Patent Application
20140203560
The present disclosure relates generally to wind turbines, and more particularly to methods and apparatus for adjusting pitch angles of rotor blades in wind turbines.
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and a rotor including one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
During operation of a wind turbine, various components of the wind turbine are subjected to various loads due to the aerodynamic wind loads acting on the blade. In particular, the rotor blades experience significant loading, and frequent changes in loading, during operation due to interaction with the wind. Changes in wind speed and direction, for example, may modify the loads experienced by the rotor blades. To reduce rotor blade loading, various methods and apparatus have been developed to enable pitching of the rotor blades during operation. Pitching generally allows the rotor blades to shed a portion of the loads experienced thereby.
Such methods and apparatus for pitching rotor blades typically utilized controllers which determine appropriate pitch angles for the rotor blades based on operating conditions. Various control algorithms may be utilized in the controllers, such as proportional integral derivative (“PID”) control algorithms. However, known algorithms utilized to determine appropriate pitch angles have a variety of disadvantages. For example, the gain factors utilized in the various equations in PID control algorithms typically must be selected to balance competing interests, namely, the responsiveness of the pitch adjustment system and the amount of work that the pitch adjustment system performs. Lower gains reduce the amount of work, thus reducing the risk of damage to the system, but also reduce the responsiveness of the system, thus resulting in higher extreme loads that the system cannot adequately respond to. Higher gains increase the responsiveness of the system, thus resulting in lower extreme loads, but also increase the amount of work, thus increasing the risk of damage to the system.
Accordingly, improved methods and apparatus for adjusting the pitch angles of rotor blades in wind turbines are desired in the art. Specifically, methods and apparatus that allow for specific tailoring of the pitch adjustment system controller and associated control algorithm for varying operating conditions would be advantageous.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one embodiment, the present disclosure is directed to a method for adjusting a pitch angle of a rotor blade in a wind turbine. The method includes monitoring an operational value of the wind turbine, and providing the operational value to a controller, the controller utilizing a proportional integral derivative control algorithm to adjust the pitch angle. The method further includes adjusting a gain factor for the proportional integral derivative control algorithm to a first gain value when the operational value is within a first operational region, and adjusting a gain factor for the proportional integral derivative control algorithm to a second gain value when the operational value is within a second operational region. The second gain value is different from the first gain value, and the second operational region is different from the first operational region.
In another embodiment, the present disclosure is directed to a wind turbine. The wind turbine includes a tower, a nacelle mounted to the tower, and a rotor coupled to the nacelle, the rotor comprising a hub and a plurality of rotor blades. The wind turbine further includes a generator, and a plurality of pitch adjustment mechanisms, each of the plurality of pitch adjustment mechanisms coupled to one of the plurality of rotor blades. The wind turbine further includes a controller in operable communication with one of the plurality of pitch adjustment mechanisms, the controller utilizing a proportional integral derivative control algorithm. The controller is configured to adjust a gain factor for the proportional integral derivative control algorithm to a first gain value when an operational value of the wind turbine is within a first operational region. The controller is further configured to adjust a gain factor for the proportional integral derivative control algorithm to a second gain value when the operational value is within a second operational region. The second gain value is different from the first gain value, and the second operational region is different from the first operational region.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
As shown, the wind turbine 10 may also include a turbine control system or a turbine controller 26 centralized within the nacelle 16. However, it should be appreciated that the turbine controller 26 may be disposed at any location on or in the wind turbine 10, at any location on the support surface 14 or generally at any other location. The turbine controller 26 may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences) and/or components of the wind turbine 10. For example, the controller 26 may be configured to control the blade pitch or pitch angle of each of the rotor blades 22 (i.e., an angle that determines a perspective of the rotor blades 22 with respect to the direction 28 of the wind) to control the loading on the rotor blades 22 by adjusting an angular position of at least one rotor blade 22 relative to the wind. For instance, the turbine controller 26 may control the pitch angle of the rotor blades 22, either individually or simultaneously, by transmitting suitable control signals/commands to various pitch drives or pitch adjustment mechanisms 32 (
It should be appreciated that the turbine controller 26 may generally comprise a computer or any other suitable processing unit. Thus, in several embodiments, the turbine controller 26 may include one or more processor(s) and associated memory device(s) configured to perform a variety of computer-implemented functions. As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) of the turbine controller 26 and/or pitch controller 30 may generally comprise memory element(s) including, but are not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s), configure the controller 26 to perform various computer-implemented functions including, but not limited to, performing proportional integral derivative (“PID”) control algorithms, including various calculations within one or more PID control loops, and various other suitable computer-implemented functions. In addition, the turbine controller 26 may also include various input/output channels for receiving inputs from sensors and/or other measurement devices and for sending control signals to various components of the wind turbine 10.
It should additionally be understood that the controller may be a singular controller or include various components, such as pitch controllers and/or yaw controllers, which communicate with a central controller for specifically controlling pitch and yaw as discussed. Additionally, the term “controller” may also encompass a combination of computers, processing units and/or related components in communication with one another.
Referring now to
It should be appreciated that the rotor shaft 40 may generally be supported within the nacelle by a support frame or bedplate 46 positioned atop the wind turbine tower 12. For example, the rotor shaft 40 may be supported by the bedplate 46 via a pair of pillow blocks 48, 50 mounted to the bedplate 46.
Additionally, as indicated above, the turbine controller 26 may also be located within the nacelle 16 of the wind turbine 10. For example, as shown in the illustrated embodiment, the turbine controller 26 is disposed within a control cabinet 52 mounted to a portion of the nacelle 16. However, in other embodiments, the turbine controller 26 may be disposed at any other suitable location on and/or within the wind turbine 10 or at any suitable location remote to the wind turbine 10. Moreover, as described above, the turbine controller 26 may also be communicatively coupled to various components of the wind turbine 10 for generally controlling the wind turbine and/or such components. For example, the turbine controller 26 may be communicatively coupled to the yaw drive mechanism(s) 38 of the wind turbine 10 for controlling and/or altering the yaw direction of the nacelle 16 relative to the direction 28 (
As discussed, controller 26 may control pitch adjustment of the rotor blades 22. Such control is facilitated at least in part by use of a PID control algorithm. For example, the controller 26 may run a PID control loop for each individual rotor blade 22 or for a group of rotor blades 22. As is generally understood, a PID control algorithm includes a generic control loop feedback mechanism that is widely used in processing applications to calculate an “error” as the difference between a measured process value (PV) (e.g., current pitch angle) and a desired setpoint value (SP) (e.g., desired pitch angle). Thus, utilizing a PID control loop, the controller 26 may be configured to minimize the error by adjusting the process control inputs.
For example,
P
out
=K
p
e(t)
The integral (I) value (also called “reset”) makes a change to the CV output that is proportional to the magnitude and duration of the error by integrating the error over time and multiplying the value by a tunable integral gain factor Ki:
I
out
=K
i∫0te(τ)dτ
The integral (I) term accelerates process towards the setpoint and eliminates the inherent steady-state error that occurs with proportional-only controllers.
The derivative (D) value (also called “rate”) makes a change to the CV output as a function of the slope of the error over time multiplied by a tunable derivative gain factor Kd:
The derivative (D) term slows the rate of change of the controller output and reduces the magnitude of the overshoot produced by the integral (I) term.
The proportional (P), integral (I), and derivative (D) terms are summed to calculate the CV output (u(t)) of the PID controller:
As discussed below, the control algorithm is “tuned” to the specific requirements of the process by adjustment of the different gain factors (Kp, Ki, Kd) to achieve an optimum control response.
As discussed, improved methods and apparatus for adjusting the pitch angles of the rotor blades 22, which allow for specific tailoring of the controller 26 and associated control algorithm, are desired. Accordingly, the present disclosure is further directed to methods for adjusting the pitch angle of the rotor blades 22, and to wind turbines 10 that include controllers 26 capable of such operation. Such methods allow for adjustment of the gain factors utilized in the control algorithm based on operational values detected during operation of the wind turbine, such that various levels of gains can advantageously be utilized in appropriate operating conditions. For example, low gains may be utilized in operating conditions wherein the risk of excessive rotor blade 22 loading is low, high gains may be utilized in operating conditions wherein the risk of excessive rotor blade 22 loading is high, and medium gains may be utilized in operating conditions wherein the risk of excessive rotor blade 22 loading is medium.
A method according to the present disclosure may include, for example, monitoring one or more operational values of the wind turbine 10, as shown in step 100 of
As shown in step 102 of
As discussed, the controller 26 may utilize PID algorithms to adjust the pitch angle of the various rotor blades 22. A method according to the present disclosure may thus include adjusting one or more gain factors Kp, Ki, Kd based on the operational values. For example, each operational value, and changes thereto, may be correlated with the risk of excessive rotor blade 22 loading. The gain factors Kp, Ki, Kd can then be adjusted based on changes in the operational values such that suitable gain factors Kp, Ki, Kd are utilized that are appropriate for the associated risk of excessive rotor blade 22 loading. It should be understood that gain factors according to the present disclosures are multipliers utilized as discussed above in PID algorithms. It should further be understood that gain values, as discussed below, are numerical values utilized as gain factors in the PID algorithms.
For example, as shown in
In some embodiments as shown, the first gain value 120 may be 1. Alternatively, however, any suitable value above or below 1 may be utilized as a first gain value 120.
As further shown in
In
In some embodiments, as shown in
In some embodiments as shown, the second gain value 124 may be between approximately 2 and approximately 4. Alternatively, however, any suitable value above approximately 4 or below approximately 2 may be utilized as a second gain value 124.
As further shown in
In some embodiments, the third gain value 128 may be a third gain value range, as shown in
In
It should additionally be understood that the first gain values, as well as any other suitable gain values, may be single values or ranges of values, as desired or required.
It should further be understood that the present disclosure is not limited to three gain values and operational regions, and rather that any suitable number or values and regions is within the scope and spirit of the present disclosure.
It should be noted that a gain factor utilized in a method according to the present disclosure may be a proportional gain factor Kp, an integral gain factor Ki, or a derivative gain factor Kd.
In exemplary embodiments, a method according to the present disclosure may further include adjusting a pitch angle of one or more rotor blades 22, as shown as step 116 of
The present disclosure is further directed to a controller 26 that utilizes a PID control algorithm, and to a wind turbine 10 utilizing such controller 26. The controller 26 according to the present disclosure may be configured to adjust one or more gain factors Kp, Ki, Kd to first gain values 120 when operational values are within first operational regions 122, to second gain values 124 when operational values are within second operational regions 126, and optionally to third gain values 128 when operational values are within third operational regions 130, as discussed above. The controller 26 may be in operable communication with one or more pitch adjustment mechanisms 32, and may thus be operable to pitch one or more rotor blades 22 as desired or required.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
