Energies

Research

Jump to: Review

4664 KiB

Open AccessArticle

A Novel Multi-Point Excitation Fatigue Testing Method for Wind Turbine Rotor Blades

by Zujin Pan and Jianzhong Wu

Energies 2017, 10(7), 1058; https://doi.org/10.3390/en10071058 - 21 Jul 2017

Cited by 6 | Viewed by 5025

Abstract

Wind turbine blades have to withstand the rigorous test of 20–25 years of service. Fatigue testing is an accurate method used to verify blade reliability. Multi-point excitation could better fit the fatigue damage distribution, which reduces the power output of a single exciter [...] Read more.

Wind turbine blades have to withstand the rigorous test of 20–25 years of service. Fatigue testing is an accurate method used to verify blade reliability. Multi-point excitation could better fit the fatigue damage distribution, which reduces the power output of a single exciter and saves testing energy consumption. The amplitude, phase, and frequency characteristics of the fatigue test system and, moreover, the relationship between the excitation force, damping, and the amplitude variation of the blade, are analyzed by the Lagrangian equation and the finite element simulation method. The full-scale fatigue test of an equivalent full cycle life in the flapwise direction is carried out by multi-excitation. When the frequency and phase of the multi-point exciters are consistent, the maximum vibration effect can be exerted. When the phase difference of the dual exciters is 180°, the vibration effect produced by the dual exciters can be equivalent to each other. The blade amplitude is proportional to excitation forces, while inversely proportional to the damping ratio. The bending moment deviation of the blade is controlled within 9.2%; moreover, the energy consumption is 40% lower than that of the single-point excitation. The use of multi-point excitation allows loading the blade with high precision, stable operation, and low cost, which provides the theoretical and experimental basis for the fatigue test of large wind turbine blades. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

3181 KiB

Open AccessArticle

A Flexible Maximum Power Point Tracking Control Strategy Considering Both Conversion Efficiency and Power Fluctuation for Large-inertia Wind Turbines

by Hongmin Meng, Tingting Yang, Ji-zhen Liu and Zhongwei Lin

Energies 2017, 10(7), 939; https://doi.org/10.3390/en10070939 - 6 Jul 2017

Cited by 10 | Viewed by 5205

Abstract

In wind turbine control, maximum power point tracking (MPPT) control is the main control mode for partial-load regimes. Efficiency potentiation of energy conversion and power smoothing are both two important control objectives in partial-load regime. However, on the one hand, low power fluctuation [...] Read more.

In wind turbine control, maximum power point tracking (MPPT) control is the main control mode for partial-load regimes. Efficiency potentiation of energy conversion and power smoothing are both two important control objectives in partial-load regime. However, on the one hand, low power fluctuation signifies inefficiency of energy conversion. On the other hand, enhancing efficiency may increase output power fluctuation as well. Thus the two objectives are contradictory and difficult to balance. This paper proposes a flexible MPPT control framework to improve the performance of both conversion efficiency and power smoothing, by adaptively compensating the torque reference value. The compensation was determined by a proposed model predictive control (MPC) method with dynamic weights in the cost function, which improved control performance. The computational burden of the MPC solver was reduced by transforming the cost function representation. Theoretical analysis proved the good stability and robustness. Simulation results showed that the proposed method not only kept efficiency at a high level, but also reduced power fluctuations as much as possible. Therefore, the proposed method could improve wind farm profits and power grid reliability. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

2332 KiB

Open AccessArticle

Integration of Degradation Processes in a Strategic Offshore Wind Farm O&M Simulation Model

by Thomas Michael Welte, Iver Bakken Sperstad, Espen Høegh Sørum and Magne Lorentzen Kolstad

Energies 2017, 10(7), 925; https://doi.org/10.3390/en10070925 - 4 Jul 2017

Cited by 11 | Viewed by 6384

Abstract

Decision support models for offshore wind farm operation and maintenance (O&M) are required to represent the failure behavior of wind turbine components. Detailed degradation modelling is already incorporated in models for specific components and applications. However, component degradation is only one of many [...] Read more.

Decision support models for offshore wind farm operation and maintenance (O&M) are required to represent the failure behavior of wind turbine components. Detailed degradation modelling is already incorporated in models for specific components and applications. However, component degradation is only one of many effects that must be captured in high-level strategic decision support models that simulate entire wind farms. Thus, for practical applications, a trade-off is needed between detailed degradation modelling and the level of simplicity of input data representation. To this end, this paper discusses two alternative approaches for taking into account component degradation processes in strategic offshore wind farm O&M simulation models: (1) full integration of the degradation process in the O&M simulation model; and (2) loose integration where the degradation process is translated into simplified input to the O&M model. As a proof-of-concept, a Markov process for blade degradation has been considered. Simulations using the NOWIcob O&M model show that the difference between full and loose integration is small in terms of aggregated output parameters such as average wind turbine availability and O&M costs. Although loose integration models some effects less accurately than full integration, the former is more flexible and convenient, and the accuracy is for most purposes sufficient for such O&M models. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

9029 KiB

Open AccessArticle

Increased Wind Energy Yield and Grid Utilisation with Continuous Feed-In Management

by Clemens Jauch, Arne Gloe, Sebastian Hippel and Henning Thiesen

Energies 2017, 10(7), 870; https://doi.org/10.3390/en10070870 - 28 Jun 2017

Cited by 6 | Viewed by 4587

Abstract

This paper presents a study to assess how wind turbines could increase their energy yield when their grid connection point is not strong enough for the rated power. It is state of the art that in such situations grid operators impose feed-in management [...] Read more.

This paper presents a study to assess how wind turbines could increase their energy yield when their grid connection point is not strong enough for the rated power. It is state of the art that in such situations grid operators impose feed-in management on the affected wind turbines, i.e., the maximum power is limited. For this study a 5 MW wind turbine is introduced in a small grid that has only limited power transfer capabilities to the upstream power system. Simulations of one particular day are conducted with the electric load, the temperature, and the wind speed as measured on that day. This simulation is conducted twice: once with the 5 MW wind turbine controlled with conventional feed-in management, and a second time when its power is controlled flexibly, i.e., with continuous feed-in management. The results of these two simulations are compared in terms of grid performance, and in terms of mechanical stress on the 5 MW wind turbine. Finally, the conclusion can be drawn that continuous feed-in management is clearly superior to conventional feed-in management. It exhibits much better performance in the grid in terms of energy yield and also in terms of constancy of voltage and temperature of grid equipment. Although it causes somewhat more frequent stress for the wind turbine, the maximum stress level is not increased. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

479 KiB

Open AccessArticle

Data–Driven Fault Diagnosis of a Wind Farm Benchmark Model

by Silvio Simani, Paolo Castaldi and Saverio Farsoni

Energies 2017, 10(7), 866; https://doi.org/10.3390/en10070866 - 28 Jun 2017

Cited by 13 | Viewed by 5273

Abstract

The fault diagnosis of wind farms has been proven to be a challenging task, and motivates the research activities carried out through this work. Therefore, this paper deals with the fault diagnosis of a wind park benchmark model, and it considers viable solutions [...] Read more.

The fault diagnosis of wind farms has been proven to be a challenging task, and motivates the research activities carried out through this work. Therefore, this paper deals with the fault diagnosis of a wind park benchmark model, and it considers viable solutions to the problem of earlier fault detection and isolation. The design of the fault indicator involves data-driven approaches, as they can represent effective tools for coping with poor analytical knowledge of the system dynamics, noise, uncertainty, and disturbances. In particular, the proposed data-driven solutions rely on fuzzy models and neural networks that are used to describe the strongly nonlinear relationships between measurement and faults. The chosen architectures rely on nonlinear autoregressive with exogenous input models, as they can represent the dynamic evolution of the system over time. The developed fault diagnosis schemes are tested by means of a high-fidelity benchmark model that simulates the normal and the faulty behaviour of a wind farm installation. The achieved performances are also compared with those of a model-based approach relying on nonlinear differential geometry tools. Finally, a Monte-Carlo analysis validates the robustness and reliability of the proposed solutions against typical parameter uncertainties and disturbances. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

2027 KiB

Open AccessArticle

Five Megawatt Wind Turbine Power Output Improvements by Passive Flow Control Devices

by Unai Fernandez-Gamiz, Ekaitz Zulueta, Ana Boyano, Igor Ansoategui and Irantzu Uriarte

Energies 2017, 10(6), 742; https://doi.org/10.3390/en10060742 - 24 May 2017

Cited by 53 | Viewed by 7059

Abstract

The effects of two types of flow control devices, vortex generators (VGs) and Gurney flaps (GFs), on the power output performance of a multi-megawatt horizontal axis wind turbine is presented. To that end, an improved blade element momentum (BEM)-based solver has been developed [...] Read more.

The effects of two types of flow control devices, vortex generators (VGs) and Gurney flaps (GFs), on the power output performance of a multi-megawatt horizontal axis wind turbine is presented. To that end, an improved blade element momentum (BEM)-based solver has been developed and BEM-based computations have been carried out on the National Renewable Energy Laboratory (NREL) 5 MW baseline wind turbine. The results obtained from the clean wind turbine are compared with the ones obtained from the wind turbine equipped with the flow control devices. A significant increase in the average wind turbine power output has been found for all of the flow control device configurations and for the wind speed realizations studied in the present work. Furthermore, a best configuration case is proposed which has the largest increase of the average power output. In that case, increments on the average power output of 10.4% and 3.5% have been found at two different wind speed realizations. The thrust force and bending moment in the root of the blade have also been determined and compared with the values of the clean wind turbine. A residual increase in the bending moment of less than 1% has been found. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

7320 KiB

Open AccessArticle

Coordinated Control Strategy for a Hybrid Wind Farm with DFIG and PMSG under Symmetrical Grid Faults

by Jiawei Li, Jun Yao, Xin Zeng, Ruikuo Liu, Depeng Xu and Caisheng Wang

Energies 2017, 10(5), 669; https://doi.org/10.3390/en10050669 - 11 May 2017

Cited by 14 | Viewed by 5863

Abstract

This paper presents a coordinated control strategy for a hybrid wind farm with doubly-fed induction generator (DFIG)- and direct-driven permanent-magnet synchronous generator (PMSG)-based wind turbines under symmetrical grid faults. The proposed low-voltage ride-through (LVRT) strategy is based on a novel current allocation principle [...] Read more.

This paper presents a coordinated control strategy for a hybrid wind farm with doubly-fed induction generator (DFIG)- and direct-driven permanent-magnet synchronous generator (PMSG)-based wind turbines under symmetrical grid faults. The proposed low-voltage ride-through (LVRT) strategy is based on a novel current allocation principle and is implemented for individual DFIG- or PMSG-based wind turbines. No communication equipment between different wind power generators is required. By monitoring the local voltages and active power outputs of the corresponding wind generators, the proposed control strategy can control the hybrid wind farm to provide the maximum reactive power to support the grid voltage during a symmetrical grid fault. As a result, the reduction in the active power output from the hybrid wind farm can be decreased, which also helps avoid generator over-speed issues and supply active power support for the power grid. In addition, the reactive current upper limits of DFIG- and PMSG-based sub-wind farms are investigated by considering different active power outputs and different grid voltage dip depths, and the feasible regions of the two types of sub-wind farms for meeting the LVRT requirements are further studied. Finally, the effectiveness of the proposed coordinated LVRT control strategy for the hybrid wind farm is validated by simulation and experimental results. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

1090 KiB

Open AccessArticle

Bayesian Estimation of Remaining Useful Life for Wind Turbine Blades

by Jannie S. Nielsen and John D. Sørensen

Energies 2017, 10(5), 664; https://doi.org/10.3390/en10050664 - 10 May 2017

Cited by 61 | Viewed by 6717

Abstract

To optimally plan maintenance of wind turbine blades, knowledge of the degradation processes and the remaining useful life is essential. In this paper, a method is proposed for calibration of a Markov deterioration model based on past inspection data for a range of [...] Read more.

To optimally plan maintenance of wind turbine blades, knowledge of the degradation processes and the remaining useful life is essential. In this paper, a method is proposed for calibration of a Markov deterioration model based on past inspection data for a range of blades, and updating of the model for a specific wind turbine blade, whenever information is available from inspections and/or condition monitoring. Dynamic Bayesian networks are used to obtain probabilities of inspection outcomes for a maximum likelihood estimation of the transition probabilities in the Markov model, and are used again when updating the model for a specific blade using observations. The method is illustrated using indicative data from a database containing data from inspections of wind turbine blades. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

1031 KiB

Open AccessArticle

Determination of the Most Suitable Technology Transfer Strategy for Wind Turbines Using an Integrated AHP-TOPSIS Decision Model

by A. Dinmohammadi and M. Shafiee

Energies 2017, 10(5), 642; https://doi.org/10.3390/en10050642 - 6 May 2017

Cited by 54 | Viewed by 6850

Abstract

The high-speed development of industrial products and goods in the world has caused “technology” to be considered as a crucial competitive advantage for most large organizations. In recent years, developing countries have considerably tended to promote their technological and innovative capabilities through importing [...] Read more.

The high-speed development of industrial products and goods in the world has caused “technology” to be considered as a crucial competitive advantage for most large organizations. In recent years, developing countries have considerably tended to promote their technological and innovative capabilities through importing high-tech equipment owned and operated by developed countries. There are currently a variety of solutions to transfer a particular technology from a developed country. The selection of the most profitable technology transfer strategy is a very complex decision-making problem for technology importers as it involves different technical, environmental, social, and economic aspects. In this study, a hybrid multiple-criteria decision making (MCDM) model based on the analytic hierarchy process (AHP) and the technique for order of preference by similarity to ideal solution (TOPSIS) is proposed to evaluate and prioritise various technology transfer strategies for wind turbine systems. For this purpose, a number of criteria and sub-criteria are defined from the viewpoint of wind energy investors, wind turbine manufacturers, and wind farm operators. The relative importance of criteria and sub-criteria with respect to the ultimate goal are computed using the eigenvalue method and then, the technology transfer alternatives are ranked based on their relative closeness to the ideal solution. The model is finally applied to determine the most suitable wind turbine technology transfer strategy among four options of reverse engineering, technology skills training, turn-key contracts, and technology licensing for the renewable energy sector of Iran, and the results are compared with those obtained by classical decision-making models. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

3350 KiB

Open AccessArticle

A Comparison Study between Two MPPT Control Methods for a Large Variable-Speed Wind Turbine under Different Wind Speed Characteristics

by Dongran Song, Jian Yang, Mei Su, Anfeng Liu, Yao Liu and Young Hoon Joo

Energies 2017, 10(5), 613; https://doi.org/10.3390/en10050613 - 1 May 2017

Cited by 28 | Viewed by 5247

Abstract

Variable speed wind turbines (VSWTs) usually adopt a maximum power point tracking (MPPT) method to optimize energy capture performance. Nevertheless, obtained performance offered by different MPPT methods may be affected by the impact of wind turbine (WT)’s inertia and wind speed characteristics and [...] Read more.

Variable speed wind turbines (VSWTs) usually adopt a maximum power point tracking (MPPT) method to optimize energy capture performance. Nevertheless, obtained performance offered by different MPPT methods may be affected by the impact of wind turbine (WT)’s inertia and wind speed characteristics and it needs to be clarified. In this paper, the tip speed ratio (TSR) and optimal torque (OT) methods are investigated in terms of their performance under different wind speed characteristics on a 1.5 MW wind turbine model. To this end, the TSR control method based on an effective wind speed estimator and the OT control method are firstly presented. Then, their performance is investigated and compared through simulation test results under different wind speeds using Bladed software. Comparison results show that the TSR control method can capture slightly more wind energy at the cost of high component loads than the other one under all wind conditions. Furthermore, it is found that both control methods present similar trends of power reduction that is relevant to mean wind speed and turbulence intensity. From the obtained results, we demonstrate that, to further improve MPPT capability of large VSWTs, other advanced control methods using wind speed prediction information need to be addressed. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

10079 KiB

Open AccessArticle

Aerodynamic Analysis of a Helical Vertical Axis Wind Turbine

by Qian Cheng, Xiaolan Liu, Ho Seong Ji, Kyung Chun Kim and Bo Yang

Energies 2017, 10(4), 575; https://doi.org/10.3390/en10040575 - 22 Apr 2017

Cited by 45 | Viewed by 12701

Abstract

Vertical axis wind turbines (VAWTs) are gradually receiving more and more interest due to their lower sensitivity to the yawed wind direction. Compared with straight blades VAWT, blades with a certain helicity show a better aerodynamic performance and less noise emission. Nowadays computational [...] Read more.

Vertical axis wind turbines (VAWTs) are gradually receiving more and more interest due to their lower sensitivity to the yawed wind direction. Compared with straight blades VAWT, blades with a certain helicity show a better aerodynamic performance and less noise emission. Nowadays computational fluid dynamics technology is frequently applied to VAWTs and gives results that can reflect real flow phenomena. In this paper, a 2D flow field simulation of a helical vertical axis wind turbine (HVAWT) with four blades has been carried out by means of a large eddy simulation (LES). The power output and fluctuation at each azimuthal position are studied with different tip speed ratio (TSR). The result shows that the variation of angle of attack (AOA) and blade-wake interaction under different TSR conditions are the two main reasons for the effects of TSR on power output. Furthermore, in order to understand the characteristics of the HVAWT along the spanwise direction, the 3D full size flow field has also been studied by the means of unsteady Reynold Averaged Navier-Stokes (U-RANS) and 3D effects on the turbine performance can be observed by the spanwise pressure distribution. It shows that tip vortex near blade tips and second flow in the spanwise direction also play a major role on the performance of VAWTs. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

2005 KiB

Open AccessArticle

Signal-Based Gas Leakage Detection for Fluid Power Accumulators in Wind Turbines

by Jesper Liniger, Nariman Sepehri, Mohsen Soltani and Henrik C. Pedersen

Energies 2017, 10(3), 331; https://doi.org/10.3390/en10030331 - 8 Mar 2017

Cited by 12 | Viewed by 4737

Abstract

This paper describes the development and application of a signal-based fault detection method for identifying gas leakage in hydraulic accumulators used in wind turbines [...] Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Graphical abstract

12622 KiB

Open AccessArticle

A Novel Parametric Modeling Method and Optimal Design for Savonius Wind Turbines

by Baoshou Zhang, Baowei Song, Zhaoyong Mao, Wenlong Tian, Boyang Li and Bo Li

Energies 2017, 10(3), 301; https://doi.org/10.3390/en10030301 - 3 Mar 2017

Cited by 59 | Viewed by 11281

Abstract

Under the inspiration of polar coordinates, a novel parametric modeling and optimization method for Savonius wind turbines was proposed to obtain the highest power output, in which a quadratic polynomial curve was bent to describe a blade. Only two design parameters are needed [...] Read more.

Under the inspiration of polar coordinates, a novel parametric modeling and optimization method for Savonius wind turbines was proposed to obtain the highest power output, in which a quadratic polynomial curve was bent to describe a blade. Only two design parameters are needed for the shape-complicated blade. Therefore, this novel method reduces sampling scale. A series of transient simulations was run to get the optimal performance coefficient (power coefficient C p) for different modified turbines based on computational fluid dynamics (CFD) method. Then, a global response surface model and a more precise local response surface model were created according to Kriging Method. These models defined the relationship between optimization objective Cp and design parameters. Particle swarm optimization (PSO) algorithm was applied to find the optimal design based on these response surface models. Finally, the optimal Savonius blade shaped like a “hook” was obtained. Cm (torque coefficient), Cp and flow structure were compared for the optimal design and the classical design. The results demonstrate that the optimal Savonius turbine has excellent comprehensive performance. The power coefficient Cp is significantly increased from 0.247 to 0.262 (6% higher). The weight of the optimal blade is reduced by 17.9%. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

2562 KiB

Open AccessArticle

Investigating How an Artificial Neural Network Model Can Be Used to Detect Added Mass on a Non-Rotating Beam Using Its Natural Frequencies: A Possible Application for Wind Turbine Blade Ice Detection

by Sudhakar Gantasala, Jean-Claude Luneno and Jan-Olov Aidanpää

Energies 2017, 10(2), 184; https://doi.org/10.3390/en10020184 - 7 Feb 2017

Cited by 20 | Viewed by 8049

Abstract

Structures vibrate with their natural frequencies when disturbed from their equilibrium position. These frequencies reduce when an additional mass accumulates on their structures, like ice accumulation on wind turbines installed in cold climate sites. The added mass has two features: the location and [...] Read more.

Structures vibrate with their natural frequencies when disturbed from their equilibrium position. These frequencies reduce when an additional mass accumulates on their structures, like ice accumulation on wind turbines installed in cold climate sites. The added mass has two features: the location and quantity of mass. Natural frequencies of the structure reduce differently depending on these two features of the added mass. In this work, a technique based on an artificial neural network (ANN) model is proposed to identify added mass by training the neural network with a dataset of natural frequencies of the structure calculated using different quantities of the added mass at different locations on the structure. The proposed method is demonstrated on a non-rotating beam model fixed at one end. The length of the beam is divided into three zones in which different added masses are considered, and its natural frequencies are calculated using a finite element model of the beam. ANN is trained with this dataset of natural frequencies of the beam as an input and corresponding added masses used in the calculations as an output. ANN approximates the non-linear relationship between these inputs and outputs. An experimental setup of the cantilever beam is fabricated, and experimental modal analysis is carried out considering a few added masses on the beam. The frequencies estimated in the experiments are given as an input to the trained ANN model, and the identified masses are compared against the actual masses used in the experiments. These masses are identified with an error that varies with the location and the quantity of added mass. The reason for these errors can be attributed to the unaccounted stiffness variation in the beam model due to the added mass while generating the dataset for training the neural network. Therefore, the added masses are roughly estimated. At the end of the paper, an application of the current technique for detecting ice mass on a wind turbine blade is studied. A neural network model is designed and trained with a dataset of natural frequencies calculated using the finite element model of the blade considering different ice masses. The trained network model is tested to identify ice masses in four test cases that considers random mass distributions along the blade. The neural network model is able to roughly estimate ice masses, and the error reduces with increasing ice mass on the blade. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

5739 KiB

Open AccessArticle

Multi-Objective Aerodynamic and Structural Optimization of Horizontal-Axis Wind Turbine Blades

by Jie Zhu, Xin Cai and Rongrong Gu

Energies 2017, 10(1), 101; https://doi.org/10.3390/en10010101 - 15 Jan 2017

Cited by 21 | Viewed by 8327

Abstract

A procedure based on MATLAB combined with ANSYS is presented and utilized for the multi-objective aerodynamic and structural optimization of horizontal-axis wind turbine (HAWT) blades. In order to minimize the cost of energy (COE) and improve the overall performance of the blades, materials [...] Read more.

A procedure based on MATLAB combined with ANSYS is presented and utilized for the multi-objective aerodynamic and structural optimization of horizontal-axis wind turbine (HAWT) blades. In order to minimize the cost of energy (COE) and improve the overall performance of the blades, materials of carbon fiber reinforced plastic (CFRP) combined with glass fiber reinforced plastic (GFRP) are applied. The maximum annual energy production (AEP), the minimum blade mass and the minimum blade cost are taken as three objectives. Main aerodynamic and structural characteristics of the blades are employed as design variables. Various design requirements including strain, deflection, vibration and buckling limits are taken into account as constraints. To evaluate the aerodynamic performances and the structural behaviors, the blade element momentum (BEM) theory and the finite element method (FEM) are applied in the procedure. Moreover, the non-dominated sorting genetic algorithm (NSGA) II, which constitutes the core of the procedure, is adapted for the multi-objective optimization of the blades. To prove the efficiency and reliability of the procedure, a commercial 1.5 MW HAWT blade is used as a case study, and a set of trade-off solutions is obtained. Compared with the original scheme, the optimization results show great improvements for the overall performance of the blade. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

11428 KiB

Open AccessArticle

Effect on Torque and Thrust of the Pointed Tip Shape of a Wind Turbine Blade

by Kyoungsoo Lee, Shrabanti Roy, Ziaul Huque, Raghava Kommalapati and SangEul Han

Energies 2017, 10(1), 79; https://doi.org/10.3390/en10010079 - 11 Jan 2017

Cited by 8 | Viewed by 8621

Abstract

This paper presents the effect of the tip shape of a wind turbine blade on aerodynamic forces, including the effects of separation, transition and stall. A National Renewable Energy Laboratory (NREL) Phase-VI wind turbine blade was used, in which the shape of the [...] Read more.

This paper presents the effect of the tip shape of a wind turbine blade on aerodynamic forces, including the effects of separation, transition and stall. A National Renewable Energy Laboratory (NREL) Phase-VI wind turbine blade was used, in which the shape of the tip was modified to a pointed tip. Computational fluid dynamics (CFD) simulations were employed for the analysis and the results were compared with the original NREL blade CFD and experimental data using ANSYS CFX (Ansys Inc., Delaware, PA, USA). To predict the separation and separation-induced transition on both near wall and far away, the shear-stress-transport (SST) Gamma-Theta turbulent model was used. The stall onset of a 20° angle of attack and its effects were also analyzed and presented. The value of torque with the pointed tip blade was found to be 3%–8% higher than the original NREL blade showing the benefit of the pointed tip. Normal force coefficient is lower at the tip for the pointed tip blade, which results in lower deformation of the blade. It was found that the pointed-tip blade is more efficient in terms of generating torque than the original NREL Phase-VI blade in the dynamic stall region of 10–15 m/s wind speeds. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

10155 KiB

Open AccessArticle

Theoretical Analysis of Shrouded Horizontal Axis Wind Turbines

by Tariq Abdulsalam Khamlaj and Markus Peer Rumpfkeil

Energies 2017, 10(1), 38; https://doi.org/10.3390/en10010038 - 1 Jan 2017

Cited by 34 | Viewed by 9638

Abstract

Numerous analytical studies for power augmentation systems can be found in the literature with the goal to improve the performance of wind turbines by increasing the energy density of the air at the rotor. All methods to date are only concerned with the [...] Read more.

Numerous analytical studies for power augmentation systems can be found in the literature with the goal to improve the performance of wind turbines by increasing the energy density of the air at the rotor. All methods to date are only concerned with the effects of a diffuser as the power augmentation, and this work extends the semi-empirical shrouded wind turbine model introduced first by Foreman to incorporate a converging-diverging nozzle into the system. The analysis is based on assumptions and approximations of the conservation laws to calculate optimal power coefficients and power extraction, as well as augmentation ratios. It is revealed that the power enhancement is proportional to the mass stream rise produced by the nozzle diffuser-augmented wind turbine (NDAWT). Such mass flow rise can only be accomplished through two essential principles: the increase in the area ratios and/or by reducing the negative back pressure at the exit. The thrust coefficient for optimal power production of a conventional bare wind turbine is known to be 8/9, whereas the theoretical analysis of the NDAWT predicts an ideal thrust coefficient either lower or higher than 8/9 depending on the back pressure coefficient at which the shrouded turbine operates. Computed performance expectations demonstrate a good agreement with numerical and experimental results, and it is demonstrated that much larger power coefficients than for traditional wind turbines are achievable. Lastly, the developed model is very well suited for the preliminary design of a shrouded wind turbine where typically many trade-off studies need to be conducted inexpensively. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

4217 KiB

Open AccessArticle

Prognosis of the Remaining Useful Life of Bearings in a Wind Turbine Gearbox

by Wei Teng, Xiaolong Zhang, Yibing Liu, Andrew Kusiak and Zhiyong Ma

Energies 2017, 10(1), 32; https://doi.org/10.3390/en10010032 - 31 Dec 2016

Cited by 52 | Viewed by 14040

Abstract

Predicting the remaining useful life (RUL) of critical subassemblies can provide an advanced maintenance strategy for wind turbines installed in remote regions. This paper proposes a novel prognostic approach to predict the RUL of bearings in a wind turbine gearbox. An artificial neural [...] Read more.

Predicting the remaining useful life (RUL) of critical subassemblies can provide an advanced maintenance strategy for wind turbines installed in remote regions. This paper proposes a novel prognostic approach to predict the RUL of bearings in a wind turbine gearbox. An artificial neural network (NN) is used to train data-driven models and to predict short-term tendencies of feature series. By combining the predicted and training features, a polynomial curve reflecting the long-term degradation process of bearings is fitted. Through solving the intersection between the fitted curve and the pre-defined threshold, the RUL can be deduced. The presented approach is validated by an operating wind turbine with a faulty bearing in the gearbox. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

3920 KiB

Open AccessArticle

Understanding Inertial Response of Variable-Speed Wind Turbines by Defined Internal Potential Vector

by Lei Shang, Jiabing Hu, Xiaoming Yuan and Yongning Chi

Energies 2017, 10(1), 22; https://doi.org/10.3390/en10010022 - 25 Dec 2016

Cited by 30 | Viewed by 8060

Abstract

With the rapid development of wind power generation, the inertial response of wind turbines (WTs) has become a topic of wide concern recently, due to its influence on grid frequency dynamics and stability. This paper proposes and defines the inner potential to summarize [...] Read more.

With the rapid development of wind power generation, the inertial response of wind turbines (WTs) has become a topic of wide concern recently, due to its influence on grid frequency dynamics and stability. This paper proposes and defines the inner potential to summarize and understand the inertia control methods and inertial response of type-3 and type-4 WTs, which is analogous to typical synchronous generators (SGs), to make it more easy to understand by system operators and engineers with a traditional power system background. The dynamics of the defined inner potential of the wind turbine without any inertia control is different from SGs, thus the electromechanical inertia is completely hidden. The rapid power control loop and synchronization control loop are the major reasons that the WT’s inertial response is disenabled. On the basis of the defined inner potential’s dynamic, the existing inertia control method for WTs are reviewed and summarized as three approaches, i.e., optimizing the power control or synchronization control or both. At last, the main challenges and issues of these inertia controls are attempted to explain and address. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

996 KiB

Open AccessArticle

Validation of Generic Models for Variable Speed Operation Wind Turbines Following the Recent Guidelines Issued by IEC 61400-27

by Andrés Honrubia-Escribano, Francisco Jiménez-Buendía, Emilio Gómez-Lázaro and Jens Fortmann

Energies 2016, 9(12), 1048; https://doi.org/10.3390/en9121048 - 13 Dec 2016

Cited by 17 | Viewed by 7311

Abstract

Considerable efforts are currently being made by several international working groups focused on the development of generic, also known as simplified or standard, wind turbine models for power system stability studies. In this sense, the first edition of International Electrotechnical Commission (IEC) 61400-27-1, [...] Read more.

Considerable efforts are currently being made by several international working groups focused on the development of generic, also known as simplified or standard, wind turbine models for power system stability studies. In this sense, the first edition of International Electrotechnical Commission (IEC) 61400-27-1, which defines generic dynamic simulation models for wind turbines, was published in February 2015. Nevertheless, the correlations of the IEC generic models with respect to specific wind turbine manufacturer models are required by the wind power industry to validate the accuracy and corresponding usability of these standard models. The present work conducts the validation of the two topologies of variable speed wind turbines that present not only the largest market share, but also the most technological advances. Specifically, the doubly-fed induction machine and the full-scale converter (FSC) topology are modeled based on the IEC 61400-27-1 guidelines. The models are simulated for a wide range of voltage dips with different characteristics and wind turbine operating conditions. The simulated response of the IEC generic model is compared to the corresponding simplified model of a wind turbine manufacturer, showing a good correlation in most cases. Validation error sources are analyzed in detail, as well. In addition, this paper reviews in detail the previous work done in this field. Results suggest that wind turbine manufacturers are able to adjust the IEC generic models to represent the behavior of their specific wind turbines for power system stability analysis. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

2664 KiB

Open AccessArticle

A Flexible Ramping Capacity Model for Generation Scheduling with High Levels of Wind Energy Penetration

by Hungyu Kwon, Jong-Keun Park, Dam Kim, Jihyun Yi and Hyeongon Park

Energies 2016, 9(12), 1040; https://doi.org/10.3390/en9121040 - 11 Dec 2016

Cited by 13 | Viewed by 4888

Abstract

The penetration level of renewable generation has increased significantly in recent years, which has led to operational concerns associated with the system ramping capability. Here, we propose the flexible ramping capacity (FRC) model, which considers the practical ramping capability of generation resources as [...] Read more.

The penetration level of renewable generation has increased significantly in recent years, which has led to operational concerns associated with the system ramping capability. Here, we propose the flexible ramping capacity (FRC) model, which considers the practical ramping capability of generation resources as well as the uncertainty in net load. The FRC model also incorporates the demand curve of the ramping capacity, which represents the hourly economic value of the ramping capacity. The model is formulated mathematically using ramp constraints, which are incorporated into unit commitment (UC) and economic dispatch (ED) processes. Simulations are carried out using a 10-unit system to compare the FRC model with conventional methods. We show that the FRC method can improve reliability and reduce expected operating costs. The simulation results also show that, by using the FRC model, system reliability can be satisfied at high wind power generation levels while achieving economic efficiency. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

6544 KiB

Open AccessArticle

Development of Seismic Demand for Chang-Bin Offshore Wind Farm in Taiwan Strait

by Yu-Kai Wang, Juin-Fu Chai, Yu-Wen Chang, Ti-Ying Huang and Yu-Shu Kuo

Energies 2016, 9(12), 1036; https://doi.org/10.3390/en9121036 - 9 Dec 2016

Cited by 13 | Viewed by 6494

Abstract

Taiwan is located on the Pacific seismic belt, and the soil conditions of Taiwan’s offshore wind farms are softer than those in Europe. To ensure safety and stability of the offshore wind turbine supporting structures, it is important to assess the offshore wind [...] Read more.

Taiwan is located on the Pacific seismic belt, and the soil conditions of Taiwan’s offshore wind farms are softer than those in Europe. To ensure safety and stability of the offshore wind turbine supporting structures, it is important to assess the offshore wind farms seismic forces reasonably. In this paper, the relevant seismic and geological data are obtained for Chang-Bin offshore wind farm in Taiwan Strait, the probabilistic seismic hazard analysis (PSHA) is carried out, and the first uniform hazard response spectrum for Chang-Bin offshore wind farm is achieved. Compared with existing design response spectrum in the local regulation, this site-specific seismic hazard analysis has influence on the seismic force considered in the design of supporting structures and therefore affects the cost of the supporting structures. The results show that a site-specific seismic hazard analysis is required for high seismic area. The paper highlights the importance of seismic hazard analysis to assess the offshore wind farms seismic forces. The follow-up recommendations and research directions are given for Taiwan’s offshore wind turbine supporting structures under seismic force considerations. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

15412 KiB

Open AccessArticle

Strategy Design of Hybrid Energy Storage System for Smoothing Wind Power Fluctuations

by Jingyu Liu and Lei Zhang

Energies 2016, 9(12), 991; https://doi.org/10.3390/en9120991 - 25 Nov 2016

Cited by 26 | Viewed by 6436

Abstract

With the increasing contribution of wind power plants, the reliability and security of modern power systems have become a huge challenge due to the uncertainty and intermittency of wind energy sources. In this paper, a hybrid energy storage system (HESS) consisting of battery [...] Read more.

With the increasing contribution of wind power plants, the reliability and security of modern power systems have become a huge challenge due to the uncertainty and intermittency of wind energy sources. In this paper, a hybrid energy storage system (HESS) consisting of battery and supercapacitor is built to smooth the power fluctuations of wind power. A power allocation strategy is proposed to give full play to the respective advantages of the two energy storage components. In the proposed strategy, the low-frequency and high-frequency components of wind power fluctuations are absorbed by battery groups and supercapacitor groups, respectively. By inhibiting the low-frequency components of supercapacitor current, the times of charging-discharging of battery groups can be significantly reduced. A DC/AC converter is applied to achieve the power exchange between the HESS and the grid. Adjustment rules for regulating state-of-charge (SOC) of energy storage elements are designed to avoid overcharge and deep discharge considering the safety and the high efficiency of the energy storage elements. Experimental results on the test platform verify the effectiveness of the proposed power allocation strategy in DC/AC converter and battery SOC adjustment rules for regulating SOC levels. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

6042 KiB

Open AccessArticle

An Improved Adaptive-Torque-Gain MPPT Control for Direct-Driven PMSG Wind Turbines Considering Wind Farm Turbulences

by Xiaolian Zhang, Can Huang, Sipeng Hao, Fan Chen and Jingjing Zhai

Energies 2016, 9(11), 977; https://doi.org/10.3390/en9110977 - 22 Nov 2016

Cited by 31 | Viewed by 8318

Abstract

Maximum power point tracking (MPPT) plays an important role in increasing the efficiency of a wind energy conversion system (WECS). In this paper, three conventional MPPT methods are reviewed: power signal feedback (PSF) control, decreased torque gain (DTG) control, and adaptive torque gain [...] Read more.

Maximum power point tracking (MPPT) plays an important role in increasing the efficiency of a wind energy conversion system (WECS). In this paper, three conventional MPPT methods are reviewed: power signal feedback (PSF) control, decreased torque gain (DTG) control, and adaptive torque gain (ATG) control, and their potential challenges are investigated. It is found out that the conventional MPPT method ignores the effect of wind turbine inertia and wind speed fluctuations, which lowers WECS efficiency. Accordingly, an improved adaptive torque gain (IATG) method is proposed, which customizes adaptive torque gains and enhances MPPT performances. Specifically, the IATG control considers wind farm turbulences and works out the relationship between the optimal torque gains and the wind speed characteristics, which has not been reported in the literature. The IATG control is promising, especially under the ongoing trend of building wind farms with large-scale wind turbines and at low and medium wind speed sites. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

5325 KiB

Open AccessArticle

Electric Circuit Model for the Aerodynamic Performance Analysis of a Three-Blade Darrieus-Type Vertical Axis Wind Turbine: The Tchakoua Model

by Pierre Tchakoua, René Wamkeue, Mohand Ouhrouche, Ernesto Benini and Gabriel Ekemb

Energies 2016, 9(10), 820; https://doi.org/10.3390/en9100820 - 14 Oct 2016

Cited by 2 | Viewed by 8392

Abstract

The complex and unsteady aerodynamics of vertical axis wind turbines (VAWTs) pose significant challenges for simulation tools. Recently, significant research efforts have focused on the development of new methods for analysing and optimising the aerodynamic performance of VAWTs. This paper presents an electric [...] Read more.

The complex and unsteady aerodynamics of vertical axis wind turbines (VAWTs) pose significant challenges for simulation tools. Recently, significant research efforts have focused on the development of new methods for analysing and optimising the aerodynamic performance of VAWTs. This paper presents an electric circuit model for Darrieus-type vertical axis wind turbine (DT-VAWT) rotors. The novel Tchakoua model is based on the mechanical description given by the Paraschivoiu double-multiple streamtube model using a mechanical‑electrical analogy. Model simulations were conducted using MATLAB for a three-bladed rotor architecture, characterized by a NACA0012 profile, an average Reynolds number of 40,000 for the blade and a tip speed ratio of 5. The results obtained show strong agreement with findings from both aerodynamic and computational fluid dynamics (CFD) models in the literature. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Graphical abstract

Review

Jump to: Research

3543 KiB

Open AccessReview

Review of Reactive Power Dispatch Strategies for Loss Minimization in a DFIG-based Wind Farm

by Baohua Zhang, Weihao Hu, Peng Hou, Jin Tan, Mohsen Soltani and Zhe Chen

Energies 2017, 10(7), 856; https://doi.org/10.3390/en10070856 - 27 Jun 2017

Cited by 16 | Viewed by 5982

Abstract

This paper reviews and compares the performance of reactive power dispatch strategies for the loss minimization of Doubly Fed Induction Generator (DFIG)-based Wind Farms (WFs). Twelve possible combinations of three WF level reactive power dispatch strategies and four Wind Turbine (WT) level reactive [...] Read more.

This paper reviews and compares the performance of reactive power dispatch strategies for the loss minimization of Doubly Fed Induction Generator (DFIG)-based Wind Farms (WFs). Twelve possible combinations of three WF level reactive power dispatch strategies and four Wind Turbine (WT) level reactive power control strategies are investigated. All of the combined strategies are formulated based on the comprehensive loss models of WFs, including the loss models of DFIGs, converters, filters, transformers, and cables of the collection system. Optimization problems are solved by a Modified Particle Swarm Optimization (MPSO) algorithm. The effectiveness of these strategies is evaluated by simulations on a carefully designed WF under a series of cases with different wind speeds and reactive power requirements of the WF. The wind speed at each WT inside the WF is calculated using the Jensen wake model. The results show that the best reactive power dispatch strategy for loss minimization comes when the WF level strategy and WT level control are coordinated and the losses from each device in the WF are considered in the objective. Full article

(This article belongs to the Special Issue Wind Turbine 2017)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Wind Turbine 2017

Share This Special Issue

Special Issue Editor

Special Issue Information

Benefits of Publishing in a Special Issue

Published Papers (26 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI