Method and system for extracting inertial energy from a wind turbine

p00001Procedure and system for inertial energy extraction r of a wind turbine

p00002The present invention described relates, in general, to the operation of a wind turbine and, more specifically, to the extraction of inertial energy from a wind turbine after releasing a reduction of power from the wind turbine.

p00003In WO 2008/131775 the speed is temporarily increased due to the weakening of the field generator at high wind speeds.

p00004Wind turbines use wind energy to produce electrical energy. Wind turbines typically include a rotor that has multiple blades that transform wind energy into a rotating shaft of a drive shaft, which in turn is used to drive a rotor of an electric generator to produce electrical energy. A plurality of wind turbines can be grouped, sometimes called as a "wind farm."

p00005To mitigate the problems associated with the turbine load, the supply of energy to the network and / or in certain planning conditions (for example, planned maintenance activities), it may be necessary to reduce the production of energy in part or all of the turbines in a wind farm, also called "reduction of wind turbine power". During a power reduction of the wind turbine a power level generated by the turbine is controlled (ie reduced to a power reduction level). Typically, during a wind turbine power reduction, a pitch angle of the rotor blades is adjusted to reduce the rotor rotation speed, which reduces the power output of the wind turbine. For example, during a reduction in power of the wind turbine, the wind turbine can be configured to supply forty percent (40%) of a maximum level of electrical energy capable of being produced by the wind turbine. During a reduction of wind turbine power, wind speeds may be such that it would be possible to produce the maximum level of electrical energy capable of being produced by the wind turbine, however, less energy is generated for other reasons. In other bras, the aerodynamic energy present in the wind is not captured on purpose and, therefore, is wasted.

p00006In one aspect according to the present invention, a system for operating a wind turbine during a power reduction operation is provided. The wind turbine includes a generator and a wind turbine rotor that has at least one rotor blade. The wind turbine also includes a drive train that includes at least one shaft coupled to the wind turbine rotor and configured to drive the generator. The system includes a control system configured to increase a rotation speed of the wind turbine rotor beyond an optimum nominal speed during the wind turbine power reduction operation, and an extraction device configured to extract inertial energy stored in the drive train in case of release of the power reduction operation.

p00007Various aspects and embodiments of the present invention will now be described in connection with the accompanying drawings, in which:

p00008Figure 1 is a perspective view of an example wind turbine.

p00009Figure 2 is a partially sectioned perspective view of a portion of the wind turbine shown in Figure 1.

p00010Figure 3 is a flow chart of an example procedure for the extraction of inertial energy from a wind turbine.

p00011Figure 4 is a graph of example rotor speeds and the corresponding energy generated over time.

p00012Figure 5 is a graph illustrating the changes in a generator speed over a period of time.

p00013Figure 6 is a graph illustrating the changes in an output power of the generator over the period of time also shown in Figure 5.

p00014Figure 7 is a graph that illustrates changes in a generator output power level over the period of time shown in Figure 5.

p00015As used herein, the term "shovel" is intended to be representative of any device that provides reactive force when it is in motion relative to a surrounding fluid. As used herein, the term "wind turbine" is intended to be representative of any device that generates rotation energy from wind energy and, more specifically, that converts the kinetic energy of wind into mechanical energy. As used herein, the term "wind generator" is intended to be representative of any wind turbine that generates electrical energy from rotating energy generated from energy.

p00017of wind and, more specifically, to convert the mechanical energy converted from the kinetic energy of the wind into electrical energy.

p00018Several technical effects of some of the systems, procedures and apparatus described in this document include at least one of (a) configuring a control system to adjust the operation of the wind turbine to facilitate the increase of a rotor speed of a rotor during wind turbine power reduction, and (b) configure an extraction device to extract inertia energy stored in a wind turbine drive train under the release of the power reduction.

p00019Figure 1 is a perspective view of an example wind turbine 10. Figure 2 is a partially sectioned perspective view of a portion of the wind turbine 10. The wind turbine 10 described and shown in this document is configured to generate electrical energy from wind energy. On the other hand, the wind turbine 10 described and shown in this document includes a horizontal axis configuration. However, in some embodiments, the wind turbine 10 may include, in addition to or as an alternative to the horizontal axis configuration, a vertical axis configuration (not shown). The wind turbine 10 can be coupled to an electric load (not shown), such as, but not limited to, an electric power network (not shown), for the reception of electric power from it to drive the operation of the wind turbine 10 and / or associated components and / or for the supply of electric power generated by the wind turbine 10 thereto. Although only one wind turbine 10 is shown in Figures 1 and 2, in some embodiments, a plurality of wind turbines 10 can be grouped together to form a wind farm.

p00020The wind turbine 10 includes a body 12, sometimes referred to as a "gondola", and a rotor (generally designated by 14) coupled to the body 12 for rotation relative to the body 12 about an axis of rotation

p0002116. In the exemplary embodiment, the body 12 is mounted on a tower 18 extending from a base 20. However, in some embodiments, in addition to or as an alternative to the body 12 mounted on the tower, the wind turbine 10 includes a body 12 adjacent to the ground and / or a water surface. The height of the tower 18 can be any suitable height that allows the wind turbine 10 to function as described herein. The rotor 14 includes a hub 22 and a plurality of blades 24 (sometimes called "aerodynamic profiles") that extend radially outward from the hub 22 to convert wind energy into rotational energy. Although rotor 14 is described and shown herein as having three blades 24, rotor 14 may have any suitable number of blades 24. Each blade 24 may have any suitable length that allows the wind turbine 10 to function as described herein. For example, in some embodiments, one or more blades 24 are approximately half a meter long, while in some embodiments one or more blades 24 are about fifty meters long. Other examples of lengths of the blades 24 include ten meters or less, approximately twenty meters, approximately thirty-seven meters, and approximately forty meters. Other examples include rotor blades between about fifty meters and a hundred meters long.

p00022Despite how the blades 24 are shown in Figure 1, the rotor 14 can have blades 24 in any suitable way, and can have blades 24 of any type and / or any configuration, if such shape, type and / or configuration It is described and / or shown in this document. An example of another type, shape and / or configuration of the blades 24 is a duct rotor (not shown) having a turbine (not shown) contained within a duct (not shown). Another example of another type, shape and / or configuration of the blades 24 is included within a Darrieus wind turbine, sometimes referred to as an "egg mixer" turbine. However, another example of another type, shape and / or configuration of the blades 24 is included within a Savonious wind turbine. A further example of another type, shape and / or configuration of the blades 24 is included within a traditional windmill for pumping water, such as, but not limited to, four-blade rotors that have wooden shutters and / or sails of cloth. On the other hand, the wind turbine 10 can be, in some embodiments, a wind turbine that has a rotor 14 that is generally facing the wind to take advantage of the wind energy, and / or can be a wind turbine that has a rotor 14 which, in general, is facing the wind direction to harness energy. Of course, in any embodiment, the rotor 14 may not be exactly facing the wind and / or in favor of the wind, but may generally be facing at any angle (which may be variable) relative to a wind direction to take advantage of the energy of the same.

p00023Referring now to FIG. 2, the wind turbine 10 includes an electric generator 26 coupled to the rotor 14 to generate electric power from the rotational energy generated by the rotor 14. The generator 26 can be any suitable type of electric generator, such as, but not limited to, a winding rotor induction generator, such as a doubly fed induction generator. The generator 26 includes a stator (not shown) and a rotor (not shown). The rotor 14 includes a main rotor shaft 28 (also called a "low speed shaft") coupled to the hub 22 for rotation therewith. The generator 26 is coupled to the main rotor shaft 28 such that the rotation of the main rotor shaft 28 drives the rotation of the generator rotor, and therefore, the operation of the generator 26. In the exemplary embodiment, the generator rotor has a rotor shaft 30 (also called a "high speed shaft") coupled thereto and coupled to the main rotor shaft 28 through a gearbox 32. In other embodiments, The generator rotor is directly coupled to the main rotor shaft 28, sometimes referred to as a "direct drive wind turbine".

p00024In some embodiments, one or more processors (not shown in Figure 2) within a control panel 34 form a control system 36 that is used for general monitoring and control of the system, including the

p00026step and speed regulation, the application of the high-speed shaft and the brake to the turn, the application to the turn and the motor pump and the monitoring of the power level and faults. Alternative distributed or centralized control architectures can be used in some embodiments. The term processor, as used herein, refers to central processing units, microprocessors, microcontrollers, reduced instruction set circuits (RISC), application specific integrated circuits (ASICs), logic circuits, and any other capable circuit or processor of executing the functions described in this document.

p00027In various embodiments, the control system 36 provides control signals to an actuator 38 of the pitch of the variable blade to control the passage of the blades 24 that drive the hub 22 as a result of wind. The hub 22 and the blades 24 together form the rotor 14 of the wind turbine. A drive train 40 of the wind turbine 10 includes the main rotor shaft 28, connected to the hub 22 and the gearbox 32 which, in some embodiments, uses a double path geometry to drive the high speed shaft 30 enclosed within the gearbox 32. The high speed shaft 30 is used to drive the generator 26 which is supported by a main frame 42. Another suitable type of generator, by way of non-limiting example, is a multi-pole generator that can operate at the speed of the main rotor shaft 28 in a direct drive configuration, without the need for a gearbox 32.

p00028The torque of the rotor 14 drives the generator rotor to thereby generate AC power of variable frequency from the rotation of the rotor 14. The generator 26 has a pair of the air gap between the generator rotor and the stator that opposes to rotor torque 14. A frequency converter 44 is coupled to the generator 26 for the conversion of the variable frequency AC to a fixed frequency AC for supply to an electric load (not shown in Figure 2), such as, but not limited to, a mains connected to the generator 26. The frequency converter 44 can be placed anywhere inside or away from the wind turbine 10. For example, in the exemplary embodiment, the frequency converter 44 is placed inside the base 20 of the tower

p0002918.

p00030In some embodiments, the wind turbine 10 may include a rotor speed limiter, for example, but not limited to, a disc brake 46. The disc brake 46 slows the rotation of the rotor 14 to, for example, slow down the Rotation of the rotor 14, the brake rotor 14 against the total wind torque, and / or reduce the generation of electrical energy from the electric generator 26. In addition, in some embodiments, the wind turbine 10 may include a turning system 48 for the rotation of the body 12 about a rotation axis 50 to change a rotation of the rotor 14, and more specifically, to change a direction of orientation of the rotor 14 to, for example, adjust an angle between the orientation direction of the rotor 14 and a wind direction.

p00031Figure 3 is a flow chart 60 illustrating an example procedure for the operation of a wind turbine, for example, wind turbine 10 (shown in Figure 2) during power reduction of wind turbine 10. More specifically , the flow chart 60 illustrates an example procedure for the inertial energy extraction of, for example, the wind turbine 10. The procedure includes monitoring 70 of the operation of the wind turbine. For example, the power generation and energy demand of the network can be monitored 70, locally and / or remotely from the wind turbine 10. In some examples, the control system 36 (shown in the figure 2) It is configured to monitor 70 power generation and network power demand. The procedure may also include initiation 72 of a power reduction of the wind turbine 10 in the event of a power reduction event. By initiating 72 of the power reduction of the wind turbine 10, an output of the power level of the wind turbine 10 is reduced. Typically, the power reduction is initiated 72 by adjusting a blade pitch of the blades of the rotor, for example, the rotor blades 24 (shown in Figure 2). The pitch of the blades is adjusted to reduce a rotational speed of the rotor, for example, the rotor 14 (shown in Figure 2). By reducing the rotational speed of the rotor 14, the output power is reduced by the wind turbine 10.

p00032In the exemplary embodiment, instead of the power reduction of the rotational speed of the rotor 14, the start 72 of the power reduction of the wind turbine 10 includes a power reduction of the torque demand in the generator 26. More specifically, a frequency converter, for example, the frequency converter 44 (shown in Figure 2) is configured to reduce the torque demand in the generator 26 at the start of the power reduction. By reducing the power of the torque demand in the generator 26, the energy output is reduced by the wind turbine 10, for example, to a level of power reduction.

p00033As described above, the procedure includes initiating 72 the power reduction of the wind turbine 10 when a power reduction event occurs. The power reduction event may include the generation of energy exceeding the power demand of the power supply network, the generation of energy exceeding a stored power reduction energy level, and / or a demand time period of low energy Alternatively, the power reduction can follow a power reduction schedule. For example, it can be determined that during periods of peak electricity usage, a power grid is capable of offering a level of energy generated by the wind turbine10 that is 80% of a maximum possible energy that is capable of generating the wind turbine 10. During periods that are not peak, the power supply network may only be able to offer a level of energy generated by wind turbine 10 which is 50% of the maximum possible is capable of generating wind turbine 10. Power reduction facilitates the provision to the power supply network of a level of energy that the power supply network is capable of supplying.

p00035In the exemplary embodiment, the method also includes facilitating an increase in a rotor speed during the wind turbine power reduction. More specifically, the control system 36 is configured to adjust a pitch angle of one or more of the blades 24, for example, by controlling the variable pitch drive 38 of the blades (shown in Figure 2). Adjusting the pitch angle of the rotor blades 24 facilitates the increase in the rotational speed of the rotor 14 during the power reduction of the wind turbine 10. In the exemplary embodiment, the torque demand in the generator 26 is reduced , maintaining the output power of the wind turbine 10 at or below the power reduction level, while increasing the rotational speed of the rotor 14. As described above, typically, during power reduction, the blades 24 are positioned such that the wind passes over the blades 24, thereby minimizing the effect that the wind has on the blades 24 and reducing the speed of rotation of the rotor 14. In contrast, in the exemplary embodiment, the method includes adjusting the operation of the wind turbine 10 to facilitate the increase in the rotational speed of the rotor 14 during the power reduction above an optimum nominal speed for a curve of torque In an alternative embodiment, the control system 36 is configured to adjust a turning angle of the body 12 (shown in Figure 2) by controlling the turning system 48 (shown in Figure 2). The control system 36 may be configured to adjust the pitch angle of the blades 24 and / or a groove angle of the body 12, such that the rotor speed may increase above the optimum nominal speed for the curve of torque, but does not increase more than a predetermined maximum nominal rotor speed. The predetermined maximum nominal speed of the rotor facilitates the prevention or minimization of damage to the wind turbine 10 due to a speeding condition. The adjustment of the operation of the wind turbine 10 facilitates the capture of aerodynamic energy in the air (for example, which would have been lost due to the reduction of power) and the storage of aerodynamic energy in the form of inertial energy in the rotation of the drive train 40 of the wind turbine 10.

p00036In the exemplary embodiment, the process also includes release 76 of the wind turbine power reduction. In the exemplary embodiment, the control system 36 determines when to release the power reduction 76 based, at least partially, on the generation of monitored energy 70 and the demand of the power supply network. Alternatively, the control system 36 determines when to release the power reduction based, at least partially, on a power reduction schedule. Although described as being determined by the control system 36, a determination as to releasing 76 the power reduction can also be made by a centralized wind farm controller (not shown in Figure 3) or by any other suitable device. The release 76 of the wind turbine power reduction includes the wind turbine adjustment operation 10 to allow the power output of the wind turbine 10 to be increased to a power level greater than the power reduction level. For example, you can adjust the pitch of the blades, the angle of grinding, and / or the torque demand of the generator 26.

p00037In the exemplary embodiment, the method also includes extracting the inertial energy 78 stored in the drive train 40 in case of release 76 of the power reduction. In the exemplary embodiment, an extraction device is configured to extract the inertial energy 78 stored in the drive train 40. A frequency converter, for example, the frequency converter 44 (shown in Figure 2) may be configured to extract the inertial energy 78 stored in the drive train 40 in case of release 76 of the power reduction. Although described herein as a frequency converter, the extraction device may be any device that allows the wind turbine 10 to function as described herein. To extract the inertial energy 78 stored in the drive train 40, the frequency converter 44 may be configured to increase a torque demand in the generator 26 after the release of the wind turbine power reduction. The increase in torque demand in the generator 26 facilitates the conversion of the inertial energy stored in the drive train 40 of the wind turbine 10 into electrical energy for supply to a supply network. More specifically, to increase the torque demand in the generator 26, the frequency converter 44 may be configured to adjust a generator phase 26 to increase the generator torque.

p00038Figure 4 is a graph 80 of speeds of the example rotor (n) 82 and the corresponding power generated (P) 84 by, for example, the generator 26 (shown in Figure 2) over time (t ). For example, the generated power 84 can be measured in kilowatts (kW), the rotor speeds 82 can be measured in radians per second (rad / s), and the time can be measured in seconds (s). In the exemplary embodiment, a power reduction level 90 is predetermined to be X% of a maximum power capable of being generated, for example, by wind turbine 10 (shown in Figure 1). In the exemplary embodiment, at first 92, the rotor speed 82 increases to a level where the generated power 84 rises above the power reduction level 90. In the exemplary embodiment, in order for the power generation 84 to remain at or below the power reduction level 90, a torque demand in the generator 26 is reduced. In the exemplary embodiment, the rotor speed 82 is lets rise above the power reduction level 90, for example, at a time 94. For example, the control system 36 is configured to adjust the pitch of the blades 24 (shown in Figure 2) such that the speed 82 of the rotor increases beyond the power reduction level 90, but does not increase beyond a maximum power rotor speed. By actively facilitating this increase in rotor speed 82, wind aerodynamic energy is captured as inertial energy, which is stored in the drive train 40 (i.e., the rotating components) of the wind turbine 10.

p00039In the exemplary embodiment, when the rotor speed 82 decreases, for example, due to the reduction of the

p00041wind speed, the adjustment of the pitch of the blades, and / or the adjustment of the angle of güiñada, the power generated 84 is reduced below the power reduction level 90 at the time 96. In the example embodiment, in the moment 96, the power reduction is released. Furthermore, at the moment 96, a signal is provided to, or generated by, for example, the control system 36, indicating a desire to have more output power. The signal can be generated automatically by the control system 36 (for example, under the power reduction of the generated power 84 below the power reduction level 90) and / or can be provided manually by an operator of the wind turbine 10 In the exemplary embodiment, the control system 36 provides an extraction device, for example, the frequency converter 44 (shown in Figure 2) with an increase in the value of the torque demand. The increased torque demand value causes the frequency converter 44 to change the excitation of the generator 26, which causes the generated power 84 to increase to a generated power 98. Increasing the torque demand value facilitates the conversion of the inertial energy stored in the rotating components of the wind turbine 10 in electrical power for supply to the power supply network. The additional electrical power converted from the inertial energy is illustrated in Figure 4 in the shaded area 100 and in the shaded area 102. For example, at time 104, without capturing the inertial energy, the generated energy 84 would be in a power level 106. Power level 106 is obtained only by converting the wind energy currently available into rotating energy by means of blades 24. In contrast, at the moment 104, the generated power 98 is a power level 108 generated by the conversion of the inertial energy stored in electrical power, in addition to the conversion of the wind energy currently available into electrical power.

p00042Figure 5 is a graph 120 illustrating the changes in a generator speed 122, measured in revolutions per minute (rpm), over a period of time 124, measured in seconds (s). Figure 6 is a graph 130 illustrating the changes in an output power 132 of the generator, measured in kilowatts (kW), over a period of time 124. Figure 7 is a graph 140 illustrating the changes in a generator output energy level 142, measured in kilowatt-seconds (kWs), over time period 124. Figures 5 to 7 are illustrative of the behavior of a wind turbine generator, for example, generator 26 (shown in Figure 2) of wind turbine 10 (shown in Figure 2). In the illustrated example, a substantially constant generator speed 122 from a moment 148 to a moment 150 produces an output power 132 of the substantially constant generator. Between moment 148 and moment 150, generator 26 and rotor 14 are in equilibrium. In the illustrated example, at the moment 150 a signal is provided to, or generated by, for example, the control system 36, indicating a desire to have more output power 132. The signal can be generated automatically by the control system 36 (for example, in the power reduction of the output power 132 below a power reduction level, for example, at the moment 96 (shown in the figure 4)) and / or can be provided manually by an operator of the wind turbine 10. In the exemplary embodiment, the control system 36 provides an extraction device, for example, the frequency converter 44 (shown in Figure 2), with a signal that directs the frequency converter 44 to extract the inertial energy stored in the drive train 40. For example, the control system 36 can provide the frequency converter 44 with an increase in the value of the torque demand. The increased torque demand value causes the frequency converter 44 to change the excitation of the generator 26, which causes the increase in output power 132 shown between the moment 150 and the moment 152. The frequency converter 44 it applies more torque to the generator 26 which is applied to the rotor 14 by wind, which causes the rotor speed, and therefore the speed 122 of the generator 122, to decrease after the moment 150.

p00043Although the speed 122 of the generator decreases after moment 150, the output power 132 of the generator increases due to the release of the inertial energy stored in drive train 40 of the wind turbine 10. At time 152, the power output 132 of the generator reaches maximum power and begins to decrease as stored inertial energy is converted into electrical energy (i.e., output power 132). In addition, at a time 154 the inertial energy stored in the drive train 40 of the wind turbine 10 is dissipated. After the moment 154, the output power 132 of the generator is only generated from aerodynamic energy captured by the wind blades 24 .

p00044Example procedures and systems for extracting inertial energy from a wind turbine are described in this document. More specifically, the procedures and systems described in this document allow the active storage of inertial energy during the power reduction operation of a wind turbine, and the conversion of inertial energy into electrical power by releasing the power reduction operation. The procedures and systems described in this document facilitate the generation of electrical power from inertial energy, in addition to the captured aerodynamic energy, during a wind speed drop.

p00045Several of the procedures and systems described in this document facilitate an efficient and economical operation of a wind turbine. Examples of performance of the procedures and systems are described and / or shown in this document in detail. The procedures and systems are not limited to the specific embodiments described in this document, but rather, the components of each system, as well as the steps of the procedures, can be used independently and separately from other components and stages described in this document. Each component, and each procedure stage, can also be used in combination with other components and / or process steps. Although described herein in the context of a wind turbine, the procedures and systems described herein can be applied to, for example, without limitation, power plants that include hydroelectric turbines or steam turbines.

p00046When elements / components / etc are introduced. of the procedures and systems described and / or illustrated in this document, the articles "a", "a", "the" and "said" are intended to mean that there is one or more of the element (s) / component (s) / etc . The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be element (s) / component (s) / etc. additional different from

p000475 element (s) / component (s) / etc. indicated.

p00048The present description uses examples to disclose the invention, including the preferred mode, and also to allow any person skilled in the art to practice the invention, including the realization and use of devices or systems and the performance of any of the procedures. incorporated. The patentable scope of the invention is defined in the claims, and may include other examples that are produced by

p0004910 subject matter experts Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with non-substantial differences from the literal language of the claims.