Wind turbine—floating platform assembly and method for orienting said assembly description

Abstract

The invention allows orientation of the platform (1) in order to obtain conditions of maximum efficiency in the wind turbine (16). It comprises first sensors (8) for detecting an effective rotation axis angle (?) formed between the rotation axis (2) and a horizontal plane (24); second sensors (9) for detecting wind direction (23); platform orientation means (11) for modifying the effective rotation axis angle (?); and at least one control unit (12) adapted for receiving a first input (13) from the first sensors (8) and a second input (14) from the second sensors (9) and, based on said inputs (13, 14), transmitting orders to the platform orientation means (11) and yaw mechanism.

Claims

1. A wind turbine-floating platform assembly comprising: a floating platform; an upwind-type wind turbine disposed on the floating platform, the upwind-type wind turbine comprising: a tower fixed to the floating platform, a nacelle disposed on the tower to support a rotor, a yaw mechanism located in the nacelle, the yaw mechanism configured to rotate the nacelle around a longitudinal axis of the tower, and at least two blades located in the rotor, the at least two blades being configured so as to cause a rotation of the rotor around a rotation axis, the rotation axis having a tilt angle, formed between the rotation axis and a plane perpendicular to the longitudinal axis of the tower, non equal to zero; at least one first sensor configured to detect an effective rotation axis angle formed between the rotation axis and a horizontal plane; at least one second sensor configured to detect wind direction; a platform orientation mechanism configured to modify the effective rotation axis angle; and a control unit configured to receive a first input from the at least one first sensor and a second input from the at least one second sensor and transmit instructions to the platform orientation mechanism based on the first input and the second input, as well as transmit instructions to the yaw mechanism based on the second input.

2. The assembly of claim 1, wherein the platform orientation mechanism comprises submerged elements associated with the platform and is configured to modify a position of the submerged elements.

3. The assembly of claim 2, wherein the submerged elements comprise a plurality of floats, and wherein the platform orientation mechanism is further configured to impel air, via conduits, toward a plurality of chambers associated with the plurality of floats.

4. The assembly of claim 3, wherein the plurality of chambers are interconnected via the conduits.

5. The assembly of claim 3, wherein the platform orientation mechanism comprises at least one compressor configured to impel the air.

6. The assembly of claim 1, wherein the at least two blades comprise a limitation mechanism configured to limit a caused rotation of the rotor for wind speeds exceeding a certain threshold value.

7. The assembly of claim 6, wherein the limitation mechanism is configured to cause the at least two blades to rotate with respect to their corresponding longitudinal axis in order to vary a blade surface area exposable to wind.

8. The assembly of claim 1, further comprising at least one third sensor configured to measure a magnitude of at least one of the following: speed of wind incident upon the tower, rotor rotation speed, blade orientation angle with respect to its corresponding longitudinal axis, and instantaneous power generated; wherein the first control unit is further configured to receive a third input from the at least one third sensor and, based at least in part on the third input, transmit the instructions to the platform orientation mechanism.

9. The assembly of claim 1, wherein the control unit comprises: a yaw subunit configured to control the yaw mechanism based on the second input, and an orientation subunit configured to control the platform orientation mechanism based on the first input and second input.

10. A method for orienting a wind turbine-floating platform assembly, the method comprising: receiving a first input via at least one first sensor, the first input being indicative of a rotation angle (?) formed between a horizontal plane and a rotation axis of a rotor, the rotor being supported on a nacelle located on a tower of a wind turbine which is arranged on a floating platform, the rotation axis having a tilt angle (?), formed between the rotation axis and a plane perpendicular to a longitudinal axis of the tower, non equal to zero; communicating the first input to a control unit; receiving a second input via at least one second sensor, the second input being indicative of a wind direction; communicating the second input to the control unit; and causing a variation in ? wherein the absolute value of ? is smaller than ?.

11. The method of claim 10, wherein causing the variation in ? comprises causing the tower to lean windward.

12. The method of claim 11, further comprising: receiving a third input by via at least one third sensor, the third input being indicative of at least one of the following: speed of the wind incident upon the tower, rotor rotation speed, blade orientation angle with respect to their longitudinal axis, and instantaneous power generated; communicating the third input to the control unit; comparing a value of said third input with a previously defined threshold value; and wherein causing the variation in ? comprises causing the variation in ? when the value of the third input does not exceed the threshold value.

13. The method of claim 10, wherein causing the variation in the ? comprises causing the variation in such a manner that the ? has a mean value substantially equal to zero.

14. The method of claim 12, wherein causing the variation in the ? comprises causing the variation in ? based on a difference between a parameter value and the first input value, the parameter value being calculated based on the third input value.

15. A wind turbine-floating platform assembly comprising: a floating platform; an upwind-type wind turbine disposed on the floating platform, the upwind-type wind turbine comprising: a tower fixed to the floating platform, a nacelle disposed on the tower to support a rotor, a yaw mechanism located in the nacelle, the yaw mechanism configured to rotate the nacelle around a longitudinal axis of the tower, and at least two blades located in the rotor, the at least two blades being configured so as to cause a rotation of the rotor around a rotation axis, the rotation axis having a tilt angle, formed between the rotation axis and a plane perpendicular to the longitudinal axis of the tower, non equal to zero; at least one first sensor configured to detect an effective rotation axis angle formed between the rotation axis and a horizontal plane; at least one second sensor configured to detect wind direction; a platform orientation mechanism configured to modify the effective rotation axis angle and a control unit configured to receive a first input from the at least one first sensor and a second input from the at least one second sensor and transmit instructions to the platform orientation mechanism based on the first input and the second input so as to lean the tower windward for compensating the effect of the wind and the tilt angle, as well as transmit instructions to the yaw mechanism based on the second input.

Description

DESCRIPTION OF THE DRAWINGS

(1) In order to complete the description being made and with the object of helping to better understand the features of the invention, in accordance with a preferred embodiment thereof, accompanying said description as an integral part thereof is a set of drawings wherein the following has been represented in an illustrative and non-limiting manner:

(2) FIG. 1.Shows a view of a wind turbine-floating platform assembly not covered by claims.

(3) FIG. 2.Shows a wind turbine-floating platform assembly in accordance with the invention, illustrating the operation of the orientation means.

(4) FIG. 3.Shows a graphic representing the evolution of the effective angle (?) of the rotation axis in accordance with wind speed according to a preferred embodiment of the method of the invention.

(5) FIG. 4.Shows a schematic diagram illustrating the method in accordance with the invention.

(6) FIG. 5.Shows a view of the orientation means according to the first embodiment.

(7) FIG. 6.Shows a schematic view of the operation of the method according to a preferred embodiment.

PREFERRED EMBODIMENTS OF THE INVENTION

(8) The wind turbine (16)floating platform (1) assembly in accordance with the invention shown in FIG. 2 comprises an upwind-type wind turbine (16) disposed on a floating platform (1), where the wind turbine comprises: a tower (3) fixed to the platform (1); a nacelle (4) disposed on the tower (3) for supporting a rotor (6), and having a yaw mechanism (not shown) to orient the rotor (6) windward, said yaw mechanism enabling the nacelle (4) to rotate with respect to the tower (3) around the longitudinal axis of said tower (3); the rotor (6) comprising at least two blades (7) capable of making the rotor (6) rotate around a rotation axis (2) due to the action of the wind incident upon said blades (7), the rotation axis (2) having a tilt angle (?), formed between the rotation axis (2) and a plane perpendicular to the longitudinal axis of the tower (3), non equal to zero.

(9) The assembly additionally comprises: first sensors (8) for detecting an effective angle (?) of the rotation axis, formed between the rotation axis (2) and a horizontal plane (24); second sensors (9) for detecting wind direction (23); orientation means (11) for modifying the effective angle (?) of the rotation axis (2); and limiting means for limiting the power obtained at wind speeds greater than a certain threshold speed, where said limiting means comprise means for controlling blade pitch for enabling said blades (7) to rotate with respect to their longitudinal axis in order to vary the surface area of the blades (7) exposed to the wind.

(10) The assembly additionally includes: third sensors (10) for measuring at least one magnitude selected from among: the speed of the wind incident upon the tower (3), the speed of rotation of the rotor (6), the angle of orientation of the blades (7) with respect to their longitudinal axis and the instantaneous power generated; the control unit (12) being adapted to receive a third input (15), from the third sensors (10) and, based on said inputs (13, 14, 15), transmit orders to the orientation means (11); and a control unit (12) adapted to receive a first input (13), from the first sensors (8) and a second input (14) from the second sensors (9) and, based on said inputs (13, 14), transmit orders to the platform orientation means (11) and to the yaw mechanism.

(11) The orientation means (11), see FIG. 5, comprise active means for controlling the position of the centre of buoyancy by modifying submerged elements, preferably floats (17) linked to the platform (1). In a preferred embodiment, the submerged elements are modified without modifying the distribution of the platform masses. This can be done by modifying the submerged part of the floats (17) or, alternatively, by modifying the amount of air confined in a lower chamber (18) of said floats (17). In particular, in a previously explained preferred embodiment of the second alternative, the orientation means (11) comprise: a plurality of floats (17) disposed on the lower part of the platform (1); chambers (18) disposed on the lower part of the floats (17); impulsion means (20) for impelling air to the chambers (18) through conduits (19), thereby modifying the amount of air confined within said chambers and the water surface (22), where the conduits (19) interconnect the plurality of chambers (18). The impulsion means (20) comprise at least one compressor (20).

(12) In accordance with a first embodiment of the invention, a method is presented for orienting the assembly of the invention which comprises the following steps, as shown in FIG. 4: capturing the first input (13) by means of the first sensors (8); communicating the first input (13) to the control unit (12); capturing the second input (14) by means of the second sensors (9); communicating said second input (14) to the control unit (12); and ordering the orientation means (11), through the control unit (12), to orient the platform (1) based on the first input (13) and the second input (14), in such a manner that the effective rotation axis angle (2) is, in absolute value, smaller than the tilt angle (?).

(13) In accordance with a second embodiment, the method of the invention comprises the additional steps of: capturing a third input (15) by means of the third sensors (10); communicating said third input (15) to the control unit (12); and comparing the value of the third input (15) to the previously defined threshold value and, when the condition that the value of the third input (15) does not exceed the threshold value is fulfilled, ordering the orientation means to orient the platform in accordance with the first input (13), the second input (14) and the third input (15).

(14) In a third preferred embodiment of the invention, a third input signal is used for controlling leaning, said signal being selected from among the following: wind speed, rotor rotation speed, electricity generated or blade pitch angle.

(15) Control of the angle of blade pitch towards feathered position to control rotor rotation speed within the rated wind range is typical in wind turbines. The variation in blade pitch angle limits wind energy capture as of the moment in which the wind turbine reaches its rated rotation speed and power limits. In this case, when the third input (15), which provides a wind speed value, or blade pitch or rated power or rotor rotation regime value, reaches a predetermined threshold value, the control unit (12) does not transmit instructions to the orientation means (11), allowing the tower (3) to adopt a leeward leaning given by the force of the wind, and allowing the limiting means to control the power generated.

(16) This situation does not increase the moment at the base of the tower or the fatigue loads produced by said moment. Fatigue loads are the result of the magnitude of the force and occurrence thereof. In a system with control over the angle of blade pitch towards feathered position, the driving force of the wind decreases when said pitch control becomes activated and strong wind occurrence is low.

(17) In accordance with a preferred embodiment, the effective angle (?) of the rotation axis (2) depends on the third input, in particular, on a series of speed wind values, as explained below.

(18) FIG. 3 shows how, based on a wind speed threshold (Vv-off), the orientation means (11) stop receiving instructions and, for wind speeds greater than said speed Vv-off, the resulting effective rotation axis angle (?) evolves freely, firstly increasing and then decreasing, due to the fact that the driving force of the wind decreases upon activation of blade pitch control.

(19) In a transition zone between a reference value (Vv-t) and Vv-off, the effective angle (?) increases gradually (or ramps up), in such a manner that at Vv-off speed it reaches the ?-off value or deactivation angle. Said value is that in which the wind turbine generates rated power with a wind speed equal to Vv-off and a blade pitch angle equal to ?-off. Vv-2 speed marks the wind speed at which the rated power is reached, where control of blade pitch towards feathered position preferably becomes activated. Said Vv-2 speed is comprised within the range [Vv-t, Vv-off], capable of adopting any value. At Vv-off speed a blade pitch angle threshold is reached (?-off) which alternatively determines that the orientation means (11) stop receiving instructions.

(20) Within a range of wind speeds comprised between the Vv-cut-in and Vv-t, the resulting angle (?) has a mean value approximately equal to zero.

(21) Table 2 below shows a simplified diagram illustrating the foregoing. Vv-med represents the wind speed value.

(22) TABLE-US-00002 TABLE 2 Relationship between angle ? and wind speed Vv-med. Vv_med ? Vv-cut-in < Vv-med < Vv-t 0 Vv-t <= Vv-med < Vv-off <0 Vv-med > Vv-off The orientation means do not receive instructions

(23) In this manner, the evolution of the effective rotation axis angle is controlled upon actuation of the orientation means of the platform in a convenient manner, in such a manner that: the effective rotation axis angle is substantially equal to the angle of maximum efficiency with light and moderate winds (less than Vv-t), maximising production; the effective rotation axis angle evolves freely under strong winds (greater than Vv-off) where wind energy is greater than that which the wind turbine can transform into electrical power, reducing the loads on the wind turbine and the actuation of the blade pitch regulation mechanism, as well as the actuation of the platform orientation mechanism; the effective rotation axis angle evolves gradually from the angle of maximum efficiency to the deactivation angle, in such a manner as to avoid sudden transitions.

(24) FIG. 6 shows that when the orientation means are activated, i.e. for wind speeds of less than Vv-off, the control unit orders activation of the orientation means (11) based on the difference between a parameter value (?ref) and the leaning value (?med) of the rotation axis (2) detected by the first sensors (8). Based on said difference and using a regulator or any equivalent means known in the state of the art, the order (Y) is calculated and transmitted to the orientation means. Said parameter value (?ref) is calculated based on the wind speed (Vv-med) measured by the third sensors (10) using a predefined function or table of values.