System and method for coordinated frequency response of an inverter-based resource to grid frequency changes

Abstract

A method for operating a grid-forming (GFM) inverter-based resource (IBR) having a controller. The method includes receiving, via the controller, a control signal that is determined based on a first gain applied to a higher-level controller. The method also includes generating, via the controller, an output signal based on the control signal. In addition, the method includes adjusting the first gain to a first value in response to a frequency feedback signal exceeding a threshold. The first value is configured to reduce or eliminate changes in the control signal due to grid frequency.

Description

700649-WO-1 / GECW-1270-PCTSYSTEM AND METHOD FOR COORDINATED FREQUENCY RESPONSE OF AN INVERTER-BASED RESOURCE TO GRID FREQUENCY CHANGESFIELD

[0001] The present disclosure relates generally to operation of an inverter-based resource (IBR), such as a wind turbine generator, and more particularly, to systems and methods for controlling the IBR response to a change in grid frequency.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 ty pically 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 profile 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 ty pes: 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. Thus, the wind turbines simply inject the specified current into the grid based on the fundamental voltage waveforms. However, with the rapid growth of wind power systems, penetration into some grids has increased to the point where wind turbine generators have a significant impact on the grid voltage and frequency. When wind turbines are located in a weak700649-WO-1 / GECW-1270-PCT 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.

[0004] In addition, the reduction in the proportion of synchronous machines with respect to asynchronous machines, which determine the grid defining parameters voltage and frequency, have contributed to decreasing stability margins. The immediate consequence of the decreased stability margins is a grid collapse when subjected to voltage and frequency disturbances in the grid. To address this, many renewable resource machines, such as an inverter-based resource (IBR) configured as a doubly-fed induction generator in a wind turbine power system, operate in a “grid forming mode.”

[0005] In “grid-forming” (GFM) mode, the converters provide a voltage-source characteristic, where the angle and magnitude of the voltage are controlled to achieve the regulation functions needed by the grid. In GFM mode, the renewable resource may be controlled to operate as a virtual synchronous machine (V SM) having an inertial power regulator replicating synchronous machine behavior. Similar to an actual synchronous machine, this control exhibits an inertial response. Also, in GFM mode , the predominant system variables of frequency and terminal voltage magnitude are regulated. 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.

[0006] The basic control structure to achieve the above grid-forming 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 doubly-fed wind turbine generator are disclosed in PCT / US2020 / 013787 entitled “System and Method for Providing Grid- Forming Control for a Double-Feb Wind Turbine Generator.”700649-WO-1 / GECW-1270-PCT

[0007] To be effective, GFM IBRs must be able to maintain an internal voltage phasor that does not move quickly when there are changes in grid conditions, e.g., sudden addition / removal of loads, opening or closing of grid connections that lead to phase jumps and / or rapid change of frequency. Such events include, for example, low voltage ride through (LVRT), high voltage ride through (HVRT), multiple fault ride through (MFRT), and / or phase jump events. In other words, the power from the GFM IBR must be able to change suddenly to stabilize the grid, with a subsequent slow reset to power being commanded from a higher-level control function.

[0008] GFM IBRs inherently support grid frequency and angle stability’ in a similar way as synchronous machines. Therefore, a GFM IBR automatically changes power output to stabilize the grid with negligible time delays and without deadbands. However, a side effect of this inherent characteristic of GFM IBRs is that higher-level power regulating functions (i.e., higher-level controls) thereof may counteract this inherent response if not properly designed to avoid such counteraction.

[0009] Thus, a method and system are needed for controlling higher-level power regulating functions in a farm operating GFM IBRs in such a way to avoid counteracting the inherent power response of the GFM IBR.BRIEF DESCRIPTION

[0010] Aspects and advantages of the present 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 present disclosure.

[0011] In an aspect, the present disclosure is directed to a method for operating a grid-forming (GFM) inverter-based resource (IBR) having a controller. The method includes receiving, via the controller, a control signal that is determined based on a first gain applied to a higher-level controller. The method also includes generating, via the controller, an output signal based on the control signal. In addition, the method includes adjusting the first gain to a first value in response to a frequency feedback signal exceeding a threshold. The first value is configured to reduce or eliminate changes in the control signal due to grid frequency.

[0012] In another aspect, the present disclosure is directed to a wind turbine. The wind turbine includes a wind turbine generator configured as a GFM IBR connected700649-WO-1 / GECW-1270-PCT to a power grid. The wind turbine also includes a converter controller comprising at least one first processor, the at least one first processor configured to perform a plurality of first operations. The plurality of operations includes receiving a control signal. The plurality of operations also includes based on the control signal, generating an output signal to control the wind turbine generator. Further, the wind turbine includes a wind turbine controller comprising at least one second processor, the at least one second processor configured to perform a plurality of second operations. The plurality of second operations includes adjusting a first gain to a first value in response to a frequency feedback signal exceeding a threshold. The first value is configured to reduce or eliminate changes in the control signal due to grid frequency. The plurality of second operations also includes determining the control signal based on the first gain.

[0013] In another aspect, the present disclosure is directed to a wind turbine farm. The wind turbine farm includes a plurality of wind turbines. Each of the wind turbines includes a wind turbine generator configured as a GFM IBR connected to a power grid. Each of the wind turbines also includes a converter controller comprising at least one first processor, the at least one first processor configured to perform a plurality of first operations. The plurality of first operations includes receiving a control signal from a higher-level controller. The plurality' of first operations also includes generating an output signal to control the wind turbine generator based on the control signal. The control signal is determined based on a first gain applied to the higher-level controller being adjusted to a first value in response to a frequency feedback signal exceeding a threshold. The first value is configured to reduce or eliminate changes in the control signal due to grid frequency.

[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 present disclosure and, together with the description, serve to explain the principles of the present disclosure.BRIEF DESCRIPTION OF THE DRAWINGS700649-WO-1 / GECW-1270-PCT

[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 schematic diagram of an embodiment of a main circuit of a grid-forming system according to conventional construction;

[0017] FIG. 2 illustrates an example control diagram for providing grid-forming (GFM) control according to conventional construction;

[0018] FIG. 3 illustrates a perspective view of an embodiment of a wind turbine according to the present disclosure;

[0019] FIG. 4 illustrates a simplified, internal view of an embodiment of the nacelle of the wind turbine shown in FIG. 3;

[0020] FIG. 5 illustrates a schematic diagram of an embodiment of a wind turbine power system according to the present disclosure;

[0021] FIG. 6 illustrates a wind farm utilizing a plurality of the wind turbine power systems of FIG. 5;

[0022] FIG. 7 illustrates a block diagram of an embodiment of suitable components that may be included within a controller used as a converter controller, a turbine controller, or a farm-level controller according to the present disclosure;

[0023] FIG. 8 illustrates a schematic diagram of an embodiment of a system for providing grid-forming control of a double-fed generator of a wind turbine according to the present disclosure;

[0024] FIG. 9 illustrates an expanded block diagram of an embodiment of an inertial power regulator with frequency droop control according to the present disclosure;

[0025] FIG. 10 illustrates a simplified block diagram of an embodiment of main inputs and outputs of a turbine controller according to the present disclosure;

[0026] FIG. 11 illustrates a flow chart of an embodiment of a method for operating a renewable energy source having an inverter-based resource (IBR) system and controlled by a converter controller according to the present disclosure;

[0027] FIG. 12 illustrates a schematic diagram of an embodiment of a system that utilizes farm-level and / or turbine-level compensation according to the present disclosure;700649-WO-1 / GECW-1270-PCT

[0028] FIG. 13 illustrates a more detailed view of the turbine-level compensation functionality of FIG. 12; and

[0029] FIG. 14 illustrates a more detailed view of the farm-level compensation functionality of FIG. 12.DETAILED DESCRIPTION

[0030] Reference now will be made in detail to embodiments of the present disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the present disclosure, not limitation of the present 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 present 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.

[0031] In general, the present disclosure is directed to systems and methods for controlling an inverter-based resource (IBR) connected to a power grid, wherein the IBR is operated in a grid-forming (GFM) mode as a virtual synchronous machine (VSM). As used herein, inverter-based resources generally refer to electrical devices that can generate or absorb electric power through switching of power-electronic devices.

[0032] A general description of the control and operation of an IBR operated in GFM is provided below with reference to FIGS. 1-2. In particular, FIG. 1 illustrates a schematic diagram of an embodiment of a main circuit of a grid-forming system. As shown, the main circuit includes a power-electronic converter with connections on DC and AC sides. This converter receives gating commands from a controller that creates an AC voltage phasor Vcnv at an angle of Thvcnv. The angle is with respect to a reference phasor having a fixed frequency. The DC side is supplied with a device capable of generating or absorbing power for even a short duration. Such devices may include, for example, batteries, solar panels, rotating machines with a rectifier, or capacitors. In addition, as shown, the circuit includes an inductive impedance Xcnv700649-WO-1 / GECW-1270-PCT connecting the converter to its point of interconnection, show n as the voltage Vt and angle ThVt in FIG. 1. The electrical system behind the point of interconnect is shown as a Thevemn equivalent with impedance Zthev and voltage Vthev at angle ThVthev. This equivalent can be used to represent any circuit, including grid-connected and islanded circuits with loads. In practical situations, the impedance Zthev will be primarily inductive.

[0033] Still referring to FIG. 1, the closed-loop portion of the main control receives feedback signals from the voltage and current at the point of interconnection. Additional inputs are received from higher-level controls (not shown). While FIG. 1 illustrates a single converter as an example, any grouping of equipment that can create an electrical equivalent of a controlled voltage Vcnv behind an impedance Xcnv can have the control schemes disclosed applied to achieve the same performance benefits.

[0034] Referring now to FIG. 2, a control diagram for providing GFM control according to conventional construction is illustrated. As shown, a converter controller 1 receives references (e.g., Vref and Pref) and limits (e.g.. VcmdLimits and PcmdLimits) from higher-level controls 2. These high-level limits are on physical quantities of voltage, current, and pow er. The main regulators include a fast voltage regulator 3 and a slow pow er regulator 4. These regulators 3, 4 have final limits applied to the converter control commands for voltage magnitude (e.g., VcnvCmd) and angle (e.g.. 0pangand 0PLL) to implement constraints on reactive- and real- components of current, respectively. Further, such limits are based upon a predetermined fixed value as a default, w ith closed-loop control to reduce the limits should current exceed limits.

[0035] Grid-forming converter technology responds to changes in system generation / load in a similar way as conventional (e.g.. thermal) generation. Similar to conventional thermal generation, frequency droop is used in grid-forming converters to share loading among other parallel connected grid-forming resources. Unlike conventional pow er generation, however, the amount of power available from windturbines is less predictable due to variations in wind. The amount of support to system frequency in terms of active power is therefore constrained by local wdnd conditions.700649-WO-1 / GECW-1270-PCT

[0036] As mentioned above, an inherent characteristic of GFM IBRs is that they inherently support grid frequency and angle stability' in a similar way as synchronous machines. A GFM 1BR automatically changes power output to stabilize the grid with negligible time delays and without deadbands. The higher-level power regulating control functions, however, tend to counteract this inherent response. An aim of the present methodology is to minimize this disadvantageous counter effect.

[0037] As used herein. IBRs generally refer to electrical devices that can generate or absorb electric power through switching of power-electronic devices. Accordingly, IBRs may include wind turbine generators, solar inverters, energy -storage systems, STATCOMs, or hydro-power systems. For example, in an embodiment, the IBR may be a wind turbine power system having a rotor-side converter, a line-side converter, and a doubly -fed induction generator (DFIG) connected to the electrical grid.

[0038] Referring to the drawings, FIG. 3 illustrates a perspective view of an embodiment of a wind turbine 10 according to the present disclosure. The wind turbine 10 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 outw ardly 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 22 may 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. 4) positioned within the nacelle 16 to permit electrical energy to be produced.

[0039] The wind turbine 10 may also include a wind turbine controller 26 centralized within the nacelle 16. How ever, in other embodiments, the wind turbine 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 wind turbine 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 wind turbine controller 26 may include a computer or700649-WO-1 / GECW-1270-PCT other suitable processing unit. Thus, in several embodiments, the wind turbine controller 26 may include suitable computer-readable instructions that, when implemented, configure the wind turbine controller 26 to perform various different functions, such as receiving, transmitting and / or executing wind turbine control signals. Accordingly, the wind turbine 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.

[0040] Referring now to FIG. 4, a simplified, internal view of an embodiment of the nacelle 16 of the wind turbine 10 shown in FIG. 3 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.

[0041] The wind turbine 10 may also include one or more pitch drive mechanisms 32 communicatively coupled to the wind turbine controller 26, with each pitch adjustment 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 tow er 12 of the wind turbine 10).

[0042] 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 30, 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 and700649-WO-1 / GECW-1270-PCTRanging (“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.

[0043] Referring now to FIG. 5, 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 FIGS. 3 and 4, 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 present disclosure is not limited to wind turbine systems.

[0044] In the embodiment of FIG. 5, the rotor 18 of the wind turbine 10 may, optionally, be coupled to the gearbox 38, which is, in turn, coupled to a generator 102, which may be a DFIG. As shown, the generator 102 is connected to a stator bus 104. Further, as shown, a power converter 106 is 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 provides an output multiphase power (e.g., three-phase power) from a stator of the generator 102, and the rotor bus 108 provides an output multiphase power (e.g., three- phase power) from a rotor of the generator 102. The power converter 106 includes 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.

[0045] The RSC 112 and the LSC 114 are 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 1 12 and / or the line-side converter 114, as described herein. It should be noted that the converter700649-WO-1 / GECW-1270-PCT controller 120 may be configured as an interface between the power converter 106 and the wind turbine controller 26 and may include any number of control devices.

[0046] In typical configurations, various line contactors and circuit breakers including, for example, a grid breaker 122 are 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.

[0047] 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 108, sinusoidal multi -phase (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 are modulated to convert the AC power provided from the rotor bus 108 into DC power suitable for the DC link 116.

[0048] 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, switching elements (e.g., IGBTs) used in bridge circuits of the line-side converter 114 are 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).

[0049] 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 operational700649-WO-1 / GECW-1270-PCT considerations. Additional protection components may also be included in the wind turbine power system 100.

[0050] Moreover, the power converter 106 may receive control signals from, for instance, a higher-level control system (e.g., the turbine controller or a wind farm controller) 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 power 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.

[0051] The power 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.

[0052] Under some states, the bi-directional characteristics of the power converter 106, 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 the 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.

[0053] 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 adjusting700649-WO-1 / GECW-1270-PCT 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.

[0054] Referring to FIG. 6, the wind turbine power system 100 described herein may be part of a wind farm 150. As shown, the wind farm 150 may include a plurality of wind turbines 152. including the wind turbine 10 described above, and an overall farm-level controller 156. The individual turbine controllers of the respective plurality of wind turbines 152 are communicatively coupled to the farm-level controller 156, e.g., through a wired connection, such as by connecting the wind turbine controller 26 through suitable communicative links 154 (e.g., a suitable cable). Alternatively, the wind turbine controllers 26 may be communicatively coupled to the farm-level controller 156 through a wireless connection, such as by using any suitable wireless communications protocol known in the art. In further embodiments, the farm-level controller 156 is configured to send and receive control signals to and from the various wind turbines 152. such as for example, distributing real and / or reactive power demands across the wind turbines 152 of the wind farm 150.

[0055] Referring now to FIG. 7, 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 wind turbine controller 26. and / or the farm-level controller 156 described herein) is illustrated. The controller may include one or more processor(s) 158, computer, or other suitable processing unit and associated memory device(s) 160 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).

[0056] 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) 160 may generally include memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)),700649-WO-1 / GECW-1270-PCT computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and / or other suitable memory elements.

[0057] Such memory device(s) 160 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) 158, configure the controller to perform various functions as described herein. Additionally, the controller may also include a communications interface 162 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 164 (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) 158.

[0058] Referring now to FIG. 8, a schematic diagram of an embodiment of a system 200 for providing grid-forming control of a double-fed generator of a wind turbine is illustrated according to the present disclosure. In particular, FIG. 8 illustrates a one-line diagram of the double-fed wind turbine generator 102 with a high-level control structure for grid-forming characteristics.

[0059] As shown, the system 200 may include many of the same features of FIG. 5 described herein, with components having the same reference characters representing like components. As shown, the line-side converter 114 control structure may include a DC regulator 212 and a line current regulator 214. The DC regulator 212 is configured to generate line-side current commands for the line current regulator 214. The line current regulator 214 then generates line-side voltage commands for a modulator 218. The modulator 218 also receives an output (e.g., a phase-locked loop angle) from a phase-locked loop 216 to generate one or more gate pulses for the lineside converter 114. The phase-locked loop 216 typically generates its output using a voltage feedback signal.

[0060] Furthermore, as shown, the system 200 includes a control structure for controlling the rotor-side converter 112 using grid-forming characteristics. In particular, the system 200 may include a stator voltage regulator 206 for providing such grid-forming characteristics. In addition, as shown, the system 200 may include700649-WO-1 / GECW-1270-PCT a grid voltage / V AR regulator 202, an inertial power regulator 204, a rotor current regulator 208, and a modulator 210.

[0061] More particularly, the system 200 includes an inner-loop current-regulator structure and a fast stator voltage regulator to convert voltage commands from the grid-forming controls to rotor current regulator commands. Thus, the system provides control of the rotor voltage of the double-fed wind turbine generator 102 to meet a higher-level command for magnitude and angle of stator voltage. Such control is relatively fast and insensitive to current flowing in the stator of the double-fed wind turbine generator 102.

[0062] Furthermore, the inertial power regulator 204 of this system 200 implements various functions, including (1) following the active power reference supplied by the turbine control, and (2) sharing power among other parallel connected resources. Following the active power reference supplied by the turbine control is practically achieved through modification of the angle command to the stator voltage control, whereas sharing the power among other parallel connected resources is practically achieved through a frequency droop.

[0063] Referring now to FIG. 9, an expanded block diagram of the inertial power regulator 204 with frequency droop is provided according to the present disclosure. As shown, the frequency reference signal COREF and the phase lock loop frequency signal COPLL are combined to generate the frequency error signal E®. Specifically, theOPLI, signal, which represents the actual frequency of the IBR output is subtracted from the COREF signal in a summing junction 222 to generate the Emerror signal. The Eraerror signal is provided to a frequency control having a first control loop including a conventional proportional plus integral regulator 224 and a deadband control 226. The deadband control 226 provides some range of variation of the frequency error signal, for example, approximately 1 / 2 Hz without any change of output signal. This limits response due to natural fluctuations of the power system frequency. The proportional plus integral regulator 224 converts the error signal to a conventional bias signal which is applied to a summing junction 220.

[0064] A second loop includes a proportional droop circuit 228 which may be an amplifier with a fixed gain that receives the Eraerror signal and provides an immediate compensation signal to the summing junction 220, the compensation signal being700649-WO-1 / GECW-1270-PCT added to the output signal from the proportional plus integral regulator 224. The output 230 of the summing junction 220 is a power offset signal which is coupled to a summing junction 232 whose other input is the power reference signal PREF.Accordingly, the frequency offset signal from summing junction 220 serves to modify the power reference signal PREF. The purpose of such modification is to adjust the power reference signal PREF as a function of frequency shifts. More particularly, the intent of the system is to automatically adjust the power output of the IBR in response to imbalances in generation and load reflected as deviations in frequency.

[0065] Thus, as shown, the proportional droop circuit 228 modifies the power reference PREF from the turbine control by adding a droop term (i.e., the output 230 from summing junction 220) determined by the difference between the frequency reference and the actual frequency. Under normal conditions, the grid frequency is close to nominal and the droop term is zero. When there is an imbalance in generation and load, the grid frequency may deviate from nominal and the droop term will cause the power converter 106 to generate power different from the power reference PREF from the turbine control. The inertial power regulator 204 also introduces an inertial regulator 234 which modifies the pow er error signal to simulate the inertia and damping of synchronous machines.

[0066] If the pow er reference signal is modified by the frequency bias circuit, the resultant signal identified as PORD is developed at an output terminal of the summing junction 232 and applied to a summation circuit 236 where the commanded power or ordered power is compared to the measured output pow er PB of the system. Note here that the signal PB represents the real pow er developed at the output of the IBR. The output signal from the summation circuit 236 represents the power error signal which is applied to the inertial regulator 234. The signal developed by the inertial regulator as described above represents the desired frequency coi of the internal voltage Ei and, if the frequency is properly tracking, w ill be the same as the frequency COPLL. In this regard, the signal coi developed at the output of the inertial regulator 234 is summed in a summing junction 238 with the COPLL signal. Any difference between the phase lock loop frequency and the signal coi results in an error signal which is applied to aa integrator 240 to develop the SIT signal. In such embodiments, the integrator 240 may be a conventional type of integrator whose output signal SIT is an angle offset w hich700649-WO-1 / GECW-1270-PCT can be summed with the output signal from the phase lock loop to generate the output signal 0i.

[0067] Referring now to FIG. 10, a simplified, block diagram of the main inputs and outputs of the wind turbine controller 26 is provided according to the present disclosure. In an embodiment, an objective of the wind turbine controller 26 is to maximize power generated by the generator 102 based on available power from the wind that is within power constraint(s) (e.g.. PlimH and / or PlimL) imposed by a power setpoint limit (e g., PwrSet). Typically, the wind turbine controller 26 achieves this objective by regulating the speed and active power of the generator 102. For example, the wind turbine controller 26 can receive and regulate a speed feedback signal (e.g., SpdFbk) and a power feedback signal (e.g., PwrFbk). Thus, in an embodiment, the wind turbine controller 26 utilizes maximum power-point tracking algorithms to determine a power reference (e.g., POWER_Ref) to the converter controller 120 and a pitch command (e.g., PITCHCmd) to the pitch control to realize these control objectives.

[0068] Under normal grid conditions, the power setpoint (e.g., PwrSet) is set to nominal power rating of the generator 102. The wind turbine controller 26 adjusts pitch and converter power references to maximize the power output within the power setpoint constraints. Therefore, actual power may deviate significantly from the power setpoint limit based on wind conditions, but generally stays within the power constraints. Under curtailed conditions, the power setpoint is reduced below nominal power rating, but the controls continue to operate the same way and are constrained to a lower power. Note that the power setpoint may also be interpreted as a power limit, as the wind turbine controller 26 is allowed to produce as much power as possible within this constraint.

[0069] As explained above, an inherent characteristic of GFM IBRs (such as the wind turbine generators discussed above) is that they inherently support grid frequency and angle stability in a similar way as synchronous machines. A GFM IBR automatically changes power output to stabilize the grid with negligible time delays and without deadbands. The higher-level power regulating control functions, such as the wind turbine controller and farm-level controllers discussed above, tend to700649-WO-1 / GECW-1270-PCT counteract this inherent response. An aim of the present methodology' is to minimize this disadvantageous countereffect.

[0070] Referring now to FIGS. 11-14. a method 300 and a system 400 for operating a renewable energy source having an IBR controlled by a converter controller are illustrated according to the present disclosure. In particular, FIG. 11 depicts a flow chart of an embodiment of the method 300 in accordance with the present disclosure. FIGS. 12-14 illustrate example diagrams of the system 400 for practicing the method 300 in accordance with the present disclosure. Moreover, in an embodiment, the system 400 and method 300 are related to operating a GFM IBR. For purposes of explanation, the IBR is presented as a wind turbine power system having at least one power converter coupled to a generator, wherein the converter controller receives control signal(s) from a higher-level controller, such as a wind turbine controller and / or a farm-level controller. However, it should be appreciated that the disclosed method 300 may be implemented with any other suitable power generation systems having any other suitable configurations. In addition, one skilled in the art. using the disclosures provided herein, will appreciate that various steps of the methods disclosed herein can be omitted, rearranged, constrained, and / or adapted in various ways without deviating from the scope of the present disclosure.

[0071] Referring to FIG. 12, the converter controller 120 (communicatively coupled to the power converter 106 in FIG. 5) of the system 400 is schematically illustrated. The converter controller 120 may be configured as an interface between the power converter 106 and the wind turbine controller 26. Within the converter controller 120, a power reference signal (PwrRel) is received from a higher-level controller, such as the wind turbine controller 26 as shown. At 422, a frequency droop function may be performed based on a reference frequency signal (FrqRefl) and a frequency feedback signal (FrqFbkl) corresponding to the detected grid frequency and may modify the power reference signal (PwrRel) at the junction 418. The frequency droop function 422 may adjust the power reference signal (PwrRel) to support the grid frequency, like conventional droop control functions in other types of generators. An IBR power regulator 420 may receive the modified power reference signal, as well as a power feedback signal (PFbk) and may generate a reference power actuator signal (PrefActuator) that is usually a power angle signal used to adjust the700649-WO-1 / GECW-1270-PCT angle of the grid-forming voltage source created by the IBR. This power angle may be used to generate the bridge gate pulses of the power converter 106 directly or used to synthesize a voltage source through a stator voltage regulator (as in a dual-fed type generator system) (FIG. 5). The IBR power regulator 420 may also receive a power limit signal from a higher-level controller, such as an inertia power limit signal (Inertial PwrLmt) from the farm-level controller 156, as discussed in greater detail below. This IBR power regulator 420 may also be an inertial power regulator similar to the form shown in FIG. 9.

[0072] In general, feedback signals (e.g., power feedback signals, frequency feedback signals, speed 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.

[0073] Still referring to FIG. 12. the wind turbine controller 26 of the system 400 is schematically illustrated. A first power limit signal (PwrLmt) may be received from a higher-level controller, such as the farm-level controller 156 as shown. As shown in FIG. 13, the wind turbine controller 26 may include a local power constraint module 413 that generates a second power limit signal for the wind turbine controller 26. A minimum module 411 may be configured to determine a constrained power limit signal as a function of the first and second power limit signals.

[0074] Referring back to FIG. 12, at 416, a frequency droop function may be performed based on a reference frequency signal (FrqRef2) and a frequency feedback signal (FrqFbk2) corresponding to the detected grid frequency and may be used to modify the power limit signal (PwrLmt) (or the constrained power limit signal) at the junction 412. The modified power limit signal may be received by a turbine control circuitry 414. which generates the pow er reference signal (PwrRef) transmitted to the converter controller 120 (discussed above). Thus, the wind turbine controller 26 is considered as a “higher-level controller" to the converter controller 120.

[0075] FIG. 12 also schematically depicts a farm-level controller 156 that is higher-level to the wind turbine controller 26 and to the converter controller 120. The700649-WO-1 / GECW-1270-PCT farm-level controller 156 may receive a farm power reference signal (PrefFarm) for the entire wind farm. At 408, a frequency droop function may be performed based on a reference frequency signal (FrqRef3) and a frequency feedback signal (FrqFbk3) corresponding to the detected grid frequency and may be used to modify the farm power reference signal (PrefFarm) at a junction 402. The modified farm power reference signal may be received by a farm power regulator 404, which generates a total power requirement signal for the wind farm. At 406, a steady state power distribution of the total power signal may be made for the individual wind turbines, wherein the power limit signal (PwrLmt) discussed above may be generated and transmitted to the wind turbine controller 26.

[0076] The farm-level controller 156 may include an inertial power distribution function 410 that receives a farm inertial power request signal (PInrFarm) and an inertial power capability signal (Inertial PwrCap) from the individual wind turbine controllers 26, wherein an inertial power limit signal (Inertial PwrLmt) may be generated and transmitted to the individual converter controllers 120 (e g., for all of the wind turbines within the wind farm).

[0077] Still referring to FIG. 12, as discussed above, each of the converter controllers 120, wind turbine controllers 26, and farm-level controllers 156 may contain frequency droop functions 408, 416, 422. The frequency droop functions 416, 422 downstream of the farm-level control 156 may be essentially washed out over time to allow the farm-level control 156 to dictate farm droop response in steady - state. However, as discussed above, the GFM IBR (e.g., via the converter controller 120) inherently supports grid frequency and angle stability in a similar way as synchronous machines. The GFM IBR automatically changes power output to stabilize the grid with negligible time delays and without deadbands. A side effect of the higher-level power regulating functions (e g., the wind turbine controller 26 and farm-level controller 156) is that they may counteract this inherent fast response of the GFM IBR.

[0078] The method 300 and system 400 sen e to minimize or eliminate this counter effect of the higher-level controllers 120, 26 by adjusting one or more gains via one or more gain selectors 440, 458 within the wind turbine controllers 26 and / or the farm-level controllers 156, as depicted in FIG. 12.700649-WO-1 / GECW-1270-PCT

[0079] Referring to FIGS. 11-12, at step 302 in FIG. 11, the method 300 includes receiving, via the converter controller 120, a control signal that is determined at least in part based on a first gain applied to the higher-level controller. The control signal may also be determined based on a first frequency droop function performed on a detected grid frequency at a higher-level controller. The IBR may be a wind turbine generator, wherein the higher-level controller is a wind turbine controller 26, and the control signal received by the converter controller is a power reference signal (PwrRef) generated by the wind turbine controller 26. For example, referring to FIG. 12, the converter controller 120 receives the power reference signal (PwrRef) from the higher-level wind turbine controller 26, which was derived in part based on the first gain applied to the wind turbine controller 26.

[0080] Referring back to FIG. 11, as show n at step 304, the converter controller 120 generates an output signal based in part on the control signal. The output signal may also be generated based on a second frequency droop function performed on the detected grid frequency. Additionally, or alternatively, the converter controller 120 can generate the output signal based in part on an inertial power regulator, as explained above. For example, the converter controller 120 may modify the power reference signal (PwrRef) via the frequency droop function 422 performed on the detected grid frequency, as explained above. The converter controller 120 can then, for example, generate the reference power actuator signal (Pref) based on the modified power reference signal and the power feedback signal (PFbk), as explained above.

[0081] As shown at step 306, the first gain is adjusted to a first value in response to a frequency feedback signal (FrqFbk2) exceeding a threshold. For example, the higher-level controller can compare the frequency feedback signal (FrqFbk2) to the threshold. The threshold may be stored in the higher-level controller (e.g., in memory devices 160 thereof). The threshold may be specified by a manufacturer of the IBR and / or a component thereof or a provider of the electrical grid. The frequency feedback signal (FrqFbk2) may indicate a frequency, a rate of change of the frequency, or any other suitable frequency metric. As such, the threshold may specify a limit (e.g., a maximum value) of the frequency metric indicated by the frequency feedback signal (FrqFbk2).700649-WO-1 / GECW-1270-PCT

[0082] Furthermore, the first value may be stored in a look-up table, or the like, that associates gain values with control modes of the IBR. The look-up table may be stored by the higher-level controller (e.g., in the memory devices 160 thereof). In response to determining that the frequency feedback signal (FrqFbk2) exceeds the threshold, the gain selector 458 can access the look-up table and select the first value associated with the first gain in the look-up table.

[0083] In an embodiment, as shown in FIG. 13, the first gain may be a turbinelevel gain applied to one of a wind turbine speed regulator or a wind turbine power regulator. In response to the frequency feedback signal (FrqFbk2) exceeding the threshold, the higher-level controller can apply the first value of the first gain via the turbine control circuitry 414 to generate the power reference signal (PwrRef).

[0084] The first value reduces or eliminates changes in the control signal received by the converter controller 120 due to the detected grid frequency. In an embodiment, the first value may be a fixed value. As one example, the first value may be zero so as to freeze the control signal (i. e. , maintain a previous control signal for a certain amount of time) to allow for the converter controller 120 to stabilize the grid. In another embodiment, the first value may be a variable value dependent on at least one of a frequency feedback signal, a speed feedback signal, a power feedback signal, or functions thereof. The first value may be determined empirically (e.g., based on testing and / or simulation to determine a gain value that reduces changes in the control signal received by the converter controller 120 due to changes in the detected grid frequency).

[0085] Furthermore, in an embodiment, as shown in FIG. 13, the control signal may be determined based additionally on a second gain applied to the higher-level controller. In such an embodiment, the method 300 may include adjusting the second gain to a third value in response to the frequency feedback signal (FrqFbk2) exceeding the threshold. The third value may be stored in the look-up table. In response to determining that frequency feedback signal (FrqFbk2) exceeds the threshold, the gain selector 458 can access the look-up table and select the third value associated with the second gain in the look-up table.

[0086] In an embodiment, as shown in FIG. 13, the second gain may be a turbinelevel gain applied to another of the wind turbine speed regulator or the wind turbine700649-WO-1 / GECW-1270-PCT power regulator. In response to the frequency feedback signal (FrqFbk2) exceeding the threshold, the higher-level controller can apply the third value of the second gain via the turbine control circuitry 414 to generate the power reference signal (PwrRef). The third value further reduces or eliminates changes in the control signal received by the converter controller 120 due to changes in the detected grid frequency. The third value may be determined in the same manner as the first value, as explained above.

[0087] At a step 308, the method 300 may include, in response to the frequency feedback signal (FrqFbk2) being less than or equal to the threshold, adjusting the first gain to a second value. The second value may be stored in the look-up table. The higher-level controller can, for example, determine that frequency feedback signal (FrqFbk2) is below the threshold based on comparing the frequency feedback signal (FrqFbk2) to the threshold, as explained above. In response to determining that the frequency feedback signal (FrqFbk2) is less than or equal to the threshold, the gain selector 458 can access the look-up table and select the second value associated with the first gain in the look-up table. The higher-level controller can then apply the second value of the first gain via the turbine control circuitry 414 to generate the power reference signal (PwrRef).

[0088] The second value is configured to maximize power output by the IBR. The second value is greater than the first value. In an embodiment, the second value is a fixed value. In another embodiment, the second value is a variable value dependent on a frequency feedback signal, a speed feedback signal, a power feedback signal, or functions thereof. The second value may be determined empirically (e.g., based on testing and / or simulation to determine a gain value that maximizes power output by the IBR).

[0089] Furthermore, in an embodiment, the method 300 may include, in response to the frequency feedback signal (FrqFbk2) being less than or equal to the threshold, adjusting the second gain to a fourth value. The fourth value may be stored in the look-up table. In response to determining that the frequency feedback signal (FrqFbk2) being less than or equal to the threshold, the gain selector 458 can access the look-up table and select the fourth value associated with the second gain in the look-up table. The higher-level controller can then apply the fourth value of the second gain via the turbine control circuitry 414 to generate the power reference700649-WO-1 / GECW-1270-PCT signal (PwrRef). The fourth value is configured to further maximize power output by the IBR. The fourth value is greater than the third value. The fourth value may be determined in the same manner as the second value, as explained above.

[0090] Referring to FIG. 13, the frequency droop function 416 may be performed based on the frequency reference signal (FrqRef2) and the frequency feedback signal (FrqFbk2), as discussed above. In this embodiment, the frequency reference signal (FrqRef2) may be based on a filtered version of the grid frequency feedback. Additionally, the frequency reference signal (FrqRefl) supplied to the converter controller 120 (FIG. 12) may also be based on a filtered version of the grid frequency feedback, wherein a filter bandwidth of the frequency droop function 416 may be lower than a filter bandwidth of the frequency droop function 422. The frequency droop function 416 may be applied to the first power limit signal (PwrLmt) and may generally include one or more parameter settings defining the amount of power change from a deviation in grid frequency.

[0091] Still referring to FIG. 13, the first and second gains are intended to apply to a power and / or speed regulator in the turbine controls 414 to reduce or eliminate changes in the active power that would otherwise counteract the fast reaction of the converter to grid-frequency / phase angle changes. The gain selector 458 may function by adjusting a value of the gains, as explained above, to avoid the changes in power reference due only to changes in grid frequency / phase. For example, in an embodiment, the gain selector 458 may select a first value for the first gain when the frequency feedback signal (FrqFbk2) exceeds the threshold or a second value for the first gain when the frequency feedback signal (FrqFbk2) being less than or equal to the threshold, as explained above. Additionally, or alternatively, the gain selector 458 may select a third value for the second gain when the frequency feedback signal (FrqFbk2) exceeds the threshold or a fourth value for the second gain when the frequency feedback signal (FrqFbk2) being less than or equal to the threshold, as explained above. In this way, the power reference would normally match a power feedback under normal or unchanging grid frequency conditions, and the power regulators and energy balance controls would operate as normal. However, under changing grid frequency conditions, the power reference will temporarily show little700649-WO-1 / GECW-1270-PCT or no change so that the higher-level controller has little or no response to the frequency / phase angle event.

[0092] Referring back to FIG. 12, in another embodiment wherein the 1BR is a wind turbine generator, and the control signal is a power reference signal (PwrRef) generated by the wind turbine controller 26, the farm-level controller 156 may be considered as the higher-level controller, wherein this higher-level controller generates the power limit signal (PwrLmt) received and used by the wind turbine controller 26 to generate the control signal used by the converter controller 120. Thus, in this embodiment, the control signal is derived in part based on a third gain applied to the farm-level controller 156. The control signal may be further derived in part based on the frequency droop function 408 performed on the detected grid frequency at the farm level controller 156.

[0093] Referring to FIG. 14, the third gain may be a farm-level gain applied to a farm power feedback signal. Similar to the gain applied to the power regulator in the wind turbine controller 26, this gain is intended to apply to the farm power regulator 404 to reduce or eliminate power limit changes associated with fast gridfrequency / phase angle changes. By removing these specific changes in power limit from the power regulator, the farm-level controls 156 may avoid counteracting the response of the downstream converter controller 120. The gain selector 440 may function by adjusting a value of the third gain, as explained above, to counter the changes in power limit due only to fast changes in grid frequency / phase. For example, in an embodiment, the gain selector 440 may select a fifth value for the third gain when the frequency feedback signal (FrqFbk2) exceeds the threshold or a sixth value for the third gain when the frequency feedback signal (FrqFbk2) being less than or equal to the threshold. In such an example, the fifth value may further reduce or eliminate changes in the control signal received by the converter controller 120 due to changes in the detected grid frequency, and the sixth value may be configured to further maximize power output by the IBR. The sixth value may be greater than the fifth value. In this way, the power feedback would normally be less than or equal to the power limit under normal or unchanging grid frequency conditions, and the power regulators and energy balance controls w ould operate as normal. However, under changing grid frequency conditions, the pow er limit will temporarily show little or no700649-WO-1 / GECW-1270-PCT change so that the controller has little or no response to the fast frequency / phase angle event.

[0094] The present disclosure also encompasses an individual wind turbine having a wind turbine generator configured as a GFM IBR connected to a power grid and controlled by a converter controller 120. The wind turbine generator is configured for operation in accordance with any one or combination of the methods discussed above.

[0095] The present disclosure also encompasses various system and method embodiments for operating a wind turbine generator in a wind turbine farm having a plurality' of wind turbines connected to a power grid, wherein the wind turbines include a wind turbine controller 26 in communication with a farm-level controller 156. The wind turbine generators include a converter controller 120, all of which are discussed above.

[0096] The converter controller 120 may, for example, receive a first control signal determined by the wind turbine controller 26 based on a turbine-level gain applied to the wind turbine controller 26. Moreover, the wind turbine controller 26 may receive a second control signal determined by the farm-level controller 156 based on a farm-level gain applied to the farm-level controller 156. Furthermore, the converter controller 120 may generate an output signal based in part on the second control signal.

[0097] The turbine-level gain applied to the w ind turbine controller 26 may include any one or combination of the first and second gains discussed above. The farm-level gain applied to the farm-level controller 156 may include the third gain discussed above. Based on a comparison of the frequency feedback signal (FrqFbk2) to the threshold, the gains can be adjusted to either reduce or eliminate changes in the control signal received by the converter controller due to changes in the grid frequency or to maximize power output by the IBR, as discussed in detail above.

[0098] Likewise, the present disclosure encompasses a wind turbine farm having a plurality of wind turbines.

[0099] Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, as well as other known equivalents for each such methods and700649-WO-1 / GECW-1270-PCT feature, can be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or conducted in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0100] Various aspects and embodiments of the present disclosure are defined by the following clauses:

[0101] A method for operating a grid-forming (GFM) inverter-based resource (IBR) having a controller, the method comprising: receiving, via the controller, a control signal that is determined based on a first gain applied to a higher-level controller; generating, via the controller, an output signal based on the control signal; and adjusting the first gain to a first value in response to a frequency feedback signal exceeding a threshold, the first value being configured to reduce or eliminate changes in the control signal due to grid frequency.

[0102] The method of any preceding clause, wherein the IBR is a wind turbine generator, the higher-level controller is a wind turbine controller, and the control signal received by the controller is a power reference signal generated by the wind turbine controller.

[0103] The method of any preceding clause, further comprising in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value configured to maximize power output by the IBR. the second value being greater than the first value.

[0104] The method of any preceding clause, wherein the first value is configured to freeze the control signal.

[0105] The method of any preceding clause, further comprising determining the control signal based on a second gain applied to the higher-level controller, wherein first gain is applied to one of a speed regulator or a power regulator and the second gain is applied to the other of the speed regulator or the power regulator.700649-WO-1 / GECW-1270-PCT

[0106] The method of any preceding clause, further comprising adjusting the second gain to a third value in response to the frequency feedback signal exceeding the threshold, the third value being configured to further reduce or eliminate changes in the control signal received by the controller due to the grid frequency.

[0107] The method of any preceding clause, further comprising in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value and adjusting the second gain to a fourth value, the second value and the fourth value being configured to maximize power output by the IBR, wherein the second value is greater than the first value and the fourth value is greater than the third value.

[0108] The method of any preceding clause, wherein the IBR is a wind turbine generator and the control signal is a power reference signal generated by a wind turbine controller, wherein the higher-level controller is a farm-level controller that generates a power limit signal received by the wind turbine controller, the power limit signal being used by the wind turbine controller to generate the power reference signal.

[0109] The method of any preceding clause wherein the frequency feedback signal indicates one of a frequency or a rate of change of the frequency.

[0110] A wind turbine, comprising: a wind turbine generator configured as a GFM IBR connected to a power grid; a converter controller comprising at least one first processor, the at least one first processor configured to perform a plurality of first operations, the plurality of first operations comprising: receiving a control signal; based on the control signal, generating an output signal to control the wind turbine generator; and a wind turbine controller comprising at least one second processor, the at least one second processor configured to perform a plurality of second operations, the plurality of second operations comprising: adjusting a first gain to a first value in response to a frequency feedback signal exceeding a threshold, the first value being configured to reduce or eliminate changes in the control signal due to grid frequency; and determining the control signal based on the first gain.

[0111] The wind turbine of any preceding clause, wherein the plurality of second operations further comprises: determining the control signal based on a second gain applied to the wind turbine controller, wherein the first gain is applied to one of a700649-WO-1 / GECW-1270-PCT speed regulator or a power regulator and the second gain is applied to the other of the speed regulator or the power regulator.

[0112] The wind turbine of any preceding clause, wherein the plurality of second operations further comprises: adjusting the second gain to a third value in response to the frequency feedback signal exceeding the threshold, the third value being configured to further reduce or eliminate changes in the control signal received by the converter controller due to the grid frequency.

[0113] The wind turbine of any preceding clause, wherein the plurality of second operations further comprises: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value and adjusting the second gain to a fourth value, the second value and the fourth value being configured to maximize power output by the IBR, wherein the second value is greater than the first value and the fourth value is greater than the third value.

[0114] A wind turbine farm, comprising: a plurality of wind turbines, each of the wind turbines comprising: a wind turbine generator configured as a GFM IBR connected to a power grid; and a converter controller comprising at least one first processor, the at least one first processor configured to perform a plurality of first operations, the plurality of first operations comprising: receiving a control signal from a higher-level controller; and generating an output signal to control the wind turbine generator based on the control signal; wherein the control signal is determined based on a first gain applied to the higher-level controller being adjusted to a first value in response to a frequency feedback signal exceeding a threshold, the first value being configured to reduce or eliminate changes in the control signal due to grid frequency.

[0115] The wind farm of any preceding clause, wherein each of the w ind turbines further comprises a wind turbine controller, the wind turbine controller being the higher-level controller; wherein the wind turbine controller comprises at least one second processor, the at least one second processor configured to perform a plurality of second operations, the plurality of second operations comprising: adjusting the first gain to the first value in response to the frequency feedback signal exceeding the threshold; and determining the control signal based on the first gain.

[0116] The wind farm of any preceding clause, wherein the plurality of second operations further comprises: in response to the frequency feedback signal being less700649-WO-1 / GECW-1270-PCT than or equal to the threshold, adjusting the first gain to a second value configured to maximize power output by the IBR, the second value being greater than the first value.

[0117] The wind farm of any preceding clause, further comprising a farm-level controller, the farm-level controller being the higher-level controller and comprising at least one second processor, the at least one second processor configured to perform a plurality of second operations, the plurality of second operations comprising: adjusting the first gain to the first value in response to the frequency feedback signal exceeding the threshold; and determining a second control signal based on the first gain.

[0118] The wind farm of any preceding clause, wherein the plurality of second operations further comprises: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value configured to maximize power output by the IBR, the second value being greater than the first value.

[0119] The wind farm of any preceding clause, wherein each of the wind turbines further comprises a wind turbine controller comprising at least one third processor, the at least one third processor configured to perform a plurality of third operations, the plurality' of third operations comprising: receiving the second control signal from the farm-level controller; adjusting a second gain to a second value in response to the frequency feedback signal exceeding the threshold, the second value being further configured to reduce or eliminate changes in the control signal due to the grid frequency; and determining the control signal based on the second control signal and the second gain.

[0120] This written description uses examples to disclose the present disclosure, including the best mode, and also to enable any person skilled in the art to practice the present disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the present 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 from700649-WO-1 / GECW-1270-PCT the literal languages of the claims.

Claims

700649-WO-1 / GECW-1270-PCTWHAT IS CLAIMED IS:

1. A method for operating a grid-forming (GFM) inverter-based resource (IBR) having a controller, the method comprising: receiving, via the controller, a control signal that is determined based on a first gain applied to a higher-level controller; generating, via the controller, an output signal based on the control signal; and adjusting the first gain to a first value in response to a frequency feedback signal exceeding a threshold, the first value being configured to reduce or eliminate changes in the control signal due to grid frequency.

2. The method of claim 1. wherein the IBR is a wind turbine generator, the higher-level controller is a wind turbine controller, and the control signal received by the controller is a power reference signal generated by the wind turbine controller.

3. The method of claim 1. further comprising: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value configured to maximize power output by the IBR, the second value being greater than the first value.

4. The method of claim 1, wherein the first value is configured to freeze the control signal.

5. The method of claim 1, further comprising determining the control signal based on a second gain applied to the higher-level controller, wherein first gain is applied to one of a speed regulator or a power regulator and the second gam is applied to the other of the speed regulator or the power regulator.

6. The method of claim 5, further comprising: adjusting the second gain to a third value in response to the frequency feedback signal exceeding the threshold, the third value being configured to further reduce or eliminate changes in the control signal received by the controller due to the grid frequency.700649-WO-1 / GECW-1270-PCT7. The method of claim 6. further comprising: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value and adjusting the second gain to a fourth value, the second value and the fourth value being configured to maximize power output by the IBR, wherein the second value is greater than the first value and the fourth value is greater than the third value.

8. The method of claim 1, wherein the IBR is a w ind turbine generator and the control signal is a power reference signal generated by a wind turbine controller, wherein the higher-level controller is a farm-level controller that generates a power limit signal received by the wind turbine controller, the power limit signal being used by the wind turbine controller to generate the power reference signal.

9. The method of claim 1 , wherein the frequency feedback signal indicates one of a frequency or a rate of change of the frequency.

10. A wind turbine, comprising: a wind turbine generator configured as a GFM IBR connected to a power grid; a converter controller comprising at least one first processor, the at least one first processor configured to perform a plurality of first operations, the plurality of first operations comprising: receiving a control signal; based on the control signal, generating an output signal to control the wind turbine generator; and a wind turbine controller comprising at least one second processor, the at least one second processor configured to perform a plurality of second operations, the plurality of second operations comprising: adjusting a first gain to a first value in response to a frequency feedback signal exceeding a threshold, the first value being configured to reduce or eliminate changes in the control signal due to grid frequency; and determining the control signal based on the first gain.700649-WO-1 / GECW-1270-PCT11. The wind turbine of claim 10, wherein the plurality of second operations further comprises: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value configured to maximize power output by the IBR, the second value being greater than the first value.

12. The wind turbine of claim 10, wherein the plurality of second operations further comprises: determining the control signal based on a second gain applied to the wind turbine controller, wherein the first gain is applied to one of a speed regulator or a power regulator and the second gain is applied to the other of the speed regulator or the power regulator.

13. The wind turbine of claim 12, wherein the plurality of second operations further comprises: adjusting the second gain to a third value in response to the frequency feedback signal exceeding the threshold, the third value being configured to further reduce or eliminate changes in the control signal received by the converter controller due to the grid frequency.

14. The wind turbine of claim 13, wherein the plurality of second operations further comprises: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value and adjusting the second gain to a fourth value, the second value and the fourth value being configured to maximize power output by the IBR, wherein the second value is greater than the first value and the fourth value is greater than the third value.

15. A wind turbine farm, comprising: a plurality of wind turbines, each of the wind turbines comprising:700649-WO-1 / GECW-1270-PCT a wind turbine generator configured as a GFM IBR connected to a power grid: and a converter controller comprising at least one first processor, the at least one first processor configured to perform a plurality of first operations, the plurality of first operations comprising: receiving a control signal from a higher-level controller; and generating an output signal to control the wind turbine generator based on the control signal: wherein the control signal is determined based on a first gain applied to the higher-level controller being adjusted to a first value in response to a frequency feedback signal exceeding a threshold, the first value being configured to reduce or eliminate changes in the control signal due to grid frequency.

16. The wind turbine farm of claim 15, wherein each of the wind turbines further comprises a wind turbine controller, the wind turbine controller being the higher-level controller; wherein the wind turbine controller comprises at least one second processor, the at least one second processor configured to perform a plurality of second operations, the plurality of second operations comprising: adjusting the first gain to the first value in response to the frequency feedback signal exceeding the threshold; and determining the control signal based on the first gain.

17. The wind turbine of claim 16, wherein the plurality of second operations further comprises: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value configured to maximize power output by the IBR, the second value being greater than the first value.

18. The wind turbine farm of claim 15, further comprising a farm-level controller, the farm-level controller being the higher-level controller and comprising700649-WO-1 / GECW-1270-PCT at least one second processor, the at least one second processor configured to perform a plurality of second operations, the plurality of second operations comprising: adjusting the first gain to the first value in response to the frequency feedback signal exceeding the threshold; and determining a second control signal based on the first gain.

19. The wind turbine of claim 18, wherein the plurality of second operations further comprises: in response to the frequency feedback signal being less than or equal to the threshold, adjusting the first gain to a second value configured to maximize power output by the IBR, the second value being greater than the first value.

20. The wind turbine of claim 18, wherein each of the wind turbines further comprises a wind turbine controller comprising at least one third processor, the at least one third processor configured to perform a plurality of third operations, the plurality of third operations comprising: receiving the second control signal from the farm-level controller; adjusting a second gain to a second value in response to the frequency feedback signal exceeding the threshold, the second value being further configured to reduce or eliminate changes in the control signal due to the grid frequency; and determining the control signal based on the second control signal and the second gain.

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