Method and device for suppressing shaft torsional vibration of network-constructed doubly-fed wind turbine under variable wind speed

Abstract

The application discloses a method and device for inhibiting shaft torsional vibration of a grid-connected doubly-fed wind turbine under variable wind speed, and a mathematical model of electromagnetic torque-speed difference of the grid-connected doubly-fed wind turbine is constructed; a Bode diagram of electromagnetic torque-speed difference is drawn according to the mathematical model; the natural oscillation frequency of the shaft of the doubly-fed wind turbine is calculated according to mechanical parameters of the wind turbine and the motor, and stability analysis of the damping of the natural oscillation frequency of the shaft is combined with the Bode diagram; a small signal model block diagram is drawn according to the mathematical model; analysis results that the current loop provides a coupling path for the speed and the active power are obtained by analyzing the small signal model block diagram; and the risk of the shaft torsional vibration is reduced by reducing the negative damping caused by the operation area according to the stability analysis results and the analysis results of the small signal model block diagram.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind power generation control, in particular to a method and device for suppressing shaft torsional vibration of grid forming doubly-fed wind turbine under variable wind speed. BACKGROUND

[0002] In recent years, doubly-fed wind power has developed rapidly, and the installed capacity has continued to grow rapidly.

[0003] In order to improve the stability and active support capability of wind power generation system based on doubly-fed induction generator (DFIG) under weak grid operation, the grid forming (GFM) control of DFIG has been widely concerned. The control structure of GFM-DFIG determines that the mechanical and electrical systems have strong coupling in the low frequency range, so it is easy to produce shaft torsional vibration.

[0004] At present, the following researches have been carried out on the shaft torsional vibration of grid forming doubly-fed wind turbine at home and abroad: (1) the grid forming doubly-fed wind turbine is more prone to shaft torsional vibration than grid-connected control due to the low active loop bandwidth; (2) a control strategy of differential feedforward compensation and torque feedback compensation is proposed to suppress the shaft torsional vibration of the grid forming doubly-fed wind turbine; (3) the shaft torsional vibration of the doubly-fed wind turbine using hybrid synchronization control is analyzed, and it is pointed out that the shaft torsional vibration can be suppressed with the increase of the hybrid synchronization coefficient.

[0005] From the above, it can be seen that the above-mentioned researches only analyze the torsional vibration characteristics of the grid forming doubly-fed wind turbine under constant wind speed, and usually introduce dampers to improve the shaft characteristics. However, on the one hand, due to the volatility of wind speed in actual working conditions, the wind turbine will work in different operating regions; on the other hand, the external damping controller will change the performance of the grid forming control. Therefore, under the premise of not changing the performance of the grid forming control, the traditional method is difficult to improve the grid connection stability of the grid forming doubly-fed wind turbine under variable wind speed. SUMMARY

[0006] In view of this, the present application provides a method and device for suppressing shaft torsional vibration of grid forming doubly-fed wind turbine under variable wind speed, which reduces the current loop bandwidth, solves the problem of relatively limited scope of traditional methods, and provides a reference for improving the grid connection stability of grid forming doubly-fed wind turbine.

[0007] According to a first aspect of the embodiments of the present application, a method for suppressing shaft torsional vibration of grid forming doubly-fed wind turbine under variable wind speed is provided, comprising:

[0008] building a mathematical model of electromagnetic torque-speed difference of the grid forming doubly-fed wind turbine;

[0009] drawing a Bode diagram of electromagnetic torque-speed difference according to the mathematical model;

[0010] According to mechanical parameters of the wind turbine and the motor, an inherent oscillation frequency of a shaft system of the doubly-fed wind turbine is calculated, and damping of the inherent oscillation frequency of the shaft system is analyzed in stability in combination with the Bode diagram;

[0011] According to the mathematical model, a small-signal model block diagram is drawn;

[0012] The small-signal model block diagram is analyzed, and an analysis result that the current loop provides a coupling path for the rotational speed and the active power is obtained;

[0013] According to the stability analysis result and the analysis result of the small-signal model block diagram, a negative damping caused by an operating region is weakened by reducing a bandwidth of the current loop, so as to reduce a risk of shaft torsional vibration.

[0014] According to a second aspect of the embodiment of the present application, a device for inhibiting shaft torsional vibration of a grid-connected doubly-fed wind turbine under variable wind speed is provided, and the device comprises:

[0015] A construction module is configured to construct a mathematical model of electromagnetic torque-rotational speed difference of the grid-connected doubly-fed wind turbine;

[0016] A first drawing module is configured to draw a Bode diagram of the electromagnetic torque-rotational speed difference according to the mathematical model;

[0017] A calculation analysis module is configured to calculate an inherent oscillation frequency of a shaft system of the doubly-fed wind turbine according to mechanical parameters of the wind turbine and the motor, and analyze damping of the inherent oscillation frequency of the shaft system in stability in combination with the Bode diagram;

[0018] A second drawing module is configured to draw a small-signal model block diagram according to the mathematical model;

[0019] An analysis module is configured to analyze the small-signal model block diagram, and obtain an analysis result that the current loop provides a coupling path for the rotational speed and the active power;

[0020] An inhibition module is configured to weaken a negative damping caused by an operating region by reducing a bandwidth of the current loop according to the stability analysis result and the analysis result of the small-signal model block diagram, so as to reduce a risk of shaft torsional vibration.

[0021] According to a second aspect of the embodiment of the present application, an electronic device is provided, and the electronic device comprises:

[0022] One or more processors;

[0023] A memory is configured to store one or more programs;

[0024] When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to the first aspect.

[0025] The technical scheme provided by the embodiment of the application can include the following beneficial effects:

[0026] A mathematical model of electromagnetic torque-speed difference of the grid-connected doubly-fed wind turbine is constructed, a Bode diagram of electromagnetic torque-speed difference is drawn according to the mathematical model, the natural oscillation frequency of the shaft system of the doubly-fed wind turbine is calculated according to the mechanical parameters of the wind turbine and the motor, and the damping of the natural oscillation frequency of the shaft system is analyzed in stability according to the Bode diagram, a small signal model block diagram is drawn according to the mathematical model, the analysis result that the current loop provides a coupling path for the speed and active power is obtained by analyzing the small signal model block diagram, and the damping characteristics of the shaft system of the doubly-fed wind turbine in different operating regions are changed by reducing the current loop bandwidth to weaken the negative damping caused by the operating region, so that the risk of shaft torsional vibration is reduced. Since there is a positive and negative difference in the speed loop in different operating regions, the stability of the two operating regions can be considered at the same time, the negative damping generated in the operating region switching process of the grid-connected doubly-fed wind turbine is weakened, and the risk of shaft torsional vibration is reduced.

[0027] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the application. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the application and, together with the specification, serve to explain the principles of the application.

[0029] Figure 1 is a flow chart of a method for inhibiting shaft torsional vibration of a grid-connected doubly-fed wind turbine under variable wind speed according to an exemplary embodiment.

[0030] Figure 2 is a schematic diagram of grid-connected operation of a grid-connected doubly-fed wind turbine provided by an embodiment of the application.

[0031] Figure 3 is a graph of electromagnetic torque-speed difference phase-frequency characteristics corresponding to different operating regions provided by an embodiment of the application.

[0032] Figure 4 is a small signal structure diagram of electromagnetic torque-speed difference of a grid-connected doubly-fed wind turbine provided by an embodiment of the application.

[0033] Figure 5 is a simplified analysis diagram of electromagnetic torque-speed difference small signal provided by an embodiment of the application.

[0034] Figure 6 is a graph of amplitude-frequency characteristics of branch 1 under different current loop bandwidths provided by an embodiment of the application.

[0035] Figure 7is a phase angle difference diagram in different operating regions under different current loop bandwidths provided by an embodiment of the application.

[0036] Figure 8 is a block diagram of a device for suppressing shaft torsional vibration of a grid-connected doubly-fed wind turbine under variable wind speed according to an exemplary embodiment.

[0037] Figure 9 is a block diagram of an electronic device according to an exemplary embodiment. DETAILED DESCRIPTION

[0038] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, the same numbers are used to indicate the same or similar elements, unless otherwise represented. The embodiments described in the following exemplary embodiments are not meant to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the present application as detailed in the appended claims.

[0039] The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in the present application and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0040] Figure 1 is a flow chart of a method for suppressing shaft torsional vibration of a grid-connected doubly-fed wind turbine under variable wind speed according to an exemplary embodiment, as shown in Figure 1 the method can include the following steps:

[0041] S1: constructing a mathematical model of electromagnetic torque-speed difference of the grid-connected doubly-fed wind turbine. This step can include the following sub-steps:

[0042] S11: according to the characteristics of the front-stage wind turbine of the doubly-fed wind turbine, establishing a first small-signal transfer model considering mechanical transmission system link and speed control link;

[0043] Specifically, according to Figure 2 , the first small-signal transfer model is as follows:

[0044] Mechanical transmission system link: ;

[0045] Speed control link: ;

[0046] wherein, Δ represents the small-signal quantity of a variable; H t , H grespectively, are equivalent wind inertia and equivalent motor inertia; T m , T 12 , T e respectively, are wind input mechanical torque, transmission shaft torque and motor input electromagnetic torque; ω t and ω r respectively, are wind rotor speed and generator speed; θ Δ and ω Δ respectively, are angular displacement and speed difference of wind turbine relative to doubly-fed wind turbine rotor; K m and D m are mechanical stiffness coefficient and mechanical damping coefficient; P ref represents active power instruction given value, G7 is speed-power instruction change matrix; k opt represents constant related to wind turbine, ω t0 is wind rotor speed when wind turbine is in steady state; H ω represents speed controller.

[0047] S12: according to electrical control characteristics of doubly-fed wind turbine, a second small signal transfer model considering doubly-fed wind turbine model, voltage outer loop control link and current control inner loop link is established;

[0048] Specifically, according to Figure 2 , the second small signal transfer model is respectively as follows:

[0049] Doubly-fed wind turbine model: ;

[0050] Voltage outer loop control link: ;

[0051] Current inner loop control link: ;

[0052] Wherein, Δ represents small signal quantity of variable; U sdq , I sdq , U rdq , I rdq respectively, are dq axis components of doubly-fed wind turbine stator voltage and current and rotor voltage and current; s is Laplace operator; ω1 is power frequency angular frequency; R s , R r , L s , L r , L m respectively, are stator and rotor resistance, stator and rotor inductance and mutual inductance; ω s is slip angular frequency; ψ rd0 , ψ rd0 respectively, are d-axis and q-axis steady state values of rotor flux; G 0_1 and G 0_2 respectively, are stator current-stator voltage change matrix and rotor current-stator voltage change matrix; G0_3 , G 0_4 , and G 0_5 are stator current-rotor voltage variation matrix, rotor current-rotor voltage variation matrix and speed-rotor voltage variation matrix, respectively; G 2_0 , and G 2_1 are coefficient variation matrix caused by control, respectively, G 2_3 , and G 2_4 are voltage loop and current loop controllers; superscript "ref" represents command value of corresponding variable; θ and E are power synchronization generation angle and voltage loop amplitude given value, respectively; superscript "s" represents variable in actual coordinate system; superscript "c" represents variable in control coordinate system.

[0053] S13: according to the network-constructing type doubly-fed wind turbine topology, a third small signal transfer model of the coordinate transformation link, the power calculation link, the power control link and the power torque link is established;

[0054] Specifically, according to Figure 2 , when the partial control links are linearized, a mathematical model needs to be supplemented so as to make the control equation hold, therefore the third small signal transfer model of the coordinate transformation link, the power calculation link, the power control link and the power torque link is respectively as follows:

[0055] Coordinate transformation link: ;

[0056] Power calculation link: ;

[0057] Power control link: ;

[0058] Power torque model: ;

[0059] Wherein, Δ represents small signal quantity of variable; superscript "s" represents variable in actual coordinate system; superscript "c" represents variable in control coordinate system; X represents stator voltage and rotor voltage current of the doubly-fed wind turbine; θ and E are power synchronization generation angle and voltage loop amplitude given value, respectively; G3 is transformation matrix between system rotating coordinate system and control rotating coordinate system; P e and Q e are stator active power and reactive power, respectively; U sdq , I sdq , are dq axis components of stator voltage and current of the doubly-fed wind turbine, respectively; I sd0 , I sq0 are stator current d-axis and q-axis steady-state values, respectively; U sd0 , U sq0respectively are steady-state values of stator voltage d-axis and q-axis; G4 and G5 are stator voltage-power variation matrix and stator current-power variation matrix; Q ref represents reactive power instruction given value; J and D respectively represent active power inertia and active power damping coefficient of grid forming control; s is Laplace operator; ω1 is power frequency angular frequency; H Q is reactive power controller; T e is electromagnetic torque of motor.

[0060] S14: the three small signal models are combined, and a mathematical model of electromagnetic torque-speed difference of grid forming double-fed wind turbine is obtained by eliminating.

[0061] Specifically, the three small signal models are combined, and a mathematical model of electromagnetic torque-speed difference of grid forming double-fed wind turbine is obtained by eliminating. According to the mathematical model, a small signal model block diagram and a Bode diagram of electromagnetic torque-speed difference are drawn, the natural oscillation frequency of the shaft system of the double-fed wind turbine is intercepted, and the shaft damping is analyzed in combination with the Bode diagram.

[0062] The mathematical model is as follows:

[0063]

[0064] Wherein, ΔT e and Δω Δ are small signal components of electromagnetic torque and speed difference respectively, ω1 is power frequency angular frequency; k is the ratio of equivalent motor inertia and equivalent wind wheel inertia; G7 is speed-power instruction variation matrix; G 0_1 and G 0_2 are stator current-stator voltage variation matrix and rotor current-stator voltage variation matrix respectively; G 0_3 , G 0_4 and G 0_5 are stator current-rotor voltage variation matrix, rotor current-rotor voltage variation matrix and speed-rotor voltage variation matrix respectively; G1 is main circuit variation matrix; G 2_0 and G 2_1 are coefficient variation matrices caused by control, G 2_3 and G 2_4 are voltage loop and current loop controllers; G 3_1 , G 3_2 , G 3_3 are transformation matrices between stator voltage, rotor current and rotor voltage coordinate systems respectively; G4 and G5 are stator voltage-power variation matrix and stator current-power variation matrix.

[0065] S2: according to the mathematical model, a Bode diagram of electromagnetic torque-speed difference is drawn;

[0066] Specifically, Figure 3is the phase-frequency characteristic diagram in the electromagnetic torque versus speed difference Bode diagram corresponding to different operating regions. When the wind speed changes, the speed-power instruction change matrix G7 presents negative gain and positive gain in the maximum power tracking region and the constant speed region, resulting in different phase characteristics of the grid-connected doubly-fed wind turbine at the shaft inherent oscillation frequency in different operating regions, as shown in FIG. 3, thereby causing shaft torsional vibration of the doubly-fed wind turbine. Since the amplitude-frequency characteristic reflects the size of the shaft damping, the phase-frequency characteristic reflects whether the shaft torsional vibration is generated, therefore, for simplifying the analysis, the present example only focuses on the phase-frequency characteristic of the Bode diagram and ignores the amplitude-frequency characteristic. Figure 3

[0067] S3: According to the mechanical parameters of the wind turbine and the motor, the shaft inherent oscillation frequency of the doubly-fed wind turbine is calculated, and the stability of the shaft inherent oscillation frequency is analyzed in combination with the damping of the Bode diagram;

[0068] Specifically, the shaft inherent oscillation frequency is calculated by the following formula:

[0069]

[0070] wherein f is the shaft inherent oscillation frequency; π is the circular constant; K is the mechanical stiffness coefficient; H, H are the equivalent wind wheel inertia and the equivalent motor inertia respectively; and ω1 is the power frequency angular frequency. osc m t g

[0071] When the shaft inherent oscillation frequency is obtained, the corresponding phase is analyzed on the Bode diagram, so that the damping change at the shaft inherent oscillation frequency in different operating regions is analyzed. When the phase is in (90°, 270°), it indicates that the shaft damping is positive; when the phase is in (-90°, 90°), it indicates that the shaft damping is negative.

[0072] S4: According to the mathematical model, a small signal model block diagram is drawn;

[0073] Specifically, Figure 4 is the small signal model block diagram of the electromagnetic torque versus speed difference of the grid-connected doubly-fed wind turbine, and it can be seen from Figure 4 that the current loop provides a coupling path for the speed and the active power, thereby changing the size of the shaft damping. Compared with the mathematical model, through the small signal model block diagram, the influence of the current loop on the shaft damping can be intuitively reflected.

[0074] S5: The small signal model block diagram is analyzed, and an analysis result that the current loop provides a coupling path for the speed and the active power is obtained;

[0075] Specifically, for further analyzing the role of the current loop, Figure 4 the small signal transfer relationship shown in FIG. 6 can be transformed into Figure 5 ​​​​​The shown form. Where branch 1 concerns the influence of the current inner loop on the shaft damping, branch 2 considers the operation area and the effect of the synchronous outer loop on the shaft damping. Figure 6 is the amplitude-frequency characteristic diagram of branch 1 under different current loop bandwidths. With the increase of the current loop bandwidth f c , the gain of branch 1 gradually decreases and can even be ignored, so that the influence of the current loop on the shaft damping disappears. Therefore, with the increase of the current loop bandwidth, Figure 4 can be simplified as branch 2 in Figure 5 . Since changing the operation area will make the G7 element in branch 2 present opposite phase characteristics, from branch 2 of Figure 5 , this will cause the shaft damping of the grid-connected doubly-fed wind turbine to change from positive to negative, thereby causing shaft torsional vibration. Through the above analysis, it can be known that in order to reduce the risk of shaft torsional vibration caused by operation area switching, increasing the current loop bandwidth can increase the total damping of the system.

[0076] S6: According to the stability analysis result and the analysis result of the small signal model block diagram, the negative damping caused by the operation area is weakened by reducing the current loop bandwidth, thereby reducing the risk of shaft torsional vibration.

[0077] Specifically, Figure 7 is a phase angle difference diagram under different operation areas under different current loop bandwidths. With the decrease of the current loop bandwidth, the phase difference θ diff between the electromagnetic torque and the speed difference gradually decreases, weakening the influence of the G7 element, so that the shaft damping of the two operation areas is positive, thereby improving the stability of the grid-connected doubly-fed wind turbine when the operation area switches. For a MW-level wind turbine, the control bandwidth of the current loop generally cannot be less than 100Hz. Therefore, the current loop parameters when the phase angle difference θ diff is 90° are selected in the present example. When the wind speed changes, the operation area switches, and there is a risk of shaft torsional vibration. In order to weaken the negative damping caused by the gain change of the operation area, the current loop bandwidth can be reduced on the basis of ensuring the control performance of the wind turbine, thereby effectively avoiding the shaft torsional vibration caused by the operation area switching.

[0078] Corresponding to the foregoing embodiments of the method for suppressing shaft torsional vibration of the grid-connected doubly-fed wind turbine under variable wind speed, the present application also provides an example of the method for suppressing shaft torsional vibration of the grid-connected doubly-fed wind turbine under variable wind speed.

[0079] Figure 8 is a block diagram of a device for suppressing shaft torsional vibration of a grid-connected doubly-fed wind turbine under variable wind speed according to an example embodiment. The device can include:

[0080] a construction module 1 configured to construct a mathematical model of electromagnetic torque-speed difference of the grid-connected doubly-fed wind turbine;

[0081] The first drawing module 2 is used to draw a Bode plot of electromagnetic torque-speed difference based on the mathematical model.

[0082] The calculation and analysis module 3 is used to calculate the natural oscillation frequency of the shaft system of the doubly fed wind turbine based on the mechanical parameters of the wind turbine and the motor, and to perform stability analysis on the damping of the natural oscillation frequency of the shaft system in combination with the Bode plot.

[0083] The second drawing module 4 is used to draw a small signal model block diagram based on the mathematical model.

[0084] Analysis module 5 is used to analyze the block diagram of the small signal model to obtain the analysis results that the current loop provides a coupling path for the rotational speed and active power;

[0085] Suppression module 6 is used to reduce the risk of shaft torsional vibration by reducing the negative damping in the operating region by decreasing the current loop bandwidth, based on the stability analysis results and the analysis results of the small signal model block diagram.

[0086] Regarding the apparatus in the above embodiments, the specific manner in which each module performs its operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0087] For the device embodiments, since they basically correspond to the method embodiments, the relevant parts can be referred to in the description of the method embodiments. The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this application according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0088] Accordingly, this application also provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; and, when the one or more programs are executed by the one or more processors, causing the one or more processors to implement the method described above for suppressing shaft torsional vibration in a doubly-fed induction generator (DFIG) with variable wind speed. Figure 9 The diagram shown is a hardware structure diagram of any device with data processing capabilities, used in an embodiment of the present invention to suppress shaft torsional vibration in a doubly fed wind turbine with a variable wind speed. (Except for...) Figure 9 In addition to the processor and memory shown, any data processing device in the embodiment may also include other hardware depending on the actual function of the data processing device, which will not be described in detail here.

[0089] Correspondingly, the application further provides a computer readable storage medium, which stores computer instructions, and the instructions are executed by a processor to implement the method for suppressing shaft torsional vibration of a variable-speed network-constructed double-fed wind turbine. The computer readable storage medium can be an internal storage unit of any device with data processing capability, such as a hard disk or a memory. The computer readable storage medium can also be an external storage device, such as a plug-in hard disk, a smart media card (SMC), an SD card, a flash card, etc. Further, the computer readable storage medium can include both the internal storage unit of any device with data processing capability and the external storage device. The computer readable storage medium is used to store the computer program and other programs and data required by the device with data processing capability, and can also be used to temporarily store data that has been output or will be output.

[0090] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

[0091] It should be understood that the application is not limited to the precise construction that has been described above and shown in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The scope of the application is limited only by the appended claims.

Claims

1. A method for suppressing shaft torsional vibration of a variable-speed network-structured doubly-fed wind turbine, characterized in that, The method comprises the following steps: a mathematical model of electromagnetic torque-speed difference of grid-connected doubly-fed wind turbine is constructed; a Bode diagram of electromagnetic torque-speed difference is drawn according to the mathematical model; a natural oscillation frequency of a shafting of the doubly-fed wind turbine is calculated according to mechanical parameters of the wind turbine and the motor, and a stability analysis of damping of the natural oscillation frequency of the shafting is performed in combination with the Bode diagram; a small signal model block diagram is drawn according to the mathematical model; analysis results that the current loop provides a coupling path for the speed and the active power are obtained by analyzing the small signal model block diagram; a risk of shafting torsional vibration is reduced by reducing a negative damping caused by an operating region through reducing a current loop bandwidth according to the stability analysis results and the analysis results of the small signal model block diagram. The mathematical model of electromagnetic torque-speed difference of the grid-connected doubly-fed wind turbine comprises the following steps: a first small signal transfer model considering a mechanical transmission system link and a speed control link is established according to characteristics of a front-stage wind turbine of the doubly-fed wind turbine; a second small signal transfer model considering a doubly-fed wind turbine model, a voltage outer loop control link and a current control inner loop link is established according to electrical control characteristics of the doubly-fed wind turbine; a third small signal transfer model of a coordinate transformation link, a power calculation link, a power control link and a power torque link is established according to a topology of the grid-connected doubly-fed wind turbine; the above three small signal models are solved to obtain the mathematical model of electromagnetic torque-speed difference of the grid-connected doubly-fed wind turbine; the natural oscillation frequency of the shafting of the doubly-fed wind turbine is calculated by the following formula: ； wherein, f osc is the shaft natural oscillation frequency; π is the circle constant; K m is the mechanical stiffness coefficient; H t , H g are the equivalent wind wheel inertia and the equivalent motor inertia, respectively; ω 1 is the power frequency angular frequency.

2. The method of claim 1, wherein, The first small signal transfer model is as follows: Mechanical transmission system element: ; Speed control loop: ; where Δ denotes a small signal of a variable; H t , H g Jw and Jm are equivalent wind wheel inertia and equivalent motor inertia, respectively; T m , T 12 , T e Tw, Tt and Tm are wind wheel input mechanical torque, transmission shaft torque and motor input electromagnetic torque, respectively; ω t and ω r ωw and ωm are wind wheel speed and generator speed, respectively; θ Δ and ω Δ θw and ωd are angular displacement and speed difference of wind turbine relative to doubly-fed wind turbine rotor, respectively; K m and D m K and D are mechanical stiffness coefficient and mechanical damping coefficient, respectively; P ref P* denotes active power command given value, G 7 is speed-power command change matrix; k opt Cw denotes constant related to wind turbine, ω t0 ωwss is wind wheel speed when wind turbine is in steady state operation; H ω ωc denotes speed controller.

3. The method of claim 1, wherein, The second small signal transfer model is as follows: Doubly fed wind turbine model: ; Voltage outer loop control link: ; Current inner loop control element: ; where Δ denotes the small signal quantity of the variable; U sdq 、 I sdq 、 U rdq 、 I rdq are the stator and rotor voltage and current dq axis components of the doubly-fed wind turbine respectively; s is the Laplace operator; ω 1 is the power frequency angular frequency; R s 、 R r 、 L s 、 L r 、 L m are the stator and rotor resistance, inductance and mutual inductance respectively; ω s is the slip angular frequency; ψ rd0 、 ψ rd0 are the rotor flux d axis, q axis steady state values respectively; G 0_1 and G 0_2 are the stator current-stator voltage variation matrix and rotor current-stator voltage variation matrix respectively; G 0_3 、 G 0_4 and G 0_5 are the stator current-rotor voltage variation matrix, rotor current-rotor voltage variation matrix and speed-rotor voltage variation matrix respectively; G 2_0 and G 2_1 are the coefficient variation matrix caused by control respectively, G 2_3 and G 2_4 are the voltage loop and current loop controllers; the superscript ref ” denotes the command value of the corresponding variable; θ and E are the power synchronization generated angle and voltage loop amplitude given value respectively; the superscript s ” denotes the variable in the actual coordinate system; the superscript c ” denotes the variable in the control coordinate system.

4. The method of claim 1, wherein, The third small signal transfer model is as follows: Coordinate transformation block: ; Power calculation block: ; Power control loop: ; Power torque model: ; Where Δ represents the small semaphore of the variable; the superscript " s " indicates a variable in the actual coordinate system; superscript " c " indicates a variable in the control coordinate system; X Represents the stator voltage and rotor voltage and current of a doubly-fed wind turbine; θ and E These are the setpoints for the power synchronization generation angle and voltage loop amplitude, respectively. G 3 represents the transformation matrix between the system rotating coordinate system and the control rotating coordinate system; P e and Q e These are the stator active power and reactive power, respectively. U sdq , I sdq , respectively, are the stator voltage and current of the doubly fed wind turbine. dq Axial components; I sd0 , I sq0 These are the stator currents. d axis, q Shaft steady-state value; U sd0 , U sq0 Stator voltages d axis, q Shaft steady-state value; G 4 and G 5 represents the stator voltage-power variation matrix and the stator current-power variation matrix; Q ref This indicates the given value for the reactive power command; J and D These represent the active inertia and active damping coefficient of the network control system, respectively. s For the Laplace operator; ω 1 represents the power frequency angular frequency; H Q It is a reactive power controller; T e It is the electromagnetic torque of the motor.

5. The method of claim 1, wherein, The mathematical model of electromagnetic torque-speed difference of the grid-connected doubly-fed wind turbine is as follows: ； where Δ T e and Δ ω Δ are small signal components of electromagnetic torque and speed difference, respectively, ω 1 is the power frequency angular frequency; k J is the ratio of equivalent motor inertia and equivalent wind wheel inertia; G 7 is the speed-power command change matrix; G 0_1 and G 0_2 are stator current-stator voltage change matrix and rotor current-stator voltage change matrix, respectively; G 0_3 , G 0_4 and G 0_5 are stator current-rotor voltage change matrix, rotor current-rotor voltage change matrix and speed-rotor voltage change matrix, respectively; G 1 is the main circuit change matrix; G 2_0 and G 2_1 are coefficient change matrices caused by control, respectively, G 2_3 and G 2_4 are voltage loop and current loop controllers; G 3_1 , G 3_2 , G 3_3 are transformation matrices between stator voltage, rotor current and rotor voltage coordinate systems, respectively; G 4 and G 5 are stator voltage-power change matrix and stator current-power change matrix.

6. The method of claim 1, wherein, The small signal model block diagram including the transmission system, the speed loop, the synchronous outer loop and the current inner loop is drawn according to the mathematical model.

7. A device for suppressing shaft torsional vibration of a variable-speed network-configuration doubly-fed wind turbine, characterized in that, The device is used to execute the method of claim 1, and the device comprises: a construction module configured to construct a mathematical model of electromagnetic torque-speed difference of a grid-connected doubly-fed wind turbine; a first drawing module configured to draw a Bode diagram of electromagnetic torque-speed difference according to the mathematical model; a calculation and analysis module configured to calculate a natural oscillation frequency of a shafting of the doubly-fed wind turbine according to mechanical parameters of a wind turbine and a motor, and perform a stability analysis of damping of the natural oscillation frequency of the shafting in combination with the Bode diagram; a second drawing module configured to draw a small signal model block diagram according to the mathematical model; an analysis module configured to obtain analysis results that a current loop provides a coupling path for a speed and an active power by analyzing the small signal model block diagram; a suppression module configured to reduce a risk of shafting torsional vibration by reducing a negative damping caused by an operating region through reducing a current loop bandwidth according to the stability analysis results and the analysis results of the small signal model block diagram.

8. An electronic device, comprising: The device comprises: one or more processors; a memory configured to store one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the method of any one of claims 1-6.

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