Single Rotor Wind Turbine Research Articles

Improved dfig dftc by using a fractional-order super twisting algorithms in wind power application

Background: The direct flux and torque control are a robust, simple, and alternative approach control formulation that does not require decomposition into symmetrical components; the direct flux and torque control schemes have been proved to be preponderant for doubly-fed induction generators due to the simple implementation.
 Aim: This work presents the minimization of electromagnetic torque and rotor flux undulations of doubly-fed induction generators using fractional-order super twisting algorithms and modified space vector modulation techniques.
 Methods: The main role of direct flux and torque control is to regulate and control the electromagnetic torque and rotor flux of doubly-fed induction generators for wind turbine systems. The direct flux and torque control is a traditional control algorithm and robust technique. Fractional-order super twisting algorithms are a new and proposed nonlinear controller; characterized by a robust controller and a simpler algorithm, which gives a good harmonic distortion of current compared to other methods.
 Novelty: The A fractional-order super twisting algorithm is proposed. Proposed nonlinear controller construction is based on the traditional super twisting algorithm and fractional calculus to obtain a robust controller and reduces the electromagnetic torque and rotor flux undulations of doubly-fed induction generators. We use in our study a 1.5 MW doubly-fed induction generator integrated into a single-rotor wind turbine system to minimizes the electromagnetic torque, stator current, rotor flux undulations. As shown in the results figures using fractional-order super twisting algorithms ameliorate effectiveness especially minimizes the electromagnetic torque and rotor flux, and minimizes harmonic distortion of stator current (0.16 %) compared to the traditional control scheme.
 Results: As shown in the results figures using fractional-order super twisting algorithms ameliorate effectiveness especially minimizes the electromagnetic torque and rotor flux, and minimizes harmonic distortion of stator current (0.16 %) compared to the traditional control scheme.
 Conclusion: The direct flux and torque control are a robust, simple, and alternative approach control formulation that does not require decomposition into symmetrical components; the direct flux and torque control schemes have been proved to be preponderant for doubly-fed induction generators due to the simple implementation.

Dynamic Analysis of a Single-Rotor Wind Turbine with Counter-Rotating Electric Generator under Variable Wind Speed

This paper presents a theoretical study of the dynamic behaviour of a wind turbine consisting of a wind rotor, a speed increaser with fixed axes, and a counter-rotating electric generator, operating in variable wind conditions. In the first part, the dynamic analytical model of the wind turbine mechanical system is elaborated based on the dynamic equations associated with the component rigid bodies and the linear mechanical characteristics associated with the direct current (DC) generator and wind rotor. The paper proposes a method for identifying the coefficients of the wind rotor mechanical characteristics depending on the wind speed. The numerical simulations performed in Simulink-MATLAB by MathWorks on a case study of a 10 kW wind turbine highlight the variation with the time of the kinematic parameters (angular speeds and accelerations), torques and powers for wind system shafts, as well as the mechanical efficiency, both in transient and steady-state regimes, considering variable wind speed. The analytical and numerical results are helpful for researchers, designers, developers, and practitioners of wind turbines aiming to optimise their construction and functionality through virtual prototyping.

Improved Rotor Flux and Torque Control Based on the Third-Order Sliding Mode Scheme Applied to the Asynchronous Generator for the Single-Rotor Wind Turbine

In this work, a third-order sliding mode controller-based direct flux and torque control (DFTC-TOSMC) for an asynchronous generator (AG) based single-rotor wind turbine (SRWT) is proposed. The traditional direct flux and torque control (DFTC) technology or direct torque control (DTC) with integral proportional (PI) regulator (DFTC-PI) has been widely used in asynchronous generators in recent years due to its higher efficiency compared with the traditional DFTC switching strategy. At the same time, one of its main disadvantages is the significant ripples of magnetic flux and torque that are produced by the classical PI regulator. In order to solve these drawbacks, this work was designed to improve the strategy by removing these regulators. The designed strategy was based on replacing the PI regulators with a TOSMC method that will have the same inputs as these regulators. The numerical simulation was carried out in MATLAB software, and the results obtained can evaluate the effectiveness of the designed strategy relative to the traditional strategy.

Development and Performance Investigation of a Unique Dual-rotor Savonius-type Counter-rotating Wind Turbine

Wind power is sustainable and prevalent virtually all over the globe. However, the conversion efficiency of the conventional single-rotor wind turbine (SRWT) is still far from satisfactory. The dual-rotor counter-rotating concept is among the reliable techniques used to enhance the efficiency of a wind energy conversion device for its renowned effectiveness. This study aims to investigate the performance of a Savonius dual/twin-rotor system, particularly in low-speed wind conditions while employing the counter-rotating technique. The evaluation of this technique is presented in terms of aerodynamic characteristics, including the power and torque coefficients. The results have shown that the new concept was able to improve the performance of the system extensively and was capable of operating in a lower wind speed condition. Compared to a single-rotor system, an additional 42% more torque was possible owing to the existence of a second rotor in the new system. The results have also revealed that the conversion efficiency of the system has been enhanced substantially. A corresponding average power coefficient of up to 28% was achieved. The present technique is thought to be promising for wind energy conversion systems, including sites with poor wind conditions.

Analysis of Airconditioning System Using Single-Rotor Wind Turbine Power, Dual Rotor Wind Turbine Power, and Ducted Dual Rotor Wind Turbine Power As Input to Compressor

As vapor compression refrigeration system is the best-suited system used in the present scenario due to its various advantages, in the present paper MATLAB analysis is done for the analysis of simple VCR to calculate COP and refrigeration effect.in the present paper R134a refrigerant is used as a refrigerant.as we know a certain amount of power is used to drive the compressor input in conventional VCR system uses electrical power to convert into mechanical shaft rotation with certain rotation, power and torque.in this paper specific power torque and rotation is given to the compressor without any electrical motor. the power obtains from an SRWT, DRWT, and DDRWT with specific torque power and rotation. then after analysis is carried out to get the COP and Refrigeration Effect.

On critical aeroelastic modes of a tri-rotor wind turbine

This paper presents the first investigation on a high-fidelity linear time-invariant aeroelastic model of multi-rotor wind turbines with three-bladed rotors. The modeling method developed in this work integrates the rotor model from the aeroelastic single-rotor wind turbine stability software HAWCStab2 with a model of the support structure in the aeroelastic multi-body tool HAWC2.The method is used to analyze the linear aeroelastic response of the DTU 30 MW tri-rotor wind turbine to see if the system experiences any aeroelastic instabilities or has any critical low damped modes. Furthermore, a comprehensive aeroelastic analysis of the DTU 10 MW wind turbine is performed and used to compare rotor modes between the two types of wind turbines. The results from the aeroelastic analysis are visualized using a developed mode-clustering algorithm utilizing an extension of the modal assurance criterion.The results show that the tri-rotor wind turbine does not have any aeroelastic instabilities. Comparing the rotor modes of the single-rotor and the tri-rotor wind turbine shows that the dynamics of the lower rotors change significantly both in natural frequencies and damping ratios. This means that it can be sub-optimal to use the rotor from a single-rotor on a multi-rotor configuration. It is found that for multi-rotor wind turbines with arm structures the vertical arm-bending modes are low damped and therefore at risk of aeroelastic instabilities in addition to the side-side tower modes.The aeroelastic multi-rotor wind turbine modeling framework is verified by comparing frequency response functions with a nonlinear model in HAWC2.

CFD Analysis of Torque and Power for Single Rotor, Dual Rotor, and Ducted Dual Rotor Wind Turbine

With the present advancement, a wind turbine needs a wind rotor with high torque and power. The present study aims to enhance the torque and power of wind turbine by employing the ducted dual rotor. In this regard, CFD analysis is performed to analyze the torque and power produced for horizontal axis single rotor bare wind turbine, dual rotor wind turbine, and convergent-divergent ducted type dual rotor wind turbine. The comparative study is conducted to enhance the power and torque for the aforementioned rotor type. The results highlight the maximum value of torque for a dual ducted wind turbine is 36.9% more than a dual rotor at 16 m/s of wind velocity and 92.2 % more than a single rotor at 16 m/s of wind velocity, and the maximum value of the power produced for a dual ducted wind turbine is 40.48% more than a dual rotor at 16 m/s of wind velocity and 139.66% more than a single rotor at 16 m/s of wind velocity. Therefore result suggested that a dual ducted wind turbine is better than a single rotor wind turbine.

A novel methodology for analyzing modal dynamics of multi-rotor wind turbines

A multi-rotor wind turbine (MRWT) is accepted as a novel solution in reducing the rotor size without decreasing the energy harvesting capability compared to a single-rotor wind turbine (SRWT). However, there is no systematic methodology available for obtaining the modal properties of MRWTs. This paper presents a novel methodology and systematic modeling method of modal dynamics with comprehensive numerical simulations and analyses of MRWTs. In the methodology, Coleman transformation is employed to convert the nonlinear time-variant dynamics formulation of a MRWT into a set of linear time-invariant dynamic equations. Using HAWC2 and HAWCStab2 a method to establishing high-fidelity linear time-invariant dynamic models is presented. The structural modal dynamics of a tri-rotor wind turbine is systematically investigated by using modal analysis theory and interpreting the rotor speed-dependent dynamics visualized in a Campbell diagram. The investigation shows that rotor modes on a MRWT have similar behavior as for a SRWT and that low torsional stiffness of the rotor attachment point affects the first flapwise backward whirling modes by decreasing the corresponding natural frequencies. Moreover, the low torsional stiffness results in a delayed splitting of the asymmetric flapwise rotor modes. The simulations and analyses result verified the proposed dynamic modeling method. The major contributions in this paper provide the essential insights and guidance in the design of MRWTs but also for SRWT with slender towers.

Aerodynamic Performance and Flow Structure Investigation of Contra-rotating Wind Turbines by CFD and Experimental Methods

Wind tunnel experiment was carried out to measure mechanical power of the contra-rotating wind turbine (CRWT) and single rotor wind turbine (SRWT) under various working conditions. Particle Image Velocimetry (PIV) device was employed to measure the transient flow field on the meridional plane of the rotors. The azimuthal velocity vector, magnitude and streamline were obtained by the average PIV image of ten intervals in a rotation cycle. CFD model of steady flow was developed to predict aerodynamic performance and flow structure of the CRWTs using S-A turbulent model. The single channel model was employed with periodic boundary condition. CFD results were validated with wind tunnel test in literature and experiment in this paper. Results show that CFD method has a satisfied accuracy in power prediction, with a relative error less than 34%. The azimuthal average velocity distributions predicted by experimental and CFD methods are close and the maximum value are approximate to each other. Results demonstrate a high velocity zone at the outside of the front rotor tip and a low velocity zone near the middle of the rear rotor. CRWT has a complicated flow structure. Particularly at the rear rotor, flow becomes uneven and streamline curvatures are more ununiformed.

Modal Analysis of a Quad-Rotor Wind Turbine

Unlike Single-Rotor wind turbines, stability analysis of Multi-Rotor wind turbines is still in its initial stages. This paper presents the modal analysis of a Quad-Rotor wind turbine and identifies the new modes or possible instability modes that are otherwise not present on a Single-Rotor wind turbine. Multi-Blade Coordinate transformation scheme is adapted to a Quad-Rotor wind turbine to write the system’s equation of motion in fixed-reference frame followed by Eigenvalue analysis to determine the natural frequencies and mode shapes of the Quad-Rotor wind turbine. A Campbell diagram of the Quad-Rotor wind turbine is presented. Results indicate that the Quad-Rotor turbine is soft-soft to the first tower modes (fore-aft, side-side, and torsion). Furthermore, the modes with low natural frequency other than the tower modes are a combination of tower, boom, and blade modes. Therefore, due to the presence of blade modes, the modal frequency of these modes increases or decreases with increasing rotor speed due to centrifugal stiffening.

Parametric Study on a Performance of a Small Counter-Rotating Wind Turbine

A small Counter-Rotating Wind Turbine (CRWT) has been proposed and its performance has been investigated numerically. Results of a parametric study have been presented in this paper. As parameters, the axial distance between rotors and a tip speed ratio of each rotor have been selected. Performance parameters have been compared with reference to a Single Rotor Wind Turbine (SRWT). Simulations were carried out with Computational Fluids Dynamics (CFD) solver and a Large Eddy Scale approach to model turbulences. An Actuator Line Model has been chosen to represent rotors in the computational domain. Summing up the results of simulation tests, it can be stated that when constructing a CRWT turbine, rotors should be placed at a distance of at least 0.5 D (where D is rotor outer diameter) or more. One can then expect a noticeable power increase compared to a single rotor turbine. Placing the second rotor closer than 0.5 D guarantees a significant increase in power, but in such configurations, dynamic interactions between the rotors are visible, resulting in fluctuations in torque and power. Dynamic interactions between rotor blades above 0.5 D are invisible.

Numerical analysis on the performance of Dual Rotor wind turbine

This study investigates the aerodynamic performance of wind turbines aiming to maximize the power extracted from the wind. The study is focusing on the effect of introducing a second rotor to the main rotor of the wind turbine in what is called a dual rotor wind turbine (DRWT). The numerical study took place on the performance of small-scale model of wind turbine of 0.9 m diameter using S826 airfoil.
 Both the Co-rotating and Counter rotating configurations were investigated at different tip speed ratios (TSR) and compared with the performance of the single rotor wind turbine (SRWT). Many parameters were studied for dual rotor turbines. These include the spacing between the two rotors, the pitch angle of the rear rotor and the rotational speed of ratio rear to front rotor. Three-dimensional simulations performed and employed using CFD simulations with Multi Reference Frame (MRF) technique.
 The Co Rotating Wind Turbine (CWT) and Counter Rotating Wind Turbine (CRWT) found to have better performance compared to that of the SRWT with an increase ranging from 12 to 14% in peak power coefficient. Moreover, the effect of changing the pitch angle of the rear rotor on the overall performance found to be of a negligible effect between angles 0⁰ until 2⁰ degrees tilting toward the front rotor. On the other hand, the ratio of rotational speed of the rear rotor to the front rotor found to cause a further increase in the peak performance of the CWT and CRWT ranging from 3 to 5%.

Optimized manufacturing of the small dual wind turbine used to generate electricity in central Iraq areas

Start your Due to the importance of generating electricity from wind turbines, single rotor wind turbine and dual rotor wind turbine. There was a need to design and manufacture the turbine system operating in both types mentioned above and have advantages to increase the generation of electric power. The aim of this work was to generate electrical power at a wind speed of up to 1m/s and more to achieve this wind speed and direction of the wind were adopted from tables of the Zerbatiya Station of the Wasit Governorate (Geographically located in central Iraq). The simulation was used to generate rotational speed for front and rear blades from 1m/sec to 13m/sec. A new idea was used to induce the dual small wind turbine to generate electrical power at low speed (1m/sec). In this case, there is latent energy in the surrounding wind turbine, but it is not that helps to rotate the wind turbine. To apply this idea the starter motor is used. Passive magnetic bearing supports have been used to reduce friction of the rotors this will reduce losing of wind energy. Brakes are the mechanical devices which aimed to slow or shut down the machine. They are also designed to prevent moving after stopping. Finally, the Genetic Algorithm (GA) was used within the program for the purpose of obtaining the best amount of power generated. All the above were for the purpose of determining the best position for blades at different speeds to generate electricity by using Permanent Magnetic Synchronous Generator (400W).Results of this paper: (a)-The starter motor proved good performance when using it. (b)-Using passive magnetic bearing proved effect on increase the power generation. (c)-Mechanical brakes work to stop the system within a period of time and not immediately as this will negatively affect the performance of the system.

Condition Monitoring for Single-Rotor Wind Turbine Load Sensors in the Full-Load Region

Incipient faults on blade load sensors can impede the sound performance of a wind turbine, leading to increasing loads over time and severe blade degradation. As such, knowledge of the blade load sensors’ health is essential for ensuring effective load reduction by means of individual pitch control. This paper presents a condition monitoring strategy for the blade load sensors based on estimation of the loads acting on the rotor blades in the full-load region. Fault detection is achieved via appropriate residual generators, the statistical properties of which are used to design change detectors robust against measurement noise and wind field stochasticity. Specifically, a Generalized Likelihood Ratio Test for the t-LocationScale distribution is developed for ensuring robust detection of sensor blade faults. The proposed method is evaluated in a high-fidelity simulator under non-uniform wind scenarios. The simulation results show that detection of multiplicative faults on the blade load sensors is achieved even in absence of knowledge of the local wind speed.

Experimented Examination of Power Produced for Dual Rotor Wind Turbine over Single Rotor Wind Turbine

As that wind energy is the vital energy resource which can be used widely to facilitate humane being prolong till the time nature or so called wind is there main aim of this paper is increase extraction percentage of energy from wind using dual rotor wind turbine connected on same axis, analysis were carried out experimentally for the increased power coefficient CP. It has been compared and found that with respect to single rotor or turbine dual wind power is having larger value of CP and torque, moreover instead of using one turbine for two turbine on same axis the value of CP increases with the better balancing stability, further the comparison is made with the performance of single bare wind turbine . Compare to that of single rotor if we used two rotor on same shaft then the torque and power increases on the other hand we will also get large stability due to weight balance condition and was found that large amount of energy can be extracted with comparatively larger value of torque. Experiment have been carried out on single rotor wind turbine and then dual rotor wind turbine after turbine development in the real atmospheric condition due to which different torque ,power produced, rotor speed was achieved which was analyzed and found fruitful where a large amount of power or torque is required

Analysis on the Force and Life of Gearbox in Double-Rotor Wind Turbine

In order to study the force and life of the key components in the gearbox of an existing double-rotor wind turbine, the design and structural parameters of the gearbox in the traditional National Renewable Energy Laboratory (NREL) 5 MW single-rotor wind turbine are adopted, and the fixed ring gear of the first planetary stage transmission is released to form a differential gearbox suitable for a double-rotor wind turbine with two inputs. The double input is used to connect the double rotor. Subsequently, the characteristics of the gearbox in a double-rotor wind turbine are discussed. On the basis of the constant rated power of the whole wind turbine, the total power is divided into two parts, which are allocated to the double rotors, then two rotational speeds of the two inputs are given according to different power ratios by complying with the matching principle of force and moment. Furthermore, the force acting on the pitch circle of the planet gear, as well as the force and life of the planet bearing of the two-stage planetary transmission are calculated and compared with a single-rotor wind turbine. The results show that the structural advantages of a double-rotor wind turbine can reduce the stress of key components of the gearbox and increase the life span of the planet bearing, thereby the life of the whole gearbox is improved and the downtime of the whole wind turbine is reduced.

The effect of axial distance on dual rotor wind turbine’s performance

Dual-rotor wind turbine (DRWT) is the development of wind turbine design with the addition of rotors placed on the same shaft. The addition of rotors causes the turbine to improve its performance. Experimental research was conducted to determine the performance that can be achieved by the DRWT type using the wind tunnel module. The test was carried out on three variations of the axial distance ratio of 0.08; 0.12; and 0.16. Comparing with a singlerotor wind turbine (SRWT), the DRWT type gives better performance. The DRWT type can rotate at a lower tip speed ratio than SRWT type. The power generated by the DRWT type is increasing up to 100% at tip speed ratio of 0.08 in all axial distance ratio while SRWT type can not rotate at tip speed ratio of 0.8. The DRWT type with a ratio of 0.12 is able to reach the highest coefficient of power which is 0.35 at tip speed ratio of 1.2. There was an increment of 53.7% in mechanical power from the SRWT type under the same conditions. Furthermore, the numerical method was used to know the flow phenomenon in the two rotors. The wake flow behind the first rotor causes backflow that give a loss to DRWT’s performance but still has enough energy that can be extracted by the second rotor and converted to mechanical power. Greater energy conversion will reduce wasted wind energy.

Multirotor wind turbine wakes

To fulfill the increasing need for large power generation by wind turbines, the concept of multirotor wind turbines has recently received attention as a promising alternative to conventional massive single-rotor wind turbines. To shed light on the viability of this concept, large-eddy simulation is employed in this study to compare wake flow properties of a multirotor wind turbine with those of a single-rotor turbine. The wake of a multirotor turbine is found to recover faster at short downwind distances, where the whole wake is characterized as an array of localized high velocity-deficit regions associated with each rotor. However, as the wake moves downstream, rotor wakes start interacting with each other until they eventually form a single wake. This transition from a wake array to a single wake adversely affects the initial fast recovery of multirotor turbine wakes. A budget analysis of mean kinetic energy is performed to analyze the energy transport into the wake before and after this transition. In addition, the effect of different geometrical configurations on wake characteristics of a multirotor turbine was examined. We found that the recovery rate of multirotor turbine wakes is enhanced by the increase in rotor spacing, whereas the number and rotation direction of rotors do not play a significant role in the wake recovery. A simple analytical relationship is also developed to predict the streamwise distance at which the transition from a wake array to a single wake occurs for multirotor wind turbines.

Improved energy production of multi-rotor wind farms

The multi-rotor (MR) wind turbine concept can be used to upscale wind turbines without increasing the rotor diameter, which can be beneficial for transport, manufacture and design of wind turbines blades. The rotor interaction of a MR wind turbine leads to a faster wake recovery compared to an equivalent single-rotor (SR) wind turbine wake. In this article, the benefit of the faster wake recovery of MR wind turbines is quantified using Reynolds-averaged Navier-Stokes simulations of a 4}4 rectangular MR wind farm, for three different inter wind turbine spacings. The simulations predict an increase of 0.3-1.7% in annual energy production for the MR wind farm with respect to an equivalent SR wind farm, where the highest gain is obtained for the tightest inter wind turbine spacing. The gain in AEP is mainly caused by the aligned wind directions for the first downstream wind turbine in a wind turbine row of the MR wind farm, which is verified by an additional large-eddy simulation.

The aerodynamic coupling design and wind tunnel test of contra-rotating wind turbines

The performance of contra-rotating wind turbines (CRWTs) is highly dependent on aerodynamic design. However, flow interaction between two rotors hasn't been fully understood. In this paper, flow interaction was considered in theoretical model based on actuator disc theory with wake rotation. As a consequence, a coupling design method was formulated. Simultaneous blade design of both rotors was originally expressed by a global optimization problem. The input variables include axial and tangential velocity induction factors of both rotors. The output is energy efficiency of CRWT at the annular disc. As a result, chord length and blade section pitch distribution were determined synchronously. This method was applied on the 500W cases of a CRWT and a single rotor wind turbine (SRWT) with identical radius. Wind tunnel test were carried out on the prototypes, with rotating speed and pitch of both rotors controlled independently under various wind velocity. Result validated the effectiveness of design method. At rated wind velocity, the maximum power coefficients of CRWT and SRWT were 0.426 and 0.373. Despite a slightly high start-up wind speed, CRWT demonstrated a higher power coefficient than single turbine at wind velocity 8–14 m/s, with power coefficient relative increment 5.3–28.9%.