Showing papers on "Blade pitch published in 2012"

A morphing trailing edge device for a wind turbine

Abstract: The loads on wind turbine components are primarily from the blades. It is important to control these loads in order to avoid damaging the wind turbine. Rotor control technology is currently limited to controlling the rotor speed and the blade pitch. As blades increase in length, it becomes less desirable to pitch the entire blade as a single rigid body, but there is a requirement to control loads more precisely along the length of the blade. This can be achieved with aerodynamic control devices such as flaps. Morphing structures are good candidates for wind turbine flaps because they have the potential to create structures that have the conflicting abilities of being load carrying, lightweight and shape adaptive. A morphing flap design with an anisotropic cellular structure is presented, which is able to undergo large deflections and high strains. An aeroelastic analysis couples the work done by aerodynamic loads on the flap, the flap strain energy and the required actuation work to change shape. The morphing flap model is manufactured, and its stiffness is measured.

Numerical simulation of wind turbine blade-tower interaction

Abstract: Numerical simulations of wind turbine blade-tower interaction by using the open source OpenFOAM tools coupled with arbitrary mesh interface (AMI) method were presented. The governing equations were the unsteady Reynolds-averaged Navier-Stokes (RANS) which were solved by the pimpleDyMFoam solver, and the AMI method was employed to handle mesh movements. The National Renewable Energy Laboratory (NREL) phase VI wind turbine in upwind configuration was selected for numerical tests with different incoming wind speeds (5, 10, 15, and 25 m/s) at a fixed blade pitch and constant rotational speed. Detailed numerical results of vortex structure, time histories of thrust, and pressure distribution on the blade and tower were presented. The findings show that the wind turbine tower has little effect on the whole aerodynamic performance of an upwind wind turbine, while the rotating rotor will induce an obvious cyclic drop in the front pressure of the tower. Also, strong interaction of blade tip vortices with separation from the tower was observed.

A review on recent low voltage ride-through solutions for PMSG wind turbine

Abstract: Research of grid connected wind turbines has gained great interest in the recent years. This led to introduce guidelines and regulations regarding the connection of large wind farms to the electrical network. One of such guidelines is low voltage ride-through capability (LVRT). In this paper, a survey on recent LVRT solutions for permanent magnet synchronous generators (PMSG) is carried out along with a brief explanation of grid codes. Among those solutions is the control of fully rated converters, blade pitch angle control and capacitor sizing. Other solutions such as active crowbar rotor circuit and the DC bus energy storage circuit are illustrated. The survey extends to provide possibilities for the development of further LVRT research at the wind farm level using high power FACT devices.

Combining droop curve concepts with control systems for wind turbine active power control

Abstract: Wind energy is becoming a larger portion of the global energy portfolio, and wind penetration has increased dramatically in certain regions of the world This increasing wind penetration has driven the need for wind turbines to provide active power control (APC) services to the local utility grid, as wind turbines do not intrinsically provide frequency regulation services that are common with traditional generators Large scale wind turbines are typically decoupled from the utility grid via power electronics, which allows the turbines to synthesize APC commands via control of the generator torque and blade pitch commands Consequently, the APC services provided by a wind turbine can be more flexible than those provided by conventional generators This paper focuses on the development and implementation of both static and dynamic droop curves to measure grid frequency and output delta power reference signals to a novel power set point tracking control system The combined droop curve and power tracking controller is simulated and comparisons are made between simulations using various droop curve parameters and stochastic wind conditions The tradeoffs involved with aggressive response to frequency events are analyzed At the turbine level, simulations are performed to analyze induced structural loads At the grid level, simulations test a wind plant's response to a dip in grid frequency

Optimum seeking-based non-linear controller to maximise energy capture in a variable speed wind turbine

Abstract: In this study, an optimum seeking-based robust non-linear controller is proposed to maximise wind energy captured by variable speed wind turbines at low-to-medium wind speeds The proposed strategy simultaneously controls the blade pitch angle and tip-speed ratio, through the turbine rotor angular speed, to an optimal point at which the power coefficient, and hence the wind turbine efficiency, is maximum The optimal points are given to the controller by an optimisation algorithm that seeks the unknown optimal blade pitch angle and rotor speed The control method allows for aerodynamic rotor power maximisation without exact knowledge of the wind turbine model A representative numerical simulation is presented to show that the wind turbine can be accurately controlled to achieve maximum energy capture

Model prediction control method and model prediction control system for all working conditions of wind generating set

Abstract: Disclosed are a model prediction control method and a model prediction control system for all working conditions of a wind generating set. The system comprises an MPC (model prediction control) device, a feedback information measurer, a wind wheel, a driving chain, a tower, a generating unit, a variable propeller driver and a converter. The feedback information measurer is used for detecting status variables of the wind wheel, the driving chain, the tower and the generating unit and transmitting detecting results to the MPC device, the MPC device is used for computing targets of the blade pitch angle and the generator torque, and the variable propeller driver and the converter are used for adjusting the blade pitch angle and the wind generator torque. The method is used for computing control increment by means of a variable propeller control prediction model and a torque control prediction model, takes the status variables including driving chain torsional displacement, driving chain torsional speed, blade plane external first-order flap displacement, blade plane external first-order flap speed, tower front-back first-order swing displacement, tower front-back first-order swing speed, mechanical loads of the unit and the like, and two prediction models can be automatically switched in different working conditions, so that the wind generating set can be operated in all working conditions.

Electrical powered tail rotor of a helicopter

Abstract: The invention is related to an electrical powered tail rotor (1) of a helicopter comprising a housing (2) around the tail rotor (1), and at least one permanent magnet energized synchronous motor with a stator (6, 7) with an increased number of poles (9). Said at least one synchronous motor is integrated as a torus (8) around an opening of the housing (2) encompassing the tail rotor (1). Blades (4) of the tail rotor (1) are fixed to at least one rotating component (10, 11) of said at least one synchronous motor. Supply means provide for electric energy to said at least one synchronous motor. Blade pitch control means are provided at the torus (8).

Comparison of feedforward and model predictive control of wind turbines using LIDAR

Abstract: LIDAR systems are able to provide preview information of wind disturbances at various distances in front of wind turbines. This technology paves the way for new control concepts such as feedforward control and model predictive control. This paper compares a nonlinear model predictive controller and a feedforward controller to a baseline controller. Realistic wind “measurements” are obtained using a detailed simulation of a LIDAR system. A full lifetime comparison shows the advantages of using the wind predictions to reduce wind turbine fatigue loads on the tower and blades as well as to limit the blade pitch rates. The results illustrate that the feedforward controller can be combined with a tower feedback controller to yield similar load reductions as the model predictive controller.

Modeling, simulation and control of a wind turbine with a hydraulic transmission system

Abstract: A complete mathematical model of a hydraulic transmission concept for use in wind turbines is presented. The hydraulic system transfers the power from the nacelle to ground level. The main focus has been to develop a model that takes into account the most important dynamics affecting the wind turbine and the hydraulic transmission system involved, such that the model can be used to analyze the dynamic feasibility of a hydraulic transmission concept. Further, dynamic analysis of a hydraulic transmission system for wind turbines is investigated. The nonlinear dynamic model is developed in MATLAB Simulink. Analytical calculation of natural periods of a linearized model corresponds well with simulations of the overall system. A valve control system is proposed to reduce pressure and power fluctuations at operation both below and above the rated wind speed for the wind turbine. Further, a blade pitch control system based on an aerodynamic power estimator is proposed for operation above the rated wind speed. System simulations for one case below and one case above the rated wind speed show that the dynamic response of the overall system is stable and that the wind turbine variables are within typical ranges for conventional variable speed wind turbines with mechanical transmission. Copyright © 2012 John Wiley & Sons, Ltd.

Design and Test of a Vertical-Axis Wind Turbine with Pitch Control

Abstract: The concept of pitch control has been implemented in the design of a small vertical-axis wind turbine. Benefits gained can be shown by the experimental and numerical results presented in this paper. As found, the method of variable pitch control outperforms the one of fixed pitch control. The present results show that the former can make remarkable improvement on the starting torque as well as the aerodynamic characteristics at low tip speed ratios.

Power Regulation of Variable Speed Wind Turbines using Pitch Control based on Disturbance Observer

Abstract: Most variable speed wind turbines have pitch control mechanisms and one of their objectives is to protect turbines when the wind speed is too high. By adjusting pitch angles of wind turbine, the inlet power and the torque developed by the turbine are regulated. In this paper, the difference between the real wind speed and its rated value is regarded as a disturbance, and a component called disturbance observer (DOB) is added to the pre-designed control loop. The additional DOB based controller estimates the disturbance and generates a compensating signal to suppress the effect of disturbance on the system. As a result, the stability and the performance of the closed loop system guaranteed by an outer-loop controller (designed for a nominal system without taking into account of disturbances) are approximately recovered in the steady state. Simulation results are presented to verify the performance of the proposed control scheme.

Load shape control of wind turbines

Abstract: Methods and apparatus for control and monitoring of wind turbines. Various embodiments pertain to the operational analysis of vibratory modes of the blades of the wind turbine. This real time analysis of blade modal response can be used as feedback in a control system to change the yaw angle of the hub and nacelle to capture higher power from the wind stream, change the pitch on one or more blades to reduce uneven blade loading, to identify damage to a blade, and further to identify the accumulation of ice on a blade.

Partial-load de-rating for wind turbine control

Abstract: Methods,controllers and computer program products for controlling a wind turbine. Under de-rated operating conditions in which the power requested from a wind turbine is less than the available power, a controller adjusts blade pitch of the wind turbine to reduce the rotor power coefficient. The captured wind power is thereby reduced to be approximately equal to the requested electrical power, which is less than either the available power or the rated power of the wind turbine generator. This reduction in captured power provides the controller with an additional degree of freedom that allows the controller to increase the electrical power output of the wind turbine in response to wind fluctuations without damaging the wind turbine. By allowing increases in power under de-rated conditions, the controller may reduce the amount of pitching necessary to prevent the turbine from exceeding its rated power output level.

Implementation of Pitch Control Of wind Turbine Using Simulink (Matlab)

Abstract:  Abstract— In this paper, it is shown that how the variable speed wind turbine can be used to generate a fixed value of voltage at the output with the help of a pi controller and it is done by varying the pitch angle of the blades Pitch angle control is the most common means for adjusting the aerodynamic torque of the wind turbine when wind speed is above rated speed and various controlling variables may be chosen, such as wind speed, generator speed and generator power As conventional pitch control usually use PI controller, the mathematical model of the system should be known well The block diagram of the proposed speed control system which consists of speed controller, actuator model and the turbine linearized model is simulated by Matlab-Simulink software package the simulation results show that the controller accurately adjusts the blade pitch angle to set the wind turbine power output to its reference value A rotor swept area Cp aerodynamic coefficient of performance air density angle of attack pitch angle of the blade tip-speed ratio rotor-speed

Growing Neural Gas-Based MPPT of Variable Pitch Wind Generators With Induction Machines

Abstract: This paper proposes a maximum power point tracking (MPPT) technique for variable pitch wind generators with induction machines, which can suitably be adopted in both the maximum power range and the constant power range of the wind speed. For this purpose, an MPPT technique based on the growing neural gas (GNG) wind turbine surface identification and the corresponding function inversion has been adopted to cover also the situation of constant rated power region. This has been obtained by including the blade pitch angle in the space of the data learnt by the GNG and feeding back the estimated wind speed to compute the correct value of the pitch angle, which permits the machine to work at rated power and torque. A further enhancement of the pitch angle selection by a simple perturb & observe method has been added to cope with slight wind estimation errors occurring at machine rated speed. The proposed methodology has been verified both in numerical simulation and experimentally on a properly devised test setup. The correct behavior of the system has been proved also on a real wind speed profile on a daily scale.

Voltage/pitch control for maximisation and regulation of active/reactive powers in wind turbines with uncertainties

Abstract: This study addresses the problem of controlling a variable-speed wind turbine with a doubly fed induction generator (DFIG), modelled as an electromechanically coupled non-linear system with rotor voltages and blade pitch angle as its inputs, active and reactive powers as its outputs, and most of the aerodynamic and mechanical parameters as its uncertainties. Using a blend of linear and non-linear control strategies (including feedback linearisation, pole placement, uncertainty estimation and gradient-based potential function minimisation) as well as time-scale separation in the dynamics, the authors develop a controller that is capable of maximising the active power in the maximum power tracking (MPT) mode, regulating the active power in the power regulation (PR) mode, seamlessly switching between the two modes and simultaneously adjusting the reactive power to achieve a desired power factor. The controller consists of four cascaded components, uses realistic feedback signals, and operates without knowledge of the C p -surface, air density, friction coefficient, and wind speed. Finally, the authors show the effectiveness of the controller via simulation with realistic wind profiles.

Robust nonlinear control strategy to maximize energy capture in a variable speed wind turbine with an internal induction generator

Abstract: This paper proposes a control strategy to maximize the wind energy captured in a variable speed wind turbine, with an internal induction generator, at low to medium wind speeds. The proposed strategy controls the tip-speed ratio, via the rotor angular speed, to an optimum point at which the efficiency constant (or power coefficient) is maximum for a particular blade pitch angle and wind speed. This control method allows for aerodynamic rotor power maximization without exact wind turbine model knowledge. Representative numerical results demonstrate that the wind turbine can be controlled to achieve near maximum energy capture.

Methods and systems for alleviating the loads generated in wind turbines by wind asymmetries

Abstract: A method for alleviating rotor asymmetric loads in a variable-speed wind turbine having pitch and torque control means comprising the following steps: providing a control law that determines the pitch to be applied individually to each wind turbine blade for counteracting rotor asymmetric loads (such as wind shear, upflow, yaw misalignment) using wind speed and wind direction measurements at the wind turbine, values of the wind features that cause rotor asymmetric loads and configuration parameters of the wind turbine (whether real-time values or statistical values at the wind turbine site), said pitch to be added to the collective pitch θ 0 ; implementing said control law in the wind turbine control means. The invention also refers to a wind turbine control system arranged for implementing said method.

Wind speed estimation for wind turbine control

Abstract: In the literature, proposed control strategies for the efficiency of wind energy conversion systems are usually based on gain scheduling PI controller using the pitch angle to control the rotor speed. Focus is then only made on power production. In previous work, we proposed a model based control strategy that highly decreases the mechanical solicitation of the structure while preserving power production. This control strategy is based on aerodynamical models that uses the measure of the wind speed as an input.

Numerical calculations of propeller shaft loads on azimuth propulsors in oblique inflow

Abstract: This paper evaluates various computational methods used to compute propeller performance, hydrodynamic side force and bending moment applied to an azimuth propulsor propeller shaft in oblique inflow. The two non-viscous models used are the BEM method and the blade element momentum theory (BEMT). RANS calculations are used to compute the loads on the propeller and the nominal wake velocity from the thruster body to be used in the BEMT model. The effect of the ship hull is also considered in the calculation by implementing the measured nominal wake of a ship hull at different propeller azimuthal positions. All the models are compared and validated against the experimental results, and the discussions are presented.

Blade Design Optimisation for Fixed-Pitch Fixed-Speed Wind Turbines

Abstract: Fixed-pitch fixed-speed (FPFS) wind turbines have some distinct advantages over other topologies for small wind turbines, particularly for low wind speed sites. The blade design of FPFS wind turbines is fundamentally different to fixed-pitch variable-speed wind turbine blade design. Theoretically, it is difficult to obtain a global mathematical solution for the blade design optimisation. Through case studies of a given baseline wind turbine and its blade airfoil, this paper aims to demonstrate a practical method for optimum blade design of FPFS small wind turbines. The optimum blade design is based on the aerodynamic characteristics of the airfoil, that is, the lift and drag coefficients, and the annual mean wind speed. The design parameters for the blade optimisation include design wind speed, design tip speed ratio, and design attack angle. A series of design case studies using various design parameters are investigated for the wind turbine blade design. The design outcomes are analyzed and compared to each other against power performance of the rotor and annual energy production. The design outcomes from the limited design cases demonstrate clearly which blade design provides the best performance. This approach can be used for any practice of FPFS wind turbine blade design and refurbishment.

Two LQRI based Blade Pitch Controls for Wind Turbines

Abstract: As the wind turbine size has been increasing and their mechanical components are built lighter, the reduction of the structural loads becomes a very important task of wind turbine control in addition to maximum wind power capture. In this paper, we present a separate set of collective and individual pitch control algorithms. Both pitch control algorithms use the LQR control technique with integral action (LQRI), and utilize Kalman filters to estimate system states and wind speed. Compared to previous works in this area, our pitch control algorithms can control rotor speed and blade bending moments at the same time to improve the trade-off between rotor speed regulation and load reduction, while both collective and individual pitch controls can be designed separately. Simulation results show that the proposed collective and individual pitch controllers achieve very good rotor speed regulation and significant reduction of blade bending moments.

Blade Displacement Measurement Technique Applied to a Full-Scale Rotor Test

Abstract: Blade displacement measurements using multi-camera photogrammetry were acquired during the full-scale wind tunnel test of the UH-60A Airloads rotor, conducted in the National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel. The objectives were to measure the blade displacement and deformation of the four rotor blades as they rotated through the entire rotor azimuth. These measurements are expected to provide a unique dataset to aid in the development and validation of rotorcraft prediction techniques. They are used to resolve the blade shape and position, including pitch, flap, lag and elastic deformation. Photogrammetric data encompass advance ratios from 0.15 to slowed rotor simulations of 1.0, thrust coefficient to rotor solidity ratios from 0.01 to 0.13, and rotor shaft angles from -10.0 to 8.0 degrees. An overview of the blade displacement measurement methodology and system development, descriptions of image processing, uncertainty considerations, preliminary results covering static and moderate advance ratio test conditions and future considerations are presented. Comparisons of experimental and computational results for a moderate advance ratio forward flight condition show good trend agreements, but also indicate significant mean discrepancies in lag and elastic twist. Blade displacement pitch measurements agree well with both the wind tunnel commanded and measured values.