Showing papers on "Blade pitch published in 2008"

Pitch angle control for variable speed wind turbines

Abstract: 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. A fuzzy logic pitch angle controller is developed in this paper, in which it does not need well known about the system and the mean wind speed is used to compensate the non-linear sensitivity. The fuzzy logic control strategy may have the potential when the system contains strong non-linearity, such as wind turbulence is strong, or the control objectives include fatigue loads. The design of the fuzzy logic controller and the comparisons with conversional pitch angle control strategies with various controlling variables are carried out. The simulation shows that the fuzzy logic controller can achieve better control performances than conventional pitch angle control strategies, namely lower fatigue loads, lower power peak and lower torque peak.

Influence of Control on the Pitch Damping of a Floating Wind Turbine

Abstract: This paper presents the influence of conventional wind turbine blade-pitch control actions on the pitch damping of a wind turbine supported by an offshore floating barge with catenary moorings.

On the proof of concept of a ‘Smart’ wind turbine rotor blade for load alleviation

Abstract: The trend with offshore wind turbines is to increase the rotor diameter as much as possible to decrease the costs per kilowatt-hour. The increasing dimensions have led to the relative increase of the loads on the wind turbine structure. Because of the increasing rotor size and the spatial load variations along the blade, it is necessary to react to turbulence in a more detailed way; each blade separately and at several separate radial distances. In this paper, a proof of concept study is performed to show the feasibility of the load alleviation abilities of a ‘Smart’ blade, i.e. a blade equipped with a number of control devices that locally change the lift profile on the blade, combined with appropriate sensors and feedback controllers. Theoretical and experimental models are developed of a scaled non-rotating rotor blade which is equipped with two trailing edge flaps and strain sensors to facilitate feedback control. A pitch actuator is used to induce disturbances with a similar character as a gust or turbulence. A feedback controller based on classical loop shaping is designed that minimizes the root bending moment in the flapping direction. We show that with appropriate control techniques, the loads for periodic disturbances and for turbulence generated disturbances can be reduced up to 90 and 55%, respectively. Copyright © 2008 John Wiley & Sons, Ltd.

Robust Multivariable Pitch Control Design for Load Reduction on Large Wind Turbines

Abstract: This paper deals with multivariable pitch control design for wind turbines, including load reducing control objectives. Different design approaches, including collective and cyclic pitch, and robustness aspects are discussed. A control design with decoupled controllers for collective and cyclic pitch is worked out in detail, based on the H ∝ norm minimization approach. The control design is verified by simulations with a full nonlinear model of the wind turbine, showing the potential of multivariable pitch control to actively increase damping of the first axial tower bending mode and to reduce 1p fluctuations in blade root bending moments. Multivariable control design provides a convenient way of including additional load reducing objectives into the pitch controller of wind turbines. Fatigue loading of certain components, as tower and blades, could be reduced significantly.

Pitch Angle Control of Variable Speed Wind Turbine

Abstract: The aim of this study is to design a simple controller to maximize the extracted energy of wind turbines. In this study the pitch angle control of variable speed wind turbine is investigated. In particular, it concentrates on the extraction of maximum available energy, reduction of torque and output power variations, which gives stresses in the gearbox and mechanical structure. The control concentrates on separate wind speed internals as well as on whole wind speed region. It is found that the control structures varies substantially between the wind speed regions. Two different control systems are compared. The results show that pitch actuator with three levels of pitching speed have better response.

Wind power generation system and operating method thereof

Abstract: A wind power generation system wherein procedure for controlling the blade pitch is changed in accordance with the rate of decrease in the amplitude of the grid voltage, and when over current occurs in the grid-side power converter, the grid-side power converter is brought into the gate-blocked condition whereas the generator-side power converter continues its operation.

Aircraft propeller drive, method for driving an aircraft propeller, use of a bearing for an aircraft propeller drive and use of an electric machine

Abstract: To improve the damping of vibrations in aircraft propeller drives, the invention discloses an aircraft propeller drive comprising a propeller, a motor and a drive train between the propeller and the motor. The drive train of said aircraft propeller drive has a torsional vibration damper.

Control modes for extendable rotor blades

Abstract: A wind turbine may be controlled in a variety of manners to optimize operating parameters. In one arrangement, for example, the length or the pitch of a wind turbine rotor blade may be adjusted to avoid harmonic resonance frequencies. In another example, the length of a rotor blade may be modified to reduce noise or to optimize profits or both. The controls may be based on data from various types of sensors including accelerometers, sound meters, strain gauges and the like. Actuation of extendable rotor blades can rotate wind turbine rotors without wind or generator pulsing affording multiple advantages. A battery test control may also be used to determine the operational readiness of a battery useful for a variety of purposes in a turbine.

Adaptive Pitch Control of Variable-Speed Wind Turbines

Abstract: The aerodynamic efficiency of a variable-speed wind turbine operating in Region 2, or below-rated wind speeds, is greatly affected by the identification of accurate parameters for the controller. In particular, the power coefficient (Cp) surface must be well known for optimal efficiency to be achieved with a constant-gain controller. However, adaptive control can overcome the inefficiencies caused by inaccurate knowledge of the Cp surface. Previous work focused on adaptive torque gain control to cause a variable-speed turbine to operate, on average, at the tip-speed ratio λ* for which the maximum Cp occurs. This paper considers the effects of adaptive blade pitch angle control on a turbine’s aerodynamic efficiency. Computer simulations and tests on a field turbine are used to verify the adaptive pitch control scheme. Simulation and field test results demonstrate that the adaptive pitch controller causes the pitch angle to approach its optimal value. Adaptive pitch control can be used to seek the optimal pitch angle for energy capture in Region 2 operation. Additional field operation is required before a statistically significant improvement in energy capture can be demonstrated.

State-Space Control of Tower Motion for Deepwater Floating Offshore Wind Turbines

Abstract: The offshore wind energy potential is huge and to capture that energy, turbines have to be placed further offshore. Floating wind turbines offer a solution for deep waters. However, a floating wind turbine has extra motions that will affect the turbine in power production and structural loads. Therefore, the turbine control system has to be able to regulate power production and maintain safe operation of the turbine under incident wind and wave conditions. The work presented here discusses the application of state-space optimal controllers to regulate rotor speed and platform pitch above rated wind speed. A gain scheduled PI controller is used as a baseline to gauge the performance of the new controllers developed. A collective pitch linear quadratic regulator, designed to only regulate rotor speed and platform pitch, improves system performance but this improvement is thought to be due to better controller tuning as both controllers use the same mechanism to restore platform pitch and regulate speed. Individual blade pitch control using periodic control theory is applied because it uses a different mechanism to regulate platform pitch. Preliminary simulation results show that individual blade pitch control has platform pitch regulation over collective pitch controllers. However, unintended excitation of platform roll indicate that a more complicated controller may be required to ensure closed loop stability of the entire floating turbine.

Vertical speed and flight path command algorithm for displacement collective utilizing tactile cueing and tactile feedback

Abstract: A flight control system includes a collective position command algorithm for a lift axis (collective pitch) which, in combination with an active collective system, provides a force feedback such that a pilot may seamlessly command vertical speed, flight path angle or directly change collective blade pitch. The collective position command algorithm utilizes displacement of the collective controller to command direct collective blade pitch change, while a constant force application to the collective controller within a 'level flight' detent commands vertical velocity or flight path angle. The 'level flight' detent provides a tactile cue for collective position to reference the aircraft level flight attitude without the pilot having to refer to the instruments and without excessive collective controller movement.

A method of operating a wind turbine with pitch control, a wind turbine and a cluster of wind turbines

Abstract: A method of operating a pitch controlled wind turbine connected to the utility grid in response to an increase in wind velocity to above a predefined value. The method includes the sequential steps of: reducing the generated power, allowing an intermediate increase in the generator speed, and reducing the generator speed by pitching the wind turbine rotor blades. A wind turbine and a cluster of wind turbines is also contemplated.

Computational study of the advancing-side lift-phase problem

Abstract: The prediction of airloads and the corresponding structural response in high-speed forward flight of rotors poses a significant challenge to predictive rotorcraft aeromechanics methods. One of the issues identified in the flight test data of the Puma and Black Hawk aircraft is the phase difference between the minimum lift coefficient and the minimum of the blade pitch on the advancing side of the rotor during high-speed forward flight. This is commonly referred to as the advancing-side lift-phase delay. In the present work, the unsteady three-dimensional flowfield on the advancing side of a helicopter rotor is analyzed using computational fluid dynamics in an attempt to quantify contributions to the preceding effect. Time-dependent two-dimensional computational fluid dynamics simulations of blade sections with combined pitch/freestream Mach number oscillation were carried out to isolate the contribution to the phase difference of pitch angle and Mach number variations in the absence of the complex rotor-induced flowfield, sideslip, and rotor blade dynamics. The results for the freestream Mach number oscillations show that the lift coefficient lags the Mach changes at outboard stations, but this effect is reduced for combined pitch/Mach number oscillations. Finite span and sideslip contributions to the phasing were quantified by investigating the chordwise extent of supersonic flow on the advancing side for two nonlifting rotors in high-speed flight. Finally, the UH-60A rotor in high-speed forward flight was considered. By comparing results for rigid blades with results for a prescribed blade torsional deflection, the contribution of the blade torsion to the advancing-blade lift phasing was also quantified. Furthermore, rigid-blade simulations with different flapping schedules demonstrated the sensitivity of the lift phasing to trim-state variations. It was found that Mach number effects are dominant and the lift phasing depends primarily on the encountered Mach number and pitch schedule. Further, the elastic torsional deflection of the blades effectively changes the pitch schedule of the blade sections and also plays a role in the phasing of the lift and pitching moment coefficients.

Rotor Blade Sectional Performance Under Yawed Inflow Conditions

Abstract: This study shows the results of pressure distribution measurements on a rotor blade of a horizontal axis wind turbine under various yawed operations. The experiments are carried out in a wind tunnel with a 2.4 m diameter test rotor. In the measurements, the power curve and pressure distributions are measured for different azimuth angles. By increasing yaw angle, the maximum value of power coefficient of the rotor decreases. The sign of the yaw angle does not have any effect on power performance. The aerodynamic forces are discussed using the axial and rotational force coefficients for each azimuth angle. In the case of higher tip speed ratios, the blade section passing on the upstream side in yawed operations has a greater contribution to the rotor torque than that on the downstream side. In this tip speed range, the aerodynamic forces at the 70% radius section appear proportional to the angle of attack. In the case of the lower tip speed ratios, the blade on the downstream side does not contribute to rotor torque, which appears to result from separation.

Flying object with tandem rotors

Abstract: A flying object with tandem rotors, in particular a helicopter, has a main rotor and a tandem rotor each with propeller blades which are driven by a rotor shaft and which is hinge-mounted to this rotor shaft. The angle between the surface of rotation of the main rotor and the rotor shaft may vary. A swinging manner on an oscillatory shaft is essentially transverse to the rotor shaft of the main rotor and is directed transversally to the longitudinal axis of the vanes. The main rotor and the tandem rotor each have an auxiliary rotor connected respectively to the main rotor and tandem rotor by a mechanical link. The swinging motions of the auxiliary rotor controls the angle of incidence (A) of at least one of the propeller blades of the main rotor and tandem rotor. There is an acute angle of displacement when viewing the propeller blades relative to the vanes in a direction perpendicular to their respective rotational planes.

Nonlinear robust control to maximize energy capture in a variable speed wind turbine

Abstract: The emergence of wind turbine systems for electric power generation can help satisfy the growing global demand. To maximize wind energy captured in variable speed wind turbines at low to medium wind speeds, a robust control strategy is presented. The proposed strategy simultaneously controls the blade pitch and tip speed ratio, via the rotor angular speed, to an optimum point at which the efficiency constant (or power coefficient) is maximum. The control method allows for aerodynamic rotor power maximization without the restrictions of exact wind turbine model knowledge. A series of numerical results show that the wind turbine can be controlled to achieve maximum energy capture.

Blade pitch management method and system

Abstract: A method for operating a wind turbine. The method includes providing a wind turbine having at least one blade having adjustable pitch angle that is adjusted according to an operational parameter schedule. A blade efficiency parameter is determined in response to a wind speed and a rotor speed. A minimum pitch angle is determined in response to the blade efficiency parameter and the pitch angle of the at least one blade in response to the blade efficiency parameter is maintained to an angle equal to or greater than the minimum pitch angle independent of the operational parameter schedule. A wind turbine plant and a method for servicing a wind turbine are also disclosed.

Post Stall Propeller Behavior at Low Reynolds Numbers

Abstract: Limited data exists for propeller and wind turbine post stall aerodynamics. Post stall aerodynamics was observed in small propellers at low Reynolds numbers. First, performance data (thrust, power, and efficiency) for a set variable pitch propellers was acquired in a wind tunnel. The propellers were 6 to 9.9 inches in diameter and were able to pitch to extreme angles. Second detailed geometric characteristics (pitch, chord, airfoil) of the propellers were measured. Finally, PROPID with and without stall delay models was used to simulate the propellers and predict the performance. Comparing the experimental and calculated results identified regions where post stall aerodynamics affected propeller performance.

Wind driven power generator with moveable cam

Abstract: A wind driven generator includes a rotor disposed in a cylindrical duct and supported by a frame for rotation in response to wind flowing through the duct. The rotor includes plural circumferentially spaced paralleled rotor blades supported for rotation about a generally horizontal axis. Each blade is supported for pivotal movement to change blade pitch, angle of attack or camber as the rotor rotates. A pitch or camber control motor, self-governing wind vane mechanism, or governing mechanism is operable to move a circular cam to vary blade pitch or camber to control rotor speed. The duct is mounted on a mast having a base supported on a foundation for pivotal movement to face the wind for maximizing air flow through the duct. Electric power generators are connected to opposite ends of the rotor at respective power output or drive shafts.

Speed controlled pitch system

Abstract: The present patent application concerns wind turbine having a rotor with a first rotor blade and a pitch control system with a controller and a first drive system for adjusting a pitch angle of the first rotor blade, wherein the drive system is adapted to transform rotational energy of the rotor blade rotating about its longitudinal axis into another form of energy such that a counter torque against the rotating direction is induced. Further, it concerns a method for controlling a pitch velocity of a rotor blade of a wind turbine, the wind turbine comprising at least one drive system for adjusting a pitch angle of said rotor blade, the drive system being adapted to operate in a active mode, wherein the drive system rotates the rotor blade, and in a passive mode, wherein the drive system exerts a counter force against the rotating direction, when the rotor blade being rotated by another force than the force of the drive system, wherein the pitch velocity is controlled by operating the drive system in said passive mode when the pitch of the rotor blade is changed from a first position to a second position.

Lightning protection system for a wind turbine rotor blade and a method for manufacturing such a blade

Abstract: The invention relates to a wind turbine rotor blade comprising a blade tip and a lightning protection system. The rotor blade includes at least one lightning receptor at the surface of the blade in an external distance (L ex ) from the distal end of the blade tip, and a lightning receptor base inside the rotor blade arranged at an first internal distance (L i1 ) from the distal end of the blade tip. The rotor blade further includes means for changing at least one electric property of the rotor blade at the lightning receptor base, as compared to the electric properties of the ambient air by increasing the electric field supported between the lightning receptor base and the inner surface of the rotor blade. The invention further relates to a method for manufacturing a wind turbine rotor blade.

Hydroelectric in-pipe generator

Abstract: The present device provides an in-pipe turbine generator having a conduit, a plurality of runner blades positioned within the conduit, and a pitch adjustment mechanism whereby the pitch of the runner blades may be varied. The pitch adjustment mechanism further includes pitch adjustment screws that are positioned on a tangential flat on the master pitch adjustment bevel gear. Rotation of the pitch adjustment screw rotates the master pitch adjustment bevel gear thereby rotating the blade hub gears and the runner blades. Runner blade torque and angular velocity is transferred to a DC power generator and may be converted to AC power.

Method and system for operating a wind turbine

Abstract: The present invention relates to a method and a system for operating a Wind Turbine (WTG), which WTG comprises a rotor comprising at least two blades, which blades are pitch regulated, where the rotor is connected to a shaft, which shaft is supported by bearings, and which shaft drives at least one generator, where the WTG uses a load regulation system for regulating the individual pitch of at least two blades. The object of the invention is to compensate for asymmetric load on the rotor in a wind turbine, a second object is to reduce wearing at shaft bearings in the wind turbine, and a third object is to increase the power production of a wind turbine. This can be achieved if the load regulation system measures the actual rotor load by at least one displacement sensor, which displacement sensor is measuring the bending of the main shaft, where the load regulation system based on the shaft bending regulates the individual pitch of the blades for compensating asymmetric load at the rotor.

Pitch bearing for wind turbine rotor blades

Abstract: A pitch bearing for a wind turbine rotor comprises a rotor hub and at least one rotor blade, the pitch bearing comprising a cylindrical inner bearing ring connectable to a rotor blade of the wind turbine rotor, a cylindrical outer bearing ring connectable to the rotor hub of the wind turbine rotor and an annular reinforcement section for reinforcing the outer bearing ring. The annular reinforcement section adjoins the cylindrical outer bearing ring at its radial outer surface.

System and method for controlling a wind turbine during loss of grid power and changing wind conditions

Abstract: An apparatus and method for controlling a wind turbine (100) having a plurality of blades (108) such that the blade angle (θ )of each blade is continuously adjusted during loss of grid power relative to a wind direction relative to an orientation of the nacelle (112) (i.e., yaw offset) and a rotor azimuth while keeping the orientation of the nacelle of the wind turbine substantially constant. The wind turbine is capable of pitching the blades a full 360 degrees and generating power from the rotation of the rotor shaft (116) during loss of grid power.

Analysis of Underwater Free Vibrations of a Composite Propeller Blade

Abstract: The free vibration characteristics of a composite marine propeller blade were studied. MAB and composite materials were used. Composites with symmetric, balanced and unbalanced stacking sequences were analyzed. Rotational effects and added mass were considered using the finite element method. The natural frequency of the blade in water was much lower than in air. The mode shapes of the blade are almost the same in air as in water. The anisotropy of the composites shift the contours of the mode shape. Generally, greater anisotropy corresponds to a lower natural frequency. The rotational effects can be ignored because the marine propeller rotates slowly.

Method and system for operating a wind turbine generator

Abstract: A method of operating a wind turbine generator having at least one wind turbine blade includes increasing a pitch angle of the at least one wind turbine blade as the at least one wind turbine blade rotates through a first range of blade azimuth values Such increasing of the pitch angle reduces acoustic emissions generated by the wind turbine generator The method also includes decreasing the pitch angle of the at least one wind turbine blade as the at least one wind turbine blade rotates through a second range of blade azimuth values Such decreasing of the pitch angle increases electric power generated by the wind turbine generator

fast hybrid helicopter with long range with longitudinal trim control

Abstract: A hybrid helicopter includes an airframe provided with a fuselage and a lift-producing surface together with stabilizer surfaces and a drive system including: a mechanical interconnection system between a rotor of radius (R) with collective pitch and cyclic pitch control of the blades of the rotor and at least one propeller with collective pitch control of the blades of the propeller; and at least one turbine engine driving the mechanical interconnection system. The hybrid helicopter includes first members for controlling the angle at which the at least one pitch control surface is set as a function of the bending moment exerted on the rotor mast relative to the pitch axis of the hybrid helicopter, and second members for controlling the cyclic pitch of the blades of the rotor in order to control the longitudinal trim of the hybrid helicopter as a function of flight conditions.