Low frequency damping torque modeling method and system for grid-connected doubly-fed wind power system
Patent Information
- Application Number
- CN202611416129.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-14
- Publication Date
- 2026-10-30
AI Technical Summary
[0005]本发明提供一种构网双馈风电并网系统的低频阻尼转矩建模方法和系统，旨在解决现有技术中难以对构网型双馈风机在弱电网下的低频阻尼特性及振荡风险进行有效建模和量化分析的技术问题
通过将复杂的构网双馈风电并网系统分解为物理意义清晰的等效机械子系统和等效电气子系统，简化了分析模型，能够清晰地揭示构网控制中的有功同步环节与系统其余电气部分之间的相互作用关系，为理解低频振荡机理提供了明确的物理视角。进一步，通过推导与频率相关的弹性系数模型和阻尼系数模型，能够精确定位系统发生机电耦合振荡的扭振频率点，并进一步计算出该频率点上的净阻尼，从而实现了对系统低频阻尼特性的量化评估，相比于传统的时域仿真或特征值分析，本方法更为直观和深刻。最后，基于计算出的净阻尼值，能够直接、可靠地判断系统的小扰动稳定性，并量化稳定裕度。净阻尼为负值预示着系统存在低频振荡失稳风险，其对应的扭振频率即为振荡频率。这种量化分析结果能够为风机控制参数（如虚拟同步发电机的虚拟惯量和阻尼系数）的优化设计提供明确的指导，以主动增强系统阻尼，抑制低频振荡，提升系统在弱电网下的稳定运行能力。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of power system technology, and in particular to a low-frequency damping torque modeling method and system for a grid-connected doubly fed wind power system. Background Technology
[0002] As wind power penetration in power systems continues to increase, modern power systems are gradually exhibiting characteristics of weak damping and low inertia. Wind turbines are typically connected to the end of the grid, where the grid strength at the connection point is relatively weak, i.e., a weak grid scenario with a low short-circuit ratio (SCR).
[0003] To improve the adaptability of traditional grid-connected doubly-fed induction generator (DFIG) wind turbines in weak grid environments, grid-connected control technologies (such as virtual synchronous generator control) are applied to DFIGs, enabling them to simulate the characteristics of a synchronous generator and present themselves as a voltage source to improve grid connection stability. However, in weak grid scenarios, the complex interactions between the control system of the grid-connected wind turbine, the power grid, and the induction motor shaft system may introduce negative electrical damping. Under certain conditions, this negative damping can cause low-frequency oscillations in the system, and in severe cases, even lead to oscillation instability, threatening the safe and stable operation of the system.
[0004] Therefore, the existing technology lacks a method to effectively model and quantify the low-frequency damping characteristics of grid-connected doubly-fed wind turbines, making it difficult to accurately explore and evaluate the intrinsic mechanism and influencing factors of low-frequency oscillations generated by doubly-fed wind turbines in weak grid scenarios, which poses a challenge to the optimization design of wind turbine control parameters. Summary of the Invention
[0005] This invention provides a low-frequency damping torque modeling method and system for grid-connected doubly fed wind power systems, aiming to solve the technical problem that it is difficult to effectively model and quantify the low-frequency damping characteristics and oscillation risk of grid-connected doubly fed wind turbines under weak power grids in the prior art.
[0006] This invention provides a low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system, comprising: Construct a small-signal state-space model of a grid-connected system for a doubly fed wind turbine; The small-signal state-space model is decomposed into a set of small-signal state-space equations for an equivalent mechanical subsystem and an equivalent electrical subsystem; wherein, the equivalent mechanical subsystem is composed of the active power synchronization element of the grid-type doubly-fed wind turbine; Based on the small-signal state-space equations, the frequency-dependent elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and the equivalent electrical subsystem are derived. Based on the elastic coefficient model, the torsional vibration frequency point of the grid-connected system is determined. The torsional vibration frequency point is the frequency at which the sum of the elastic coefficient of the equivalent mechanical subsystem and the elastic coefficient of the equivalent electrical subsystem is zero. Based on the damping coefficient model, the sum of the damping coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem at the torsional vibration frequency point is calculated to obtain the net damping of the grid-connected system.
[0007] This invention also provides a low-frequency damping torque modeling system for a grid-connected doubly-fed induction generator (DFIG) wind power system, comprising: The model building module is used to build a small-signal state-space model of the grid-connected system of a grid-connected doubly-fed wind turbine; The model decomposition module is used to decompose the small-signal state-space model into a set of small-signal state-space equations for an equivalent mechanical subsystem and an equivalent electrical subsystem; wherein, the equivalent mechanical subsystem is composed of the active power synchronization element of the grid-type doubly-fed wind turbine; The model derivation module is used to derive the frequency-dependent elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and the equivalent electrical subsystem based on the small-signal state-space equation set. The torsional vibration determination module is used to determine the torsional vibration frequency point of the grid-connected system based on the elastic coefficient model. The torsional vibration frequency point is the frequency at which the sum of the elastic coefficient of the equivalent mechanical subsystem and the elastic coefficient of the equivalent electrical subsystem is zero. The damping calculation module is used to calculate the sum of the damping coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem at the torsional vibration frequency point based on the damping coefficient model, so as to obtain the net damping of the grid-connected system.
[0008] The present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the low-frequency damping torque modeling method for a grid-connected doubly fed wind power system as described above.
[0009] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the low-frequency damping torque modeling method for a grid-connected doubly fed wind power system as described above.
[0010] Compared with existing technologies, the low-frequency damping torque modeling method and system for grid-connected doubly-fed induction generator (DFIG) wind power systems provided by this invention have the following advantages: By decomposing the complex grid-connected doubly-fed induction generator (DFIG) wind power system into physically clear equivalent mechanical and electrical subsystems, the analytical model is simplified. This simplifies the analysis and clearly reveals the interaction between the active power synchronization element in the grid control and the remaining electrical components of the system, providing a clear physical perspective for understanding the low-frequency oscillation mechanism. Furthermore, by deriving frequency-related elastic coefficient and damping coefficient models, the torsional vibration frequency point where electromechanical coupling oscillations occur can be accurately located, and the net damping at this frequency point can be calculated. This allows for a quantitative assessment of the system's low-frequency damping characteristics, which is more intuitive and insightful than traditional time-domain simulation or eigenvalue analysis. Finally, based on the calculated net damping value, the system's small-disturbance stability can be directly and reliably determined, and the stability margin quantified. A negative net damping value indicates a risk of low-frequency oscillation instability, and the corresponding torsional vibration frequency is the oscillation frequency. This quantitative analysis can provide clear guidance for the optimized design of wind turbine control parameters (such as the virtual inertia and damping coefficient of the virtual synchronous generator) to proactively enhance system damping, suppress low-frequency oscillations, and improve the system's stable operation under weak power grid conditions. Attached Figure Description
[0011] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0012] Figure 1 This is a flowchart illustrating the low-frequency damping torque modeling method provided by the present invention.
[0013] Figure 2 This is the main circuit topology diagram of the grid-connected doubly fed wind power system in this invention.
[0014] Figure 3 This is a control block diagram of the RSC of the grid-type doubly fed wind turbine in this invention.
[0015] Figure 4 This is the equivalent mathematical model of the grid-connected doubly fed wind power system in this invention.
[0016] Figure 5 The results show the low-frequency damping characteristics of the grid-type doubly fed wind turbine in this invention.
[0017] Figure 6 The results are simulation results of the small disturbance stability of the grid-type doubly fed wind turbine in this invention. Detailed Implementation
[0018] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.
[0019] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0021] This invention provides a low-frequency damping torque modeling method for grid-connected doubly-fed induction generator (DFIG) wind power systems. This method aims to quantitatively evaluate the low-frequency damping characteristics and small disturbance stability of DFIG wind turbines in weak grid environments by performing accurate mathematical modeling and decomposition, thereby revealing the intrinsic mechanism of low-frequency oscillations in the system and providing theoretical guidance for the optimized design of wind turbine control parameters.
[0022] In one embodiment, the low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system provided by the present invention specifically includes: Step S110: Construct a small-signal state-space model of the grid-connected system of the grid-connected doubly fed wind turbine.
[0023] Step S120: Decompose the small-signal state-space model into a set of small-signal state-space equations for an equivalent mechanical subsystem and an equivalent electrical subsystem; wherein, the equivalent mechanical subsystem consists of the active power synchronization link of the grid-type doubly fed wind turbine.
[0024] Step S130: Based on the small-signal state-space equations, derive the frequency-dependent elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and the equivalent electrical subsystem.
[0025] Step S140: Based on the elastic coefficient model, determine the torsional vibration frequency point of the grid-connected system. The torsional vibration frequency point is the frequency at which the sum of the elastic coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem is zero.
[0026] Step S150: Based on the damping coefficient model, calculate the sum of the damping coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem at the torsional vibration frequency point to obtain the net damping of the grid-connected system.
[0027] Specifically, such as Figure 2 As shown, this is the main circuit topology of a grid-connected doubly-fed induction generator (DFIG) wind turbine system. This topology comprehensively considers multiple dynamic components, including the induction motor and its shaft drive system, the rotor-side converter (RSC) and its control system, the grid-side converter (GSC) and its control system, and the DC bus capacitor. In this embodiment, the small-signal state-space model is established in the grid common coordinate system. xy The mathematical expression for the above is as follows: ; in, For each dynamic component of a grid-type doubly fed wind turbine; For the stator voltage of a grid-type doubly-fed wind turbine xy Axial components; For the small-signal state-space matrix of the grid-connected system; and These are the input and output matrices of the grid-connected system, respectively. This is to minimize the disturbance of the xy-axis components of the grid-connected current of a grid-connected doubly-fed induction generator (DFIG).
[0028] After obtaining the small-signal state-space model of the entire grid-connected system, the grid-connected system can be decomposed into an equivalent mechanical subsystem and an equivalent electrical subsystem. Correspondingly, the small-signal state-space model can be decomposed into a set of small-signal state-space equations for the equivalent mechanical subsystem and the equivalent electrical subsystem.
[0029] Reference Figure 4 The equivalent mathematical model of the grid-connected doubly-fed induction generator (DFIG) wind power system shown is presented. This decomposition helps to clearly analyze the contribution of different dynamic components to the dynamic characteristics of the system. Among them, the equivalent mechanical subsystem consists of the active power synchronization link of the grid-connected DFIG wind turbine.
[0030] In a preferred embodiment, such as Figure 3 The RSC control block diagram shown illustrates that the grid-connected control strategy for doubly-fed induction generators can be virtual synchronous generator (VSG) control. In this case, the active power synchronization link specifically corresponds to the dynamic swing equation of the virtual synchronous generator. The equivalent electrical subsystem consists of the remaining dynamic parts of the grid-connected system, including other converter control links, doubly-fed induction generators, and the dynamic equations of the weak grid.
[0031] Based on the above decomposition, the small-signal state-space equations of the equivalent mechanical subsystem are derived. The negative values of the stator active power disturbance are then considered. As input, virtual synchronization phase angle As output, the small-signal state-space equations of the equivalent mechanical subsystem can be derived from the small-signal state-space model of the rotor flux-controlled doubly-fed wind turbine: ; in, These are the state variables of the equivalent mechanical subsystem. For virtual synchronization angular frequency, For virtual synchronization phase angle, For the small-signal state-space matrix of the equivalent mechanical subsystem, and These are the input and output matrices of the equivalent mechanical subsystem, respectively.
[0032] Simultaneously, the small-signal state-space equations of the equivalent electrical subsystem are derived. The stator active power disturbance is then considered. As output, virtual synchronization phase angle As input, the small-signal state-space equations of the equivalent electrical subsystem can be derived from the small-signal state-space model of the rotor flux-controlled doubly-fed wind turbine: ; in, For the state variables of the equivalent electrical subsystem, , and These are the small output disturbances of the integral elements of the reactive power PI controller and the rotor flux PI controller, respectively. This is a small disturbance to the DC bus voltage. , and These are the small-signal state variable matrices for the induction motor shaft drive system, the grid-side converter vector control system, and the phase-locked loop control system of the grid-type doubly-fed wind turbine, respectively. This is the small-signal state-space matrix of the equivalent electrical subsystem; and These are the input and output matrices of the equivalent electrical subsystem, respectively.
[0033] In this embodiment, the control of the grid-type doubly-fed wind turbine adopts a rotor flux linkage control strategy, such as... Figure 3 As shown, this is reflected in the model construction of the equivalent electrical subsystem mentioned above.
[0034] After establishing the small-signal state-space equations of the equivalent mechanical subsystem and the equivalent electrical subsystem, the frequency-dependent elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and the equivalent electrical subsystem are further derived.
[0035] In a preferred embodiment, the derivation process is as follows: First, based on the above-mentioned small-signal state-space equations, the transfer functions of the equivalent mechanical subsystem and the equivalent electrical subsystem are calculated respectively. and Its expression is: ; in, The transfer function of the equivalent mechanical subsystem; The transfer function of the equivalent electrical subsystem. For complex frequency variables (Laplace operator). It is an identity matrix.
[0036] Subsequently, the complex frequency variables in the two transfer functions Replace with frequency domain differential operator , that is to say = To obtain the complex torque coefficient functions of the equivalent mechanical subsystem and the equivalent electrical subsystem, respectively. and Its expression is: ; in, The complex torque coefficient of the equivalent mechanical subsystem; The complex torque coefficient of the equivalent electrical subsystem; The imaginary unit; ω is the angular frequency.
[0037] Finally, the real part of the complex torque coefficient function of the equivalent mechanical subsystem is... and the virtual part These are respectively used as the elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem; and the real part of the complex torque coefficient function of the equivalent electrical subsystem is used. and the virtual part These are respectively used as elastic coefficient models and damping coefficient models for the equivalent electrical subsystem. In this way, the dynamic characteristics of the system are successfully decomposed into two frequency-dependent dimensions for analysis: elasticity and damping.
[0038] Based on the elastic coefficient model obtained from the aforementioned steps, the torsional vibration frequency of the grid-connected system can be determined. The torsional vibration frequency point It is the frequency at which the sum of the elasticity coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem is zero, i.e., it satisfies the following condition: + = 0 in, This is the torsional vibration frequency of the system; For the equivalent mechanical subsystem at the torsional vibration frequency point The elastic modulus; For the equivalent electrical subsystem at the torsional vibration frequency point The elastic coefficient.
[0039] After determining the torsional vibration frequency point Then, based on the damping coefficient model, the torsional vibration frequency can be calculated. The sum of the damping coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem yields the net damping of the grid-connected system. The calculation formula is as follows: ; in, For the equivalent mechanical subsystem at the torsional vibration frequency point Damping coefficient; For the equivalent electrical subsystem at the torsional vibration frequency point The damping coefficient.
[0040] Furthermore, this method also includes determining the small disturbance stability of the grid-connected system based on the sign of the net damping. Specifically, if the net damping is positive ( If the net damping is >0, the grid-connected system is judged to be stable under small disturbances; if the net damping is negative ( If the value is less than 0, the grid-connected system is judged to be unstable under small disturbances. In this case, the system exhibits torsional vibration frequency. Risk of instability due to low-frequency oscillations. Net damping. The value of reflects the stability margin of the grid-connected system under small disturbances; the smaller the value, the smaller the stability margin.
[0041] To verify the effectiveness of the method of the present invention, a specific simulation analysis was conducted.
[0042] Setting the virtual active inertia coefficient Virtual damping coefficient The values are 30, 32.5, and 35 respectively. Please refer to [link / reference]. Figure 5 , Figure 5 The low-frequency damping characteristic curve of the grid-connected system obtained according to the method of the present invention is shown. From Figure 5 It can be seen from this that, with different virtual damping coefficients Below, torsional vibration frequency point It remained essentially unchanged at 1.854Hz. However, with The reduction in the net damping coefficient of the grid-connected system This also gradually decreases, meaning that the stability margin of the grid-connected system for low-frequency small disturbances is decreasing. Specifically, when... When = 30, the calculated net damping coefficient A negative value indicates a risk of low-frequency oscillation and instability in the grid-connected system.
[0043] Please see Figure 6 , Figure 6 This demonstrates the different virtual damping coefficients under small disturbances in a weak power grid. Simulation results of a grid-connected doubly-fed induction generator (DFIG) wind power system. Figure 6 It can be seen that, with As the voltage gradually decreases from 60 to 30, the oscillation amplitude of the active power response curve of the doubly-fed induction generator (DFIG) gradually increases after being subjected to small disturbances in a weak power grid, while the oscillation frequency changes relatively little. When... When the power output of the wind turbine was reduced to 30, a low-frequency oscillation divergence with a frequency of 1.825Hz occurred, and the grid-connected system could no longer maintain stable operation. This simulation result is consistent with... Figure 5 The results of the low-frequency damping characteristic analysis shown are highly consistent, proving that the modeling and analysis method proposed in this invention can accurately predict the low-frequency oscillation behavior of the system and reveal the influence of control parameters on system stability.
[0044] In summary, the low-frequency damping torque modeling method for the grid-connected doubly-fed induction generator (DFIG) wind power system in this embodiment has the following technical advantages: 1. By decomposing the complex grid-connected doubly-fed wind power system into equivalent mechanical and electrical subsystems with clear physical meaning, the analysis model is simplified. This simplifies the analysis model and clearly reveals the interaction between the active power synchronization link in grid control and the rest of the electrical components of the system, providing a clear physical perspective for understanding the low-frequency oscillation mechanism.
[0045] 2. By deriving the frequency-dependent elastic coefficient model and damping coefficient model, the torsional vibration frequency point where the electromechanical coupling oscillation occurs in the system can be accurately located, and the net damping at this frequency point can be further calculated, thereby realizing the quantitative evaluation of the low-frequency damping characteristics of the system. Compared with traditional time-domain simulation or eigenvalue analysis, this method is more intuitive and profound.
[0046] 3. Based on the calculated net damping value, the stability of the system under small disturbances can be directly and reliably determined, and the stability margin can be quantified. A negative net damping value indicates that the system has a risk of low-frequency oscillation instability, and the corresponding torsional vibration frequency is the oscillation frequency. This quantitative analysis result can provide clear guidance for the optimized design of wind turbine control parameters (such as the virtual inertia and damping coefficient of the virtual synchronous generator), so as to actively enhance system damping, suppress low-frequency oscillations, and improve the system's stable operation capability under weak power grid conditions.
[0047] This application also provides a low-frequency damping torque modeling system for a grid-connected doubly-fed induction generator (DFIG) wind power system, which is used to execute the above-described method. The system includes: a model construction module for constructing a small-signal state-space model of the grid-connected DFIG wind power system; a model decomposition module for decomposing the small-signal state-space model into an equivalent mechanical subsystem and an equivalent electrical subsystem, wherein the equivalent mechanical subsystem consists of the active power synchronization element of the DFIG wind power system; a model derivation module for deriving the frequency-related elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and the equivalent electrical subsystem; a torsional vibration determination module for determining the torsional vibration frequency point of the grid-connected system based on the elastic coefficient model, wherein the torsional vibration frequency point is the frequency at which the sum of the elastic coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem is zero; and a damping calculation module for calculating the sum of the damping coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem at the torsional vibration frequency point based on the damping coefficient model, thereby obtaining the net damping of the grid-connected system. The functions of each module correspond one-to-one with the aforementioned methods and steps, and will not be repeated here.
[0048] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the low-frequency damping torque modeling method for grid-connected doubly fed wind power systems provided by the above methods.
[0049] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the low-frequency damping torque modeling method for grid-connected doubly fed wind power systems provided by the methods described above.
[0050] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. 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 embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.
[0051] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.
[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for modeling low-frequency damping torque in a grid-connected doubly-fed induction generator (DFIG) wind power system, characterized in that, include: Construct a small-signal state-space model of a grid-connected system for a doubly fed wind turbine; The small-signal state-space model is decomposed into a set of small-signal state-space equations for an equivalent mechanical subsystem and an equivalent electrical subsystem; wherein, the equivalent mechanical subsystem is composed of the active power synchronization element of the grid-type doubly-fed wind turbine; Based on the small-signal state-space equations, the frequency-dependent elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and the equivalent electrical subsystem are derived. Based on the elastic coefficient model, the torsional vibration frequency point of the grid-connected system is determined. The torsional vibration frequency point is the frequency at which the sum of the elastic coefficient of the equivalent mechanical subsystem and the elastic coefficient of the equivalent electrical subsystem is zero. Based on the damping coefficient model, the sum of the damping coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem at the torsional vibration frequency point is calculated to obtain the net damping of the grid-connected system.
2. The low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system according to claim 1, characterized in that, The grid-connected doubly-fed wind turbine uses a virtual synchronous generator control strategy, and the active power synchronization element corresponds to the dynamic swing equation of the virtual synchronous generator.
3. The low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system according to claim 1, characterized in that, The control of the grid-type doubly fed wind turbine adopts a rotor flux linkage control strategy.
4. The low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system according to claim 1, characterized in that, The small-signal state-space model is established on the power grid common coordinate system.
5. The low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system according to claim 1, characterized in that, The derivation of the frequency-dependent elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and equivalent electrical subsystem includes: Calculate the transfer functions of the equivalent mechanical subsystem and the equivalent electrical subsystem respectively; The complex frequency variables in the two transfer functions Replace with frequency domain differential operator To obtain the complex torque coefficient functions of the equivalent mechanical subsystem and the equivalent electrical subsystem, respectively; The real and imaginary parts of the complex torque coefficient function of the equivalent mechanical subsystem are used as the elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem, respectively. The real and imaginary parts of the complex torque coefficient function of the equivalent electrical subsystem are used as the elastic coefficient model and damping coefficient model of the equivalent electrical subsystem, respectively.
6. The low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system according to claim 1, characterized in that, Also includes: The small disturbance stability of the grid-connected system is determined based on the sign of the net damping.
7. The low-frequency damping torque modeling method for a grid-connected doubly-fed induction generator (DFIG) wind power system according to claim 6, characterized in that, The small disturbance stability of the grid-connected system is determined based on the sign of the net damping, specifically including: If the net damping is positive, the grid-connected system is determined to be stable under small disturbances; if the net damping is negative, the grid-connected system is determined to be unstable under small disturbances.
8. A low-frequency damping torque modeling system for a grid-connected doubly-fed induction generator (DFIG) wind power system, characterized in that, include: The model building module is used to build a small-signal state-space model of the grid-connected system of a grid-connected doubly-fed wind turbine; The model decomposition module is used to decompose the small-signal state-space model into a set of small-signal state-space equations for an equivalent mechanical subsystem and an equivalent electrical subsystem; wherein, the equivalent mechanical subsystem is composed of the active power synchronization element of the grid-type doubly-fed wind turbine; The model derivation module is used to derive the frequency-dependent elastic coefficient model and damping coefficient model of the equivalent mechanical subsystem and the equivalent electrical subsystem based on the small-signal state-space equation set. The torsional vibration determination module is used to determine the torsional vibration frequency point of the grid-connected system based on the elastic coefficient model. The torsional vibration frequency point is the frequency at which the sum of the elastic coefficient of the equivalent mechanical subsystem and the elastic coefficient of the equivalent electrical subsystem is zero. The damping calculation module is used to calculate the sum of the damping coefficients of the equivalent mechanical subsystem and the equivalent electrical subsystem at the torsional vibration frequency point based on the damping coefficient model, so as to obtain the net damping of the grid-connected system.
9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the low-frequency damping torque modeling method for a grid-connected doubly fed wind power system as described in any one of claims 1-7.
10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the low-frequency damping torque modeling method for a grid-connected doubly fed wind power system as described in any one of claims 1-7.