Control method and apparatus for grid-forming doubly-fed wind turbine generator, generator, and medium

Abstract

The present application relates to the technical field of wind power generation, and discloses a control method and apparatus for a grid-forming doubly-fed wind turbine generator, a generator, and a medium. In embodiments of the present application, a current reference value of a grid connection point is determined on the basis of measurement parameters of the grid connection point in combination with an internal potential parameter of a grid-forming doubly-fed wind turbine generator and a virtual impedance reference value, a voltage reference value of a grid-side converter is further determined on the basis of the current reference value of the grid connection point, and the grid-side converter is modulated on the basis of the voltage reference value, thereby implementing closed-loop control of the grid-side converter, such that a difference between an output voltage value and the voltage reference value of the grid-side converter is less than a preset threshold.

Description

Control methods, devices, units and media of grid-connected doubly-fed wind turbine units

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410914802.7, filed on July 19, 2024, entitled “Control method, device, unit and medium for grid-connected doubly fed wind turbine”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of wind power generation technology, and in particular to a control method, device, unit and medium for a grid-type doubly fed wind turbine. Background Technology

[0004] For the power grid, safety is paramount; maintaining grid stability and preventing grid disconnection incidents are crucial. Due to the fluctuating and intermittent nature of renewable energy sources, renewable energy units are generally PQ nodes in the power system flow, with voltage established by the grid. As the installed capacity of renewable energy continues to increase, the grid's clamping ability over the voltage at the grid connection point is declining. When grid faults occur, voltage or frequency instability or oscillations are likely to occur. To address these grid pain points and support a higher installed capacity of renewable energy, grid-connected wind turbine units have emerged as one solution.

[0005] For grid-connected wind turbines, it is of great significance to know how to control them so that they can quickly and actively support the stability of grid frequency and voltage.

[0006] Summary of the Invention

[0007] This application provides a control method, device, unit, and medium for a grid-connected doubly-fed induction generator (DFIG), which enables the DFIG to quickly and actively support grid frequency and voltage stability.

[0008] In a first aspect, embodiments of this application provide a control method for a grid-connected doubly-fed induction generator (DFIG) wind turbine, the DFIG wind turbine including a grid-side converter, the method comprising:

[0009] The internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly fed wind turbine generator are obtained. The measurement parameters include voltage and current measurements.

[0010] The reference value of the current at the grid connection point is determined based on the internal potential parameters, voltage measurements, and virtual impedance reference values.

[0011] Determine the voltage reference value of the grid-side converter based on the current reference value and the current measurement value;

[0012] The grid-side converter is controlled based on a voltage reference value to ensure that the difference between the output voltage of the grid-side converter and the voltage reference value is less than a preset threshold.

[0013] Secondly, embodiments of this application provide a control device for a grid-connected doubly-fed induction generator (DFIG) wind turbine generator, which includes a grid-side converter. The device includes:

[0014] The acquisition module is used to acquire the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly fed wind turbine generator. The measurement parameters include voltage and current measurements.

[0015] The determination module is used to determine the current reference value at the grid connection point based on the internal potential parameters, voltage measurement values, and virtual impedance reference values; and to determine the voltage reference value of the grid-side converter based on the current reference value and current measurement values.

[0016] The control module is used to control the grid-side converter according to the voltage reference value, so that the difference between the output voltage value of the grid-side converter and the voltage reference value is less than a preset threshold.

[0017] Thirdly, embodiments of this application provide a grid-type doubly-fed wind turbine generator, comprising:

[0018] A doubly-fed generator, the stator of which is configured to be connected to the power grid;

[0019] The generator-side converter has its AC terminal connected to the rotor of the doubly-fed generator.

[0020] The grid-side converter has its AC terminal configured to be connected to the power grid, and its DC terminal is connected to the DC terminal of the generator-side converter via a DC bus.

[0021] The converter controller, connected to both the turbine-side converter and the grid-side converter, is configured to acquire the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly-fed wind turbine generator. The measurement parameters include voltage and current measurements. Based on the internal potential parameters, voltage measurements, and virtual impedance reference values, the current reference value at the grid connection point is determined. Based on the current reference value and current measurements, the voltage reference value of the grid-side converter is determined. The grid-side converter is controlled based on the voltage reference value to ensure that the difference between the output voltage of the grid-side converter and the voltage reference value is less than a preset threshold.

[0022] Fourthly, embodiments of this application provide a computer-readable storage medium having computer program instructions stored thereon, which, when executed by a processor, implement the method described in the first aspect.

[0023] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the method described in the first aspect.

[0024] In this embodiment, the current reference value at the grid connection point is determined based on the measured parameters at the grid connection point, combined with the internal potential parameters and virtual impedance reference value of the grid-connected doubly-fed induction generator (DFIG). Then, the voltage reference value of the grid-side converter is determined based on the current reference value at the grid connection point, and the grid-side converter is modulated based on this voltage reference value, thus achieving closed-loop control of the grid-side converter. The measured parameters at the grid connection point allow for timely detection of grid changes; therefore, the closed-loop control based on these parameters can quickly and proactively modulate the voltage of the grid-side converter, ensuring it reaches a given value, thereby enabling the wind turbine to actively support grid voltage and frequency stability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 is a structural schematic diagram of a grid-type wind turbine provided in an embodiment of this application;

[0027] Figure 2 is a flowchart of a control method for a grid-type doubly fed wind turbine generator provided in an embodiment of this application;

[0028] Figure 3 is a flowchart of determining the internal potential phase angle of a grid-type doubly fed wind turbine generator according to an embodiment of this application;

[0029] Figure 4 is a logic diagram for determining the phase angle of internal potential according to an embodiment of this application;

[0030] Figure 5 is a logic diagram of determining a given value of active power according to an embodiment of this application;

[0031] Figure 6 is a flowchart of determining the internal potential amplitude of a grid-type doubly fed wind turbine generator according to an embodiment of this application;

[0032] Figure 7 is a flowchart of another control method for a grid-type doubly fed wind turbine generator provided in an embodiment of this application;

[0033] Figure 8 is a flowchart of another control method for a grid-type doubly fed wind turbine generator provided in an embodiment of this application;

[0034] Figure 9 is a structural diagram of a control device for a grid-type doubly fed wind turbine provided in an embodiment of this application. Detailed Implementation

[0035] The features and exemplary embodiments of various aspects of this application will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a comprehensive understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this application by illustrating examples. In the accompanying drawings and the following description, at least some well-known structures and techniques are not shown to avoid unnecessarily obscuring the application; and, for clarity, the dimensions of some structures may be exaggerated. Furthermore, the features, structures, or characteristics described below can be combined in any suitable manner in one or more embodiments.

[0036] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of the cable-stayed tower and wind turbine generator set of this application. It should also be noted in the description of this application that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections or indirect connections. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0037] As the proportion of installed capacity of new energy sources continues to increase, the grid's clamping ability on the voltage at the grid connection point is constantly decreasing. When a grid fault occurs, voltage and frequency stability issues are likely to arise. To address these grid pain points and support a higher installed capacity of new energy sources, grid-connected wind turbine units have emerged as one solution.

[0038] Grid-connected wind turbines simulate the rotor motion equations of synchronous generators, exhibiting voltage source control and self-synchronizing grid characteristics. They directly control the amplitude and phase of their output voltage, supporting grid frequency and voltage stability, and providing inertia and damping support to the system. They also have islanding operation capabilities and are suitable for high-proportion new energy power systems with low strength and low inertia.

[0039] In practical applications, it is of great significance to control grid-connected wind turbines so that they can quickly and actively support the stability of grid frequency and voltage.

[0040] Therefore, this application provides a control method, device, unit, and medium for grid-connected doubly-fed wind turbine generators, which can enable grid-connected doubly-fed wind turbine generators to quickly and actively support grid frequency and voltage stability.

[0041] Figure 1 is a structural schematic diagram of a grid-type wind turbine provided in an embodiment of this application. As shown in Figure 1, the grid-type wind turbine 10 may include an impeller 100, a gearbox 101, a double-fed induction generator (DFIG) 102, a rotor-side converter (RSC) 103, a grid-side converter (GSC) 104, an energy storage unit 105, a DC / DC converter 106, and a converter controller 107.

[0042] The impeller 100 is connected to the low-speed pole of the gearbox 101, the high-speed pole of the gearbox 101 is connected to the shaft of the doubly-fed generator 102, the stator of the doubly-fed generator 102 is configured to be connected to the power grid, the rotor of the doubly-fed generator 102 is connected to the AC terminal of the generator-side converter 103, the DC terminal of the generator-side converter 103 is connected to the DC terminal of the grid-side converter 104 through a DC bus, and the AC terminal of the grid-side converter 104 is configured to be connected to the grid cable.

[0043] The energy storage unit 105 can be a battery pack, supercapacitor, or other component with charging and discharging capabilities. The energy storage unit 105 is connected to the DC bus of the grid-side converter 104 via a DC / DC converter 106. The energy storage unit 105 and the DC / DC converter 106 are configured to stabilize the voltage of the DC bus.

[0044] The converter controller 107 is connected to the machine-side converter 103 and the grid-side converter 104 respectively. In this embodiment, the converter controller 107 can enable the grid-connected wind turbine 10 to quickly and actively support the grid frequency and voltage stability by performing closed-loop control on the grid-side converter 104.

[0045] Figure 2 is a flowchart of a control method for a grid-type doubly fed wind turbine provided in an embodiment of this application. This control method for a grid-type doubly fed wind turbine can be applied to the converter controller shown in Figure 1.

[0046] As shown in Figure 2, the control method for this grid-type doubly-fed wind turbine generator may include the following steps:

[0047] S210. Obtain the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly-fed wind turbine.

[0048] The measurement parameters include voltage and current measurements.

[0049] S220. Determine the reference current value at the grid connection point based on the internal potential parameters, voltage measurements, and virtual impedance reference values.

[0050] S230. Determine the voltage reference value of the grid-side converter based on the current reference value and the current measurement value.

[0051] S240. Control the grid-side converter according to the voltage reference value so that the difference between the output voltage value of the grid-side converter and the voltage reference value is less than a preset threshold.

[0052] In the above embodiments provided in this application, changes in the power grid can be detected in a timely manner through the measurement parameters of the grid connection point. When changes in the power grid are detected, the grid-side converter can be closed-loop controlled according to the changes in the power grid combined with the internal potential parameters and virtual impedance reference values ​​of the grid-connected doubly fed wind turbine, so as to modulate the voltage of the grid-side converter and make the voltage of the grid-side converter reach a given value, thereby enabling the wind turbine to actively support the stability of the grid voltage and frequency.

[0053] The above steps are explained in detail below:

[0054] The internal electromotive force (EMF) of a generator refers to the symmetrical three-phase EMF induced within the stator windings by the main magnetic field forming a rotating magnetic field in the air gap when the generator rotor rotates at synchronous speed, "cutting" the stator windings. In S210 of this application embodiment, the internal EMF parameters can be parameters that characterize the internal EMF features of a grid-connected doubly-fed wind turbine generator, such as the internal EMF amplitude and internal EMF phase angle.

[0055] The grid connection point is the point between the box-type transformer and the power grid. For example, a box-type transformer can connect one or more wind turbine units to the power grid. In this embodiment, the connection of a grid-type doubly fed wind turbine unit to the power grid is taken as an example.

[0056] The measurement parameters of the grid connection point can be parameter values ​​obtained by measuring the electrical signals at the grid connection point. For example, the measurement parameters of the grid connection point can include voltage and current measurements. By measuring the voltage at the grid connection point, a voltage measurement value can be obtained; similarly, by measuring the current at the grid connection point, a current measurement value can be obtained. The voltage measurement value is the three-phase voltage value in a three-phase stationary coordinate system, and the current measurement value is the three-phase current value in a three-phase stationary coordinate system.

[0057] Taking a grid-connected doubly-fed induction generator (DFIG) wind turbine connected to the grid via a box-type transformer as an example, the measured current at the grid connection point is the measured output current of the DFIG wind turbine. In this embodiment, the output current of the DFIG wind turbine is equal to the sum of the output current of the branch where the stator is located and the output current of the branch where the grid-side converter is located. That is, in this embodiment, the grid-side converter can be closed-loop controlled based on the sum of the output current of the branch where the stator is located and the output current of the branch where the grid-side converter is located.

[0058] Virtual impedance can include virtual inductance and virtual resistance; correspondingly, virtual impedance reference values ​​can include virtual inductance reference values ​​and virtual resistance reference values. The magnitudes of the virtual inductance reference values ​​and virtual resistance reference values ​​can be set according to the scenario, requirements, and experience.

[0059] For example, the converter controller can periodically acquire the internal electromotive force parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly-fed induction generator (DFIG) to achieve periodic control of the grid-side converter. The duration of each cycle can be set relatively short, thereby enabling more timely detection of grid changes and allowing the DFIG to support grid frequency and voltage stability more quickly.

[0060] In S220, exemplarily, the current reference value at the grid connection point may include the A-axis current reference value, B-axis current reference value, and C-axis current reference value given at the grid connection point in a three-phase stationary coordinate system. Exemplarily, the current reference value at the grid connection point may also include the α-axis current reference value and β-axis current reference value given at the grid connection point in a two-phase stationary coordinate system. That is, the embodiments of this application can perform closed-loop control of the grid-side converter based on parameters obtained in a three-phase stationary coordinate system, or they can perform closed-loop control of the grid-side converter based on parameters obtained in a two-phase stationary coordinate system.

[0061] In this embodiment, the current reference value at the grid connection point can be determined based on the internal potential parameter, the voltage measurement value at the grid connection point, and the virtual impedance reference value. That is, this embodiment can dynamically determine the current reference value at the grid connection point based on changes in the power grid, achieving proactive response and support to the power grid.

[0062] Taking the closed-loop control of the grid-side converter using parameters obtained in a two-phase stationary coordinate system as an example, the three-phase voltage measurements can be subjected to Clark transformation to obtain the α-axis voltage measurement and β-axis voltage measurement. Then, based on the internal potential parameters, virtual impedance reference values, and the α-axis and β-axis voltage measurements, the α-axis current reference values ​​and β-axis current reference values ​​at the grid connection point can be obtained.

[0063] In S230, taking the closed-loop control of the grid-side converter based on the parameters obtained in the three-phase stationary coordinate system as an example, the voltage reference values ​​here can be the A-axis voltage value, B-axis voltage value and C-axis voltage value given by the grid-side converter in the three-phase stationary coordinate system.

[0064] Taking closed-loop control of the grid-side converter based on parameters obtained in a two-phase stationary coordinate system as an example, the voltage reference values ​​here can be the α-axis and β-axis voltage values ​​of the grid-side converter given in the two-phase stationary coordinate system. In this case, the α-axis and β-axis voltage reference values ​​of the grid-side converter can be dynamically determined based on the current measurement value at the grid connection point and the α-axis and β-axis current reference values ​​at the grid connection point, thus realizing closed-loop control of the grid-side converter. By modulating the voltage of the grid-side converter, the grid-type doubly-fed induction generator can quickly and actively support the grid frequency and voltage stability.

[0065] For example, the above current measurement values ​​can be converted into α-axis current measurement values ​​and β-axis current measurement values ​​by using coordinate transformation between a three-phase stationary coordinate system and a two-phase stationary coordinate system. Then, based on the α-axis current measurement values ​​and α-axis current reference values, the α-axis voltage reference value of the grid-side converter can be obtained, and based on the β-axis current measurement values ​​and β-axis current reference values, the β-axis voltage reference value of the grid-side converter can be obtained, providing a voltage basis for subsequent grid-side converter modulation.

[0066] In S240, the preset threshold can be a relatively small value, thereby improving the control effect.

[0067] In some embodiments, the α-axis voltage of the grid-side converter can be modulated according to the α-axis voltage reference value, such that the difference between the α-axis voltage of the grid-side converter and the α-axis voltage reference value is less than a first threshold. Similarly, the β-axis voltage of the grid-side converter can be modulated according to the β-axis voltage reference value, such that the difference between the β-axis voltage of the grid-side converter and the β-axis voltage reference value is less than a second threshold, thereby achieving complete closed-loop control of the grid-side converter. The first threshold and the second threshold are collectively referred to as preset thresholds.

[0068] In some embodiments, the A-axis voltage of the grid-side converter can also be modulated according to the A-axis voltage reference value, such that the difference between the A-axis voltage of the grid-side converter and the A-axis voltage reference value is less than a third threshold. Similarly, the B-axis voltage of the grid-side converter can be modulated according to the B-axis voltage reference value, such that the difference between the B-axis voltage of the grid-side converter and the B-axis voltage reference value is less than a fourth threshold. Similarly, the C-axis voltage of the grid-side converter can be modulated according to the C-axis voltage reference value, such that the difference between the C-axis voltage of the grid-side converter and the C-axis voltage reference value is less than a fifth threshold. The third, fourth, and fifth thresholds are collectively referred to as preset thresholds.

[0069] This application embodiment can detect changes in the power grid in a timely manner by measuring the voltage and current at the grid connection point. Based on the measured voltage and current at the grid connection point, and combined with the internal potential parameters of the grid-connected doubly-fed wind turbine, the voltage of the grid-side converter is actively modulated, thereby realizing the rapid and active support effect of the grid-connected doubly-fed wind turbine on the power grid.

[0070] Taking the internal potential parameters, including the internal potential phase angle, as an example, the process of determining the internal potential phase angle can include S310-S330 as shown in Figure 3. The specific contents of S310-S330 will be explained below.

[0071] In S310, the internal potential angular frequency ω and the grid angular frequency are obtained. Active power setpoint P of grid-side converter set The active power measurement value P at the grid connection point g .

[0072] Active power setpoint P of grid-side converter set It can be set according to the scenario, needs, experience, etc., and there are no specific limitations here.

[0073] In S320, the grid angular frequency is determined. The angular frequency difference between the internal potential angular frequency ω and the active power setpoint P set With active power measurement value P g The power difference.

[0074] In this embodiment, the power grid angular frequency is introduced. And calculate the angular frequency of the power grid. The angular frequency difference between the internal potential angular frequency ω and the angular frequency ω is used to provide inertia and damping support, so that the grid-connected doubly fed wind turbine can better support the grid frequency.

[0075] In S330, the internal potential phase angle θ is determined based on the power difference, the angular frequency difference, and the internal potential angular frequency ω.

[0076] Figure 4 is a logic diagram of determining the internal potential phase angle according to an embodiment of this application. The internal potential phase angle can be obtained by combining the following formula with the logic diagram.

[0077] For example,

[0078] Among them, P set P is the given value for active power. g The active power measurement value is given, and ω is the internal potential angular frequency. Let ω be the grid angular frequency, ΔT be the torque change, D be the damping coefficient, J be the moment of inertia, and P be the torque. set -P g This is the power difference. Let θ be the angular frequency difference, θ be the phase angle of the internal potential, and s be the complex variable in the Laplace transform.

[0079] In the process of simulating a virtual synchronous machine, the embodiment of this application introduces the angular frequency difference between the grid angular frequency and the internal potential angular frequency, enabling the grid-type doubly fed wind turbine to actively respond to and support the grid frequency, thereby achieving power synchronization control and avoiding safety risks.

[0080] In some embodiments, the active power setpoint P of the grid-side converter set It can also be dynamically adjusted according to the state of charge of the energy storage unit.

[0081] For example, prior to S210, the control method for this grid-type doubly-fed wind turbine may further include the following steps:

[0082] Obtain the State of Charge (SOC) reference value*, the State of Charge (SOC) measurement value, and the active power setpoint at the grid connection point for the energy storage unit.

[0083] Determine the difference in state of charge between the reference value SOC* and the measured value SOC;

[0084] According to the power conversion coefficient K D The power conversion is performed on the state of charge difference to obtain the power change ΔP corresponding to the state of charge difference;

[0085] Based on the active power given value The difference between the active power setpoint P of the grid-side converter and the power change ΔP is used to determine the active power setpoint P. set .

[0086] The State of Charge (SOC) reference value here refers to the given SOC value of the energy storage unit; for example, the SOC reference value can be set to 80%-90%. The measured SOC value is the actual measured SOC of the energy storage unit. The active power setpoint at the grid connection point... Issued by the power grid dispatch center.

[0087] Power conversion coefficient K D Used to convert the state of charge into active power, different states of charge correspond to different power conversion coefficients K. D Power conversion factor K D It can be determined and stored in advance through experiments, experience, and other methods.

[0088] Figure 5 is a logic diagram illustrating the determination of an active power setpoint according to an embodiment of this application. Based on this logic diagram and the following formula, the active power setpoint P can be obtained. set .

[0089] For example, Min≤P set ≤Max, where Min and Max are the limiting values.

[0090] For example, when the calculated P set When the value is between Min and Max, the active power setpoint of the grid-side converter is determined by the calculated P. set When the calculated P set When the value is ≥Max, determine the active power setpoint P of the grid-side converter. set =Max, when the calculated P set When ≤Min, determine the active power setpoint P of the grid-side converter. set =Min.

[0091] With the active power setpoint from the grid remaining unchanged, the embodiments of this application can dynamically adjust the active power setpoint of the grid-side converter according to the state of charge of the energy storage unit, thereby achieving rapid and active support for the grid while maintaining the stability of the DC bus voltage.

[0092] Taking the internal potential parameter including the internal potential amplitude as an example, the process of determining the internal potential amplitude can include S610-S640 as shown in Figure 6.

[0093] In S610, in response to the grid-connected doubly-fed induction generator being in reactive power control mode, the reactive power measurement value Q at the grid connection point is acquired. e The reactive power setpoint received by the grid-type doubly-fed wind turbine generator. and the reference amplitude E of the internal potential B .

[0094] reactive power setpoint The reactive power reference value issued by the power grid, and the reference amplitude E of the internal electromotive force. B The magnitude of the reference voltage for the internal potential.

[0095] For example, when a grid-connected doubly-fed induction generator (DFIG) is in reactive power control mode, the converter controller can obtain the reactive power measurement value Q at the grid connection point. e The reactive power setpoint received by the grid-type doubly-fed wind turbine generator. and the reference amplitude E of the internal potential B This provides a data foundation for subsequent calculations of the internal potential amplitude.

[0096] In S620, the reactive power setpoint is determined. With reactive power measurement value Q e The reactive power difference ΔQ.

[0097] For example,

[0098] In S630, the reactive power difference ΔQ is processed by proportional-integral processing to obtain the voltage amplitude change ΔE.

[0099] For example, the reactive power difference ΔQ can be proportionally processed to obtain the first voltage amplitude change ΔE1, and the reactive power difference ΔQ can be integrally processed to obtain the second voltage amplitude change ΔE2. The final voltage amplitude change ΔE is the sum of the first voltage amplitude change ΔE1 and the second voltage amplitude change ΔE2, that is, ΔE = ΔE1 + ΔE2.

[0100] The proportional coefficient and integral coefficient can be set according to the scenario, needs, experience, etc., and are not limited here.

[0101] In S640, based on the reference amplitude E B The sum of the voltage amplitude change ΔE and the internal potential amplitude E* is used to determine the internal potential amplitude.

[0102] For example, E* = ΔE + E B .

[0103] In this embodiment of the application, when the grid-connected doubly-fed induction generator (DFIG) is in reactive power control mode, the converter controller can calculate the internal potential amplitude of the DFIG based on the reactive power setpoint and reactive power measurement value at the grid connection point, as well as the reference amplitude of the internal potential. This provides a basis for closed-loop control of the grid-side converter, enabling the DFIG to quickly and actively support the stability of the grid frequency and voltage.

[0104] Figure 7 is a flowchart of another control method for a grid-type doubly fed wind turbine provided in an embodiment of this application. The difference between Figure 7 and Figure 2 is that S220 in Figure 2 can be further refined into S2201-S2202 in Figure 7, S230 in Figure 2 can be further refined into S2301-S2303 in Figure 7, and S240 in Figure 2 can be further refined into S2401 in Figure 7.

[0105] In S2201, the virtual impedance voltage drop is determined based on the internal potential parameters and voltage measurements.

[0106] The virtual impedance voltage drop is the voltage drop across the virtual impedance in the above embodiments. The virtual impedance voltage drop can be determined based on the internal potential parameters and voltage measurements.

[0107] Taking closed-loop control of the grid-side converter based on parameters obtained in a two-phase stationary coordinate system as an example, exemplarily, the d-axis and q-axis voltage amplitudes can be obtained by performing an inverse Park transformation based on the internal potential phase angle θ, yielding the α-axis and β-axis voltage amplitudes; the voltage measurements can then be transformed using a Clark transformation to obtain the α-axis and β-axis voltage measurements. The virtual impedance voltage drop represents the first voltage difference between the α-axis voltage amplitude and the α-axis voltage measurement, and the second voltage difference between the β-axis voltage amplitude and the β-axis voltage measurement.

[0108] In this embodiment, the d-axis voltage amplitude is the internal potential amplitude E* determined in the above embodiments, and the q-axis voltage amplitude is 0. The α-axis voltage amplitude can be obtained through the inverse Park transformation. and β-axis voltage amplitude

[0109] The Clark transformation can be used to convert voltage measurements from a three-phase stationary coordinate system to a two-phase stationary coordinate system, thus obtaining the α-axis voltage measurement. and β-axis voltage measurement value From this, the first pressure difference can be obtained. Second pressure difference That is, the virtual impedance voltage drops are ΔU1 and ΔU2, respectively.

[0110] In S2202, the reference values ​​of the α-axis current and β-axis current at the grid connection point are determined based on the ratio of the virtual impedance voltage drop to the virtual impedance reference value.

[0111] For example, the virtual impedance can be expressed as L v s+R v , where L v R is the virtual inductance value. v This is a virtual resistance value.

[0112] For example, the α-axis current reference value β-axis current reference value

[0113] This application embodiment utilizes the internal potential phase angle determined in the above embodiments to transform the internal potential amplitude and simultaneously transform the voltage measurement value at the grid connection point. The internal potential amplitude and voltage measurement value are transformed into the αβ coordinate system to obtain the α-axis current reference value and β-axis current reference value at the grid connection point. This achieves proactive sensing and response to the power grid. Subsequently, the corresponding voltage reference value can be determined based on this current reference value to modulate the grid-side converter. By modulating the grid-side converter, this grid-connected doubly-fed induction generator can quickly and proactively support grid frequency and voltage stability, mitigating safety risks.

[0114] In S2301, the current measurement values ​​are transformed by coordinates to obtain the α-axis current measurement values ​​and the β-axis current measurement values.

[0115] For example, by using coordinate transformation between a three-phase stationary coordinate system and a two-phase stationary coordinate system, the three-phase current measurement value can be converted into the α-axis current measurement value I. α_WT and β-axis current measurement value I β_WT .

[0116] In S2302, the reference value for the α-axis current is determined. Compared with the α-axis current measurement value I α_WT First current difference ΔI α_WT and β-axis current reference value Compared with the β-axis current measurement value I β_WT The second current difference ΔI β_WT .

[0117] In S2303, the first current difference ΔI α_WT By performing proportional resonance processing, the reference value of the α-axis voltage of the grid-side converter is obtained. And the second current difference ΔI β_WT By performing proportional resonance processing, the reference value of the β-axis voltage of the grid-side converter is obtained.

[0118] The magnitudes of the coefficients of the proportional resonance can be set according to the scenario, requirements, experience, etc., and are not limited here.

[0119] In S2401, the grid-side converter is controlled based on the α-axis voltage reference value and the β-axis voltage reference value to make the difference between the α-axis voltage of the grid-side converter and the α-axis voltage reference value less than a first threshold and to make the difference between the β-axis voltage of the grid-side converter and the β-axis voltage reference value less than a second threshold.

[0120] The voltage modulation processes for the α-axis and β-axis are similar.

[0121] In some embodiments, the current measurement at the grid connection point may include the sum of the output current measurement of the branch where the stator of the grid-connected doubly-fed induction generator (DFIG) is located and the output current measurement of the branch where the grid-side converter is located. That is, the current measurement at the grid connection point may include the output current measurement of the branch where the stator is located and the output current measurement of the branch where the grid-side converter is located. In practical applications, since the current generated by filter capacitors, power distribution equipment, etc., is relatively small, the output current measurement of the branch where the stator is located can also be approximated as the output current measurement of the stator, and the output current measurement of the branch where the grid-side converter is located can also be approximated as the output current measurement of the grid-side converter. In other words, the current measurement at the grid connection point can be approximated as the sum of the output current measurement of the stator and the output current measurement of the grid-side converter.

[0122] Based on this, the control method for grid-type doubly fed wind turbine generators provided in the embodiments of this application may include the steps shown in FIG8. The difference between FIG8 and FIG2 is that S230 in FIG2 can be refined into S2304-S2305 in FIG8.

[0123] In S2304, the output current reference value of the branch where the grid-side converter is located is determined based on the current reference value and the output current measurement value of the branch where the stator is located.

[0124] The output current measurement value of the branch where the stator is located is the current measurement value of the three-phase current in the three-phase stationary coordinate system. Through Clark transformation, the output current measurement value of the branch where the stator is located can be converted to the two-phase stationary coordinate system to obtain the α-axis current measurement value and β-axis current measurement value of the branch where the stator is located.

[0125] The output current reference value of the branch where the grid-side converter is located can be the output current reference value in a three-phase stationary coordinate system or the output current reference value in a two-phase stationary coordinate system.

[0126] In a two-phase stationary coordinate system, for example, the α-axis output current reference value of the branch where the grid-connected converter is located can be obtained based on the difference between the α-axis current reference value at the grid connection point and the measured α-axis current value of the branch where the stator is located. Similarly, the β-axis output current reference value of the branch where the grid-connected converter is located can be obtained based on the difference between the β-axis current reference value at the grid connection point and the measured β-axis current value of the branch where the stator is located.

[0127] In a three-phase stationary coordinate system, for example, the A-axis output current reference value of the branch where the grid-connected converter is located can be obtained based on the difference between the A-axis current reference value at the grid connection point and the measured A-axis current value of the branch where the stator is located. Similarly, the B-axis output current reference value of the branch where the grid-connected converter is located can be obtained based on the difference between the B-axis current reference value at the grid connection point and the measured B-axis current value of the branch where the stator is located. Similarly, the C-axis output current reference value of the branch where the grid-connected converter is located can be obtained based on the difference between the C-axis current reference value at the grid connection point and the measured C-axis current value of the branch where the stator is located.

[0128] In S2305, the voltage reference value of the grid-side converter is determined based on the output current reference value of the branch where the grid-side converter is located and the measured output current value of the branch where the grid-side converter is located.

[0129] Taking a two-phase stationary coordinate system as an example, the reference values ​​of the α-axis voltage and β-axis voltage of the grid-side converter can be determined based on the reference values ​​of the α-axis output current, the reference values ​​of the β-axis output current, and the measured values ​​of the output current of the grid-side converter.

[0130] The output current measurement value of the grid-side converter here is the current measurement value of the three-phase current in the three-phase stationary coordinate system. Through Clark transformation, the output current measurement value of the grid-side converter can be transformed to a two-phase stationary coordinate system to obtain the α-axis current measurement value and β-axis current measurement value of the grid-side converter.

[0131] For example, a third current difference between the α-axis output current reference value and the measured α-axis current value of the grid-side converter can be determined, as well as a fourth current difference between the β-axis output current reference value and the measured β-axis current value of the grid-side converter. By performing proportional resonance processing on the third current difference, the α-axis voltage reference value of the grid-side converter can be obtained. By performing proportional resonance processing on the fourth current difference, the β-axis voltage reference value of the grid-side converter can be obtained.

[0132] The magnitudes of the coefficients of the proportional resonance can be set according to the scenario, requirements, experience, etc., and are not limited here.

[0133] The process of determining the voltage reference value of the grid-side converter in the three-phase stationary coordinate system is similar to that in the two-phase stationary coordinate system, and will not be repeated here.

[0134] In this embodiment, after obtaining the current reference value at the grid connection point, the output current reference value of the grid-side converter branch can be obtained by utilizing the relationship between the measured current value at the grid connection point, the output current of the branch where the stator is located, and the output current of the branch where the grid-side converter is located. Then, combined with the measured output current value of the branch where the grid-side converter is located, the voltage reference value of the grid-side converter can be obtained. This achieves the purpose of closed-loop control of the grid-side converter based on the current reference value of the branch where the grid-side converter is located, thus improving the control effect.

[0135] This application's embodiments introduce energy storage units and DC / DC converters into traditional grid-connected wind turbine generators, enabling these units to stabilize the DC bus voltage. Simultaneously, the active power setpoint of the grid-side converter is dynamically adjusted using the state of charge (SBC) of the energy storage unit. Based on this active power setpoint, and combined with the grid angular frequency and internal potential angular frequency, the internal potential phase angle is determined, achieving power synchronization control. Furthermore, based on the internal potential phase angle and amplitude, and combined with voltage and current measurements at the grid connection point, closed-loop control of the grid-side converter is implemented. This allows the grid-connected wind turbine generator to quickly and proactively respond to and support grid frequency and voltage stability, effectively mitigating safety risks.

[0136] Figure 9 is a structural diagram of a control device for a grid-type doubly-fed wind turbine provided in an embodiment of this application. As shown in Figure 9, the control device 900 for the grid-type doubly-fed wind turbine may include:

[0137] The acquisition module 901 is used to acquire the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly fed wind turbine generator. The measurement parameters include voltage measurement values ​​and current measurement values.

[0138] The determination module 902 is used to determine the current reference value at the grid connection point based on the internal potential parameters, voltage measurement values, and virtual impedance reference values; and to determine the voltage reference value of the grid-side converter based on the current reference value and current measurement values.

[0139] The control module 903 is used to control the grid-side converter according to the voltage reference value so that the difference between the output voltage value of the grid-side converter and the voltage reference value is less than a preset threshold.

[0140] This embodiment determines the current reference value at the grid connection point based on the measured parameters at the grid connection point, combined with the internal potential parameters and virtual impedance reference value of the grid-connected doubly-fed induction generator (DFIG). Then, it determines the voltage reference value of the grid-side converter based on the current reference value at the grid connection point, and modulates the grid-side converter based on this voltage reference value, thus achieving closed-loop control of the grid-side converter. The measured parameters at the grid connection point allow for timely detection of grid changes; therefore, the closed-loop control based on these parameters can quickly and proactively modulate the voltage of the grid-side converter, ensuring it reaches a given value, thereby enabling the wind turbine to actively support grid voltage and frequency stability.

[0141] In some embodiments, the internal potential parameter includes the internal potential phase angle;

[0142] The acquisition module 901 is also used to acquire the internal potential angular frequency, the grid angular frequency, the active power setpoint of the grid-side converter, and the active power measurement value at the grid connection point;

[0143] The determination module 902 is also used to determine the angular frequency difference between the grid angular frequency and the internal potential angular frequency, as well as the power difference between the active power setpoint and the active power measurement value; and to determine the internal potential phase angle based on the power difference, the angular frequency difference and the internal potential angular frequency.

[0144] In some embodiments, the grid-connected doubly fed wind turbine also includes an energy storage unit, which is connected to the DC bus of the grid-side converter via a DC / DC converter. The energy storage unit and the DC / DC converter are configured to stabilize the voltage of the DC bus.

[0145] The acquisition module 901 is also used to acquire the state of charge reference value, state of charge measurement value and active power setpoint of the grid connection point of the energy storage unit before acquiring the internal potential parameters, grid connection point measurement parameters and virtual impedance reference value of the grid-connected doubly fed wind turbine generator.

[0146] The determination module 902 is also used to determine the state of charge difference between the reference value and the measured value; to perform power conversion on the state of charge difference according to the power conversion coefficient to obtain the power change corresponding to the state of charge difference; and to determine the active power setpoint of the grid-side converter according to the difference between the active power setpoint and the power change.

[0147] In some embodiments, the internal potential parameter includes the internal potential amplitude;

[0148] The acquisition module 901 is also used to acquire the reactive power measurement value at the grid connection point, the reactive power setpoint received by the grid-connected doubly fed wind turbine, and the reference amplitude of the internal electromotive force in response to the grid-connected doubly fed wind turbine being in reactive power control mode.

[0149] The determination module 902 is also used to determine the reactive power difference between the reactive power setpoint and the reactive power measurement; to perform proportional-integral processing on the reactive power difference to obtain the voltage amplitude change; and to determine the internal potential amplitude based on the sum of the reference amplitude and the voltage amplitude change.

[0150] In some embodiments, the determining module 902 is specifically used for:

[0151] The virtual impedance voltage drop is determined based on the internal potential parameters and voltage measurements.

[0152] The reference values ​​for the α-axis current and β-axis current at the grid connection point are determined based on the ratio of the virtual impedance voltage drop to the virtual impedance reference value.

[0153] In some embodiments, the internal potential parameters include the internal potential amplitude and the internal potential phase angle, and the internal potential amplitude includes the d-axis voltage amplitude and the q-axis voltage amplitude;

[0154] Module 902 is specifically used for:

[0155] Based on the phase angle, coordinate transformation is performed on the d-axis voltage amplitude and the q-axis voltage amplitude to obtain the α-axis voltage amplitude and the β-axis voltage amplitude;

[0156] The voltage measurements are transformed using coordinates to obtain the α-axis voltage measurements and the β-axis voltage measurements.

[0157] The first voltage difference between the α-axis voltage amplitude and the α-axis voltage measurement, and the second voltage difference between the β-axis voltage amplitude and the β-axis voltage measurement are both defined as virtual impedance voltage drops.

[0158] In some embodiments, the determining module 902 is specifically used for:

[0159] The current measurement values ​​are transformed by coordinates to obtain the α-axis current measurement values ​​and the β-axis current measurement values;

[0160] Determine the first current difference between the α-axis current reference value and the α-axis current measurement value, and the second current difference between the β-axis current reference value and the β-axis current measurement value;

[0161] The first current difference is processed by proportional resonance to obtain the α-axis voltage reference value of the grid-side converter, and the second current difference is processed by proportional resonance to obtain the β-axis voltage reference value of the grid-side converter.

[0162] In some embodiments, the current measurement values ​​include the output current measurement value of the branch where the stator of the grid-type doubly fed wind turbine is located and the output current measurement value of the branch where the grid-side converter is located.

[0163] Module 902 is specifically used for:

[0164] Based on the current reference value and the output current measurement value of the branch where the stator is located, determine the output current reference value of the branch where the grid-side converter is located;

[0165] The voltage reference value of the grid-side converter is determined based on the reference value of the output current of the branch where the grid-side converter is located and the measured value of the output current of the branch where the grid-side converter is located.

[0166] The control device for the grid-type doubly-fed wind turbine provided in this application embodiment can realize the various processes in the control method embodiments of the grid-type doubly-fed wind turbine shown in Figures 2-3 and 6-8. To avoid repetition, these processes will not be described again here.

[0167] Based on the same inventive concept, this application also provides a grid-type doubly-fed wind turbine generator, which may include:

[0168] A doubly-fed generator, the stator of which is configured to be connected to the power grid;

[0169] The generator-side converter has its AC terminal connected to the rotor of the doubly-fed generator.

[0170] The grid-side converter has its AC terminal configured to be connected to the power grid, and its DC terminal is connected to the DC terminal of the generator-side converter via a DC bus.

[0171] The converter controller, connected to both the turbine-side converter and the grid-side converter, is configured to acquire the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly-fed wind turbine generator. The measurement parameters include voltage and current measurements. Based on the internal potential parameters, voltage measurements, and virtual impedance reference values, the current reference value at the grid connection point is determined. Based on the current reference value and current measurements, the voltage reference value of the grid-side converter is determined. The grid-side converter is controlled based on the voltage reference value to ensure that the difference between the output voltage of the grid-side converter and the voltage reference value is less than a preset threshold.

[0172] In some embodiments, the grid-type doubly fed wind turbine generator also includes an energy storage unit;

[0173] The energy storage unit is connected to the DC bus of the grid-side converter via a DC / DC converter, and the energy storage unit and the DC / DC converter are configured to stabilize the voltage of the DC bus.

[0174] The specific structure of the grid-type doubly fed wind turbine can be seen in Figure 1. Other related content can be found in the above embodiments. For the sake of brevity, it will not be described in detail here.

[0175] This application's embodiments introduce energy storage units and DC / DC converters into traditional grid-connected wind turbine generators, enabling these units to stabilize the DC bus voltage. Simultaneously, the active power setpoint of the grid-side converter is dynamically adjusted using the state of charge (SBC) of the energy storage unit. Based on this active power setpoint, and combined with the grid angular frequency and internal potential angular frequency, the internal potential phase angle is determined, achieving power synchronization control. Furthermore, based on the internal potential phase angle and amplitude, and combined with voltage and current measurements at the grid connection point, closed-loop control of the grid-side converter is implemented. This allows the grid-connected wind turbine generator to quickly and proactively respond to and support grid frequency and voltage stability, effectively mitigating safety risks.

[0176] Furthermore, in conjunction with the control method for grid-connected doubly-fed induction generators in the above embodiments, this application embodiment can provide a computer storage medium for implementation. This computer storage medium stores computer program instructions; when the computer program instructions are executed by a processor, they implement each process of any of the control methods for grid-connected doubly-fed induction generators in the above embodiments, achieving the same technical effect. To avoid repetition, further details are omitted here.

[0177] In addition, in conjunction with the control method of the grid-type doubly-fed wind turbine in the above embodiments, this application also provides a computer program product, including a computer program. When the computer program is executed by at least one processor, it implements the various processes of any of the control method embodiments of the grid-type doubly-fed wind turbine in the above embodiments and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0178] It should be clarified that this application is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of this application is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of this application.

[0179] The functional blocks shown in the above block diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0180] It should also be noted that the exemplary embodiments mentioned in this application describe methods or systems based on a series of steps or apparatus. However, this application is not limited to the order of the above steps; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0181] The aspects of embodiments of this application have been described above with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It should be understood that each block in the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to create a machine such that these instructions, executable via the processor of the computer or other programmable data processing apparatus, enable the implementation of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. Such a processor can be, but is not limited to, a general-purpose processor, a special-purpose processor, a special application processor, or a field-programmable logic circuit. It is also understood that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can also be implemented by dedicated hardware performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0182] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A grid-connected doubly-fed wind turbine generator, comprising: A doubly-fed generator, wherein the stator of the doubly-fed generator is configured to be connected to the power grid; A generator-side converter, wherein the AC terminal of the generator-side converter is connected to the rotor of the doubly-fed generator; A grid-side converter, wherein the AC terminal of the grid-side converter is configured to be connected to the power grid, and the DC terminal of the grid-side converter is connected to the DC terminal of the generator-side converter via a DC bus; A converter controller, which is connected to the machine-side converter and the grid-side converter, is configured to acquire the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly-fed wind turbine generator, wherein the measurement parameters include voltage measurement values ​​and current measurement values. The reference value of the current at the grid connection point is determined based on the internal potential parameter, the voltage measurement value, and the virtual impedance reference value. The voltage reference value of the grid-side converter is determined based on the current reference value and the current measurement value. The grid-side converter is controlled according to the voltage reference value so that the difference between the output voltage value of the grid-side converter and the voltage reference value is less than a preset threshold.

2. The grid-type doubly-fed wind turbine generator according to claim 1, wherein, The grid-type doubly fed wind turbine also includes an energy storage unit; The energy storage unit is connected to the DC bus of the grid-side converter via a DC / DC converter, and the energy storage unit and the DC / DC converter are configured to stabilize the voltage of the DC bus.

3. A control method for a grid-connected doubly-fed induction generator (DFIG), wherein the DFIG includes a grid-side converter, and the method includes: The internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly fed wind turbine generator are obtained. The measurement parameters include voltage measurement values ​​and current measurement values. The reference value of the current at the grid connection point is determined based on the internal potential parameter, the voltage measurement value, and the virtual impedance reference value. The voltage reference value of the grid-side converter is determined based on the current reference value and the current measurement value. The grid-side converter is controlled according to the voltage reference value to enable the grid-side converter to... The difference between the output voltage of the device and the voltage reference value is less than a preset threshold.

4. The method according to claim 3, wherein, The internal potential parameters include the internal potential phase angle; The acquisition of the internal potential parameters of the grid-type doubly-fed wind turbine includes: Obtain the internal potential angular frequency, the grid angular frequency, the active power setpoint of the grid-side converter, and the active power measurement value at the grid connection point; Determine the angular frequency difference between the grid angular frequency and the internal potential angular frequency, and the power difference between the active power setpoint and the active power measurement value; The internal potential phase angle is determined based on the power difference, the angular frequency difference, and the internal potential angular frequency.

5. The method according to claim 3 or 4, wherein, The grid-type doubly fed wind turbine also includes an energy storage unit, which is connected to the DC bus of the grid-side converter via a DC / DC converter. The energy storage unit and the DC / DC converter are configured to stabilize the voltage of the DC bus. Before obtaining the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference value of the grid-connected doubly-fed wind turbine generator, the method further includes: Obtain the state of charge reference value, state of charge measurement value, and active power setpoint of the grid connection point of the energy storage unit; Determine the state of charge difference between the reference value and the measured value. Based on the power conversion coefficient, the power conversion is performed on the state of charge difference to obtain the power change corresponding to the state of charge difference; The active power setpoint of the grid-side converter is determined based on the difference between the active power setpoint and the power change.

6. The method according to claim 3 or 4, wherein, The internal potential parameter includes the internal potential amplitude; The acquisition of the internal potential parameters of the grid-type doubly-fed wind turbine includes: In response to the grid-connected doubly-fed wind turbine being in reactive power control mode, the reactive power measurement value at the grid connection point, the reactive power setpoint received by the grid-connected doubly-fed wind turbine, and the reference amplitude of the internal electromotive force are acquired. Determine the reactive power difference between the given reactive power value and the measured reactive power value; The voltage amplitude change is obtained by performing proportional-integral processing on the reactive power difference. The internal potential amplitude is determined based on the sum of the reference amplitude and the voltage amplitude change.

7. The method according to claim 3 or 4, wherein, The step of determining the current reference value at the grid connection point based on the internal potential parameter, the voltage measurement value, and the virtual impedance reference value includes: The virtual impedance voltage drop is determined based on the internal potential parameters and the voltage measurement values. The α-axis current reference value and β-axis current reference value of the grid connection point are determined based on the ratio of the virtual impedance voltage drop to the virtual impedance reference value.

8. The method according to claim 7, wherein, The internal potential parameters include the internal potential amplitude and the internal potential phase angle, and the internal potential amplitude includes the d-axis voltage amplitude and the q-axis voltage amplitude; The step of determining the virtual impedance voltage drop based on the internal potential parameter and the voltage measurement value includes: Based on the phase angle, coordinate transformation is performed on the d-axis voltage amplitude and the q-axis voltage amplitude to obtain the α-axis voltage amplitude and the β-axis voltage amplitude; The voltage measurements are transformed using coordinates to obtain the α-axis voltage measurements and the β-axis voltage measurements. The first voltage difference between the α-axis voltage amplitude and the α-axis voltage measurement, and the second voltage difference between the β-axis voltage amplitude and the β-axis voltage measurement, are both determined as the virtual impedance voltage drop.

9. The method according to claim 7, wherein, Determining the voltage reference value of the grid-side converter based on the current reference value and the measured current value includes: The current measurement values ​​are transformed by coordinates to obtain the α-axis current measurement value and the β-axis current measurement value; Determine a first current difference between the α-axis current reference value and the α-axis current measurement value, and a second current difference between the β-axis current reference value and the β-axis current measurement value; The first current difference is processed using proportional resonance to obtain the α-axis voltage reference value of the grid-side converter, and the second current difference is processed using proportional resonance to obtain the grid-side voltage reference value. Reference value for the β-axis voltage of the converter.

10. The method according to claim 3 or 4, wherein, The current measurement values ​​include the output current measurement values ​​of the branch where the stator of the grid-type doubly fed wind turbine is located and the output current measurement values ​​of the branch where the grid-side converter is located. The step of determining the voltage reference value of the grid-side converter based on the current reference value and the current measurement value includes: Based on the current reference value and the output current measurement value of the branch where the stator is located, determine the output current reference value of the branch where the grid-side converter is located; The voltage reference value of the grid-side converter is determined based on the output current reference value of the branch where the grid-side converter is located and the measured output current value of the branch where the grid-side converter is located.

11. A control device for a grid-connected doubly-fed induction generator (DFIG), the DFIG comprising a grid-side converter, the device comprising: The acquisition module is used to acquire the internal potential parameters, grid connection point measurement parameters, and virtual impedance reference values ​​of the grid-connected doubly-fed wind turbine generator. The measurement parameters include voltage measurement values ​​and current measurement values. The determining module is used to determine the current reference value of the grid connection point based on the internal potential parameter, the voltage measurement value, and the virtual impedance reference value; The voltage reference value of the grid-side converter is determined based on the current reference value and the current measurement value. The control module is used to control the grid-side converter according to the voltage reference value, so that the difference between the output voltage value of the grid-side converter and the voltage reference value is less than a preset threshold.

12. A computer-readable storage medium having stored thereon computer program instructions that, when executed by a processor, implement the method as described in any one of claims 3-10.

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