System and method for providing speed-dependent grid frequency support in grid-forming inverter-based resources

Abstract

A method for constraining grid frequency support of a wind turbine connected to a power grid to prevent trip events in the wind turbine includes receiving, via a controller, one or more speed feedback signals from the wind turbine. Further, the method includes adjusting, via the controller, one or more parameters of a power conditioner of the wind turbine based on the one or more speed feedback signals such that a power output of the wind turbine is less sensitive to a change in at least one of the grid frequency or the phase angle.

Description

Technical Field

[0001] The present disclosure generally relates to wind turbines, and more particularly, to systems and methods for providing speed-related grid frequency support in grid-forming wind turbines. Background Art

[0002] Wind power is considered to be one of the cleanest and most environmentally friendly energy sources currently available, and wind turbines have received increasing attention in this regard. Modern wind turbines typically include a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture the kinetic energy of the wind using known airfoil principles. For example, the rotor blades typically have a cross-sectional profile of an airfoil such that during operation, air flows over the blade, creating a pressure difference between the sides. Thus, a lift force acting from the pressure side towards the suction side acts on the blade. The lift force generates torque on the main rotor shaft, which is typically gear-connected to a generator for generating electricity.

[0003] Wind turbines can be classified into two types: fixed-speed turbines and variable-speed turbines. Conventionally, variable-speed wind turbines are controlled as current sources connected to the power grid. In other words, variable-speed wind turbines rely on the grid frequency detected by a phase-locked loop (PLL) as a reference and inject a specified amount of current into the grid. The conventional current source control of wind turbines is based on the assumption that the grid voltage waveform is a fundamental voltage waveform with a fixed frequency and amplitude, and the penetration of wind power into the grid is low enough so as not to cause disturbances to the grid voltage amplitude and frequency. Therefore, the wind turbine injects a specified current into the grid only based on the fundamental voltage waveform. However, with the rapid growth of wind power, the penetration of wind power into some grids has increased to a point where wind turbine generators have a significant impact on the grid voltage and frequency. When a wind turbine is located in a weak grid, wind turbine power fluctuations can cause an increase in the amplitude and frequency variations of the grid voltage. These fluctuations can adversely affect the performance and stability of the PLL and wind turbine current control.

[0004] In addition, many existing renewable power generation converters (such as doubly-fed wind turbine generators) operate in a "grid-following" mode. Grid-following type devices utilize fast current regulation loops to control the active and reactive power exchanged with the grid. More specifically, Figure 1Shows the basic elements of the main circuit and converter control structure for a grid-following doubly-fed wind turbine generator. As shown, the active power reference of the converter is developed by an energy source regulator (e.g., the turbine control section of the wind turbine). This active power reference is transmitted as a torque reference, which represents the lesser of the maximum available power from the energy source at that instant or a curtailment command from a higher-level grid controller. The converter control then determines the current reference for the active component of the current to achieve the desired torque. Thus, the doubly-fed wind turbine generator includes a function to manage voltage and reactive power in a way that results in a command for the reactive component of the current. The wide-bandwidth current regulator then develops the command for the voltage applied to the system by the converter such that the actual current closely tracks the command.

[0005] Alternatively, a grid-forming type of converter provides a voltage source characteristic where the angle and magnitude of the voltage are controlled to achieve the regulation functions required by the grid. With this configuration, the current will flow according to the needs of the grid, and the converter helps to establish the voltage and frequency for the grid. This characteristic is comparable to that of a conventional generator based on a turbine driving a synchronous machine. Thus, a grid-forming source must include the following basic functions: (1) support the grid voltage and frequency for any current flow (both real and reactive) within the ratings of the equipment; (2) prevent operation beyond the voltage or current capabilities of the equipment by allowing the grid voltage or frequency to vary rather than disconnecting the equipment (disconnection is only allowed if the voltage or frequency exceeds the bounds established by the grid entity); (3) remain stable for any grid configuration or load characteristic, including serving isolated loads or connecting to other grid-forming sources and switching between such configurations; (4) share the total load of the grid among other grid-forming sources connected to the grid; (5) overcome major and minor grid disturbances, and (6) meet requirements (1)-(5) without requiring fast communication with other control systems present in the grid or externally created logic signals related to changes in the grid configuration.

[0006] The basic control structure for achieving the above grid-forming objectives was developed in the early 1990s and field-validated for battery systems (see, for example, U.S. Patent No. 5,798,633 titled "Battery Energy Storage Power Conditioning System"). Applications related to full-converter wind turbines and solar generators are disclosed in U.S. Publication No. 2010 / 0142237 titled "System and Method for Control of a Grid Connected Power Generating System" and U.S. Patent No. 9,270,194 titled "Controller for controlling a power converter". However, such implementations are employed on full-converter wind turbines.

[0007] Grid-forming wind turbines enhance grid stability by automatically changing their power output in response to grid frequency and phase changes. However, based on the operating point of the wind turbine, the ability of the wind turbine to supply such support can be limited. For example, at low rotor speeds where the wind turbine is operating near its lower speed limit, a small increase in grid-induced power can cause a speed decrease sufficient to cause a low-speed trip.

[0008] In view of the foregoing, systems and methods for solving the previously mentioned problems would be welcome in the art. Accordingly, the present disclosure relates to systems and methods for constraining grid frequency support in a wind turbine when the wind turbine does not have sufficient kinetic energy or energy input from the wind to avoid these grid-induced low-speed trips while maintaining the grid-forming characteristics of the wind turbine. Summary of the Invention

[0009] Aspects and advantages of the present invention will be set forth in part in the following description, or may be obvious from the description, or may be learned by practice of the present invention.

[0010] The present disclosure relates to a method for constraining grid frequency support of a wind turbine connected to an electric power grid to prevent trip events in the wind turbine. The method includes receiving, via a controller, one or more speed feedback signals from the wind turbine. Additionally, the method includes adjusting, via the controller, one or more parameters of a power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of grid frequency or phase angle.

[0011] In another aspect, the present disclosure relates to a power regulator configured to constrain the grid frequency support of a wind turbine connected to an electrical grid to prevent a tripping event in the wind turbine. The power regulator includes a controller that includes at least one processor. The (multiple) processors are configured to perform a plurality of operations including, but not limited to, receiving one or more speed feedback signals from the wind turbine and adjusting one or more parameters of the power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or phase angle.

[0012] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] A complete and open disclosure of the invention, including the best mode thereof for those of ordinary skill in the art, is set forth in the specification, which makes reference to the accompanying drawings, in which:

[0014] Figure 1 shows a single-line diagram of a doubly-fed wind turbine generator having a converter control structure for grid-following applications according to a conventional configuration;

[0015] Figure 2 shows a perspective view of an embodiment of a wind turbine according to the present disclosure;

[0016] Figure 3 shows a simplified internal view of an embodiment of a nacelle according to the present disclosure;

[0017] Figure 4 shows a schematic diagram of an embodiment of a wind turbine electrical power system suitable for use with the Figure 1 wind turbine shown in;

[0018] Figure 5 shows a schematic diagram of another embodiment of a wind turbine electrical power system suitable for use with the Figure 1 wind turbine shown in;

[0019] Figure 6 shows a schematic diagram of an embodiment of a wind farm having multiple wind turbines according to the present disclosure;

[0020] Figure 7 shows a block diagram of an embodiment of a controller according to the present disclosure;

[0021] Figure 8 shows a single-line diagram of a doubly-fed wind turbine generator having converter control for grid-forming applications according to the present disclosure;

[0022] Figure 9 Shows a detailed block diagram of an embodiment of a power regulator according to the present disclosure;

[0023] Figure 10 Shows a flowchart of an embodiment of a method for constraining grid frequency support of a wind turbine connected to a power grid according to the present disclosure to prevent a tripping event in the wind turbine; and

[0024] Figure 11 Shows a schematic diagram of an embodiment of a system for making the power output of a wind turbine less sensitive to changes in grid frequency and / or phase angle by adjusting one or more gains of a power regulator of the wind turbine according to the present disclosure. Detailed Description

[0025] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention and not limitation of the invention. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features shown or described as part of one embodiment can be used with another embodiment to yield yet another embodiment. Accordingly, it is intended that the present invention cover such modifications and variations that come within the scope of the appended claims and their equivalents.

[0026] Grid-forming wind turbine generators enhance grid stability by automatically changing their power output in response to grid frequency and phase changes. However, based on the operating point of the wind turbine, the ability of the wind turbine to provide this support can be limited. For example, at low rotor speeds where the wind turbine is operating near its minimum speed limit, a small increase in grid-induced power can cause a speed decrease sufficient to cause a low-speed trip. Accordingly, the systems and methods of the present disclosure relate to constraining grid frequency support when the wind turbine does not have sufficient kinetic energy to avoid these grid-induced low-speed trips.

[0027] Now referring to the drawings, Figure 2A perspective view of a wind turbine 10 according to an embodiment of the present disclosure is shown. As shown, the wind turbine 10 generally includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to the hub 20 and extending outwardly therefrom. For example, in the illustrated embodiment, the rotor 18 includes three rotor blades 22. However, in alternative embodiments, the rotor 18 may include more or fewer than three rotor blades 22. Each rotor blade 22 may be spaced about the hub 20 to facilitate rotation of the rotor 18 such that kinetic energy can be converted from the wind into useful mechanical energy and subsequently electrical energy. For example, the hub 20 may be rotatably coupled to an electrical generator 24 ( Figure 3 ) positioned within the nacelle 16 to permit generation of electrical energy.

[0028] The wind turbine 10 may also include a wind turbine controller 26 centered within the nacelle 16. However, in other embodiments, the controller 26 may be located within any other component of the wind turbine 10 or at a location external to the wind turbine 10. Additionally, the controller 26 may be communicatively coupled to any number of components of the wind turbine 10 to control the operation of such components and / or to implement corrective or control actions. In this regard, the controller 26 may include a computer or other suitable processing unit. Accordingly, in several embodiments, the controller 26 may include suitable computer-readable instructions that, when implemented, configure the controller 26 to perform various different functions, such as receiving, transmitting, and / or executing wind turbine control signals. Thus, the controller 26 may generally be configured to control various operating modes (e.g., startup or shutdown sequences), derating or ramping of the wind turbine, and / or individual components of the wind turbine 10.

[0029] Now referring to Figure 2 , a simplified internal view of an embodiment of the nacelle 16 of the wind turbine 10 shown in Figure 1 is shown. As shown, the generator 24 may be disposed within the nacelle 16 and supported on top of a bottom plate 46. Generally, the generator 24 may be coupled to the rotor 18 for generating electrical power from the rotational energy generated by the rotor 18. For example, as shown in the illustrated embodiment, the rotor 18 may include a rotor shaft 34 that is coupled to the hub 20 for rotation therewith. The rotor shaft 34 may in turn be rotatably coupled to a generator shaft 36 of the generator 24 via a gearbox 38. As generally understood, the rotor shaft 34 may provide a low-speed high-torque input to the gearbox 38 in response to rotation of the rotor blades 22 and the hub 20. The gearbox 38 may then be configured to transform the low-speed high-torque input into a high-speed low-torque output to drive the generator shaft 36 and thus the generator 24.

[0030] The wind turbine 10 may also include one or more pitch drive mechanisms 32 communicatively coupled to the wind turbine controller 26, where each pitch adjustment mechanism 32 is configured to rotate the pitch bearing 40 and thus the individual rotor blades 22 about their respective pitch axes 28. Additionally, as shown, the wind turbine 10 may include one or more yaw drive mechanisms 42 configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging the yaw bearing 44 of the wind turbine 10 disposed between the nacelle 16 and the tower 12 of the wind turbine 10).

[0031] Additionally, the wind turbine 10 may also include one or more sensors 66, 68 for monitoring various wind conditions of the wind turbine 10. For example, the incoming wind direction 52, wind speed, or any other suitable wind condition near the wind turbine 10 may be measured, such as by using a suitable weather sensor 66. Suitable weather sensors may include, for example, light detection and ranging (“lidar”) devices, acoustic detection and ranging (“sodar”) devices, anemometers, wind vanes, barometers, radar devices (such as Doppler radar devices), or any other sensing device known or later developed in the art that can provide wind direction information. As described herein, additional sensors 68 may also be utilized to measure additional operating parameters of the wind turbine 10, such as voltage, current, vibration, etc.

[0032] Now referring to Figure 4 , a schematic diagram of an embodiment of a wind turbine power system 100 in accordance with aspects of the present disclosure is shown. Although the present disclosure will generally be described herein with reference to the system 100 shown in Figure 4 , those skilled in the art, using the disclosure provided herein, should understand that aspects of the present disclosure may also be applicable to other power generation systems, and as mentioned above, the present invention is not limited to wind turbine systems.

[0033] In an Figure 4 embodiment, and as mentioned, the rotor 18 of the wind turbine 10 ( Figure 2 ) may optionally be coupled to a gearbox 38, which in turn is coupled to a generator 102, and the generator 102 may be a doubly-fed induction generator (DFIG). As Figure 4As shown, generator 102 may be connected to stator bus 104. Additionally, as shown, power converter 106 may be connected to generator 102 via rotor bus 108 and to stator bus 104 via line-side bus 110. In this regard, stator bus 104 may provide output polyphase power (e.g., three-phase power) from the stator of generator 102, and rotor bus 108 may provide output polyphase power (e.g., three-phase power) from the rotor of generator 102. Power converter 106 may also include a rotor-side converter (RSC) 112 and a line-side converter (LSC) 114. Generator 102 is coupled to rotor-side converter 112 via rotor bus 108. Additionally, RSC 112 is coupled to LSC 114 via DC link 116, and DC link capacitor 118 is across DC link 116. LSC 114 is in turn coupled to line-side bus 110.

[0034] RSC 112 and LSC 114 may be configured for normal operating modes in a three-phase pulse-width modulation (PWM) arrangement using one or more switching devices such as insulated gate bipolar transistor (IGBT) switching elements. Additionally, power converter 106 may be coupled to converter controller 120 to control the operation of rotor-side converter 112 and / or line-side converter 114, as described herein. It should be noted that converter controller 120 may be configured as an interface between power converter 106 and turbine controller 26 and may include any number of control devices.

[0035] In a typical configuration, various line contactors and circuit breakers may also be included, including, for example, grid circuit breaker 122, for isolating various components required for normal operation of generator 120 during connection to or disconnection from a load such as power grid 124. For example, system circuit breaker 126 may couple system bus 128 to transformer 130, which may be coupled to power grid 124 via grid circuit breaker 122. In alternative embodiments, fuses may replace some or all of the circuit breakers.

[0036] In operation, alternating current (AC) power generated at generator 102 by rotating rotor 18 is provided to power grid 124 via a dual path defined by stator bus 104 and rotor bus 108. On the rotor bus side 108, sinusoidal polyphase (e.g., three-phase) AC power is provided to power converter 106. Rotor-side converter 112 converts the AC power provided from rotor bus 108 into direct current (DC) power and provides the DC power to DC link 116. As generally understood, the switching elements (e.g., IGBTs) used in the bridge circuit of rotor-side converter 112 may be modulated to convert the AC power provided from rotor bus 108 into DC power suitable for DC link 116.

[0037] In addition, the line-side converter 114 converts the DC power on the DC link 116 into AC output power suitable for the power grid 124. In particular, the switching elements (e.g., IGBTs) used in the bridge circuit of the line-side converter 114 can be modulated to convert the DC power on the DC link 116 into AC power on the line-side bus 110. The AC power from the power converter 106 can be combined with the power from the stator of the generator 102 to provide polyphase power (e.g., three-phase power) having a frequency generally maintained at the frequency of the power grid 124 (e.g., 50 Hz or 60 Hz).

[0038] In addition, various circuit breakers and switches, such as the grid circuit breaker 122, the system circuit breaker 126, the stator synchronous switch 132, the converter circuit breaker 134, and the line contactor 136, may be included in the wind turbine power system 100 to connect or disconnect the corresponding buses, e.g., when the current is too large and may damage the components of the wind turbine power system 100 or for other operational considerations. Additional protection components may also be included in the wind turbine power system 100.

[0039] Furthermore, the power converter 106 may receive control signals from, for example, a local control system 176 via the converter controller 120. The control signals may be based, among other things, on the sensed state or operating characteristics of the wind turbine power system 100. Typically, the control signals provide control for the operation of the power converter 106. For example, feedback in the form of the sensed speed of the generator 102 may be used to control the conversion of the output power from the rotor bus 108 to maintain an appropriate and balanced polyphase (e.g., three-phase) power supply. Other feedback from other sensors may also be used by the controller(s) 120, 26 to control the power converter 106, including, for example, voltage and current feedback of the stator bus and the rotor bus. Using various forms of feedback information, switching control signals (e.g., gate timing commands for IGBTs), stator synchronous control signals, and circuit breaker signals can be generated.

[0040] The power converter 106 also compensates for or adjusts the frequency of the three-phase power from the rotor for variations (e.g., variations in the wind speed at the hub 20 and the rotor blades 22). Thus, the mechanical and electrical rotor frequencies are decoupled, and the electrical stator frequency and rotor frequency matching is facilitated substantially independently of the mechanical rotor speed.

[0041] In some states, the bidirectional characteristics of the power converter 106, and specifically, the bidirectional characteristics of the LSC 114 and the RSC 112 facilitate feeding at least some of the generated electrical power back into the generator rotor. More specifically, electrical power can be transmitted from the stator bus 104 to the line-side bus 110, and then through the line contactor 136 and into the power converter 106, specifically the LSC 114, which acts as a rectifier and rectifies the sinusoidal three-phase AC power into DC power. The DC power is transmitted into the DC link 116. The capacitor 118 facilitates reducing the DC link voltage amplitude variation by facilitating reducing the DC ripple sometimes associated with three-phase AC rectification.

[0042] The DC power is then transmitted to the RSC 112, which converts the DC electrical power into three-phase sinusoidal AC electrical power by adjusting the voltage, current, and frequency. This conversion is monitored and controlled via the converter controller 120. The converted AC power is transmitted from the RSC 112 to the generator rotor via the rotor bus 108. In this way, the generator reactive power control is facilitated by controlling the rotor current and voltage.

[0043] Now refer to Figure 5 , a schematic diagram of an embodiment of another wind turbine power system 100 according to aspects of the present disclosure is shown. In particular, Figure 5 a full-power conversion system is shown. It should be understood that Figure 5 similar components of Figure 4 will have the same markings as those set forth in

[0044] Now refer to Figure 6, the wind turbine power system 100 described herein may be part of a wind farm 50. As shown, the wind farm 50 may include a plurality of wind turbines 52 (including the wind turbine 10 described above), and an overall field-level controller 56. For example, as shown in the illustrated embodiment, the wind farm 50 includes twelve wind turbines, including the wind turbine 10. However, in other embodiments, the wind farm 50 may include any other number of wind turbines, such as fewer than twelve wind turbines or more than twelve wind turbines. In one embodiment, the turbine controllers in the plurality of wind turbines 52 are communicatively coupled to the field-level controller 56, for example, by a wired connection, such as by connecting the turbine controller 26 via a suitable communication link 54 (e.g., a suitable cable). Alternatively, the turbine controllers may be communicatively coupled to the field-level controller 56 by a wireless connection, such as by using any suitable wireless communication protocol known in the art. In additional embodiments, the field-level controller 56 is configured to send control signals to and receive control signals from the various wind turbines 52, such as, for example, to distribute real and / or reactive power demands across the wind turbines 52 of the wind farm 50.

[0045] Now referring to Figure 7 , a block diagram of an embodiment of suitable components in accordance with an example aspect of the present disclosure is shown. The suitable components may be included within a controller (such as any one of the converter controller 120, turbine controller 26, and / or field-level controller 56 described herein). As shown, the controller may include one or more processors 58, a computer, or other suitable processing unit, and an associated (multiple) memory device 60, which may include suitable computer-readable instructions that, when implemented, configure the controller to perform various different functions, such as receiving, transmitting, and / or executing wind turbine control signals (e.g., performing the methods, steps, calculations, etc. disclosed herein).

[0046] As used herein, the term "processor" refers not only to integrated circuits known in the art as being included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits, and other programmable circuits. Additionally, the (multiple) memory device 60 may generally include (multiple) memory elements, including but not limited to computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, compact disc read-only memory (CD-ROM), magneto-optical discs (MOD), digital versatile discs (DVD), and / or other suitable memory elements.

[0047] Such memory device(s) 60 may generally be configured to store suitable computer-readable instructions that, when implemented by processor(s) 58, configure the controller to perform the various functions described herein. Additionally, the controller may further include a communication interface 62 to facilitate communication between the controller and the various components of the wind turbine 10. The interface may include one or more circuits, terminals, pins, contacts, conductors, or other components for transmitting and receiving control signals. Further, the controller may include a sensor interface 64 (e.g., one or more analog-to-digital converters) to allow signals transmitted from sensors 66, 68 to be converted into signals that can be understood and processed by processor(s) 58.

[0048] Now referring to Figure 8 , a schematic diagram of an embodiment of a grid-forming power system 200 according to the present disclosure, which particularly shows a single-line diagram of a doubly-fed wind turbine generator 102 having an advanced control structure for grid-forming characteristics. In particular, as shown, the grid-forming power system 200 may include many of the same features described herein Figure 4 , where components having the same reference numerals represent similar components. Additionally, as shown, the grid-forming power system 200 may include a control structure for controlling the line-side converter, which is similar to the control structure shown in Figure 1 . More particularly, as shown, the line-side converter control structure may include a DC regulator 212 and a line current regulator 214. The DC regulator 212 is configured to generate a line-side current command for the line current regulator 214. The line current regulator 214 then generates a line-side voltage command for the modulator 218. The modulator 218 also receives an output (e.g., a phase-locked loop angle) from the phase-locked loop 216 to generate one or more gate pulses for the line-side converter 114. The phase-locked loop 216 typically uses a voltage feedback signal to generate its output.

[0049] Additionally, as shown, the grid-forming power system 200 may further include a unique control structure for controlling the rotor-side converter 112 using grid-forming characteristics. In particular, as shown in Figure 8 , the grid-forming power system 200 may include a stator voltage regulator 206 for providing such grid-forming characteristics. Additionally, as shown, the grid-forming power system 200 may include a grid voltage / VAR regulator 202, an inertia power regulator 204, a rotor current regulator 208, and a modulator 210.

[0050] More particularly, as will be explained, the grid-forming power system 200 includes an inner loop current regulator structure and a fast stator voltage regulator to transform the voltage command from the grid-forming control into a rotor current regulator command. Thus, the systems and methods of the present disclosure provide control of the rotor voltage of the generator 102 to meet a higher level of commands for the magnitude and angle of the stator voltage. Such control must be relatively fast and insensitive to the current flowing in the stator of the doubly-fed wind turbine generator 102.

[0051] Now referring to Figure 9 , a detailed block diagram of a power regulator (such as power regulator 204) according to the present disclosure is shown. In particular, as shown, the power regulator 205 includes a frequency reference signal ω REF and a phase-locked loop frequency signal ω PLL , which are combined to generate a frequency error signal E ω as shown according to the present disclosure. In a particular embodiment, for example, the power regulator 204 may be a grid-forming power regulator.

[0052] As shown, at summing point 220, the ω REF signal is subtracted from the signal representing the actual frequency of the output of the inverter-based resource, ω PLL , to generate the E ω error signal. The error signal E ω is provided to a frequency deviation control having a first control loop, which includes a conventional proportional plus integral regulator 222 and a deadband control 224. The deadband control 224 provides a certain range of variation of the frequency error signal, for example, approximately 1 / 2 Hz, without any change in the output signal. This limits the response due to natural fluctuations in the power system frequency. The proportional plus integral regulator 222 transforms the error signal E ω into a conventional bias signal, which is applied to summing point 226.

[0053] The second loop includes a proportional droop control 228, which may be a fixed gain that receives the error signal E ω and provides an immediate compensation signal to summing point 76, and the compensation signal is added to the output signal from the proportional plus integral regulator 222. The output of summing point 226 is a power offset signal coupled to summing point 230, and another input to summing point 230 is a power reference signal P REFTherefore, the frequency offset signal from summing point 226 is used to modify the power reference signal. The purpose of such modification is to adjust the power reference signal according to the change in frequency shift. More particularly, the system is intended to attempt to keep the system output frequency constant such that if there is an error between the output frequency and the reference frequency, the power reference signal is adjusted to compensate for the frequency error. Further, the power system to which the inverter-based resource is connected may include reactive loads such as AC induction and synchronous motors whose speed is directly related to the frequency of the inverter output signal. If additional power is supplied from the inverter-based resource, the inverter-based resource will tend to accelerate due to the inductive reaction of the machines as they start to decelerate, and the reduction in power will cause the frequency to drop. Therefore, frequency deviation control provides an important function in achieving control of the torque output of the machines connected to the output of the inverter-based resource. When connecting parallel grid-forming resources in a wind farm, droop (or frequency deviation control) also facilitates sharing of active power among the parallel resources.

[0054] The power regulator 204 also introduces an inertia regulator 234 that modifies the power error signal to simulate the inertia of a synchronous machine. More particularly, if a sudden change in output is experienced, the inertia regulator 234 prevents sudden frequency changes or power changes that can cause instantaneous torque to be generated by the motors connected to the output of the inverter-based resource.

[0055] If the power reference signal is modified by frequency deviation control, the resultant signal identified as P ORD develops at the output terminal of summing point 230 and is applied to summing point 232 where the commanded power or demanded power is compared with the measured output power P B of the system. In such embodiments, the P B signal represents the actual power developed at the output of the inverter-based resource. The output signal from summing point 232 represents the power error signal applied to the inertia regulator 234. As described above, the signal developed by the inertia regulator 234 represents the desired frequency ω 1 of the internal voltage E 1 and will be the same as the frequency ω PLL if the frequency is correctly tracked.

[0056] In this regard, the signal ω 1 developed at the output of the inertia regulator 234 is added to the ω PLL signal in summing point 236. Any difference between the phase-locked loop frequency and the signal ω 1 results in an error signal that is applied to integrator 238 to develop the δ IT signal. In an embodiment, integrator 238 is a conventional type of integrator whose output signal δ ITis the angle offset that can be added to the output signal from the phase-locked loop to generate the output signal θ 1 It will be appreciated that ω PLL The signal is taken from the phase-locked loop and thus represents the actual frequency of the output of the inverter-based resource. In the case of a sudden opening of the utility breaker, ω PLL The signal will represent the actual frequency of the voltage generated by the inverter-based resource, and the power regulator 204 will cause the power output of the inverter-based resource to be adjusted according to the change in the output frequency. The integrator 240 in the inertia regulator 234 becomes important for limiting any attempted frequency change in the control system. It will be appreciated that the setting of the deadband control 224 and the gain at the proportional droop control 228 are selected to coordinate with the changes in the power system to which the inverter-based resource is connected and with the load to which the inverter-based resource will supply power. Additionally, the grid-forming power system 200 may be adapted to modify the settings of the deadband control 224, the proportional droop control 228, and / or the inertia power regulator 204 in an adaptive manner, such as when the state of the utility breaker changes to connect the utility to the system or disconnect the utility from the load system.

[0057] In particular, the systems and methods of the present disclosure relate to adjusting the gain of the grid-forming power regulator 204 in such a way that the power output of the wind turbine generator is less sensitive to changes in the grid frequency / phase angle at lower speeds. In particular, Figure 10 FIG. shows a flowchart of an embodiment of a method 250 for providing grid frequency support for a wind turbine connected to a power grid to prevent trip events in the wind turbine. Generally, method 250 is described herein with reference to Figures 2 to 9 wind turbine 10. However, it should be appreciated that the disclosed method 250 can be implemented using a wind turbine having any other suitable configuration. Additionally, although Figure 10 the steps are depicted for illustration and discussion purposes as being performed in a particular order, the methods discussed herein are not limited to any particular order or arrangement. Those skilled in the art using the disclosure provided herein will recognize that the various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or adapted in various ways without departing from the scope of the present disclosure.

[0058] As shown at (252), method 250 includes receiving, via a controller, one or more speed feedback signals from a wind turbine. For example, in an embodiment, the (multiple) speed feedback signals may include rotor speed, generator speed, wind speed, or any other speed parameter of the wind turbine. As shown at (254), method 250 includes adjusting, via the controller, one or more parameters of a power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of grid frequency or phase angle. In an embodiment, for example, the (multiple) parameters of power regulator 204 may include one or more gains of power regulator 204. In particular, it is beneficial that the power output of the wind turbine is less sensitive to a grid frequency drop or a negative phase jump when the amount of energy available to the wind turbine is low enough such that support of grid frequency and / or phase cannot be maintained without tripping (e.g., a low speed trip). The amount of available energy may be related to the energy input from the wind or the stored kinetic energy of the rotating system. The amount of available energy may be related to the energy input from the wind or the stored kinetic energy of the rotating system. The energy input from the wind may be closely related to the measured wind speed, and the stored kinetic energy may be closely related to the measured generator speed or rotor speed.

[0059] may be referred to Figure 11 for a better understanding Figure 10 of method 250. In particular, Figure 11 FIG. shows a schematic diagram of system 300 for adjusting the gain of power regulator 204 of wind turbine 10 based on speed such that the power output of wind turbine 10 is less sensitive to changes in grid frequency and / or phase angle. More specifically, as shown, system 300 is configured to receive a speed threshold 302 (e.g., SpdThrs) and one or more speed feedback signals 304 (e.g., SpdFbk). In an embodiment, for example, speed threshold 302 generally encompasses a predetermined speed threshold below which the power regulator gain begins to change direction to reduce sensitivity to grid frequency / phase changes. Additionally, in an embodiment, the (multiple) speed feedback signals 304 generally encompass speed feedback signals of variable speed wind turbine 10 that are typically estimated based on sensor instrumentation (e.g., using a tachometer and / or an encoder).

[0060] In addition, as shown, system 300 may include one or more filters 306 for filtering one or more speed feedback signals from wind turbine 10. Thus, as shown at 308, system 300 is configured to compare the (multiple) speed feedback signals 304 from wind turbine 10 with a speed threshold 302 to obtain a difference 309 between the (multiple) speed feedback signals 304 and the speed threshold 302. In addition, when the (multiple) speed feedback signals 304 are less than the speed threshold 302, as shown at 310, system 300 is configured to apply a predetermined parameter setting 310 (e.g., SpdGn) to the difference 309 to generate a speed-related scale factor 314 (e.g., SpdSF). In such embodiments, when SpdFbk < SpdThrs, the predetermined parameter setting determines the steepness of the relationship between the speed and the power regulator setting. In additional embodiments, as shown, system 300 may also be configured to limit the speed-related scale factor 314, e.g., via a limiter 312.

[0061] Thus, the speed-related scale factor 314 is used to determine various power regulator settings. For example, in an embodiment, system 300 is configured to use the speed-related scale factor 314 to determine the gain of power regulator 204 and apply the gain to the operation of power regulator 204. In a particular embodiment, as shown, the (multiple) gains of power regulator 204 may include an inertia setting 320 of power regulator 204 (e.g., Figure 9 parameter H in inertia regulator 234 in Figure 9 ), one or more damping parameters 316, 318 of power regulator 204 (e.g., D parameter ω Figure 9 and D in inertia regulator 234 in Figure 11 ), and / or the frequency droop / proportional droop 322 of power regulator 204 (e.g., within

[0062] proportional droop control 228 of

[0063] Another aspect of the present invention is provided by the subject matter of the following clauses:

[0064] The method according to any of the preceding clauses, wherein one or more speed feedback signals include at least one of a rotor speed, a generator speed, or a wind speed.

[0065] The method according to any of the preceding clauses, wherein the power regulator is a grid-forming power regulator.

[0066] The method according to any of the preceding clauses, wherein one or more parameters of the power regulator include one or more gains of the power regulator.

[0067] The method according to any of the preceding clauses, wherein one or more gains of the power regulator include at least one of the following: an inertia setting of the power regulator, one or more damping parameters of the power regulator, or a frequency droop parameter of the power regulator.

[0068] The method according to any of the preceding clauses, wherein adjusting one or more parameters of the power regulator of the wind turbine depending on one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of a grid frequency or a phase angle further includes: receiving a speed threshold via a controller; and comparing, via the controller, one or more speed feedback signals from the wind turbine with the speed threshold to obtain a difference between the one or more speed feedback signals and the speed threshold.

[0069] The method according to any of the preceding clauses, wherein adjusting one or more parameters of the power regulator of the wind turbine depending on one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of a grid frequency or a phase angle further includes: when the one or more speed feedback signals are less than the speed threshold, applying a predetermined parameter setting to the difference via the controller to generate a speed-related scale factor, the predetermined parameter setting determining a steepness of a relationship between the speed and the power regulator setting.

[0070] The method according to any of the preceding clauses, wherein adjusting one or more parameters of the power regulator of the wind turbine depending on one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of a grid frequency or a phase angle further includes: determining, via the controller, one or more parameters of the power regulator using the speed-related scale factor; and applying the one or more parameters to the operation of the power regulator.

[0071] The method according to any of the preceding clauses, wherein adjusting one or more parameters of the power regulator of the wind turbine depending on one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of a grid frequency or a phase angle further includes: limiting the speed-related scale factor via a limiter of the controller.

[0072] The method according to any of the preceding clauses, the method further comprising filtering one or more speed feedback signals from the wind turbine via a filter of the controller.

[0073] A power regulator configured to constrain the grid frequency support of a wind turbine connected to an electrical grid to prevent a tripping event in the wind turbine, the power regulator comprising: a controller including at least one processor configured to perform a plurality of operations, the plurality of operations including: receiving one or more speed feedback signals from the wind turbine, and adjusting one or more parameters of the power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle.

[0074] The power regulator according to any of the preceding clauses, wherein the one or more speed feedback signals include at least one of a rotor speed, a generator speed, or a wind speed.

[0075] The power regulator according to any of the preceding clauses, wherein the power regulator is a grid-forming power regulator.

[0076] The power regulator according to any of the preceding clauses, wherein the one or more parameters of the power regulator include one or more gains of the power regulator.

[0077] The power regulator according to any of the preceding clauses, wherein the one or more gains of the power regulator include at least one of the following: an inertia setting of the power regulator, one or more damping parameters of the power regulator, or a frequency droop parameter.

[0078] The power regulator according to any of the preceding clauses, wherein adjusting one or more parameters of the power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: receiving a speed threshold; and comparing the one or more speed feedback signals from the wind turbine with the speed threshold to obtain a difference between the one or more speed feedback signals and the speed threshold.

[0079] The power regulator according to any of the preceding clauses, wherein adjusting one or more parameters of the power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: when the one or more speed feedback signals are less than the speed threshold, applying a predetermined parameter setting to the difference to generate a speed-related scaling factor, the predetermined parameter setting determining the steepness of the relationship between the speed and the power regulator setting.

[0080] A power regulator according to any of the preceding clauses, wherein adjusting one or more parameters of a power regulator of a wind turbine depending on one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of grid frequency or phase angle further comprises: determining one or more parameters of the power regulator using a speed-dependent scaling factor; and applying the one or more parameters to the operation of the power regulator.

[0081] A power regulator according to any of the preceding clauses, wherein adjusting one or more parameters of a power regulator of a wind turbine depending on one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of grid frequency or phase angle further comprises: limiting the speed-dependent scaling factor.

[0082] A power regulator according to any of the preceding clauses, the power regulator further comprising filtering one or more speed feedback signals from the wind turbine.

[0083] This written description uses examples to disclose the invention (including the best mode), and also enables those skilled in the art to practice the invention (including making and using any device or system and performing any incorporated method). The scope of patentability of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples include structural elements that do not differ from the literal language of the claims, or if such other examples include equivalent structural elements that do not differ significantly from the literal language of the claims, then such other examples are intended to be within the scope of the claims.

Claims

1. A method for constraining the grid frequency support of a wind turbine connected to an electric power grid to prevent tripping events in the wind turbine, the method comprises: receiving, via a controller, one or more speed feedback signals from the wind turbine; and adjusting, via the controller, one or more parameters of a power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of grid frequency or phase angle.

2. The method according to claim 1, wherein, the one or more speed feedback signals include at least one of rotor speed, generator speed, or wind speed.

3. The method according to claim 1, wherein, the power regulator is a grid-forming power regulator.

4. The method according to claim 1, wherein, the one or more parameters of the power regulator include one or more gains of the power regulator.

5. The method according to claim 4, wherein, the one or more gains of the power regulator include at least one of the following: the inertia setting of the power regulator, one or more damping parameters of the power regulator, or the frequency droop parameter of the power regulator.

6. The method according to claim 1, wherein, adjusting the one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: receiving, via the controller, a speed threshold; and comparing, via the controller, the one or more speed feedback signals from the wind turbine with the speed threshold to obtain a difference between the one or more speed feedback signals and the speed threshold.

7. The method according to claim 6, wherein, adjusting the one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: when the one or more speed feedback signals are less than the speed threshold, applying, via the controller, a predetermined parameter setting to the difference to generate a speed-related scale factor, the predetermined parameter setting determining the steepness of the relationship between speed and power regulator setting.

8. The method according to claim 7, wherein, adjusting the one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: determining, via the controller, the one or more parameters of the power regulator using the speed-related scale factor; and applying the one or more parameters to the operation of the power regulator.

9. The method according to claim 8, wherein, Adjusting one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: Limiting the speed-related scaling factor via a limiter of the controller.

10. The method according to claim 1, the method further comprising filtering, via a filter of the controller, the one or more speed feedback signals from the wind turbine.

11. A power regulator configured to constrain the grid frequency support of a wind turbine connected to an electrical network to prevent a tripping event in the wind turbine, the power regulator comprising: A controller, the controller including at least one processor configured to perform a plurality of operations, the plurality of operations including: Receiving one or more speed feedback signals from the wind turbine; and Adjusting one or more parameters of the power regulator of the wind turbine based on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle.

12. The power regulator according to claim 11, wherein, The one or more speed feedback signals include at least one of a rotor speed, a generator speed, or a wind speed.

13. The power regulator according to claim 11, wherein, The power regulator is a grid-forming power regulator.

14. The power regulator according to claim 11, wherein, The one or more parameters of the power regulator include one or more gains of the power regulator.

15. The power regulator according to claim 14, wherein, The one or more gains of the power regulator include at least one of the following: the inertia setting of the power regulator, one or more damping parameters of the power regulator, or a frequency droop parameter.

16. The power regulator according to claim 11, wherein, Adjusting one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: Receiving a speed threshold; and Comparing the one or more speed feedback signals from the wind turbine with the speed threshold to obtain a difference between the one or more speed feedback signals and the speed threshold.

17. The power regulator according to claim 16, wherein, Adjusting one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: When the one or more speed feedback signals are less than the speed threshold, a predetermined parameter setting is applied to the difference to generate a speed-related scaling factor, and the predetermined parameter setting determines the steepness of the relationship between speed and power regulator setting.

18. The power regulator according to claim 17, wherein, adjusting the one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: determining the one or more parameters of the power regulator using the speed-related scaling factor; and applying the one or more parameters to the operation of the power regulator.

19. The power regulator according to claim 18, wherein, adjusting the one or more parameters of the power regulator of the wind turbine depending on the one or more speed feedback signals such that the power output of the wind turbine is less sensitive to changes in at least one of the grid frequency or the phase angle further comprises: limiting the speed-related scaling factor.

20. The power regulator according to claim 11, the power regulator further comprising filtering the one or more speed feedback signals from the wind turbine.

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