Characteristics Of Wind Turbine Research Articles

Study on aerodynamic performance of a combined vertical axis wind turbine based on blade element momentum theorem

The vertical axis wind turbine is mainly divided into lift type and drag type. The lift-type wind turbine has high-power coefficient, but it is difficult to start. The drag-type wind turbine is easy to start, but the power coefficient is low. Combined with the advantages of the two, a combined wind turbine with the lift blade and the drag blade is designed in this paper, which is expected to obtain higher power coefficient and better starting ability. For the combined wind turbine, based on the blade element momentum theorem, the analytical model of multiple-disk-multiple-streamtube is established. By solving the model with the program code, a method of analyzing the aerodynamic characteristics of the combined vertical axis wind turbine is given. The characteristics of attack angle, normal force, tangential force, and power coefficient of the combined wind turbine with different tip speed ratio are obtained by using the analytical model. The Navier–Stokes equation is solved by SST(Shear Stress Transfer) k–w turbulence model (four equations) in fluent 16.0 software. The tangential force coefficient, power coefficient and starting ability of the combined wind turbine are obtained by computational fluid dynamic method. The accuracy of the analytical model in solving the aerodynamic performance of the combined wind turbine is verified by comparing the solution results of the analytical model with the simulation results.

Research on sub/super‐synchronous oscillation suppression method for direct‐drive wind turbine based on energy compensation

A method to suppress sub/super-synchronous oscillation of direct-drive wind turbines based on energy compensation is proposed. First, the transient energy model of direct-drive wind turbine is built, and the negative damping energy terms that lead the oscillation of direct-drive wind turbine are extracted. On this basis, the expressions of voltage compensation terms corresponding to negative damping energy terms are derived by backward deduction, thus supplementary energy branches are constructed, and their impact on fundamental frequency characteristics of wind turbine is analyzed. And then, with the compensation energy of supplementary branches reaching the maximum and the increment of fundamental-frequency voltage being the minimum as the objective, and with the frequency-domain characteristic and fundamental-frequency voltage characteristic of control links being satisfied as constraints, a scheme to optimize the compensation coefficients of multiple branches is established. Finally, the model of direct-drive wind turbine is built in RT-LAB for hardware-in-the-loop tests. Simulation results verify that, the method can realize fast frequency-dependent suppression of sub/super-synchronous oscillation in different frequency bands concerning different grid strengths.

Transient voltage mechanism and influencing factors of wind power HVDC transmission system

HVDC transmission is an important approach to delivery large-scale wind power for a long distance. When the commutation failure occurs, the voltage of sending end will fluctuate dramatically, which threatens the stable operation of wind farm. Meanwhile, different characteristics of wind turbines will further affect the transient voltage of sending end, so the impact of wind farm on the transient voltage must be considered, especially for the high proportion of wind power generation. Firstly, the sending end transient voltage characteristics are analyzed and the mechanism of transient overvoltage caused by commutation failure is revealed. Then, doubly-fed wind power generation systems with different control modes are modeled, and the dynamic reactive power response capabilities of them are studied, so as to analyze the influence of the doubly-fed induction generator (DFIG) control modes on the transient overvoltage. Finally, a simulation example is established which verifies the correctness of the theoretical analysis. The results show that when DFIG adopts the constant voltage control strategy with the quickly response speed of the converters, it has stronger reactive power output capability, and can suppress the transient overvoltage, which is beneficial to the safe and stable operation of the power grid.

Aerodynamic Characteristics of Airfoil and Vertical Axis Wind Turbine Employed with Gurney Flaps

In the present studies, the effects of Gurney flaps on aerodynamic characteristics of a static airfoil and a rotating vertical axis wind turbine are investigated by means of numerical approaches. First, mesh and time step studies are conducted and the results are validated with experimental data in good agreement. The numerical solutions demonstrate that the usage of Gurney flap increases the airfoil lift coefficient CL with a slight increase in drag coefficient CD. Furthermore, mounting a Gurney flap at the trailing edge of the blade increases the power production of the turbine considerably. Increasing the Gurney flap height further increases the power production. The best performance found is obtained for the maximum height used in this study at 6% relative to the chord. This is in contrast to the static airfoil case, which shows no further improvement for a flap height greater than 0.5%c. Increasing the angle of the flap decreases the power production of the turbine slightly but the load fluctuations could be reduced for the small value of the flap height. The present paper demonstrates that the Gurney flap height for high solidity turbines is allowed to be larger than the classical limit of around 2% for lower solidity turbines.

Wind Tunnel Experiments and Numerical Study on Performance Characteristics of an H-type Vertical Axis Wind Turbine in the Spanwise Direction

The aerodynamic forces and vortex characteristics of an H-type Vertical Axis Wind Turbine (VAWT) become complicated because of dynamic stall, particularly in the three-dimensional impact on the blade spanwise direction. This study focused on the evaluation of the aerodynamic performance and vortex characteristics of an H-type VAWT in the spanwise direction by numerical simulations and wind tunnel experiments. Pressure acting on the blade surface was obtained from multiport pressure measurement devices by wind tunnel. Meanwhile, the vortex field around different blade sections was investigated through numerical simulations. The stall behavior was analysed by comparing the results of numerical simulations and experiments. As a result, the tangential force of single blade was mainly contributed at the chordwise position of x/c≤0.4c and the power of single blade was mainly contributed at the azimuthal angle range of 60°≤θ≤150° in the blade section position region of 0≤z/(H/2)≤0.7. At the section position of z/(H/2)=0.5, the initial flow separation was found at the suction side and progressed forward to the leading edge. With the increase of the tip speed ratios, the decreasing position of the averaged local power coefficient of each section was closer to the middle section of z/(H/2)=0, and the attenuation speed became faster. The power coefficient reductions at the blade section position of z/(H/2)=0.9 were 38.29%, 46.78% and 56.42% when the tip speed ratios were 1.38, 2.19 and 2.58, respectively. The results of this study provided a better understanding of the development of the performance characteristics and vortex characteristics of H-type VAWT.

First comparison of the electrical properties of two grid emulators for UVRT test against field measurement

The technical rules for connecting turbines to the medium, high or extra-high voltage grid in Germany require the certification of the UVRT characteristics of wind turbines. The state-of-art voltage divider-based test equipment, also named UVRT-Container, is well equipped for executing UVRT tests in field. To conduct the UVRT in field the full wind turbine should be already installed. A second option to perform UVRT tests are system level test benches. They enable the testing of the nacelle. The components that are not actually present, such as the turbine tower or the blades, are emulated via a mechanical hardware in the loop (HiL) system. In this work, for the first time, the performance of two different grid simulators installed at the DyNaLab at Fraunhofer IWES and at the CWD at RWTH Aachen University is compared with a field measurement of the same type of wind turbine. Thus, not only a system test bench measurement is compared to a field measurement. Rather, two system test benches with individual technical approaches are additionally compared with each other. The focus of this work is to investigate the characteristics of the grid simulators within the steady-state range of the UVRT tests to replicate identical fault shapes on the test benches and in the field.

Aerodynamic and aeroacoustic performance investigations on modified H-rotor Darrieus wind turbine

The present paper investigates the aerodynamic and aeroacoustic characteristics of the H-rotor Darrieus vertical axis wind turbine (VAWT) combined with very promising energy conversion and steering technology; a fixed guide-vanes. The main scope of the current work is to enhance the aerodynamic performance and assess the noise production accomplished with such enhancement. The studies are carried out in two phases; the first phase is a parametric 2D CFD simulation employing the unsteady Reynolds-averaged Navier-Stokes (URANS) approach to optimize the design parameters of the guide-vanes. The second phase is a 3D CFD simulation of the full turbine using a higher-order numerical scheme and a hybrid RANS/LES (DDES) method. The guide-vanes show a superior power augmentation, about 42% increase in the power coefficient at λ = 2.75, with a slightly noisy operation and completely change the signal directivity. A remarkable difference in power coefficient is observed between 2D and 3D models at the high-speed ratios stems from the 3D effect. As a result, a 3D simulation of the capped Darrieus turbine is carried out, and then a noise assessment of such configuration is assessed. The results show a 20% increase in power coefficient by using the cap, without significant change in the noise signal.

Is the Large-Scale Development of Wind-PV with Hydro-Pumped Storage Economically Feasible in Greece?

The achievement of the long-term national energy targets in Greece for large-scale integration of wind and solar energy may be facilitated by the development of hydro-pumped storage projects. In light of the above, technical aspects related with the operation of the Greek power system and its ability to absorb renewable energy are analyzed in connection with the role of hydro-pumped storage and relative economic aspects. The aim of this work is to assess the potential contribution of hydro-pumped storage projects and estimate the capacity magnitude order to support large-scale wind and photovoltaic (PV) integration in Greece. For this purpose, scenarios for the Greek power system with focus on Wind and PV development, in conjunction with hydro-pumped storage capacity, are developed, and results for current situation and reference years 2030 and 2050 are presented. For the simulation, among others, high resolution mesoscale wind data for a typical year in the whole Greek territory are used for the steady state simulation of the Greek power system, in order to better estimate the power that could be generated from installed wind turbines, taking into consideration technical characteristics of a typical commercial wind turbine. Results indicate the need of gradual development of hydro-pumped storage in parallel with the large-scale integration of wind and PV capacity into the Greek power system. In addition, the feasibility of the examined scenarios is supported from the low cost of wind and PV generation. In the case of Greece, thanks to the complex morphology and hydraulic conditions of the country, hydro-pumped storage composes an efficient and low-cost storage solution.

Visualization of aerodynamic forces and flow field on a straight-bladed vertical axis wind turbine by wind tunnel experiments and panel method

This paper investigated the evaluation of the aerodynamic performance and vortex characteristic of a straight-bladed Vertical Axis Wind Turbine (VAWT) in the spanwise direction. To observe the aerodynamic forces characteristics, pressures acting on the blade surface were measured by a multiport pressure measurement device. Pressure measurement was carried out in the spanwise sections of z/(H/2) = 0, 0.4, 0.70, 0.8 and 0.90 with wind tunnel experiments. Meanwhile, panel method based on the lifting surface theory was used to study the flow characteristics of VAWT. As a result, it was clarified that the absolute value of radial force coefficient from measurement took the maximum value at the upstream region around the azimuth angle of 100° and became small at the downstream region. Moreover, the radial force coefficient of the experimental value was significantly affected by the three-dimensional and decreased as it approached the blade tip. For the flow field, the circulation amount contour of the vertical vortex was wider near the blade center and became narrower around the blade tip in the blade spanwise direction. This study provided a better understanding of the development of aerodynamic forces and vortex characteristic through pressure measurements and panel method calculations.

Performance of Crossflow Wind Turbines in In-line Configuration and Opposite Rotation Direction

Wind energy sources must be investigated to produce electrical energy from a renewable source. Crossflow wind turbines are suitable for use because they have several advantages such as self-starting ability, low noise, and excellent stability. They have the potential to be applied as small wind turbines in urban districts because of their small maximum coefficient of power (Cp), which is 10% of that of other small wind turbines. To enhance the performance of crossflow wind turbines, we changed the turbine to rotate in the opposite direction in the in-line configuration. Turbine performance testing was tested using a wind tunnel. The characteristics of crossflow wind turbines were investigated, then turbine performance was analyzed and discussed. The maximum power coefficient obtained was 0.169 (Cp) with the configuration of 12 turbine blades at a wind speed of 10 m/s. The maximum torque coefficient obtained was 0.703. The overall results show that the crossflow wind turbine in in-line configuration with opposite rotation can improve the performance of wind turbines.

Technique for testing small wind turbines by method of acceleration in the wind tunnel and in the field

A technique is proposed for obtaining aerodynamic and mechanical characteristics of wind turbines – the wind energy conversion coefficient and the relative torque of the wind turbine as a function of their speed with respect to the intensity of the wind wheel acceleration from the moment of its start until the synchronous speed at constant wind speed. The proposed technique simplifies and significantly reduces the time for experimental testing of wind turbine wheels.

Identification of optimum wind turbine parameters for varying wind climates using a novel month-based turbine performance index

The capacity factor (CF) and power coefficient (Cp) are two important wind turbine characteristics. CF describes the power generation capacity during a given period, and Cp describes the efficiency of the wind turbine. Both quantities depend on the rated wind speed. Determining the optimal rated wind speed that maximizes a function of CF and Cp that is directly related to a wind turbine’s output wind power density thus is of utmost importance as it leads to a maximum energy output. This paper proposes a novel Month-based Turbine Performance Index (MTPI) that considers the hourly mean wind speed data month-wise and enables the evaluation of this desired optimum rated turbine speed (Vr,opt) for a given site. Here, the 2-parameter Weibull distribution is employed as a single tool to parameterize the wind speed data and determine the wind speed probability density function, wind power density, vertical wind shear, CF, and Cp of the wind turbine. The examined stations taken for the analysis are from Trivandrum, Ahmedabad, and Calcutta in India. Our index is especially important in regions with intra annular variability, since it is the first to consider monthly instead of annual data.

WIND TURBINE SIMULATION AND CONTROL USING SQUIRREL-CAGE INDUCTION GENERATOR FOR DFIG WIND ENERGY CONVERSION 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 3 kW. 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.

Performance Characteristics of A Micro Wind Turbine Integrated on A Noise Barrier

Micro wind turbines can be structurally integrated on top of the solid base of noise barriers near highways. A number of performance factors were assessed with holistic experiments in wind tunnel and in the field. The wind turbines underperformed when exposed in yawed flow conditions. The theoretical cosθ theories for yaw misalignment did not always predict power correctly. Inverter losses turned out to be crucial especially in standby mode. Combination of standby losses with yawed flow losses and low wind speed regime may even result in a net power consuming turbine. The micro wind turbine control system for maintaining optimal power production underperformed in the field when comparing tip speed ratios and performance coefficients with the values recorded in the wind tunnel. The turbine was idling between 20%–30% of time as it was assessed for sites with annual average wind speeds of three to five meters per second without any power production. Finally, the field test analysis showed that inadequate yaw response could potentially lead to 18% of the losses, the inverter related losses to 8%, and control related losses to 33%. The totalized loss led to a 48% efficiency drop when compared with the ideal power production measured before the inverter. Micro wind turbine’s performance has room for optimization for application in turbulent wind conditions on top of noise barriers.

Control and Investigation of Operational Characteristics of Variable Speed Wind Turbines with Doubly Fed Induction Generators

This article deals with the analysis, modeling, and control of the doubly-fed induction generator (DFIG) for wind turbines. The DFIG wind turbine can deliver more energy to the grid. There are some different methods to modify the DFIG system in order to accomplish the stator reactive power proposed. One of these methods is to modify the DFIG system for nominal voltage to evaluate cost and materials-efficiency consequences. A specific control strategy is implemented according to the vector control strategy. The proportional-integral (PI) regulators used are simple and precise controllers. This type of regulation, which is closed-loop rotor currents, allows adjustment of the sliding of the DFIG. This gives a good adjustment of the powers of the stator and the rotor. The percentage error of the simulation is less than 2 %. The results obtained in these investigations show that it is possible to adjust the powers of the stator, even with a variation of the parameters. The developed method will allow achieving the maximum efficiency of the wind energy conversion chain. The objective of this article is to optimize the quality of energy generated by wind turbines by controlling the reactive stator power and reducing the losses of the energy of the reactive stator power, which must be a physically minimal value. The results will be presented in the Matlab - Simulink environment.

Robust wind turbine emulator design using sliding mode controller

This work deals with the development of a real-time wind turbine emulator (WTE) for laboratory purpose using a robust sliding mode controller (SMC). The application of power electronic converters with various control strategies in machine control facilitate the imitation of a practical wind turbine characteristics using a separately excited DC motor. The SMC theory is used here to develop a control law that governs the system to track the reference current set by the mathematical model of the wind turbine to get the desired output. The static, dynamic characteristics and also the transient responses of the WTE are satisfactorily reproduced by the proposed SMC method. To validate the performance of WTE prototype, it is tested under various operating conditions. A performance comparison of the proposed SMC with the existing proportional and integral (PI) controller in terms of tracking speed, peak overshoot and settling time are discussed in detail. The experimental result analysis confirms that the proposed control scheme improves the imitation of the real-time wind turbine characteristics and performs efficiently under both steady-state and transient conditions.

Development of a wind turbine driven by longitudinal vortex: Wind tunnel experiment to investigate the basic characteristics of the wind turbine using a single circular cylinder blade

In this study, the basic rotation and output torque characteristics of a longitudinal vortex wind turbine (LV-WT) were investigated by using a wind tunnel experiment. This wind turbine uses a circular cylinder with a diameter d as the driving blade, and a ring-shaped plate with width w ​= ​d is installed behind the cylinder blade with a gap s. A steady lift force to sustain the rotational motion is generated by the longitudinal vortex formed near the intersection of the cylinder blade and the ring plate. The gap ratio s/d is the most dominant parameter for the performance of the LV-WT, and the output torque and efficiency are maximum at s/d ​= ​0.35. A wider ring plate and flanges attached to the blade are promising techniques to improve the performance of the LV-WT. The lift coefficient Cl is approximated by a decreasing linear function of the velocity ratio λ = (rotational velocity V)/(free flow velocity U), as predicted in the preceding numerical study of the authors. Using the drag coefficient determined by the loaded experiment, the performance characteristics of LV-WT are predicted for the widely varying conditions.

Transient modelling of doubly‐fed induction generator based wind turbine on full operation condition and rapid starting period based on low voltage ride‐through testing

Transient simulation model of doubly-fed induction generator-based wind turbine has a complex model structure and considerable control parameters. An accurate simulation model is especially important for studying the static and transient characteristics of doubly-fed induction generator-based wind turbine and the grid-connected system. Based on the measured data of low voltage ride-through testing, the integrated parameter identification method is proposed here. Combined with the time-domain simulation analysis, curve fitting is used to determine the control strategy of doubly-fed induction generator-based wind turbine. The improved genetic algorithm is used to identify the generator parameters, power control parameters, and resistance of Crowbar of doubly-fed induction generator-based wind turbine. Combined with the electrical parameters provided by the wind turbine manufacturer, electromagnetic transient model on full operation condition and rapid starting period, corresponding to a measured doubly-fed induction generator-based wind turbine in West Inner Mongolia Power Grid, is then established, which can operate in the full wind speed range and quickly enter the stable state within 1 s after start-up. Comparison of simulation results and measured data shows that the established electromagnetic transient simulation model using parameters identified by the proposed method can accurately reflect the key characteristics of doubly-fed induction generator-based wind turbine.

STUDI EKSPERIMENTAL PERFORMANSI TURBIN SAVONIUS DI PESISIR PANTAI KABUPATEN DEMAK TERHADAP DAYA LISTRIK YANG DIHASILKAN

<p><em>Energy from fossil fuels consisting of petroleum, coal, natural gas containing raw material for energy fulfillment in Indonesia is still very central through the use of raw materials from renewable energy is still very low. In Indonesia the potential for renewable energy such as wind energy needs to be optimized. One of the uses of wind energy is through savonius wind turbine as electricity generators. Characteristics of savonius wind turbine with vertical axis rotors which gave a simple shape, and that able to control low speeds. This is in accordance with regions in Indonesi which have low average speeds. This experimental study, aims to determine the description of wind potential and determine the performance of savonius wind turbines on the coast of Demak regency on the electrical energy produced. Savonius wind turbine used is made of galvalum material in the form of an S type rotor with diameter 1.1 m and height 1.4 m, using pulley transmission system with multiplication ratio 1:6 dan using generator type PMG 200 W. This research uses the method experiment. Data collection in the form of wind speed, humidity, temperature, rotor rotation speed, voltage and electric curret is carried out at 14.30 to 17.30 Western Indonesian Time. Data Analysis in this study uses quantitative descriptive analysis. The result showed the potential of wind on the coast of Demak regency have an average wind speed of 2,02 m/s with a temperature of 31</em><em>,</em><em>34 </em><em><sup>0</sup></em><em>C and humidity of 76,96. And the performance of the installed wind turbine produces the highest power 3.5 watt with an electric power coefficient of 0,181 and tip speed ratio around 1,75. From these result, the potensial of wind with performance savonius turbine can generate electricity used for pond lighting in the village Berahan Kulon Kecamatan Wedung. </em><em></em></p>

Design and implementation details of a low cost sensorless emulator for variable speed wind turbines

In this paper, a low cost wind turbine emulator (WTE) is designed and implemented. The aim is accurately simulating the nonlinear behaviors and characteristics of a real wind turbine. It is well known that each wind turbine has its own power coefficient characteristic. This work contains an analysis of the WTE by considering the main power coefficient models known in literature. Speed sensor is one of the most important component used to provide the shaft speed information. This latter will increase greatly the system cost and volume of the control scheme. In our work, we propose cheapest solution by using a second-order sliding-mode speed observer based on super-twisting algorithm. Note that the accurate speed estimation is essential to maintain good simulation of wind turbine characteristics. The WTE closed loop operation is ensured by the fuzzy logic technique. Experimental results confirm the effectiveness of the proposed sensorless WTE solution.