Method and apparatus for controlling a wind turbine converter

Abstract

A method of controlling a converter (13), in particular a converter of a wind turbine (1), the converter comprising a first converter part (15) connected to a generator (9), a DC link (17) and a second converter part (19) connected to a utility grid, the method comprising: controlling the first converter part (15) and the second converter part (17) by a first control signal (113) and a second control signal (115), respectively, the first control signal (113) and the second control signal (115) both being derived based on a requested power signal (105) and a generator speed (107), in particular the requested power signal (105) being a requested active power signal, wherein the first control signal (113) indicates a substantially constant generator torque for a speed change of the generator speed (107) above a frequency threshold.

Description

Technical Field

[0001] This invention relates to a method and apparatus for controlling a converter having a generator converter section and a public grid converter section. Further, this invention relates to a generator system and even more particularly to a wind turbine. Background Technology

[0002] Traditionally, a converter is connected between the generator and the output terminals of a wind turbine to convert a variable-frequency AC power flow into a substantially fixed-frequency AC power flow. The wind turbine's output terminals may be connected to a common junction point to which multiple other wind turbines are connected, and optionally to a utility grid that supplies electricity to multiple consumers via one or more wind farm transformers. Traditionally, the power flow supplied to or exchanged with the utility grid requires control regarding electrical properties such as power flow rate, voltage phase angle, etc. Because the configuration of a traditional converter consists of a generator section, a DC link, and a utility grid section, there are design options for how to control the converter.

[0003] Traditionally, the converter receives a power demand signal from the wind turbine controller. This power demand signal can then be used directly in the grid converter section, which delivers the required power to the utility grid. Similarly, the generator converter section can also receive the same power demand signal in a conventional system. A correction power, such as that derived from a DC link voltage controller, can be added to this power demand. The generator converter section can then control the generator power to this combined value. Therefore, conventionally, in a steady state, both the grid converter power signal and the generator converter power signal are equal to the required value (ignoring losses), and the DC link voltage is at the required voltage value. A further conventional variant may control the generator torque instead of its power.

[0004] When the conventional generator power is kept constant at a still-changing generator speed, this may not be optimal for damping mechanical resonance.

[0005] Therefore, the technical problem solved by the present invention can be regarded as providing a control method and a corresponding control device that can control a converter including a generator side section and a public power grid section in order to effectively reduce mechanical vibration, reduce speed ripple and / or load on components of the generator and / or drive system, and / or improve the efficiency and performance of power generation.

[0006] This problem is solved by embodiments of the present invention. Summary of the Invention

[0007] According to an embodiment of the present invention, a method for controlling a converter, particularly a converter for a wind turbine, is provided, the converter comprising a first (e.g., generator-side) converter section connected to a generator, a DC link, and a second (e.g., grid-side) converter section connected to a public power grid, the method comprising controlling the first converter section and the second converter section respectively via a first control signal and a second control signal, both the first control signal and the second control signal being derived based on a requested power signal and a generator speed, particularly, the requested power signal being a requested active power signal, wherein the first control signal indicates a substantially constant generator torque for a change in generator speed above a frequency threshold.

[0008] This method can be performed by a device for controlling a converter according to an embodiment of the present invention, and in particular, by a wind turbine controller.

[0009] The generator speed can be measured or estimated, for example, based on generator current and voltage derived from a "speed observer". Therefore, physical measurement of speed is not necessary.

[0010] The first converter section can also be referred to as the generator-side converter section, and the second converter section can also be referred to as the grid converter section. Each converter section may include multiple controllable switches, such as IGBTs, where, for example, for each phase (e.g., a total of three phases may be supported), two of the controllable switches may be connected in series (other converter topologies are possible). The on-state of the controllable switches may be controlled by a pulse-width modulated signal. In particular, the first converter section may include or may be an AC-DC converter section capable of converting a (variable) frequency AC power flow into a substantially DC power flow that can exist at a DC link. The grid converter section or the second converter section may be capable of converting a DC power flow into a fixed frequency (e.g., 50 Hz or 60 Hz) power flow. The power flow or power output from the second converter section may be further transformed to a higher voltage by a transformer, this transformation occurring before the transformed power flow is supplied to a common coupling point to which multiple other wind turbines or other generators are connected.

[0011] The first and second control signals can, for example, define reference values, such as active power, current, and torque corresponding to desired values ​​at the output terminals of the respective converter sections or generators. The corresponding first and second control signals can be supplied to controllers. The outputs of these controllers may then be supplied to one or more gate driver circuits, which generate pulse-width modulated signals from those control signals for the gates of controllable switches in the first and second converter sections, respectively. For example, a space vector modulation scheme can be applied. The first and second control signals can be implemented as electrical and / or optical signals.

[0012] For example, the (software) controller can receive a first and / or a second control signal and can output the required converter AC terminal voltage (for the generator bridge or network bridge, respectively). The AC terminal voltage requirement signal can be received at a PWM mode generator that derives the switching mode required to achieve the terminal voltage, and the switching mode can be supplied to the gate driver.

[0013] The requested power signal can be, or may correspond to, a reference power expected to be output by the generator or converter. Specifically, the generator can be implemented as a permanent magnet synchronous machine, such as a three-phase permanent magnet motor. The generator may include a stator providing the entire perimeter and having one (e.g., three-phase) winding set, or may include two or more stator segments, each providing a section of the entire perimeter, such as 180°, 90°, 60°, etc., and each stator segment having one (e.g., three-phase) winding set. Each of the potential plurality of winding sets may be connected to a corresponding associated first converter section.

[0014] The requested power signal can be received, for example, from a wind farm controller or an operator of the utility grid. The requested power signal can define the requested active power.

[0015] The first control signal can directly define the desired generator torque, or it can indicate, for example, a signal related to the generator torque, such as a current signal, in particular, an active current signal.

[0016] During generator operation, the generator speed can vary. This variation in generator speed can, for example, include variations at different frequencies. The time-varying generator speed can have different frequency components. These different frequency components can be obtained, for example, by applying a Fourier transform to the generator speed as observed over time. Very rapid changes in generator speed then correspond to high-frequency components, and slow changes in generator speed correspond to low-frequency components. In this application, the high-frequency components of the generator speed variation can, for example, be referred to as those frequency components having frequencies above a frequency threshold. The low-frequency components of the generator speed variation can be referred to as those frequency components of the speed variation below a frequency threshold.

[0017] When there is a (at least substantially) constant generator torque for generator speed variations above a frequency threshold, mechanical oscillations can be effectively reduced. Furthermore, efficiency can be improved and load can be reduced.

[0018] The first converter section is connected to the generator. Controlling the first converter section allows control over the power and current generated by the generator. When the generator torque is substantially constant, especially when the variation is less than 5% or less than 1% (for a constant requested power signal), the load or wear on generator components or transmission components may be reduced. When the generator torque is substantially constant with respect to the high-frequency component of the speed variation, the output power can vary according to the speed variation.

[0019] In the context of this application, the first converter section may also be referred to as a generator bridge, and the second converter section may also be referred to as a network bridge.

[0020] According to an embodiment of the present invention, the first control signal defines an active current demand value for the first converter section, and / or the second control signal defines a power demand value or active current demand value for the second converter section, and / or wherein the frequency threshold is in the range between 0.01 Hz and 1 Hz, particularly in the range between 0.1 Hz and 1 Hz.

[0021] When the first control signal defines the active current demand value for the first converter section, conventionally applied control schemes can be used to implement the control method upon modification. Furthermore, when the second control signal defines the power demand value or active current demand value, conventionally known algorithms can also be employed and modified to implement the control method.

[0022] The generator speed can correspond to the mechanical speed of the rotor rotating within the generator. In other embodiments, the generator speed can correspond to an electrical speed proportional to the rotor speed. Thus, this embodiment of the invention can be implemented using conventionally known control schemes.

[0023] According to an embodiment of the present invention, the first control signal indicates the generator torque that varies with respect to speed changes below the frequency threshold, and in particular, indicates the generator torque that varies according to the speed changes.

[0024] When the generator torque varies with respect to the low-frequency component of the generator speed, the excitation of mechanical vibration can be less than that at the high-frequency component. Furthermore, by varying the generator torque, the output power can be made substantially constant with respect to speed variations below a frequency threshold, thus more closely satisfying the requested power signal.

[0025] According to an embodiment of the present invention, the second control signal and / or the power demand value for the second converter portion varies with respect to rotational speed changes above the frequency threshold. In particular, the second control signal and / or the power demand value varies with respect to rotational speed changes above the frequency threshold and according to the rotational speed changes.

[0026] As the rotational speed changes, the first control signal can become more constant or less constant, while the second control signal can change as the rotational speed changes.

[0027] In particular, compatible control signals can be used to control both generator sections, so that the converter sections do not interfere with each other.

[0028] According to an embodiment of the present invention, the second control signal and / or the power demand value for the second converter section are substantially constant with respect to rotational speed variations below the frequency threshold.

[0029] At low frequencies, depending on the requested power signal, the second control signal and / or the power demand value for the second converter section can be substantially constant.

[0030] According to an embodiment of the present invention, the DC link is controlled by a DC link controller for a constant DC voltage. The DC link controller can thus control the input voltage, i.e., the DC voltage, for the second converter section. Therefore, it can be ensured that the output voltage of the second converter section is within the desired range.

[0031] According to an embodiment of the present invention, the DC link controller generates a power modification signal in response to a DC voltage error. The DC link controller may include, for example, a PI or PID controller that receives the DC voltage error (the difference between the measured DC voltage and a reference DC voltage) and derives the power modification signal based on the DC voltage error, such that the DC voltage error is reduced more and more, ideally reaching 0.

[0032] According to an embodiment of the present invention, the method further includes determining the second control signal, which includes: receiving a requested power value; performing a low-pass filter on the generator speed; dividing the generator speed by the filtered generator speed to obtain a division signal; and multiplying the requested power signal with a signal derived based on the division signal to obtain the second control signal.

[0033] Low-pass filtering of the generator speed can be performed using a low-pass filter with an appropriately set frequency threshold. The filtered generator speed may have no or only a reduced amplitude of the high-frequency component of the speed change. For the high-frequency component of the speed change, the division signal can be greater than 0, and for the low-frequency component of the speed change, the division signal can be equal to 1. Therefore, the second control signal can periodically change between being greater than and less than the requested power for the high-frequency component, and can be equal to the requested power for the low-frequency component of the speed change.

[0034] The second control signal can vary at a higher frequency as the speed changes, thus tending to vary around the value 1.

[0035] Therefore, in a high-frequency system, the power demand of the public grid (a specific implementation of the second control signal) can vary with the generator speed. However, this allows the generator torque to be kept substantially constant.

[0036] According to an embodiment of the present invention, the signal derived based on the division signal is obtained by one of the following: the division signal; by applying a compensation filter to the division signal, in particular, compensating for the phase error and / or gain error of the observed (estimated) rotational speed signal and / or the common bridge power transfer function.

[0037] Compensation filters can be provided primarily to compensate for velocity observer gain / phase errors and network bridge power transfer functions.

[0038] The compensation filter, also known as a lead / lag filter, can take low-pass filtered active power, low-pass filtered reactive power, and low-pass filtered generator speed as inputs. The input values ​​can define corresponding operating points. Therefore, it can address and account for speed estimation gain / phase errors and power transfer function gain / phase errors of the grid (network bridge).

[0039] According to embodiments of the present invention, the compensation filter is tuned based on the corresponding operating points of the first converter section and / or the second converter section and / or the generator and / or the utility power grid. Therefore, the method can be further improved and measurement-related errors or phase shifts can be reduced.

[0040] According to an embodiment of the present invention, the method further includes determining the first control signal, which includes: receiving a requested power signal; adding the requested power value to the power modification signal (output by the DC controller) to obtain a generator power demand signal; performing a low-pass filter on the generator speed; multiplying the filtered generator speed by a (stator) flux signal associated with the magnetic flux of the generator to obtain a generator anti-EMF signal; and dividing the generator power demand value by the generator anti-EMF signal to obtain the first control signal.

[0041] Thus, the first control signal can be obtained in a simple manner. The flux signal can correspond to the magnetic flux of the generator, which can be due to a permanent magnet or a magnetic field generated by the windings of the generator stator. The flux can be measured or determined, for example, by calculation based on other known or measured quantities (such as current, voltage, inductance, etc.).

[0042] An estimate of the actual generator flux can be derived from voltage and current measurements, as well as some knowledge of generator parameters (such as inductance and resistance).

[0043] According to an embodiment of the present invention, the first control signal and / or the second control signal indicate the power variation for speed variations above the frequency threshold, in particular, indicate the power variation for speed variations above the frequency threshold; and / or wherein the second control signal indicates a substantially constant torque for speed variations above the frequency threshold.

[0044] Because the power varies at a relatively high frequency, the deviation from the requested power can also have a relatively high frequency, thus not significantly disturbing the power output.

[0045] It should be understood that features disclosed, described, applied, or interpreted individually or in any combination in the context of a method for controlling a converter may also be applied individually or in any combination to an apparatus for controlling a converter according to embodiments of the present invention, and vice versa.

[0046] According to an embodiment of the present invention, an apparatus is provided for controlling a converter, particularly a converter for a wind turbine, the converter comprising a first (e.g., generator-side) converter section connected to a generator, a DC link, and a second (e.g., grid-side) converter section connected to a public power grid, the apparatus comprising: an input section for receiving an input signal including a requested power signal, particularly a requested active power signal, and an input signal (estimated, observed, or measured) generator speed; and a control section adapted to control the first converter section and the second converter section respectively by a first control signal and a second control signal derived based on the input signal, wherein the first control signal indicates a substantially constant generator torque for changes in the generator speed above a frequency threshold.

[0047] Furthermore, according to an embodiment, a generator system is provided, comprising: a generator; a converter including a first converter section connected to the generator, a DC link, and a second converter section connectable to a public power grid; and an apparatus according to a previous embodiment, connected to control the converter.

[0048] Furthermore, according to an embodiment of the present invention, a wind turbine is provided, comprising: a rotor shaft, wherein a plurality of blades are mounted on the rotor shaft; and a generator system according to a previous embodiment.

[0049] The aspects and further aspects of the invention defined above will become apparent from the examples of the embodiments described below, and will be explained with reference to these examples. The invention will now be described in more detail with reference to examples of embodiments, but the invention is not limited to these examples. Attached Figure Description

[0050] Embodiments of the present invention will now be described with reference to the accompanying drawings. The present invention is not limited to the embodiments illustrated or described.

[0051] Figure 1 A wind turbine according to an embodiment of the present invention is schematically illustrated, including a device according to an embodiment of the present invention; Figure 2 The illustration schematically depicts an apparatus for controlling a converter according to an embodiment of the present invention; and Figure 3 An apparatus for controlling a converter according to another embodiment of the present invention is schematically illustrated. Detailed Implementation

[0052] The illustrations in the accompanying drawings are for illustrative purposes only. It should be noted that similar or identical elements are provided with the same reference numerals in different drawings, or reference numerals that differ from the corresponding reference numerals only in the first digit.

[0053] Figure 1 The wind turbine 1, schematically illustrated, includes a shaft 3 with a hub 5, on which multiple rotor blades 7 are mounted. The rotor shaft 3 rotates within a generator 9 that outputs a three-phase (or a different number of phases) power flow 11. The generator 9 can be a single-channel, dual-channel, or multi-channel generator, each channel of which may have an associated converter. The output terminals of the generator 9 are connected to a converter 13, which includes a (first) generator-side section 15, a DC link 17, and a (second) utility grid section 19. The utility grid converter section 19 outputs a three-phase power signal 21, which can be supplied, for example, via a transformer to a common coupling point, which in turn is connected to the utility grid.

[0054] The converter 13 is controlled by a device 100 for controlling the converter according to an embodiment of the present invention. Further, the generator 9, the converter 13, and the device 100 form a generator system according to an embodiment of the present invention, which is labeled with reference numeral 25.

[0055] The device 100 includes an input section formed by input terminals 101 and 103 for receiving input signals including a requested power signal 105 and a generator speed 107 measured by a measuring sensor 109. In other embodiments, the measuring sensor 109 is implemented by means of an observer that indirectly derives the speed from the measured electrical quantity. The requested power signal 105 may be supplied, for example, from a wind farm controller. Based on the input signals 105 and 107, the device 100 uses a control section 111 to derive a first control signal 113 and output the first control signal 113 to a first portion 15 of a converter 13, and to derive a second control signal 115 and output the second control signal 115 to a second converter portion 19 of the converter 13. The control signals 113 and 115 may define reference values, such as those relating to active power, reactive power, current, and torque, which are then used by a controller whose output is a pulse-modulated signal for a plurality of controllable switches within the first converter portion 15 and the second converter portion 19. Thus, the first control signal 113 indicates a substantially constant generator torque for changes in the rotational speed of the generator 9 above a frequency threshold.

[0056] Figure 1 The apparatus 100, illustrated schematically, is capable of implementing or performing the method of controlling a converter according to an embodiment of the present invention.

[0057] Figure 2 A control converter device 200 according to an embodiment of the present invention is schematically illustrated. The device 200 can be used, for example, as a control converter device. Figure 1 The device 100 shown in the figure.

[0058] It should be noted that Figures 1 to 3 Elements that are similar in structure and / or function are labeled with reference numerals that differ only in the first digit. Descriptions of specific elements not referred to in a particular drawing may be derived from descriptions in another drawing or another embodiment.

[0059] The generator speed 107 is received at input terminal 203, and the requested power signal 105 is received at input terminal 201. The generator speed 207 is filtered using a low-pass filter 217 to remove high-frequency components, and the generator speed 207 is obtained as a filtered generator speed signal 219.

[0060] The filtered generator speed 219 is multiplied by the flux signal 221 associated with the magnetic flux of the generator 9 to obtain the generator inverse EMF signal 223. Thus, the multiplication is performed using the multiplication element 225.

[0061] Using the division element 227, the generator power demand value 229 is divided by the generator reverse EMF signal 223 to obtain the first control signal 213, which is specifically the generator active current demand value or signal.

[0062] Furthermore, the requested power signal 205 is received and added to the power modification signal 233 using the adder element 231 to obtain the generator power demand signal 229. The power modification signal 233 is generated using the DC link controller 235 that receives the DC voltage error signal 237.

[0063] To generate the second control signal 215, the generator speed 207 is divided by the filtered generator speed 219 using a division element 239 to obtain a division signal 241. The requested power signal 205 is multiplied by a signal 245 derived from the division signal 241 using a multiplication element 243 to obtain the second control signal 215. Figure 2 In the embodiment illustrated in the figure, signal 245 derived from the division signal is equal to the division signal 241.

[0064] However, in alternative embodiments, such as Figure 3 As illustrated, a signal 345 derived from the division signal 341 is generated by applying a compensation filter 347 to the division signal 341. Thus, the compensation filter 347 is tuned depending on the input signals (e.g., related to the operating points of the first converter section 15 and the second converter section 19). In the illustrated embodiment, the compensation filter 247 receives low-pass filtered grid power 349, low-pass filtered grid reactive power 351, and low-pass filtered observed speed 319.

[0065] According to an embodiment of the invention, the DC link controller output signal affects the first converter section, namely, the generator-side converter section. The generator torque can be kept relatively constant even in the presence of speed variations. According to an embodiment of the invention, the DC link controller 235 is located at the generator bridge. The external demand signal 205 may include a power demand signal. The common converter section 19 can be controlled by a controller that operates in a manner that keeps the torque substantially constant, wherein the power may intentionally deviate from the demand in response to speed fluctuations. The generator-side converter section 15 can be controlled to attempt to keep the torque also constant. As the generator speed changes, the generator power can change in phase with the speed (i.e., the torque tends to be kept relatively constant) (for frequencies above a frequency threshold), which may tend to reduce mechanical resonance.

[0066] If possible Figure 2 and 3 As obtained, in order to calculate the generator active current demand (e.g., Figure 2 and 3 The first control signals 213 and 313 (illustrated in the diagram) divide the generator power demand signal 229 by the generator anti-EMF signals 223 and 323. By including filters 217 and 317 in the speed signal 207 used to calculate the generator anti-EMF 223, this tends to reject speed fluctuations from the generator active current demand; that is, it tends to keep the generator active current relatively constant even in the presence of speed fluctuations. Since the generator active current can be closely related to the generator torque, this may introduce the property of tending to keep the generator torque relatively constant even in the presence of speed fluctuations.

[0067] According to embodiments of the present invention, constant torque characteristics are created at frequencies above the cutoff frequency (e.g., frequency threshold) of low-pass filters 217 and 317, and constant power characteristics are created at frequencies below the cutoff frequency (e.g., frequency threshold) of low-pass filters 217 and 317.

[0068] If the only modification is to the generator-side converter section, then the network and generator bridge will have mismatch control objectives. The network bridge will want to maintain constant power in the presence of speed fluctuations, while the generator bridge will want power to vary in response to speed fluctuations. The resulting power mismatch in these two different converter sections (or bridges) will cause a DC link voltage error, and based on this voltage error, the DC link controller will modify the generator power demand. In doing so, this additional power demand will come into play to counteract the constant torque class characteristics introduced in the generator converter section.

[0069] To avoid this problem, the network bridge power requirements are modified in response to speed fluctuations, such as... Figure 2 and 3 As shown in the diagram. In alternative implementations (with similar or identical behavior), the downstream net active current demand can be modified instead of the net power demand. By closely matching the way both the network and the generator bridge modify the power (compared to the externally requested value) in the presence of speed fluctuations, this tends to prevent voltage errors from being observed in the DC link at frequencies where speed fluctuations occur, and thus tends to prevent the DC link controller from creating unwanted modifications to the generator power demand at frequencies where speed fluctuations occur.

[0070] Therefore, according to embodiments of the present invention, speed disturbances at frequencies above the cutoff frequencies of low-pass filters 217 and 317 can generally achieve characteristics close to the desired constant torque. At all frequencies of the speed disturbance, the power in both the network bridge and the generator bridge can be very similar, resulting in inherently good control of the DC link voltage.

[0071] exist Figure 3 In the alternative embodiment 300 illustrated in the middle, an additional filter 347 is introduced in the power demand calculation path to the network bridge to potentially further enhance performance. This filter 347 can be adaptively tuned as a function of the operating point of the network bridge and / or generator bridge, and can compensate for gain and / or phase introduced into the observed speed and / or network bridge power transfer function.

[0072] According to embodiments of the invention, as the generator speed fluctuates (particularly with frequency components for high frequencies), the network bridge power requirements are modified to create (substantially) constant torque characteristics. Further, according to embodiments of the invention, as the generator speed fluctuates, the generator bridge current requirements can be modified to create constant torque characteristics. A DC link controller can be associated with the generator bridge.

[0073] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude multiple. Elements described in association with different embodiments may also be combined. It should also be noted that the reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method for controlling a converter (13), the converter comprising a first converter section (15) connected to a generator (9), a DC link (17), and a second converter section (19) connected to a public power grid, the method comprising: The first converter section (15) and the second converter section are controlled by a first control signal (113) and a second control signal (115), respectively. Both the first control signal (113) and the second control signal (115) are derived based on the requested power signal (105) and the generator speed (107). The first control signal (113) indicates a substantially constant generator torque for changes in generator speed (107) above a frequency threshold.

2. The method according to claim 1, wherein the converter (13) is a converter of the wind turbine (1).

3. The method according to claim 1, wherein the requested power signal (105) is the requested active power signal.

4. The method according to claim 1, Wherein the first control signal (113) defines the active current demand value for the first converter section (15), and / or The second control signal (115) defines the power demand value or active current demand value for the second converter section (19), and / or The frequency threshold is in the range of 0.01 Hz to 1 Hz.

5. The method of claim 4, wherein the frequency threshold is in the range between 0.1 Hz and 1 Hz.

6. The method according to any one of claims 1 to 5, wherein the first control signal (113) indicates the generator torque for changes in rotational speed below the frequency threshold.

7. The method according to claim 6, wherein the first control signal (113) indicates the generator torque that varies according to the speed change.

8. The method according to any one of claims 1 to 5, wherein the second control signal (115) and / or the power demand value for the second converter section (19) varies with respect to rotational speed changes above the frequency threshold.

9. The method of claim 8, wherein the second control signal and / or power demand value varies according to the speed change for speed changes above the frequency threshold.

10. The method according to any one of claims 1 to 5, wherein the second control signal (115) and / or the power demand value for the second converter section (19) is substantially constant with respect to rotational speed changes below the frequency threshold.

11. The method according to any one of claims 1 to 5, wherein the DC link (17) is controlled by a DC link controller (235) for a constant DC voltage.

12. The method of claim 11, wherein the DC link controller (235) generates a power modification signal (233) in response to a DC voltage error (237).

13. The method according to any one of claims 1 to 5, further comprising determining the second control signal (215), which includes: Receive the requested power value (205); The generator speed (207) is low-pass filtered; Divide the generator speed (207) by the filtered generator speed (219) to obtain the division signal (241). as well as The requested power signal (205) is multiplied by the signal (245) derived based on the division signal (241) to obtain the second control signal (215).

14. The method of claim 13, wherein the signal (245) derived based on the division signal (241) is obtained by one of the following: The division signal; The compensation filter (347) is applied to the division signal (241).

15. The method of claim 14, wherein the application of the compensation filter (347) includes compensating for the rotational speed estimation phase error and / or gain error and / or the power transfer function gain and / or phase error of the utility grid.

16. The method of claim 14, wherein the compensation filter (347) is tuned depending on the corresponding operating point of the first converter section (15) and / or the second converter section (19) and / or the generator (9) and / or the utility power grid.

17. The method of claim 16, further comprising determining the first control signal (213), comprising: Receive the requested power signal (205); The requested power value (205) is added to the power modification signal (233) to obtain the generator power demand signal (229). The generator speed (207) is low-pass filtered; The filtered generator speed is multiplied by the flux signal (221) associated with the magnetic flux of the generator to obtain the generator inverse EMF signal (223). Divide the generator power demand value (229) by the generator anti-EMF signal (223) to obtain the first control signal (213).

18. The method according to claim 17, Wherein the first control signal (113) and / or the second control signal (115) indicate the power change for a change in rotational speed above the frequency threshold; and / or The second control signal (115) indicates a substantially constant torque for speed variations above the frequency threshold.

19. The method of claim 18, wherein the first control signal (113) and / or the second control signal (115) indicate a change in power based on a rotational speed variation above the frequency threshold.

20. A device (100) for controlling a converter (13), the converter including a first converter section (15) connectable to a generator (9), a DC link (17), and a second converter section (19) connectable to a public power grid, the device comprising: The input units (101, 103) are used to receive an input signal including the requested power signal (105) and the measured or estimated generator speed (103); The control unit (111) is adapted to control the first converter section (15) and the second converter section (19) respectively by a first control signal (113) and a second control signal (115) derived based on the input signal. The first control signal (113) indicates a substantially constant generator torque for changes in the generator speed above a frequency threshold.

21. The apparatus (100) according to claim 20, wherein the converter (13) is a converter of the wind turbine (1).

22. The apparatus (100) according to claim 20, wherein the requested power signal (105) is the requested active power signal.

23. A generator system (25), comprising: Generator (9); The converter (13) includes a first converter section (15) connected to the generator (9), a DC link (17), and a second converter section (19) connectable to the public power grid; and The device (100) according to any one of claims 20 to 22 is connected to control the converter (13).

24. A wind turbine (1), comprising: Rotor shaft (3), multiple blades are mounted on said rotor shaft (3); as well as The generator system (25) according to claim 23.

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