System and method for controlling a wind turbine

Abstract

A system and method for controlling a wind turbine is provided. Thus, a controller of the wind turbine detects an oscillation in the power output of the wind turbine during recovery from a transient event. In response to detecting the oscillation, a portion of the power output during a peak phase of the oscillation is stored in an energy storage device. The portion of stored power is then discharged during a valley phase of the oscillation in order to reduce an amplitude of the oscillation in the power output delivered to a power grid.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wind turbines, and more particularly, to systems and methods for controlling a wind turbine in response to transient grid events. BACKGROUND

[0002] Wind power generation is considered one of the cleanest and most environmentally friendly sources of energy available today, and wind turbines are gaining increasing attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The nacelle includes a rotor assembly coupled to the gearbox and generator. The rotor assembly and gearbox are mounted on a bedplate support frame that is located within the nacelle. The one or more rotor blades use known airfoil principles to capture kinetic energy of the wind. The rotor blades transfer the kinetic energy in the form of rotational energy to a shaft that couples the rotor blades to the gearbox, or directly to the generator if no gearbox is used. The generator then converts the mechanical energy into electrical energy, and the electrical energy can be transferred to a converter and / or transformer housed within the tower and then deployed to a utility grid. Modern wind power systems typically take the form of a wind farm having a plurality of such wind turbine generators that are operable to supply power to a transmission system that provides power to a power grid.

[0003] To supply power to the power grid, wind turbines generally need to comply with certain grid requirements. For example, wind turbines can be required to provide a fault ride-through (e.g., low voltage ride-through) capability. This requirement can require the wind turbine to remain connected to the power grid during one or more transient grid events, such as a grid fault. As used herein, the term "grid fault," "fault," or the like is intended to cover a change in the magnitude of the grid voltage for a period of time. For example, when a grid fault occurs, the voltage of the system can drop by a substantial amount for a short period of time (e.g., typically less than 500 milliseconds). Moreover, grid faults can occur for a variety of reasons, including but not limited to a phase conductor being connected to ground (i.e., a ground fault), a short circuit between phase conductors, lightning and / or a storm, and / or an accidental transmission line grounding.

[0004] In the past, wind turbines could be disconnected immediately in response to a voltage decrease, but as the amount of power production by wind turbines as a percentage of the power grid has increased, the desirability of keeping wind turbines online and riding through transient grid events has increased. However, a voltage decrease of a transient grid event can result in a significant decrease in the torque of the generator while the rotational speed of the rotor can remain substantially constant. In this regard, when the grid voltage recovers to the pre-fault level, the mismatch between the torque of the generator and the inertia of the rotor can result in undesirable torsional vibrations in the drivetrain of the wind turbine. The torsional vibrations can manifest as oscillations in the power produced by the wind turbine that exceed certain power grid limits.

[0005] Therefore, there is a continuing need in the art for new and improved systems and methods that address the aforementioned problems. In this regard, the present disclosure relates to systems and methods for controlling a wind turbine to manage oscillations in the power output of the wind turbine in response to a transient grid event. SUMMARY

[0006] Aspects and advantages of the application will be set forth in part in the following description, or can be obvious from the description, or can be learned through practice of the application.

[0007] In one aspect, the present disclosure relates to a method for controlling a wind turbine connected to a power grid and including a generator. The method can include receiving, via a controller, an indication of a transient event occurring in the power grid. Further, the method can include detecting, via the controller, an oscillation in the power output of the wind turbine during a transient event recovery phase following the transient event. The oscillation can include a peak phase followed by a trough phase, the peak phase in the trough phase being determined relative to the power output prior to the transient event. In response to detecting the oscillation, the method can include storing at least a portion of a peak phase power in an energy storage device operably coupled to the generator to establish a stored charge. The peak phase power can correspond to the power output during the peak phase. Further, the method can include discharging at least a portion of the stored charge to the power grid during the trough phase of the oscillation to reduce an amplitude of the oscillation in the power output delivered to the power grid.

[0008] In embodiments, discharging at least a portion of the stored charge can further include determining, via the controller, a duration of the trough phase. The method can further include synchronizing a duration of the discharging of the portion of the stored charge with the duration of the trough phase.

[0009] In additional embodiments, the method can further include determining, via the controller, a slope rate and an amplitude of the oscillation during the trough phase. Further, the method can include synchronizing the discharging of the portion of the stored charge with the slope rate and the amplitude of the oscillation during the trough phase.

[0010] In yet another embodiment, the method can include determining an upper threshold and a lower threshold for a deviation of the power output of the wind turbine from the power output of the wind turbine prior to the transient event. The upper threshold and the lower threshold can define an oscillation tolerance band. The portion of the peak phase power stored via the energy storage device can be a portion of the peak phase power that exceeds the upper threshold. Further, the method can include determining, via the controller, a portion of the valley phase power that is below the lower threshold. The portion of the stored charge discharged can correspond to the portion of the valley phase power that is below the lower threshold. The valley phase power can correspond to a portion of the power output during the valley phase. The method can further include repeating the storing and discharging steps for subsequent oscillations until the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0011] In still another embodiment, the threshold can be a first upper threshold and a first lower threshold that are applied at a first interval after the transient event. Accordingly, the method can further include determining a second upper threshold and a second lower threshold for a deviation of the power output of the wind turbine from the power output prior to the transient event. The second upper threshold and the second lower threshold can be applied at a second interval after the first interval and can have a smaller deviation from the power output prior to the transient event than the first upper threshold and the first lower threshold.

[0012] In an embodiment, the method can include discharging a remaining portion of the stored charge to the power grid at a remaining discharge rate when the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0013] In an additional embodiment, the method can include determining, via an oscillation compensation control module of the controller, a magnitude of the portion of the peak phase power stored by the energy storage device in response to the detection of the oscillation. Further, the method can include determining, via the oscillation compensation control module, a magnitude of the portion of the stored charge discharged upon the detection of the valley phase. Further, the method can include generating, via the oscillation compensation control module, a set point command for a line side converter of a power converter of the wind turbine in order to obtain the determined stored charge and discharge.

[0014] In yet another embodiment, a method can include receiving, via an oscillation compensation control module, a plurality of operating parameters. The oscillation compensation control module can also receive a damping torque command from a power transmission system damping system of a wind turbine. The method can also include determining, via the oscillation compensation control module, a plurality of oscillation parameters for a power output of the wind turbine based on one or more of the operating parameters and the damping torque command. Further, the method can include filtering, via the oscillation compensation control module, the plurality of oscillation parameters to obtain a plurality of oscillation power components. The plurality of oscillation components can include a stator oscillation power, a rotor oscillation power, and / or a line side oscillation power. The method can also include determining, via the oscillation compensation control module, a magnitude of a portion of peak phase power stored by an energy storage device based at least in part on at least one of the plurality of oscillation power components.

[0015] In still another embodiment, a method can include determining, via a control module, a magnitude of a transient event based on a plurality of operating parameters. The method can also include initiating, via the control module, a first operating mode and / or a second operating mode based on the magnitude of the transient event. The first operating mode can include storing and discharging rotor oscillation power. The second operating mode can include storing and discharging both rotor oscillation power and stator oscillation power.

[0016] In an embodiment, the plurality of operating parameters can indicate a slip magnitude, a generator speed, and a plurality of voltages and currents. The plurality of voltages and currents can include stator voltages and currents, rotor voltages and currents, and line side voltages and currents at each of the three-phase power. Determining the plurality of oscillation parameters for the power output of the wind turbine can be based on the slip magnitude, the generator speed, and the damping torque command.

[0017] In an additional embodiment, the energy storage device can be a battery and / or a super capacitor.

[0018] In yet another embodiment, receiving an indication of a transient event occurring in a power grid can include receiving, via a controller, data indicative of the change event from a sensor operably coupled between a line side of a power converter of the wind turbine and a point of interconnection with the power grid.

[0019] In still another embodiment, the transient event can be a zero voltage ride through event, a low voltage ride through event, and / or a high voltage ride through event.

[0020] In another aspect, the present disclosure relates to a system for controlling a wind turbine connected to a power grid. The system can include a generator operably coupled to an energy storage device, and a controller communicatively coupled to the generator. The controller can include at least one processor configured to perform a plurality of operations. The plurality of operations can include any of the operations and / or features described herein.

[0021] 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.

[0022] Technical Solution 1. A method for controlling a wind turbine connected to a power grid, the wind turbine comprising a generator, the method comprising:

[0023] receiving, via a controller, an indication of a transient event occurring in the power grid;

[0024] detecting, via the controller, an oscillation in a power output of the wind turbine during a transient event recovery phase following the transient event, the oscillation comprising a peak phase followed by a trough phase with respect to the power output prior to the transient event;

[0025] in response to detecting the oscillation, storing at least a portion of a peak phase power in an energy storage device, the energy storage device operably coupled to the generator to establish a stored charge, wherein the peak phase power corresponds to a power output during the peak phase; and

[0026] during the trough phase of the oscillation, discharging at least a portion of the stored charge to the power grid to reduce an amplitude of the oscillation in the power output delivered to the power grid.

[0027] Technical Solution 2. The method of Technical Solution 1, wherein discharging at least the portion of the stored charge further comprises:

[0028] determining, via the controller, a duration of the trough phase; and

[0029] synchronizing a duration of the discharging of the portion of the stored charge with the duration of the trough phase.

[0030] Technical Solution 3. The method of Technical Solution 2, further comprising:

[0031] determining, via the controller, a slope rate and an amplitude of the oscillation during the trough phase; and

[0032] synchronizing the discharging of the portion of the stored charge with the slope rate and the amplitude of the oscillation during the trough phase.

[0033] Technical Solution 4. The method of Technical Solution 1, further comprising:

[0034] determining an upper threshold and a lower threshold of a deviation of the power output of the wind turbine relative to the power output of the wind turbine prior to the transient event, the upper threshold and the lower threshold defining an oscillation tolerance band, and wherein the portion of the peak phase power stored via the energy storage device is a portion of the peak phase power that exceeds the upper threshold;

[0035] determining, via the controller, a portion of a valley phase power that is below the lower threshold, wherein the portion of the stored charge discharged corresponds to the portion of the valley phase power that is below the lower threshold, wherein the valley phase power corresponds to a portion of power output during the valley phase; and

[0036] repeating the storing and discharging steps for subsequent oscillations until the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0037] Technical Solution 5. The method of Technical Solution 4, wherein the upper threshold and lower threshold are a first upper threshold and a first lower threshold that are applied at a first interval after the transient event, the method further comprising:

[0038] determining a second upper threshold and a second lower threshold of the power output of the wind turbine relative to the power output prior to the transient event, wherein the second upper threshold and second lower threshold are applied at a second interval after the first interval and have a smaller deviation from the power output prior to the transient event than the first upper threshold and the first lower threshold.

[0039] Technical Solution 6. The method of Technical Solution 4, the method further comprising:

[0040] discharging a remaining portion of the stored charge to the power grid at a remaining discharge rate when the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0041] Technical Solution 7. The method of Technical Solution 1, the method further comprising:

[0042] determining, via an oscillation compensation control module of the controller, a magnitude of the portion of the peak phase power stored by the energy storage device in response to the detection of the oscillation;

[0043] determining, via the oscillation compensation control module, a magnitude of the portion of the stored charge discharged at the detection of the valley phase; and

[0044] via the oscillation compensation control module, generating a setpoint command for a line side converter of a power converter of the wind turbine in order to obtain the determined stored charge and discharge.

[0045] Technical solution 8. The method of technical solution 7, further comprising:

[0046] receiving, via the oscillation compensation control module, a plurality of operating parameters;

[0047] receiving, via the oscillation compensation control module, a damping torque command from a drivetrain damping system of the wind turbine;

[0048] determining, via the oscillation compensation control module, a plurality of oscillation parameters for the power output of the wind turbine based on one or more of the operating parameters and the damping torque command;

[0049] filtering, via the oscillation compensation control module, the plurality of oscillation parameters to obtain a plurality of oscillation power components, the plurality of oscillation power components comprising at least one of a stator oscillation power, a rotor oscillation power, and a line side oscillation power; and

[0050] determining, via the oscillation compensation control module, a magnitude of the portion of the peak phase power stored by the energy storage device based at least in part on at least one of the plurality of oscillation power components.

[0051] Technical solution 9. The method of technical solution 8, further comprising:

[0052] determining, via the oscillation compensation control module, a magnitude of the transient event based on the plurality of operating parameters; and

[0053] initiating, via the oscillation compensation control module, one of a first operating mode or a second operating mode based on the magnitude of the transient event, wherein the first operating mode comprises storing and discharging the rotor oscillation power, and wherein the second operating mode comprises storing and discharging both the rotor oscillation power and the stator oscillation power.

[0054] Technical solution 10. The method of technical solution 8, wherein the plurality of operating parameters indicate a slip magnitude, a generator speed, and a plurality of voltages and currents, the plurality of voltages and currents comprising a stator voltage and current, a rotor voltage and current, and a line side voltage and current at each of three phase powers, and wherein determining the plurality of oscillation parameters for the power output of the wind turbine is based on the slip magnitude, the generator speed, and the damping torque command.

[0055] CLAIM 11. The method of claim 1, wherein the energy storage device comprises at least one of a battery and a supercapacitor.

[0056] CLAIM 12. The method of claim 1, wherein receiving the indication of the transient event occurring in the power grid further comprises:

[0057] receiving, via the controller, data indicative of the transient event from a sensor operably coupled between a line side of a power converter of the wind turbine and a point of interconnection with the power grid.

[0058] CLAIM 13. The method of claim 12, wherein the transient event comprises one of a zero voltage ride through event, a low voltage ride through event, and a high voltage ride through event.

[0059] CLAIM 14. The method of claim 1, wherein receiving the indication of the transient event further comprises:

[0060] detecting, via the controller, a change in a powertrain torque aspect of the wind turbine indicative of the transient event.

[0061] CLAIM 15. A system for controlling a wind turbine connected to a power grid, the system comprising:

[0062] a generator operably coupled to an energy storage device; and

[0063] a controller communicatively coupled to the generator, the controller comprising at least one processor configured to perform a plurality of operations, the plurality of operations comprising:

[0064] receiving an indication of a transient event occurring in the power grid,

[0065] detecting, during a transient event recovery phase following the transient event, an oscillation in a power output of the wind turbine, the oscillation comprising a peak phase followed by a trough phase with respect to the power output prior to the transient event,

[0066] in response to detecting the oscillation, storing at least a portion of a peak phase power in an energy storage device operably coupled to the generator to establish a stored charge, wherein the peak phase power corresponds to a power output during the peak phase, and

[0067] during the trough phase of the oscillation, discharging at least a portion of the stored charge to the power grid so as to reduce an amplitude of the oscillation in the power output delivered to the power grid.

[0068] Technical Solution 16. The system of Technical Solution 15, wherein discharging at least the portion of the stored charge further comprises:

[0069] determining a duration of the valley phase; and

[0070] synchronizing the discharging of the portion of the stored charge with the duration of the valley phase.

[0071] Technical Solution 17. The system of Technical Solution 15, wherein the plurality of operations further comprise:

[0072] determining an upper threshold and a lower threshold of a deviation of the power output of the wind turbine relative to the power output of the wind turbine prior to the transient event, the upper threshold and the lower threshold defining an oscillation tolerance band, wherein the portion of the peak phase power stored via the energy storage device is a portion of the peak phase power that exceeds the upper threshold;

[0073] determining a portion of valley phase power that is below the lower threshold, wherein the portion of the stored charge that is discharged corresponds to the portion of the valley phase power that is below the lower threshold, wherein the valley phase power corresponds to a portion of power output during the valley phase; and

[0074] repeating the storing and discharging steps for subsequent oscillations until the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0075] Technical Solution 18. The system of Technical Solution 15, wherein the plurality of operations further comprise:

[0076] determining a magnitude of the portion of the peak phase power stored by the energy storage device;

[0077] determining an amount of the stored charge to discharge at the detection of the valley phase; and

[0078] generating a set point command for a line side converter of a power converter of the wind turbine in order to obtain the determined stored charge and discharge.

[0079] Technical Solution 19. The system of Technical Solution 18, wherein the plurality of operations further comprise:

[0080] receiving a plurality of operating parameters indicative of a slip magnitude, a generator speed, and a plurality of voltages and currents, the plurality of voltages and currents including a stator voltage and current, a rotor voltage and current, and a line side voltage and current at each of three phase powers;

[0081] receiving a damping torque command from a drivetrain damping system of the wind turbine;

[0082] determining, based on the slip magnitude, the generator speed, and the damping torque command, a plurality of oscillation parameters for the power output of the wind turbine;

[0083] filtering, via an oscillation compensation control module, the plurality of oscillation parameters to obtain a plurality of oscillation power components, the plurality of oscillation power components including at least one of a stator oscillation power, a rotor oscillation power, and a line side oscillation power; and

[0084] determining, via the oscillation compensation control module, a magnitude of the portion of the peak stage power stored by the energy storage device based at least in part on at least one of the plurality of oscillation power components.

[0085] Technical Solution 20. The system of Technical Solution 19, wherein the plurality of operations further comprise:

[0086] determining, via the oscillation compensation control module, a magnitude of the transient event based on the plurality of operating parameters; and

[0087] initiating, via the oscillation compensation control module, one of a first operating mode or a second operating mode based on the magnitude of the transient event, wherein the first operating mode includes storing and discharging the rotor oscillation power, and wherein the second operating mode includes storing and discharging both the rotor oscillation power and the stator oscillation power. BRIEF DESCRIPTION OF DRAWINGS

[0088] The complete and enabling disclosure of the present application, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification, which makes reference to the appended drawings, in which:

[0089] Figure 1 shows a perspective view of one embodiment of a wind turbine according to the present disclosure;

[0090] Figure 2 shows a perspective internal view of one embodiment of a nacelle of a wind turbine according to the present disclosure;

[0091] Figure 3 shows a schematic view of one embodiment of a powertrain of a wind turbine according to the present disclosure;

[0092] Figure 4 shows a schematic view of one embodiment of an electrical system for use with a wind turbine according to the present disclosure;

[0093] Figure 5a block diagram illustrating one embodiment of a controller for use with a wind turbine according to the present disclosure;

[0094] Figure 6 a flow diagram illustrating one embodiment of control logic of a system for controlling a wind turbine according to the present disclosure;

[0095] Figure 7 a flow diagram illustrating one embodiment of an extended portion of control logic according to the present disclosure; Figure 6

[0096] Figure 8 a graphical illustration of one embodiment of power output of a wind turbine according to the present disclosure;

[0097] Figure 9A a graphical illustration of one embodiment of power output of a wind turbine after a transient grid event according to the present disclosure;

[0098] Figure 9B a graphical illustration of one embodiment of power output of a wind turbine according to the present disclosure, particularly illustrating a portion of peak phase power and a portion of stored charge; and

[0099] Figure 9C a graphical illustration of one embodiment of power output of a wind turbine as delivered to a power grid according to the present disclosure.

[0100] The repeated use of reference characters in the present specification and drawings is intended to denote the same or similar features or elements. DETAILED DESCRIPTION

[0101] Reference will now be made in detail to embodiments of the application, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the application and is not meant as a limitation of the application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the scope or spirit of the application. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield still a further embodiment. Thus, it is intended that the present application covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0102] As used herein, the terms "first", "second" and "third" can be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.

[0103] The terms "coupled", "fixed", "attached" and like terms are used to indicate either a direct or indirect connection, as appropriate, unless stated otherwise. ​

[0104] Approximating language as used herein throughout the specification and claims is applied to any quantitative representation that can be perceived to be close to or approximately the same as its intended meaning. Accordingly, a value modified by a term or terms, such as "about", "approximately”, and "substantially”, will not be limited to the precise value specified. In at least some instances, the approximating language can correspond to the precision of an instrument for measuring the value or the precision of the measurement techniques employed to determine the value. For example, the approximating language can refer to being within 10% of a value.

[0105] Throughout the specification and claims, range limitations are combined and interchanged, such ranges are identified and include all the sub-ranges contained therein, unless context or language indicates otherwise. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0106] Generally, the present disclosure relates to systems and methods for controlling a wind turbine in order to reduce oscillations in the electrical power delivered by the wind turbine to a power grid following a transient grid event. Typically, a wind turbine utilizes torque generated by a generator to counteract torque generated by a rotor in response to the wind. Many modern wind turbines employ a generator, such as a doubly-fed induction generator (DFIG), which utilizes grid power for the generation of generator torque. At the onset of a transient grid event, such as a low voltage ride through (LVRT) event, the grid power can suddenly decrease, resulting in a corresponding decrease in generator torque. However, due to inertia and / or the influence of the wind, the rotor can continue to rotate at the same speed, and in some cases, can accelerate while rotation is not significantly resisted by the generator torque. When the transient grid event ends and the grid power recovers, the generator can quickly return to generating generator torque in order to restore the wind turbine to a power generating state. However, within the drivetrain of the wind turbine, the generator torque can encounter torque caused by the rotation of the rotor. This encounter can generate torsional vibrations within the drivetrain. A drivetrain damper (DTD) control system can be employed to quickly dampen the generated torsional vibrations. However, until the torsional vibrations are damped, the torsional vibrations can cause oscillations in the power output of the wind turbine delivered to the power grid. Accordingly, the systems and methods of the present disclosure can be employed to shape the power output of the wind turbine until the torsional vibrations are damped and stable power production is reestablished following the transient event.

[0107] In particular, the present disclosure includes systems and methods that can detect oscillations in a power output of a wind turbine during a transient event recovery phase following a transient event. The oscillations in the power output can be characterized by at least one peak phase (e.g., crest phase) during which the power output of the wind turbine can be greater than the power output of the wind turbine prior to the transient event. Each peak phase can be followed by a trough phase (e.g., trough phase) during which the power output of the wind turbine can fall below the power output of the wind turbine prior to the transient event.

[0108] Because the oscillations in the power output can exceed certain grid requirements related to the stability of the power delivered to the grid, the controller can store at least a portion of the peak phase power in an energy storage device. At least a portion of the stored power can then be discharged to the power grid during the trough phase. In other words, a portion of the power generated during the peak phase that exceeds a threshold value can be diverted to the energy storage device, rather than delivered to the power grid. Similarly, once the power output falls below a minimum threshold value, the additional power stored from the peak phase can be discharged to the grid to make up for the difference between the minimum threshold value and the actual power production during the trough phase. Thus, the power output can not exceed an upper deviation threshold value, and can remain above a minimum deviation threshold value, as experienced by the power grid. Accordingly, even though torsional vibrations can be present during the transient event recovery phase, the power oscillations resulting from the torsional vibrations can not be delivered to the power grid. In effect, by selectively diverting and then discharging a portion of the power output of the generator, the effects of the torsional vibrations on the power output of the wind turbine can be substantially hidden from the power grid. This, in turn, can improve the ability of the wind turbine to meet grid specification requirements related to power oscillations following a grid event, such as requirements to control rise time, overshoot / undershoot, settling time, and / or dampen oscillatory response.

[0109] Referring now to the drawings, Figure 1A perspective view of one embodiment of a wind turbine 100 according to the present disclosure is shown. As shown, the wind turbine 100 generally includes a tower 102 extending from a support surface 104, a nacelle 106 mounted on the tower 102, and a rotor 108 coupled to the nacelle 106. The rotor 108 includes a rotatable hub 110 and at least one rotor blade 112 coupled to and extending outward from the hub 110. For example, in the embodiment shown, the rotor 108 includes three rotor blades 112. However, in alternative embodiments, the rotor 108 can include more or less than three rotor blades 112. Each rotor blade 112 can be spaced apart from the hub 110 to facilitate rotation of the rotor 108 to enable kinetic energy to be converted from the wind into usable mechanical energy and subsequently into electrical energy. For example, the hub 110 can be rotatably coupled to a generator 118 of an electrical system 400 Figure 2 ) positioned within the nacelle 106 to permit electrical energy production. Figure 2

[0110] The wind turbine 100 can also include a controller 200 centralized within the nacelle 106. However, in other embodiments, the controller 200 can be located within any other component of the wind turbine 100, or at a location external to the wind turbine. Moreover, the controller 200 can be communicatively coupled to any number of components of the wind turbine 100 in order to control the components. In this regard, the controller 200 can include a computer or other suitable processing unit. Thus, in several embodiments, the controller 200 can include suitable computer-readable instructions that, when implemented, configure the controller 200 to perform a variety of different functions, such as receiving, transmitting, and / or executing wind turbine control signals.

[0111] Referring now to Figures 2-4 , a simplified internal view of one embodiment of the nacelle 106, a schematic view of one embodiment of a power transmission system 146, and Figure 1 ​An exemplary electrical system 400 of the wind turbine 100 is shown. As shown, the generator 118 can be coupled to the rotor 108 for generating electrical power from rotational energy generated by the rotor 108. For example, as shown in the illustrated embodiment, the rotor 108 can include a rotor shaft 122 coupled to the hub 110 for rotation therewith. The rotor shaft 122 can be rotatably supported by a main bearing 144. The rotor shaft 122 can in turn be rotatably coupled to a high speed shaft 124 of the generator 118 through an optional gearbox 126 connected to a bedplate support frame 136 by one or more torque arms 142. As generally understood, the rotor shaft 122 can provide a low speed, high torque input to the gearbox 126 in response to rotation of the rotor blades 112 and the hub 110. The gearbox 126 can then be configured with a plurality of gears 148 to convert the low speed, high torque input to a high speed, low torque output to drive the high speed shaft 124 and thus the generator 118. In embodiments, the gearbox 126 can be configured with a plurality of gear ratios in order to produce varying rotational speeds of the high speed shaft for a given low speed input, or vice versa.

[0112] In embodiments, the rotor 108 can be slowed via a torque generated by the generator 118. Because the generator 118 can generate a torque opposite to the rotation of the rotor 108, the high speed shaft 124 can be equipped with a slip coupling 154. The slip coupling 154 can prevent damage to components of the drivetrain 146 due to overloading of the drivetrain 146. In this regard, the slip coupling 154 can have a release threshold or traction force above which the slip coupling 154 can allow the first portion 162 and the second portion 164 of the high speed shaft 124 to have different rotational speeds. It should be appreciated that if the torsional moment at the slip coupling 154 exceeds the release / traction threshold, the generator 118 can be communicatively decoupled from the rotor 108. In such a case, the torque generated by the generator 118 can be unavailable to slow the rotor 108, or the increased rotational speed of the rotor 108 can be unavailable for increased power production.

[0113] Each rotor blade 112 can also include a pitch control mechanism 120 configured to rotate the rotor blade 112 about its pitch axis 116. Each pitch control mechanism 120 can include a pitch drive motor 128 (e.g., any suitable electric, hydraulic, or pneumatic motor), a pitch drive gearbox 130, and a pitch drive pinion 132. In such embodiments, the pitch drive motor 128 can be coupled to the pitch drive gearbox 130 such that the pitch drive motor 128 imparts mechanical force to the pitch drive gearbox 130. Similarly, the pitch drive gearbox 130 can be coupled to the pitch drive pinion 132 for rotation therewith. The pitch drive pinion 132 can in turn be in rotational engagement with a pitch bearing 134 coupled between the hub 110 and the corresponding rotor blade 112 such that rotation of the pitch drive pinion 132 causes rotation of the pitch bearing 134. Thus, in such embodiments, rotation of the pitch drive motor 128 drives the pitch drive gearbox 130 and the pitch drive pinion 132, thereby rotating the pitch bearing 134 and rotor blade(s) 112 about the pitch axis 116. Similarly, the wind turbine 100 can include one or more yaw drive mechanisms 138 communicatively coupled to the controller 200, where each yaw drive mechanism 138 is configured to change the angle of the nacelle 106 relative to the wind (e.g., by engaging a yaw bearing 140 of the wind turbine 100).

[0114] With particular reference to Figure 2 In embodiments, the wind turbine 100 can include at least one operational sensor 158. The operational sensor(s) 158 can be configured to detect performance of the wind turbine 100, for example, in response to environmental conditions. For example, the operational sensor(s) 158 can be a rotational speed sensor operably coupled to the controller 200. The operational sensor(s) 158 can be directed at the rotor shaft 122 of the wind turbine 100 and / or generator 118. The operational sensor(s) 158 can collect data indicative of the rotational speed and / or rotational position of the rotor shaft 122, and thus the rotor 108 in the form of rotor speed and / or rotor azimuth angle. In embodiments, the operational sensor(s) 158 can be an analog tachometer, a DC tachometer, an AC tachometer, a digital tachometer, a contact tachometer, a non-contact tachometer, or a time and frequency tachometer. In embodiments, the operational sensor(s) 158 can be, for example, an encoder, such as an optical encoder. Further, the operational sensor(s) 158 can be configured to monitor a plurality of electrical conditions, such as slip, stator voltage and current, rotor voltage and current, and line side voltage and current at each of the three-phase power. Thus, in embodiments, the operational sensor(s) 158 can be configured to monitor operational parameters 301 Figure 6 ) of the wind turbine 100.

[0115] Further, in embodiments, the wind turbine 100 can include or be operably coupled to at least one grid sensor 156 configured to monitor at least one parameter of the power grid 179 and / or the power output of the wind turbine 100 to the power grid 179. For example, the grid sensor(s) 156 can be configured to continuously monitor the voltage of the power grid 179 as experienced by the wind turbine 100, and vice versa. Accordingly, in embodiments, the grid sensor(s) 156 can be an ammeter, a voltmeter, an ohmmeter, and / or any other suitable sensor for monitoring the power of the power grid 179 and / or the power output of the wind turbine 100.

[0116] It should also be recognized that, as used herein, the term "monitor" and variations thereof indicate that the various sensors of the wind turbine 100 can be configured to provide a direct measurement of the parameter being monitored or an indirect measurement of such parameter. Accordingly, the sensors described herein can be used, for example, to generate a signal related to the parameter being monitored, which can then be utilized by the controller 200 to determine a condition or response of the wind turbine 100.

[0117] With particular reference to Figure 4 In embodiments, the electrical system 400 can include various components for converting the kinetic energy of the rotor 108 into an electrical output in an acceptable form to the connected power grid 179. For example, in embodiments, the generator 118 can be a doubly-fed induction generator (DFIG) having a stator 402 and a generator rotor 404. The generator 118 can be coupled to a stator bus 406 and a power converter 408 via a rotor bus 410. In such a configuration, the stator bus 406 can provide output multiphase power (e.g., three-phase power) from the stator of the generator 118, and the rotor bus 410 can provide output multiphase power (e.g., three-phase power) from the generator rotor 404 of the generator 118. Further, the generator 118 can be coupled to a rotor-side converter 412 via the rotor bus 410. The rotor-side converter 412 can be coupled to a line-side converter 414, which can in turn be coupled to a line-side bus 416.

[0118] In embodiments, the rotor-side converter 412 and the line-side converter 414 can be configured for a normal mode of operation in a three-phase pulse width modulation (PWM) arrangement using insulated gate bipolar transistors (IGBTs) as switching devices. Other suitable switching devices can be used, such as insulated gate commutated thyristors, MOSFETs, bipolar transistors, silicon controlled rectifiers, and / or other suitable switching devices. The rotor-side converter 412 and the line-side converter 414 can be coupled across a DC link capacitor 420 via a DC link 418.

[0119] In embodiments, the power converter 408 can be coupled to the controller 200, which is configured as a converter controller 202 to control operation of the power converter 408. For example, the converter controller 202 can send control commands to the rotor-side converter 412 and the line-side converter 414 to control modulation of switching elements used in the power converter 408 to establish a desired generator torque setpoint and / or power output.

[0120] As Figure 4 As further depicted in FIG. 4, in embodiments, the electrical system 400 can include a transformer 422 that couples the wind turbine 100 to the power grid 179. In embodiments, the transformer 422 can be a 3-winding transformer that includes a high voltage (e.g., greater than 12 KV AC) primary winding 424. The high voltage primary winding 424 can be coupled to the power grid 179. The transformer 422 can also include a medium voltage (e.g., 6 KV AC) secondary winding 426 coupled to the stator bus 406, and a low voltage (e.g., 575 V AC, 690 V AC, etc.) auxiliary winding 428 coupled to the line bus 416. It should be appreciated that the transformer 422 can be a three-winding transformer as depicted, or alternatively, can be a two-winding transformer having only the primary winding 424 and the secondary winding 426; can be a four-winding transformer having the primary winding 424, the secondary winding 426, and the auxiliary winding 428, as well as additional auxiliary windings; or can have any other suitable number of windings.

[0121] In embodiments, the electrical system 400 can also include various circuit breakers, fuses, contactors, and other devices to control and / or protect various components of the electrical system 400. For example, in embodiments, the electrical system 400 can include a grid circuit breaker 430, a stator bus circuit breaker 432, and / or a line bus circuit breaker 434. The circuit breaker(s) 430, 432, 434 of the electrical system 400 can connect or disconnect corresponding components of the electrical system 400 when conditions of the electrical system 400 approach operating thresholds of the electrical system 400.

[0122] According to the present disclosure, in embodiments, the electrical system 400 can include an energy storage device 436 operably coupled to the generator 118. In embodiments, the energy storage device 436 can be a battery and / or a supercapacitor configured to receive electrical charge from the generator 118 and discharge electrical charge to the power grid 179. Accordingly, the energy storage device 436 can be coupled to the power converter 408 via a bidirectional converter 438. For example, in embodiments, the bidirectional converter 438 can be operably coupled to the DC link 418. In embodiments, the energy storage device 436 can be communicatively coupled to the controller 200 via the bidirectional converter 438 such that the controller 200 can direct operation of the energy storage device 436 as disclosed herein. It should be appreciated that the energy storage device 436 can be a pre-existing component operably coupled to the wind turbine 100, such as in embodiments where the wind turbine 100 is a hybrid power generation facility.

[0123] Still referring to Figure 4 and also referring to Figure 5 -9, a number of embodiments of a system 300 for controlling a wind turbine 100 according to the present disclosure are presented. As Figure 5 particularly shown in FIG. 9, a schematic diagram of one embodiment of suitable components that can be included within the system 300 is shown. For example, as shown, the system 300 can include a controller 200 communicatively coupled to the operating sensor(s) 158 and the grid sensor(s) 156. Further, as shown, the controller 200 includes one or more processors 206 and associated storage device(s) 208 configured to perform various computer-implemented functions (e.g., perform methods, steps, calculations, etc., and store related data as disclosed herein). Further, the controller 200 can also include a communication module 210 to facilitate communication between the controller 200 and various components of the wind turbine 100. Further, the communication module 210 can include a sensor interface 212 (e.g., one or more analog-to-digital converters) to allow signals transmitted from the sensor(s) 158, 156 to be converted into signals that can be understood and processed by the processor(s) 206. It should be appreciated that the sensor(s) 158, 156 can be communicatively coupled to the communication module 210 using any suitable means. For example, the sensor(s) 158, 156 can be coupled to the sensor interface 212 via a wired connection. However, in other embodiments, the sensor(s) 158, 156 can be coupled to the sensor interface 212 via a wireless connection, such as by using any suitable wireless communication protocol known in the art. Further, the communication module 210 can also be operably coupled to an operating state control module 214 configured to change at least one wind turbine operating state.

[0124] As used herein, the term "processor" refers not only to integrated circuits designed specifically for control purposes, but also to programmable logic controllers (PLCs), microcontrollers, microcomputers, special-purpose computers, and other programmable circuits. Additionally, storage device(s) 208 can generally include storage elements, including, but not limited to, computer readable medium, such as random access memory (RAM), computer readable nonvolatile memory, such as flash memory, floppy disks, optical disks, and / or other suitable storage elements. Such storage device(s) 208 can generally be configured to store suitable computer readable instructions that, when implemented by processor(s) 206, configure controller 200 to perform various functions, including, but not limited to, storing at least a portion of peak phase power generated by generator 118 in response to a transient event during a peak phase of an oscillation, and discharging at least a portion of the stored charge during a valley phase of the oscillation as described herein, as well as various other suitable computer-implemented functions.

[0125] With particular reference to Figure 6 -9, in embodiments, controller 200 of system 300 can receive an indication of a transient event 302 occurring in power grid 179. The transient grid event 302 can result in the generation of torsional vibrations within power transmission system 146 of wind turbine 100. In this regard, controller 200 can be configured to detect an oscillation 304 in power output 306 of wind turbine 100 during a transient grid event recovery phase (R GE ) following transient event 302. Oscillation 304 can include at least one peak phase 308 followed by a valley phase 310. Peak phase(s) 308 can be considered to be a portion of power output 306 that is greater than the power output prior to transient event 302 (e.g., pre-transient grid event (P GE) voltage 312, while the valley phase(s) 310 can be considered as a portion of the power output 306 that is less than the power output prior to the transient event 302. In response to detecting the oscillation 304, the controller 200 can store at least a portion of the peak phase power 314 (e.g., a portion of the power output 306 of the generator 118 generated during the peak phase(s) 308) in an energy storage device 436, which can be operatively coupled to the generator 118. Storing the portion of the peak phase power 314 in the energy storage device 436 can establish a stored charge 316 in the energy storage device 436. The system 300 can release at least a portion 318 of the stored charge 316 to the power grid 179 during the valley phase(s) 310 of the oscillation 304. Releasing the portion 318 of the stored charge 316 can reduce an amplitude 320 of the oscillation 304 of the power output 306 (e.g., delivered power 322) delivered to the power grid 179.

[0126] In embodiments, the transient grid event 302 can be a zero voltage ride through (ZVRT) event, a low voltage ride through (LVRT) event, and / or a high voltage ride through (HVRT) event, where a rapid change in voltage aspect of the power grid 179 or an effect thereof is detected such as by the grid sensor(s) 156. For example, in embodiments, the LVRT event can be characterized by a voltage reduction that is at least 50% of the pre-transient grid event (P GE ) voltage. In additional embodiments, the voltage reduction can be less than or equal to 70% of the pre-transient grid event (P GE ) voltage. It should be appreciated that, in embodiments, maintaining at least 30% of the pre-transient grid event (P GE ) voltage 312 throughout the transient grid event 302 can facilitate recovery of the wind turbine 100 from the transient grid event 302, as the maintained voltage can provide an initial resistance against which generator torque can be generated and increased.

[0127] In embodiments, the transient event 302 can be detected by the controller 200 based on data received from a sensor (e.g., the grid sensor 156) indicative of the transient event 302. In such embodiments, the grid sensor 156 can be operatively coupled between a line side of the power converter 408 and a point of interconnection with the power grid 179. For example, the data received by the controller 200 can be indicative of a rapid change in voltage aspect of the power grid 179.

[0128] In embodiments, the transient event 302 can be detected by the controller 200 based on a change in powertrain torque 303 of the wind turbine 100. For example, in embodiments, the controller 200 can receive data indicative of a plurality of operating parameters 301 from the operating sensor(s) 158. In embodiments, the plurality of operating parameters 301 can correspond to operating parameters of the rotor 108 and / or the generator 118. For example, the plurality of operating parameters 301 can be indicative of rotor speed, rotor angular displacement, rotor angular acceleration, generator speed, generator angular displacement, and / or generator angular acceleration. Accordingly, the controller 200 can utilize the plurality of operating parameters 301 to determine a change in powertrain torque 303, which can be indicative of the transient event 302.

[0129] In response to the transient grid event 302, in embodiments, the controller 200 can generate a damping torque command 324 via the powertrain damper control module 216. The damping torque command 324 can establish a default damping level 326 of torsional vibrations caused by the transient grid event 302. The damping torque command 324 can be calculated to increase the natural damping of the powertrain 146, thereby reducing the magnitude, frequency, and / or duration of the torsional vibrations. However, it should be appreciated that the oscillations 304 in the power output 306 can persist until the torsional vibrations are reduced to a pre-transient grid event (P GE ) vibration level.

[0130] To reduce the amplitude 320 of the oscillations 304 in the delivered power 322, in embodiments, the controller 200 can determine an upper threshold 328 of deviation for the power output 306 of the wind turbine 100 relative to the power output / power level of the wind turbine 100 prior to the transient event 302. In embodiments, the controller 200 can also determine a lower threshold 330 of deviation for the power output 306 relative to the power output prior to the transient event 302. The upper threshold 328 and the lower threshold 330 can define an oscillation tolerance band 332.

[0131] As depicted at 329, in embodiments, the controller 200 can determine a portion of the peak phase power 314 that exceeds the upper threshold 328. In embodiments, the portion of the peak phase power 314 that is stored via the energy storage device 436 can be the portion of the peak phase power 314 that exceeds the upper threshold 328, as particularly depicted in FIG. 9. In other words, the amount of power generated by the generator 118 during the peak phase(s) 308 that would exceed the grid limit (e.g., the upper threshold 328) if delivered to the grid can be diverted to the energy storage device 436, while the remainder of the power generated during the peak phase(s) 308 is delivered to the grid 179. Figure 8

[0132] ​As depicted at 331, in embodiments, the controller 200 can determine a portion of the valley phase power 334 that is below the lower threshold 330. In embodiments, the portion 318 of the stored charge 316 discharged can correspond to the portion of the valley phase power 334 that is below the lower threshold 330. In such embodiments, the valley phase power 334 can correspond to a portion of the power output 306 generated during the valley phase(s) 310 of the oscillation 304. In other words, by discharging the portion 318 of the stored charge 316 when the power generated by the generator 118 is below the minimum demand (e.g., the lower threshold 330), the system 300 can prevent the power grid 179 from detecting (e.g., seeing) an unacceptable drop in the power output 306.

[0133] In embodiments, the upper threshold 328 and the lower threshold 330 can be a first upper threshold and a first lower threshold that are applied at a first interval 336 after the transient event 302. In such embodiments, the system 300 can determine a second upper threshold 338 and a second lower threshold 340 for the power output 306 relative to the power output of the wind turbine 100 prior to the transient event 302. In embodiments, the second upper threshold 338 and the second lower threshold 340 can be applied at a second interval 342 after the first interval 336. The second upper threshold 338 and the second lower threshold 340 can have a smaller deviation from the power output prior to the transient event 302 than the first upper threshold 328 and the first lower threshold 330. It should be appreciated that the second upper threshold 338 and the second lower threshold 340 can facilitate compliance with the power grid 179 demands, necessitating a more stable power output 306 as time elapses from the transient event 302.

[0134] It should also be appreciated that the utilization of the first set of thresholds 328, 330 and the second set of thresholds 338, 340 can facilitate a more customized control scheme that can not be available with only a single set of thresholds. For example, in embodiments, if the more restrictive second upper threshold 330 and the second lower threshold 340 were implemented at the beginning of the transient grid event recovery phase (R GE ) the magnitude of the portion of the peak phase power 314 diverted to the energy storage device 436 can exceed the capacity of the components of the wind turbine 100.

[0135] As depicted at 344, the controller 200 can be configured to determine a magnitude of the amplitude 320 of the oscillation 304 (e.g., the power output 306 versus the pre-transient grid event (P GEwhether the deviation of the power output 306 is within the oscillation tolerance band 332. In embodiments in which the oscillation 304 exceeds the oscillation tolerance band 332, the controller 200 can repeat the storing and discharging steps of the system 300 for subsequent oscillations until the deviation of the power output 306 remains within the oscillation tolerance band 332. However, in embodiments in which the deviation of the power output 306 of the wind turbine 100 remains within the oscillation tolerance band 332, the controller can discharge the remaining portion 346 of the stored charge 316 to the power grid 179.

[0136] An exemplary operation of an embodiment of the system 300 is depicted in FIG. 9. As depicted, in embodiments in which control of the system 300 is not omitted, Figure 9A represents the oscillation 304 of the power output 306. In this regard, Figure 9A may represent the natural power output 306 of the wind turbine 100 in response to the transient event 302. In contrast, Figure 9B depicts a portion of the peak phase power 314 that can be stored via the energy storage device 436 during the peak phase 308, and a corresponding portion 318 of the stored charge 316 that can be discharged during the corresponding valley phase 310. As Figure 9B depicted in FIG. 8, in embodiments, the storing and discharging steps of the system 300 can be repeated for subsequent oscillations until the deviation of the power output 306 of the wind turbine 100 remains within the oscillation tolerance band 332. In embodiments, Figure 9C may represent the effect of the system 300 on the delivered power 322. As Figure 9C depicted in FIG. 8, in embodiments, any portion of the peak phase power 314 that can exceed the upper threshold 328 can not be delivered to the power grid 179, and the power output 306 can be increased by the stored charge 316 such that the delivered power 322 remains above the lower threshold 330. Thus, the delivered power 322 can comply with grid demands to control the deviation in the power output 306 of the wind turbine 100. It should be appreciated that, Figure 9C the waveforms depicted in FIG. 8 are not intended to limit the delivered power 322 to a particular waveform. Rather, Figure 9C indicates that the delivered power 322 (as experienced by the power grid 179) can remain between the upper threshold 328 and the lower threshold 330. For example, in embodiments, the delivered power 322 (as experienced by the power grid 179) can have a sinusoidal or other suitable waveform with a reduced amplitude 320.

[0137] again with particular reference to Figure 6In embodiments, discharging the portion 318 of the stored charge 316 can include determining a duration 348 of the valley phase(s) 310. Based on the determination, the controller 200 can synchronize a discharging duration 350 of the portion 318 of the stored charge 316 with the duration 348 of the valley phase(s) 310. It should be appreciated that synchronizing the discharging duration 350 with the duration 348 of the valley phase(s) 310 can limit the increase in the output power 306 to a period in which the power output 306 is below the pre-transient grid event (P GE ) voltage 312, and thus to a period in which the increase can be beneficial.

[0138] In embodiments, the controller 200 can determine a slope rate 352 and an amplitude 320 of the oscillation 304 during the valley phase(s) 310. As depicted at 354, in embodiments, the controller 200 can synchronize the discharging of the portion 318 of the stored charge 316 with the slope rate 352 and the amplitude 320 of the oscillation 304 during the valley phase(s) 310. For example, in embodiments, the discharging of the portion 318 of the stored charge 316 can determine a shape that conforms to a shape of the oscillation 304 during the valley phase(s) 310. In other words, synchronizing the discharging in the manner described can facilitate providing only as much power as is needed to increase the power output 306 at each instant of the valley phase(s) 310. It should also be appreciated that discharging the portion 318 of the stored charge 316 without synchronizing the discharging with the oscillation 304 can result in discharging excess or insufficient portions of the stored charge 316 relative to an additional amount of power needed to increase the power output 306 in order to meet the demands of the power grid 179.

[0139] As shown in Figure 7 , additional aspects of the system 300 can be incorporated within Block Bl as depicted by Figure 6 . In this regard, as depicted at 356, in embodiments, the system 300 can include determining, via the oscillation compensation control module 218 of the controller 200, a magnitude of a portion of the peak phase power 314 stored by the energy storage device 436 in response to detection of the oscillation 304. As depicted at 358, in embodiments, the oscillation compensation control module 218 can also determine a magnitude of the portion 318 of the stored charge 316 to discharge upon detection of the valley phase(s) 310. Based on the determined magnitudes of the stored charge 316 and the discharging portion 318, the oscillation compensation control module 218 can generate a setpoint command for the line side converter 414 of the power converter 408 of the wind turbine 100 that is calculated to achieve the determined magnitudes.

[0140] In embodiments, the oscillation compensation control module 218 can receive a plurality of operating parameters 301 from the operating sensor(s) 158 and a damping torque command 324 from the drivetrain damper control module 216. In embodiments, the plurality of operating parameters 301 can be indicative of a slip magnitude, a generator speed, and a plurality of voltages and currents. The plurality of voltages and currents can include stator voltages and currents, rotor voltages and currents, and line side voltages and currents at each of the three phases.

[0141] Based on one or more of the operating parameters 301 and the damping torque command 324, the oscillation compensation control module 218 can determine, in embodiments, a plurality of oscillation parameters 362 for the power output 306. The plurality of oscillation parameters 362 can describe characteristics of the oscillation 304. The plurality of oscillation parameters 362 for the power output 306 of the wind turbine 100 can be determined based on the slip magnitude, the generator speed, and the damping torque command 324.

[0142] As depicted at 364, in embodiments, the oscillation compensation control module 218 can filter the plurality of oscillation parameters 362 in order to obtain a plurality of oscillation power components 366. The plurality of oscillation components 366 can include a stator oscillation power 368, a rotor oscillation power 370, and a line side oscillation power 372. Thus, in embodiments, the oscillation compensation control module 218 can determine a magnitude of a portion of the peak phase power 314 stored by the energy storage device 436 based at least in part on at least one of the plurality of oscillation power components 366.

[0143] As depicted at 374, in embodiments, the oscillation compensation control module 218 can determine a magnitude of the transient event 302 based on the plurality of operating parameters 301. In embodiments, the magnitude of the transient event 302 can be compared to a magnitude threshold 378 at 376. In embodiments where the magnitude of the transient event 302 does not exceed the magnitude threshold 378, the oscillation compensation control module 218 can initiate a first operating mode 380. As depicted at 382, the first operating mode 380 can include storing and discharging the rotor oscillation power 370. In embodiments where the magnitude of the transient event 302 exceeds the magnitude threshold 378, the oscillation compensation control module 218 can initiate a second operating mode 384. As depicted at 386, the second operating mode 384 can include storing and discharging both the rotor oscillation power 370 and the stator oscillation power 368. It should be appreciated that the use of the first operating mode 380 and the second operating mode 384 can facilitate the storage and discharge steps to be tailored to the magnitude of the transient event 374 and, thus, to the resulting oscillation 304.

[0144] Furthermore, those skilled in the art will recognize that the herein described components (operations, materials, acts, etc.) can be combined in a manner not specifically described herein. For example, features from one embodiment can be combined with features from another embodiment. Similarly, features from a particular embodiment can be left out of an implementation of the application while other features are included in the implementation. In addition, features or aspects of the application can be practiced automatically and without human intervention. Further, those skilled in the art will recognize or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments described herein. It is therefore intended that the application not be limited to the specifically described embodiments and embodiments herein, but that the application be considered to extend to all alternative and equivalents as would be recognized by one skilled in the art.

[0145] This written description uses examples to disclose the application (including the best mode), and also to enable any person skilled in the art to practice the application, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the application is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to fall 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

[0146] Further aspects of the application are provided by the subject matter of the following clauses:

[0147] Clause 1. A method for controlling a wind turbine connected to a power grid, the wind turbine comprising a generator, the method comprising: receiving, via a controller, an indication of a transient event occurring in the power grid; detecting, via the controller, an oscillation in a power output of the wind turbine during a transient event recovery phase following the transient event, the oscillation comprising a peak phase followed by a valley phase with respect to the power output before the transient event; in response to detecting the oscillation, storing at least a portion of a peak phase power in an energy storage device, the energy storage device operably coupled to the generator, to establish a stored charge, wherein the peak phase power corresponds to a power output during the peak phase; and discharging at least a portion of the stored charge to the power grid during the valley phase of the oscillation to reduce an amplitude of the oscillation of the power output delivered to the power grid.

[0148] Clause 2. The method of clause 1, wherein discharging the at least a portion of the stored charge further comprises: determining, via the controller, a duration of the valley phase; and synchronizing a duration of the discharging of the portion of the stored charge with the duration of the valley phase.

[0149] Clause 3. The method of any preceding clause, further comprising: determining, via the controller, a slope rate and an amplitude of the oscillation during the valley phase; and synchronizing the discharging of the portion of the stored charge with the slope rate and the amplitude of the oscillation during the valley phase.

[0150] Clause 4. The method of any preceding clause, further comprising: determining an upper threshold and a lower threshold of a deviation of the power output of the wind turbine relative to the power output of the wind turbine prior to the transient event, the upper threshold and the lower threshold defining an oscillation tolerance band, and wherein the portion of the peak phase power stored via the energy storage device is a portion of the peak phase power that exceeds the upper threshold; determining, via the controller, a portion of the valley phase power that is below the lower threshold, wherein the portion of the stored charge discharged corresponds to the portion of the valley phase power that is below the lower threshold, wherein the valley phase power corresponds to a portion of power output during the valley phase; and repeating the storing and discharging steps for subsequent oscillations until the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0151] Clause 5. The method of any preceding clause, wherein the upper threshold and the lower threshold are a first upper threshold and a first lower threshold that are applied at a first interval after the transient event, the method further comprising: determining a second upper threshold and a second lower threshold of the power output of the wind turbine relative to the power output prior to the transient event, wherein the second upper threshold and the second lower threshold are applied at a second interval after the first interval and have a smaller deviation from the power output prior to the transient event than the first upper threshold and the first lower threshold.

[0152] Clause 6. The method of any preceding clause, further comprising: discharging a remaining portion of the stored charge to the power grid at a remaining discharge rate when the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0153] Clause 7. The method of any preceding clause, further comprising: determining, via an oscillation compensation control module of the controller, a magnitude of the portion of the peak phase power stored by the energy storage device in response to the detection of the oscillation; determining, via the oscillation compensation control module, a magnitude of the portion of the stored charge discharged at the detection of the valley phase; and generating, via the oscillation compensation control module, a setpoint command for a line side converter of a power converter of the wind turbine in order to obtain the determined stored charge and discharge.

[0154] Clause 8. The method of any preceding clause, further comprising: receiving, via the oscillation compensation control module, a plurality of operating parameters; receiving, via the oscillation compensation control module, a damping torque command from a drivetrain damping system of the wind turbine; determining, via the oscillation compensation control module, a plurality of oscillation parameters for the power output of the wind turbine based on one or more of the operating parameters and the damping torque command; filtering, via the oscillation compensation control module, the plurality of oscillation parameters to obtain a plurality of oscillation power components, the plurality of oscillation power components comprising at least one of a stator oscillation power, a rotor oscillation power, and a line side oscillation power; and determining, via the oscillation compensation control module, a magnitude of the portion of the peak stage power to be stored by the energy storage device based at least in part on at least one of the plurality of oscillation power components.

[0155] Clause 9. The method of claim 8, further comprising: determining, via the oscillation compensation control module, a magnitude of the transient event based on the plurality of operating parameters; and initiating, via the oscillation compensation control module, one of a first operating mode or a second operating mode based on the magnitude of the transient event, wherein the first operating mode comprises storing and discharging the rotor oscillation power, and wherein the second operating mode comprises storing and discharging both the rotor oscillation power and the stator oscillation power.

[0156] Clause 10. The method of any preceding clause, wherein the plurality of operating parameters are indicative of a slip magnitude, a generator speed, and a plurality of voltages and currents, the plurality of voltages and currents comprising a stator voltage and current, a rotor voltage and current, and a line side voltage and current at each of a three-phase power, and wherein determining the plurality of oscillation parameters for the power output of the wind turbine is based on the slip magnitude, the generator speed, and the damping torque command.

[0157] Clause 11. The method of any preceding clause, wherein the energy storage device comprises at least one of a battery and a supercapacitor.

[0158] Clause 12. The method of any preceding clause, wherein receiving the indication of the transient event occurring in the power grid further comprises: receiving, via the controller, data indicative of the transient event from a sensor operably coupled between a line side of a power converter of the wind turbine and a point of interconnection with the power grid.

[0159] Clause 13. The method of any preceding clause, wherein the transient event comprises one of a zero voltage ride through event, a low voltage ride through event, and a high voltage ride through event.

[0160] Clause 14. The method of any preceding clause, wherein receiving the indication of the transient event further comprises detecting, via the controller, a change in a drivetrain torque aspect of the wind turbine indicative of the transient event.

[0161] Clause 15. A system for controlling a wind turbine connected to a power grid, the system comprising: a generator operably coupled to an energy storage device; and a controller communicatively coupled to the generator, the controller comprising at least one processor configured to perform a plurality of operations, the plurality of operations comprising: receiving an indication of a transient event occurring in the power grid, detecting an oscillation in a power output of the wind turbine during a transient event recovery phase following the transient event, the oscillation comprising a peak phase followed by a trough phase with respect to the power output before the transient event, in response to detecting the oscillation, storing at least a portion of the power output during the peak phase in an energy storage device, the energy storage device operably coupled to the generator to build a stored charge, and during the trough phase of the oscillation, discharging at least a portion of the stored charge to the power grid in order to reduce an amplitude of the oscillation of the power output delivered to the power grid.

[0162] Clause 16. The system of any preceding clause, wherein discharging at least a portion of the stored charge further comprises: determining a duration of the trough phase; and synchronizing a duration of the discharging of the portion of the stored charge with the duration of the trough phase.

[0163] Clause 17. The system of any preceding clause, wherein the plurality of operations further comprise: determining an upper threshold and a lower threshold of a deviation of the power output of the wind turbine with respect to the power output of the wind turbine before the transient event, the upper threshold and the lower threshold defining an oscillation tolerance band, wherein the portion of the peak phase power stored via the energy storage device is a portion of the peak phase power that exceeds the upper threshold; determining a portion of the trough phase power that is below the lower threshold, wherein the portion of the stored charge discharged corresponds to the portion of the trough phase power that is below the lower threshold; and repeating the storing and discharging steps for subsequent oscillations until the deviation of the power output of the wind turbine remains within the oscillation tolerance band.

[0164] Clause 18. The system of any preceding clause, wherein the plurality of operations further comprise: determining a magnitude of the portion of the peak phase power stored by the energy storage device; determining the amount of stored charge to release at the detection of the valley phase; and generating a setpoint command for a line side converter of a power converter of the wind turbine in order to obtain the determined stored charge and release.

[0165] Clause 19. The system of any preceding clause, wherein the plurality of operations further comprise: receiving a plurality of operating parameters indicative of a slip magnitude, a generator speed, and a plurality of voltages and currents, the plurality of voltages and currents including a stator voltage and current, a rotor voltage and current, and a line side voltage and current at each of three-phase power; receiving a damping torque command from a drivetrain damping system of the wind turbine; determining a plurality of oscillation parameters for the power output of the wind turbine based on the slip magnitude, the generator speed, and the damping torque command; filtering, via the oscillation compensation control module, the plurality of oscillation parameters to obtain a plurality of oscillation power components, the plurality of oscillation power components including at least one of a stator oscillation power, a rotor oscillation power, and a line side oscillation power; and determining, via the oscillation compensation control module, a magnitude of the portion of the peak phase power stored by the energy storage device based at least in part on at least one of the plurality of oscillation power components.

[0166] Clause 20. The system of any preceding clause, wherein the plurality of operations further comprise: determining, via the control module, a magnitude of the transient event based on the plurality of operating parameters; and initiating, via the control module, one of a first operating mode or a second operating mode based on the magnitude of the transient event, wherein the first operating mode includes storing and releasing the rotor oscillation power, and wherein the second operating mode includes storing and releasing both the rotor oscillation power and the stator oscillation power.

Claims

1. A method for controlling a wind turbine connected to a power grid, the wind turbine including a generator, the method comprising: The controller receives indications of transient events occurring in the power grid. During the transient event recovery phase following the transient event, oscillations in the power output of the wind turbine are detected via the controller, the oscillations including a peak phase followed by a trough phase; In response to detecting the oscillation, at least a portion of the peak-phase power is stored in an energy storage device operatively coupled to the generator to establish stored charge, wherein the peak-phase power corresponds to the power output during the peak phase; and During the trough phase of the oscillation, at least a portion of the stored charge is released to the power grid in order to reduce the amplitude of the oscillation in the power output supplied to the power grid; An upper threshold and a lower threshold are determined for the deviation of the power output of the wind turbine relative to the power output of the wind turbine prior to the transient event, the upper threshold and the lower threshold defining an oscillation tolerance band, and wherein the portion of the peak stage power stored via the energy storage device is the portion of the peak stage power exceeding the upper threshold; The controller determines a portion of the power during a valley phase below a lower threshold, wherein the portion of the released stored charge corresponds to the portion of the power during the valley phase below the lower threshold, and wherein the valley phase power corresponds to the power output portion during the valley phase; and The storage and release steps are repeated in response to subsequent oscillations until the deviation in the power output of the wind turbine remains within the oscillation tolerance band.

2. The method according to claim 1, wherein, The release of at least said portion of the stored charge further includes: The duration of the valley phase is determined via the controller; and The duration of the release of the portion of the stored charge is synchronized with the duration of the valley phase.

3. The method according to claim 2, further comprising: The slope and amplitude of the oscillation during the valley phase are determined via the controller; as well as The release of the portion of the stored charge is synchronized with the slope and amplitude of the oscillation during the valley phase.

4. The method according to claim 1, wherein, The upper and lower thresholds are a first upper threshold and a first lower threshold, which are applied at a first interval after the transient event. The method further includes: A second upper threshold and a second lower threshold are determined for the power output of the wind turbine relative to the power output prior to the transient event, wherein the second upper threshold and the second lower threshold are applied at a second interval after the first interval and have a smaller deviation from the power output prior to the transient event compared to the first upper threshold and the first lower threshold.

5. The method according to claim 1, further comprising: When the deviation of the power output of the wind turbine remains within the oscillation tolerance band, the remaining portion of the stored charge is discharged to the power grid at the residual discharge rate.

6. The method according to claim 1, further comprising: In response to the detection of the oscillation, the magnitude of the portion of the peak stage power stored by the energy storage device is determined via the oscillation compensation control module of the controller; The oscillation compensation control module determines the magnitude of the portion of the stored charge released during the detection in the valley phase. as well as The oscillation compensation control module generates a setpoint command for the line-side converter of the power converter of the wind turbine to obtain the determined stored charge and discharge.

7. The method according to claim 6, further comprising: Multiple operating parameters are received via the oscillation compensation control module; The damping torque command is received from the power transmission system damping system of the wind turbine via the oscillation compensation control module. The oscillation compensation control module determines multiple oscillation parameters for the power output of the wind turbine based on one or more of the operating parameters and the damping torque command. The oscillation compensation control module filters the multiple oscillation parameters to obtain multiple oscillation power components, which include at least one of stator oscillation power, rotor oscillation power, and line-side oscillation power. as well as The magnitude of the portion of the peak stage power stored by the energy storage device is determined, at least in part, based on at least one of the plurality of oscillation power components, via the oscillation compensation control module.

8. The method according to claim 7, further comprising: The magnitude of the transient event is determined by the oscillation compensation control module based on the multiple operating parameters. as well as The oscillation compensation control module initiates one of a first operating mode or a second operating mode based on the magnitude of the transient event, wherein the first operating mode includes storing and releasing the rotor oscillation power, and wherein the second operating mode includes storing and releasing both the rotor oscillation power and the stator oscillation power.

9. The method according to claim 7, wherein, The plurality of operating parameters indicate slip value, generator speed, and a plurality of voltages and currents, including stator voltage and current, rotor voltage and current, and line-side voltage and current at each of the three-phase power, wherein the plurality of oscillation parameters for determining the power output of the wind turbine are based on the slip value, the generator speed, and the damping torque command.

10. The method according to claim 1, wherein, The energy storage device includes at least one of a battery and a supercapacitor.

11. The method according to claim 1, wherein, The indication of receiving the transient event occurring in the power grid further includes: The controller receives data indicating the transient event from a sensor operatively coupled between the line side of the power converter of the wind turbine and the point of interconnection with the power grid.

12. The method according to claim 11, wherein, The transient events include one of the following: zero-voltage ride-through event, low-voltage ride-through event, and high-voltage ride-through event.

13. The method according to claim 1, wherein, The indication of receiving the transient event further includes: The controller detects changes in the torque of the power transmission system of the wind turbine, which indicate the transient event.

14. A system for controlling a wind turbine connected to a power grid, the system comprising: A generator that is operatively coupled to an energy storage device; as well as A controller communicatively coupled to the generator, the controller including at least one processor configured to perform a plurality of operations, the plurality of operations including: Receive indications of transient events occurring in the power grid. During the transient event recovery phase following the transient event, oscillations in the power output of the wind turbine are detected, the oscillations including a peak phase followed by a trough phase. In response to detecting the oscillation, at least a portion of the peak-phase power is stored in an energy storage device operatively coupled to the generator to establish stored charge, wherein the peak-phase power corresponds to the power output during the peak phase, and During the trough phase of the oscillation, at least a portion of the stored charge is released to the power grid in order to reduce the amplitude of the oscillation in the power output supplied to the power grid; An upper threshold and a lower threshold are determined for the deviation of the power output of the wind turbine relative to the power output of the wind turbine prior to the transient event, the upper threshold and the lower threshold defining an oscillation tolerance band, wherein the portion of the peak stage power stored via the energy storage device is the portion of the peak stage power exceeding the upper threshold; Determine the portion of the power during the valley phase below the lower threshold, wherein the portion of the released stored charge corresponds to the portion of the power during the valley phase below the lower threshold, wherein the valley phase power corresponds to the power output portion during the valley phase; and The storage and release steps are repeated in response to subsequent oscillations until the deviation in the power output of the wind turbine remains within the oscillation tolerance band.

15. The system according to claim 14, wherein, The release of at least said portion of the stored charge further includes: Determine the duration of the valley phase; and The duration of the release of the portion of the stored charge is synchronized with the duration of the valley phase.

16. The system according to claim 14, wherein, The plurality of operations also include: Determine the magnitude of the portion of the peak stage power stored by the energy storage device; Determine the amount of stored charge released during the detection at the valley stage; and Generate a setpoint command for the line-side converter of the power converter for the wind turbine in order to obtain the determined stored charge and discharge.

17. The system according to claim 16, wherein, The plurality of operations also include: Receives an indication of slip value, generator speed, and multiple operating parameters including stator voltage and current, rotor voltage and current, and line-side voltage and current at each of the three-phase power components; Receive damping torque command from the power transmission system damping system of the wind turbine; Multiple oscillation parameters for the power output of the wind turbine are determined based on the slip value, the generator speed, and the damping torque command. The oscillation compensation control module filters the multiple oscillation parameters to obtain multiple oscillation power components, which include at least one of stator oscillation power, rotor oscillation power, and line-side oscillation power; and The magnitude of the portion of the peak stage power stored by the energy storage device is determined, at least in part, based on at least one of the plurality of oscillation power components, via the oscillation compensation control module.

18. The system according to claim 17, wherein, The plurality of operations also include: The magnitude of the transient event is determined based on the plurality of operating parameters via the oscillation compensation control module; and The oscillation compensation control module initiates one of a first operating mode or a second operating mode based on the magnitude of the transient event, wherein the first operating mode includes storing and releasing the rotor oscillation power, and wherein the second operating mode includes storing and releasing both the rotor oscillation power and the stator oscillation power.

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