Showing papers on "Blade pitch published in 2003"

Individual Blade Pitch Control for Load Reduction

Abstract: If a pitch-regulated wind turbine has individual pitch actuators for each blade, the possibility arises to send different pitch angle demands to each blade. The possibility of using this as a way of reducing loads has been suggested many times over the years, but the idea has yet to gain full commercial acceptance. There are a number of reasons why this situation may be set to change, and very significant load reductions can result. Copyright © 2002 John Wiley & Sons, Ltd.

Method of operating a wind turbine

Abstract: A wind turbine has a generator (7) with a connected rotor (3) having a hub (4) and blades (5) rotatably connected to the hub for adjusting the pitch angle. In a method of operating such a wind turbine under climatic conditions, where there is a risk of icing on the blades and no or weak wind, the generator is used as a motor for driving the rotor and the pitch angle of the blades is adjusted to ensure that the resulting wind substantially hits the leading edge of the blades. Any ice formed may be removed by means of de-icing in a known manner.

Low voltage ride through for wind turbine generators

Abstract: A wind turbine. The wind turbine includes a blade pitch control system to vary a pitch of one or more blades and a turbine controller coupled with the blade pitch control system. A first power source is coupled with the turbine controller and with the blade pitch control system to provide power during a first mode of operation. Uninterruptible power supplies coupled to the turbine controller and with the blade pitch control system to provide power during a second mode of operation. The turbine controller detects a transition from the first mode of operation to the second mode of operation and causes the blade pitch control system to vary the pitch of the one or more blades in response to the transition.

Rotor blade for a wind power plant

Abstract: The invention concerns a rotor blade of a wind power installation and a wind power installation. One advantage of the present invention is to provide a rotor blade having a rotor blade profile, and a wind power installation, which has better efficiency than hitherto. A rotor blade of a wind power installation, wherein the rotor blade has a thickness reserve approximately in the range of between 15% and 40%, preferably in the range of between about 23% and 28%, and wherein the greatest profile thickness is between about 20% and 45%, preferably between about 32% and 36%.

Method and apparatus for wind turbine rotor load control

Abstract: Vertical and horizontal wind shears, yaw misalignment and/or turbulence act together to produce asymmetric loading across a wind turbine rotor. The resultant load produces bending moments in the blades that are reacted through the hub and subsequently to the low-speed shaft. As a result, the main shaft and main shaft flange are displaced from their at rest or non-aerodynamic load positions. The amount of shaft flange displacement is measured using one or more sensors. The output signals from the sensors are used to determine the magnitude and/or the orientation of the resultant rotor load. This information is used to effect the blade pitch change needed to reduce the load and thereby reduce fatigue and loading on various turbine components.

Periodic Disturbance Accommodating Control for Blade Load Mitigation in Wind Turbines

Abstract: Performance of a model-based periodic gain controller for wind turbines is presented using Disturbance Accommodating Control (DAC) techniques to estimate fluctuating wind disturbances. The control objective is to regulate rotor speed at above-rated wind speeds while mitigating cyclic blade root loads. Actuation is via individual blade pitch, and sensors are limited to rotor angle and speed. The modeled turbine is a two-bladed, downwind machine with simple blade and tower flexibility having four degrees of freedom. Comparisons are made to a time-invariant DAC controller and to a proportional-integral-derivative (PID) design. Simulations are performed using a fluctuating wind input and a nonlinear turbine model. Results indicate that the state-space control designs are effective in reducing blade loads without a sacrifice in speed regulation. The periodic controller shows the most potential because it uses a time-varying turbine model to estimate unmeasured states. The use of additional sensors to help reconstruct the blade flap rate can significantly improve the level of load attenuation, as witnessed in full-state feedback results.

Lightning protection of a pitch-controlled wind turbine blade

Abstract: A wind turbine rotor including a rotor hub (3) and a plurality of blades (4), and where each blade root (16) is connected to said rotor hub through a pitch bearing (5) in such a manner that the pitch angle of the blade is adjustable by a turning of the blade about its longitudinal axis relative to the rotor hub. The blade is provided with at least one electrically conducting lightening down-conductor (6) extending in the longitudinal direction of the blade to the blade root and being electrically isolated from the pitch bearing (5). A spark gap (15) is provided between the lightning down-conductor and the rotor hub, said spark gap (15) being adapted to conduct a lightning current passing through the lightning down-conductor. A sliding contact connection (7, 12) is provided parallel to the spark gap (15) between the lightning down-conductor (6) and the rotor hub (3), said sliding contact connection ensuring electrical contact between said lightening down-conductor (6) and said rotor hub (3) irrespective of the pitch angle of the blade. The invention also relates to a wind turbine including such a rotor.

Wind Shear and Turbulence Effects on Rotor Fatigue and Loads Control

Abstract: The effects of wind shear and turbulence on rotor fatigue and loads control are explored for a large horizontal axis wind turbine in variable speed operation from 4 to 20 m/s. Two and three blade rigid rotors are considered over a range of wind shear exponents up to 1.25 and a range of turbulence intensities up to 17%. RMS blade root flatwise moments are predicted to be very substantially increased at higher wind shear, and resultant fatigue damage is increased by many orders of magnitude. Smaller but similar trends occur with increasing turbulence levels. In-plane fatigue damage is driven by 1P gravity loads and exacerbated by turbulence level at higher wind speeds. This damage is higher by one to two orders of magnitude at the roots of the three blade rotor. Individual blade pitch control of fluctuating flatwise moments markedly reduces flatwise fatigue damage due to this source, and to a lesser degree the in-plane damage due to turbulence. The same is true of fluctuating rotor torque moments driven by turbulence and transmitted to the drive train. Blade root moments out of the plane of rotation aggregate to create rotor pitching and yawing moments transmitted to the turbine structure through the drive train to the yaw drive system and the tower. These moments are predicted to be relatively insensitive to turbulence level and essentially proportional to the wind shear exponent for the two blade rotor. Fluctuating moments are substantially reduced with individual blade pitch control, and addition of a teeter degree of freedom should further contribute to this end. Fluctuating pitching and yawing moments of the three blade rotor are substantially less sensitive to wind shear, more sensitive to turbulence level, and substantially lower than those for the two blade rotor. Mean rotor torque and hence power are essentially the same for both rotors, independent of wind shear, and somewhat reduced with individual blade pitch control of fluctuating flatwise moments. The same is true of mean rotor thrust, however fluctuations in rotor thrust are substantially reduced with individual blade pitch control. It appears, on balance, that higher wind shear coupled with turbulence effects should be accounted for in the fatigue design of large, long life turbines. Much more work is required on this problem.

Sensing of loads on wind turbine blades

Abstract: The invention relates to a wind power plant with a tower, a rotor having at least one rotor blade being substantially radially distant with respect to a rotor axis and being rotatably supported with respect to a substantially horizontal rotation axis in a portion at the top of said tower, preferably at machine nacelle rotatably supported on a rotation axis extending substantially along the gravitational direction, a sensor means associated to said rotor for generating sensor signals depending on the mechanical load of the rotor, and an analysis means, especially a data processing means, wherein at least two, preferably pair-wise mounted, sensor elements are associated to at least one, preferably to each, rotor blade of the rotor and the evaluation means is designed for determining evaluation signals representing the mechanical loads of at least one rotor blade on the basis of the sensor signals generated by the sensor elements associated to this rotor blade.

Redundant blade pitch control system for a wind turbine and method for controlling a wind turbine

Abstract: A redundant and fail-safe blade system of a wind turbine includes at least one blade pitch drive ( 20, 21, 22 ) and at least two power control modules ( 60, 61, 62, 6′ ) for controlling the blade pitch drive ( 20, 21, 22 ). The power control modules ( 60, 61, 62, 6′ ) are connected to the blade pitch drive ( 20, 21, 22 ) by a switching unit ( 10 ) which allows an alternative connection between the blade pitch drive ( 20, 21, 22 ) and any of the power control modules ( 60, 61, 62, 6′ ). In operation, the blade pitch drive ( 20, 21, 22 ) is controlled by only one of the power control modules ( 60, 61, 62, 6′ ). If a malfunction of the currently operating power control module ( 60, 61, 62, 6′ ) is detected, switching unit ( 10 ) provides a connection to the other power control module ( 60, 61, 62, 6′ ) to allow an ongoing operation of the wind turbine without an unplanned or forced shut-down.

Disturbance Tracking and Blade Load Control of Wind Turbines in Variable-Speed Operation

Abstract: A composite state-space controller was developed for a multi-objective problem in the variable-speed operation of wind turbines. Disturbance Tracking Control theory was applied to the design of a torque controller to optimize energy capture under the influence of persistent wind disturbances. A limitation in the theory for common multi-state models is described, which led to the design of a complementary pitch controller. The goal of the independent blade pitch design was to minimize blade root fatigue loads. Simulation results indicate an 11% reduction in fatigue damage using the proposed controllers, compared to a conventional torque-only design. Meanwhile, energy capture is almost identical, partly because of nonlinear effects.

Disturbance Tracking Control and Blade Load Mitigation for Variable-Speed Wind Turbines

Abstract: A composite linear state-space controller was developed for a multi-objective problem in the variable-speed operation of wind turbines Disturbance Tracking Control theory was applied to the design of a torque controller to optimize energy capture under the influence of persistent wind disturbances A limitation in the theory for common multi-state models is described; this led to the design of a complementary pitch controller The goal of the independent blade pitch design was to minimize blade root fatigue loads A SymDyn model of a two-bladed, 600-kW machine was used for the simulation studies Results indicate a 24% reduction in blade fatigue damage using the proposed controllers, compared to a conventional torque-only design However, energy capture was not improved as much as expected, partly due to nonlinearity effects degrading the performance of the state-space estimator design Tower base fatigue damage was shown to decrease significantly using active pitch

Actuation system for a controllable pitch propeller

Abstract: A propeller control system (20) provides for actuation through supply pressure only. A transfer bearing (38) thereby requires only a single land. The supply pressure is metered at a pitch change valve (40) within the rotating propeller shaft (28) downstream of the transfer bearing (38) to provide hydraulic pressure for actuation and control. A feather override mode is provided by energizing a feathering solenoid (44). The increased supply pressure changes the hydraulic force balance of the pitch change valve (40) to allow the increased supply pressure into a Coarse Pitch chamber and simultaneously allow fluid within the Fine Pitch chamber to flow to drain pressure. The flow to drain changes the hydraulic balance on the Pitch Change Actuator Piston (48) to drive a pitch link (50) attached to each propeller blade (32)and thereby change the pitch thereof towards coarse pitch.

Method for mounting a rotor blade of a wind energy installation without using a crane

Abstract: Mobile cranes have been used to mount rotor blades on wind energy installations for a long time. Such cranes pick up the rotor blade at the foot of the wind energy installation and guide it up to the rotor blade connection of the hub of the wind energy installation, so that the rotor blade can be connected to the hub. Said connection is carried out mostly by screwing, in that screw bolts are countersunk in the connecting flange of the rotor blade and project into corresponding boreholes in the rotor blade connection of the hub, in such a way that nuts can be screwed onto the screw bolts. The invention relates to a method for mounting blades according to patent claim 1. Advantageous developments are described in the following claims. The inventive method is used to mount a rotor blade (12) of a wind energy installation (1) onto a rotor blade connection (9) on a hub (8) of a rotor (5) of the wind energy installation (1), or to dismount said rotor blade from the same, without using a crane. According to said method, at least one cable (14, 15) is fixed between a part in the hub region (8) of the wind energy installation and the bottom (13) of the wind energy installation (1), and the rotor blade (12) is moved upwards along the cable (14, 15) when mounted and downwards along the cable when dismounted.

Torque- and Speed Control of a Pitch Regulated Wind Turbine

Abstract: Variable speed operated wind turbines has the potential to reduce fatigue loads, compared to fixed speed wind turbines. With pitch controllable rotor blades limitation of the power at high wind speeds is obtained. The thesis describes different controlling aspects concerning wind turbines and how these together can be used to optimize the system's performance. Torque control is used in order to achieve reduction on the mechanical loads on the drive-train for low wind speeds and limitation of power output for high wind speeds. In the high wind speed interval torque control is effective in order to limit the output power if a suffciently fast pitch actuator is used. In the middle wind speed interval filter utilization can be used to give a reference signal to the controller in order to reduce speed and torque variations.

Predicting the Contribution of Running Propellers to Aircraft Stability Derivatives

Abstract: Running propellers can have a profound effect on the trim and static stability of an airplane. The method most commonly used for determining propeller stability derivatives is based on blade element theory with the axial component of induced velocity taken to be that predicted from classical propeller momentum theory, which neglects the effects of slipstream rotation. The induced flow that is predicted by classical propeller momentum theory is not consistent with the actual induced flow in the vicinity of a rotating propeller. In the present paper, an alternative method for predicting propeller stability derivatives is proposed. This method is based on blade element theory with the induced velocity predicted from propeller vortex theory. Nomenclature

Cyclic actuation system for a controllable pitch propeller and a method of providing aircraft control therewith

Abstract: A propeller control generates a once per revolution (1P) blade thrust variation through cyclic pitch of rigidly mounted non-flapping propeller blades. The resultant shaft bending moment is used to provide aircraft attitude control. Axial translation of a pitch change assembly including a pitch change yoke along an axis of rotation drives a pitch link attached to each propeller blade to collectively change the propeller blade pitch angle. The pitch change yoke includes a translating pitch change yoke portion and an articulatable pitch change yoke portion. Deflection of the articulatable pitch change yoke portion changes the pitch change effect of each pitch link as a function of its angular position such that a sinusoidal pitch angle is superimposed on normal pitch angle. Cyclic pitch change actuators deflect the articulatable pitch change yoke portion in any angular direction while the linear deflection of the cyclic pitch change actuators generate the magnitude of the cyclic pitch.

Wind power plant, control arrangement for a wind power plant, and method for operating a wind power plant

Abstract: The invention relates to a wind power plant with a tower, a rotor having at least one rotor blade being substantially radially distant with respect to a rotor axis and being rotatably supported with respect to a substantially horizontal rotation axis in a portion at the top of said tower, preferably at machine nacelle rotatably supported on a rotation axis extending substantially along the gravitational direction, a sensor means associated to said rotor for generating sensor signals depending on the mechanical load of the rotor, and an analysis means, especially a data processing means, wherein at least two, preferably pair-wise mounted, sensor elements are associated to at least one, preferably to each, rotor blade of the rotor and the evaluation means is designed for determining evaluation signals representing the mechanical loads of at least one rotor blade on the basis of the sensor signals generated by the sensor elements associated to this rotor blade.

Rotor blade pitch control assembly

Abstract: A rotor blade assembly provides a pitch control assembly to pitch the rotor blade about a rotor blade pitch axis. The pitch control assembly includes a trailing edge flap and a trailing edge servo flap that extend from the trailing edge of the rotor blade. The trailing edge flap is offset in the span wise direction relative to the trailing edge flap. The trailing edge servo flap is located upon a trailing edge servo flap arm linked to the trailing edge flap. To pitch the rotor blade, the trailing edge servo flap is pitched in a direction opposite the desired pitch direction of the trailing edge flap.

Rotor Configuration Effects on the Performance of a HAWT With Tip-Mounted Mie-Type Vanes

Abstract: In this paper, the relationships between the power augmentation of a HAWT due to Mie-type tip vane application and other factors influencing the efficiency of a wind turbine such as the blade aspect ratio, number of blades, blade pitch angle and Reynolds number are investigated. Experiments were carried out in a wind tunnel with an open, 3.6 m diameter, test section. Rotor models included two- and three-blade upwind turbines with four sets of blades with different aspect ratios. With the rotor blades tested, a maximum power augmentation of about 14.5% was achieved due to Mie vane application. The relationships between power augmentation due to the Mie vane and the above factors are investigated. It is found that the application of a tip-mounted Mie vane results in a larger increase in maximum power coefficient for rotors with smaller aspect ratios and for lower wind speeds. Surface oil film and surface tuft visualization methods were used to detect the flow patterns at the blade tip. Addition of the Mie vanes causes significant changes in flow behavior near the blade tip, resulting in additional blade lift.

Load-receiving arrangement for wind turbine wings

Abstract: The invention relates to a rotor blade (10) of a wind power plant, comprising a rotor blade connection that is joined to a rotor hub (12) of a wind power plant, and a rotor blade tip (13) located at the opposite end of the rotor blade (10). In order to create a rotor blade (10) in which a deflection can be detected with simple means, at least one electrical conductor (20, 21, 22, 23, 24, 26) that begins at the rotor blade connection and extends in the longitudinal direction of the rotor blade and back to the rotor blade connection is laid across the entire length of the rotor blade (10) while a detector (16) which detects the electrical resistance of the conductor (20, 21, 22, 23, 24, 26) is connected to a device evaluating said electrical resistance. The invention is based on the recognition that any deflection of the rotor blade results in the support structure being extended and that said extension modifies the electrical resistance of an electrical conductor when transferred thereto. The degree of deflection of the rotor blade can be inferred from the modification of the electrical resistance because said modification is proportionate to the extension of the conductor, which is proportionate to the deflection of the rotor blade.

Wind turbine with a plurality of rotors

Abstract: A wind turbine with an array of rotors arranged at various heights Each rotor is optimized for the height at which it is located Optimization of each rotor could include selection of rated power, solidity, tip speed, blade taper, or rotor diameter Each rotor can also be operated in a manner that is optimized for the wind speed it experiences Optimized operation parameters could include blade pitch angle or rotor speed

Blade pitch angle control device and wind power generation device

Abstract: PROBLEM TO BE SOLVED: To control a pitch angle with high accuracy, and to realize further reduction of load change caused in a wind power generation device at low cost. SOLUTION: The blade pitch angle control device has a memory part 10 storing a prescribed parameter, an azimuth angle, and a pitch angle command value having influence on the load change of a blade, being related to each other, an azimuth angle detecting part 11 for detecting the azimuth angle for every blade, a parameter detecting part 12 for detecting the prescribed parameter, a command value obtaining part 13 for obtaining the pitch angle command value for every blade selected by the azimuth angle for every blade detected with the azimuth angle detecting part 11 and the prescribed parameter detected with the parameter detecting part 12, from the memory part 10; and a pitch angle control command value generating part 14 for generating a pitch angle control command value for individually controlling the pitch angle of the blade based on the pitch angle command value and a common pitch angle command value. COPYRIGHT: (C)2005,JPO&NCIPI

Stabilization of Helicopter Blades with Severed Pitch Links Using Trailing-Edge Flaps

Abstract: The feasibility of using trailing-edge flaps to reconfigure a helicopter rotor blade following a failure of the pitch link is addressed, which makes the blade free floating in pitch and otherwise uncontrollable. A coupled rotor-fuselage model is developed that allows for rotor anisotropy. A new, optimization-based, trim procedure is developed to determine the dynamics of the failed blade and the flap inputs required for reconfiguration. The trailing-edge flap can correct the otherwise catastrophic consequences of a pitch link failure. The residual 1 and 2/rev (revolution) components of the hub loads are reasonably small with a one-harmonic flap input and essentially disappear if a second harmonic is added to the flap input. The required flap deflections are high but not unreasonable. The flap acts by generating a rigid-body pitching motion of the free-floating blade that matches the angles that otherwise would have been generated by the swashplate. The steady-state flapping motion of the reconfigured blade is very nearly identical to those of the undamaged blades, The solutions are very sensitive to phase errors in the first harmonic of the flap inputs. The sensitivity is lower for the constant and the second harmonic inputs. The result suggests that if a helicopter rotor is equipped with trailing-edge flaps for other purposes such as vibration or noise reduction, these flaps could be used as emergency control surfaces.

Blade pitch control disk device for a rotorcraft rotor

Abstract: A cyclic swashplate device for controlling rotorcraft blade pitch is disclosed for application to rotorcraft swashplates, in particular, in helicopters. A cyclic swashplate device controls the rotorcraft blade pitch. The device ( 10 ′), with rotating ( 10 ′) and non-rotating ( 14 ′) cyclic swashplates is designed in such a way that at least one of the two disks includes a modular link fitting assembly ( 46, 42 ) ensuring the links with the disk ( 12′, 14 ′) and the pitch connecting rods ( 6 ) and/or at least one driving device or with the pilot control devices ( 17 ) and/or at least one retaining device. Interconnecting fittings are attached rigidly and separately to an annular device, such as one of the rings ( 31′, 30 ′) of a bearing ( 21 ′) on the corresponding disk ( 14′, 12 ′).

Transverse flow blower and blade for the same

Abstract: PROBLEM TO BE SOLVED: To provide a transverse flow blower and a blade for the same in which blade pitch noises can be reduced by improving mechanical unbalance. SOLUTION: In the bladed wheel 20, ring-shaped support discs 21 are arranged in parallel with one another at given intervals in a driving shaft 24 direction and then blades 22 are supported in parallel with the driving shaft 24 at prescribed intervals between each of the support discs 21. Outer circumferential ends of the blades 22 are formed into corrugated shapes with concavity and convexity in the directions of their thickness and are parallel with lip portions not to be subjected to line interference with the lip portions 26. Then, the blades 22 come to partially interfere with the lip portions 26 along with a rotation of the bladed wheel 20, which can decrease an air volume colliding simultaneously with the lip portions 26 to be able to reduce possibility to form eccentric large concentric vortexes. As a result, the noises can be decreased. COPYRIGHT: (C)2005,JPO&NCIPI

Development of the Identification Model

Abstract: The goal of our system identification is to achieve the best possible fit of the estimated frequency responses and, ultimately, the vehicle responses, with a model that is physically meaningful and that has an accuracy well suited for high-bandwidth control design applications

Horizontal axis windmill and its control method

Abstract: PROBLEM TO BE SOLVED: To provide a horizontal axis windmill and its control method capable of effectively suppressing overspeed or output reduction of a rotor even in an environment where the fluctuation of wind speed is large, and of substantializing acquisition of stable rated power. SOLUTION: The horizontal axis windmill 1 is equipped with the rotor 4 having a blade with a variable pitch angle, and the pitch angle of the blade is changed according to fluctuation of wind speed so that the rotation speed of the rotor 4 converges to a predetermined target value. The windmill 1 includes a means for calculating wind acceleration speed, and a means for changing the target value on the basis of the calculated wind acceleration speed. In the method for the horizontal axis windmill 1, which changes the pitch angle of the blade according to fluctuation of wind speed to converge the rotation speed of the rotor 4 to the predetermined target value, the acceleration speed of the wind blown on the horizontal axis windmill 1 is calculated (wind acceleration calculating process S20), and the target value is changed on the basis of the calculated wind acceleration (target value changing process S31, S41). COPYRIGHT: (C)2005,JPO&NCIPI

comprehensive aeroelastic analysis of helicopter rotor with trailing-edge flap for primary control and vibration control

Abstract: : A comprehensive aeroelastic analytical model of helicopter rotors with trailing-edge flaps for primary and vibration controls has been developed. The derivation of system equations is based on Hamilton principles, and implemented with finite element method in space and time. The blade element consists of fifteen degrees of freedom representing blade flap, lag, torsional, and axial deformations. Three aerodynamic models of flapped airfoils were implemented in the present analysis, the unsteady Hariharan-Leishman model for trailing-edge flaps without aerodynamic balance, a quasi-steady Theodorsen theory for an aerodynamic balanced trailing-edge flap, and table lookup based on wind tunnel test data. The trailing-edge flap deflections may be modeled as a degree of freedom so that the actuator dynamics can be captured properly. The coupled trim procedures for swashplateless rotor are solved in either wind tunnel trim or free flight condition. A multicyclic controller is also implemented to calculate the flap control inputs for minimization of vibratory rotor hub loads. The coupled blade equations of motion are linearized by using small perturbations about a steady trimmed solution. The aeroelastic stability characteristics of trailing-edge flap rotors is then determined from an eigenanalysis of the homogeneous equations using Floquet method. The correlation studies of a typical bearingless rotor and an ultralight teetering rotor are respectively based on wind tunnel test data and simulations of another comprehensive analysis (CAMRAD II). Overall, good correlations are obtained. Parametric study identifies that the effect of actuator dynamics cannot be neglected, especially for a torsionally soft smart actuator system. Aeroelastic stability characteristics of a trailing-edge flap rotor system are shown to be sensitive to flap aerodynamic and mass balances. Key parameters of trailing-edge flap system for primary rotor control are identified as blade pitch index angle