Dynamic Model Of Wind Turbine Research Articles

Dynamic reliability estimation of onshore wind turbine tower based on frequency-domain method

With the upscaling of wind turbine, the issue of dynamic reliability of wind turbine towers has become increasingly evident. However, the complexity and nonlinearity of wind turbine dynamics present significant challenges in evaluating their dynamic reliability under stochastic loads, requiring substantial computational resources. In this paper, a computationally cost-effective frequency-domain method is proposed as a means of estimating the dynamic reliability of an onshore wind turbine tower. An analytical approach is employed to obtain the power spectral density (PSD) of the rated wind speed and load on the rotating blades. Secondly, a dynamic model of onshore horizontal axis onshore wind turbine is established using flexible multi-body dynamics (MBD). The linear time-varying dynamic equation is transformed into a linear time-invariant form through the application of statistical linearization method. Subsequently, complex modal analysis is used to employ the displacements and internal forces of the tower. Moreover, the first-passage reliability and fatigue reliability of the wind turbine tower are determined through power spectral analysis. A numerical example of a 5-MW wind turbine is presented to demonstrate that the proposed method yields results in good agreement with Monte Carlo simulations (MCS), thereby demonstrating its effectiveness. The reliability analysis of the 5-MW wind turbine reveals that over a 20-year design life, the first-passage reliability is 0.9997 when adopting fore-after displacement at the tower top as the failure criterion, and the fatigue reliability of the tower base is 0.9445.

Hierarchical dynamic wake modeling of wind turbine based on physics-informed generative deep learning

With the increasing demand for electric power, the size of wind farms is becoming much larger than ever before. Power and load prediction are two of the most essential topics in wind farm layout optimization. Traditional wake modeling methods, such as analytic models and CFD simulations, struggle to handle such large-scale problems accurately and efficiently. In this study, a novel hierarchical dynamic wake modeling approach for wind turbines using generative deep learning, PHOENIX (PHysics-infOrmed gEnerative deep learniNg for hIerarchical dynamic wake modeling eXploration), is proposed to capture the spatial–temporal features of the unsteady wake field in wind turbine clusters. The dynamic wake meandering (DWM) model is employed to generate the corresponding datasets for training, testing, and validating the deep learning-based wake prediction framework. This research is expected to accelerate the prediction process and improve accuracy, and it can be further applied to wind turbine design and wind farm layout optimization.

Dynamic modeling and vibration control of barge offshore wind turbine using tuned liquid column damper in floating platform

This study investigated the vibration suppression of a barge-type floating offshore wind turbine (FOWT) using a passive tuned liquid damper (TLCD) in the floating platform. The fully coupled aero-hydro–servo-elastic model was established using OpenFAST, and it was used to evaluate the suppression performance of the TLCD in the time and frequency domains. To optimally design the TLCD parameters, a 3-degree of freedom (DOF) model was proposed based on the Lagrange equation for a barge-type FOWT with a platform TLCD, which accounts for the DOF of platform pitching, tower bending in the fore–aft direction, and vertical-liquid column motion of TLCD. The unknown parameters of the 3-DOF model were estimated and validated to ensure result accuracy. The exhaustive search method was implemented to obtain the optimized TLCD parameters of the barge-type FOWT, and the simulation results showed that TLCD can effectively mitigate the structural vibration of barge-type FOWT. When applying a large TLCD mass to the barge platform for structural vibration control, replacing part of the ballast with a TLCD of equal mass to maintain the overall mass of the barge-type FOWT was prioritized.

An Uncertainty-Aware Health Monitoring Model for Wind Turbine Drivetrains Based On Bayesian Neural Network

Vibration-based fault diagnostics in rotating machinery when combined with deep learning approaches have yielded promising results. Nevertheless, standard deep learning methods can be unreliable when faced with new data from previously unseen faults or unusual operating conditions. To overcome this challenge, a Bayesian convolutional neural network is explored in this study to diagnose faults in wind turbine gearboxes. This Bayesian statistics framework provides accurate results with low uncertainty by evaluating test data with the same training data distribution. When presented with data that it has not seen before, the network signals its uncertainty and recommends human intervention. This helps to reduce the likelihood of incorrect diagnoses resulting from wrong overconfident classifications. The study compares the performance of Bayesian and standard neural networks using a simulation-based database of acceleration signals. These signals are represented as 2D cyclic spectral coherence maps generated from a multi-body dynamic model of a five-Megawatt wind turbine. By incorporating uncertainty into the prediction results, this approach has the potential to significantly reduce false positives and improve maintenance operations’ efficiency and effectiveness.

Investigation of Wind Data Resolution for Small Wind Turbine Performance Study


 Small wind turbine sites, in general, use a 0.5Hz sampling interval and a 10-minute averaging interval for a feasibility study or turbine testing. Studies have established that the calculated performance variation of small wind turbines when averaging at large time intervals. The performance variation is larger for sites with high wind variability. However, these studies are often based on low sampling frequency and high averaging intervals. 
 
 
 In the present study, wind speed data has been measured at a high sampling frequency of 20Hz with an ultrasonic sensor. A dynamic model of a 50W Rutland wind turbine is used to analyse the simulated performance using wind speed data at a range of sampling intervals and some averaging intervals. The wind turbine and the anemometer are installed in a residential area of high wind variability. 
 
 
 The energy is calculated and compared directly using the wind turbine model and using the IEC recommended method of bins. The direct method results show that the rise in instantaneous sampling intervals up to 20 seconds has an insignificant effect on the energy output. Whereas, for 2-seconds sampled wind data averaged over 10-minutes, energy overestimates of 19% is observed. However, where only 10-minute interval averaged wind data are available, there is a significant underestimate in energy by 45%. The energy calculated using the method of bins overestimates the energy by 19% for high resolution wind data and underestimates by 22% for 10-minute average data.

Dynamic Modeling and Investigation of a Tunable Vortex Bladeless Wind Turbine

This paper investigates the dynamics of an electromagnetic vortex bladeless wind turbine (VBWT) with a tunable mechanism. The tunable mechanism comprises a progressive-rate spring that is attached to an oscillating magnet inside an electromagnetic coil. The spring stiffness is progressively adjusted as the wind speed changes to tune the turbine fundamental frequency to match the shedding frequency of the vortex-induced vibration (VIV) due to the wind flow crossing over the oscillating mast. Coupled nonlinear equations of motion of the tunable turbine are developed using the lumped-mass representation and Lagrange formulation. Numerical results show that the tunable turbine performs effectively beyond a threshold wind speed. An analytical expression of the threshold speed is derived based on the mechanical fundamental frequency of the turbine. The analytical results are in reasonable agreement with the numerical evaluations. At a given wind speed past the threshold, the tunable turbine has an optimum spring stiffness at which the output power is maximum. Numerical studies also show that the output power of the 2 m long tunable turbine is tens of times larger in comparison to a conventional bladeless turbine. For example, at a wind speed of 4.22 m/s, the output rms power of the tunable turbine is around 1105 mW versus 17 mW of the conventional VBWT. The power can be further maximized at an optimum external load. This research work demonstrated the feasibility and merits of the proposed tunable mechanism to enhance the overall performance of the bladeless wind turbine.

Dynamic modeling of power network-integrated wind turbine

This paper presents the performance investigation of voltage and current for dynamic model of the wind turbine. In this study, the various numbers of wind turbine speed are applied in the simulation. This treatment is intended to see how much influence the turbine speed has on the voltage and current output. IEEE 14 bus system is integrated to the wind turbine in order to observe the impact of on-grid connection to the voltage and current performance. How to model wind turbine in PSCAD simulation software also discussed in this paper. The detail of supporting components in designing a wind turbine system and their functions are also explained. Several values of turbine speed are also considered in this paper as a study material in seeing the performance of wind turbines. The relationship between wind speed and pitch angle will also be discussed to ensure that the wind turbine is not damaged. In order to prove the accuracy of the simulation model, the obtained measurement generation of active power from the wind turbine is matched with the manual calculation. Based on the various wind speed values that have been tested, this can be the basis for the application of wind turbine (renewable energy) design development for further research.

Nonlinear dynamic characteristics of horizontal-axis wind turbine blades including pre-twist

This paper focuses on the dynamic modeling and vibration analysis of horizontal axis wind turbine (HAWT) blades with emphasis on the effects of the pre-twist, rotational rigid body motion and coupling among the different blade's degrees of freedom. The blade is considered as a rotating pre-twisted beam mounted on a rigid hub with a constant angle relative to the plane of rotation, so-called precone angle. Kinetic energy of the blade based on its elastic as well as rigid motion together with its strain energy and generalized forces resulting from gravitational, centrifugal and aerodynamic loadings are obtained and used to derive new coupled dynamic equations by means of Hamilton's principle. The weak formulation is constructed and the Rayleigh-Ritz method (RRM) is adopted to extract a reduced order model (ROM) for the blade's vibration analysis. The developed nonlinear ROM is linearized around the steady-state solution and the blade's dynamic characteristics are obtained. The reference wind turbine blade called NREL 5-MW HAWT blade is selected as the case-study and effects of pre-twist, centrifugal force, angular velocity-depended terms, nonlinearities and transverse static loads on its dynamic characteristics are investigated. Results are shown to be in good agreement with available data in the literature.

A Combined RMS Simulation Model for DFIG-Based and FSC-Based Wind Turbines and Its Initialization

Reconstructable dynamic simulation models of modern variable-speed wind turbines (WTs), which are integrable into any simulation software, are crucial to the scientists investigating the contribution of WTs to counteracting the current power system stability issues. The structural similarity between a doubly fed induction-generator-based (DFIG-based) WT model and a full-scale-convertor-based (FSC-based) WT model using induction generator offers the possibility of integrating them into a combined modular model with little effort and the same used parameter set. This article presents a combined root mean square (RMS) WT model, which contains a DFIG-based WT and a FSC-based WT using induction generator. The model is designed based on fundamental machine and converter equations and can be applied for classical network stability analyses. Furthermore, analogous well-performing initialization procedures for both DFIG-based and FSC-based WT models are also introduced. As an example, to demonstrate the performance of the WT model in frequency stability studies, the model is extended with a droop-based fast frequency response (FFR) controller and is implemented in a MATLAB-based RMS simulation tool. The results of the case studies confirmed a solid functionality of initialization procedures. Furthermore, they illustrate feasible and comparable general behavior of both WT models as well as their plausible responses in the event of a frequency drop in a 220 kV test system.

A comparative study of fully coupled and de-coupled methods on dynamic behaviour of floating wind turbine drivetrains

Traditionally, drivetrain responses are obtained by a de-coupled analysis, which first involves a global analysis with a simplified representation of the drivetrain, followed by a detailed analysis of the drivetrain with the input of global response on the drivetrain interface. As the wind turbine size increases, it is questionable whether this de-coupled analysis method yields sufficiently accurate results. To address this question, a comparative study of the drivetrain dynamic behaviour obtained by a fully coupled method and a de-coupled one, is conducted and reported in this paper. A 10-MW fully coupled aero-hydro-servo-elastic floating wind turbine dynamic model is developed, including a high-fidelity drivetrain. The developed fully coupled model is assessed to be reasonable via the comparison of drivetrain first-order natural frequency and code-to-code comparisons in terms of global responses between two simulation tools Simpack and Fast. Resonance analysis of the 10-MW drivetrain in the fully coupled model is performed, with focus on rotor-drivetrain-bedplate-tower coupled modes in the low frequency range. Time domain simulations of the drivetrain in the fully coupled and the de-coupled models are carried out in different environmental conditions. One-hour fatigue damage of drivetrain gears and bearings in the fully coupled and de-coupled models are compared. Effect of nacelle motion on drivetrain fatigue damage in the de-coupled analysis is discussed. The results are presented to demonstrate whether the de-coupled method could be confidently used for drivetrain dynamic analysis. This study provides a basis for drivetrain design and dynamic analysis in floating wind turbines.

Extensive model validation for generic IEC 61400-27-1 wind turbine models

The aim of this paper is to demonstrate the usefulness, practical applicability, accuracy and reliability of Standard IEC 61400-27-1. The objective of this standard is to specify generic simulation models for the four main types of wind turbines, as well as procedures to validate them. Given that most of the works published and related to the validation of generic wind turbine models have applied a limited number of voltage dip tests to a single wind turbine, the present paper significantly widens the scope of these studies, conducting a total of 59 voltage dip field tests in 7 different wind turbines from 3 manufacturers. The Type 3 and Type 4 wind turbines, i.e., the doubly-fed and the full-scale converter wind turbines, respectively, are the two topologies analysed, since these comprise the vast majority of the market share for new wind turbines. The field measurements carried out on the actual wind turbines are compared to the simulation results of the corresponding IEC dynamic wind turbine models, and the IEC validation methodology is applied. Based on the results obtained, several comparative analyses are performed, and the reasons for differences in the accuracy of the behaviour of the wind turbine topologies considered are also analysed.

A novel approach for robust control design of hidden synthetic inertia for variable speed wind turbines

This work presents a novel design methodology for hidden synthetic inertia control of variable speed wind turbines that considers the compromise between grid frequency response and operating limits of the wind turbine states. Two state space design strategies are proposed: one based on H∞ robust control with dynamic output feedback; and other based on H∞ static state feedback control; both strategies operate as supplementary controllers. The study was carried out on simulation with dynamic mathematical modeling of a variable speed wind turbine and an isolated system with conventional power plants, aiming to evaluate the grid frequency response to load-generation disturbances and wind speed variations. The proposed control strategies are compared with two topologies: without wind turbine frequency control and another with synthetic inertia contribution by Proportional-Derivative control. The proposed strategies allow to optimize performance of synthetic inertia control in accordance with wind turbine operating limits. H∞-based topologies presented greater attenuation of the impacts of load-generation disturbances on the frequency response, and also minimizes a cost function based on H2 norm of the frequency signal in comparison with other controllers, thus providing better performance against reference variations and changes of operation point.

A novel wind turbine fault diagnosis method based on generator current analysis

Gear meshing dynamic model is the most important part in the whole wind turbine system which is used to carry out operation conditions simulation in off-line case. By simulating the normal gear meshing and the gear meshing with broken teeth in wind turbine dynamic model respectively, the difference in generator current can be observed. The method we propose is to monitor the operating condition of the wind turbine based on the current transmitted to the generator end dynamically according to the meshing of the gear pair. Mechanical parameters have great influence on the system that will be transmitted to asynchronous generator, it works in a quite different approach compared with traditional method on vibration monitoring using sensors.

Prediction and Validation of the Annual Energy Production of a Wind Turbine Using WindSim and a Dynamic Wind Turbine Model

In this study, dynamic simulations of a wind turbine were performed to predict its dynamic performance, and the results were experimentally validated. The dynamic simulation received time-domain wind speed and direction data and predicted the power output by applying control algorithms. The target wind turbine for the simulation was a 2 MW wind turbine installed in an onshore wind farm. The wind speed and direction data for the simulation were obtained from WindSim, which is a commercial computational fluid dynamics (CFD) code for wind farm design, and measured wind speed and direction data with a mast were used for WindSim. For the simulation, the wind turbine controller was tuned to match the power curve of the target wind turbine. The dynamic simulation was performed for a period of one year, and the results were compared with the results from WindSim and the measurement. It was found from the comparison that the annual energy production (AEP) of a wind turbine can be accurately predicted using a dynamic wind turbine model with a controller that takes into account both power regulations and yaw actions with wind speed and direction data obtained from WindSim.

Requirements for Validation of Dynamic Wind Turbine Models: An International Grid Code Review

Wind power is positioned as one of the fastest-growing energy sources today, while also being a mature technology with a strong capacity for creating employment and guaranteeing environmental sustainability. However, the stochastic nature of wind may affect the integration of power plants into power systems and the availability of generation capacity. In this sense, as in the case of conventional power plants, wind power installations should be able to help maintain power system stability and reliability. To help achieve this objective, a significant number of countries have developed so-called grid interconnection agreements. These are designed to define the technical and behavioral requirements that wind power installations, as well as other power plants, must comply with when seeking connection to the national network. These documents also detail the tasks that should be conducted to certify such installations, so these can be commercially exploited. These certification processes allow countries to assess wind turbine and wind power plant simulation models. These models can then be used to estimate and simulate wind power performance under a variety of scenarios. Within this framework, and with a particular focus on the new Spanish grid code, the present paper addresses the validation process of dynamic wind turbine models followed in three countries—Spain, Germany and South Africa. In these three countries, and as a novel option, it has been proposed that these models form part of the commissioning and certification processes of wind power plants.

Simple vibration model for the design of a vertical axis wind turbine

Wind turbines are widely used these days as one of renewable energy sources. In this paper, a dynamic model of a vertical axis wind turbine is developed by considering coupling effects among shaft bending, shaft torsion, shaft tension, rotor tension and rotor bending. The modal characteristics of the vertical axis wind turbine were obtained by using the dynamic model. The accuracy of the proposed model was first validated by comparing its numerical results to those obtained with a commercial program. Then, the effects of key design parameters such as shaft length, shaft diameter and rotor cross section area on the modal characteristics of the wind turbine were investigated. The natural frequency loci veering phenomena occurred when those parameters varied. The loci veering phenomena were associated with the mode shape switch between shaft bending and rotor bending, which should be carefully examined to improve the vibration quality of the wind turbine. The main contribution of this study is to propose a simple vibration model by which the effects of various design parameters on the modal characteristics of the vertical axis wind turbine can be investigated. Some design guidelines related to the vibration performance are also suggested.

Dynamic modeling and free vibration analysis of horizontal axis wind turbine blades in the flap-wise direction

The dynamic modeling and free vibration analysis of horizontal axis wind turbine (HAWT) blades in the flap-wise direction are addressed in this paper. Blade kinetic and potential energy are evaluated while taking into account the influences of gravity force, centrifugal force, and the blade rotary inertia. Using Hamilton's principle, a nonlinear partial differential equation with time and space varying coefficients together with appropriate boundary conditions is derived as a novel and comprehensive dynamic model for the blade vibration in the flap-wise direction. After linearizing and simplifying the nonlinear model, the Rayleigh-Ritz method is employed to find natural frequencies and their associated mode shapes. Furthermore, the National Renewable Energy Laboratory (NREL) 5-MW reference wind turbine is chosen to investigate the effects of the rotary inertia, angular velocity, hub radius, pitch and precone angles on its dynamic characteristics. It is shown that increasing the hub radius and the angular velocity or decreasing the rotary inertia, significantly increases the natural frequencies while design parameters such as pitch or precone angles slightly affect the dynamic characteristics of the blades. The accuracy of the simplified model is also verified by comparing results for natural frequencies with some existing data in the literature.

Study of Dynamic Response Characteristics of the Wind Turbine Based on Measured Power Spectrum in the Eyewall Region of Typhoons

The present research envisages a method for calculating the dynamic responses of the wind turbines under typhoon. The measured power spectrum and inverse Fourier transform are used to generate the fluctuating wind field in the eyewall of the typhoon. Based on the beam theory, the unsteady aerodynamic model and the wind turbine dynamic model are coupled to calculate the dynamic response. Furthermore, using this method, the aeroelastic responses of a 6 MW wind turbine at different yaw angles are studied, and a 2 MW wind turbine are also calculated to verify the applicability of the results for different sizes of wind turbines. The results show that the turbulence characteristics of the fluctuating wind simulated by the proposed method is in good agreement with the actual measurement. Compared with the results simulated by the recommended power spectrum like the Kaimal spectrum, the energy distribution and variation characteristics simulated by the proposed method represent the real typhoon in a superior manner. It is found that the blade vibrates most violently at the inflow yaw angle of 30 degrees under the coupled effect of the aerodynamic, inertial and structural loads. In addition, the load on the tower exceeds the design limit values at the yaw angles of both 30 degrees and 120 degrees.

A dynamic programming-based maintenance model of offshore wind turbine considering logistic delay and weather condition

There are several challenges toward maintaining offshore wind turbines such as ensuring the intrinsic performance of the wind turbine, maximizing short- and long-term profits, and optimizing maintenance grouping. These criteria should be optimized in respect to several practical constraints. Moreover, issues such as decision-making in uncertain environments where reliability-oriented field data are insufficient and information regarding the state of health state also be tackled.This paper proposes a failure model that includes multiple failure modes with different failure consequences. Logistic delays and weather conditions are also obstacles for performing maintenance activities. To save logistic cost and downtime loss, a two-level maintenance policy considering both periodic maintenance planning and reactive maintenance is developed. The first level is aimed at failure modes whose degradation process is black-box by grouping individual maintenance activities according to their own maintenance period. The second level is aimed at those failure modes whose failure can be indicated through two options: 1) Integration with existing maintenance tasks of the first level and 2) creating a new maintenance opportunity. The effects of decision thresholds on the choice of maintenance options are studied through simulations.

Improving the reliability and energy production of large wind turbine with a digital hydrostatic drivetrain

Gearbox failure is one of the major factors causing the increased downtime in modern wind turbines. This increases the turbine maintenance cost and therefore the turbine cost of energy. A hydrostatic transmission not only improves the turbine reliability through its “soft” transmission, but also eliminates the use of power converter through its continuous variable transmission function. A hydrostatic wind turbine usually employs a fixed displacement pump to drive a variable displacement motor. The variable displacement motor runs at partial displacement when the wind speed is below the rated wind speed, leading to low drivetrain efficiency. Moreover, large variable displacement motors for large utility wind turbine are not commercially available. Therefore in this paper a digital hydrostatic transmission solution for large utility wind turbine has been proposed. The large variable displacement motor was replaced by combining several fixed displacement motors and a small variable displacement motor with some digital encoding scheme. Two encoding schemes have been proposed for digital hydrostatic transmission. The modeling and design of the digital hydrostatic wind turbine were presented. A hydrostatic wind turbine control based on kw2 control law has been proposed. A dynamic simulation model of the digital hydrostatic wind turbine has been developed. The proposed digital hydrostatic drive solution has been compared with a conventional hydrostatic solution in a commercial 2.5 MW wind turbine. Simulation studies verified the feasibility and the engineering practice of the proposed digital hydrostatic drive solution.