Characteristics Of Wind Turbine Research Articles

A 2 MW Wind Turbine Simulator for DFIG Wind Energy Generation Systems

This work presents the design and implementation of a wind turbine simulator to carry out laboratory tests on the generation, regulation, and control of a wind power conversion system (WECS) with a capacity of 2 MW. A three-phase squirrel-cage induction motor emulates the static and dynamic wind turbine characteristics based on the torque-speed profile of a wind turbine. The Emulator allows all electromechanical tests to be carried out, from the characterization of the generator to the adjustment of controls and protections for equipment operating in a specific location. Initial Emulator tests were successful. This simulator aims to reproduce the same behavior as a wind turbine, that is, the generator must operate as if it were connected to a real turbine. In this line, a wind profile implemented by using a computer program and its output is used as an input signal. This signal together with the speed measured on the axis serves as the input variable of the emulated turbine.

Research on the rotor speed and aerodynamic characteristics of a dynamic yawing wind turbine with a short-time uniform wind direction variation

Dynamic yawing caused by wind direction variation is an important operating case for wind turbines. Because experimental data are lacking, existing studies assume that the rotor speed and pitch angle are constant, which cannot reflect the actual working states of wind turbines in the short-time variation of the wind direction. In this study, the rotor speed and power characteristics of wind turbine with the condition of variable wind direction were obtained through experiments. Using the experimental time-varying rotor speed curve, the aerodynamic characteristics were further studied using computational fluid dynamics method. The results showed that the rotor speed decreased due to the short-term wind direction variation. The final rotor speed and the stable time were related to the initial tip speed ratio and the wind direction variation rate, respectively. The dynamic yawing with the assumption of invariable rotor speed overestimated the average torque and underestimated the variation of torque. The continuous decreasing rotor speed made the angle of attack and its fluctuation degree larger. This caused a wide range of the flow separation for the whole blade and large fluctuation of the axial/tangential force load, and it doubled the fluctuation frequency of the aerodynamic load in the blade root region.

Analysis of Aerodynamic Characteristics of Vertical Axis Wind Turbine (VAWT) Based on Modified Double Multiple Stream Tube Model

To further improvement of the aerodynamic performance simulation model accuracy of Vertical Axis Wind Turbine (VAWT), based on the traditional double multi-flow tube theoretical model, the aerodynamic parameters of the airfoil before and after stall are modified by the Lanchester method. Prand model is used to modify the aspect ratio of the airfoil under the condition of the small angle of attack before stall. Viterna Corrigan model is used to modify the aspect ratio, lift and drag coefficients of the airfoil under the stall. And a relaxation factor is introduced to correct the induction factor, also to improve the iterative non-convergence of the simulation under the condition of large tip speed ratio. The simulation results match the experimental data very well. Based on this new aerodynamic performance analysis method, the influence of blade tip speed ratio, blade number, blade chord length, rotor radius, and incoming wind speed on power coefficient and tangential force coefficient is studied, which can provide a reference for the design of aerodynamic performance parameters of the wind turbine.

On the application of semicircular and Bach-type blades in the internal Savonius rotor of a hybrid wind turbine system

In the present study, a comparison has been performed numerically to explore the impact of internal rotor type on power characteristics of a two-bladed hybrid vertical axis wind turbine (VAWT). For this purpose, the internal rotor of a hybrid wind turbine built with the conventional semicircle and Bach-type blades is considered under two free-wind speeds (U∞) of 5 and 10 m/s. Computations are conducted at three tip speed ratios (TSRs) of 1.5, 2.5, and 3.5. Effects of different relative positions between the external and internal rotors, called attachment angle, (φ) such as 0°, 45°, and 90° are studied in detail and the obtained results are validated against the available data for Darrieus and Savonius rotors, separately. The results illustrate that the internal rotor type, attachment angle, and TSR have considerable impacts on the hybrid rotor performance. Moreover, it is demonstrated that the Bach-type Savonius rotor has better performance than the conventional semicircle one in a two-bladed hybrid wind turbine regardless of φ, TSR, and U∞. The maximum improvement of 20% is reported for hybrid wind turbine equipped with Bach-type rotor under φ = 90°, TSR = 1.5, and U∞ = 5 m/s.

Aerodynamic characteristic of wind turbine with the leading edge slat and Microtab

The leading edge slat can increase the flow energy of airfoil suction surface, and Microtab can hinder the flow of pressure surface. In order to combine the advantages of two passive flow control methods, this paper creatively proposed to combine the leading edge slat with Microtab to simulate the S809 airfoil, which slat had the contour characteristics of S809 airfoil. The transition SST turbulence model was applied to estimate the aerodynamic characteristics of the S809 airfoil. According to research, the flow control approach of the leading edge slat combined with Microtab could effectively restrain the flow separation and ameliorate the aerodynamic characteristics of the S809 airfoil. For Case-12, when the airfoil angle of attack was 16.22°, the boundary layer flow separation was restrained completely, Cl was increased to 3.06 from 1.79 and increased by 171% compared with clear airfoil. Research shown that the position of slat, the position and height of the Microtab were significant factors for the aerodynamic characteristics of the S809 airfoil. Microtab position at 0.95c and height at 0.03c performed the best effect to inhibit flow separation and improve lift coefficients.

A decision theoretic framework for reliability-based optimal wind turbine selection

The problem of choosing the optimal wind turbine for a specific site is of special importance in the design process of wind farm. Manifestly, the selection of the optimal wind turbine should depend on a certain criteria. In this paper, optimal wind turbine selection is studied in terms of the capacity factor of wind turbine generator and the Expected Energy not Supplied which is one of the most commonly used reliability indices for power systems. The latter one considers the load profile of the system and is suitable to compare different wind farm compositions while the former one completely ignores the load profile of the system. This paper presents general theoretical results that are helpful to compare performance of wind turbines and wind farms without data collection and further numerical assessment. In particular, the conditions on wind turbine characteristics and availability values of wind turbines are determined to compare wind turbines and wind farms in terms of the capacity factor and Expected Energy not Supplied.

Research on the Power Capture and Wake Characteristics of a Wind Turbine Based on a Modified Actuator Line Model

On a wind farm, the wake has an important impact on the performance of the wind turbines. For example, the wake of an upstream wind turbine affects the blade load and output power of the downstream wind turbine. In this paper, a modified actuator line model with blade tips, root loss, and an airfoil three-dimensional delayed stall was revised. This full-scale modified actuator line model with blades, nacelles, and towers, was combined with a Large Eddy Simulation, and then applied and validated based on an analysis of wind turbine wakes in wind farms. The modified actuator line model was verified using an experimental wind turbine. Subsequently, numerical simulations were conducted on two NREL 5 MW wind turbines with different staggered spacing to study the effect of the staggered spacing on the characteristics of wind turbines. The results show that the output power of the upstream turbine stabilized at 5.9 MW, and the output power of the downstream turbine increased. When the staggered spacing is R and 1.5R, both the power and thrust of the downstream turbine are severely reduced. However, the length of the peaks was significantly longer, which resulted in a long-term unstable power output. As the staggered spacing increased, the velocity in the central near wake of the downstream turbine also increased, and the recovery speed at the threshold of the wake slowed down. The modified actuator line model described herein can be used for the numerical simulation of wakes in wind farms.

Effect of blade tip on torque characteristics of circular cylinder blade wind turbine driven by longitudinal vortex

Effect of blade tip on torque characteristics of circular cylinder blade wind turbine driven by longitudinal vortex

Wind Turbine Clustering and Equivalent Parameter Identification in Multitime Scales Based on the Deep Migration of Multiview Features

To improve the precision of wind farm multi-machine equivalence and multi-scene generalization, this paper proposes a method for wind turbine clustering and equivalent parameter identification in multi-time scales based on the deep migration of multi-view features. The proposed technique carries out multi-machine equivalence by leveraging the multi-view information from each turbine in a wind farm. Specifically, a deep spatio-temporal Improved Auto-Encoder is designed, jointly trained with the target clustering layer. IAE is used for mining multi-view latent characteristics of wind turbines orienting to grouping turbines to improve the model’s adaptability to multiple scenarios and divide turbines in an unsupervised manner. This method generates a visual heat map to represent the attended area of characteristics based on transfer learning and Class Activation Map to enable interpretability. In the next phase, this technique constructs a multi-objective optimization model by synthesizing the equivalent deviation of voltage, current, active power, and reactive power to further improve accuracy. It can identify the equivalent parameters of collector lines, the mechanical structure, and the control system at different time scales simultaneously via the black-box paralleled optimization method based on Bayes and Multi-arm Bandit. The proposed approach is evaluated on a typical double-fed wind farm with grid-side faults under various conditions of disturbing winds. Also, an ablation study is conducted to make analysis according to the two phases, i.e., turbine division and parameter identification. The results validate the accuracy and robustness of this method.

Experimental Investigation on Wake Characteristics of Wind Turbine and a New Two-Dimensional Wake Model

Experimental Investigation on Wake Characteristics of Wind Turbine and a New Two-Dimensional Wake Model

Aerodynamic Analysis of Onshore Commercial Large Scale Wind Turbine

In this study, the variations of yearly aerodynamic characteristics of horizontal axis wind turbines operating in an installed wind power plant (WPP) in detail was revealed by means of the blade element momentum theory and angular momentum theory. For this aim, five identical wind turbines of the three-bladed type having rated power of 2 MW located in an installed wind farm in Hatay province of Turkey were selected. According to the results obtained from horizontal axis wind turbines having rated power of Pr=2 MW, annual average turbine mechanical power output (P), power coefficient (CP), free-stream wind speed (U∞), and turbine rotor rotational speed (Ω) were obtained as 672.68 kW, 30.80%, 8.49 m/s and 12.81 rpm, respectively. Moreover, annual average axial flow induction factor (a), thrust coefficient (CT), thrust force (T) and blade tip speed ratio (λ) were calculated as 0.10, 0.34, 75.18 kN and 6.57, respectively.

Effects of continuously changing inlet wind direction on near-to-far wake characteristics behind wind turbines over flat terrain

The wake characteristics of a utility-scale wind turbine under realistic atmospheric boundary layer conditions are affected by the continuously changing wind direction arriving at the wind turbine. In the present study, the effects of continuous changes in the incoming wind direction were studied for a wind turbine on flat terrain, with the objective of understanding the wake characteristics of the wind turbine. Thus, understanding the effects of continuously changing incoming wind direction on the wake characteristics of wind turbines over flat terrain is important in the design of wind farm layouts, including in the design of offshore wind power plants. For this purpose, a computational fluid dynamics (CFD) approach using large-eddy simulations (LES) was adopted in the present study. An in-house LES-solver based on the actuator line (AL) aerodynamics technique was constructed in order to successfully capture the wake structure behind the wind turbine. First, experimental investigations on both a blade-only wind turbine scale model and a full 3D wind turbine scale model (isolated wind turbine) were conducted for a fixed inlet wind condition, the latter including the nacelle and the tower. Through a detailed comparison of the wind tunnel experimental and numerical results, the prediction accuracy of the in-house LES-solver was verified and validated for fixed inlet wind conditions. On the basis of the validation results obtained, and using the full 3D wind turbine scale model, the effects of the continuously changing inlet wind conditions on the wake characteristics in the near- and far-wake regions were numerically investigated. In addition, the effects of the wind turbine nacelle and tower on the wake characteristics were also investigated. The numerical results show that the most significant impact of the effects of the continuously changing wind direction was the rapid recovery of the mean velocity deficits in the wind turbine wake region. Further, at the x = 10D position (D is the rotor diameter) downstream of the wind turbine, the non-dimensional streamwise mean velocity was 0.93, which nearly matches the approaching flow speed, under an optimal tip speed ratio of 4.0, compared to the fixed wind direction scenario.

Aeroelastic and Aerodynamic Tests of Wind Turbine with Various Polygonal Towers

Traditionally, circular cross-section towers have been used as supporting systems of wind turbines, but weaknesses have become apparent with recent upsizing of wind turbines. Thus, polygonal cross-section towers have been proposed and used in Europe. In this study, the effects of polygonal cross-sections on the aeroelastic and aerodynamic characteristics of wind turbines were examined through a series of wind tunnel tests. Aeroelastic tests showed that a square cross-section tower showed instability vibrations, and polygonal cross-section towers showed limited vibrations for tower-only cases. However, for wind turbines with various polygonal cross-section towers, no instability vibrations were observed, and displacements increased proportionally to the square of mean wind speed. Furthermore, pressure measurements showed that local force coefficients changed largely depending on wind direction and azimuth angle. Local drag force coefficients decreased with increasing number of tower sides, approaching those of the tower-only case, and local lift force coefficients showed larger absolute values than those of the tower-only case. The maximum mean and fluctuating drag force and the maximum fluctuating lift coefficients at each height decreased with increasing number of tower sides.

A survey on development and prospect of wind turbines virtual synchronous control technology

The ongoing energy revolution has led to the gradual replacement of traditional synchronous generators by renewable enecorresponding authorrgy. This transformation of power generation mode reshapes power system dynamics and poses many challenges to reliable and efficient grid operation. With the continuous improvement of the penetration level of renewable energy represented by wind power in the power system, the synchronous mode of wind turbine will gradually become one of the main modes of system synchronization. In the case of coexistence of multiple synchronization modes, the synchronization mechanism of the whole power system will be fundamentally changed; at the same time, due to the response characteristics of wind turbine to the frequency and voltage dynamics of power grid and the traditional power supply, the synchronous mode of wind turbine will gradually become one of the main modes of system synchronization The frequency and voltage stability of power system also faces new challenges. The virtual synchronous generation technology can make the grid connected inverter simulate the operation mechanism of step generator and provide an effective method to solve the above problems. In this paper, the main technical routes to realize virtual synchronous control of wind turbines are summarized. From the aspects of stability analysis, control system optimization, performance analysis and evaluation, the research and engineering status of virtual synchronization technology in wind turbines are introduced, and the problems to be solved and technical requirements are prospected.

Aerodynamic improvement of Darrieus wind turbine

Until recently, vertical-axis wind turbines are less extensively developed in wind energetics. At the same time, there are a number of advantages in turbines of such type like their independence from the change of wind direction, lower levels of aerodynamic and infrasound noises, higher structural reliability (compared to horizontal engines), etc. With these advantages, vertical-axis wind turbines demonstrate promising capacities. Inter alia, the productiveness of such turbines can be refined through the aerodynamic improvement of the structure and comprehensive optimization of the rotor geometry. The main purpose of the presented paper is to aerodynamically improve vertical wind turbine in order to increase the efficiency of wind energy conversion into electricity. Within the framework of the classical theory of impulses, this article presents a study of the effect of variation in Reynolds number on the general energy characteristics of a vertical-axis wind turbine with two blades. The integral approach makes it possible to use a single-disk impulse model to determine the main specific indicators of the system. The power factor was calculated based on the obtained value of the shaft torque factor, which in turn was determined by numerically integrating the total torque generated by the wind turbine. To calculate the test problem, we used the classic NACA airfoils: 0012, 0015, 0018 and 0021. The proposed calculation algorithm makes it possible not to indicate the Reynolds number and corresponding aerodynamic coefficients at the beginning of the calculation, but to recalculate it depending on the relative speed, position of the airfoil and the linear speed of the airfoil around the circumference. Proposed modern design techniques can be helpful for optimization of vertical wind turbines.

Electromechanical Transient Modeling and LVRT Parameter Identification of Large Capacity Full Power Converter Wind Turbines Based on PSASP Program

Full power converter wind turbine is the main type of wind power, so the simulation calculation needs to establish accurate model parameters. This paper analyzes the model structure of PSASP program according to its low voltage ride through control and physical characteristics, and puts forward the parameter identification method of LVRT characteristics of full power converter wind turbine, and to use the LVRT data of 5. 5MW unit for parameter identification and simulation verification. This paper proposes that the electromechanical transient simulation can ignore the part of the generator model of the full power converter wind turbine, and simulates the grid side converter with the controlled current source. The main characteristics of LVRT are determined by the control system of the converter. In order to do the parameter identification, it is necessary to calculate and analyze the control characteristics of multiple measured data. First, determine the control mode, then determine the control parameters to complete the parameter identification. In this paper, the modeling conditions and model structure of the full power converter wind turbine are confirmed. The correlation between the parameters during the LVRT fault and the parameters during the LVRT recovery period and the LVRT characteristics is analyzed. In this paper, a parameter identification method is proposed to analyze the active current and reactive current during the LVRT fault, which has strong physical significance and operability. Based on the actual LVRT characteristics of 5. 5MW wind turbine, the parameter identification and simulation are carried out to verify the correctness of the method.

Research on the Influence of Shear Turbulence on the Aerodynamic Loads Characteristics of Wind Turbine

In order to accurately analysis the aerodynamic loads characteristics of the wind turbine under different turbulent wind conditions, the horizontal homogeneity in the flow field without a wind turbine and the numerical accuracy of the homogeneous flow field with a wind turbine were validated against the experimental results. The aerodynamic loads of the wind turbine were studied under the conditions of the uniform wind with a uniform turbulence intensity, the uniform wind with a shear turbulence intensity, the shear wind with a uniform turbulence intensity and the shear wind with a shear turbulence intensity. The results show that the increasing turbulence intensity leads to a small reduction in the torque of the wind turbine. Compared with uniform wind, shear inflow leads to a sine or cosine variation in the aerodynamic performance of the wind turbine and a reduction in the wind turbine’s thrust and torque. Compared with uniform turbulence intensity, shear turbulence intensity leads to a reduction in the wind turbine’s thrust and torque, and a more obvious phase lag effect, but it has little influence on the yawing moment and pitching moment.

Oscillation analysis of doubly-fed unit considering wind speed variation

Tower shadow effect and wind shear may cause power oscillation of the unit. In order to study the influence of tower shadow effect and wind shear on the output power of wind turbine, a doubly-fed turbine was taken as an example. Firstly, the influence of tower shadow effect and wind shear was considered to study the periodic power fluctuation characteristics of wind turbines. Then, according to the dynamic model of mechanical transmission mechanism, the influences of the inertia constants of generator, fan and the stiffness coefficient of the shaft system on the transient performance of the wind power generation system were considered respectively. Finally, a single machine infinite bus system model including wind speed model is built on PSCAD/EMTDC platform for simulation. The results show that the tower shadow effect and wind shear component can cause the power fluctuation of the turbine. When the power fluctuation frequency of the turbine is equal to the natural oscillation frequency of the wind turbine shafting, the resonance of the turbine occurs, and the amplitude of oscillation is the largest. Changing the transmission parameters will affect the power fluctuation amplitude and speed response speed of the unit.

Numerical study of aerodynamic characteristics on a straight-bladed vertical axis wind turbine with bionic blades

This paper has attempted to investigate the aerodynamic characteristics of the straight-bladed vertical axis wind turbine (VAWT) with bionic blades for better application of bionic blades to VAWTs. The study was based on the computational fluid dynamics numerical simulation (CFD numerical simulation) technique to investigate the differences of the power and tangential force coefficients of the wind turbine between the bionic blades and standard blades at three different tip speed ratios (TSRs = 1.38, 2.19, and 2.58) for the mainstream wind velocity of 8.0 m/s. The results showed that the average power coefficient enhancing effect of the bionic blade increases as the TSR increases, and the average power coefficient of the bionic blade is higher than that of the standard blade mainly because of the high wind energy utilization in the wave trough section. Moreover, the power coefficients of the wave crest sections for bionic blades are better than that of the standard blades at the downstream region of 200° < θ < 260°. This research provides a reference for the use of bionic blades in the straight-bladed VAWT.

Differences in wind farm energy production based on the atmospheric stability dissipation rate: Case study of a 30 MW onshore wind farm

The physical characteristics of a wind field significantly influence the energy produced by a wind farm because they are related to the available kinetic energy in the wake region created by wind turbine generators; they also affect wake recovery. To understand the correlation between the external environment and the amount of energy produced, a study based on the interaction between the power characteristics of wind turbines and atmospheric factors is required. In this study, the distribution characteristics of the turbulence dissipation rate (ε) with the regime were analyzed after classifying atmospheric stability by regimes. In addition, the normalized power of wind turbines was analyzed, and the difference in annual energy production (AEP) with the regime was presented. The AEP showed the best value in the slightly unstable regime and the lowest value in the stable regime. Finally, considering the annual mean wind speed at the study site, a difference of approximately 5%–7% was observed between the AEP under the neutral atmospheric regime and other atmospheric regimes. Further, this study highlights the impact of atmospheric stability regimes and the turbulence dissipation rate on energy production, thereby indicating the necessity of integrating these factors to predict the AEP of wind farms.