Showing papers on "Turbine published in 2007"
TL;DR: In this paper, the authors present results from an investigation of failure statistics from four sources, i.e. two separate sources from Sweden, one from Finland, and one from Germany, revealing reliability performance of the different components within the wind turbine.
Abstract: The wind power industry has expanded greatly during the past few years, has served a growing market, and has spawned the development of larger wind turbines. Different designs and technical advances now make it possible to put wind turbines off shore. The fast expansion of the wind power market comes with problems. The new designs are not always fully tested, and the designed 20 year lifetime is typically never achieved before the next generation of turbines is erected. This paper presents results from an investigation of failure statistics from four sources, i.e. two separate sources from Sweden, one from Finland, and one from Germany. Statistics reveal reliability performance of the different components within the wind turbine. The gearbox is the most critical because downtime, per failure, is high compared to the other components in the wind power turbine. The statistical data for larger turbines also show trends toward higher, ever increasing failure frequency when compared to small turbines, which have a decreasing failure rate over the operational years.
680 citations
TL;DR: In this paper, the results of cavitation tunnel and tank tests on an 800 mm diameter model of a marine current turbine (MCT) were presented, and the results provided useful information for the hydrodynamic design of MCTs and detailed data for the validation of numerical models.
671 citations
TL;DR: In this paper, the authors proposed a control scheme that allows doubly fed induction wind generators (DFIWG) to participate effectively in system frequency regulation. But, the control strategy defined at the wind generator to supply primary frequency regulation capability exploits a combination of control of the static converters and pitch control, adjusting the rotor speed and the active power according to the deloaded optimum power extraction curve.
Abstract: This paper proposes a control scheme that allows doubly fed induction wind generators (DFIWG) to participate effectively in system frequency regulation. In this control approach, wind generators operate according to a deloaded optimum power extraction curve such that the active power provided by each wind turbine increases or decreases during system frequency changes. The control strategy defined at the wind generator to supply primary frequency regulation capability exploits a combination of control of the static converters and pitch control, adjusting the rotor speed and the active power according to the deloaded optimum power extraction curve. Results obtained in a small isolated system are presented to demonstrate the effectiveness of the approach.
571 citations
TL;DR: In this paper, an assessment on the capability of a doubly fed induction generator (DFIG) wind turbine for frequency regulation is presented, where detailed aerodynamic, structural and electrical dynamic models were used in order to enhance the inertia support from the DFIG wind turbine.
Abstract: An assessment on the capability of a doubly fed induction generator (DFIG) wind turbine for frequency regulation is presented. Detailed aerodynamic, structural and electrical dynamic models were used in this study. A control loop acting on the frequency deviation was added to the inertia contributing loop in order to enhance the inertia support from the DFIG wind turbine. The possibility of de-loading a wind turbine to provide primary and secondary frequency response was discussed. A frequency droop controller was examined where the droop is operating on the electronic torque set point below its maximum speed and is operating on the pitch demand at maximum speed. It is also shown that by reducing the generator torque set point the DFIG wind turbine can provide high frequency response.
515 citations
TL;DR: In this paper, the reliability of wind turbine components from historic German and Danish data has been analyzed using reliability analysis methods which are not only applicable to wind turbines but relate to any repairable system.
Abstract: Modern wind turbines are complex aerodynamic, mechanical and electrical machines incorporating sophisticated control systems. Wind turbines have been erected in increasing numbers in Europe, the USA and elsewhere. In Europe, Germany and Denmark have played a particularly prominent part in developing the technology, and both countries have installed large numbers of turbines. This article is concerned with understanding the historic reliability of modern wind turbines. The prime objective of the work is to extract information from existing data so that the reliability of large wind turbines can be predicted, particularly when installed offshore in the future. The article uses data collected from the Windstats survey to analyse the reliability of wind turbine components from historic German and Danish data. Windstats data have characteristics common to practical reliability surveys; for example, the number of failures is collected for each interval but the number of turbines varies in each interval. In this article, the authors use reliability analysis methods which are not only applicable to wind turbines but relate to any repairable system. Particular care is taken to compare results from the two populations to consider the validity of the data. The main purpose of the article is to discuss the practical methods of predicting large-wind-turbine reliability using grouped survey data from Windstats and to show how turbine design, turbine configuration, time, weather and possibly maintenance can affect the extracted results. Copyright © 2006 John Wiley &Sons, Ltd.
459 citations
TL;DR: In this paper, a three-bladed wind turbine with a rotor diameter of 58m was used to characterize the noise sources and to verify whether trailing edge noise from the blades was dominant.
410 citations
TL;DR: In this article, the authors show that the fractional power loss increases from 1/3 to 2/3 as the fraction of the channel cross-section spanned by the turbines increases from 0 to close to 1.
Abstract: There is an upper bound to the amount of power that can be generated by turbines in tidal channels as too many turbines merely block the flow. One condition for achievement of the upper bound is that the turbines are deployed uniformly across the channel, with all the flow through them, but this may interfere with other uses of the channel. An isolated turbine is more effective in a channel than in an unbounded flow, but the current downstream is non-uniform between the wake of the turbines and the free stream. Hence some energy is lost when these streams merge, as may occur in a long channel. We show here, for ideal turbine models, that the fractional power loss increases from 1/3 to 2/3 as the fraction of the channel cross-section spanned by the turbines increases from 0 to close to 1. In another scenario, possibly appropriate for a short channel, the speed of the free stream outside the turbine wake is controlled by separation at the channel exit. In this case, the maximum power obtainable is slightly less than proportional to the fraction of the channel cross-section occupied by turbines.
382 citations
TL;DR: In this paper, a multivariable control strategy for variable speed, variable pitch wind turbine is proposed for the above-rated power operating condition, which is realized by combining a nonlinear dynamic state feedback torque control strategy with a linear control for blade pitch angle.
360 citations
TL;DR: In this article, nine different concepts for natural gas fired power plants with CO2 capture have been investigated, and a comparison is made based on net plant efficiency and emission of CO2, where a 400MW combined cycle plant is applied as a reference case.
346 citations
TL;DR: In this article, the authors focus on the fault ride-through capability of doubly fed induction generator (DFIG) wind turbines and the ability of the DIG to protect itself without disconnection during grid faults.
332 citations
Abstract: The low-voltage ride-through capability of a 2 MW full converter wind turbine with permanent magnet synchronous generator is investigated herein. A detailed description of the system, its controller options and its behaviour when subjected to a severe voltage dip, is presented. A control scheme for the turbine that allows it to withstand severe voltage dips is designed and simulated. This control scheme emphasises the regulation of the dc-link voltage and minimisation of the drive train torque surplus. Also, the level of modelling detail required for stability analysis is analysed and discussed.
01 Jul 2007
TL;DR: In this paper, a control algorithm for wind turbines mounted on floating platforms is presented, including the tuning method (pole-placement) to ensure the desired control frequency which provides stable tower vibration modes.
Abstract: Wind turbines mounted on floating platforms is subjected to completely different and soft foundation properties, than seen for onshore wind turbines. This leads to much lower natural frequencies, related to the rigid body motion of the structure which again leads to an unfavorable coupling between tower motion and the pitch control of the turbine. The tower motion in combination with the aerodynamics and the pitch control will be poor or even negative damped which causes large transient loads if not accounted for. The reason for this low damping is shown to be caused by a too fast pitch regulation compared to the motion of the tower or in other words the lowest control-structure natural frequency must be lower than the lowest critical tower frequency. A control algorithm is presented including the tuning method (pole-placement) to ensure the desired control frequency which provides stable tower vibration modes.
TL;DR: In this article, the authors deal with the aeroelastic instabilities that have occurred and may still occur for modern commercial wind turbines: stall-induced vibrations for stall-turbines, and classical flutter for pitch-regulated turbines.
Abstract: This paper deals with the aeroelastic instabilities that have occurred and may still occur for modern commercial wind turbines: stall-induced vibrations for stall-turbines, and classical flutter for pitch-regulated turbines. A review of previous works is combined with derivations of analytical stability limits for typical blade sections that show the fundamental mechanisms of these instabilities. The risk of stall-induced vibrations is mainly related to blade airfoil characteristics, effective direction of blade vibrations and structural damping; whereas the blade tip speed, torsional blade stiffness and chordwise position of the center of gravity along the blades are the main parameters for flutter. These instability characteristics are exemplified by aeroelastic stability analyses of different wind turbines. The review of each aeroelastic instability ends with a list of current research issues that represent unsolved aeroelastic instability problems for wind turbines. Copyright © 2007 John Wiley & Sons, Ltd.
24 Jun 2007
TL;DR: In this article, the authors presented the dynamic model and control schemes of a variable speed pitch wind turbine with permanent magnet synchronous generator (PMSG) model, a pitch-angled controlled wind turbine model and a drive train model.
Abstract: The paper presents the dynamic model and control schemes of a variable speed pitch wind turbine with permanent magnet synchronous generator (PMSG). The model includes a PMSG model, a pitch-angled controlled wind turbine model and a drive train model. The drive train model uses one-mass model to represent the mechanical characteristics of the generator set. The generator model is established in the dq-synchronous rotating reference frame. The wind turbine model details the mechanism of variable speed operation of the turbine by a pitch control. The control schemes in the paper include a pitch angle control for the wind turbine and a speed control for the generator. The pitch angle control uses wind speeds and electric power output as the input signals to ensure normal operation in high wind speed. The speed control is realized through field orientation where the d-axis current is set to zero and the q-axis current is used to control the rotational speed of the generator according to the variation of wind speed. In order to verify the presented model and the control strategy, simulations with MATLAB/Simulink software have been conducted. Simulation results prove the validity of the model and the control schemes.
TL;DR: In this paper, the authors investigated the possibility of enhancing the performances of micro-gas turbines through the addition of a bottoming organic Rankine cycle which recovers the thermal power of the exhaust gases typically available in the range of 250-300°C.
TL;DR: In this paper, the authors report on the development and verification of simulation tools based on blade element momentum theory for marine current turbines, including a commercial code (GH-Tidal Bladed) and an academic in-house code (SERG-tidal).
TL;DR: In this paper, the power spectral density of the output of wind turbines provides information on the character of fluctuations in turbine output, and both 1-second and 1-hour samples are used to estimate the power spectrum of several wind farms.
01 Jul 2007
TL;DR: In this article, a large-Eddy simulation (LES) approach is used to simulate the turbine in an environment with turbulence anisotropy properties similar to the ones of the real atmosphere.
Abstract: A CFD code has been developed based on a Large-Eddy Simulation (LES) approach. The turbine is simulated by concentrated drag forces, and is placed in an environment with turbulence anisotropy properties similar to the ones of the real atmosphere. Comparisons with experimental data and with analytical correlations have been performed, and the results are found to be in good agreement with both, suggesting that LES is a potentially useful tool in the investigation of detailed wake flow.
01 Jan 2007
TL;DR: In this article, the authors describe a new research and development initiative to improve gearbox reliability in wind turbines begun at the National Renewable Energy Laboratory (NREL) in Golden, Colorado, USA.
Abstract: NOTICE The submitted manuscript has been offered by an employee of the Midwest Research Institute (MRI), a contractor of the US Government under Contract No. DE-AC36-99GO10337. Accordingly, the US Government and MRI retain a nonexclusive royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for US Government purposes. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Summary This paper describes a new research and development initiative to improve gearbox reliability in wind turbines begun at the National Renewable Energy Laboratory (NREL) in Golden, Colorado, USA. The approach involves a collaboration of NREL staff, expert consultants, and partners from the wind energy industry who have an interest in improving gearbox reliability. The membership of this collaborative is still growing as the project becomes more defined, but the goal is to include representatives ranging from the operators, owners, wind turbine manufacturers, gearbox manufacturers, bearing manufacturers, consultants, and lubrication industries. The project is envisioned to be a multi-year comprehensive testing and analysis effort. This will include complementary laboratory and field testing on a 600 to 750-kW turbine and gearbox of a configuration that exhibits reliability problems common to a broad population of turbines. The project will target deficiencies in the design process that are contributing to substantial shortfalls in service life for most designs. New design-analysis tools will be developed to model the test configuration in detail. This will include using multi-body dynamic analysis to model wind turbine loading, coupled to internal loading and deformations of the gearbox. Intellectual property conflicts will be minimized by maintaining a test configuration that does not replicate any specific manufacturer's wind turbine model precisely, but represents a common configuration.
TL;DR: In this article, the parameters of wind turbine visibility and impact at different distances from the viewer, under different lighting and atmospheric conditions and with moving or stationary blades, were established through an online survey involving an 18 turbine wind farm at three different distances (4, 8 and 12 kilometers).
01 Jan 2007
TL;DR: In this article, a model for change in turbulence intensity alone may account for increased fatigue loading in wind farms, and a method to combine the different load situations is proposed to avoid excessive safety for fatigue estimation of the structure's steel components, and nonconservatism for fibreglass components.
Abstract: (22/04/2019) Turbulence and turbulence-generated structural loading in wind turbine clusters Turbulence in terms of standard deviation of wind speed fluctuations and other flow characteristics are different in the interior of wind farms relative to the free flow and action must be taken to ensure sufficient structural sustainability of the wind turbines exposed to “wind farm flow”. The standard deviation of wind speed fluctuations is a known key parameter for both extremeand fatigue loading, and it is argued and found to be justified that a model for change in turbulence intensity alone may account for increased fatigue loading in wind farms. Changes in scale of turbulence and horizontal flow-shear also influence the dynamic response and thus fatigue loading. However, these parameters are typically – negatively or positively – correlated with the standard deviation of wind speed fluctuations, which therefore can, if need be, represent these other variables. Thus, models for spatially averaged turbulence intensity inside the wind farm and direct-wake turbulence intensity are being devised and a method to combine the different load situations is proposed. The combination of the load cases implies a weighting method involving the slope of the considered material’s Wöhler curve. In the context, this is novel and necessary to avoid excessive safety for fatigue estimation of the structure’s steel components, and nonconservatism for fibreglass components. The proposed model offers significant reductions in computational efforts in the design process. The status for the implementation of the model is that it became part of the Danish standard for wind turbine design DS 472 (2001) in August 2001 and it is part of the corresponding international standard, IEC61400-1 (2005). Also, extreme loading under normal operation for wake conditions and the efficiency of very large wind farms are discussed.
TL;DR: In this paper, the authors investigated the market penetration and share of different wind turbine concepts during the years 1995-2004, a period that represents the maturational era of the modern wind power industry.
Abstract: The aim of this article is to investigate the market penetration and share of different wind turbine concepts during the years 1995–2004, a period that represents the maturational era of the modern wind power industry. A detailed overview is given based on suppliers' market data and concept evaluation for each individual wind turbine type sold by the Top Ten suppliers over the selected decade. The investigation is processing information on approximately 160 wind turbine types from 22 different manufacturers that have featured in the Top Ten list of wind turbine suppliers during 1995–2004. The analysis is based on comprehensive data covering approximately 97% of the cumulative wind power installed worldwide at the end of 2004. The article also provides an overall perspective on contemporary wind turbine concepts, classified with respect to both their speed control ability and power control type. Current and future trends for wind turbine concepts are discussed. Copyright © 2006 John Wiley &Sons, Ltd.
TL;DR: In this article, a detailed transformation procedure is presented from six-mass drive train model to two-mass model, which can be used in the analysis of transient stability simulation with sufficient accuracy.
Abstract: A huge number of wind generators are going to be connected with the existing network in the near future. Therefore it is necessary to analyse the transient stability of power systems, including wind turbine generator systems (WTGS). It has already been reported that one-mass or lumped model of wind turbine system is insufficient to analyse the transient behaviour of WTGS. It has also been reported that for the precise transient analysis of WTGS, a six-mass drive train model is needed. The reduced order models (three-mass and two-mass) have also been adopted so far for transient behaviour analysis. But the transient stability analysis of using six-mass, three-mass and two-mass drive train models has not been reported sufficiently so far in the literature. The authors have conducted an analysis using these methods. First, a detailed transformation procedure is presented from six-mass drive train model to two-mass model, which can be used in the analysis of transient stability simulation with sufficient accuracy. It is then determined which drive train model is appropriate for transient stability analysis of grid-connected WTGS. The effects of drive train parameters (such as inertia constant, spring constant and damping constant) on stability are examined using the above mentioned types of drive train models. Moreover, different types of symmetrical and asymmetrical faults at different wind generator power levels are considered in the simulation analyses with and without considering damping constants in six-mass, three-mass and two-mass shaft models. Considering the simulation results, it can be concluded that two-mass shaft model is sufficient for the transient stability analysis of WTGS.
TL;DR: In this paper, a study has been carried out on the power, thrust and cavitation characteristics of a 1/20th scale model of a possible 16 m diameter horizontal axis tidal turbine.
TL;DR: In this article, the capability of voltage-source converters (VSCs) to control the real power output of wind turbine generators (WTGs) can be applied to smooth power fluctuations due to wind turbulence.
Abstract: This paper shows that the capability of voltage-source converters (VSCs) to control the real power output of wind turbine generators (WTGs) can be applied to smooth power fluctuations due to wind turbulence. The paper calls attention to instability that can arise from: 1) the wind turbine itself and 2) the doubly fed induction generator (DFIG). The paper presents GP/V(s) to characterize the dynamic behavior of WTGs.
TL;DR: In this article, a series dynamic braking resistor (SDBR) is proposed to dissipate active power and boost generator voltage, potentially displacing the need for pitch control and dynamic reactive power compensation.
Abstract: Fault ride-through (FRT) is required for large wind farms in most power systems. Fixed speed wind turbines (FSWTs) are a diminishing but significant sector in the fast-growing wind turbine (WT) market. State-of-art techniques applied to meet grid requirements for FSWT wind farms are blade pitching and dynamic reactive power compensation (RPC). Blade pitching is constrained by the onerous mechanical loads imposed on a wind turbine during rapid power restoration. Dynamic RPC is constrained by its high capital cost. These present technologies can therefore be limiting, especially when connecting to smaller power systems. A novel alternative technology is proposed that inserts series resistance into the generation circuit. The series dynamic braking resistor (SDBR) dissipates active power and boosts generator voltage, potentially displacing the need for pitch control and dynamic RPC. This paper uses a representative wind farm model to study the beneficial effect of SDBR compared to dynamic RPC. This is achieved by quasi-steady-state characterization and transient FRT stability simulations. The analysis shows that SDBR can substantially improve the FRT performance of a FSWT wind farm. It also shows that a small resistance, inserted for less than one
TL;DR: In this article, a model for aerodynamic lift of wind turbine profiles under dynamic stall conditions is presented, where the model combines memory delay effects under attached flow with reduced lift due to flow separation.
TL;DR: In this paper, a component-based modeling methodology for turbocharged engines is described and applied, and new models for the compressor efficiency, compressor flow, and turbine flow are developed.
Abstract: A component based modeling methodology for turbocharged engines is described and applied. Several component models are compiled and reviewed. In addition new models are developed for the compressor efficiency, compressor flow, and turbine flow. Two application examples are finally given where the modeling methodology and the component models have been used. The applications are, firstly, observer design and air/fuel ratio control of SI engines and, secondly, control design of DI engines with VGT and EGR.
01 Jul 2007
TL;DR: In this article, the rotor speed and aerodynamic torque are estimated by a combined state and input observer, and the measured pitch angle is then used to calculate the effective wind speed by an inversion of a static aerodynamic model.
Abstract: The wind speed has a huge impact on the dynamic response of wind turbine. Because of this, many control algorithms use a measure of the wind speed to increase performance, e.g. by gain scheduling and feed forward. Unfortunately, no accurate measurement of the effective wind speed is online available from direct measurements, which means that it must be estimated in order to make such control methods applicable in practice. In this paper a new method is presented for the estimation of the effective wind speed. First, the rotor speed and aerodynamic torque are estimated by a combined state and input observer. These two variables combined with the measured pitch angle is then used to calculate the effective wind speed by an inversion of a static aerodynamic model.
TL;DR: In this article, a unique axial-flux permanent-magnet synchronous generator (AFPMSG) is presented for both vertical-axis and horizontal-axis wind turbine generation systems.
Abstract: This paper presents a unique axial-flux permanent-magnet synchronous generator (AFPMSG), which is suitable for both vertical-axis and horizontal-axis wind turbine generation systems. An outer-rotor design facilitates direct coupling of the generator to the wind turbine, while a coreless armature eliminates the magnetic pull between the stationary and moving parts. The design and construction features of the AFPMSG are reviewed. The flux-density distribution is studied, with the aid of a finite element software package, in order to predict the generated e.m.f. waveform. The performance equations of the AFPMSG are derived, and the condition for maximum efficiency is deduced, for both constant-speed and variable-speed operations. The experimental results, in general, confirm the theory developed