CONTROLLER AND CONTROL METHOD FOR A WIND TURBINE

Abstract

A controller structure for a wind turbine having an aerodynamic rotor with at least one rotor blade, wherein the controller structure is designed to control a rotation speed of the rotor of the wind turbine, wherein the controller structure is designed as a cascade control arrangement and has an outer control loop and an inner control loop, wherein the inner control loop receives an input signal which comprises a change in the rotation speed, an acceleration of the rotation speed, a function of the change in the rotation speed and/or a function of the acceleration of the rotation speed.

Claims

1. A controller for a wind turbine having an aerodynamic rotor with at least one rotor blade, the controller comprising: circuitry forming a cascade control arrangement and having an outer control loop and an inner control loop, wherein the controller is configured to control a rotation speed of the aerodynamic rotor of the wind turbine, wherein the inner control loop is configured to receive one or more input signals indicative of one or more characteristics chose from a change in the rotation speed, an acceleration of the rotation speed, a function of a change in the rotation speed and a function of an acceleration of the rotation speed.

2. The controller as claimed in claim 1, wherein a controlled variable of the outer control loop is provided as a reference variable of the inner control loop.

3. The controller as claimed in claim 2, wherein the outer control loop is configured to limit a target value of the inner control loop, wherein the target value is at least one value chose among a change in the rotation speed, the acceleration of the rotation speed, the function of the change in the rotation speed, and the function of the acceleration of the rotation speed.

4. The controller as claimed in claim 1, wherein: the one or more input signals received by the inner control loop comprises a rotor acceleration power or a rotor acceleration torque, and the rotor acceleration power or the rotor acceleration torque describes a portion of a power or torque received by the aerodynamic rotor of the wind turbine that is converted into an acceleration of the aerodynamic rotor.

5. The controller as claimed in claim 1, wherein: the one or more input signals received by the inner control loop comprises an aerodynamic power received by the aerodynamic rotor, the aerodynamic power comprises a sum of a rotor acceleration power and a generator power of a generator of the wind turbine, and the rotor acceleration power describes a portion of a power received by the aerodynamic rotor of the wind turbine that is converted into an acceleration of the aerodynamic rotor.

6. The controller as claimed in claim 1, wherein the outer control loop determines a deviation of an actual rotation speed of the aerodynamic rotor from a target rotation speed of the aerodynamic rotor as a system deviation.

7. The controller as claimed in claim 1, wherein the outer control loop generates a target value of a power or of a torque as manipulated variable.

8. The controller as claimed in claim 7, wherein the target value of the power is limited by an upper limit and a lower limit.

9. The controller as claimed in claim 8, wherein the target value of the power is asymmetrically limited by the upper limit and the lower limit.

10. The controller as claimed in claim 7, wherein the power comprises a rotor acceleration power, wherein the rotor acceleration power is limited to a rated power of the wind turbine, wherein the rotor acceleration power is 20% of the rated power of the wind turbine or less.

11. The controller as claimed in claim 7, wherein the power comprises an aerodynamic rotor power, wherein the aerodynamic rotor power is limited to twice a rated power of the wind turbine.

12. The controller as claimed in claim 1, wherein the inner control loop generates, as manipulated variable, a pitch angle or a rate of change in a pitch angle of at least one of the rotor blades of the aerodynamic rotor.

13. The controller as claimed in claim 12, wherein the target value for the rate of change in the pitch angle is limited to a value of between −18°/second and 18°/second.

14. The controller as claimed in claim 1, wherein at least one control loop chosen from the outer control loop and the inner control loop forms a Proportional (P) controller or a Proportional and Integral (PI) controller.

15. The controller structure as claimed in claim 1, further comprising a calculation circuitry configured to determine a rotor acceleration power from a change in a measured actual rotation speed of the wind turbine using an inertia of the aerodynamic rotor.

16. The controller as claimed in claim 1, further comprising a pilot control arrangement for pilot control of a pitch angle of the at least one rotor blade, wherein the pilot control arrangement is configured to prespecify, parallel to the inner control loop, at least one characteristic chose among a pitch angle and a rate of change in the pitch angle.

17. A method comprising: operating a wind turbine having an aerodynamic rotor with at least one rotor blade, wherein the operating comprises controlling a rotation speed of the rotor of the wind turbine, wherein the controlling comprises using a cascade control arrangement having an outer control loop and an inner control loop, wherein the controlling comprising: acquiring, by the inner control loop, an input signal indicative of one or more characteristics chosen from a change in the rotation speed, an acceleration of the rotation speed, a function of a change in the rotation speed and a function of an acceleration of the rotation speed.

18. A wind turbine comprising the controller as claimed in claim 1.

19. A wind farm comprising a plurality of wind turbines as claimed in claim 18.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0033] Further advantages and exemplary embodiments are described below with reference to the appended figures, in which:

[0034] FIG. 1 shows, schematically and by way of example, a wind turbine,

[0035] FIG. 2 shows, schematically and by way of example, a controller for rotation speed controllers of wind turbines, and

[0036] FIG. 3 shows, schematically and by way of example, a controller.

DETAILED DESCRIPTION

[0037] FIG. 1 shows a schematic representation of a wind turbine according to the invention. 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 and a spinner 110 is provided on the nacelle 104. During operation of the wind turbine, the aerodynamic rotor 106 is set in a rotational motion by the wind, and therefore also turns an electrodynamic rotor of a generator that is directly or indirectly coupled to the aerodynamic rotor 106. The electrical generator is arranged in the nacelle 104 and generates electrical energy. The pitch angles of the rotor blades 108 can be changed by pitch motors at the rotor blade roots of the respective rotor blades 108.

[0038] FIG. 3 shows, schematically and by way of example, a controller 300 for a wind turbine 100, as is shown in FIG. 1 for example. The controller 300 includes circuitry that is designed as a cascade control arrangement and has an outer control loop 310 and an inner control loop 350. The controller 300 controls a rotation speed in the wind turbine to a target value N.sub.target. To this end, the outer control loop 310 compares the actual rotation speed N.sub.actual with a target rotation speed N.sub.target to be established and generates a target value 340 for the rotor acceleration power P.sub.acceleration_target by means of a signal, limited by a limiter 330, of a P controller 320.

[0039] The inner control loop 350 now performs control to the rotor acceleration power P.sub.acceleration and accordingly attempts to set the rotor blades of the wind turbine 100 in such a way that the rotor 106 accelerates as little as possible. To this end, an actual acceleration power P.sub.acceleration is determined by means of a calculation component 380 (or circuitry), for example on the basis of the the change in the rotor rotation speed with respect to time dN.sub.actual/dt by a calculation component 380. The difference between the target value 340 of the acceleration power P.sub.acceleration_target and the ascertained actual value P.sub.acceleration is converted by a P controller 360 into a pitch rate to be set or a blade angle, to be set, of the rotor blades 108. The pitch rate to be set or the pitch angle to be set is limited by a limiter 370 and is then passed as target value 390 to the control arrangement of the wind turbine 100.

[0040] In this example, the calculation component 380 employs known physical relationships between the moment of inertia J known for the rotor, a torque M and rotation speed or angular velocity ω derived therefrom in order to calculate the actual acceleration power P.sub.acceleration from the change in the rotation speed.

[0041] Instead of the rotor acceleration power, as is described in the exemplary embodiment, it is also possible to use all of the aerodynamic power received by the rotor, that is to say with additional consideration of the power received by the generator. One advantage of the rotor acceleration power is, in many cases, that the variable is often usually already available for wind estimators used in control of wind turbines 100, that is to say extensive adaptation of the control of the wind turbine 100 is not required. Accordingly, it suffices merely to replace the known rotation speed controller with a controller 300. Wind estimators are known, for example, from the German patent publication DE 10 2017 105 165 A1.

[0042] As an alternative to powers, the controller 300 presented by way of example can also be implemented with torques or rotation speeds derived with respect to time. These solutions are identical apart from the aspect that the current rotation speed is included in the acceleration power. However, the way in which powers are converted into torques, and vice versa, is already sufficiently known.

[0043] The inner control loop 350 would alone lead to severe rotation speed errors over time, and therefore the outer control loop 310, which reacts considerably more slowly and sluggishly, generates a target value, which can deviate from 0 kW, for the acceleration power. If, for example, an excessive rotation speed situation prevails, that is to say that the actual rotation speed N.sub.actual is greater than the target rotation speed N.sub.target, the target value 340 would be, for example, −200 kW. In this case, the inner control loop 350 would establish an approximate rotor acceleration power P.sub.acceleration of −200 kW, so that the rotation speed of the rotor 106 is reduced as a result.

[0044] Limiting the output of the rotation speed controller by the limiter 330 or 370 allows the maximum acceleration power to be restricted, this likewise having a load-reducing effect.

[0045] The controller 300 schematically shown in FIG. 3 can be particularly advantageously supplemented with a pilot control arrangement arranged parallel to the inner control loop 350. The pilot control arrangement can perform pilot control, for example, on impending gusts and accordingly actively intervene in pitch angle adjustment in addition to the control. Therefore, extreme loads that occur, as are the result of strong gusts, can be particularly effectively avoided.

[0046] In summary, the controller 300 is for controlling the rotation speed to a rotation speed target value N.sub.target. The inner control loop 350 receives the aerodynamic power received by the rotor 106 or the acceleration power or, in simplified terms, also merely the rotor acceleration as controlled variable, wherein the pitch rate or, as an alternative, also a target rotor blade angle serves as manipulated variable. The outer control loop 310 controls, as controlled variable, the rotor rotation speed N, wherein a target value of the aerodynamic power, of the acceleration power or else of the target rotor acceleration are generated as manipulated variable for the inner control loop 350.