System and method for operating grid-following inverter-based resource

Abstract

A method for operating a grid-following inverter-based resource (IBR) connected to a power grid. The IBR has a controller. The method includes receiving, via the controller, a frequency feedback signal representative of an electrical frequency of the power grid. The method also includes determining, via the controller, a power support signal based on applying a function to the frequency feedback signal. The power support signal is configured to emulate grid-forming control for at least one of inertial power, phase jump power, and droop power in response to at least one of the frequency feedback signal and a phase jump of the power grid. The method further includes determining, via the controller, an active power command signal for the IBR based on the power support signal and a power reference signal. In addition, the method includes controlling, via the controller, the IBR based, at least in part, on the active power command signal so as to emulate grid-forming control.

Description

701070-WG-1 / GECW-1286-PCTSYSTEM AND METHOD FOR OPERATING GRID-FOLLOWING INVERTERBASED RESOURCEFIELD

[0001] The present disclosure relates generally to inverter-based resources, such as wind turbine power systems and more particularly, to systems and methods for operating a grid-following (GFL) inverter-based resource (IBR) to emulate gridforming (GFM) control of the IBR.BACKGROUND

[0002] Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modem wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. For example, rotor blades typically have the cross-sectional profde of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides. Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is typically geared to a generator for producing electricity.

[0003] Wind turbines can be distinguished in two types: fixed speed and variable speed turbines. Conventionally, variable speed wind turbines are controlled as current sources connected to a power grid. In other words, the variable speed wind turbines rely on a 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 the wind turbines is based on the assumptions that the grid voltage waveforms are fundamental voltage waveforms with fixed frequency and magnitude and that the penetration of wind power into the grid is low enough so as to not cause disturbances to the grid voltage magnitude and frequency.

[0004] Thus, the wind turbines simply inject the specified current into the grid based on the fundamental voltage waveforms. However, with the rapid growth of the wind power, wind pow er penetration into some grids has increased to the point where701070-WO-1 / GECW-1286-PCTwind turbine generators have a significant impact on the grid voltage and frequency. When wind turbines are located in a weak grid, wind turbine power fluctuations may lead to an increase in magnitude and frequency variations in the grid voltage. These fluctuations may adversely affect the performance and stability of the PLL and wind turbine current control.

[0005] Many existing renewable generation sources, such as double-fed wind turbine generators (WTGs), may operate in under “grid-following” (GFL) control and utilize fast current-regulation loops to control active and reactive power exchanged with the grid. More specifically, FIG. 1 illustrates the basic elements of the main circuit and converter control structure for a grid-following double-fed WTG. As shown, the active power reference to the converter is developed by the energy source regulator, e.g., the turbine control portion of a wind turbine, and is conveyed as a torque reference which represents the lesser of the maximum attainable power from the energy source at that instant, or a curtailment command from a higher-level grid controller. The converter control then determines a current reference for the active component of current to achieve the desired torque. Accordingly, the double-fed WTG includes functions that manage the voltage and reactive power in a manner that results in a command for the reactive component of current. Wide-bandwidth current regulators then develop commands for voltage to be applied by the converters to the system, such that the actual currents closely track the commands.

[0006] Alternatively, an inverter-based resource (IBR) (such as a double-fed WTG and controls) may operate under “grid-forming” (GFM) control wherein the IBR acts as a voltage source behind an impedance (primarily reactance) and provides a voltage-source characteristic, where the angle and magnitude of the voltage are controlled to achieve the regulation functions needed by the grid. In particular, the impedance of the IBR is normally dictated by the hardware of the system, such as reactors, transformers, or rotating machine impedances. With this structure, current will flow according to the demands of the grid, while the converter contributes to establishing a voltage and frequency for the grid. This characteristic is comparable to conventional generators based on a turbine driving a synchronous machine.

[0007] Thus, a GFM IBR desirably includes the following basic functions: (1) support grid voltage and frequency for any current flow within the rating of the701070-WO-1 / GECW-1286-PCTequipment, both real and reactive; (2) prevent operation beyond equipment voltage or current capability by allowing grid voltage or frequency to change rather than disconnecting equipment (disconnection is allowed only when voltage or frequency are outside of bounds established by the grid entity); (3) remain stable for any grid configuration or load characteristic, including serving an isolated load or connected with other grid-forming sources, and switching between such configurations; (4) share total load of the grid among other grid-forming sources connected to the grid; (5) ride through grid disturbances, both major and minor, and (6) meet requirements (1 )-(5) without requiring fast communication with other control systems existing in the grid, or externally-created logic signals related to grid configuration changes.

[0008] The basic control structure to achieve the above GFM objectives was developed and field-proven for battery systems in the early 1990’s (see e.g., United States Patent No.: 5,798,633 entitled “Battery Energy Storage Power Conditioning System”). Applications to full-converter wind generators and solar generators are disclosed in United States Patent No.: 7,804,184 entitled “System and Method for Control of a Grid Connected Power Generating System.” and United States Patent No.: 9,270,194 entitled “Controller for controlling a power converter.” Applications to grid-forming control for a double-fed WTG are disclosed in PCT / US2020 / 013787 entitled “System and Method for Providing Grid-Forming Control for a Doubly-Feb Wind Turbine Generator.”

[0009] Accordingly, GFM WTGs are capable of important grid-supporting functions, including inertial power response and phase jump power response to grid frequency and phase angle changes, respectively. In addition, GFM WTGs are able to provide these functions by using the rotating kinetic energy stored within the wind turbine itself. These functions improve grid stability by changing active power output automatically in response to the load demands of the grid. However, a consequence of providing these functions is that controlling the angle and magnitude of the voltage to achieve the regulation functions needed by the grid under GFM control is more complex than controlling active and reactive power exchanged with the grid under GFL control.

[0010] Accordingly, the present disclosure is directed to systems and methods for operating a GFL IBR to emulate GFM control so as to address the aforementioned701070-WO-1 / GECW-1286-PCTissues.BRIEF DESCRIPTION

[0011] Aspects and advantages of the disclosure will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the disclosure.

[0012] In an aspect, the present disclosure is directed to a method for operating a grid-following inverter-based resource (IBR) connected to a power grid. The IBR has a controller. The method includes receiving, via the controller, a frequency feedback signal representative of an electrical frequency of the power grid. The method also includes determining, via the controller, a power support signal based on applying a function to the frequency feedback signal. The power support signal is configured to emulate grid-forming control for at least one of inertial power, phase jump power, and droop power in response to at least one of the frequency feedback signal and a phase jump of the power grid. The method further includes determining, via the controller, an active power command signal for the IBR based on the power support signal and a power reference signal. In addition, the method includes controlling, via the controller, the IBR based, at least in part, on the active power command signal so as to emulate grid-forming control.

[0013] In another aspect, the present disclosure is directed to an IBR connected to a power grid. The inverter-based resource includes at least one controller for controlling the inverter-based resource to provide grid-following control thereof. The controller includes at least one processor configured to perform a plurality of operations. The plurality of operations includes receiving a frequency feedback signal representative of an electrical frequency of the power grid. The plurality of operations also includes determining a power support signal based on applying a function to the frequency feedback signal. The power support signal is configured to emulate grid-forming control for at least one of inertial power, phase jump power, and droop power in response to at least one of the frequency feedback signal and a phase jump. The plurality of operations further includes determining an active power command signal for the IBR based on the power support signal and a power reference signal. In addition, the plurality of operations includes controlling the IBR based, at701070-WO-1 / GECW-1286-PCTleast in part, on the active power command signal so as to emulate grid-forming control.

[0014] These and other features, aspects and advantages of the present disclosure 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 disclosure and, together with the description, serve to explain the principles of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] A full and enabling disclosure of the present disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0016] FIG. 1 illustrates a one-line diagram of a doubly-fed wind turbine generator with structure of converter controls for grid-following application according to conventional construction;

[0017] FIG. 2 illustrates a perspective view of an embodiment of a wind turbine according to the present disclosure;

[0018] FIG. 3 illustrates a simplified, internal view of an embodiment of a nacelle according to the present disclosure;

[0019] FIG. 4 illustrates a schematic view of an embodiment of a wind turbine electrical power system suitable for use with the wind turbine shown in FIG. 1;

[0020] FIG. 5 illustrates a schematic view of an embodiment of a wind farm having a plurality of wind turbines according to the present disclosure;

[0021] FIG. 6 illustrates a block diagram of an embodiment of a controller according to the present disclosure;

[0022] FIG. 7 illustrates a flow diagram of an embodiment of method for operating a grid-following inverter-based resource to emulate grid-forming control of the inverter-based resource according to the present disclosure;

[0023] FIG. 8 illustrates a schematic diagram of an embodiment of a grid following power system according to the present disclosure, particularly illustrating a one-line diagram of the for operating a grid following inverter-based resource to emulate grid forming control of the inverter-based resource; and701070-WD-1 / GECW-1286-PCT

[0024] FIG. 9 illustrates a schematic diagram of an embodiment of a function for determining a power support signal according to the present disclosure.DETAILED DESCRIPTION

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

[0026] In general, the present disclosure is directed to systems and methods for controlling an inverter-based resource connected to a power grid to provide gridfollowing control of the inverter-based resource that emulates grid-forming control. As used herein, inverter-based resources generally refer to electrical devices that can generate or absorb electric power through switching of power-electronic devices. Accordingly, inverter-based resource may include wind turbine generators, solar inverters, energy-storage systems, STATCOMs, or hydro-power systems. For example, in an embodiment, the inverter-based resource may be a wind turbine power system having a rotor-side converter, a line-side converter, and a generator connected to the power grid.

[0027] Referring now to the drawings. FIG. 2 illustrates a perspective view of an embodiment of a wind turbine 10 according to the present disclosure. 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 and extending outwardly from the hub 20. For example, in the illustrated embodiment, the rotor 18 includes three rotor blades 22. However, in an alternative embodiment, the rotor 18 may include more or less than three rotor blades 22. Each rotor blade 22701070-WO-1 / GECW-1286-PCTmay be spaced about the hub 20 to facilitate rotating the rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub 20 may be rotatably coupled to an electric generator 24 (FIG. 3) positioned within the nacelle 16 to permit electrical energy to be produced.

[0028] The wind turbine 10 may also include a wind turbine controller 26 centralized 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 outside the wind turbine 10. Further, the controller 26 may be communicatively coupled to any number of the components of the wind turbine 10 in order to control the operation of such components and / or implement a corrective or control action. As such, the controller 26 may include a computer or other suitable processing unit. Thus, 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. Accordingly, the controller 26 may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences), de-rating or up-rating the wind turbine, and / or individual components of the wind turbine 10.

[0029] Referring now to FIG. 3, a simplified, internal view of an embodiment of the nacelle 16 of the wind turbine 10 shown in FIG. 2 is illustrated. As shown, a generator 24 may be disposed within the nacelle 16 and supported atop a bedplate 46. In general, the generator 24 may be coupled to the rotor 18 for producing 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 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 through a gearbox 38. As is 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 convert the low speed, high torque input to a high speed, low torque output to drive the generator shaft 36 and, thus, the generator 24.

[0030] The wind turbine 10 may also one or more pitch drive mechanisms 32 communicatively coupled to the wind turbine controller 26, with each pitch701070-WD-1 / GECW-1286-PCTadjustment mechanism(s) 32 being configured to rotate a pitch bearing 40 and thus the individual rotor blade(s) 22 about its respective pitch axis 28. In addition, 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 a yaw bearing 44 of the wind turbine 10 that is arranged between the nacelle 16 and the tower 12 of the wind turbine 10).

[0031] In addition, 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 of the wind turbine 10 may be measured, such as through use of a suitable weather sensor 66. Suitable weather sensors may include, for example, Light Detection and Ranging (“LIDAR”) devices, Sonic Detection and Ranging (“SOD AR”) devices, anemometers, wind vanes, barometers, radar devices (such as Doppler radar devices) or any other sensing device which can provide wind directional information now known or later developed in the art. Still further sensors 68 may be utilized to measure additional operating parameters of the wind turbine 10, such as voltage, current, vibration, etc. as described herein.

[0032] Referring now to FIG. 4, a schematic diagram of an embodiment of a wind turbine power system 100 is illustrated in accordance with aspects of the present disclosure. Although the present disclosure will generally be described herein with reference to the wind turbine 10 shown in FIG. 2, those of ordinary skill in the art, using the disclosures provided herein, should understand that aspects of the present disclosure may also be applicable in other power generation systems, and, as mentioned above, that the disclosure is not limited to wind turbine systems.

[0033] In the embodiment of FIG. 4 and as mentioned, the rotor 18 of the wind turbine 10 (FIG. 2) may, optionally, be coupled to the gearbox 38, which is, in turn, coupled to a generator 102, which may be a doubly fed induction generator (DFIG). As shown, the generator 102 may be connected to a stator bus 104. Further, as shown, a power converter 106 may be connected to the generator 102 via a rotor bus 108, and to the stator bus 104 via a line side bus 110. As such, the stator bus 104 may provide an output multiphase power (e.g., three-phase power) from a stator of the generator 102, and the rotor bus 108 may provide an output multiphase power (e.g.,701070-WO-1 / GECW-1286-PCTthree-phase power) from a rotor of the generator 102. The power converter 106 may also include a rotor side converter (RSC) 112 and a line side converter (LSC) 114. The generator 102 is coupled via the rotor bus 108 to the rotor side converter 112. Additionally, the RSC 112 is coupled to the LSC 114 via a DC link 116 across which is a DC link capacitor 118. The LSC 114 is, in turn, coupled to the line side bus 110.

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

[0035] In typical configurations, various line contactors and circuit breakers including, for example, a grid breaker 122 may also be included for isolating the various components as necessary for normal operation of the generator 102 during connection to and disconnection from a load, such as the electrical grid 124. For example, a system circuit breaker 126 may couple a system bus 128 to a transformer 130, which may be coupled to the electrical grid 124 via the grid breaker 122. In alternative embodiments, fuses may replace some or all of the circuit breakers.

[0036] In operation, alternating current power generated at the generator 102 by rotating the rotor 18 is provided to the electrical grid 124 via dual paths defined by the stator bus 104 and the rotor bus 108. On the rotor bus side 108, sinusoidal multiphase (e.g.. three-phase) alternating current (AC) power is provided to the power converter 106. The rotor side converter 112 converts the AC power provided from the rotor bus 108 into direct current (DC) power and provides the DC power to the DC link 116. As is generally understood, switching elements (e.g., IGBTs) used in the bridge circuits of the rotor side converter 112 may be modulated to convert the AC power provided from the rotor bus 108 into DC power suitable for the 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 electrical grid 124. In particular,701070-WD-1 / GECW-1286-PCTswitching elements (e.g., IGBTs) used in bridge circuits 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 generator 102 to provide multi-phase power (e.g., three-phase power) having a frequency maintained substantially at the frequency of the electrical grid 124 (e.g., 50 Hz or 60 Hz).

[0038] Additionally, various circuit breakers and switches, such as grid breaker 122, system breaker 126, stator sync switch 132, converter breaker 134, and line contactor 136 may be included in the wind turbine power system 100 to connect or disconnect corresponding buses, for example, when current flow is excessive and may¬ damage 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] Moreover, the power converter 106 may receive control signals from, for instance, the local control system 176 via the converter controller 120. The control signals may be based, among other things, on sensed states or operating characteristics of the wind turbine power system 100. Typically, the control signals provide for control of the operation of the power converter 106. For example, feedback in the form of a sensed speed of the generator 102 may be used to control the conversion of the output pow er from the rotor bus 108 to maintain a proper and balanced multi-phase (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, stator and rotor bus voltages and current feedbacks. Using the various forms of feedback information, switching control signals (e.g., gate timing commands for IGBTs). stator synchronizing control signals, and circuit breaker signals may be generated.

[0040] The pow er converter 106 also compensates or adjusts the frequency of the three-phase power from the rotor for changes, for example, in the wind speed at the hub 20 and the rotor blades 22. Therefore, mechanical and electrical rotor frequencies are decoupled and the electrical stator and rotor frequency matching is facilitated substantially independently of the mechanical rotor speed.

[0041] Under some states, the bi-directional characteristics of the pow er converter701070-WO-1 / GECW-1286-PCT106, and specifically, the bi-directional characteristics of the LSC 114 and RSC 112, facilitate feeding back at least some of the generated electrical power into generator rotor. More specifically, electrical power may be transmitted from the stator bus 104 to the line side bus 110 and subsequently 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 to DC power. The DC power is transmitted into the DC link 116. The capacitor 118 facilitates mitigating DC link voltage amplitude variations by facilitating mitigation of a DC ripple sometimes associated with three-phase AC rectification.

[0042] The DC power is subsequently transmitted to the RSC 112 that converts the DC electrical power to a three-phase, sinusoidal AC electrical power by adjusting voltages, currents, and frequencies. This conversion is monitored and controlled via the converter controller 120. The converted AC power is transmitted from the RSC 112 via the rotor bus 108 to the generator rotor. In this manner, generator reactive power control is facilitated by controlling rotor current and voltage.

[0043] Referring now to FIG. 5. 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 farm-level controller 56. For example, as shown in the illustrated embodiment, the wind farm 50 includes twelve wind turbines, including wind turbine 10. However, in other embodiments, the wind farm 50 may include any other number of wind turbines, such as less than twelve w ind turbines or greater than twelve wind turbines. In an embodiment, the turbine controllers of the plurality of wind turbines 52 are communicatively coupled to the farm-level controller 56, e.g., through a wired connection, such as by connecting the turbine controller 26 through suitable communicative links 54 (e g., a suitable cable). Alternatively, the turbine controllers may be communicatively coupled to the farm-level controller 56 through a wireless connection, such as by using any suitable wireless communications protocol known in the art. In further embodiments, the farm-level controller 56 is configured to send and receive control signals to and from the various wind turbines 52, such as for example, distributing real and / or reactive pow er demands across the wand turbines 52 of the wind farm 50.701070-WO-1 / GECW-1286-PCT

[0044] Referring now to FIG. 6, a block diagram of an embodiment of suitable components that may be included within the controller (such as any one of the converter controller 120. the turbine controller 26. and / or the farm-level controller 56 described herein) in accordance with example aspects of the present disclosure is illustrated. As shown, the controller may include one or more processor(s) 58, computer, or other suitable processing unit and associated memory device(s) 60 that 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 and the like disclosed herein).

[0045] As used herein, the term "‘processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) 60 may generally include memory element(s) including, but not limited to, computer readable medium (e.g.. random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memon ). a floppy disk, a compact disc-read only memon' (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and / or other suitable memory' elements.

[0046] Such memory device(s) 60 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) 58, configure the controller to perform various functions as described herein.Additionally, the controller may also include a communications interface 62 to facilitate communications between the controller and the various components of the wind turbine 10. An interface can include one or more circuits, terminals, pins, contacts, conductors, or other components for sending and receiving control signals. Moreover, the controller may include a sensor interface 64 (e.g., one or more analog-to-digital converters) to permit signals transmitted from the sensors 66, 68 to be converted into signals that can be understood and processed by the processor(s) 58.

[0047] Referring now to FIG. 7, a flow diagram of an embodiment of a method 200 for operating a grid-following (GFL) inverter-based resource (IBR) to emulate grid-forming (GFM) control of the IBR is provided according to the present701070-WG-1 / GECW-1286-PCTdisclosure. In an embodiment, for example, the IBR may be a wind turbine power system having at least one power converter and a generator (such as a DFIG). In general, the method 200 is described herein with reference to the wind turbine power system 100 of FIGS. 2-6. However, it should be appreciated that the disclosed method 200 may be implemented with any other suitable power generation systems having any other suitable configurations. In addition, although FIG. 7 depicts steps performed in a particular order for purposes of illustration and discussion, the methods discussed herein are not limited to any particular order or arrangement. One skilled in the art, using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or adapted in various ways without deviating from the scope of the present disclosure.

[0048] As shown at (202), the method 200 includes receiving, via a controller (e.g., the converter controller 120), a frequency feedback signal representative of an electrical frequency of the power grid. For example, the method 200 may include receiving the frequency feedback signal from a higher-level controller (e.g., the turbine controller 26 or the farm-level controller 56). In general, the method 200 is described herein with reference to the controller being the converter controller 120 and the higher-level controller being the turbine controller 26 and / or the farm-level controller 56. However, it should be appreciated that the disclosed method 200 can be implemented with the turbine controller 26 as the controller and the farm-level controller 56 as the higher-level controller.

[0049] In general, feedback signals (e.g., power feedback signals, frequency feedback signals, speed feedback signals, voltage feedback signals, etc.) may be measured by one or more sensors 68 and / or determined by (e.g., according to known mathematical techniques) one or more controllers 26, 56, 120 (e.g.. based on measurements received from the one or more sensors 68). As one example, a frequency feedback signal may be obtained by measuring voltage and using the measured voltage feedbacks as inputs to a phase-locked loop (PLL) algorithm.

[0050] As shown at (204), the method 200 includes determining, via the controller, a power support signal based on applying a function 400 to the frequency feedback signal. The power support signal is configured to emulate grid-forming control for at least one of inertial power, phase jump power, and droop power in701070-WO-1 / GECW-1286-PCTresponse to at least one of the frequency feedback signal and a phase jump (i.e., a change in a phase angle) of the power grid. In an embodiment, for example, the method 200 may include determining, via the converter controller, the power support signal based on a comparison of a first signal and a second signal. The first signal may be determined based on applying a first gain to the frequency feedback signal. In an embodiment, the first gain may be a fixed gain. The second signal may be determined based on applying a low-pass filter to the frequency feedback signal. In an embodiment, the filter may be configured to limit a duration of the second signal based on a feedback signal.

[0051] Moreover, in an embodiment, a filter gain of the low-pass filter may be a variable gain dependent on a difference between the frequency feedback signal and a nominal electrical frequency of the power grid. For example, the second gain may equal the first gain when the difference between the electrical frequency of the power grid and the nominal electrical frequency is zero. The nominal electrical frequency may be a frequency of the power grid under normal operating conditions (e.g., 50 Hz or 60 Hz).

[0052] Further, in an embodiment, the power support signal may be limited by a limit (such as a maximum limit and / or a minimum limit). The limit may be a variable limit dependent on the feedback signal. Thus, the limit may be configured to provide a constraint on the power support signal to prevent excessive loading and / or reverse loading on the wind turbine 10 and / or components thereof in response to frequency and / or phase angle deviations of the power grid.

[0053] Referring still to FIG. 7, as shown at (206), the method 200 includes determining, via the controller, an active power command signal for the IBR (e.g., the generator) based on a comparison of the power support signal and a power reference signal. Thus, the active power command signal is a difference between the power support signal and the power reference signal. The controller may, for example, receive the power reference signal from the higher-level controller.

[0054] As shown at (208), the method 200 further includes controlling, via the controller, the IBR (e.g., the DFIG) based, at least in part, on the active power command signal so as to emulate GFM control. In an embodiment, the IBR (e.g., the DFIG) may be controlled based further on a reactive power reference signal. As such,701070-WO-1 / GECW-1286-PCTone or more gate pulses for the power converter may be derived from the active power command signal and the reactive power command signal. The controller may, for example, receive the reactive power command signal from the higher-level controller.

[0055] The method 200 of FIG. 7 can be better understood with reference to FIGS. 8-10. In particular, FIGS. 8-9 illustrate schematic diagrams of a system for operating a GFL IBR connected to a power grid according to the present disclosure. More specifically, FIG. 8 illustrates a schematic diagram of an embodiment of a GFL power system 300 according to the present disclosure, particularly illustrating a one-line diagram of the for operating a GFL IBR to emulate GFM control of the IBR. FIG. 9 illustrates a schematic diagram of an embodiment of a function 400 for determining a power support signal according to the present disclosure.

[0056] As shown in the embodiment illustrated in FIG. 8, the GFL power system 300 may include many of the same features of FIG. 4 described herein, with components having the same reference characters representing like components. Further, as shown, the GFL power system 300 may include a control structure for controlling the line side converter that is similar to the control structure shown in FIG.1. More particularly, as shown, the line side converter control structure may include a DC voltage regulator 312 and a line current regulator 314. The DC voltage regulator 312 is configured to generate line-side current commands for the line current regulator 314. The line current regulator 314 then generates line-side voltage commands for a modulator 318. The modulator 318 also receives an output (e.g., a phase-locked loop angle) from a phase-locked loop 316 to generate one or more gate pulses for the line side converter 114. The phase-locked loop 316 typically generates its output using a voltage feedback signal.

[0057] Furthermore, as shown, the GFL power system 300 may also include a unique control structure for controlling the rotor side converter 112 to emulate GFM control. In particular, as shown in FIG. 8, the GFL power system 300 may include a function 400 for providing a power support signal Pgfmconfigured to emulate such GFM control. In addition, as shown, the GFL power system 300 may include a grid voltage / VAR regulator 302, a torque regulator 304, a rotor current regulator 308, and a modulator 310. In general, the GFL power system 300 is described herein with701070-WO-1 / GECW-1286-PCTreference to a higher-level controller being a turbine controller 26. However, it should be appreciated that the disclosed GFL power system 300 may be implemented with the higher-level controller being a farm-level controller 56 or any other suitable higher-level controller.

[0058] As shown in FIG. 8, the function 400 receives a frequency feedback signal C PLL. The function 400 is configured to output a power support signal Pgfin, as discussed further below. As shown, the power support signal Pgfm is compared to a power reference signal Pref, which may be received from a higher-level controller, to obtain an active power command signal Pcmd. The torque regulator 204 receives the active power command signal Pcmd. Moreover, the grid voltage / VAR regulator 302 may receive, e.g., from the higher-level controller, a reactive power reference signal Qref. Outputs from the grid voltage / VAR regulator 302 and the torque regulator 304 are commands (e.g., IRCmdy and IRCmdx) for rotor current, which are implemented in the rotor current regulator 308 by generating rotor voltage commands (e.g., VRCmdx and VRCmdy) for the modulator 310. The modulator 310 also receives a phase-locked loop angle from the phase-locked loop 316 and a rotor position feedback (0Fbk) to generate one or more gate pulses for the rotor-side converter 112.

[0059] As shown in the embodiment illustrated in FIG. 9, the function 400 receives the frequency feedback signal COPLL. The function 400 may apply a first gain 402 (e.g.. via multiplication) to the frequency feedback signal C PLL to obtain a first signal 404. In an embodiment, the first gain 402 may be fixed gain. In such an embodiment, the converter controller 120 may store the first gain 402 (e.g., in the memory devices 160 thereol). The first gain 402 may be determined to adjust sensitivity of the emulated GFM control.

[0060] The function 400 may further apply a low pass filter 406 to the frequency feedback signal COPLL to obtain a second signal 408. In an embodiment, a filter gain (k(Af)) may be a variable gain dependent on a difference betw een the frequency feedback signal COPLL and a nominal electrical frequency of the power grid. More particularly, the filter gain (k(Af)) may equal the first gain 402 when the difference between the frequency feedback signal COPLL and the nominal electrical frequency of the powder grid is zero. Further, in an embodiment, a time constraint (T(wr)) of the low-pass filter 406 may be configured to limit a duration of the second signal 408 as a701070-WO-1 / GECW-1286-PCTfunction of a feedback signal.

[0061] The speed feedback signal may be measured by the sensor(s) 68 and / or determined by the controller(s) 26. 56. 120, as discussed above. In general, the function 400 is described herein with reference to the feedback signal being a rotor speed feedback signal. However, it should be appreciated that the disclosed function 400 may be implemented with the feedback signal being a generator speed feedback signal or any other suitable feedback signal.

[0062] The function 400 determines the power support signal Pgfmbased on a comparison (e.g., via comparator 410) between the first signal 404 and the second signal 408. Thus, the power support signal Pgfmis a difference between the first signal 404 and the second signal 408. The power support signal Pgfm is configured to emulate GFM control for at least one of inertial power, phase jump power, and droop power in response to at least one of the frequency feedback signal COPLL and a phase jump of the power grid. That is, the power support signal Pgfm may represent a command from an inertial power regulator in a GFM power system. As such, using the power support signal Pgfmto determine the active power command signal Pcmd for the GFL power system 300 causes the GFL power system 300 to control inertial power, phase jump power, and droop power similar to GFM control in response to frequency deviations, and / or phase jumps of a power grid.

[0063] The function 400 may be further configured to apply a limit 412 on the power support signal Pgfm. The limit 412 may be a variable limit dependent on the feedback signal (e.g., the rotor speed feedback signal). For example, the limit 412 may be configured to limit an amount of kinetic energy that can be extracted from the wind turbine 10 based on the rotor speed feedback signal. As such, when the power support signal Pgfm, exceeds the limit 412. the function 400 may set the power support signal Pgfm to the limit 412.

[0064] Further aspects of the invention are provided by the subject matter of the following clauses:

[0065] A method for operating a grid-following inverter-based resource (IBR) connected to a power grid, the IBR having a controller, the method comprising: receiving, via the controller, a frequency feedback signal representative of an electrical frequency of the power grid; determining, via the controller, a power701070-WO-1 / GECW-1286-PCTsupport signal based on applying a function to the frequency feedback signal, the power support signal configured to emulate grid-forming control for at least one of inertial power, phase jump power, and droop power in response to at least one of the frequency feedback signal and a phase jump of the power grid; determining, via the controller, an active power command signal for the IBR based on the power support signal and a power reference signal; and controlling, via the controller, the IBR based, at least in part, on the active power command signal so as to emulate grid-forming control.

[0066] The method of any preceding clause, wherein determining, via the controller, the power support signal based on applying the function to the frequency feedback signal further comprises: determining, via the controller, a first signal based on applying a first gain to the frequency feedback signal; determining, via the controller, a second signal by applying a low-pass filter to the frequency feedback signal; and determining, via the controller, the power support signal based on a comparison of the first signal and the second signal.

[0067] The method of any preceding clause, wherein a time constraint of the low-pass filter is a variable time constraint dependent on a feedback signal.

[0068] The method of any preceding clause, wherein a filter gain of the low-pass filter is a variable gain dependent on a difference between the frequency feedback signal and a nominal electrical frequency of the power grid.

[0069] The method of any preceding clause, wherein the filter gain equals the first gain when the difference between the frequency feedback signal and the nominal electrical frequency of the power grid is zero.

[0070] The method of any preceding clause, further comprising limiting, via the controller, the power support signal by a limit.

[0071] The method of any preceding clause, wherein the limit is a variable limit dependent on a feedback signal.

[0072] The method of any preceding clause, wherein the first gain is a fixed gain.

[0073] The method of any preceding clause, further comprising controlling, via the controller, the IBR based further on a reactive power reference signal.

[0074] The method of any preceding clause, further comprising providing, via a higher-level controller, the power reference signal and the reactive power command701070-WO-1 / GECW-1286-PCTsignal.

[0075] An IBR connected to a power grid, the inverter-based resource comprising: at least one controller for controlling the inverter-based resource to provide grid-following control thereof, the controller comprising at least one processor, the at least one processor configured to perform a plurality of operations, the plurality' of operations comprising: receiving a frequency feedback signal representative of an electrical frequency of the power grid; determining a power support signal based on applying a function to the frequency feedback signal, the power support signal configured to emulate grid-forming control for at least one of inertial power, phase jump power, and droop power in response to at least one of the frequency feedback signal and a phase jump; determining an active power command signal for the IBR based on the power support signal and a power reference signal; and controlling the IBR based, at least in part, on the active power command signal so as to emulate grid-forming control.

[0076] The IBR of any preceding clause, wherein determining the power support signal based on applying the function to the frequency feedback signal further comprises: determining a first signal based on applying a first gain to the frequency feedback signal; determining a second signal by applying a low-pass filter to the frequency feedback signal; and determining the power support signal based on a comparison of the first signal and the second signal.

[0077] The IBR of any preceding clause, wherein a time constraint of the low-pass filter is a variable time constraint dependent on a feedback signal.

[0078] The IBR of any preceding clause, wherein a filter gain of the low-pass filter is a variable gain dependent on a difference between the frequency feedback signal and a nominal electrical frequency of the power grid.

[0079] The IBR of any preceding clause, wherein the filter gain equals the first gain when the difference betw een the electrical frequency of the pow er grid and the nominal electrical frequency is zero.

[0080] The IBR of any preceding clause, wherein the plurality of operations further comprises limiting the power support signal by a limit.

[0081] The IBR of any preceding clause, wherein the limit is a variable limit dependent on a feedback signal.701070-WO-1 / GECW-1286-PCT

[0082] The IBR of any preceding clause, wherein the first gain is a fixed gain.

[0083] The IBR of any preceding clause, wherein the plurality’ of operations further comprises controlling the IBR based further on a reactive power reference signal.

[0084] The IBR of any preceding clause, wherein the power reference signal and the reactive power command signal are provided by a higher-level controller.

[0085] This written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

701070-WO-1 / GECW-1286-PCTWHAT IS CLAIMED IS:

1. A method for operating a grid-following inverter-based resource (IBR) connected to a pow er grid, the IBR having a controller, the method comprising: receiving, via the controller, a frequency feedback signal representative of an electrical frequency of the pow er grid;determining, via the controller, a power support signal based on applying a function to the frequency feedback signal, the power support signal configured to emulate grid-forming control for at least one of inertial pow er, phase jump pow er, and droop power in response to at least one of the frequency feedback signal and a phase jump of the power grid;determining, via the controller, an active power command signal for the IBR based on the pow er support signal and a power reference signal; and controlling, via the controller, the IBR based, at least in part, on the active pow er command signal so as to emulate grid-forming control.

2. The method of claim 1. wherein determining, via the controller, the power support signal based on applying the function to the frequency feedback signal further comprises:determining, via the controller, a first signal based on applying a first gain to the frequency feedback signal;determining, via the controller, a second signal by applying a low-pass filter to the frequency feedback signal; anddetermining, via the controller, the power support signal based on a comparison of the first signal and the second signal.

3. The method of claim 2, wherein a time constraint of the low-pass filter is a variable time constraint dependent on a feedback signal.

4. The method of claim 2. wherein a filter gain of the low-pass filter is a variable gain dependent on a difference between the frequency feedback signal and a nominal electrical frequency of the powder grid.701070-WO-1 / GECW-1286-PCT5. The method of claim 4, wherein the filter gain equals the first gain when the difference between the frequency feedback signal and the nominal electrical frequency of the power grid is zero.

6. The method of claim 2, further comprising limiting, via the controller, the power support signal by a limit.

7. The method of claim 6, wherein the limit is a variable limit dependent on a feedback signal.

8. The method of claim 2. wherein the first gain is a fixed gain.

9. The method of claim 1, further comprising controlling, via the controller, the IBR based further on a reactive power reference signal.

10. The method of claim 9. further comprising providing, via a higher-level controller, the power reference signal and the reactive power command signal.

11. An inverter-based resource (IBR) connected to a power grid, the inverter-based resource comprising:at least one controller for controlling the inverter-based resource to provide grid-following control thereof, the controller comprising at least one processor, the at least one processor configured to perform a plurality of operations, the plurality of operations comprising:receiving a frequency feedback signal representative of an electrical frequency of the power grid;determining a power support signal based on applying a function to the frequency feedback signal, the power support signal configured to emulate grid-forming control for at least one of inertial power, phase jump power, and droop power in response to at least one of the frequency feedback signal and a phase jump;determining an active power command signal for the IBR based on the701070-WO-1 / GECW-1286-PCTpower support signal and a power reference signal; andcontrolling the IBR based, at least in part, on the active power command signal so as to emulate grid-forming control.

12. The IBR of claim 11, wherein determining the power support signal based on applying the function to the frequency feedback signal further comprises:determining a first signal based on applying a first gain to the frequency feedback signal;determining a second signal by applying a low-pass filter to the frequency feedback signal; anddetermining the power support signal based on a comparison of the first signal and the second signal.

13. The inverter-based resource of claim 12, wherein a time constraint of the low-pass filter is a variable time constraint dependent on a feedback signal.

14. The IBR of claim 12, wherein a filter gain of the low-pass filter is a variable gain dependent on a difference between the frequency feedback signal and a nominal electrical frequency of the power grid.

15. The IBR of claim 14, wherein the filter gain equals the first gain when the difference between the electrical frequency of the power grid and the nominal electrical frequency is zero.

16. The IBR of claim 12. wherein the plurality of operations further comprises limiting the power support signal by a limit.

17. The IBR of claim 16, wherein the limit is a variable limit dependent on a feedback signal.

18. The IBR of claim 12, wherein the first gain is a fixed gain.701070-WO-1 / GECW-1286-PCT19. The IBR of claim 11, wherein the plurality of operations further comprises controlling the IBR based further on a reactive power reference signal.

20. The IBR of claim 19, wherein the power reference signal and the reactive power command signal are provided by a higher-level controller.

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