Zhe. "Advanced wind energy convertors using electronic power conversion." Thesis, Durham University, 1997. http://etheses.dur.ac.uk/1632/.
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Edwards, Gregory W. "Wind turbine power generation emulation via doubly fed induction generator control." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FEdwards.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2009.Thesis Advisor(s): Julian, Alexander L. Second Reader: Cristi, Roberto. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Double Fed Induction Generator (DFIG), Space Vector Modulation (SVM), wind turbine, Field Programmable Gate Array (FPGA), bi-directional power flow. Includes bibliographical references (p. 75). Also available in print.
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Burnham, David James. "Control of wind turbine output power via a variable rotor resistance." Thesis, [Austin, Tex. : University of Texas, 2009. http://hdl.handle.net/2152/ETD-UT-2009-05-105.
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Kjellin, Jon. "Vertical Axis Wind Turbines : Electrical System and Experimental Results." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182438.
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The wind power research at the division of Electricity at Uppsala University is aimed towards increased understanding of vertical axis wind turbines. The considered type of wind turbine is an H-rotor with a directly driven synchronous generator operating at variable speed. The experimental work presented in this thesis comprises investigation of three vertical axis wind turbines of different design and size. The electrical, control and measurement systems for the first 12 kW wind turbine have been designed and implemented. The second was a 10 kW wind turbine adapted to a telecom application. Both the 12 kW and the 10 kW were operated against dump loads. The third turbine was a 200 kW grid-connected wind turbine, where control and measurement systems have been implemented. Experimental results have shown that an all-electric control, substituting mechanical systems such as blade-pitch, is possible for this type of turbine. By controlling the rectified generator voltage, the rotational speed of the turbine is also controlled. An electrical start-up system has been built and verified. The power coefficient has been measured and the stall behaviour of this type of turbine has been examined. An optimum tip speed ratio control has been implemented and tested, with promising results. Use of the turbine to estimate the wind speed has been demonstrated. This has been used to get a faster regulation of the turbine compared to if an anemometer had been used.
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Schlipf, David [Verfasser], and Po Wen [Akademischer Betreuer] Cheng. "Lidar-assisted control concepts for wind turbines / David Schlipf ; Betreuer: Po Wen Cheng." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2016. http://d-nb.info/1118369653/34.
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Den, Heijer Francois Malan. "Development of an active pitch control system for wind turbines / F.M. den Heijer." Thesis, North-West University, 2008. http://hdl.handle.net/10394/2635.
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A wind turbine needs to be controlled to ensure its safe and optimal operation, especially during high wind speeds. The most common control objectives are to limit the power and rotational speed of the wind turbine by using pitch control.
Aero Energy is a company based in Potchefstroom, South Africa, that has been developing and manufacturing wind turbine blades since 2000. Their most popular product is the AE1kW
blades. The blades have a tendency to over-speed in high wind speeds and the cut-in wind speed must be improved. The objective of this study was to develop an active pitch control system for wind turbines. A prototype active pitch control system had to be developed for the AE1kW blades. The objectives of the control system are to protect the wind turbine from over-speeding and to improve start-up performance.
An accurate model was firstly developed to predict a wind turbine’s performance with active
pitch control. The active pitch control was implemented by means of a two-stage centrifugal
governor. The governor uses negative or stalling pitch control. The first linear stage uses a soft spring to provide improved start-up performance. The second non-linear stage uses a hard spring to provide over-speed protection. The governor was manufactured and then tested with the AE1kW blades. The governor achieved both the control objectives of over-speed protection and improved start-up performance. The models were validated by the results.
It was established that the two-stage centrifugal governor concept can be implemented on any
wind turbine, provided the blades and tower are strong enough to handle the thrust forces
associated with negative pitch control. It was recommended that an active pitch control system be developed that uses positive pitching for the over-speed protection, which will eliminate the large thrust forces. Keywords: pitch control, wind turbine, centrifugal governor, over-speed protection, cut-in wind speed, blade element-momentum theory, rotor, generator, stall, feathering.Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2009.
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Menon, Ashwin. "Numerical investigation of synthetic jet based flow control for vertical axis wind turbines." Thesis, Rensselaer Polytechnic Institute, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1568426.
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This numerical study focuses on the implementation of active flow control using synthetic jets on vertical-axis wind turbine (VAWT) blades. This study demonstrates that synthetic-jet based flow control improves the efficiency of the turbine and reduces the risk of structural fatigue.
In VAWTs, the blades experience a significant variation in the angle of attack over each rotation cycle and associated with it are sudden changes in the flow-induced loading on the blades. For example, a sudden variation in blade loading is experienced due to the detachment of the leading edge vortex at high angles of attack. This is in-turn reduces the axial force and hence the overall power output of the turbine. Additionally, such force variations lead to structural fatigue and possibly failure. Current simulations consider a cross-section of a three-blade VAWT model (with straight blades). VAWT models with two different airfoils, NACA 0018 and DU 06-W-200, are considered at tip-speed-ratios of 2 and 3. In these simulations, unsteady, Reynolds-averaged Navier-Stokes equations along with the Spalart-Allmaras turbulence model are employed, where stabilized finite element method is utilized along with an implicit time-integration scheme.
The idea of using synthetic jets is to control the variation in flow-induced loading during each rotation cycle. At first the dominant location of the flow separation is determined for both airfoils. The jets are then placed at this location. Jet parameters of blowing ratio and reduced frequency are specified within a range (i.e., O(0.5-1.5) and O(1-10), respectively) and their effects on jet performance are studied. The jets are activated only in a selected portion of the rotation cycle. This is referred to as the partial cycle control in contrast to the full cycle (the latter is found to be detrimental). For given jet parameters, simulations results are used to determine whether the jets improve axial force, flow separation and blade-vortex interaction. At blowing ratio of 1.5 and reduced frequency of 5, we observe above 12% increase in the average axial force over the rotation cycle for both airfoils.
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Hoffmann, Rolf. "A comparison of control concepts for wind turbines in terms of energy capture." Phd thesis, [S.l. : s.n.], 2002. https://tuprints.ulb.tu-darmstadt.de/226/1/Diss.pdf.
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In this study, eight different control concepts for wind turbines are compared in terms of their annual energy capture. In detail, they are a stall controlled single speed concept, a stall controlled two speed concept, an active stall controlled single speed concept, an active stall controlled two speed concept, a pitch controlled single speed concept, a pitch controlled two speed concept, a stall controlled variable speed concept and finally a pitch controlled variable speed concept. In order to be able to expose all these different concepts to exactly the same wind conditions, numerical computer simulation is chosen as the appropriate method to do the comparison, as in reality it is almost impossible to achieve the same wind conditions for different turbines. This approach also prevents all possible differences in rotor layout between the individual concepts from entering into the results, as it is possible to use the same rotor design for all control concepts. Because the influence of time variant quantities such as the turbulent wind flow on a nonlinear system ( e.g. a wind turbine rotor) has to be taken into account, an analytical representation had to be found which allowed a time-step simulation. This especially set some limits on the complexity allowed for the numerical model. Therefore the modeling of all parts of the system (whether they are aerodynamic, mechanic or electric) is kept rather simplistic. As a comparison of general control concepts is the topic of this study, the controllers are not modeled as they are used by a certain manufacturer. Instead they are modeled in an idealized way, each of which covers the ideal performance of one class of control concepts. For each combination of parameters, one time domain simulation was performed. The output data was then weighted and averaged in order to obtain the energy captured from the wind within one year. These energy values are finally arranged in a way which allows an easy comparison between the relative performance of all control concepts under consideration. The results show the differences in the annual energy capture of the eight concepts as a function of site conditions (the annual mean wind speed, the turbulence and the shape parameter of the Weibull distribution assumed for the annual wind speed distribution) as well as their dependence on two design parameters (the design tip speed ratio and the choice of rotor profiles). Due to the rather crude modeling these results have to be seen more qualitatively then quantitatively. However, they show to which extent a comparison between different control concepts depends on the values of different parameters. Hopefully, they also lead to a deeper understanding of the very different results of similar comparisons found in the literature.
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Alkan, Deniz. "Investigating CVT as a Transmission System Option for Wind Turbines." Thesis, KTH, Energiteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121187.
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In this study, an innovative solution is examined for transmission problems and frequency control for wind Turbines. Power electronics and the gear boxes are the parts which are responsible of a significant amount of failures and they are increasing the operation and maintenance cost of wind turbines. Continuously transmission (CVT) systems are investigated as an alternative for conventional gear box technologies for wind turbines in terms of frequency control and power production efficiency. Even though, it has being used in the car industry and is proven to be efficient, there are very limited amount of studies on the CVT implementation on wind turbines. Therefore, this study has also an assertion on being a useful mechanical analyse on that topic. After observing several different types of possibly suitable CVT systems for wind turbines; a blade element momentum code is written in order to calculate the torque, rotational speed and power production values of a wind turbine by using aerodynamic blade properties. Following to this, a dynamic model is created by using the values founded by the help of the blade element momentum theory code, for the wind turbine drive train both including and excluding the CVT system. Comparison of these two dynamic models is done, and possible advantages and disadvantages of using CVT systems for wind turbines are highlighted. The wind speed values, which are simulated according to measured wind speed data, are used in order to create the dynamic models, and Matlab is chosen as the software environment for modelling and calculation processes. Promising results are taken out of the simulations for both in terms of energy efficiency and frequency control. The wind turbine model, which is using the CVT system, is observed to have slightly higher energy production and more importantly, no need for power electronics for frequency control. As an outcome of this study, it is possible to say that the CVT system is a candidate of being a research topic for future developments of the wind turbine technology.
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Alatar, Faris Muhanned Lutfi. "Frequency Scan–Based Mitigation Approach of Subsynchronous Control Interaction in Type-3 Wind Turbines." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104657.
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Subsynchronous oscillations (SSO) were an issue that occurred in the past with conventional generators and were studied extensively throughout the years. However, with the rise of inverter-based resources, a new form of SSO emerged under the name subsynchronous control interaction (SSCI). More specifically, a resonance case occurs between Type-3 wind turbines and series compensation that can damage equipment within the wind farm and disrupt power generation. This work explores the types of SSCI and the various analysis methods as well as mitigation of SSCI. The work expands on the concept of frequency scan to be able to use it in an on-line setting with its output data used to mitigate SSCI through the modification of wind turbine parameters. Multiple frequency scans are conducted using PSCAD/EMTDC software to build a lookup table and harmonic injection is used in a parallel configuration to obtain the impedance of the system. Once the impedance of the system is obtained then the value of the parameters is adjusted using the look-up table. Harmonic injection is optimized through phase shifts to ensure minimal disruption of the steady-state operating point and is conducted using Python programming language with PSCAD Automation Library. Simulation results demonstrate the effectiveness of this approach by ensuring oscillations do not grow exponentially in comparison to the regular operation of the wind farm.Master of Science
Due to climate change concern and the depletion of fossil fuel resources, electrical power generation is shifting towards renewables such as solar and wind energy. Wind energy can be obtained using wind turbines that transform wind energy into electrical energy, these wind turbines come in four different types. Type-3 wind turbines are the most commonly used in the industry which use a special configuration of the classical induction generator. These wind turbines are typically installed in a distant location which makes it more difficult to transfer energy from its location to populated areas, hence, series capacitors can be used to increase the amount of transferred energy. However, these series capacitors can create a phenomenon called subsynchronous control interaction (SSCI) with Type-3 wind turbines. In this phenomenon, energy is exchanged back and forth between the series capacitors and the wind turbines causing the current to grow exponentially which leads to interruptions in service and damage to major equipments within the wind turbine. This work explores SSCI, the tools to study it, and the currently available mitigation methods. It also presents a method to identify the cases where SSCI can happen and mitigates it using adjustable parameters.
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Kumar, Avishek. "Multivariable control of wind turbines for fatigue load reduction in the presence of nonlinearities." Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/17839.
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In an effort to reduce cost of energy from wind, wind turbines have grown to immense sizes. This has led to large, flexible, lightly damped towers and rotors that can be excited by the wind. Reducing the resulting fatigue loading and maintaining power capture are primary objectives for advanced controllers. In this thesis, a synthesis procedure for creating a multivariable linear parameter varying (LPV) controller suitable for the wind turbine control problem is created. The LPV controller uses the current wind speed estimate from an Extended Kalman Filter (EKF) for gain scheduling in order to accommodate system nonlinearities. The synthesis procedure allows the use of a parameter dependance Lyapunov function without having to choose the form of the parameter dependence. Additionally, the synthesis procedure is designed for discrete time systems, allowing digital implementation of the controller. While the LPV controller is suitable for the wind turbine problem, its performance is limited by constrained actuators, as well as persistent disturbances to the system. Therefore a model predictive controller (MPC controller) that builds on the advantages of the LPV controller is created. The MPC controller utilises future wind speed information to increase controller performance and can maintain stability in the presence of constrained actuators. The ability of both controllers to reduce fatigue loading in the drivetrain, tower and blades whilst maintaining power capture relative to a baseline is tested in simulation. The testing includes six hours of simulations using a high order, nonlinear aeroelastic model of a three-bladed, 600kW wind turbine in full-field turbulent winds. The simulation conditions include above rated, below rated, and transitional winds. The LPV controller shows overall reductions in tower, drivetrain and blade loads relative to the baseline. The MPC controller shows poor performance in below rated winds due to high errors in the prediction model. In above rated winds, the MPC controller shows the ability to reduce loads in the blades, drivetrain and tower relative to the LPV controller. Furthermore, the MPC controller shows less pitch actuator usage and maintains performance in situations that cause the LPV controller to saturate the pitch actuators and lose performance.