System and method for providing grid forming control for doubly-fed wind turbine generators

Abstract

A method for providing grid formation control of a doubly-fed wind turbine generator connected to a power grid includes receiving at least one control signal associated with a desired total power output or total current output of the doubly-fed wind turbine generator. The method also includes determining a contribution of at least one of power or current from a line-side converter to the desired total power output or total current output, respectively, of the doubly-fed wind turbine generator. The method further includes determining a control command for a stator of the doubly-fed wind turbine generator based on the contribution of the at least one of power or current from the line-side converter and the at least one control signal. In addition, the method includes adjusting the at least one of power or current in the stator of the doubly-fed wind turbine generator using the control command.

Description

Technical Field

[0001] This disclosure generally relates to doubly-fed wind turbine generators, and more specifically to systems and methods for providing grid formation control of doubly-fed wind turbine generators using virtual impedance. Background Technology

[0002] Wind power is considered one of the cleanest and most environmentally friendly energy sources available today, and wind turbines have received increasing attention in this area. A modern wind turbine typically consists of a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture the kinetic energy of the wind using the known airfoil principle. For example, rotor blades typically have an airfoil cross-sectional profile such that during operation, airflow across the blades creates a pressure difference between the sides. Therefore, lift, directed from the pressure side towards the suction side, acts on the blades. This lift generates torque on the main rotor shaft, which is typically geared to the generator to produce electricity.

[0003] Wind turbines can be classified into two types: constant-speed turbines and variable-speed turbines. Conventionally, variable-speed wind turbines are controlled as current sources connected to the power grid. In other words, variable-speed wind turbines rely on the grid frequency detected by a phase-locked loop (PLL) as a reference and inject a specified amount of current into the grid. Conventional current source control of wind turbines is based on the assumption that the grid voltage waveform is a fundamental voltage waveform with a fixed frequency and amplitude, and that wind power penetration in the grid is low enough not to interfere with 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, its penetration in some grids has increased to the point where wind turbine generators have a significant impact on grid voltage and frequency. When a wind turbine is located in a weak grid, 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 the wind turbine current control.

[0004] Therefore, many existing asynchronous generators (such as doubly-fed wind turbine generators) operate in "grid-following" mode. Grid-following equipment utilizes a fast current regulation loop to control the active and reactive power exchanged with the grid. More specifically, Figure 1The diagram illustrates the basic components of the main circuit and converter control structure of a grid-following doubly-fed induction generator (DFIG) wind turbine. As shown, the active power reference for the converter is developed by the energy source regulator (e.g., the turbine control section of the wind turbine). This is passed as a torque reference, representing the smaller of the maximum power available from the energy source at that moment or a reduction command from a higher-level grid controller. The converter control unit then determines the current reference for the active component of the current to achieve the desired torque. Therefore, the DFIG wind turbine includes functions that manage voltage and reactive power in a manner that results in commands for the reactive component of the current. A wide-bandwidth current regulator then develops commands for the converter to apply voltage to the system, ensuring that the actual current closely follows the commands.

[0005] Alternatively, grid forming (GFM) is based on the inverter's resource-integrated transformer (IBR) acting as a voltage source after impedance and providing voltage source characteristics, where the angle and magnitude of the voltage are controlled to achieve the regulation functions required by the grid. Specifically, the impedance of the GFM IBR is typically determined by the system hardware, such as the impedance of reactors, transformers, or rotating electrical machines. In this configuration, current flows according to the grid's demand, while the converter helps establish voltage and frequency for the grid. This characteristic is comparable to a conventional turbine-based generator that drives a synchronous motor. Therefore, a grid forming source must include the following basic functions: (1) support grid voltage and frequency for any current (both active and reactive) within the rated value of the equipment; (2) prevent operation beyond the equipment's voltage or current capacity by allowing changes in grid voltage or frequency rather than disconnecting the equipment (disconnection is only allowed when the voltage or frequency exceeds the boundary established by the grid entity); (3) remain stable for any grid configuration or load characteristics, including supplying isolated loads or connecting to other grid forming sources, and switching between these configurations; (4) share the total load of the grid among other grid forming sources connected to the grid; (5) traverse grid disturbances (both large and small disturbances); and (6) meet requirements (1)-(5) without requiring rapid communication with other control systems present in the grid or externally created logic signals related to changes in grid configuration.

[0006] The basic control structure for achieving the aforementioned grid-forming objectives was developed and field-proven for battery systems in the early 1990s (see, for example, U.S. Patent No. 5,798,633, entitled "Battery Energy Storage Power Conditioning System"). Applications to full-power converter wind turbines and solar generators are disclosed in U.S. Patent Nos. 7,804,184, entitled "System and Method for Control of a Grid Connected Power Generating System," and 9,270,194, entitled "Controller for controlling a powerconverter." 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 Doubly-Feb Wind Turbine Generator."

[0007] In particular, such as Figure 2 As shown, the grid-forming voltage source is implemented on the stator voltage for implementing grid-forming control for a doubly-fed wind turbine generator using a stator voltage regulator. More specifically, as shown, the stator voltage regulator 50 is configured to receive higher-level commands (e.g., E) for the amplitude of the stator voltage. I ) and higher-level commands (e.g., δ) for the stator voltage angle relative to the phase-locked loop angle. IT Furthermore, as shown in the figure, the stator voltage regulator 50 can then convert (multiple) voltage commands into stator voltage commands (e.g., VS_Cmd_xy), as shown at 52. The stator voltage regulator 50 can then determine a magnetizing current feedforward signal (e.g., IM_FF_xy) based on the stator voltage commands and the magnetizing admittance (e.g., jBmag 54), the magnetizing admittance corresponding to the magnetizing susceptance. Accordingly, the magnetizing current feedforward signal is configured to facilitate a rapid response of the stator voltage to the stator voltage commands.

[0008] Furthermore, as shown, the stator voltage regulator 50 can also receive a stator voltage feedback signal (e.g., VS_Fbk_xy) and determine the difference between the stator voltage feedback signal and the stator voltage command, as shown at 62. Therefore, in this embodiment, as shown, the stator voltage regulator 50 can also determine a magnetization current correction signal (e.g., IM_Corr_xy) via a proportional-integral regulator 232. Thus, as shown at 56, the stator voltage regulator 50 can then add a magnetization current feedforward signal (e.g., IM_FF_xy) to the magnetization current correction signal (IM_Corr_xy) from the power regulator to determine the magnetization current command (e.g., IM_Cmd_xy).

[0009] Furthermore, as shown at 58, the stator voltage regulator 50 can determine (e.g., IR_Cmd_xy) rotor current commands based on the magnetizing current command (e.g., IM_Cmd_xy) and the stator current feedback signal (e.g., IS_Fbk_xy). Therefore, in an embodiment, the measured stator current signal can be fed into the rotor current command, as shown at 58, to substantially decouple the stator response stator voltage from one or more grid characteristics. More specifically, in a particular embodiment, as shown, the stator voltage regulator 50 can determine (e.g., (e.g., (e.g., ( (magnetizing current) command)) rotor current commands by adding the magnetizing current command to the measured stator current feedback signal. Furthermore, as shown, the limiter 60 can, as appropriate, limit the rotor current commands to comply with (e.g., ...

[0010] Therefore, it would be advantageous to configure systems and methods such that the effective impedance can be set independently of the physical characteristics of the equipment. Thus, this disclosure relates to a system and method for creating a configurable virtual impedance in a GFM doubly-fed wind turbine generator to increase flexibility in the dynamics of the tuned system. Summary of the Invention

[0011] Technical Solution 1. A method for providing grid formation control for a doubly-fed wind turbine generator connected to a power grid, the doubly-fed wind turbine generator having a line-side converter connected via a DC link to a rotor-side converter, the method comprising: Receive at least one control signal associated with the desired total power output or total current output of the doubly fed wind turbine generator; Determine the contribution of at least one of the power or current from the line-side converter to the desired total power output or total current output of the doubly-fed wind turbine generator, respectively. Control commands for the stator of the doubly-fed wind turbine generator are determined based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal; and The control commands are used to adjust at least one of the power or current in the stator of the doubly fed wind turbine generator.

[0012] Technical Solution 2. The method according to Technical Solution 1, wherein at least one control signal associated with the desired total power output or total current output of the doubly fed wind turbine generator includes at least one of phase angle or total power command.

[0013] Technical Solution 3. The method according to Technical Solution 2, wherein determining the control command for the stator of the doubly-fed wind turbine generator based on the contribution of at least one of the power currents from the line-side converter and the at least one control signal further includes: Use the total power command to adjust the total power output to generate an angle command; and The angle command is compensated to generate control commands for the stator of the doubly-fed wind turbine generator.

[0014] Technical Solution 4. The method according to Technical Solution 3, wherein compensating the angle command to generate control commands for the stator of the doubly-fed wind turbine generator further includes: The line-side converter power is estimated based on the total power command and the slip of the doubly fed wind turbine generator; The compensation angle is estimated based on the power of the line-side converter and the internal impedance value of the doubly-fed wind turbine generator; and The compensation angle is used to compensate the angle command to generate control commands for the stator of the doubly-fed wind turbine generator.

[0015] Technical Solution 5. The method according to Technical Solution 4, wherein estimating the compensation angle based on the power of the line-side converter and the internal impedance value of the doubly-fed wind turbine generator further includes: Receive the electrical frequency and rotor speed of the doubly fed wind turbine generator; The slip of the doubly-fed wind turbine generator is determined based on the electrical frequency and the rotor speed. The slip ratio is used to determine the ratio of stator power to total power of the doubly-fed wind turbine generator; and The compensation angle is calculated based on the ratio, the internal impedance value, and the total power command.

[0016] Technical Solution 6. The method according to Technical Solution 5, wherein the internal impedance value of the doubly fed wind turbine generator includes an internal virtual impedance value and an internal physical impedance value.

[0017] Technical Solution 7. The method according to Technical Solution 2, wherein determining the control command for the stator of the doubly-fed wind turbine generator based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal further includes: Receive a control signal indicating the total power command; At the input of the power regulator of the doubly fed wind turbine generator, the total power command is compensated by the line-side converter power to generate a stator power control command; The stator power control command is used to adjust the stator power of the doubly-fed wind turbine generator.

[0018] Technical Solution 8. The method according to Technical Solution 4, wherein the internal impedance value includes the internal virtual impedance value at the node inside the doubly fed wind turbine generator.

[0019] Technical Solution 9. The method according to Technical Solution 8 further includes using a current feedback signal to determine the voltage deviation across the internal virtual impedance value of the doubly fed wind turbine generator.

[0020] Technical Solution 10. The method according to Technical Solution 9, wherein using the control command to adjust at least one of the power or current in the stator of the doubly-fed wind turbine generator further includes: Determine the difference between the voltage deviation and the internal voltage command to obtain the magnetization voltage command; The feedforward component is calculated using the magnetization voltage command; The magnetization current command is determined using the feedforward and fine-tuning components; and The magnetizing current command and at least one current feedback signal are used to calculate one or more rotor current commands for the doubly-fed wind turbine generator.

[0021] Technical Solution 11. A system for providing grid formation control for a doubly-fed wind turbine generator connected to a power grid, the doubly-fed wind turbine generator having a line-side converter connected via a DC link to a rotor-side converter, the system comprising: A controller includes at least one processor configured to perform a plurality of operations, the plurality of operations including: Receive at least one control signal associated with the desired total power output or total current output of the doubly fed wind turbine generator; Determine the contribution of at least one of the power or current from the line-side converter to the desired total power output or total current output of the doubly-fed wind turbine generator, respectively. Control commands for the stator of the doubly-fed wind turbine generator are determined based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal; and The control commands are used to adjust at least one of the power or current in the stator of the doubly fed wind turbine generator.

[0022] Technical Solution 12. The system according to Technical Solution 11, wherein the at least one control signal associated with the desired total power output or total current output of the doubly fed wind turbine generator includes at least one of phase angle or total power command.

[0023] Technical Solution 13. The system according to Technical Solution 12, wherein determining the control command for the stator of the doubly-fed wind turbine generator based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal further includes: Use the total power command to adjust the total power output to generate an angle command; and The angle command is compensated to generate control commands for the stator of the doubly-fed wind turbine generator.

[0024] Technical Solution 14. The system according to Technical Solution 13, wherein compensating the angle command to generate control commands for the stator of the doubly-fed wind turbine generator further includes: The line-side converter power is estimated based on the total power command and the slip of the doubly fed wind turbine generator; The compensation angle is estimated based on the power of the line-side converter and the internal impedance value of the doubly-fed wind turbine generator; and The compensation angle is used to compensate the angle command to generate control commands for the stator of the doubly-fed wind turbine generator.

[0025] Technical Solution 15. The system according to Technical Solution 14, wherein estimating the compensation angle based on the power of the line-side converter and the internal impedance value of the doubly-fed wind turbine generator further includes: Receive the electrical frequency and rotor speed of the doubly fed wind turbine generator; The slip of the doubly-fed wind turbine generator is determined based on the electrical frequency and the rotor speed. The slip ratio is used to determine the ratio of stator power to total power of the doubly-fed wind turbine generator; and The compensation angle is calculated based on the ratio, the internal impedance value, and the total power command.

[0026] Technical Solution 16. The system according to Technical Solution 15, wherein the internal impedance value of the doubly fed wind turbine generator includes an internal virtual impedance value and an internal physical impedance value.

[0027] Technical Solution 17. The system according to Technical Solution 15, wherein determining the control command for the stator of the doubly-fed wind turbine generator based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal further includes: Receive a control signal indicating the total power command; At the input of the power regulator of the doubly fed wind turbine generator, the total power command is compensated by the line-side converter power to generate a stator power control command; The stator power control command is used to adjust the stator power of the doubly-fed wind turbine generator.

[0028] Technical Solution 18. The system according to Technical Solution 14, wherein the internal impedance value includes an internal virtual impedance value at a node inside the doubly fed wind turbine generator.

[0029] Technical Solution 19. The system according to Technical Solution 18 further includes using a current feedback signal to determine the voltage deviation across the internal virtual impedance value of the doubly fed wind turbine generator.

[0030] Technical Solution 20. The system according to Technical Solution 19, wherein using the control command to adjust at least one of the power or current in the stator of the doubly-fed wind turbine generator further includes: Determine the difference between the voltage deviation and the at least one virtual impedance value to obtain the magnetization voltage command; The feedforward component is calculated using the magnetization voltage command; The magnetization current command is determined using the feedforward and fine-tuning components; and The magnetizing current command and at least one current feedback signal are used to calculate one or more rotor current commands for the doubly-fed wind turbine generator.

[0031] Aspects and advantages of the invention will be set forth in part in the description which follows, or may be apparent from the description, or may be learned by practice of the invention.

[0032] In one aspect, this disclosure relates to a method for providing grid formation control for a doubly-fed induction generator (DFIG) connected to a power grid. The DFIG has a line-side converter connected via a DC link to a rotor-side converter. The method includes receiving at least one control signal associated with a desired total power output or total current output of the DFIG. The method further includes determining the contribution of at least one of the power or current from the line-side converter to the desired total power output or total current output of the DFIG. The method further includes determining a control command for the stator of the DFIG based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal. Furthermore, the method includes using the control command to regulate at least one of the power or current in the stator of the DFIG.

[0033] In an embodiment, the control signals(s) associated with the desired total power output or total current output of the doubly fed wind turbine generator may include at least one of phase angle or total power command.

[0034] In another embodiment, determining the control command for the stator of the doubly-fed wind turbine generator based on the contribution of at least one of the power or current from the line-side converter and at least one control signal may include: using a total power command to adjust the total power output to generate an angle command; and compensating the angle command to generate the control command for the stator of the doubly-fed wind turbine generator.

[0035] In another embodiment, the compensation angle command to generate control commands for the stator of the doubly-fed wind turbine generator may include: estimating the line-side converter power based on the total power command and the slip of the doubly-fed wind turbine generator; estimating the compensation angle based on the line-side converter power and the internal impedance value of the doubly-fed wind turbine generator; and using the compensation angle to compensate the angle command to generate control commands for the stator of the doubly-fed wind turbine generator.

[0036] In another embodiment, estimating the compensation angle based on the line-side converter power and the internal impedance value of the doubly-fed wind turbine generator may include: receiving the electrical frequency and rotor speed of the doubly-fed wind turbine generator; determining the slip of the doubly-fed wind turbine generator based on the electrical frequency and rotor speed; using the slip to determine the ratio of the stator power to the total power of the doubly-fed wind turbine generator; and calculating the compensation angle based on the ratio, the internal impedance value, and the total power command.

[0037] In several embodiments, the internal impedance value of a doubly-fed wind turbine generator may include an internal virtual impedance value and an internal physical impedance value.

[0038] In a particular embodiment, determining a control command for the stator of a doubly-fed wind turbine generator based on the contribution of at least one of the power or current from the line-side converter and at least one control signal may include: receiving a control signal indicating a total power command; compensating the total power command with the power from the line-side converter at the input of the power regulator of the doubly-fed wind turbine generator to generate a stator power control command; and using the stator power control command to regulate the stator power of the doubly-fed wind turbine generator.

[0039] In yet another embodiment, the internal impedance value may include an internal virtual impedance value at a node inside the doubly-fed wind turbine generator. Therefore, in such an embodiment, the method may further include using a current feedback signal to determine the voltage deviation across the internal virtual impedance value of the doubly-fed wind turbine generator.

[0040] In an embodiment, using control commands to adjust at least one of the power or current in the stator of a doubly-fed wind turbine generator may include: determining the difference between a voltage deviation and an internal voltage command to obtain a magnetizing voltage command; calculating a feedforward component using the magnetizing voltage command; determining a magnetizing current command using the feedforward component and a trim (or adjustment, i.e., trim) component; and calculating one or more rotor current commands for the doubly-fed wind turbine generator using the magnetizing current command and at least one current feedback signal.

[0041] In another aspect, this disclosure relates to a system for providing grid formation control for a doubly-fed induction generator (DFIG) connected to a power grid. The DFIG has a line-side converter connected via a DC link to a rotor-side converter. The system includes a controller having at least one processor configured to perform multiple operations, including but not limited to: receiving at least one control signal associated with a desired total power output or total current output of the DFIG; determining the contribution of at least one of the power or current from the line-side converter to the desired total power output or total current output of the DFIG; determining a control command for the stator of the DFIG based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal; and using the control command to regulate at least one of the power or current in the stator of the DFIG. It should be understood that the system may also include any of the additional features described herein.

[0042] These and other features, aspects, and advantages of the invention will become more readily understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. Attached Figure Description

[0043] The complete and feasible disclosure of the invention, including its best mode, is set forth in the description with reference to the accompanying drawings, which are intended for those skilled in the art. Figure 1 A single-line diagram of a doubly fed wind turbine generator according to conventional construction is shown, which has a converter control structure for grid following applications. Figure 2 A schematic diagram of one embodiment of a grid-forming stator voltage regulator for a doubly-fed wind turbine generator according to the present disclosure is shown. Figure 3 A perspective view of one embodiment of a wind turbine according to the present disclosure is shown; Figure 4 A simplified interior view of a cabin according to an embodiment of the present disclosure is shown; Figure 5 It shows what is suitable for use with Figure 3 A schematic diagram of one embodiment of a wind turbine electric power system used in conjunction with the wind turbines shown in the diagram; Figure 6 A simplified equivalent circuit of a wind turbine electric power system according to the present disclosure is shown; Figure 7 A schematic diagram of one embodiment of a wind farm having multiple wind turbines according to the present disclosure is shown; Figure 8 A block diagram of one embodiment of a controller according to the present disclosure is shown; Figure 9 A single-line diagram of a doubly-fed wind turbine generator with converter control for grid-forming applications is shown according to this disclosure; Figure 10 A flowchart is shown as an embodiment of a method for providing grid formation control for a doubly-fed wind turbine generator connected to a power grid, according to the present disclosure; Figure 11 An equivalent circuit for a doubly fed wind turbine generator with virtual impedance, according to the present disclosure, is shown. Figure 12 A schematic diagram of an embodiment of control logic for implementing a doubly-fed wind turbine generator with the virtual impedance value used is shown; and Figure 13 A schematic diagram of one embodiment of a line-side converter voltage compensation module according to the present disclosure is shown. Detailed Implementation

[0044] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation, not limitation, of the invention. Indeed, it will be apparent to those skilled in the art that various modifications and variations may be made to the invention without departing from the scope or spirit thereof. For example, a feature shown or described in part as one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, the invention is intended to cover such modifications and variations and their equivalents as fall within the scope of the appended claims.

[0045] In general, this disclosure relates to systems and methods for providing grid formation control for a doubly-fed induction generator (DFIG) wind turbine generator using virtual impedance. In some embodiments, the systems and methods of this disclosure involve synthesizing a voltage source after the impedance characteristics, wherein the voltage source is synthesized after the generator's inherent virtual impedance. Therefore, the systems and methods of this disclosure relate to compensating for the voltage command of grid formation control to account for the contribution of the line-side converter to the output power. Although the hardware architecture of a DFIG wind turbine generator is more complex (e.g., paralleling the line-side converter and the generator), this approach achieves an effective voltage source after the impedance characteristics.

[0046] Now refer to the attached diagram, Figure 3 A perspective view of one embodiment of a wind turbine 10 according to the present disclosure is shown. As shown, the wind turbine 10 generally includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on the tower 12, and a rotor 18 coupled to the nacelle 16. The rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to 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 fewer than three rotor blades 22. Each rotor blade 22 may be spaced apart around the hub 20 to facilitate rotation of the rotor 18 so that kinetic energy can be converted from wind energy into usable mechanical energy, and subsequently into electrical energy. For example, the hub 20 may be rotatably coupled to a generator 24 positioned within the nacelle 16. Figure 4 This allows for the generation of electrical energy.

[0047] The wind turbine 10 may also include a wind turbine controller 26 centralized within the nacelle 16. However, in other embodiments, the controller 26 may be located within any other component of the wind turbine 10 or at a location outside the wind turbine 10. Furthermore, the controller 26 may be communicatively coupled to any number of components of the wind turbine 10 to control the operation of such components and / or perform corrective or control actions. Accordingly, the controller 26 may include a computer or other suitable processing unit. Therefore, in several embodiments, the controller 26 may include suitable computer-readable instructions that, when implemented, configure the controller 26 to perform various functions, such as receiving, sending, and / or executing wind turbine control signals. Thus, the controller 26 may be generally configured to control various operating modes of the wind turbine 10 (e.g., start-up or shutdown sequences), degrading or upgrading of the wind turbine, and / or various components of the wind turbine 10.

[0048] Now for reference Figure 4 , showed Figure 1 The diagram shows a simplified internal view of one embodiment of the nacelle 16 of the wind turbine 10. As shown, a generator 24 may be housed within the nacelle 16 and supported on top of a base plate 46. Generally, the generator 24 may be coupled to a rotor 18 to generate 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 a hub 20 for rotation therewith. The rotor shaft 34 may then be rotatably coupled to a generator shaft 36 of the generator 24 via a gearbox 38. As generally understood, in response to 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 thus the generator 24.

[0049] The wind turbine 10 may also include one or more pitch drive mechanisms 32 communicatively coupled to the wind turbine controller 26, wherein each(s) pitch control mechanism(s) 32 is configured to rotate the pitch bearing 40, and thus to rotate the respective rotor blade(s) 22 about their respective pitch axis 28. Furthermore, as shown, the wind turbine 10 may include one or more yaw drive mechanisms 42 configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging the yaw bearing 44 of the wind turbine 10 disposed between the nacelle 16 and the tower 12 of the wind turbine 10).

[0050] In addition, the wind turbine 10 may include one or more sensors 66, 68 for monitoring various wind conditions of the wind turbine 10. For example, the wind direction 30, wind speed, or any other suitable wind conditions near the wind turbine 10 may be measured by using a suitable weather sensor 66. Suitable weather sensors may include, for example, light detection and ranging (“LIDAR”) devices, sound detection and ranging (“SODAR”) devices, anemometers, wind vanes, barometers, radar devices (such as Doppler radar devices), or any other sensing devices now known in the art or developed hereafter that can provide wind direction information. Additional sensors 68 may also be used to measure additional operating parameters of the wind turbine 10, such as voltage, current, vibration, etc., as described herein.

[0051] Now for reference Figure 5 and Figure 6 Schematic diagrams of certain embodiments of a wind turbine power system 100 are shown according to various aspects of this disclosure. In particular, Figure 5 It shows what is suitable for use with Figure 3 A schematic diagram of one embodiment of a wind turbine electric power system 100 used in conjunction with the wind turbines shown in the diagram, and Figure 6 A simplified equivalent circuit of a wind turbine electric power system 100 is shown. Although this disclosure will be generally referenced herein... Figure 5 and Figure 6 The wind turbine electric power system 100 shown herein is described, but those skilled in the art who use the disclosure provided herein should understand that aspects of this disclosure can also be applied to other power generation systems, and as mentioned above, the invention is not limited to wind turbine systems.

[0052] exist Figure 5 In the embodiments and as mentioned, the rotor 18 of the wind turbine 10 ( Figure 3 Optionally, it can be connected to gearbox 38, which in turn is connected to generator 102, which can be a doubly-fed induction generator (DFIG) as described herein. Figure 5 and Figure 6 As shown, DFIG 102 can be connected to stator bus 104. Furthermore, as... Figure 5 and Figure 6As shown, power converter 106 can be connected to DFIG 102 via rotor bus 108 and to stator bus 104 via line-side bus 110. Accordingly, stator bus 104 can provide multiphase output power (e.g., three-phase power) from the stator of DFIG 102, and rotor bus 108 can provide multiphase output power (e.g., three-phase power) from the rotor of DFIG 102. Power converter 106 may also include rotor-side converter (RSC) 112 and line-side converter (LSC) 114. DFIG 102 is connected to RSC 112 via rotor bus 108. Additionally, RSC 112 is connected to LSC 114 via DC link 116, with DC link capacitor 118 traversing the DC link. LSC 114 is then connected to line-side bus 110. Power converter 106 may also include... Figure 6 The dynamic brake 105 shown is illustrated.

[0053] RSC 112 and LSC 114 can be configured for normal operating mode in a three-phase pulse width modulation (PWM) arrangement using one or more switching devices, such as insulated gate bipolar transistor (IGBT) switching elements. Furthermore, as... Figure 5 As shown, power converter 106 can be coupled to converter controller 120 to control the operation of RSC 112 and LSC 114, as described herein. It should be noted that converter controller 120 can be configured as an interface between power converter 106 and turbine controller 26, and can include any number of control devices.

[0054] In a typical configuration, various line contactors and circuit breakers may also be included, including, for example, a grid circuit breaker 122, to isolate various components as necessary for normal operation of DFIG 102 during connection to and disconnection from loads such as grid 124. For example, a system circuit breaker 126 may connect system bus 128 to transformer 130, which may be connected to grid 124 via grid circuit breaker 122. In alternative embodiments, fuses may replace some or all of the circuit breakers.

[0055] In operation, AC power generated at DFIG 102 by rotating rotor 18 is supplied to grid 124 via a dual path defined by stator bus 104 and rotor bus 108. On rotor bus side 108, sinusoidal multiphase (e.g., three-phase) AC power is supplied to power converter 106. RSC 112 converts the AC power supplied from rotor bus 108 into direct current (DC) power and supplies the DC power to DC link 116. As generally understood, switching elements (e.g., IGBTs) used in the bridge circuit of RSC 112 can be modulated to convert the AC power supplied from rotor bus 108 into DC power suitable for DC link 116.

[0056] Furthermore, LSC 114 converts the DC power on DC link 116 into AC output power suitable for the power grid 124. Specifically, the switching elements (e.g., IGBTs) used in the bridge circuit of LSC 114 can be modulated to convert the DC power on DC link 116 into AC power on the line-side bus 110. The AC power from power converter 106 can be combined with the power from the stator of DFIG 102 to provide multiphase power (e.g., three-phase power) with a frequency (e.g., 50Hz or 60Hz) substantially maintained at the frequency of the power grid 124.

[0057] In addition, such as Figure 5 As shown, various circuit breakers and switches, such as grid circuit breaker 122, system circuit breaker 126, stator synchronizing switch 132, converter circuit 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 excessive current may damage components of the wind turbine power system 100 or for other operational considerations. Additional protective components may also be included in the wind turbine power system 100.

[0058] Furthermore, the power converter 106 may receive control signals from, for example, a local control system 176 via the converter controller 120. These control signals may be based, in particular, on sensed states or operating characteristics of the wind turbine power system 100. Typically, 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 an appropriate and balanced multiphase (e.g., three-phase) power supply. Other feedback from other sensors may also be used by the controllers(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.

[0059] The power converter 106 also compensates for or regulates the frequency of the three-phase power from the rotor to accommodate variations in wind speed, for example, at the hub 20 and rotor blades 22. Thus, the mechanical and electrical rotor frequencies are decoupled, and electrical stator and rotor frequency matching is facilitated substantially independently of the mechanical rotor speed.

[0060] In some states, the bidirectional nature of power converter 106, and specifically the bidirectional nature of LSC 114 and RSC 112, facilitates the feedback of at least some of the generated electrical power to the generator rotor. More specifically, electrical power can be transferred from stator bus 104 to line-side bus 110, and subsequently via line contactor 136 to power converter 106 (specifically LSC 114, which acts as a rectifier and rectifies sinusoidal three-phase AC power into DC power). The DC power is then transferred to DC link 116. Capacitor 118 helps mitigate DC link voltage amplitude variations by facilitating the reduction of DC ripple sometimes associated with three-phase AC rectification.

[0061] The DC power is then transmitted to RSC 112, which converts the DC power into three-phase sinusoidal AC power by adjusting the voltage, current, and frequency. This conversion is controlled and monitored via converter controller 120. The converted AC power is then transmitted from RSC 112 to the generator rotor via rotor bus 108. In this way, reactive power control of the generator is facilitated by controlling the rotor current and voltage.

[0062] Special reference Figure 6 As mentioned, a single-line circuit diagram of the wind turbine power system 100 is shown. Specifically, as shown, the power (P) generated by the wind turbine power system 100 is... T ) is from the generator stator (P S ) and LSC 114 (P L The sum of the powers of ) is given by the following equation (1): P T = P S + P L Equation (1) In addition, from LSC 114(P L The power can be obtained by assuming it comes from the rotor (P) of DFIG 102. R All the power of ) is transferred to LSC 114 to approximate it, as given by the following equation (2): P L ≈ -P R = −Slip * Ps Equation (2) The slip ratio is defined by the relationship provided in equation (3) below: Slip = ω elec −ω rot / ω elec Equation (3) Where, ω elec It is the electrical frequency of the wind turbine power system 100, and ω rot It is the rotor speed of rotor 18 of wind turbine power system 100.

[0063] Therefore, in the embodiment, by combining the aforementioned relationships, the stator power (P) S ) and total power (P) T The ratio of ) can be expressed by the following equation (4): P S / P t = 1 / (1−slip) Equation (4) Still in another Figure 6 The relationships shown, such as voltage (V), current (I), and impedance (X), will be described in more detail in this paper.

[0064] Now for reference Figure 7 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 aforementioned wind turbine 10) and a total farm-level controller 156. For example, as shown in the illustrated embodiment, the wind farm 150 includes twelve wind turbines, including wind turbine 10. However, in other embodiments, the wind farm 150 may include any other number of wind turbines, such as fewer than twelve or more than twelve wind turbines. In one embodiment, the turbine controllers of the plurality of wind turbines 152 are communicatively connected to the farm-level controller 156, for example, via a wired connection, such as by connecting turbine controller 26 via a suitable communication link 154 (e.g., a suitable cable). Alternatively, the turbine controllers may be communicatively connected to the farm-level controller 156 via a wireless connection, such as by using any suitable wireless communication protocol known in the art. In another embodiment, the field-level controller 156 is configured to send and receive control signals to and from various wind turbines 152, such as allocating active and / or reactive power demands across wind turbines 52 of the wind farm 150.

[0065] Now for reference Figure 8This diagram illustrates a block diagram of one embodiment of a controller (such as any of the turbine controller 26, converter controller 120, and / or field-level controller 156 described herein) according to exemplary aspects of this disclosure. As shown, the controller may include one or more processors 158, a computer or other suitable processing unit, and associated memory devices(s) 160, which may include suitable computer-readable instructions that, when implemented, configure the controller to perform various functions, such as receiving, sending, and / or executing wind turbine control signals (e.g., performing the methods, steps, calculations, etc., disclosed herein).

[0066] As used herein, the term "processor" refers not only to the integrated circuit known in the art as being contained in a computer, but also to controllers, microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs), and other programmable circuits. Additionally, the memory device(s) 60 may generally include (but are not limited to) memory elements, including but not limited to computer-readable media (e.g., random access memory (RAM)), computer-readable non-volatile media (e.g., flash memory), floppy disks, compact disc read-only memory (CD-ROM), magneto-optical discs (MOD), digital versatile discs (DVDs), and / or other suitable memory elements.

[0067] Multiple such memory devices 160 may be generally configured to store suitable computer-readable instructions that, when implemented by the processors 158, configure the controller to perform the various functions described herein. Additionally, the controller may include a communication interface 162 to facilitate 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) to allow signals transmitted from sensors 66, 68 to be converted into signals that can be understood and processed by the processors 58.

[0068] Now for reference Figure 9 This illustration shows a schematic diagram of one embodiment of a system 200 for providing grid formation control for a doubly-fed generator for a wind turbine, according to the present disclosure. More specifically, as shown, system 200 may include the features described herein. Figure 5 Many of the same features are present, wherein components with the same reference numerals denote the same components. Furthermore, as shown, system 200 may include a control structure for controlling the line-side converter, which is similar to... Figure 5 The control structure shown is shown below.

[0069] Furthermore, as shown in the figure, the LSC control structure may include a DC regulator 212 and a line current regulator 214. The DC regulator 212 is configured to generate a line-side current command for the line current regulator 214. The line current regulator 214 then generates a line-side voltage command for the modulator 218. The modulator 218 also receives an output (e.g., a phase-locked loop angle) from a phase-locked loop 216 to generate one or more gating pulses for the LSC 114. The phase-locked loop 216 typically uses a voltage feedback signal to generate its output.

[0070] Furthermore, as shown in the figure, system 200 may also include a control structure for controlling RSC112 using grid formation characteristics. Specifically, as... Figure 9 As shown, system 200 may include a stator voltage regulator 206 for providing this grid formation characteristic. Additionally, as shown, system 200 may include a grid voltage / VAR regulator 202, an inertial power regulator 204, a rotor current regulator 208, and a modulator 210.

[0071] In one embodiment, the grid voltage / VAR regulator 202 receives a voltage reference (e.g., VT_REF) from the field-level controller 156 and generates a stator voltage amplitude command (e.g., VS_Mag_Cmd), while the inertial power regulator receives a power reference from the turbine controller 26 and generates a stator voltage angle command (e.g., VS_Angle_Cmd). More specifically, in one embodiment, as shown, the stator voltage regulator 206 determines one or more rotor current commands (e.g., IRCmdy and IRCmdx) based on the stator voltage amplitude command, stator voltage angle command, and / or stator current feedback signal 240 of the doubly-fed generator 120. It should be understood that the stator feedback current 240 is a strong indicator of the characteristics of the externally connected power system (i.e., the power grid). Therefore, the stator feedback current 240 can be used as a feedback signal to decouple the stator voltage response to changes from the nature of the power grid. Further details relating to the stator voltage regulator 206 are explained and described in PCT / US2020 / 013787 entitled “System and Method for Providing Grid-Forming Control for a Doubly-Feb Wind Turbine Generator”, which is incorporated herein by reference in its entirety.

[0072] As mentioned, regarding grid formation control, the current changes rapidly when grid disturbances occur. Furthermore, the control action is abrupt to restore steady-state operating conditions from higher-level control commands. The amount of current change is negatively correlated with the total impedance of the circuit. However, if the current exceeds a limit, the control responds quickly to force the current within that limit. When applied to a grid composed of many other similar systems, this strong nonlinearity can lead to disordered behavior. Alternatively, if the current change is too small, the grid formation system will not contribute as much to supporting the grid as it could otherwise.

[0073] therefore, Figures 10 to 13 A system 400 and a method 300 for providing grid formation control for a doubly-fed wind turbine generator such as the DFIG 102 using at least one virtual impedance are generally described. Reference is made in particular to... Figure 10 A flowchart illustrating an embodiment of a method 300 for providing grid formation control of a DFIG 102 using at least one virtual impedance according to this disclosure is shown. It should be understood that the disclosed method 300 can be implemented using any suitable doubly-fed wind turbine generator with any suitable configuration. Furthermore, although for illustrative and discussion purposes, Figure 10 The steps are described in a specific order, but the methods discussed herein are not limited to any particular order or arrangement. Those skilled in the art will understand, using the disclosure provided herein, that the various steps of the methods disclosed herein can be omitted, rearranged, combined, and / or modified in various ways without departing from the scope of this disclosure.

[0074] As shown in (302), method 300 includes receiving at least one control signal associated with a desired total power output or total current output of DFIG 102. For example, in an embodiment, the control signal(s) associated with the desired total power output or total current output of DFIG 102 may include a phase angle or a total power command. As shown in (304), method 300 includes determining the contribution of at least one of the power or current from LSC 114 to the desired total power output or total current output of DFIG 102, respectively. As shown in (306), method 300 includes determining a control command for the stator of DFIG 102 based on the contribution of at least one of the power or current from LSC 114 and the control signal(s). As shown in (308), method 300 includes using the control command to regulate at least one of the power or current in the stator of DFIG 102.

[0075] Reference Figure 11 and Figure 12 To better understand Figure 10 Method 300. More specifically, such as Figure 11The diagram illustrates the equivalent circuit of a power grid forming DFIG 102 with virtual impedance according to this disclosure. Specifically, the components indicated hypothetically represent "virtual" components, as such components are not actual hardware of the wind turbine power system 100, but are provided or simulated using software with available resources. Furthermore, refer to… Figure 6 and Figure 11 Components with the same reference variable represent the same variable. Therefore, such as Figure 11 As shown, the equivalent circuit may include (multiple) virtual impedance values, such as the internal virtual impedance value X at the nodes inside the doubly-fed wind turbine generator 102. D And / or the external virtual impedance value X at the node outside DFIG 102 G .

[0076] Therefore, in some embodiments, two virtual impedances may be implemented, each with a specific purpose related to the active power dynamics of the system. For example, in one embodiment, the internal virtual impedance may allow tuning of the active power output of the wind turbine power system 100 in response to variations in the external network angle. In another embodiment, the external virtual impedance may allow tuning of the grid angle estimate via a phase-locked loop in response to variations in the active power output of the grid forming resources. In such embodiments, multiple degrees of freedom allow for the configuration and tuning of active power dynamics for grid forming converter control using various hardware types and various types of external networks.

[0077] As used herein, a tunable “virtual” impedance value typically refers to impedance behavior that can be simulated by the system, rather than impedance provided by a specific component, such as an inductor. Therefore, the virtual or effective impedance can be a fixed value determined by a study of the application scenario. Alternatively, the virtual impedance can be a variable, such as one determined by control logic adapted to measured grid conditions. In one embodiment, as an example, such as during a grid fault, a larger effective impedance can be used to reduce the extreme nonlinearity associated with a rapid rise to the current-limiting region. Thus, after the fault is cleared, a larger virtual impedance allows inrush currents to remain within limits. Following a grid fault, as grid voltage recovers, the virtual impedance can subsequently decrease, allowing the converter to help support the grid while operating within its linear region. Furthermore, in embodiments, a lower effective impedance can be used to improve support provided to the grid for milder events.

[0078] In addition, such as Figure 11 As shown, the voltage source used to implement this disclosure reflects the composite voltage (E) within DFIG 102. D Furthermore, in the embodiment, the internal impedance connected in series with the synthesized voltage 466 (e.g., see...) Figure 11 and Figure 13 E in D) represents the stator leakage reactance (Xs) and internal virtual impedance (Xs) of DFIG 102. X D The combination of ) is as described below in equation (5), where I S It is the stator current, and V S It is the stator voltage: V S = E D – j*(Xs + X D )* Is Equation (5) describe Figure 11 Magnetizing voltage V in a physical circuit M The electrical equation is given by the following equation (6): V M = V S + jXs* Is Equation (6) Using this physical relationship and equation (5), the voltage of the synthesized grid after the virtual impedance can be obtained by using the following equation (7) with the physical magnetization voltage V. M Related: V M = E D - j* X D * Is Equation (7) Figure 11 The voltage V in S and V T These represent the stator voltage and the terminal voltage, respectively. Additionally, X... T I represents the transformer reactance. T It is the LSC current I in DFIG 102 L and stator current I S The sum of, and X G It is an external virtual impedance.

[0079] Now for reference Figure 12 A schematic diagram of an embodiment of a system 200 for implementing a power grid formation DFIG 102 with the virtual impedance value used, according to the present disclosure, is shown. Specifically, as shown, system 200 is configured to receive one or more control signals for DFIG 102. For example, in an embodiment, such as... Figure 12 As shown, (multiple) control signals may include phase angle δ PG Or total power command E PFor example, relative to a phase-locked loop used to synthesize at impedance X TERM The subsequent voltage. More specifically, as shown below, the impedance X TERM It can be defined by the following equation (8): X TERM = X G + X D + X S + X T Equation (8) Therefore, as shown in the figure, system 400 may also include an LSC voltage compensation module 402 for determining the contribution of at least one of the power or current from LSC 114 to the desired total power output or total current output of DFIG 102, respectively. For example, in an embodiment, such as Figure 12 As shown, the LSC voltage compensation module 402 is configured to generate a composite voltage E based on a contribution from at least one of the power or current from the LSC 114 and control signals(s). D and phase angle δ DG The synthesized voltage E D and phase angle δ DG The control command 420 (ED_Cmd_xy) for the stator of DFIG 102 can be determined via block 404.

[0080] Still referencing Figure 12 The magnetization voltage command 422 (VM_Cmd_xy) can then be calculated from the control command 420 (ED_Cmd_xy) using the above equation (7). The rotor current command 428 (IR_Cmd_xy) can then be calculated from the feedforward term 424 (IM_FF_xy) based on the estimated magnetization reactance and the fine-tuning component (IM_Corr_xy) of DFIG 102, similar to the calculation of the magnetization reactance from DFIG 102. Figure 2 The method described.

[0081] Now for reference Figure 13 A schematic diagram of one embodiment of the LSC voltage compensation module 402 according to this disclosure is shown. In the illustrated example, the LSC voltage compensation module 402 assumes that LSC 114 does not inject reactive power / current. However, in alternative embodiments, the LSC voltage compensation module 402 can be modified to account for these effects by compensating for voltage amplitude rather than angle command. Additionally, the angle compensation method can be further modified to account for dynamic braking elements (e.g., Figure 6 The power loss or operation of the dynamic brake 105.

[0082] As shown in the figure Figure 12 The input voltage command for control reflects the reactance X TERM The subsequent phase angle is 448δPG Voltage command 450 E P The relevant power equation is given by the following equation (9): P T = (E P *V G / X TERM ) * sin(δ PG ) ≈ (E P *V G / X TERM ) * (δ PG Equation (9) As explained above, equation (9) considers the reactance X TERM The power flow between two connected nodes. However, in the DFIG 102 hardware architecture, not all the power flow from the system passes through X. TERM All components. Furthermore, the power flow through the system depends on the operating speed of DFIG 102; therefore, the voltage synthesized within DFIG 102 to achieve a specific power flow depends on the operating speed of DFIG 102. To compensate for this speed dependence, the LSC voltage compensation module 402 is configured to estimate the LSC compensation angle (δ) by considering only the active power flow from LSC 114. LCOMP For example, such as Figure 13 As shown, the LSC voltage compensation module 402 can also receive the electrical frequency ω of the DFIG 102. elec 442 and rotor speed ω rot 444. As shown at 452, the LSC voltage compensation module 402 can then determine the slip 454 of the DFIG 102 based on the electrical frequency 442 and the rotor speed 444. Furthermore, as shown, the LSC voltage compensation module 402 can also filter the slip 454 via one or more filters 456. Additionally, as shown in block 458, the LSC voltage compensation module 402 can determine the ratio of the stator power to the total power of the DFIG 102 (i.e., P). S P TOT Furthermore, this ratio and total power can be used to estimate the LSC power, as shown by the following equation (10): P L = -P T *( PsP TOT – 1) Equation (10) Furthermore, as shown in box 460, the LSC voltage compensation module 402 can then calculate the compensation angle δ based on the ratio, internal impedance value, and / or power reference 446 (Pref). LCOMP 462, for example, using the following equation (10): δ LCOMP ≈ -P L * (X S + X D ) / (V S E D ) = P REF * (((P S P TOT -1)(X S + X D )) / V S E D ) ≈ P T * ((P S P TOT -1)(X S + X D Equation (11) Among them, P S Indicates stator power, P REF Represents the total power reference, and X S + X D This represents the internal impedance value of DFIG 102, where X D It is the internal virtual impedance value of DFIG 102, and X S It is the internal physical impedance value. Furthermore, in such an embodiment, the LSC power is embedded in equation (11) through the relationship in equation (10).

[0083] Therefore, the LSC compensation angle δ LCOMP It is assumed that the power from LSC 114 does not flow through the generator impedance (e.g., X). S +X D Therefore, the interior angle of the generator voltage is 464° (δ). DG This is related to the angle command, as shown in equation (10) below: δ DG ≈ δ PG + δ LCOMP Equation (12) Refer again Figure 12 As shown at 406, system 400 can also use current feedback signal 430 (IS_Fbk_xy) to determine the voltage deviation across the internal virtual impedance value of DFIG 102. Therefore, as shown at 408, system 400 can determine magnetization voltage command 422 (VM_Cmd_xy) based on control command 420 (ED_Cmd_xy) and voltage deviation.

[0084] Refer again Figure 10As shown in (308), method 300 then includes determining, at least according to control command 420 (ED_Cmd_xy), a control signal for DFIG 102. More specifically, as shown in Figure 12 As shown at 410, system 400 can use magnetization voltage command 422 (VM_Cmd_xy) to calculate feedforward component 424 (IM_FF_xy). As mentioned, system 400 can then use feedforward component 424 (IM_FF_xy) and magnetization current correction signal 432 (IM_Corr_xy) (also referred to herein as fine-tuning component) to determine magnetization current command 426 (IM_Cmd_xy). In particular, as shown, fine-tuning component 432 (IM_Corr_xy) can be the output of power regulator 414 of wind turbine power system 100.

[0085] Specifically, as shown, system 400 may receive stator voltage feedback signal 436 (VS_Fbk_xy) and / or stator current feedback signal 438 (IS_Fbk_xy), which can be summed to determine magnetization voltage feedback signal 440 (VM_Fbk_xy). Therefore, in an embodiment, as shown, system 400 may determine magnetization current correction signal 432 (IM_Corr_xy) via power regulator 414. Thus, as shown at 412, system 400 may then add magnetization current feedforward signal 424 (IM_FF_xy) to magnetization current correction signal 432 (IM_Corr_xy) from power regulator 414 to determine magnetization current command 426 (IM_Cmd_xy).

[0086] Furthermore, as shown at 416, system 400 can then use magnetizing current command 426 (IM_Cmd_xy) and at least one current feedback signal 434 (IS_Fbk_xy) to calculate one or more rotor current commands 428 (IR_Cmd_xy) for DFIG 102. Additionally, as shown, system 400 may also include limiter 418 for limiting one or more rotor current commands using upper and lower limits.

[0087] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated methods. The patentability of the invention is defined by the claims and may include other examples that would occur to a person skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method for providing grid formation control for a doubly-fed wind turbine generator connected to a power grid, the doubly-fed wind turbine generator having a line-side converter connected via a DC link to a rotor-side converter, the method comprising: Receive at least one control signal associated with the desired total power output or total current output of the doubly-fed wind turbine generator, wherein the at least one control signal associated with the desired total power output or total current output of the doubly-fed wind turbine generator includes at least one of phase angle or total power command. Determine the contribution of at least one of the power or current from the line-side converter to the desired total power output or total current output of the doubly-fed wind turbine generator, respectively. Determining a control command for the stator of the doubly-fed wind turbine generator based on a contribution from at least one of the power or current from the line-side converter and the at least one control signal, further comprising: using the total power command to adjust the total power output to generate an angle command, and compensating the angle command to generate a control command for the stator of the doubly-fed wind turbine generator; and The control commands are used to adjust at least one of the power or current in the stator of the doubly fed wind turbine generator.

2. The method according to claim 1, wherein, The compensation of the angle command to generate control commands for the stator of the doubly-fed wind turbine generator further includes: The line-side converter power is estimated based on the total power command and the slip of the doubly fed wind turbine generator; The compensation angle is estimated based on the power of the line-side converter and the internal impedance value of the doubly-fed wind turbine generator; and The compensation angle is used to compensate the angle command to generate control commands for the stator of the doubly-fed wind turbine generator.

3. The method according to claim 2, wherein, Estimating the compensation angle based on the power of the line-side converter and the internal impedance of the doubly-fed wind turbine generator also includes: Receive the electrical frequency and rotor speed of the doubly fed wind turbine generator; The slip of the doubly-fed wind turbine generator is determined based on the electrical frequency and the rotor speed. The slip ratio is used to determine the ratio of stator power to total power of the doubly-fed wind turbine generator; and The compensation angle is calculated based on the ratio, the internal impedance value, and the total power command.

4. The method according to claim 3, wherein, The internal impedance value of the doubly fed wind turbine generator includes the internal virtual impedance value and the internal physical impedance value.

5. The method according to claim 1, wherein, Determining control commands for the stator of the doubly-fed wind turbine generator based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal further includes: Receive a control signal indicating the total power command; At the input of the power regulator of the doubly fed wind turbine generator, the total power command is compensated by the line-side converter power to generate a stator power control command; The stator power control command is used to adjust the stator power of the doubly-fed wind turbine generator.

6. The method according to claim 2, wherein, The internal impedance value includes the internal virtual impedance value at the nodes inside the doubly fed wind turbine generator.

7. The method of claim 6 further comprises using a current feedback signal to determine the voltage deviation across the internal virtual impedance value of the doubly fed wind turbine generator.

8. The method according to claim 7, wherein, Using the control command to adjust at least one of the power or current in the stator of the doubly-fed wind turbine generator further includes: The difference between the voltage deviation and the internal voltage command is determined to obtain the magnetization voltage command; The feedforward component is calculated using the magnetization voltage command; The magnetization current command is determined using the feedforward and fine-tuning components; and The magnetizing current command and at least one current feedback signal are used to calculate one or more rotor current commands for the doubly-fed wind turbine generator.

9. A system for providing grid formation control for a doubly-fed wind turbine generator connected to a power grid, the doubly-fed wind turbine generator having a line-side converter connected via a DC link to a rotor-side converter, the system comprising: A controller includes at least one processor configured to perform a plurality of operations, the plurality of operations including: Receive at least one control signal associated with the desired total power output or total current output of the doubly-fed wind turbine generator, wherein the at least one control signal associated with the desired total power output or total current output of the doubly-fed wind turbine generator includes at least one of phase angle or total power command; Determine the contribution of at least one of the power or current from the line-side converter to the desired total power output or total current output of the doubly-fed wind turbine generator, respectively. Determining a control command for the stator of the doubly-fed wind turbine generator based on a contribution from at least one of the power or current from the line-side converter and the at least one control signal, further comprising: using the total power command to adjust the total power output to generate an angle command, and compensating the angle command to generate a control command for the stator of the doubly-fed wind turbine generator; and The control commands are used to adjust at least one of the power or current in the stator of the doubly fed wind turbine generator.

10. The system according to claim 9, wherein, The compensation of the angle command to generate control commands for the stator of the doubly-fed wind turbine generator further includes: The line-side converter power is estimated based on the total power command and the slip of the doubly fed wind turbine generator; The compensation angle is estimated based on the power of the line-side converter and the internal impedance value of the doubly-fed wind turbine generator; and The compensation angle is used to compensate the angle command to generate control commands for the stator of the doubly-fed wind turbine generator.

11. The system according to claim 10, wherein, Estimating the compensation angle based on the power of the line-side converter and the internal impedance of the doubly-fed wind turbine generator also includes: Receive the electrical frequency and rotor speed of the doubly fed wind turbine generator; The slip of the doubly-fed wind turbine generator is determined based on the electrical frequency and the rotor speed. The slip ratio is used to determine the ratio of stator power to total power of the doubly-fed wind turbine generator; and The compensation angle is calculated based on the ratio, the internal impedance value, and the total power command.

12. The system according to claim 11, wherein, The internal impedance value of the doubly fed wind turbine generator includes the internal virtual impedance value and the internal physical impedance value.

13. The system according to claim 11, wherein, Determining control commands for the stator of the doubly-fed wind turbine generator based on the contribution of at least one of the power or current from the line-side converter and the at least one control signal further includes: Receive a control signal indicating the total power command; At the input of the power regulator of the doubly fed wind turbine generator, the total power command is compensated by the line-side converter power to generate a stator power control command; The stator power control command is used to adjust the stator power of the doubly-fed wind turbine generator.

14. The system according to claim 10, wherein, The internal impedance value includes the internal virtual impedance value at the nodes inside the doubly fed wind turbine generator.

15. The system of claim 14, further comprising using a current feedback signal to determine the voltage deviation across the internal virtual impedance value of the doubly-fed wind turbine generator.

16. The system according to claim 15, wherein, Using the control command to adjust at least one of the power or current in the stator of the doubly-fed wind turbine generator further includes: Determine the difference between the voltage deviation and the at least one virtual impedance value to obtain the magnetization voltage command; The feedforward component is calculated using the magnetization voltage command; The magnetization current command is determined using the feedforward and fine-tuning components; and The magnetizing current command and at least one current feedback signal are used to calculate one or more rotor current commands for the doubly-fed wind turbine generator.

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