Research

8631 KiB

Open AccessArticle

Investigation of the Optimal Omni-Direction-Guide-Vane Design for Vertical Axis Wind Turbines Based on Unsteady Flow CFD Simulation

by Behzad Shahizare, Nik Nazri Bin Nik Ghazali, Wen Tong Chong, Seyed Saeed Tabatabaeikia and Nima Izadyar

Energies 2016, 9(3), 146; https://doi.org/10.3390/en9030146 - 02 Mar 2016

Cited by 15 | Viewed by 10348

Abstract

With soaring energy demands, the desire to explore alternate and renewable energy resources has become the focal point of various active research fronts. Therefore, the scientific community is revisiting the notion to tap wind resources in more rigorous and novel ways. In this [...] Read more.

With soaring energy demands, the desire to explore alternate and renewable energy resources has become the focal point of various active research fronts. Therefore, the scientific community is revisiting the notion to tap wind resources in more rigorous and novel ways. In this study, a two-dimensional computational investigation of the vertical axis wind turbine (VAWT) with omni-direction-guide-vane (ODGV) is proposed to determine the effects of this guide vane. In addition, the mesh and time step (dt) size dependency test, as well as the effect of the different turbulence models on results accuracy are investigated. Eight different shape ratios (R) of the omni-direction-guide-vane were also examined in this study. Further, the CFD model is validated by comparing the numerical results with the experimental data. Validation results show a good agreement in terms of shape and trend in CFD simulation. Based on these results, all the shape ratios, except two ratios including 0.3 and 0.4 at TSR of 1.3 to 3, have a positive effect on the power and torque coefficient improvement. Moreover, results show that the best case has a shape ratio of 0.55, which improves the power coefficient by 48% and the torque coefficient up to 58%. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1593 KiB

Open AccessEditor’s ChoiceArticle

Effects of Reynolds Number on the Energy Conversion and Near-Wake Dynamics of a High Solidity Vertical-Axis Cross-Flow Turbine

by Peter Bachant and Martin Wosnik

Energies 2016, 9(2), 73; https://doi.org/10.3390/en9020073 - 26 Jan 2016

Cited by 109 | Viewed by 12836

Abstract

Experiments were performed with a large laboratory-scale high solidity cross-flow turbine to investigate Reynolds number effects on performance and wake characteristics and to establish scale thresholds for physical and numerical modeling of individual devices and arrays. It was demonstrated that the performance of [...] Read more.

Experiments were performed with a large laboratory-scale high solidity cross-flow turbine to investigate Reynolds number effects on performance and wake characteristics and to establish scale thresholds for physical and numerical modeling of individual devices and arrays. It was demonstrated that the performance of the cross-flow turbine becomes essentially R e -independent at a Reynolds number based on the rotor diameter R e_D ≈ 10⁶ or an approximate average Reynolds number based on the blade chord length R e_c ≈ 2 × 10⁵ . A simple model that calculates the peak torque coefficient from static foil data and cross-flow turbine kinematics was shown to be a reasonable predictor for Reynolds number dependence of an actual cross-flow turbine operating under dynamic conditions. Mean velocity and turbulence measurements in the near-wake showed subtle differences over the range of R e investigated. However, when transport terms for the streamwise momentum and mean kinetic energy were calculated, a similar R e threshold was revealed. These results imply that physical model studies of cross-flow turbines should achieve R e_D ∼ 10⁶ to properly approximate both the performance and wake dynamics of full-scale devices and arrays. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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4934 KiB

Open AccessArticle

Aerodynamic and Structural Integrated Optimization Design of Horizontal-Axis Wind Turbine Blades

by Jie Zhu, Xin Cai and Rongrong Gu

Energies 2016, 9(2), 66; https://doi.org/10.3390/en9020066 - 22 Jan 2016

Cited by 17 | Viewed by 8756

Abstract

A procedure based on MATLAB combined with ANSYS is presented and utilized for the aerodynamic and structural integrated optimization design of Horizontal-Axis Wind Turbine (HAWT) blades. Three modules are used for this purpose: an aerodynamic analysis module using the Blade Element Momentum (BEM) [...] Read more.

A procedure based on MATLAB combined with ANSYS is presented and utilized for the aerodynamic and structural integrated optimization design of Horizontal-Axis Wind Turbine (HAWT) blades. Three modules are used for this purpose: an aerodynamic analysis module using the Blade Element Momentum (BEM) theory, a structural analysis module employing the Finite Element Method (FEM) and a multi-objective optimization module utilizing the non-dominated sorting genetic algorithm. The former two provide a sufficiently accurate solution of the aerodynamic and structural performances of the blade; the latter handles the design variables of the optimization problem, namely, the main geometrical shape and structural parameters of the blade, and promotes function optimization. The scope of the procedure is to achieve the best trade-off performances between the maximum Annual Energy Production (AEP) and the minimum blade mass under various design requirements. To prove the efficiency and reliability of the procedure, a commercial 1.5 megawatt (MW) HAWT blade is used as a case study. 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 2015)

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3958 KiB

Open AccessArticle

Low Voltage Ride-Through Capability Solutions for Permanent Magnet Synchronous Wind Generators

by Victor F. Mendes, Frederico F. Matos, Silas Y. Liu, Allan F. Cupertino, Heverton A. Pereira and Clodualdo V. De Sousa

Energies 2016, 9(1), 59; https://doi.org/10.3390/en9010059 - 20 Jan 2016

Cited by 29 | Viewed by 6869

Abstract

Due to the increasing number of wind power plants, several countries have modified their grid codes to include specific requirements for the connection of this technology to the power system. One of the requirements is the ride-through fault capability (RTFC), i.e., the [...] Read more.

Due to the increasing number of wind power plants, several countries have modified their grid codes to include specific requirements for the connection of this technology to the power system. One of the requirements is the ride-through fault capability (RTFC), i.e., the system capability to sustain operation during voltage sags. In this sense, the present paper intends to investigate the behavior of a full-converter wind generator with a permanent magnet synchronous machine during symmetrical and asymmetrical voltage sags. Two solutions to improve the low voltage ride-through capability (LVRT) of this technology are analyzed: discharging resistors (brake chopper) and resonant controllers (RCs). The design and limitations of these solutions and the others proposed in the literature are discussed. Experimental results in a 34 kW test bench, which represents a scaled prototype of a real 2 MW wind conversion system, are presented. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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4316 KiB

Open AccessArticle

Optimal Maintenance Management of Offshore Wind Farms

by Alberto Pliego Marugán, Fausto Pedro García Márquez and Jesús María Pinar Pérez

Energies 2016, 9(1), 46; https://doi.org/10.3390/en9010046 - 15 Jan 2016

Cited by 84 | Viewed by 8665

Abstract

Nowadays offshore wind energy is the renewable energy source with the highest growth. Offshore wind farms are composed of large and complex wind turbines, requiring a high level of reliability, availability, maintainability and safety (RAMS). Firms are employing robust remote condition monitoring systems [...] Read more.

Nowadays offshore wind energy is the renewable energy source with the highest growth. Offshore wind farms are composed of large and complex wind turbines, requiring a high level of reliability, availability, maintainability and safety (RAMS). Firms are employing robust remote condition monitoring systems in order to improve RAMS, considering the difficulty to access the wind farm. The main objective of this research work is to optimise the maintenance management of wind farms through the fault probability of each wind turbine. The probability has been calculated by Fault Tree Analysis (FTA) employing the Binary Decision Diagram (BDD) in order to reduce the computational cost. The fault tree presented in this paper has been designed and validated based on qualitative data from the literature and expert from important European collaborative research projects. The basic events of the fault tree have been prioritized employing the criticality method in order to use resources efficiently. Exogenous variables, e.g., weather conditions, have been also considered in this research work. The results provided by the dynamic probability of failure and the importance measures have been employed to develop a scheduled maintenance that contributes to improve the decision making and, consequently, to reduce the maintenance costs. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1721 KiB

Open AccessArticle

A New Fault Location Approach for Acoustic Emission Techniques in Wind Turbines

by Carlos Quiterio Gómez Muñoz and Fausto Pedro García Márquez

Energies 2016, 9(1), 40; https://doi.org/10.3390/en9010040 - 12 Jan 2016

Cited by 85 | Viewed by 7108

Abstract

The renewable energy industry is undergoing continuous improvement and development worldwide, wind energy being one of the most relevant renewable energies. This industry requires high levels of reliability, availability, maintainability and safety (RAMS) for wind turbines. The blades are critical components in wind [...] Read more.

The renewable energy industry is undergoing continuous improvement and development worldwide, wind energy being one of the most relevant renewable energies. This industry requires high levels of reliability, availability, maintainability and safety (RAMS) for wind turbines. The blades are critical components in wind turbines. The objective of this research work is focused on the fault detection and diagnosis (FDD) of the wind turbine blades. The FDD approach is composed of a robust condition monitoring system (CMS) and a novel signal processing method. CMS collects and analyses the data from different non-destructive tests based on acoustic emission. The acoustic emission signals are collected applying macro-fiber composite (MFC) sensors to detect and locate cracks on the surface of the blades. Three MFC sensors are set in a section of a wind turbine blade. The acoustic emission signals are generated by breaking a pencil lead in the blade surface. This method is used to simulate the acoustic emission due to a breakdown of the composite fibers. The breakdown generates a set of mechanical waves that are collected by the MFC sensors. A graphical method is employed to obtain a system of non-linear equations that will be used for locating the emission source. This work demonstrates that a fiber breakage in the wind turbine blade can be detected and located by using only three low cost sensors. It allows the detection of potential failures at an early stages, and it can also reduce corrective maintenance tasks and downtimes and increase the RAMS of the wind turbine. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1255 KiB

Open AccessArticle

Noise Emission of a 200 kW Vertical Axis Wind Turbine

by Erik Möllerström, Fredric Ottermo, Jonny Hylander and Hans Bernhoff

Energies 2016, 9(1), 19; https://doi.org/10.3390/en9010019 - 29 Dec 2015

Cited by 40 | Viewed by 11410

Abstract

The noise emission from a vertical axis wind turbine (VAWT) has been investigated. A noise measurement campaign on a 200 kW straight-bladed VAWT has been conducted, and the result has been compared to a semi-empirical model for turbulent-boundary-layer trailing edge (TBL-TE) noise. The [...] Read more.

The noise emission from a vertical axis wind turbine (VAWT) has been investigated. A noise measurement campaign on a 200 kW straight-bladed VAWT has been conducted, and the result has been compared to a semi-empirical model for turbulent-boundary-layer trailing edge (TBL-TE) noise. The noise emission from the wind turbine was measured, at wind speed 8 m/s, 10 m above ground, to 96.2 dBA. At this wind speed, the turbine was stalling as it was run at a tip speed lower than optimal due to constructional constraints. The noise emission at a wind speed of 6 m/s, 10 m above ground was measured while operating at optimum tip speed and was found to be 94.1 dBA. A comparison with similar size horizontal axis wind turbines (HAWTs) indicates a noise emission at the absolute bottom of the range. Furthermore, it is clear from the analysis that the turbulent-boundary-layer trailing-edge noise, as modeled here, is much lower than the measured levels, which suggests that other mechanisms are likely to be important, such as inflow turbulence. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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2085 KiB

Open AccessArticle

Enhancing LVRT of DFIG by Using a Superconducting Current Limiter on Rotor Circuit

by Flávio Oliveira, Arthur Amorim, Lucas Encarnação, Jussara Fardin, Marcos Orlando, Selênio Silva and Domingos Simonetti

Energies 2016, 9(1), 16; https://doi.org/10.3390/en9010016 - 25 Dec 2015

Cited by 15 | Viewed by 5443

Abstract

This paper have studied the dynamic of a 2.0 MW Doubly Fed Induction Generator (DFIG) during a severe voltage sag. Using the dynamic model of a DFIG, it was possible to determine the current, Electromagnetic Force and flux behavior during three-phase symmetrical voltage [...] Read more.

This paper have studied the dynamic of a 2.0 MW Doubly Fed Induction Generator (DFIG) during a severe voltage sag. Using the dynamic model of a DFIG, it was possible to determine the current, Electromagnetic Force and flux behavior during three-phase symmetrical voltage dip. Among the technologies of wind turbines the DFIG is widely employed; however, this machine is extremely susceptible to disturbances from the grid. In order to improve DFIG Low Voltage Ride-Through (LVRT), it is proposed a novel solution, using Superconducting Current Limiter (SCL) in two arrangements: one, the SCL is placed between the machine rotor and the rotor side converter (RSC), and another placed in the RSC DC-link. The proposal is validated through simulation using PSCAD™/EMTDC™ and according to requirements of specific regulations. The analysis ensure that both SCL arrangements behave likewise, and are effective in decrement the rotor currents during the disturbance. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1948 KiB

Open AccessArticle

Pareto-Optimal Evaluation of Ultimate Limit States in Offshore Wind Turbine Structural Analysis

by Michael Muskulus

Energies 2015, 8(12), 14026-14039; https://doi.org/10.3390/en81212414 - 11 Dec 2015

Cited by 6 | Viewed by 6496

Abstract

The ultimate capacity of support structures is checked with extreme loads. This is straightforward when the limit state equations depend on a single load component, and it has become common to report maxima for each load component. However, if more than one load [...] Read more.

The ultimate capacity of support structures is checked with extreme loads. This is straightforward when the limit state equations depend on a single load component, and it has become common to report maxima for each load component. However, if more than one load component is influential, e.g., both axial force and bending moments, it is not straightforward how to define an extreme load. The combination of univariate maxima can be too conservative, and many different combinations of load components can result in the worst value of the limit state equations. The use of contemporaneous load vectors is typically non-conservative. Therefore, in practice, limit state checks are done for each possible load vector, from each time step of a simulation. This is not feasible when performing reliability assessments and structural optimization, where additional, time-consuming computations are involved for each load vector. We therefore propose to use Pareto-optimal loads, which are a small set of loads that together represent all possible worst case scenarios. Simulations with two reference wind turbines show that this approach can be very useful for jacket structures, whereas the design of monopiles is often governed by the bending moment only. Even in this case, the approach might be useful when approaching the structural limits during optimization. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1463 KiB

Open AccessArticle

Overview of Modelling and Advanced Control Strategies for Wind Turbine Systems

by Silvio Simani

Energies 2015, 8(12), 13395-13418; https://doi.org/10.3390/en81212374 - 25 Nov 2015

Cited by 35 | Viewed by 9652

Abstract

The motivation for this paper comes from a real need to have an overview of the challenges of modelling and control for very demanding systems, such as wind turbine systems, which require reliability, availability, maintainability, and safety over power conversion efficiency. These issues [...] Read more.

The motivation for this paper comes from a real need to have an overview of the challenges of modelling and control for very demanding systems, such as wind turbine systems, which require reliability, availability, maintainability, and safety over power conversion efficiency. These issues have begun to stimulate research and development in the wide control community particularly for these installations that need a high degree of “sustainability”. Note that this represents a key point for offshore wind turbines, since they are characterised by expensive and/or safety critical maintenance work. In this case, a clear conflict exists between ensuring a high degree of availability and reducing maintenance times, which affect the final energy cost. On the other hand, wind turbines have highly nonlinear dynamics, with a stochastic and uncontrollable driving force as input in the form of wind speed, thus representing an interesting challenge also from the modelling point of view. Suitable control methods can provide a sustainable optimisation of the energy conversion efficiency over wider than normally expected working conditions. Moreover, a proper mathematical description of the wind turbine system should be able to capture the complete behaviour of the process under monitoring, thus providing an important impact on the control design itself. In this way, the control scheme could guarantee prescribed performance, whilst also giving a degree of “tolerance” to possible deviation of characteristic properties or system parameters from standard conditions, if properly included in the wind turbine model itself. The most important developments in advanced controllers for wind turbines are also briefly referenced, and open problems in the areas of modelling of wind turbines are finally outlined. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1073 KiB

Open AccessArticle

Integrating Auto-Associative Neural Networks with Hotelling T² Control Charts for Wind Turbine Fault Detection

by Hsu-Hao Yang, Mei-Ling Huang and Shih-Wei Yang

Energies 2015, 8(10), 12100-12115; https://doi.org/10.3390/en81012100 - 23 Oct 2015

Cited by 33 | Viewed by 6075

Abstract

This paper presents a novel methodology to detect a set of more suitable attributes that may potentially contribute to emerging faults of a wind turbine. The set of attributes were selected from one-year historical data for analysis. The methodology uses the k-means [...] Read more.

This paper presents a novel methodology to detect a set of more suitable attributes that may potentially contribute to emerging faults of a wind turbine. The set of attributes were selected from one-year historical data for analysis. The methodology uses the k-means clustering method to process outlier data and verifies the clustering results by comparing quartiles of boxplots, and applies the auto-associative neural networks to implement the residual approach that transforms the data to be approximately normally distributed. Hotelling T² multivariate quality control charts are constructed for monitoring the turbine’s performance and relative contribution of each attribute is calculated for the data points out of upper limits to determine the set of potential attributes. A case using the historical data and the alarm log is given and illustrates that our methodology has the advantage of detecting a set of susceptible attributes at the same time compared with only one independent attribute is monitored. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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2852 KiB

Open AccessArticle

An Experimental Study on the Effects ofWinglets on the Wake and Performance of a ModelWind Turbine

by Nicolas Tobin, Ali M. Hamed and Leonardo P. Chamorro

Energies 2015, 8(10), 11955-11972; https://doi.org/10.3390/en81011955 - 21 Oct 2015

Cited by 47 | Viewed by 7842

Abstract

Wind tunnel experiments were performed to investigate the effects of downstream-facing winglets on the wake dynamics, power and thrust of a model wind turbine. Two similar turbines with and without winglets were operated under the same conditions. Results show an increase in the [...] Read more.

Wind tunnel experiments were performed to investigate the effects of downstream-facing winglets on the wake dynamics, power and thrust of a model wind turbine. Two similar turbines with and without winglets were operated under the same conditions. Results show an increase in the power and thrust coefficients of 8.2% and 15.0% for the wingletted case. A simple theoretical treatment of a two-turbine system suggests a possible positive tradeoff between increasing power and thrust coefficients at a wind farm scale. The higher thrust coefficient created a region of enhanced mean shear and turbulence in the outer portion of the wake. The winglets did not significantly change the tip-vortex strength, but higher levels of turbulence in the far wake decreased the tip-vortex strength. Because of the increased mean shear in the wingletted turbine’s wake, the Reynolds stresses were higher, potentially leading to a higher energy flux downstream. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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4612 KiB

Open AccessArticle

A New Building-Integrated Wind Turbine System Utilizing the Building

by Jeongsu Park, Hyung-Jo Jung, Seung-Woo Lee and Jiyoung Park

Energies 2015, 8(10), 11846-11870; https://doi.org/10.3390/en81011846 - 21 Oct 2015

Cited by 52 | Viewed by 11503

Abstract

This paper proposes an innovative building-integrated wind turbine (BIWT) system by directly utilizing the building skin, which is an unused and unavailable area in all conventional BIWT systems. The proposed system has been developed by combining a guide vane that is able to [...] Read more.

This paper proposes an innovative building-integrated wind turbine (BIWT) system by directly utilizing the building skin, which is an unused and unavailable area in all conventional BIWT systems. The proposed system has been developed by combining a guide vane that is able to effectively collect the incoming wind and increase its speed and a rotor with an appropriate shape for specific conditions. To this end, several important design issues for the guide vane as well as the rotor were thoroughly investigated and accordingly addressed in this paper. A series of computational fluid dynamics (CFD) analyses was performed to determine the optimal configuration of the proposed system. Finally, it is demonstrated from performance evaluation tests that the prototype with the specially designed guide vane and rotor for the proposed BIWT system accelerates the wind speed to a sufficient level and consequently increases the power coefficient significantly. Thus, it was confirmed that the proposed system is a promising environment-friendly energy production system for urban areas. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1065 KiB

Open AccessArticle

Numerical Validation of a Vortex Model against ExperimentalData on a Straight-Bladed Vertical Axis Wind Turbine

by Eduard Dyachuk and Anders Goude

Energies 2015, 8(10), 11800-11820; https://doi.org/10.3390/en81011800 - 20 Oct 2015

Cited by 15 | Viewed by 6820

Abstract

Cyclic blade motion during operation of vertical axis wind turbines (VAWTs) imposes challenges on the simulations models of the aerodynamics of VAWTs. A two-dimensional vortex model is validated against the new experimental data on a 12-kW straight-bladed VAWT, which is operated at an [...] Read more.

Cyclic blade motion during operation of vertical axis wind turbines (VAWTs) imposes challenges on the simulations models of the aerodynamics of VAWTs. A two-dimensional vortex model is validated against the new experimental data on a 12-kW straight-bladed VAWT, which is operated at an open site. The results on the normal force on one blade are analyzed. The model is assessed against the measured data in the wide range of tip speed ratios: from 1.8 to 4.6. The predicted results within one revolution have a similar shape and magnitude as the measured data, though the model does not reproduce every detail of the experimental data. The present model can be used when dimensioning the turbine for maximum loads. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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637 KiB

Open AccessArticle

Maximum Energy Output of a DFIG Wind Turbine Using an Improved MPPT-Curve Method

by Dinh-Chung Phan and Shigeru Yamamoto

Energies 2015, 8(10), 11718-11736; https://doi.org/10.3390/en81011718 - 19 Oct 2015

Cited by 28 | Viewed by 6950

Abstract

A new method is proposed for obtaining the maximum power output of a doubly-fed induction generator (DFIG) wind turbine to control the rotor- and grid-side converters. The efficiency of maximum power point tracking that is obtained by the proposed method is theoretically guaranteed [...] Read more.

A new method is proposed for obtaining the maximum power output of a doubly-fed induction generator (DFIG) wind turbine to control the rotor- and grid-side converters. The efficiency of maximum power point tracking that is obtained by the proposed method is theoretically guaranteed under assumptions that represent physical conditions. Several control parameters may be adjusted to ensure the quality of control performance. In particular, a DFIG state-space model and a control technique based on the Lyapunov function are adopted to derive the control method. The effectiveness of the proposed method is verified via numerical simulations of a 1.5-MW DFIG wind turbine using MATLAB/Simulink. The simulation results show that when the proposed method is used, the wind turbine is capable of properly tracking the optimal operation point; furthermore, the generator’s available energy output is higher when the proposed method is used than it is when the conventional method is used instead. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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2826 KiB

Open AccessArticle

A Non-Unity Torque Sharing Function for Torque Ripple Minimization of Switched Reluctance Generators in Wind Power Systems

by Hye-Ung Shin, Kiwoo Park and Kyo-Beum Lee

Energies 2015, 8(10), 11685-11701; https://doi.org/10.3390/en81011685 - 16 Oct 2015

Cited by 15 | Viewed by 6784

Abstract

This paper deals with a new torque ripple minimization method for a Switched Reluctance Generator (SRG). Although, the SRG has many advantages including simple and robust construction, and high power density as a generator, it has not been widely employed in the industry. [...] Read more.

This paper deals with a new torque ripple minimization method for a Switched Reluctance Generator (SRG). Although, the SRG has many advantages including simple and robust construction, and high power density as a generator, it has not been widely employed in the industry. One of the major drawbacks of the SRG is its high torque ripple that results in high noise operation of the generator. In this paper, a non-unity Torque Sharing Function (TSF) is proposed to minimize the torque ripple over a wide speed range of operation. Simulations as well as experimental results are presented to verify the effectiveness of the proposed torque ripple minimization technique. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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2340 KiB

Open AccessArticle

Impact of the Converter Control Strategies on the Drive Train of Wind Turbine during Voltage Dips

by Fenglin Miao, Hongsheng Shi and Xiaoqing Zhang

Energies 2015, 8(10), 11452-11469; https://doi.org/10.3390/en81011452 - 13 Oct 2015

Cited by 4 | Viewed by 6160

Abstract

The impact of converter control strategies on the drive train of wind turbines during voltage dips is investigated in this paper using a full electromechanical model. Aerodynamics and tower vibration are taken into consideration by means of a simulation program, named FAST. Detailed [...] Read more.

The impact of converter control strategies on the drive train of wind turbines during voltage dips is investigated in this paper using a full electromechanical model. Aerodynamics and tower vibration are taken into consideration by means of a simulation program, named FAST. Detailed gearbox and electrical subsystems are represented in MATLAB. The dynamic response of electromagnetic torque and its impact on the mechanical variables are the concern in this paper and the response of electrical variables is less discussed. From the mechanical aspects, the effect of rising power recovery speed and unsymmetrical voltage dips are analyzed on the basis of the dynamic response of the high-speed shaft (HSS). A comparison of the impact on the drive train is made for two converter control strategies during small voltage dips. Through the analysis of torque, speed and tower vibration, the results indicate that both power recovery speed and the sudden torque sag have a significant impact on drive trains, and the effects depend on the different control strategies. Moreover, resonance might be excited on the drive train by an unbalanced voltage. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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5002 KiB

Open AccessArticle

Rotor Design for Diffuser Augmented Wind Turbines

by Søren Hjort and Helgi Larsen

Energies 2015, 8(10), 10736-10774; https://doi.org/10.3390/en81010736 - 28 Sep 2015

Cited by 16 | Viewed by 7662

Abstract

Diffuser augmented wind turbines (DAWTs) can increase mass flow through the rotor substantially, but have often failed to fulfill expectations. We address high-performance diffusers, and investigate the design requirements for a DAWT rotor to efficiently convert the available energy to shaft energy. Several [...] Read more.

Diffuser augmented wind turbines (DAWTs) can increase mass flow through the rotor substantially, but have often failed to fulfill expectations. We address high-performance diffusers, and investigate the design requirements for a DAWT rotor to efficiently convert the available energy to shaft energy. Several factors can induce wake stall scenarios causing significant energy loss. The causality between these stall mechanisms and earlier DAWT failures is discussed. First, a swirled actuator disk CFD code is validated through comparison with results from a far wake swirl corrected blade-element momentum (BEM) model, and horizontal-axis wind turbine (HAWT) reference results. Then, power efficiency versus thrust is computed with the swirled actuator disk (AD) code for low and high values of tip-speed ratios (TSR), for different centerbodies, and for different spanwise rotor thrust loading distributions. Three different configurations are studied: The bare propeller HAWT, the classical DAWT, and the high-performance multi-element DAWT. In total nearly 400 high-resolution AD runs are generated. These results are presented and discussed. It is concluded that dedicated DAWT rotors can successfully convert the available energy to shaft energy, provided the identified design requirements for swirl and axial loading distributions are satisfied. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1338 KiB

Open AccessArticle

A New Approach for Modeling Darrieus-Type Vertical Axis Wind Turbine Rotors Using Electrical Equivalent Circuit Analogy: Basis of Theoretical Formulations and Model Development

by Pierre Tchakoua, René Wamkeue, Mohand Ouhrouche, Tommy Andy Tameghe and Gabriel Ekemb

Energies 2015, 8(10), 10684-10717; https://doi.org/10.3390/en81010684 - 25 Sep 2015

Cited by 19 | Viewed by 14763

Abstract

Models are crucial in the engineering design process because they can be used for both the optimization of design parameters and the prediction of performance. Thus, models can significantly reduce design, development and optimization costs. This paper proposes a novel equivalent electrical model [...] Read more.

Models are crucial in the engineering design process because they can be used for both the optimization of design parameters and the prediction of performance. Thus, models can significantly reduce design, development and optimization costs. This paper proposes a novel equivalent electrical model for Darrieus-type vertical axis wind turbines (DTVAWTs). The proposed model was built from the mechanical description given by the Paraschivoiu double-multiple streamtube model and is based on the analogy between mechanical and electrical circuits. This work addresses the physical concepts and theoretical formulations underpinning the development of the model. After highlighting the working principle of the DTVAWT, the step-by-step development of the model is presented. For assessment purposes, simulations of aerodynamic characteristics and those of corresponding electrical components are performed and compared. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1371 KiB

Open AccessArticle

A New Application of the Multi-Resonant Zero-Current Switching Buck Converter: Analysis and Simulation in a PMSG Based WECS

by Tiara Freitas, Paulo Menegáz and Domingos Simonetti

Energies 2015, 8(9), 10219-10238; https://doi.org/10.3390/en80910219 - 17 Sep 2015

Cited by 3 | Viewed by 5812

Abstract

A new application of the three-phase buck-resonant converter is presented in this paper. It is shown that the analyzed converter is suitable to operate as the rectifier stage in low power wind energy conversion systems (WECS) based on permanent magnet synchronous generators (PMSG) [...] Read more.

A new application of the three-phase buck-resonant converter is presented in this paper. It is shown that the analyzed converter is suitable to operate as the rectifier stage in low power wind energy conversion systems (WECS) based on permanent magnet synchronous generators (PMSG) with variable wind speed. As main features, it presents a single controlled switch, simple implementation and control, and operates with a high power factor and low harmonic distortion over all wind speed ranges. The converter topology, its design equations and its operation are presented, as well as the simulation results of the PMSG based conversion system. From the analysis carried out in the paper it is concluded that the converter is indicated to be employed in distributed generation and hybrid systems where wind generation is associated with other sources. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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894 KiB

Open AccessArticle

Blade Fault Diagnosis in Small Wind Power Systems Using MPPT with Optimized Control Parameters

by Jui-Ho Chen and Weir Hung

Energies 2015, 8(9), 9191-9210; https://doi.org/10.3390/en8099191 - 27 Aug 2015

Cited by 6 | Viewed by 6015

Abstract

A systematic experiment verification of Chaos Embedded Sliding Mode Extremum Seeking Control for maximum power point tracking and a method for detecting possible faults in small wind turbine systems in advance are proposed in this paper. The chaotic logistic map is used to [...] Read more.

A systematic experiment verification of Chaos Embedded Sliding Mode Extremum Seeking Control for maximum power point tracking and a method for detecting possible faults in small wind turbine systems in advance are proposed in this paper. The chaotic logistic map is used to replace the random function in the particle swarm optimization algorithm for faster searching the optimal control parameter . From the experimental results, it is verified that the Chaos Embedded Sliding Mode Extremum Seeking Control scheme has a better dynamic response than traditional Extremum Seeking Control scheme and Hill-Climbing Search scheme for maximum power point tracking. In the proposed scheme for fault detection, a chaotic synchronization method is used to transform the maximum power point tracking signal into a chaos synchronization error distribution diagram. It is then taken as the characteristic for fault diagnosis purposes. Finally, an extension theory pattern recognition technique is applied to diagnose the fault. Notably, the use of the chaotic dynamic errors as the fault diagnosis characteristic reduces the number of extracted features required, and therefore greatly reduces both the computation time and the hardware implementation cost. From the experimental results, it is shown that the fault diagnosis rate of the proposed method exceeds 98% not only in non-real-time but also in real-time of faults detection of the blades. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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1162 KiB

Open AccessArticle

Economic Impact Assessment of Wind Power Integration: A Quasi-Public Goods Property Perspective

by Huiru Zhao, Sen Guo and Hongze Li

Energies 2015, 8(8), 8749-8774; https://doi.org/10.3390/en8088749 - 17 Aug 2015

Cited by 7 | Viewed by 7047

Abstract

The integration of wind power into power grid will bring some impacts on the multiple subjects of electric power system. Economic impacts of wind power integration on multiple subjects of China’s electric power system were quantitatively assessed from Quasi-public goods property perspective in [...] Read more.

The integration of wind power into power grid will bring some impacts on the multiple subjects of electric power system. Economic impacts of wind power integration on multiple subjects of China’s electric power system were quantitatively assessed from Quasi-public goods property perspective in this paper. Firstly, the Quasi-public goods property of transmission services provided by power grid corporations was elaborated. Secondly, the multiple subjects of China’s electric power system, which include electricity generation enterprises (EGEs), power grid corporations (PGCs), electricity consumers (ECs), and environment, were detailed analyzed. Thirdly, based on the OPF-based nodal price model and transmission service cost allocation model, the economic impact assessment model of wind power integration was built from Quasi-public goods property perspective. Then, the IEEE-24 bus system employed in this paper was introduced according to current status of China’s electric power system, and the modeling of wind turbine was also introduced. Finally, the simulation analysis was performed, and the economic impacts of wind power integration on EGEs, PGCs, ECs and Environment were calculated. The results indicate, from Quasi-public goods property perspective, the wind power integration will bring positive impacts on EGEs, PGCs and Environment, while negative impacts on ECs. The findings can provide references for power system managers, energy planners, and policy makers. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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5201 KiB

Open AccessArticle

Unraveling the Mysteries of Turbulence Transport in a Wind Farm

by Pankaj K. Jha, Earl P. N. Duque, Jessica L. Bashioum and Sven Schmitz

Energies 2015, 8(7), 6468-6496; https://doi.org/10.3390/en8076468 - 26 Jun 2015

Cited by 16 | Viewed by 7547

Abstract

A true physical understanding of the mysteries involved in the recovery process of the wake momentum deficit, downstream of utility-scale wind turbines in the atmosphere, has not been obtained to date. Field data are not acquired at sufficient spatial and temporal resolutions to [...] Read more.

A true physical understanding of the mysteries involved in the recovery process of the wake momentum deficit, downstream of utility-scale wind turbines in the atmosphere, has not been obtained to date. Field data are not acquired at sufficient spatial and temporal resolutions to dissect some of the mysteries of wake turbulence. It is here that the actuator line method has evolved to become the technology standard in the wind energy community. This work presents the actuator line method embedded into an Open source Field Operation and Manipulation (OpenFOAM) large-eddy simulation solver and applies it to two small wind farms, the first one consisting of an array of two National Renewable Energy Laboratory 5 Megawatt (NREL 5-MW) turbines separated by seven rotor diameters in neutral and unstable atmospheric boundary-layer flow and the second one consisting of five NREL 5-MW wind turbines in unstable atmospheric conditions arranged in two staggered arrays of two and three turbines, respectively. Detailed statistics involving power spectral density (PSD) of turbine power along with standard deviations reveal the effects of atmospheric turbulence and its space and time scales. High-resolution surface data extracts provide new insight into the complex recovery process of the wake momentum deficit governed by turbulence transport phenomena. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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