Improve Wind Turbine Research Articles

The transmission characteristic for the improved wind turbine gearbox

AbstractThe structure of an improved wind turbine gearbox is presented for meeting the operation of the optimized wind turbine power‐wind speed curve (P‐v curve). When the wind speed is lower than the cut‐in wind speed, the operation mode of the wind turbine is changed by the extra power, which is supplied by the motor excited source to keep the wind turbine running. Moreover, the transmission principle of the improved wind turbine gearbox is discussed. Various motor power impacts on the transmission characteristic for the improved transmission structure are investigated and results are compared with the professional software. Results indicate that as the motor power increases, the transverse vibration of sun gears and meshing forces of the low‐speed and medium‐speed planetary stages decreases. The transverse vibration for the pinion gear of the high‐speed stage enhances with the increase of the motor power. Load‐sharing coefficients of the planetary gear stages are augmented with the enlargement of the motor power. It is found that meshing forces of the torque‐implement parallel stage are increased with augmentation of the motor power.

Study on the Performance of the Wind Turbine Airfoil with Icing

If the performance of the blade was properly assessed, which would help improve wind turbine performance, wind turbine blade aerodynamics at low temperatures could severely affect the output power of the wind turbine. The research on the performance of wind turbine blade with icing which had the three different shapes was carried out. The blades flow field and the lift coefficient were got from the free stream wind whose speed was 10m/s at different angles of attack, The Influences on the flow Field and aerodynamic performance were discussed, when the ice shape changed. The results show that:1) Model 1 has the best performance, with the maximum lift coefficient of 1.2853, its stall angle of 14 degrees, and the stalling phenomenon of icing blade is postponed;2) the difference in the icing shapes has less affected on the flow field distribution and the lift coefficient at the small angle of attack, and the distribution of flow field is more sensitive to the ice shape on the upper part of the leading edge at the large angle of attack.3) Ice the irregular icing shape can cause the oscillation phenomenon for the lift coefficient at the angle of attack from 0 to 20 degree.

Determination of pitch angles and wind speeds ranges to improve wind turbine performance when using blade tip plates

In this article a wind turbine performance enhancement is studied numerically using two type of tip plates. A three dimensional finite volume code is developed to simulate the wind turbine flow field periodically at different wind speeds and pitch angles. The well-known Menter's Shear Stress Transport (kω−SST) turbulence modelling is incorporated into the code to investigate the turbulent flow field that occurs in wind turbines. Here we show that using tip plates for wind turbines performance improvement can only occur if the turbine blade pitch angle is set at the maximum output power based on the given wind speed. Otherwise, using the tip plates play negative role and reduce the wind turbine output power. This physical effect is related to the wind turbine working condition at which both the blade span-wise flow as well as the tip blade trailing vortices stay at their minimum amount.

Sensitivity analysis of the system of wind speed distributions

The fitting of empirical wind speed distributions is an important component in wind turbine energy yield assessment. Its accuracy depends on both the adequacy of the fitting function and the quality of the fitted wind speed data. Therefore, the system of wind speed distributions was recently introduced to further improve the statistical estimation of wind turbine energy yield. The system of wind speed distributions incorporates the three complement distributions Kappa, Wakeby and Burr-Generalized Extreme Value. In contrast to the progress that has been made in the statistical description of wind speed distributions, there is little research on the effects of poor quality data on the estimation of wind turbine energy yield. Therefore, the goal of this study was to evaluate the robustness of the system of wind speed distributions against typical wind speed data shortcomings such as (1) measurement errors, (2) missing data, and (3) low temporal resolution. The database were quality-controlled wind speed time series from 187 measurement stations of the German Meteorological Service located in Germany with a 10-minute temporal resolution. The investigated time series cover the period from July 2016 to December 2017. The original wind speed time series were modified by (1) rounding them to 0.5 m/s and 1 m/s steps, (2) reducing data availability to 1.0% and 0.5%, (3) reducing the temporal resolution. Afterwards, the original and the modified wind speed time series were fitted to the system of wind speed distributions. Ten goodness-of-fit metrics were applied for comparison of the original wind speed distributions with the modified distributions fitted to the system of wind speed distributions. Overall, it was found that the system of wind speed distributions is robust against common quality issues in the wind speed time series. Applying a 2.5 MW wind turbine power curve and fitting the system of wind speed distributions to integer wind speed data, the mean percentage annual energy yield error was estimated at 3.3%. Fitting the system of wind speed distributions to wind speed data with very low data availability of 0.5% of the original data, the annual energy yield over all stations was underestimated at −8.2%. The results of this investigation will help adequately addressing the biases caused by poor quality wind speed data, and thus, help to improve wind turbine energy yield assessment.

Achieving Germany’s wind energy expansion target with an improved wind turbine siting approach

The goals of this study were to develop and to evaluate wind turbine siting scenarios for achieving a share of about 40% (250 TWh/yr) wind energy in Germany’s gross electricity consumption. The scenarios were developed to quantify the influence of (1) available technology and repowering, (2) resource distribution, and (3) siting strategy on five siting suitability measures: (1) number of wind turbines, (2) cumulative installed capacity, (3) capacity factor, (4) main investment costs, and (5) distribution of wind turbines. The wind field in the analyzed hub height range was modeled by the wind speed-wind shear model on a 200 m × 200 m grid. Geographically restricted areas were considered as not suitable under all scenarios. For a better comparison of the scenarios, a novel wind turbine siting index was introduced by normalizing the suitability measures. It was found that an installed capacity of less than 100 GW and about 36,000 wind turbines are sufficient to generate 250 TWh/yr wind energy. If the current rate of wind energy expansion in Germany is maintained, this value can be achieved in the early 2030s. The results also demonstrate that inefficient wind turbine siting considerably extends the period and increases the number of required wind turbines. Against this background, the results of this study can be applied for a better coordination of wind turbine siting in Germany at different administrative levels. The methodology is portable to other countries and can be used to develop national siting strategies to achieve projected wind energy shares in the electricity mix.

Horizontal Axis Wind Turbine Blade Design Methodologies for Efficiency Enhancement—A Review

Among renewable sources of energy, wind is the most widely used resource due to its commercial acceptance, low cost and ease of operation and maintenance, relatively much less time for its realization from concept till operation, creation of new jobs, and least adverse effect on the environment. The fast technological development in the wind industry and availability of multi megawatt sized horizontal axis wind turbines has further led the promotion of wind power utilization globally. It is a well-known fact that the wind speed increases with height and hence the energy output. However, one cannot go above a certain height due to structural and other issues. Hence other attempts need to be made to increase the efficiency of the wind turbines, maintaining the hub heights to acceptable and controllable limits. The efficiency of the wind turbines or the energy output can be increased by reducing the cut-in-speed and/or the rated-speed by modifying and redesigning the blades. The problem is tackled by identifying the optimization parameters such as annual energy yield, power coefficient, energy cost, blade mass, and blade design constraints such as physical, geometric, and aerodynamic. The present paper provides an overview of the commonly used models, techniques, tools and experimental approaches applied to increase the efficiency of the wind turbines. In the present review work, particular emphasis is made on approaches used to design wind turbine blades both experimental and numerical, methodologies used to study the performance of wind turbines both experimentally and analytically, active and passive techniques used to enhance the power output from wind turbines, reduction in cut-in-speed for improved wind turbine performance, and lastly the research and development work related to new and efficient materials for the wind turbines.

Research and Development of the Wind Turbine Reliability

With the rapid development of wind power industry, the wind turbine reliability has become a hotspot in wind power research. The failure modes and research progress of wind turbine reliability both at home and abroad were analyzed. The failure modes, failure causes and detection methods of some key components in the wind turbines were summarized. Also, the frequently used methods of reliability analysis and research status of wind turbine reliability were analyzed. Following this, research focuses, methods and measures to improve wind turbine reliability were presented. We also shed light on the condition monitoring and assessment process with condition monitoring system and supervisory control and data acquisition. It is of great significance to reduce the cost of operation and maintenance and to improve the safety of wind turbines.

Physics-based data analysis for wind turbine condition monitoring

Abstract This article presents methodologies for improving wind turbine condition monitoring using physics-based data analysis techniques. The unique operating conditions of the wind turbine drivetrain are described, and the complex kinematics of the gearbox is analyzed in detail. The pros and cons of the current wind turbine condition monitoring system (CMS) are evaluated. To improve the wind turbine CMS capability, it is suggested to use linear models with unsteady excitations, instead of using nonlinear and nonstationary process models, when dealing the wind turbine dynamics response model. An analysis is undertaken of the damage excitation mechanisms cause for various components in a gearbox, especially for those associated with lower-speed shafts. Physics (mechanics)-based data analysis methods are presented for different component damage excitation mechanisms. Validation results, using the wind farm and manufacturing floor data, are reported.

Spline model for wake effect analysis: Characteristics of a single wake and its impacts on wind turbine power generation

ABSTRACTUnderstanding and quantifying the wake effect plays an important role in improving wind turbine designs and operations, as well as wind farm layout planning. The majority of the current wake effect models are physics based, but these models have a number of shortcomings. Sophisticated models based on computational fluid dynamics suffer from computational limitations and are impractical for modeling commercial-sized wind farms, whereas simplified physics-based models are generally inaccurate for wake effect quantification. Nowadays, data-driven wake effect models are gaining popularity as the data from commercially operating wind turbines become available, but this development is still in its early stages. This study contributes to the general category of data-driven wake effect modeling that makes use of actual wind turbine operational data. We propose a wake effect model based on splines with physical constraints incorporated, which sets out to estimate wake effect characteristics such as wake width and wake depth under single-wake situations. Our model is one of the first data-driven models that provides a detailed account of the wake effect. Prediction accuracy of the proposed spline model, when compared with other alternatives, also confirms the benefit of incorporating the physical constraints in the statistical estimation.

On the use of high-frequency SCADA data for improved wind turbine performance monitoring

SCADA-based condition monitoring of wind turbines facilitates the move from costly corrective repairs towards more proactive maintenance strategies. In this work, we advocate the use of high-frequency SCADA data and quantile regression to build a cost effective performance monitoring tool. The benefits of the approach are demonstrated through the comparison between state-of-the-art deterministic power curve modelling techniques and the suggested probabilistic model. Detection capabilities are compared for low and high-frequency SCADA data, providing evidence for monitoring at higher resolutions. Operational data from healthy and faulty turbines are used to provide a practical example of usage with the proposed tool, effectively achieving the detection of an incipient gearbox malfunction at a time horizon of more than one month prior to the actual occurrence of the failure.

Wind turbine noise measurements in controlled conditions

To validate and reduce the uncertainty associated with noise prediction models for wind turbines, there is a need for detailed noise measurements on wind turbines in controlled conditions. However, high-quality wind tunnel campaigns on horizontal axis wind turbine models are scarce due to the large wind tunnel size needed and consequently high associated costs. To serve this purpose, an experiment using the 4.5 -m diameter Mexico turbine was set up in the large low-speed facility of the DNW wind tunnel. An overview of the experiments is given including a selection of results. Both far field microphone as well as microphone array measurements have been performed together with unsteady force measurements on five instrumented blade sections. This allows a unique insight into the relation between acoustics and the underlying aerodynamics. Overall noise characteristics of the turbine have been determined for a variety of operational conditions by varying tip speed ratio and blade pitch angles. Scaling of the noise is studied by comparing similar combinations of tip speed ratio and pitch angle for different tip speeds. The effect of blade soiling on the noise is evaluated using roughness strips, as well as the influence of yawed or misaligned inflow on the rotor noise. A comparison of calculations using a BPM model is given indicating for which operational conditions this model suffices and for which parts the noise prediction can be improved. In summary, after years of preparation, ECN and partners have performed very successful aeroacoustic experiments in the largest wind tunnel in Europe. The comprehensive high-quality database that has been obtained will be used in the international Mexnext consortium to further improve wind turbine acoustic modeling.

Improving wind turbine efficiency with use a pseudo direct drive

Improving wind turbine efficiency with use a pseudo direct drive

Leading-edge serrations for performance improvement on a vertical-axis wind turbine at low tip-speed-ratios

The performance of vertical-axis wind turbines (VAWTs) are substantially affected by the phenomenon of dynamic stall which is induced by the variations of angle of attack of rotating blades, especially at low tip-speed-ratios (TSRs). Large and sudden torque fluctuations are observed to take place when the dynamic stall vortices, formed near the blade leading-edge, are transported downstream. At low TSRs (λTSR<4) and relatively low Reynolds number (Re<105), dynamic stall occurs periodically during the rotation of turbine blades. This results in a sharp drop in lift coefficient and therefore rotor torque and power output are essentially reduced. The purpose of the present study is to investigate the concepts for improving the power performance of a conventional H-type VAWT model by implementing sinusoidal serrations on the leading-edge of turbine blades to control the dynamic flow separation at low TSRs. A thorough numerical study has been carried out to obtain the detailed flow fields for analysis and visualization. The power output results show that the improved turbine design with the sinusoidal serration profile of the wave amplitude h=0.025c and the wavelength λs=0.33c not only increases the power generation at low TSRs, but also enhances the capability of wind energy extraction at the optimal TSR in comparison to the baseline model. The flow separation is significantly controlled in the azimuth angle ranges from 75° to 160°, where the positive torque generation is also found to be considerably increased in the improved turbine model. Counter-rotating vortex pairs are generated due to the existence of serrations, which suppress the flow separation, especially in the regions near the peak-serration sections. Additionally, the lift coefficients illustrate a delay of occurrence of dynamic stall and a notable improvement of maximum lift in the improved wind turbine model in comparison to the baseline model. The effects of Reynolds number variation also reveal that the improved model would gain more benefits in power generation at low Reynolds number compared with that at high Reynolds number. The simulated results demonstrate that the leading-edge serration strategy could be an effective solution to control the dynamic stall in the operation of VAWTs.

Fault Prediction and Diagnosis of Wind Turbine Generators Using SCADA Data

The fast-growing wind power industry faces the challenge of reducing operation and maintenance (O&amp;M) costs for wind power plants. Predictive maintenance is essential to improve wind turbine reliability and prolong operation time, thereby reducing the O&amp;M cost for wind power plants. This study presents a solution for predictive maintenance of wind turbine generators. The proposed solution can: (1) predict the remaining useful life (RUL) of wind turbine generators before a fault occurs and (2) diagnose the state of the wind turbine generator when the fault occurs. Moreover, the proposed solution implies low-deployment costs because it relies solely on the information collected from the widely available supervisory control and data acquisition (SCADA) system. Extra sensing hardware is needless. The proposed solution has been deployed and evaluated in two real-world wind power plants located in China. The experimental study demonstrates that the RUL of the generators can be predicted 18 days ahead with about an 80% prediction accuracy. When faults occur, the specific type of generator fault can be diagnosed with an accuracy of 94%.

Iterative feedback tuning of wind turbine controllers

Abstract. Traditionally, wind turbine controllers are designed using first principles or linearized or identified models. The aim of this paper is to show that with an automated, online, and model-free tuning strategy, wind turbine control performance can be significantly increased. For this purpose, iterative feedback tuning (IFT) is applied to two different turbine controllers: drivetrain damping and collective pitch control. The results, obtained by high-fidelity simulations using the NREL 5MW wind turbine, indicate significant performance improvements over baseline controllers, which were designed using classical loop-shaping techniques. It is concluded that iterative feedback tuning of turbine controllers has the potential to become a valuable tool to improve wind turbine performance.

Turbulence upstream of wind turbines: A large-eddy simulation approach to investigate the use of wind lidars

Despite the evolution of wind turbines, the way in which in-situ meteorological information is obtained has not evolved much. Wind vane and cup anemometers, installed at the turbines nacelle, right behind the blades, are still used. This near-blade monitoring does not provide any time to readjust the profile of the wind turbine, and subjects the blades and structure to wind gusts and extreme incoming wind conditions. A solution is to install wind lidar devices on the turbine's nacelle. This technique is currently under development as an alternative to traditional in-situ wind anemometry because it can measure the wind vector at substantial distances upwind. However, most used wind lidar systems are optimized for measuring within a fixed upwind range, but at what upwind distance should they interrogate the atmosphere? This work uses Large Eddy Simulations to create a realistic atmospheric flow to evaluate optimal scanning distances to learn about the incoming turbulence as a function of wind farm configuration and atmospheric stratification. A correlation model, based on a modified truncated normal distribution, has also been developed, which could be implemented within the feed-forward collective pitch control of the turbine, allowing for improved wind turbine readjustments.

Investigation of the incoming wind vector for improved wind turbine yaw-adjustment under different atmospheric and wind farm conditions

Regardless of the evolution of wind energy harvesting, the way in which turbines obtain in-situ meteorological information remains the same - i.e. using traditional wind vanes and cup anemometers installed at the turbine's nacelle, right behind the blades. As a result, misalignment with the mean wind vector is common and energy losses up to 4.6% can be experienced as well as increases in loading and structural fatigue. A solution for the near-blade monitoring is to install wind LIDAR devices on the turbines' nacelle. This technique is currently under development as an alternative to traditional in-situ wind anemometry because it can measure the wind vector at substantial distances upwind. But at what upwind distance should they interrogate the atmosphere? and, what is the optimal average time in which to learn about the incoming flow conditions? This work simulates wind fields approaching isolated wind turbines and wind turbine arrays within large wind farms using Large Eddy Simulations. The goal is to investigate the existence of an optimal upstream scanning distance and average time for wind turbines to measure the incoming wind conditions under different ambient atmospheric conditions. Results reveal no significant differences when measuring the incoming wind vector at different upstream distances, regardless of the atmospheric stratification. Within this framework a 30 min readjustment period is observed to perform the best.

EFFECTIVENESS OF BLADE TIP ON LOW SPEED HORIZONTAL AXIS WIND TURBINE PERFORMANCE

There has been an increasing demand for renewable energy in order to create a sustainable society as the non-renewable energies such as fossil fuel resources are limited. Modern wind turbines claim that they have a high efficiency in term of wind energy extraction. However, there are still having losses due to tip vortex causing to a reduction in performance. Motivated by this reason, this research aims at exploring the possibility to increase the performance of low speed small-scaled horizontal axis wind turbine with various tip devices using Computational Fluid Dynamics (CFD). Four wind turbine blades with different tip devices which consist of sword tip, swept tip, upwind winglet and downwind winglet are compared with wind turbine blade without tip device in term of CP. The application of tip device can significantly reduce induced tip vortex and improve wind turbine performance. For TSR below than 4, adding a sword tip increases CP about 7.3%, swept tip increases CP about 9.1%, upwind winglet increases CP about 1.8% and downwind winglet increases CP about 3.2%. It is observed that the best tip device for low wind speed application is swept tip as it give the highest performance increment compared to without tip device.

A New Fault Diagnosis Algorithm for PMSG Wind Turbine Power Converters under Variable Wind Speed Conditions

Although Permanent Magnet Synchronous Generator (PMSG) wind turbines (WTs) mitigate gearbox impacts, they requires high reliability of generators and converters. Statistical analysis shows that the failure rate of direct-drive PMSG wind turbines’ generators and inverters are high. Intelligent fault diagnosis algorithms to detect inverters faults is a premise for the condition monitoring system aimed at improving wind turbines’ reliability and availability. The influences of random wind speed and diversified control strategies lead to challenges for developing intelligent fault diagnosis algorithms for converters. This paper studies open-circuit fault features of wind turbine converters in variable wind speed situations through systematic simulation and experiment. A new fault diagnosis algorithm named Wind Speed Based Normalized Current Trajectory is proposed and used to accurately detect and locate faulted IGBT in the circuit arms. It is compared to direct current monitoring and current vector trajectory pattern approaches. The results show that the proposed method has advantages in the accuracy of fault diagnosis and has superior anti-noise capability in variable wind speed situations. The impact of the control strategy is also identified. Experimental results demonstrate its applicability on practical WT condition monitoring system which is used to improve wind turbine reliability and reduce their maintenance cost.

Design and Experimental Analysis of a 200W Micro Wind Turbine

Majority of the regions in India are characterized by moderate and low wind regimes. These regions have variable and gusty winds. Our low-wind energy turbine addresses this problem and is capable of providing power to millions of people not connected to the grid in low wind conditions. Our objective is to design a suitable wind turbine applicable in low speed regions extracting maximum power output. Our team aims to take on the challenge of improving wind turbine efficiencies, at low to medium wind speeds, to reduce environmental impact and encourage adoption of wind energy at domestic and commercial building rooftops and small distributed systems. Blade Element Momentum theory was adopted to find the suitable parameters at the required wind speeds. Tools like Q-Blade and X-foil were used to optimize the CAD model of the blade. A customized Wind tunnel was fabricated by the team to validate the practical results against the theoretical ones. Rapid Prototyping technique of 3-D printing was used to manufacture the blades. Final results establish a close relationship between the theoretical and experimental values.