System and method for coordinated frequency response of grid frequency variation based on inverter resources

Abstract

A system and method of operating a renewable energy source having an inverter-based resource (IBR) system and controlled by a power converter controller. The IBR system operates under grid formation mode (GFM) control. The power converter controller receives a control signal derived based on a frequency droop function performed on the detected grid frequency at the upstream controller. The power converter controller generates an output power actuator signal based on a frequency droop function performed at the power converter controller on the detected grid frequency. A first compensation is applied to the upstream controller that reduces or eliminates a change in the control signal received by the power converter controller due to a change in the grid frequency.

Description

[0001] The present disclosure relates generally to the operation of inverter-based resources (IBRs), such as wind turbine generators, and more particularly to systems and methods for controlling IBR responses to grid frequency changes. Background Art

[0002] Wind power is considered one of the cleanest and most environmentally friendly energy sources currently available, and wind turbines have garnered increasing attention in this regard. A modern wind turbine typically comprises a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture the kinetic energy of the wind using the known airfoil principle. For example, the rotor blades typically have an airfoil-like cross-sectional profile so that during operation, air flows over the blades, creating a pressure differential between the two sides. Consequently, a lift force acts on the blades, directed from the pressure side toward the suction side. This lift force generates torque on the main rotor shaft, which is typically meshed with a generator for generating electricity.

[0003] Wind turbines can be categorized into two types: fixed-speed and variable-speed turbines. Traditionally, variable-speed wind turbines are controlled as current sources connected to the power grid. In other words, variable-speed wind turbines rely on the grid frequency, detected by a phase-locked loop (PLL), as a reference and inject a specified amount of current into the grid. Traditional current source control of wind turbines is based on the assumption that the grid voltage waveform is a fundamental voltage waveform with a fixed frequency and amplitude, and that the penetration of wind power into the grid is sufficiently low to not cause disturbances to the grid voltage amplitude and frequency. Therefore, the wind turbine simply injects a specified current into the grid based on the fundamental voltage waveform. However, with the rapid growth of wind power systems, the penetration rate 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 weak grids, wind turbine power fluctuations can lead to increased variations in the amplitude and frequency of the grid voltage. These fluctuations can adversely affect the performance and stability of the PLL and wind turbine current control.

[0004] Furthermore, the reduced proportion of synchronous machines relative to asynchronous machines, which determine the grid's defining parameters of voltage and frequency, has also contributed to a reduction in stability margins. When the grid experiences voltage and frequency disturbances, the direct consequence of this reduced stability margin is grid collapse. To address this issue, many renewable energy machines, such as inverter-based resources (IBRs) configured as doubly-fed induction generators in wind turbine power systems, operate in "grid-forming mode."

[0005] In "Grid Forming Mode" (GFM), the converter provides a voltage source characteristic, where the angle and amplitude of the voltage are controlled to achieve the regulation function required by the grid. In GFM operation, renewable resources can be controlled to operate as virtual synchronous machines (VSMs) with inertial power regulators that replicate the behavior of synchronous machines. Similar to actual synchronous machines, this control exhibits an inertial response. Furthermore, in GFM mode control, the primary system variables of frequency and terminal voltage amplitude are regulated. Using this structure, current will flow according to the grid's needs, while the converter helps establish the voltage and frequency for the grid. This characteristic is comparable to that of traditional generators based on turbine-driven synchronous machines.

[0006] In the early 1990s, basic control structures to achieve the above-mentioned grid-forming objectives were developed and field-proven for battery systems (e.g., see U.S. Patent No. 5,798,633, entitled “Battery Energy Storage Power Conditioning System”). Applications to full-converter wind and solar generators are disclosed in U.S. Patent No. 7,804,184, entitled “System and Method for Control of a Grid-Connected Power Generating System,” and U.S. Patent No. 9,270,194, entitled “Controller for controlling a power converter.” Applications to grid-forming control for doubly-fed wind turbine generators are disclosed in PCT / US2020 / 013787, entitled “System and Method for Providing Grid-Forming Control for a Double-Feb Wind Turbine Generator.”

[0007] To improve efficiency, GFM inverter-based resources (IBRs) must be able to maintain internal voltage phasors that do not shift rapidly when there are changes in grid conditions, such as sudden addition / removal of load, opening or closing of grid connections that result in phase jumps and / or rapid changes in frequency. Such events include, for example, low voltage ride-through (LVRT), high voltage ride-through (HVRT), multiple fault ride-through (MFRT), and phase jump events. In other words, the power from the GFM resources must be able to change suddenly to stabilize the grid, with a subsequent slow reset of power commanded from a higher-level control function.

[0008] Grid-forming (GFM) IBRs inherently support grid frequency and angle stability in a similar manner to synchronous machines. Thus, GFM IBRs automatically vary power output to stabilize the grid with virtually no time delay and no deadband. However, a side effect of this inherent characteristic of GFM resources is that upstream power regulation functions (e.g., higher-level controls) of grid-forming resources can counteract this inherent response if not properly designed to avoid such counteraction.

[0009] Therefore, there is a need for a method and system to compensate for upstream power conditioning functions in a plant operating a GFM IBR in such a manner as to avoid canceling the inherent power response of the GFM IBR. Summary of the Invention

[0010] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0011] The present disclosure relates to a method and system for operating a renewable energy source having an inverter-based resource (IBR) system (which can be connected to a power grid or an islanded system) and controlled by a power converter controller. The method includes: operating the IBR system under grid forming mode (GFM) control; receiving, with the power converter controller, a control signal derived based on one of a frequency droop function or an inertial power regulator performed at an upstream controller on a detected grid frequency; generating, with the power converter controller, an output power actuator signal based in part on the frequency droop function performed at the power converter controller on the detected grid frequency; and applying a first compensation to the upstream controller, the first compensation reducing or eliminating variations in the control signal received by the power converter controller due to variations in the grid frequency.

[0012] In a particular embodiment, the IBR is a wind turbine generator, the upstream controller is a wind turbine controller, and the control signal received by the power converter controller is a power reference signal generated by the wind turbine controller. In this embodiment, the first compensation may be provided by a turbine-level power command compensation based on the detected grid frequency and the generator rotor speed feedback signal.

[0013] In an alternative embodiment of a wind turbine arrangement, said first compensation may be provided by a turbine level power or speed feedback compensation based on a wind turbine power feedback signal and said detected grid frequency.

[0014] In yet another embodiment of the wind turbine arrangement, the first compensation may be provided by the turbine stage power command compensation and the turbine stage power or speed feedback compensation.

[0015] In yet another embodiment, wherein the IBR is a wind turbine generator and the control signal is a power reference signal generated by the wind turbine controller, the upstream controller may be a plant-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. In this embodiment, the first compensation may be provided by a plant-level power command compensation based on the detected grid frequency. The plant-level power command compensation may also be based on a generated aggregate response estimate signal that predicts a collective response of the active power of a group of wind turbine generators in the plant to grid frequency variations.

[0016] In an alternative embodiment where the upstream controller is a plant level controller, the first compensation may be provided by a plant level power feedback compensation based on a plant power feedback signal and the detected grid frequency. The plant level power feedback compensation may also be based on the aggregated response estimate signal.

[0017] In yet another embodiment, wherein the upstream controller is the plant-level controller, the first compensation may be provided by a signal derived from the detected rate of change of grid frequency and applied to plant power regulation in the plant-level controller.

[0018] In yet another embodiment, wherein the upstream controller is the plant-level controller, the first compensation may be provided by any one or combination of: (a) the plant-level power command compensation based on the detected grid frequency; (b) the plant-level power feedback compensation based on the plant power feedback signal and the detected grid frequency; or (c) a signal derived from the rate of change of the detected grid frequency and applied to a plant power regulator in the plant-level controller.

[0019] The present invention also includes a method for operating a wind turbine generator in a wind turbine plant having a plurality of wind turbines connected to a power grid, the wind turbines having wind turbine controllers in communication with a plant-level controller, and the wind turbine generators having power converter controllers. The method includes: operating the wind turbine generator under grid forming mode (GFM) control; receiving, with the power converter controller, a first control signal derived by the wind turbine controller based on one of a frequency droop function or an inertial power regulator performed by the wind turbine controller on a detected grid frequency; receiving, with the wind turbine controller, a second control signal derived by the plant-level controller based on the frequency droop function performed by the plant-level controller on the detected grid frequency; generating, with the power converter controller, an output power actuator signal based on the frequency droop function performed by the power converter controller on the detected grid frequency; and applying a first compensation to the wind turbine controller and a second compensation to the plant-level controller, wherein the first compensation and the second compensation reduce or eliminate variations in the control signal received by the power converter controller due to variations in the grid frequency.

[0020] The present invention also includes a wind turbine comprising a wind turbine generator configured as an inverter-based resource (IBR) renewable energy source connected to a power grid and controlled by a power converter controller. The wind turbine generator is configured to operate according to any combination of the above-described method embodiments.

[0021] The present invention also includes a wind turbine plant having a plurality of wind turbines. Each wind turbine is a wind turbine generator configured as an inverter-based resource (IBR) connected to a power grid and controlled by a power converter controller. One or more of the wind turbine generators are configured to operate according to any of the above-described method embodiments.

[0022] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A complete and enabling disclosure of the invention, including the best mode thereof, to one skilled in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0024] Figure 1 A schematic diagram illustrating an embodiment of a main circuit of a grid forming system;

[0025] Figure 2 shows a control diagram for providing grid formation mode (GFM) control according to a conventional structure;

[0026] Figure 3 shows a perspective view of one embodiment of a wind turbine according to the present disclosure;

[0027] Figure 4 Shown Figure 3 A simplified interior view of one embodiment of a wind turbine nacelle is shown in FIG;

[0028] Figure 5 A schematic diagram illustrating one embodiment of a wind turbine power system according to aspects of the present disclosure is shown;

[0029] Figure 6 Shows the use of Figure 5 a wind farm comprising a plurality of wind turbine power systems;

[0030] Figure 7 A block diagram illustrating one embodiment of suitable components that may be included within a controller for use as a converter controller, a turbine controller, or a field level controller;

[0031] Figure 8 A system for providing grid forming control of a doubly-fed generator of a wind turbine is shown;

[0032] Figure 9 shows an expanded block diagram of an inertial power regulator using frequency droop control;

[0033] Figure 10 A simplified block diagram showing the main inputs and outputs of the turbine controller;

[0034] Figure 11 A flow chart illustrating an embodiment of a method according to the object of the present disclosure;

[0035] Figure 12 An embodiment of a system utilizing plant-level and / or turbine-level compensation according to aspects of the present disclosure is shown;

[0036] Figure 13 A more detailed view showing turbine stage compensation functionality; and

[0037] Figure 14 A more detailed view of the plant level compensation functionality is shown. DETAILED DESCRIPTION

[0038] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the present invention, rather than as a limitation of the present invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature shown or described as part of one embodiment may be used together with another embodiment to produce yet another embodiment. Therefore, the present invention is intended to cover such modifications and variations as fall within the scope of the appended claims and their equivalents.

[0039] In general, the present disclosure relates to systems and methods for controlling inverter-based resources (IBRs) connected to a power grid, wherein the IBRs operate as virtual synchronous machines (VSMs) in a grid-forming mode (GFM). As used herein, an inverter-based resource generally refers to an electrical device capable of generating or absorbing electrical power through the switching of power electronics.

[0040] Refer to the following Figure 1-2 Provides a general description of the control and operation of an IBR operating in a GFM.

[0041] Figure 1 is a schematic diagram of an embodiment of the main circuit of a grid forming system. As shown, the main circuit includes a power electronic converter with connections on the DC and AC sides. The converter receives a gating command from a controller, which generates an AC voltage phasor Vcnv at an angle Thvcnv. This angle is relative to a reference phasor with a fixed frequency. The DC side is supplied with devices that can generate or absorb power even for short durations. Such devices can include, for example, batteries, solar panels, rotating machines with rectifiers, or capacitors. In addition, as shown, the circuit includes an inductive impedance Xcnv connecting the converter to its interconnection point, as shown. Figure 1 The voltage Vt and angle ThVt are shown in Figure 1. The electrical system after the interconnection point is shown as a Thevenin equivalent, where the impedance Zthev and the voltage Vthev are at an angle ThVthev. This equivalent can be used to represent any circuit, including grid-connected circuits with loads and island circuits. In real-world situations, the impedance Zthev will be primarily inductive.

[0042] Still refer to Figure 1 The closed loop portion of the main control receives feedback signals from the voltage and current at the interconnection point. Additional inputs are received from higher level controls (not shown). Although Figure 1 A single converter is shown as an example, but any electrically equivalent group of devices that can produce a controlled voltage Vcnv across an impedance Xcnv can apply the disclosed control scheme to achieve the same performance benefits.

[0043] Now refer to Figure 2 , shows a control diagram for providing grid forming mode (GFM) control according to a conventional configuration. As shown, the converter controller 1 receives references (e.g., Vref and Pref) and limits (e.g., VcmdLimits and PcmdLimits) from a higher level control 2. These high level limits are physical quantities related to voltage, current, and power. The main regulator includes a fast voltage regulator 3 and a slow power regulator 4. These regulators 3, 4 have control functions applied to the voltage magnitude (e.g., VcnvCmd) and angle (e.g., θ Pang and θ PLL ) to achieve the final limit of the constraints on the reactive component and the real component of the current respectively. In addition, such limits are based on predetermined fixed values ​​as a default, wherein if the current exceeds the limit, the closed loop control is used to reduce the limit.

[0044] Grid-forming converter technology responds to changes in system generation / load in a similar manner to traditional (e.g., thermal) generation. Similar to traditional thermal generation, frequency droop is used in the grid-forming converter to share the load among other parallel-connected grid-forming resources. However, unlike traditional power generation, the amount of power available from wind turbines is less predictable due to wind variability. Therefore, the amount of support provided to system frequency in terms of active power is limited by local wind conditions.

[0045] As mentioned above, an inherent characteristic of GFM IBRs is that they inherently support grid frequency and angle stability in a similar manner to synchronous machines. GFMIBRs automatically vary power output to stabilize the grid with virtually no time delay and no deadband. However, upstream (higher-level) power regulation control functions tend to counteract this inherent response. The present approach aims to minimize this undesirable reaction.

[0046] As used herein, an inverter-based resource (IBR) generally refers to an electrical device capable of generating or absorbing power through the switching of power electronics. Thus, an inverter-based resource may include a wind turbine generator, a solar inverter, an energy storage system, a STATCOM, or a hydroelectric system. For example, in one embodiment, an inverter-based resource 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 power grid.

[0047] With reference to the accompanying drawings, Figure 3A perspective view of one embodiment of a wind turbine 10 according to the present disclosure is shown. 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 outward from the hub 20. For example, in the illustrated embodiment, the rotor 18 includes three rotor blades 22. However, in alternative embodiments, the rotor 18 may include more or less than three rotor blades 22. Each rotor blade 22 may be spaced about the hub 20 to facilitate rotating the rotor 18 so that kinetic energy from the wind can be converted into usable mechanical energy and subsequently into electrical energy. For example, the hub 20 may be rotatably coupled to an electrical generator 24 ( Figure 4 ), to allow the generation of electrical energy.

[0048] 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 external to the wind turbine 10. Furthermore, the controller 26 may be communicatively coupled to any number of components of the wind turbine 10 in order to control the operation of such components and / or implement corrective or control actions. Thus, 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 a variety of different functions, such as receiving, transmitting, and / or executing wind turbine control signals. Thus, the controller 26 may generally be configured to control various operating modes (e.g., startup or shutdown sequences), derate or uprate the wind turbine and / or individual components of the wind turbine 10.

[0049] Now refer to Figure 4 , showing Figure 3 , a simplified internal view of an embodiment of a nacelle 16 of a wind turbine 10 is shown in FIG. As shown, a generator 24 may be disposed within the nacelle 16 and supported on top of a base 46. Typically, the generator 24 may be coupled to the rotor 18 for generating electrical power from the rotational energy generated by the rotor 18. For example, as shown in the illustrated embodiment, the rotor 18 may include a rotor shaft 34 coupled to the hub 20 for rotation therewith. The rotor shaft 34 may, in turn, be rotatably coupled to a generator shaft 36 of the generator 24 via a gearbox 38. As is generally understood, in response to the rotation of the rotor blades 22 and the hub 20, the rotor shaft 34 may provide a low-speed, high-torque input to the gearbox 38. The gearbox 38 may then be configured to convert the low-speed, high-torque input into a high-speed, low-torque output to drive the generator shaft 36 and, thereby, the generator 24.

[0050] The wind turbine 10 may also have one or more pitch drive mechanisms 32 communicatively coupled to the wind turbine controller 26, wherein each pitch adjustment mechanism 32 is configured to rotate a pitch bearing 40 and, thereby, rotate the individual rotor blade(s) 22 about their respective pitch axis 28. Additionally, as shown, the wind turbine 10 may include one or more yaw drive mechanisms 42 configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging a yaw bearing 44 of the wind turbine 10, which is disposed between the nacelle 16 and the tower 12 of the wind turbine 10).

[0051] 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 the wind turbine 10 may be measured, such as by using a suitable weather sensor 66. Suitable weather sensors may include, for example, a light detection and ranging ("LIDAR") device, a sound detection and ranging ("SODAR") device, an anemometer, a wind vane, a barometer, a radar device (e.g., a Doppler radar device), or any other sensing device now known in the art or later developed that can provide wind direction information. Still other sensors 68 may be used to measure additional operating parameters of the wind turbine 10, such as voltage, current, vibration, etc., as described herein.

[0052] Now refer to Figure 5 , a schematic diagram of one embodiment of a wind turbine power system 100 is shown according to aspects of the present disclosure. Although reference will be made herein to Figure 3 and Figure 4 The present disclosure is generally described with reference to the wind turbine 10 shown in FIG. 1 , but one of ordinary skill in the art using the disclosure provided herein will appreciate that aspects of the present disclosure may also be applicable to other power generation systems and, as noted above, the present invention is not limited to wind turbine systems.

[0053] exist Figure 5In an embodiment of the present invention, the rotor 18 of the wind turbine 10 can be optionally coupled to a gearbox 38, which in turn is coupled to a generator 102, which can be a doubly fed induction generator (DFIG). As shown, the DFIG 102 is connected to a stator bus 104. Furthermore, as shown, a power converter 106 is connected to the DFIG 102 via a rotor bus 108 and to the stator bus 104 via a line-side bus 110. Thus, the stator bus 104 provides output multi-phase power (e.g., three-phase power) from the stator of the DFIG 102, and the rotor bus 108 provides output multi-phase power (e.g., three-phase power) from the rotor of the DFIG 102. The power converter 106 includes a rotor-side converter (RSC) 112 and a line-side converter (LSC) 114. The DFIG 102 is coupled to the rotor-side converter 112 via the rotor bus 108. Furthermore, 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.

[0054] The RSC 112 and the LSC 114 are configured for a normal operating mode in a three-phase pulse width modulation (PWM) arrangement using one or more switching devices (e.g., insulated gate bipolar transistor (IGBT) switching elements). Furthermore, the power converter 106 may be coupled to a converter controller 120 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.

[0055] In a typical configuration, various line contactors and circuit breakers, including, for example, grid disconnect 122, are included for isolating various components necessary for normal operation of DFIG 102 during connection to and disconnection from a load, such as a power grid 124. For example, system circuit breaker 126 may couple system bus 128 to transformer 130, which may be coupled to power grid 124 via grid disconnect 122. In alternative embodiments, fuses may replace some or all of the circuit breakers.

[0056] In operation, the AC power generated at the DFIG 102 by rotating the rotor 18 is provided to the power grid 124 via a dual path defined by the stator bus 104 and the rotor bus 108. On the rotor bus 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, the switching elements (e.g., IGBTs) used in the bridge circuit 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.

[0057] Furthermore, line-side converter 114 converts the DC power on DC link 116 into AC output power suitable for use with power grid 124. Specifically, switching elements (e.g., IGBTs) used in the bridge circuit of line-side converter 114 are modulated to convert the DC power on DC link 116 into AC power on line-side bus 110. The AC power from power converter 106 can be combined with power from the stator of DFIG 102 to provide multi-phase power (e.g., three-phase power) having a frequency that is substantially maintained at the frequency of power grid 124 (e.g., 50 Hz or 60 Hz).

[0058] In addition, various circuit breakers and switches (e.g., grid disconnect 122, system disconnect 126, stator synchronizing switch 132, converter disconnect 134, and line contactor 136) may be included in wind turbine power system 100 to connect or disconnect corresponding buses, for example, when excessive current is flowing and could damage components of wind turbine power system 100, or for other operational considerations. Additional protection components may also be included in wind turbine power system 100.

[0059] In addition, the power converter 106 may receive control signals via the converter controller 120, for example, from an upstream control system (e.g., a turbine controller or a wind farm controller). The control signals may be based on, among other things, sensed states or operating characteristics of the wind turbine power system 100. Generally, the control signals provide control over the operation of the power converter 106. For example, feedback in the form of sensed speed of the DFIG 102 may be used to control the conversion of 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 voltage and current feedback. Using various forms of feedback information, switching control signals (e.g., gate timing commands for IGBTs), stator synchronization control signals, and circuit breaker signals may be generated.

[0060] Power converter 106 also compensates or adjusts the frequency of the three-phase power from the rotor for variations in, for example, wind speed at hub 20 and rotor blades 22. Thus, mechanical and electrical rotor frequencies are decoupled, and electrical stator and rotor frequency matching is facilitated substantially independent of mechanical rotor speed.

[0061] Under certain conditions, the bidirectional nature of power converter 106, and in particular LSC 114 and RSC 112, facilitates feeding at least some of the generated electrical power back into the generator rotor. More specifically, electrical power can be transmitted from stator bus 104 to line-side bus 110, and then through line contactor 136 and into power converter 106, in particular LSC 114, which acts as a rectifier and converts the sinusoidal three-phase AC power into DC power. The DC power is transmitted into DC link 116. Capacitor 118 helps mitigate DC link voltage amplitude variations by helping to mitigate DC ripple sometimes associated with three-phase AC rectification.

[0062] The DC power is then transmitted to RSC 112, which converts the DC power into three-phase sinusoidal AC power by regulating voltage, current, and frequency. This conversion is monitored and controlled via converter controller 120. The converted AC power is transmitted from RSC 112 to the generator rotor via rotor bus 108. In this way, generator reactive power control is facilitated by controlling rotor current and voltage.

[0063] refer to Figure 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, for example, via a wired connection (e.g., by connecting the turbine controller 26 via a suitable communication link 154 (e.g., a suitable cable)). Alternatively, the turbine controller 26 may be communicatively coupled to the farm-level controller 156 via a wireless connection, for example, by using any suitable wireless communication 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, to distribute active and / or reactive power demands across the wind turbines 152 of the wind farm 150.

[0064] Now refer to Figure 7, shows a block diagram of one embodiment of suitable components that may be included within a controller, such as any of the converter controller 120, turbine controller 26, and / or farm-level controller 156 described herein. The controller may include one or more processors 158, computers, or other suitable processing units, and associated memory device(s) 160, which may include suitable computer-readable instructions that, when implemented, configure the controller to perform various functions, such as receiving, transmitting, and / or executing wind turbine control signals (e.g., performing the methods, steps, calculations, etc. disclosed herein).

[0065] As used herein, the term "processor" refers not only to what is known in the art as an integrated circuit included in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits, and other programmable circuits. In addition, the memory device(s) 60 may generally include (one or more) memory elements, including but not limited to computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, compact disk read-only memory (CD-ROM), magneto-optical disks (MODs), digital versatile disks (DVDs), and / or other suitable memory elements.

[0066] 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. Furthermore, the controller may also include a communication interface 162 for facilitating communication between the controller and various components of the wind turbine 10. The interface may include one or more circuits, terminals, pins, contacts, conductors, or other components for sending and receiving control signals. Furthermore, the controller may include a sensor interface 164 (e.g., one or more analog-to-digital converters) for allowing signals transmitted from the sensors 66, 68 to be converted into signals that can be understood and processed by the processor(s) 158.

[0067] Now refer to Figure 8 , shows a system 200 for providing grid forming control of a doubly-fed generator of a wind turbine. Specifically, Figure 8 A schematic diagram of one embodiment of a system 200 according to the present disclosure is shown, particularly showing a single-line diagram of a doubly-fed wind turbine generator 102 having an advanced control structure for grid forming characteristics.

[0068] As shown, system 200 may include the Figure 51 , where components with the same reference numerals represent similar 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 a line-side current command for the line current regulator 214. The line current regulator 214 then generates a line-side voltage command 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 line-side converter 114. The phase-locked loop 216 typically generates its output using a voltage feedback signal.

[0069] Furthermore, as shown, system 200 includes a control structure for controlling rotor-side converter 112 using the grid forming characteristic. Specifically, system 200 may include a stator voltage regulator 206 for providing such a grid forming characteristic. Furthermore, as shown, system 200 may include a grid voltage / VAR regulator 202, an inertia power regulator 204, a rotor current regulator 208, and a modulator 210.

[0070] More specifically, system 200 includes an inner-loop current regulator structure and a fast stator voltage regulator that converts voltage commands from grid forming control into rotor current regulator commands. Thus, the system provides control of the rotor voltage of doubly-fed wind turbine generator 102 to meet higher-level commands for the magnitude and angle of the stator voltage. Such control is relatively fast and insensitive to the current flowing in the stator of doubly-fed wind turbine generator 102.

[0071] Furthermore, the inertial power regulator 204 of the 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 actually achieved by modifying the angle command of the stator voltage control, while sharing power among other parallel-connected resources is actually achieved by frequency droop.

[0072] Now refer to Figure 9 , provides an expanded block diagram of the inertial power regulator 204 using frequency droop. As shown, the frequency reference signal ω REF and the phase-locked loop frequency signal ω PLL is constrained to generate a frequency error signal E ω Specifically, in the summing node 222, from ω REF The actual frequency of the inverter output is subtracted from the signal. PLL signal to generate E ω Error signal. E ωThe error signal is provided to a frequency control having a first control loop comprising a conventional proportional-plus-integral regulator 224 and a dead-band control 226. The dead-band circuit 226 provides some range of variation in the frequency error signal, for example, approximately 1 / 2 Hz, without any variation in the output signal. This limits the response due to the natural fluctuations in the power system frequency. The proportional-plus-integral regulator 224 converts the error signal into a conventional bias signal, which is applied to the summing junction 220.

[0073] The second loop includes a proportional droop circuit 228, which may be an amplifier with a fixed gain, which receives E ω The error signal is coupled to the summing node 220 and provides an instantaneous compensation signal which is added to the output signal from the proportional plus integral regulator 224. The output of the summing node 230 is a power offset signal which is coupled to the summing node 232. The other input of the summing node 232 is the power reference signal P REF Therefore, the frequency offset signal from the summing node 220 serves to modify the power reference signal P REF The purpose of this modification is to adjust the power reference signal P according to the frequency shift REF More specifically, the system is intended to try to keep the system output frequency constant so that if there is an error between the output frequency and the reference frequency, the power reference signal P REF is adjusted to compensate for frequency errors.

[0074] Thus, as shown, the proportional droop circuit 228 modifies the power reference P from the turbine control by adding a droop term (ie, output 230 from 220). REF , the droop term is determined by the difference between the frequency reference and the actual frequency. Under normal conditions, the grid frequency is close to the nominal value and the droop term is zero. When there is an imbalance in generation and load, the grid frequency may deviate from the nominal value, and the droop term will cause the power converter 106 to generate a power reference P different from the power reference P from the turbine control. REF The impact of this power deviation on turbine control can be an unexpected change in drive train speed, potentially leading to a trip of wind turbine 10.

[0075] Still refer to Figure 9 Inertia power regulator 204 also incorporates an inertia regulator 234, which modifies the power error signal to simulate the inertia of a synchronous machine. More specifically, inertia regulator 204 protects against sudden frequency or power changes, which, if experienced in the inverter output, could result in a transient torque being generated by a motor coupled to the inverter output. Inertia regulator 234 may comprise a conventional electronic circuit having the characteristics of a filter differential element, in that its output signal gradually increases in response to an increase in the input signal.

[0076] If the power reference signal is modified by the frequency bias circuit, a signal denoted as P is generated at the output terminal of the summing junction 232. ORD The resultant signal is applied to a summing circuit 236 where the command power or required power is combined with the measured output power P of the system. B Compare. Note here that the signal P B represents the active power produced at the inverter output. The output signal from the summing circuit 236 represents the power error signal applied to the inertial regulator 234. As described above, the signal generated by the inertial regulator represents the desired frequency ω1 of the internal voltage E1 and, if the frequency is tracked correctly, this signal will be consistent with the frequency ω PLL In this respect, the signal ω1 generated at the output of the inertial regulator 234 is summed at the summing junction 238 with ω PLL Any difference between the PLL frequency and the signal ω1 results in an error signal that is applied to the filter difference element 240 to produce δ IT In such an embodiment, the filter differential element 240 may be a conventional type of filter differential element, the output signal of which is IT is an angular offset that can be summed with the output signal from the phase-locked loop to generate the output signal θ1.

[0077] Now refer to Figure 10 , provides a simplified block diagram of the main inputs and outputs of the turbine controller 26. The main goal of the turbine controller 26 is to maximize the power generated by the generator 102 based on the available power from the wind and within the power constraints imposed by the power setpoint limit PwrSet. Typically, the turbine controller 26 achieves this goal by regulating the speed and active power of the generator 102. Therefore, the turbine controller 26 utilizes a maximum power point tracking algorithm to determine the power reference of the converter controller 120 and the pitch command of the pitch control to achieve these control goals.

[0078] Under normal grid conditions, the power set point (PwrSet) is set to the nominal rated power of the generator 102. The turbine controller 26 adjusts the pitch and converter power references to maximize power output within the power set point. Therefore, the actual power can deviate significantly from the set point based on wind conditions, but generally remains below the power set point. Under curtailment conditions, the power set point is reduced below the nominal rated power, but control continues to operate in the same manner, but is constrained to a lower power. Note that the power set point can also be interpreted as a power limit, as the controller is allowed to produce as much power as possible within the constraints.

[0079] As explained above, an inherent characteristic of GFMIBRs (such as the wind turbine generators discussed above) is that they inherently support grid frequency and angle stability in a manner similar to synchronous machines. GFMIBRs automatically vary their power output to stabilize the grid with virtually no time delay and no deadband. Upstream (higher-level) power regulation control functions (such as the wind turbine controllers and farm-level controllers discussed above) tend to counteract this inherent response. The present approach aims to minimize this undesirable reaction.

[0080] Figure 11 A flow chart of an embodiment 300 of a method according to the present invention for achieving the stated object is depicted. Figure 12-14 is a simplified diagram of an embodiment of a system 400 for practicing the method.

[0081] refer to Figure 11-14 , method 300 and system 400 relate to operating an IBR system under grid forming mode (GFM) control. 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 power converter controller receives control signal(s) from an upstream controller (e.g., a wind turbine controller and / or a wind farm controller). However, it should be appreciated that the disclosed method 300 may be implemented using any other suitable power generation system having any other suitable configuration. Furthermore, one skilled in the art, using the disclosure provided herein, will appreciate that various steps of the methods disclosed herein may be omitted, rearranged, constrained, and / or modified in various ways without departing from the scope of the present disclosure.

[0082] refer to Figure 12 , depicts a power converter controller 120 (coupled to Figure 5 106 in the wind turbine controller 26) and is configured as an interface between the power converter and the turbine controller 26. Within the controller 120, a power reference signal (PwrRef) is received from the wind turbine controller 26. At 422, a frequency droop function is performed based on the reference frequency signal (FrqRef1) and the frequency feedback signal (FrqFbk1) corresponding to the detected grid frequency and modifies the power reference signal at node 418. The frequency droop function adjusts the power reference signal to support the grid frequency, similar to traditional droop control functions in other types of generators. The IBR power regulator 420 receives the modified power reference signal and the power feedback signal (PFbk) and generates a reference power actuator signal (δ), which is typically a power angle signal for adjusting the angle of the voltage source formed by the grid generated by the IBR. This power angle can be used to directly generate bridge gate pulses for the power converter, or to synthesize a voltage source (such as in a doubly fed generator system) via a stator voltage regulator ( Figure 5The power regulator 420 may also receive an inertial power limit signal (InertialPwrLmt) from an upstream controller (e.g., the plant-level controller 156), as discussed in more detail below. The power regulator 420 may also be similar to Figure 9 Inertial power regulator of the form shown in .

[0083] Still refer to Figure 12 , schematically illustrating a wind turbine controller 26. A first power limit signal (PwrLmt) may be received from an upstream controller (eg, a plant level controller 156). Figure 13 As shown in FIG, the turbine controller 26 may include a local power constraint module 413 that generates a second power limit signal for the turbine controller 26. The minimum module 411 may be configured to determine a constrained power limit signal based on the first and second power limit signals.

[0084] The frequency droop function is performed between the reference frequency signal (FrqRef2) and the frequency feedback signal (FrqFbk2) corresponding to the detected grid frequency and is used to modify the power limit signal (PwrLmt) at node 412. Turbine control circuit 414 receives the modified power limit signal and generates a power reference signal (PwrRef), which is transmitted to power converter controller 120 (as described above). Therefore, wind turbine controller 26 is considered an "upstream controller" of power converter controller 120.

[0085] Figure 12 Also schematically depicted is a plant-level controller 156 upstream of the wind turbine controller 26 and the power converter controller 120. This controller 156 receives a plant power reference signal (PrefPlant) for the entire plant (wind farm). A frequency droop function is performed between the reference frequency signal (FrqRef3) and a frequency feedback signal (FrqFbk3) corresponding to the detected grid frequency and used to modify the plant power reference signal (PrefPlant) at node 402. The modified plant power reference signal is received by a plant power regulator 404, which generates a total power demand signal for the plant. At 406, a steady-state power distribution of the total power signal is performed among the individual wind turbines, wherein the aforementioned power limit signal (PwrLmt) is generated and transmitted to the wind turbine controller 26.

[0086] The plant-level controller 156 may include an inertial power allocation function 410 that receives the plant inertial power signal and an inertial power upper limit (cap) signal (InertialPwrCap) from the individual wind turbine controllers 26, generates an inertial power limit signal (InertialPwrLmt) and transmits it to the individual power converter regulators 120 (for all wind turbines within the wind farm).

[0087] refer to Figure 12 As described above, each of the converter control 120, wind turbine control 26, and plant-level control 156 includes frequency droop functionality. The frequency droop functionality downstream of the plant-level control 156 is essentially washed out over time, allowing the plant-level control 156 to dictate the plant droop response in steady state. However, as described above, the GFM IBR controller 120 inherently supports grid frequency and angle stability in a manner similar to synchronous machines. The GFM IBR automatically varies power output to stabilize the grid with virtually no time delay and no deadband. A side effect of upstream power regulation functionality (e.g., wind turbine controller 26 and plant-level controller 156) is that they counteract this inherent response of the GFM IBR.

[0088] The method 300 and system 400 serve to minimize or eliminate such adverse effects of the upstream controllers 120, 26 by adding compensation components 424, 426 within the wind turbine control 26 and / or plant level control 156, such as Figure 12 As described in .

[0089] refer to Figure 11-12 ,exist Figure 11 At step 302 of the method, the method includes operating the IBR system in a GFM control mode, as explained above. The IBR system may be a wind turbine generator, wherein the upstream controller is a wind turbine controller, and the control signal received by the power converter controller is a power reference signal generated by the wind turbine controller.

[0090] At step 304, the power converter controller 120 receives a control signal derived at least in part based on a first frequency droop function performed on a detected grid frequency at an upstream controller. Figure 12 , IBR power converter controller 120 receives a power reference signal (PwrRef) from upstream wind turbine controller 26 , which is derived based in part on a frequency droop function 416 executed in the wind turbine controller.

[0091] At step 306, the power converter controller generates an output power actuator signal based in part on a frequency droop function performed in the power converter controller on the detected grid-grid frequency. For example, the power converter controller 120 generates a reference power actuator signal (Pref) based on a modified power reference signal and a power feedback signal (PFbk).

[0092] At step 308 , a first compensation (e.g., turbine-level compensation 424 or plant-level compensation 426 ) is generated and applied to an upstream controller (e.g., one of wind turbine controller 26 or plant-level controller 156 ) that reduces or eliminates variations in the control signal received by power converter controller 120 due to variations in the detected grid frequency.

[0093] At step 310 , method 300 may include applying a second compensation (e.g., the other of turbine-level compensation 424 or plant-level compensation 426 ) to an additional upstream controller (e.g., the other of wind turbine controller 26 or plant-level controller 156 ) that further reduces or eliminates variations in control signals received by the power converter controller due to variations in grid frequency.

[0094] In a particular embodiment of method 300, the first compensation functionality may be Figure 13 The turbine stage compensation functionality is depicted in . Figure 13 As discussed above, the frequency droop function 416 is performed based on the frequency reference signal (FrqRef2) and the frequency feedback signal (FrqFbk2). In this embodiment, the frequency reference signal (FrqRef2) may be based on a filtered version of the grid frequency feedback. In addition, the frequency reference signal (FrqRef2) supplied to the power converter control 120 ( Figure 12 ) can also be based on a filtered version of the grid frequency feedback, where the filter bandwidth of the first frequency droop function 416 can be lower than the filter bandwidth of the second frequency droop function 418. The first frequency droop function 416 is applied to the power limit signal 406 and generally includes one or more parameter settings that define the amount of power change based on the grid frequency deviation.

[0095] Still refer to Figure 13 , turbine stage compensation functionality 424 ( Figure 12) can be provided by turbine-level power command compensation 460 based on the expected response of the downstream power converter control 120, together with the wind turbine controller 26 response itself, so that the overall wind turbine generator response to the grid frequency follows the target overall system response of the wind turbine generator. Power command compensation 460 can use the grid frequency feedback signal (FrqFbk2) and the generator rotor speed feedback signal (SpdFbk) to generate a power variation signal, which can be used at the input (at node 415) and / or output (at node 452) of the corresponding turbine controller 414 to minimize or eliminate changes in the power reference output signal (PwrRef) caused by grid frequency changes (thereby fully allowing the downstream power converter control 120 to manage grid support functions independently without interference from the energy balancing functionality of the wind turbine control 126). Therefore, the design of power command compensation may also require consideration of the control structure and design settings of the energy balancing controller. Under normal or unchanged grid frequency conditions, the power variation signal will be zero, and power regulation and energy balancing functions will function normally.

[0096] In another embodiment, again referring to Figure 13 , turbine stage compensation functionality 424 ( Figure 12 ) may be provided by a turbine level power or speed feedback compensation 458 which receives a wind turbine power feedback signal (PFbk) or a wind turbine speed feedback signal (SpFbk) and a sensed grid frequency feedback signal (FrqFbk2). This compensation function is intended to provide a power or speed feedback signal to the turbine control 414 that reduces or eliminates variations in active power feedback associated with grid frequency / phase angle variations. By removing these specific power variations from the feedback power, the wind turbine controller 26 may avoid canceling the response of the downstream power converter controller 120. This component 458 may operate by simulating the power converter regulator 420 ( Figure 12 ) to estimate the power change due solely to grid frequency / phase changes (e.g., as done in conventional generator swing equations). In this way, under normal or unchanged grid frequency conditions, the compensated power feedback will generally match the actual power feedback, and the power regulator and energy balance control will operate normally. However, under varying grid frequency conditions, the compensated power feedback will temporarily show little or no change in active power, causing the controller to have little or no response to frequency / phase angle events.

[0097] In certain embodiments, turbine stage compensation functionality 424 ( Figure 12 ) may be provided by a combination of the turbine stage power command compensation 460 and the turbine stage power feedback compensation 458 discussed above.

[0098] refer to Figure 12 In another embodiment, where the IBR is a wind turbine generator and the control signal is a power reference signal generated by wind turbine controller 26, plant-level controller 156 can be considered an upstream controller that generates a power limit signal received and used by wind turbine controller 26 to generate a power reference signal (control signal) used by power converter regulator 120. Thus, in this embodiment, the control signal is derived based in part on a frequency droop function performed at the plant-level controller (upstream controller) on the detected grid frequency. In this embodiment, the first compensation function can be provided by plant-level compensation functionality 426 at plant-level controller 156.

[0099] refer to Figure 14 , plant-level compensation can be provided by a plant-level power command compensation 444. The input to this compensation 444 is the detected frequency feedback signal (FrqFbk3), and the output is a power change signal that can be used at the input (at node 430) and / or output (at node 434) of the corresponding plant power regulator 404. Under constant frequency conditions, the power change signal is zero. The power compensation function is based on the expected response of the downstream control together with the power regulator response itself, so that the response of the entire system to the frequency follows the target overall system response. The configuration of the plant-level power command compensation 444 can be adjusted based on input from the aggregate response estimate 442, which predicts the collective response of the active power of a group of wind turbine generators in the plant to changes in grid frequency. The input to the aggregate response estimate function 442 may include one or more feedbacks from individual IBR units and may include: status signals (online or offline); virtual inertia settings / capabilities, where the turbine is operating as a GFM or GFL resource; or other operating point information (speed / power, etc.)

[0100] The structure for plant-level power command compensation can include multiple parallel paths, for example, one path for small signal frequency changes with relatively small limits on power changes, and another path for large changes in phase and / or frequency (which may include frequency deadbands and / or rate limits). If multiple paths are used, the outputs are summed together to obtain the total power change signal. A practical implementation can include one or more washout filters with dynamic gains, filter time constants, and limits that are dynamically scaled based on the possible power and wind turbine generator conditions.

[0101] Still refer to Figure 14In another embodiment, the first compensation may be provided by a plant-level power feedback compensation 440 based on the plant power feedback signal (PFbk) and the detected grid frequency (FrqFbk3). Similar to the power feedback compensation in the wind turbine controller, this function is intended to provide a power feedback signal to the plant power regulator to reduce or eliminate power variations associated with grid frequency / phase angle variations. By removing these specific power variations from the feedback power, the plant-level control 156 can avoid offsetting the response of the downstream power converter control 120. The component 440 may operate by simulating the power converter regulator 420 ( Figure 12 ) to estimate the power variation due solely to changes in grid frequency / phase. For example, plant-level power feedback compensation can include modeling a collection of inverter-based resources as a single lumped generator using conventional generator swing equations. Utilizing grid frequency feedback as input and assumptions about equivalent reactance, the power variation due to grid frequency can be estimated and used to compensate for the actual power feedback. Similarly, the gain of the swing equation can be adjusted based on feedback on the state, operating point, and capabilities of the collection of IBRs controlled by the plant-level regulator.

[0102] The configuration of plant-level power feedback compensation 440 may be adjusted based on input from aggregate response estimate 442 , which predicts the collective response of active power of a group of wind turbine generators in a plant to grid frequency variations.

[0103] Still refer to Figure 14 In another embodiment, the first compensation can be provided by a signal derived from the rate of change of the detected grid frequency (RoCoF) applied to the plant power regulator 404. This functionality can serve to freeze the plant power regulator 404 based on the rate of change of the grid frequency. Due to communication delays from the plant-level control 156 to the wind turbine generator, it may be desirable to freeze the plant power regulator 404 in response to severe frequency events caused by the very fast response of the wind turbine generator. When the RoCoF signal is zero for a predefined period of time, the regulator 404 can be unfrozen to resume plant-level power regulation.

[0104] Yet another embodiment includes providing a first compensation based on any combination of: (a) a plant level power command compensation 444; (b) a plant level power feedback compensation 440; or (c) a signal derived from a detected rate of change of grid frequency applied to the plant power regulator 404.

[0105] The present invention also includes various system and method embodiments for operating a wind turbine generator in a wind turbine plant 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 plant-level controller 156. The wind turbine generator includes a power converter controller 120, all of which are discussed above.

[0106] The wind turbine generator operates under grid forming mode (GFM) control, and power converter controller 120 receives a first control signal derived by wind turbine controller 26 based on a frequency droop function performed by the wind turbine controller on a detected grid frequency. Wind turbine controller 26 receives a second control signal derived by plant-level controller 156 based on a frequency droop function performed by plant-level controller 156 on a detected grid frequency. Power converter controller 120 generates an output power actuator signal based in part on the frequency droop function performed by the power converter controller on the detected grid frequency.

[0107] The first compensation is provided to the wind turbine controller 26 and may include any one or a combination of the turbine-level compensations discussed above. The second compensation is provided to the plant-level controller 156 and may include any one or a combination of the plant-level compensations discussed above. The first and second compensations reduce or eliminate variations in the control signals received by the power converter controller due to variations in grid frequency, as discussed in detail above.

[0108] The present invention also includes an individual wind turbine having a wind turbine generator configured as an inverter-based resource (IBR) renewable energy source connected to a power grid and controlled by a power converter controller. The wind turbine generator is configured to operate according to any one or a combination of the methods discussed above.

[0109] Likewise, the present disclosure includes a wind turbine plant having a plurality of wind turbines.

[0110] Further aspects of the invention are provided by the subject matter of the following clauses:

[0111] Item 1: A method for operating a renewable energy source having an inverter-based resource (IBR) system (which may be connected to a power grid or in an islanded system) and controlled by a power converter controller, the method comprising: operating the IBR system under grid forming mode (GFM) control; receiving, with the power converter controller, a control signal derived based on one of a frequency droop function or an inertial power regulator performed on a detected grid frequency at an upstream controller; generating, with the power converter controller, an output power actuator signal based on the frequency droop function performed on the detected grid frequency at the power converter controller; and applying a first compensation to the upstream controller, the first compensation reducing or eliminating variations in the control signal received by the power converter controller due to variations in the grid frequency or phase angle.

[0112] Clause 2: The method of clause 1, wherein the IBR is a wind turbine generator, the upstream controller is a wind turbine controller, and the control signal received by the power converter controller is a power reference signal generated by the wind turbine controller.

[0113] Clause 3: The method of clause 1 or 2, wherein the first compensation is provided by a turbine stage power command compensation based on the detected grid frequency.

[0114] Clause 4: The method of any of clauses 1-3, wherein the first compensation provided by the turbine stage power command compensation is also based on a generator rotor speed feedback signal.

[0115] Clause 5: The method of any of clauses 1-4, wherein the first compensation is provided by a turbine level power or speed feedback compensation based on a wind turbine power or speed feedback signal and the detected grid frequency.

[0116] Clause 6: The method of any one of clauses 1-5, wherein the first compensation is provided by a turbine stage power command compensation based on the detected grid frequency and a turbine stage power feedback compensation based on a wind turbine power feedback signal and the detected grid frequency.

[0117] Clause 7: The method of any one of clauses 1-6, wherein the IBR is a wind turbine generator and the control signal is a power reference signal generated by the wind turbine controller, wherein the upstream controller is a plant-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.

[0118] Clause 8: The method of any of clauses 1-7, wherein the first compensation is provided by a plant-level power command compensation based on the detected grid frequency.

[0119] Clause 9: A method according to any one of clauses 1-8, wherein the plant-level power command compensation is further based on an aggregate response estimate signal, which predicts the collective response of the active power of a group of wind turbine generators in the plant to changes in grid frequency.

[0120] Clause 10: The method of any one of clauses 1-9, wherein the first compensation is provided by a plant-level power feedback compensation based on a plant power feedback signal and the detected grid frequency.

[0121] Clause 11: A method according to any one of clauses 1-10, wherein the plant-level power feedback compensation is further based on an aggregate response estimate signal, which predicts the collective response of the active power of a group of wind turbine generators in the plant to changes in grid frequency.

[0122] Clause 12: The method of any of clauses 1-11, wherein the first compensation is provided by a signal derived from the detected rate of change of grid frequency, the signal being applied to a plant power conditioner in the plant-level controller.

[0123] Clause 13: A method according to any one of clauses 1-12, wherein the first compensation is provided by one or more of: (a) a plant-level power command compensation based on the detected grid frequency; (b) a plant-level power feedback compensation based on a plant power feedback signal and the detected grid frequency; or (c) a signal derived from the rate of change of the detected grid frequency applied to a plant power conditioner in the plant-level controller.

[0124] Clause 14: A method for operating a wind turbine generator in a wind turbine plant, the wind turbine plant having a plurality of wind turbines connected to a power grid, the wind turbines having wind turbine controllers in communication with a plant-level controller, the wind turbine generators having power converter controllers, the method comprising: operating the wind turbine generators under grid forming mode (GFM) control; receiving, with the power converter controller, a first control signal derived by the wind turbine controller based on a frequency droop function performed on a detected grid frequency; receiving, with the wind turbine controller, a second control signal derived by the plant-level controller based in part on the frequency droop function performed at the plant-level controller on the detected grid frequency; generating, with the power converter controller, an output power actuator signal based in part on a frequency droop function or an inertial power regulator performed at the power converter controller on the detected grid frequency; and applying a first compensation to the wind turbine controller and a second compensation to the plant-level controller, wherein the first compensation and the second compensation reduce or eliminate variations in the control signal received by the power converter controller due to variations in the grid frequency.

[0125] Clause 15: The method of clause 14, wherein the first compensation is provided by one or both of a turbine stage power command compensation based on the detected grid frequency or a turbine stage power feedback compensation based on a wind turbine power feedback signal and the detected grid frequency.

[0126] Clause 16: A method according to clause 14 or 15, wherein the second compensation includes one or more of the following: (a) a plant-level power command compensation based on the detected grid frequency; (b) a plant-level power feedback compensation based on a plant power feedback signal and the detected grid frequency; or (c) a signal derived from the rate of change of the detected grid frequency applied to a plant power conditioner in the plant-level controller.

[0127] Clause 17: The method of any one of clauses 14-16, wherein the plant-level power command compensation is further based on an aggregate response estimate signal that predicts a collective response of the active power of a group of the wind turbine generators in the plant to grid frequency variations.

[0128] Clause 18: A method according to any of clauses 14-17, wherein the plant-level power feedback compensation is further based on an aggregate response estimate signal, which predicts the collective response of the active power of a group of wind turbine generators in the plant to grid frequency changes.

[0129] Clause 19: A wind turbine comprising: a wind turbine generator configured as an inverter-based resource (IBR) renewable energy source connected to a power grid and controlled by a power converter controller; and wherein the wind turbine generator is configured to operate in accordance with the method of any one of clauses 14-18.

[0130] Clause 20: A wind turbine plant comprising: a plurality of wind turbines; each of the wind turbines comprising a wind turbine generator, the wind turbine generator configured as an inverter-based resource (IBR) renewable energy source connected to a power grid and controlled by a power converter controller; and wherein the wind turbine generator is configured to operate in accordance with the method of any one of clauses 14-18.

[0131] This written description uses examples, including the best mode, to disclose the invention and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples include structural elements that do not differ from the literal language of the claims, or if such other examples include equivalent structural elements that do not differ substantially from the literal language of the claims, they are intended to be within the scope of the claims.

Claims

1. A method for operating a renewable energy source having an inverter-based resource (IBR) system and controlled by a power converter controller, the method comprising: operating the IBR system under grid formation mode (GFM) control; receiving, with the power converter controller, a control signal derived based on a frequency droop function performed on a detected grid frequency at an upstream controller; generating, with the power converter controller, an output power actuator signal based on one of an inertial power regulator or a frequency droop function performed at the power converter controller on the detected grid frequency; as well as A first compensation is applied to the upstream controller, the first compensation reducing or eliminating variations in the control signal received by the power converter controller due to variations in the grid frequency or phase angle.

2. The method according to claim 1, wherein The IBR is a wind turbine generator, the upstream controller is a wind turbine controller, and the control signal received by the power converter controller is a power reference signal generated by the wind turbine controller.

3. The method according to claim 2, wherein: The first compensation is provided by a turbine stage power command compensation based on the detected grid frequency.

4. The method according to claim 3, wherein: The first compensation provided by the turbine stage power command compensation is also based on a generator rotor speed feedback signal.

5. The method according to claim 2, wherein: The first compensation is provided by a turbine level power or speed feedback compensation based on a wind turbine power feedback signal and the detected grid frequency.

6. The method according to claim 2, wherein: The first compensation is provided by a turbine stage power command compensation based on the detected grid frequency and a turbine stage power feedback compensation based on a wind turbine power feedback signal and the detected grid frequency.

7. The method according to claim 1, wherein The IBR is a wind turbine generator and the control signal is a power reference signal generated by the wind turbine controller, wherein the upstream controller is a plant-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.

8. The method according to claim 7, wherein: The first compensation is provided by a plant-level power command compensation based on the detected grid frequency.

9. The method according to claim 8, wherein The first compensation from the plant-level power command compensation is further based on an aggregate response estimate signal that predicts a collective response of active power of a group of the wind turbine generators in a plant to grid frequency variations.

10. The method according to claim 7, wherein: The first compensation is provided by a plant-level power feedback compensation based on a plant power feedback signal and the detected grid frequency.

11. The method according to claim 10, wherein: The first compensation from the plant-level power feedback compensation is further based on an aggregate response estimate signal that predicts a collective response of active power of a group of the wind turbine generators in a plant to grid frequency variations.

12. The method according to claim 7, wherein: The first compensation is provided by a signal derived from the detected rate of change of the grid frequency, which is applied to a plant power conditioner in the plant-level controller to freeze the plant power conditioner based on the detected rate of change of the grid frequency until a RoCoF signal is zero for a predefined time period.

13. The method according to claim 7, wherein: The first compensation is provided by one or more of: (a) a plant-level power command compensation based on the detected grid frequency; (b) a plant-level power feedback compensation based on a plant power feedback signal and the detected grid frequency; or (c) a signal derived from the rate of change of the detected grid frequency applied to a plant power conditioner in the plant-level controller.

14. A method for operating a wind turbine generator in a wind turbine plant, the wind turbine plant having a plurality of wind turbines connected to a power grid, the wind turbines having a wind turbine controller in communication with a plant-level controller, the wind turbine generator having a power converter controller, the method comprising: operating the wind turbine generator under grid forming mode (GFM) control; receiving, with the power converter controller, a first control signal derived by the wind turbine controller based on a frequency droop function performed on a detected grid frequency; receiving, with the wind turbine controller, a second control signal derived by the plant-level controller based in part on a frequency droop function performed at the plant-level controller on the detected grid frequency; generating, with the power converter controller, an output power actuator signal based in part on a frequency droop function or an inertial power regulator performed at the power converter controller on the detected grid frequency; as well as A first compensation is applied to the wind turbine controller and a second compensation is applied to the plant-level controller, wherein the first compensation and the second compensation reduce or eliminate variations in the control signal received by the power converter controller due to variations in the grid frequency.

15. The method according to claim 14, wherein The first compensation is provided by one or both of a turbine stage power command compensation based on the detected grid frequency or a turbine stage power feedback compensation based on a wind turbine power feedback signal and the detected grid frequency.

16. The method according to claim 14, wherein The second compensation includes one or more of the following: (a) a plant-level power command compensation based on the detected grid frequency; (b) a plant-level power feedback compensation based on a plant power feedback signal and the detected grid frequency; or (c) a signal derived from the rate of change of the detected grid frequency applied to a plant power conditioner in the plant-level controller.

17. The method according to claim 16, wherein The plant-level power command compensation is further based on an aggregate response estimate signal that predicts a collective response of active power of a group of the wind turbine generators in a plant to grid frequency variations.

18. The method according to claim 16, wherein The plant-level power feedback compensation is further based on an aggregate response estimate signal that predicts a collective response of active power of a group of the wind turbine generators in a plant to grid frequency variations.

19. A wind turbine comprising: a wind turbine generator configured as an inverter-based resource (IBR) renewable energy source connected to a power grid and controlled by a power converter controller; and Wherein the wind turbine generator is configured to operate according to the method of claim 1 .

20. A wind turbine plant comprising: multiple wind turbines; Each of the wind turbines includes a wind turbine generator configured as an inverter-based resource (IBR) renewable energy source connected to a power grid and controlled by a power converter controller; and Wherein the wind turbine generator is configured to operate according to the method of claim 1 .

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