Method for setting a pitch angle of a rotor blade, control device for setting a pitch angle, and associated wind turbine

Abstract

A method for setting a pitch angle of a rotor blade for a rotor of a wind turbine, a control device for setting a pitch angle of a rotor blade for a rotor of a wind turbine, and a wind turbine. In particular, a method for setting a pitch angle of a rotor blade for a rotor of a wind turbine, in particular for avoiding suction-side flow separation, wherein the rotor blade is movable rotationally about a rotor blade longitudinal axis for setting the pitch angle by means of a pitch drive, comprising the steps: determining an aerodynamic power of the rotor, establishing a nominal pitch angle as a function of the aerodynamic power, and setting the pitch angle to the established nominal pitch angle.

Claims

1. A method comprising: setting a pitch angle of a rotor blade of a rotor of a wind turbine, wherein the rotor blade is configured to move rotationally about a rotor blade longitudinal axis for setting the pitch angle by a pitch drive, wherein the setting comprises: determining an aerodynamic power of the rotor; establishing a nominal pitch angle as a function of the aerodynamic power; and setting the pitch angle to the established nominal pitch angle, wherein the nominal pitch angle is established based on an aerodynamic power factor depicted in a portionally linear control function, wherein portions of the portionally linear control function are defined by the aerodynamic power, and the aerodynamic power factor is a power-dependent additional blade angle.

2. The method according to claim 1, wherein the aerodynamic power is determined from at least one of: a generated electrical power, a power loss, or an acceleration power of the rotor, wherein the aerodynamic power is a sum of the electrical power, the power loss, and the acceleration power.

3. The method according to claim 2, wherein the power loss is formed from a sum of a measurable power loss and an estimated power loss, wherein the estimated power loss is established by multiplying an estimation parameter by the electrical power.

4. The method according to claim 2, wherein the acceleration power is established from at least one of: an inertia moment of the rotor, an angular speed, or an angular acceleration, wherein the acceleration power is established by multiplying the inertia moment of the rotor by the angular speed or angular acceleration.

5. The method according to claim 1, wherein the nominal pitch angle is formed from an adjustment gradient, wherein the adjustment gradient is formed from the pitch angle and the aerodynamic power.

6. The method according to claim 1, wherein a minimum pitch angle is taken into account when establishing the nominal pitch angle, wherein the minimum pitch angle and the aerodynamic power factor are taken into account, wherein the minimum pitch angle and the aerodynamic power factor are added together to establish the nominal pitch angle.

7. The method according to claim 1, wherein the nominal pitch angle is established with the following portionally linear control function: $\alpha ={\alpha }_{\min }+\left\{\begin{array}{c}0,\mathrm{if}{P}_{\mathrm{aero}}<P_{\min ,1},\\ \frac{\partial \alpha }{\partial P_1}*\left(P_{\mathrm{aero}}-P_{\min ,1}\right),\mathrm{if}{P}_{\min ,1}\le P_{\mathrm{aero}}<P_{\min ,2},\\ \frac{\partial \alpha }{\partial P_1}*\left(P_{\min ,2}-P_{\min ,1}\right)+\frac{\partial \alpha }{\partial P_2}*\left(P_{\mathrm{aero}}-P_{\min ,2}\right),\mathrm{if}{P}_{\min ,2}\le P_{\mathrm{aero}}\end{array}\right\},$ wherein α is the nominal pitch angle, α.sub.min is the minimum pitch angle, P.sub.aero is the aerodynamic power, P.sub.min,1 is a first power threshold value, P.sub.min,2 is a second power threshold value, $\frac{\partial \alpha }{\partial P_1}$ is a first adjustment gradient, and $\frac{\partial \alpha }{\partial P_2}$ is a second adjustment gradient.

8. The method according to claim 1, wherein at least one signal is filtered.

9. The method according to claim 1, wherein the pitch angle is set to the established nominal pitch angle if a difference between the established nominal pitch angle and a set pitch angle value is greater than a minimum setting angle.

10. The method according to claim 1, wherein the nominal pitch angle is established as a function of the aerodynamic power in an upper partial load range, wherein the upper partial load range lies between a full load range and a lower partial load range.

11. The method according to claim 1 wherein pitch angle is configured to reduce or prevent suction-side flow separation.

12. A method comprising: setting a pitch angle of a rotor blade of a rotor of a wind turbine, wherein the rotor blade is configured to move rotationally about a rotor blade longitudinal axis for setting the pitch angle by a pitch drive, wherein the setting comprises: determining an aerodynamic power of the rotor; establishing a nominal pitch angle as a function of the aerodynamic power; and setting the pitch angle to the established nominal pitch angle, wherein a minimum pitch angle is taken into account when establishing the nominal pitch angle, wherein the minimum pitch angle and an aerodynamic power factor are taken into account, wherein the minimum pitch angle and the aerodynamic power factor are added together to establish the nominal pitch angle, wherein the nominal pitch angle is established based on the aerodynamic power factor depicted in a portionally linear control function, wherein portions of the portionally linear control function are defined by the aerodynamic power, and the aerodynamic power factor is a power-dependent additional blade angle, wherein the portionally linear function has a first portion, a second portion, and a third portion, wherein the first portion is defined for an aerodynamic power which is less than a first power threshold value, wherein the nominal pitch angle in the first portion corresponds substantially to the minimum pitch angle, wherein the second portion is defined for an aerodynamic power which is greater than or equal to the first power threshold value and less than a second power threshold value, wherein the nominal pitch angle in the second portion is a sum of the minimum pitch angle and a first aerodynamic power factor, wherein the first aerodynamic power factor is established as a function of at least one of: a first adjustment gradient, the aerodynamic power, or the first power threshold value, and wherein the third portion is defined for an aerodynamic power which is greater than or equal to the second power threshold value, wherein the nominal pitch angle in the third portion is a sum of the minimum pitch angle and a second aerodynamic power factor, wherein the second aerodynamic power factor is established as a function of at least one of: a second adjustment gradient, the aerodynamic power, the second power threshold value, the first adjustment gradient, or a difference between the second power threshold value and the first power threshold value.

13. A control device comprising circuitry configured to set a pitch angle of a rotor blade for a rotor of a wind turbine by establishing a nominal pitch angle as a function of an aerodynamic power of the rotor and actuating a pitch drive to set the pitch angle of the rotor blade such that the pitch angle is set to the established nominal pitch angle by the pitch drive, wherein the circuitry is configured to establish the nominal pitch angle based on an aerodynamic power factor depicted in a portionally linear control function, wherein the portions of the portionally linear control function are defined by the aerodynamic power, and the aerodynamic power factor is a power-dependent additional blade angle.

14. The control device according to claim 13, wherein the nominal pitch angle is formed from an adjustment gradient, wherein the adjustment gradient is formed from a pitch angle and the aerodynamic power.

15. A control system comprising: the control device according to claim 13, and a pitch drive for signal transmission for adjusting a set pitch angle of the rotor blade, and wherein the control device provides the nominal pitch angle to the pitch drive.

16. The control system according to claim 15, comprising a controller structure configured to control the pitch angle based on the nominal pitch angle, wherein the controller structure has at least a first unit for determining the aerodynamic power and a second unit for establishing the nominal pitch angle as a function of the aerodynamic power.

17. A wind turbine comprising: a rotor having an adjustable-pitch rotor blade, wherein a pitch angle of the rotor blade is configured to be set by a pitch drive, and a control device according to claim 13, wherein the control device is coupled to the pitch drive for signal transmission and is configured to provide the pitch drive with a nominal pitch angle which has been established as a function of an aerodynamic power, wherein the pitch drive is configured to set the pitch angle based on the nominal pitch angle.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Preferred exemplary embodiments are explained as an example with reference to the appended figures. The drawings show:

(2) FIG. 1 shows a diagrammatic, three-dimensional view of an exemplary embodiment of a wind turbine;

(3) FIGS. 2-4 show diagrammatic, two-dimensional views of exemplary flow states on a rotor blade;

(4) FIG. 5 show a diagrammatic view of a controller structure for setting the pitch angle as known in the prior art;

(5) FIG. 6 shows an exemplary diagram of a power curve over time;

(6) FIG. 7 shows a schematic diagram to illustrate load regions;

(7) FIG. 8 shows an exemplary diagram to illustrate adjustment gradients;

(8) FIG. 9 shows a schematic exemplary view of a control device with a controller structure;

(9) FIG. 10 shows a schematic method.

(10) In the figures, the same elements or those with substantially the same or similar function are designated with the same reference signs.

DETAILED DESCRIPTION

(11) FIG. 1 shows a diagrammatic, three-dimensional view of a wind turbine 100. The wind turbine 100 has a tower 102 and a nacelle 104 on the tower 102. An aerodynamic rotor 106 with three rotor blades 108, each having a rotor blade length, and a spinner 110 are provided on the nacelle 104. The aerodynamic rotor 106 is set in rotational movement by the wind during operation of the wind turbine 100 and thus also turns an electrodynamic rotor of a generator which is coupled directly or indirectly to the aerodynamic rotor 106. The electrical generator is arranged in the nacelle 104 and generates electrical energy.

(12) The rotor blades 108 each have a rotor blade longitudinal axis 112. The rotor blade longitudinal axis 112 extends substantially from a root region of the rotor blade facing the nacelle 104 to a rotor blade tip facing away from the nacelle 104. The rotor blades 108 are arranged so as to be rotationally movable around the rotor blade longitudinal axis 112. In particular, a pitch angle 114 can be set by the rotational movement of the rotor blades 108 about the rotor blade longitudinal axis 112.

(13) To set the pitch angle 114, the wind turbine 100 has pitch drives 116. The pitch drives 116 couple the rotor blades 108 to the nacelle 104. Furthermore, the pitch drives 116 are arranged such that they can achieve a rotational movement of the rotor blades 108 about their rotor blade longitudinal axis 112. The wind turbine 100 furthermore comprises a control device 118. The control device 118 is configured for setting the pitch angle 114 of the rotor blades 108. In particular, the control device 118 is configured for establishing a nominal pitch angle as a function of an aerodynamic power of the rotor 106, and actuating the pitch drive 116 to adjust the pitch angle 114 such that the pitch angle 114 is set to the established nominal pitch angle by means of the pitch drive 116.

(14) The wind turbine 100 is furthermore configured to perform a method for setting the pitch angle 114 of at least one rotor blade 108 for the rotor 106. This method is suitable in particular for avoiding a suction-side flow separation, as will be explained in more detail below. The method comprises the steps: determining an aerodynamic power of the rotor 106 and/or at least one rotor blade 108, determining a nominal pitch angle as a function of the aerodynamic power, and setting the pitch angle 114 to the established nominal pitch angle.

(15) FIGS. 2 to 4 show diagrammatic, two-dimensional views of exemplary flow states at a rotor blade. The rotor blade 108 extends, in the direction of its profile depth, from a leading edge 120 to a trailing edge 122. The rotor blade 108 has a suction side 124 and a pressure side 128. During operation, an increased pressure prevails on the pressure side 128 and a reduced pressure on the suction side 124. Because of the increased pressure and reduced pressure, the rotor blade is set in motion. A suction-side flow 126 prevails on the suction side 124. A pressure-side flow 130 prevails on the pressure side 128.

(16) The flows 126, 130 are produced by a wind hitting the rotor blade 108. At the rotor blade 108, the wind has a contact flow speed 136 which is composed of the circumferential speed 134 and the wind speed 132. The angle of attack 138 is set between the direction of the contact flow speed 136 and a profile chord 121. The profile chord 121 extends from the leading edge 120 to the trailing edge 122.

(17) FIG. 3 shows the flow situation for a higher wind speed 132. Because the rotation speed and hence the circumferential speed 134 remain substantially constant, the angle of attack 138 changes. Accordingly, the direction of the contact flow speed 136 changes. The increase in angle of attack 138 promotes a flow separation on the suction side 124. The separation takes place physically by a pressure rise in the region close to the surface. The pressure rise in particular means a delay in the suction-side flow 126, sapping kinetic energy inside the boundary layer. This leads to a faster reduction in speed in the region close to the surface, usually resulting in a correspondingly greater pressure rise.

(18) This phenomenon may be countered if the pitch angle α is changed as shown in FIG. 4. By changing the pitch angle α, i.e., by changing the angle between the profile chord 121 and the direction of the wind 132, the angle of attack 138 may be reduced again. Because the angle of attack 138 is reduced, the suction-side flow 126 again flows around the suction side 124 without separation.

(19) FIG. 5 shows a diagrammatic view of a controller structure known from the prior art for setting a pitch angle. The angle of attack 204 is influenced by a wind speed 218, a rotation speed 220 and hence a circumferential speed, and by the pitch angle 224. In the controller structure shown here, as known from the prior art, the angle of attack 204 is adjusted via the pitch angle 224 in that the necessary pitch angle is determined via an electrical power 222.

(20) For this, the controller structure 200 comprises determination of the rotor inertia 206 and measurement of the rotation speed 208. Following a power specification 210, power regulation 212 takes place. The power regulation 212 determines a nominal blade angle 214 which is supplied to the pitch system 216. From this, the pitch angle 224 to be set is determined. Controlling the pitch angle 224 by means of the electrical power 222 leads to perceptible delays. These delays arise, for example, from the pitch system 216, the power regulation 212, the rotation speed measurement 208 and the rotor inertia 206.

(21) These delays in the controller structure 200 shown lead to a phase offset which limits the permitted extent of feedback amplification. For example, the slower the power regulator 212 reacts to a rotation speed rise by increasing the electrical power 222, usually the smaller the changes in the determination of the nominal blade angle 214 must be for the controller structure to remain stable.

(22) Because of these delays, the phase shift shown in FIG. 6 occurs between the aerodynamic power 234 and electrical power 236. Here the abscissa shows the time 232 and the ordinate shows the power 230. It is evident that a phase shift of around 90° exists between the aerodynamic power and the electrical power. This phase offset leads to a non-optimal setting of the pitch angle. This phenomenon is relevant in particular in the upper partial load range 246 shown in FIG. 7. This is because the rotation speed is here substantially constant, so that in the aerodynamic model the circumferential speed is also substantially constant.

(23) The rotation speed-power curve 244 depicted in FIG. 7 shows the power 240 as a function of a rotation speed 242. In the upper partial load region 246, the power 240 rises greatly while the rotation speed 242 remains substantially constant. Because of the delays, setting a nominal pitch angle is also associated with delays. This phenomenon is evident in particular from FIG. 8. Here the power 252 is shown over a pitch angle 250. The pitch angle curve 254 shows two different characteristics. There are two different adjustment gradients 256, 258 for reaching a nominal pitch angle 260.

(24) Because of the delays, only a low first adjustment gradient 256 is possible. By means of the aspects described above, the second adjustment gradient 258 can be implemented. In particular, this higher second adjustment gradient 258 is possible by setting the nominal pitch angle, in particular for determining an adjustment gradient, on the basis of the aerodynamic power and not the electrical power. It is evident from FIG. 8 that pitch adjustment takes place only above a higher limit power in order to achieve a pitch angle required at a limit power. This is made possible in particular because of the steeper second adjustment gradient 258. In this way, with steeper adjustment gradients, the wind turbine may be operated with economically advantageous low pitch angles over a greater operating range of the installation.

(25) Such steeper second adjustment gradients 258 are possible, for example, with the control device 118 shown in FIG. 9 and the controller structure shown there. The angle of attack 304 is dependent on the wind speed 316, the rotation speed 318 and the pitch angle 324. The aerodynamic power determination 310 is determined by means of a rotor inertia 306 and a rotation speed measurement 308, and taking into account the electrical power 320. On the basis of the aerodynamic power 322, an adjustment gradient 312 can be determined which is provided to the pitch system 314. The pitch system 314 then sets a defined pitch angle 324 at the turbine. Accordingly, steeper adjustment gradients 312 are possible so that the wind turbine can be operated economically with smaller blade angles over a larger operating range.

(26) FIG. 10 shows a diagrammatic method. In step 400, an aerodynamic power of the rotor of the wind turbine is determined. In step 402, a nominal pitch angle is established as a function of the aerodynamic power. In step 404, the pitch angle is set to the established nominal pitch angle. Because the nominal pitch angle is determined as a function of the aerodynamic power and not with direct dependency on the electrical power, shorter delays occur and hence the installation can be operated economically for longer periods with a smaller pitch angle.

(27) The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

LIST OF REFERENCE SIGNS

(28) 100 Wind turbine

(29) 102 Tower

(30) 104 Nacelle

(31) 106 Rotor

(32) 108 Rotor blades

(33) 110 Spinner

(34) 112 Rotor blade longitudinal axis

(35) 114 Pitch angle

(36) 116 Pitch drive

(37) 118 Control device

(38) 120 Leading edge

(39) 121 Profile chord

(40) 122 Trailing edge

(41) 124 Suction side

(42) 126 Suction-side flow

(43) 128 Pressure side

(44) 130 Pressure-side flow

(45) 132 Wind speed

(46) 134 Circumferential speed

(47) 136 Contact flow speed

(48) 138 Angle of attack

(49) 200 First controller structure

(50) 204 Angle of attack

(51) 206 Rotor inertia

(52) 208 Rotation speed measurement

(53) 210 Power specification

(54) 212 Power regulation

(55) 214 Nominal blade angle

(56) 216 Pitch system

(57) 218 Wind speed

(58) 220 Rotation speed

(59) 222 Electrical power

(60) 224 Pitch angle

(61) 230 Power

(62) 232 Time

(63) 234 Aerodynamic power

(64) 236 Electrical power

(65) 240 Power

(66) 242 Rotation speed

(67) 244 Power curve

(68) 246 Upper partial load range

(69) 250 Pitch angle

(70) 252 Power

(71) 254 Pitch angle curve

(72) 256 First adjustment gradient

(73) 258 Second adjustment gradient

(74) 260 Nominal pitch angle

(75) 304 Angle of attack

(76) 306 Rotor inertia

(77) 308 Rotation speed measurement

(78) 310 Determination of aerodynamic power

(79) 312 Nominal pitch angle

(80) 314 Pitch system

(81) 316 Wind speed

(82) 318 Rotation speed

(83) 320 Electrical power

(84) 322 Aerodynamic power

(85) 324 Pitch angle