Impedance modeling method, device and equipment of wind power grid-connected system considering wind power active power output and medium

Abstract

This invention relates to the field of wind power grid-connected operation control technology, and particularly to a method, apparatus, equipment, and medium for impedance modeling of wind power grid-connected systems considering active power output. The method includes establishing a turbine-side model of the direct-drive wind turbine, establishing a grid-side dynamic model of the direct-drive wind turbine under small disturbances, and constructing an initial impedance model on the grid side. Based on the initial impedance model on the grid side, the active power output of the wind turbine is used as an independent variable to improve the impedance model, establishing an impedance model of the wind power grid-connected system that includes the influence factor of the wind turbine output level. The equivalent impedance of the wind power grid-connected system under different active power output conditions is calculated, and the stability of the system under different active power output conditions is evaluated. The differences in the output of each wind turbine are considered in the stability analysis of the wind power grid-connected system, so that the active power output, as an independent variable, directly affects the impedance model of the wind power grid-connected system, providing modeling support for the research and mechanism analysis of the influence of parameters such as wind power active power output on the stability of the grid-connected system.

Description

Technical Field

[0001] This invention relates to the field of wind power grid-connected operation control technology, and in particular to a method, apparatus, equipment and medium for impedance modeling of wind power grid-connected systems that considers the active power output of wind power. Background Technology

[0002] In recent years, my country's wind power industry has developed rapidly, becoming an important force in promoting energy structure transformation. According to data from the National Energy Administration, as of the first half of 2024, the newly added grid-connected wind power capacity nationwide reached 25.84 million kilowatts, a year-on-year increase of 12%, with the cumulative grid-connected capacity exceeding 467 million kilowatts, a year-on-year increase of 20%. These figures not only demonstrate the crucial position of wind power in my country's energy structure but also indicate the enormous potential of the wind power industry in the future. In terms of power generation, in the first half of 2024, national wind power generation reached 508.8 billion kilowatt-hours, a year-on-year increase of 10%. The proportion of wind power in the country's total power generation continues to rise, making it the second largest source of electricity after thermal power. With its clean and renewable characteristics, wind power provides important support for achieving the "dual carbon" goals (carbon reduction and emission reduction).

[0003] However, in large-scale wind farms, due to differences in the location and wind speed of different turbines, the operating modes of the turbines are not uniform. This leads to inconsistent active power output of each turbine. During the operation of the wind farm, the changes in active power output have a significant impact on the stability of the grid-connected system. When the active power output changes, the initial values ​​of the system's state variables change accordingly, which in turn affects the interaction between various system components. Therefore, studying the impact of active power output on the stability of the grid-connected system is of great significance for improving the overall stability of the system.

[0004] While existing models for direct-drive wind turbine grid-connected systems can analyze the impact of active power output on system stability to some extent, they have shortcomings in the following aspects: First, existing models cannot effectively quantify the specific impact of active power output on system stability; second, existing models lack intuitive and clear model support when analyzing the mechanism by which wind turbine output affects grid-connected system stability. Therefore, current impedance modeling methods for wind power grid-connected systems cannot fully and accurately reflect the impact of dynamic changes in wind power active power output on system stability. Thus, it is necessary to establish an impedance modeling method for wind power grid-connected systems that considers the impact of wind power active power output to better support system stability analysis and optimized control.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a method, apparatus, equipment, and medium for impedance modeling of wind power grid-connected systems that considers the active power output of wind power, thereby effectively solving the problems in the background art.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: an impedance modeling method for wind power grid-connected systems considering active power output, comprising the following steps:

[0008] S10: Establish a machine-side model of the direct-drive wind turbine. The machine-side model is based on the machine-side topology and control loop of the direct-drive wind turbine, adopts the dq rotating coordinate system, and sets the d-axis along the direction of the permanent magnet flux linkage of the direct-drive generator.

[0009] S20: Based on the machine-side model, establish a grid-side small disturbance dynamic model for the direct-drive wind turbine. The grid-side small disturbance dynamic model is based on the grid-side topology and control loop. The control loop includes a voltage outer loop control model and a current inner loop control model, considering the small disturbance effect of the phase-locked loop on the grid connection point voltage.

[0010] S30: Connect the machine side and the grid side through a back-to-back DC link, and convert the output power of the machine side converter into a constant power source. Ignore the influence of machine side dynamics on the grid side small disturbance dynamic model, and construct the initial impedance model of the grid side.

[0011] S40: Based on the initial impedance model on the grid side, the active power output of the wind turbine is used as the independent variable to establish an impedance model of the wind power grid-connected system that includes the influence factor of the wind turbine output level.

[0012] S50: Based on the impedance model of the wind power grid-connected system, calculate the equivalent impedance of the wind power grid-connected system under different active power output conditions, and evaluate the stability of the system under different active power output conditions.

[0013] Further, in step S20, the current inner loop control model of the grid-side converter includes:

[0014]

[0015] In the formula, U cd U cq These are the d-axis and q-axis components of the grid-side converter output voltage, respectively. c (s) is the inner current loop transfer function, I cdref I cqref These represent the d-axis and q-axis components of the grid-side converter output current reference value, respectively. cd I cq These represent the d-axis and q-axis components of the grid-side converter output current, respectively, where ω1 is the fundamental angular frequency, and L... g This is the grid-side filter inductor.

[0016] Further, in step S20, the voltage outer loop control model includes:

[0017]

[0018] In the formula, I cdref I cqref These represent the d-axis and q-axis components of the grid-side converter output current reference value, respectively. dc U is the DC side voltage. dcref H is the reference value for the DC side voltage. u (s) is the transfer function of the outer voltage loop.

[0019] Further, in step S20, the control model that considers the small disturbance effect of the phase-locked loop on the grid connection point voltage includes:

[0020]

[0021] In the formula, ω pll H is the output angular frequency of the phase-locked loop. pll (s) is the phase-locked loop transfer function, u q θ is the q-axis component of the grid-side converter output voltage after passing through a filter. pll The phase angle is the output phase angle of the phase-locked loop, s is the differential symbol d / dt, and k is the phase angle of the phase-locked loop. p k i These are the proportional and integral control parameters of the phase-locked loop PI controller.

[0022] Further, in step S20, the grid-side small disturbance dynamic model, considering small disturbances, describes the small-signal relationship between voltage and current of the grid-side converter in the dq rotating coordinate system, including:

[0023]

[0024] Where, Δu dq The small-signal dq-axis voltage component of the grid-side converter after filtering, Δu cdq Δi is the dq-axis small-signal component of the grid-side converter output voltage. cdqref The small-signal component of the dq axis of the grid-side converter output current reference value, Δi cdq G represents the small-signal component of the dq-axis output current of the grid-side converter. c Let G be the transfer function of the inner current loop. l G is the transfer function of the filtering stage. o This is the coupling impedance transfer function.

[0025] Further, in step S20, the grid-side small disturbance dynamic model, which considers the impact of the phase-locked loop on the small disturbance of the grid connection point voltage, includes:

[0026]

[0027] In the formula, G represents the transfer function characterizing the effect of small disturbances in the phase-locked loop on the grid-side terminal voltage and current, respectively. c Let G be the transfer function of the inner current loop. o The coupling impedance transfer function, The small-signal components of the grid-side converter output voltage and current on the dq axis in the system coordinate system are respectively characterized.

[0028] Further, in step S30, the small-signal model of the DC link voltage obtained from the DC link topology and active power transmission relationship, which connects the generator side and the grid side via a back-to-back DC link, includes:

[0029]

[0030] In the formula, U cd U cq These are the d-axis and q-axis components of the grid-side converter output voltage, respectively. cd I cq These are the d-axis and q-axis components of the grid-side converter output current, respectively. dc For back-to-back DC link output current, U dc This is the voltage across capacitor C1 in the DC link.

[0031] Further, in step S30, the small-signal model for obtaining the current loop reference value by connecting the machine side and the grid side through a back-to-back DC link includes:

[0032] Δi cdqref =G uw G w (G vi Δi cdq +G vu Δu cdq );

[0033] In the formula, G w To characterize the influence factor of output level on wind turbine impedance, G vi G is the small-signal transfer function of the DC link current. vu Let Δu be the small-signal transfer function of the DC link voltage. cdq Δi is the dq-axis small-signal component of the grid-side converter output voltage. cdq This refers to the small-signal component of the dq axis output current of the grid-side converter.

[0034] Further, in step S40, the establishment of a wind power grid-connected system impedance model including the wind turbine output level influencing factor, wherein the model of the wind turbine output level influencing factor includes:

[0035]

[0036] In the formula, G w To characterize the influence factor of output level on wind turbine impedance, P dc U is the equivalent output power on the machine side. dc s represents the voltage across capacitor C1 in the DC link, where C1 is the capacitance across the back-to-back link, and s represents the differential symbol d / dt.

[0037] Further, in step S40, based on the initial impedance model on the grid side, the active power output of the wind turbine is used as the independent variable to establish a wind power grid-connected system impedance model that includes the influence factor of the wind turbine output level. The equivalent impedance of the direct-drive wind turbine itself is defined as the ratio of voltage to current. The wind power grid-connected system impedance model includes:

[0038]

[0039] In the formula, Z pmsg For the impedance model of the wind power grid-connected system, Δu cdq Δi is the dq-axis small-signal component of the grid-side converter output voltage. cdq G represents the small-signal component of the dq-axis output current of the grid-side converter. c Let G be the transfer function of the inner current loop. uw Let G be the voltage outer loop transfer function. o The coupling impedance transfer function, G represents the transfer function characterizing the effect of small disturbances in the phase-locked loop on the grid-side terminal voltage and current, respectively. w To characterize the influence factor of output level on wind turbine impedance, G vi G is the small-signal transfer function of the DC link current. vu This is the small-signal transfer function of the DC link voltage.

[0040] The present invention also includes an impedance modeling device for a wind power grid-connected system that considers the active power output of wind power, using the method described above, comprising:

[0041] The machine-side model building unit is used to build a machine-side model of the direct-drive wind turbine. The machine-side model is based on the machine-side topology and control links of the direct-drive wind turbine, adopts the dq rotating coordinate system, and sets the d-axis along the magnetic flux direction of the permanent magnet of the direct-drive generator.

[0042] The grid-side small disturbance dynamic model establishment unit is used to establish a grid-side small disturbance dynamic model of the direct-drive wind turbine based on the turbine-side model. The grid-side small disturbance dynamic model is based on the grid-side topology and control loop. The control loop includes a voltage outer loop control model and a current inner loop control model, and considers the influence of phase-locked loop on small disturbances in the grid connection point voltage.

[0043] The grid-side initial impedance model construction unit is used to connect the machine side and the grid side through a back-to-back DC link, to convert the output power of the machine-side converter into a constant power source, ignore the influence of machine-side dynamics on the grid-side small disturbance dynamic model, and construct the grid-side initial impedance model.

[0044] The wind turbine output level impedance model improvement unit is used to establish a wind power grid-connected system impedance model that includes the wind turbine output level influence factor, based on the initial impedance model on the grid side and taking the active power output of the wind turbine as the independent variable.

[0045] The system stability assessment unit is used to calculate the equivalent impedance of the wind power grid-connected system under different active power output conditions based on the impedance model of the wind power grid-connected system, and to assess the stability of the system under different active power output conditions.

[0046] The present invention also includes a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the method as described above.

[0047] The present invention also includes a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method as described above.

[0048] The beneficial effects of this invention are as follows:

[0049] By incorporating the differences in the output of each wind turbine into the stability analysis of the wind power grid-connected system, the active power output is made an independent variable that directly affects the impedance model of the wind power grid-connected system, providing modeling support for the study and mechanism analysis of the impact of parameters such as wind power active power output on the stability of the grid-connected system.

[0050] By introducing active power output as an independent variable, the impedance model is improved, enabling direct quantitative analysis of the impact of active power output on system stability. This makes system design and optimization control more precise, and solves the problem that existing models cannot clearly quantify the impact of wind power active power output. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present 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 only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 A flowchart illustrating the impedance modeling method for wind power grid-connected systems that takes into account the active power output of wind power.

[0053] Figure 2A schematic diagram of the structure and control components of a direct-drive wind power grid-connected system;

[0054] Figure 3 This is the equivalent circuit diagram of the main circuit on the machine side;

[0055] Figure 4 Diagram of the equivalent grid-connected structure and control structure of a direct-drive fan, neglecting side dynamics.

[0056] Figure 5 This is a topology diagram of a back-to-back component in a direct-drive fan.

[0057] Figure 6 This is a schematic diagram of a phase-locked loop (PLL).

[0058] Figure 7 A schematic diagram of the impedance modeling device for a wind power grid-connected system that takes into account the active power output of wind power.

[0059] Figure 8 This is a schematic diagram of the structure of a computer device. Detailed Implementation

[0060] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0061] like Figure 1 As shown: An impedance modeling method for a wind power grid-connected system considering the active power output of wind power, comprising the following steps:

[0062] S10: Establish the machine-side model of the direct-drive wind turbine. The machine-side model is based on the machine-side topology and control links of the direct-drive wind turbine. The dq rotating coordinate system is adopted, and the d-axis is set along the direction of the magnetic flux of the permanent magnet of the direct-drive generator.

[0063] S20: Based on the machine-side model, establish a grid-side small disturbance dynamic model for direct-drive wind turbines. The grid-side small disturbance dynamic model is based on the grid-side topology and control loop. The control loop includes a voltage outer loop control model and a current inner loop control model, considering the influence of phase-locked loop (PLL) on small disturbances in the grid connection point voltage.

[0064] S30: Connect the generator side and grid side through a back-to-back DC link, and convert the output power of the generator side converter into a constant power source. Ignore the influence of generator side dynamics on the grid side small disturbance dynamic model, and construct the initial impedance model of the grid side.

[0065] S40: Based on the initial impedance model on the grid side, the active power output of the wind turbine is used as the independent variable to improve the impedance model and establish an impedance model of the wind power grid-connected system that includes the influence factor of the wind turbine output level.

[0066] S50: Based on the impedance model of wind power grid-connected systems, calculate the equivalent impedance of wind power grid-connected systems under different active power output conditions, and evaluate the stability of the system under different active power output conditions.

[0067] By incorporating the differences in the output of each wind turbine into the stability analysis of the wind power grid-connected system, the active power output is made an independent variable that directly affects the impedance model of the wind power grid-connected system, providing modeling support for the study and mechanism analysis of the impact of parameters such as wind power active power output on the stability of the grid-connected system.

[0068] While existing models of direct-drive wind turbine grid-connected systems can analyze the impact of active power output on system stability, they cannot quantify this impact. By introducing active power output as an independent variable, the impedance model is improved, enabling a quantitative analysis of the impact of active power output on system stability. This makes system design and optimization control more precise and solves the problem that existing models cannot clearly quantify the impact of wind power active power output.

[0069] This technical solution considers the independent establishment and correlation of turbine-side and grid-side models when constructing the wind power grid-connected system model. In particular, it analyzes in detail the impact of control loops (such as voltage outer loop and current inner loop) on system stability through small disturbance dynamic model and impedance model. Combined with the impact of phase-locked loop (PLL) on grid connection point voltage, it further improves the accuracy of system analysis. This comprehensive analysis method helps to more accurately reflect the dynamic characteristics of wind power grid-connected system under different active power output conditions.

[0070] By constructing an impedance model that includes factors affecting wind turbine output levels, this technical solution can calculate the equivalent impedance of the wind power system under different active power output conditions and evaluate the stability of the system under different conditions. This provides a theoretical basis for improving the grid-connected adaptability and safety of wind farms, enabling the system to more flexibly cope with the system instability risks caused by wind turbine output fluctuations.

[0071] By using back-to-back DC links to convert the output power of the generator-side converter into a constant power source and ignoring the impact of generator-side dynamics on the grid-side small disturbance model, this simplification not only reduces the complexity of model calculations but also provides a rapid response capability for the real-time control of wind power grid-connected systems, enabling the system to adjust to changes in active power output more efficiently in actual operation.

[0072] With a well-developed impedance model, it can better support system stability analysis and optimized control, and provides a more intuitive and accurate analysis tool. This provides modeling support for the optimization design, scheduling and control strategies of future wind power systems, and has important engineering application value.

[0073] by Figure 2The direct-drive wind power grid-connected system shown is the object of analysis. A schematic diagram of the topology of the turbine-side converter is provided. Based on its topology and control components, a model of the wind power grid-connected system in the dq rotating coordinate system is established.

[0074] In step S10, the machine-side model includes modeling the impeller of the direct-drive wind turbine, the permanent magnet synchronous generator, the machine-side converter, and the grid-side converter. The impeller is used to convert wind energy into mechanical energy, the mechanical energy is converted into electromagnetic power through the permanent magnet synchronous generator, and the electromagnetic power is transmitted to the power grid by the machine-side converter and the grid-side converter.

[0075] The wind power is:

[0076]

[0077] Where ρ is the air density, S wind Where is the swept area and v is the wind speed.

[0078] The mechanical power converted from wind power by the impeller is:

[0079]

[0080] Among them, C p The wind energy utilization coefficient depends on the efficiency of the interaction between wind and the wind turbine during the energy conversion process. For example... Figure 3 As shown, the stator voltage expression can be obtained from the equivalent circuit of the main circuit on the machine side:

[0081] U s =E+R s I s +jω s L s I s =jω r ψ f +R s I s +jω s L s I s ;

[0082] In the formula, U s For stator voltage, I s For stator current, L s For stator inductance, R s For the stator resistance, ω s Let ω be the stator angular velocity. r Let ψ be the rotor angular velocity. f For stator flux linkage.

[0083] Since the converter control is based on two rotating coordinate systems, the variables are decomposed into dq values. The d-axis of the dq rotating coordinate system is set to the direction of the permanent magnet flux linkage of the direct-drive generator, resulting in the voltage equation of the main circuit on the generator side in the synchronous rotating coordinate system:

[0084]

[0085] At this time, the expressions for the active power and reactive power on the machine side are:

[0086]

[0087] The torque expression is:

[0088]

[0089] The machine side employs rotor magnetic field orientation vector control, with the d-axis located in the direction of the magnetic flux linkage of the rotor permanent magnet, let i sd =0, so that the motor has no armature reaction on the d-axis, that is, the direct axis does not contribute torque, and all the current of the motor is used to generate electromagnetic torque, which simplifies the control. Therefore:

[0090]

[0091]

[0092]

[0093] From the control block diagram of the direct-drive wind turbine, the power outer loop control model of the turbine-side converter is as follows:

[0094]

[0095] The current inner loop control model for the machine-side converter is as follows:

[0096]

[0097] In this embodiment, the electromagnetic power model of the machine-side converter includes:

[0098]

[0099] In the formula, P dc For electromagnetic power, ω r T is the rotor angular velocity. e For electromagnetic torque, P n Let ψ be the extreme logarithm. f For stator flux linkage, i sq This is the stator current.

[0100] In the stability analysis of grid-connected direct-drive wind turbines, since the large capacitor of the DC link isolates the turbine side from the grid side, the dynamics of the turbine side have little impact on the small disturbance dynamic model of the grid-connected system. Therefore, the wind turbine and the turbine-side converter are equivalent to constant power sources, and it is assumed that the output power of the turbine-side converter remains unchanged under the time scale under study, and its dynamic influence is ignored.

[0101] like Figure 4 As shown, a dynamic model of small disturbances on the grid side of a direct-drive wind power system is established based on the grid-side topology and control links of the direct-drive wind turbine.

[0102] The machine side and the grid side of the direct-drive fan are connected by a back-to-back structure, such as... Figure 5 As shown in the diagram, the power transmission between the machine side and the grid side is illustrated. From the topology diagram, the power on the capacitor in the back-to-back DC link is:

[0103]

[0104] In the formula, P s P represents the active power output of the machine-side converter. dc U is the active power input to the grid-side converter, C1 is the capacitor in the back-to-back circuit, and U is the active power input to the grid-side converter. dc This refers to the capacitor voltage in a back-to-back DC link.

[0105] To achieve zero power loss in the DC link, i.e., P s =P dc According to the above formula, it can be deduced that U should be such that dc This objective remains unchanged and is achieved through the voltage outer loop of the grid-side converter.

[0106] Due to the presence of a large capacitor in the DC link, the dynamics of the generator side have a negligible impact on the grid side. Therefore, the generator side is equivalent to a constant power source, which is connected to the grid side via the large capacitor. Its output power is:

[0107] P dc =U dc I dc ;

[0108] In the formula, P dc U is the equivalent output power on the machine side. dc I is the voltage across capacitor C1 in the DC link. dc This is the output current for a back-to-back DC link.

[0109] For the grid-side converter, the power transferred from the DC link is:

[0110]

[0111] In the formula, U cd U cqThese are the d-axis and q-axis components of the grid-side converter output voltage, respectively. cd I cq These are the d-axis and q-axis components of the grid-side converter output current, respectively.

[0112] refer to Figure 4 The terminal voltage equation of the grid-side converter in the dq coordinate system is as follows:

[0113]

[0114] In the formula, u d u q These are the voltages across the grid side after passing through the filter inductor, where s is the differential symbol d / dt, and L... g ω1 is the grid-side filter inductor, and ω1 is the fundamental angular frequency.

[0115] refer to Figure 5 The current in a DC link has the following relationship:

[0116] I dc +I1=I2→I dc +sC1U dc =I2;

[0117] In this embodiment, in step S20, the current inner loop control model of the grid-side converter includes:

[0118]

[0119] In the formula, U cd U cq These are the d-axis and q-axis components of the grid-side converter output voltage, respectively. c (s) is the inner current loop transfer function, I cdref I cqref These represent the d-axis and q-axis components of the grid-side converter output current reference value, respectively. cd I cq These represent the d-axis and q-axis components of the grid-side converter output current, respectively, where ω1 is the fundamental angular frequency, and L... g This is the grid-side filter inductor.

[0120] By establishing a current inner-loop control model in the dq-axis coordinate system, the grid-side converter can respond quickly to changes in system current, achieving more precise current control, reducing the system's dynamic response time, and improving overall control performance. The current inner-loop control model utilizes a filter inductor L... g The dynamic adjustment of the fundamental frequency ω1 can effectively suppress current fluctuations in the system under different operating conditions, ensure the voltage and current stability of the grid-side converter, and reduce the impact of small-signal disturbances on system stability.

[0121] As a preferred embodiment of the above, in step S20, the voltage outer loop control model includes:

[0122]

[0123] In the formula, I cdref I cqref These represent the d-axis and q-axis components of the grid-side converter output current reference value, respectively. dc U is the DC side voltage. dcref H is the reference value for the DC side voltage. u (s) is the transfer function of the outer voltage loop.

[0124] make To characterize the voltage outer loop transfer function, after small-signal processing, we have:

[0125] Δi cdqref =G uw ΔU dc ;

[0126] In the formula, Δi cdqref G represents the small-signal component of the dq axis of the grid-side converter output current reference value. uw Let ΔU be the transfer function of the outer voltage loop. dc This refers to a small signal quantity of the DC-side voltage;

[0127] Through the voltage outer loop transfer function G uw The introduction of this feature enables the system to respond rapidly to changes in DC voltage and quickly adjust the reference value of the grid-side converter output current, thereby improving the system's dynamic response speed and control accuracy. The small-signal model, through real-time feedback control of the voltage, ensures that the DC-side voltage accurately follows the reference value Δi under different load conditions. cdqref This effectively reduces the impact of voltage fluctuations on system stability and improves the voltage stability of the grid-connected system.

[0128] The control system of the grid-connected system is based on the dq coordinate system, while the grid voltage is based on the abc three-phase coordinate system. The wind power grid-connected system maintains synchronization by tracking the system components through a phase-locked loop (PLL). During this process, small disturbances in the PLL can also affect the converter output. This paper refers to the dq coordinate system, established by the actual phase angles in the system, as the main circuit coordinate system, with each component denoted by the superscript "g". Variables without superscripts are assumed to be in the main circuit coordinate system. The coordinate system established based on the PLL output phase angles is referred to as the control coordinate system, with each component denoted by the superscript "c".

[0129] In step S20, such as Figure 6 The diagram shows a phase-locked loop (PLL) schematic. The control model considering the impact of small disturbances in the grid connection voltage on the PLL includes:

[0130]

[0131] In the formula, ω pll H is the output angular frequency of the phase-locked loop. pll (s) is the phase-locked loop transfer function, u q θ is the q-axis component of the grid-side converter output voltage after passing through a filter. pll The phase angle is the output phase angle of the phase-locked loop, s is the differential symbol d / dt, and k is the phase angle of the phase-locked loop. p k i These are the proportional and integral control parameters of the phase-locked loop PI controller.

[0132] By introducing the small-signal transfer function H of the phase-locked loop pll (s) can accurately track the phase angle change of the grid connection point voltage, ensuring real-time synchronization of the system voltage and reducing voltage phase deviation caused by small disturbances; the phase-locked loop precisely adjusts the output angular frequency ω pll And update the phase angle θ in real time. pll It can quickly respond to changes in grid frequency, ensuring the synchronization of grid-connected voltage with grid frequency.

[0133] The output disturbance angle of the phase-locked loop can be obtained from the above formula:

[0134]

[0135] To express the effect of small disturbances in the phase-locked loop on the grid connection point voltage, the following transfer function is used:

[0136]

[0137] In the formula, K pll The transfer function characterizes the effect of phase-locked loop disturbances. These represent the small-signal components of the grid-side converter output voltage on the d and q axes in the main circuit coordinate system after filtering. These are the small signal components of the grid-side converter output voltage on the d and q axes in the control coordinate system after filtering.

[0138] Adding a small voltage signal disturbance at the grid connection point results in the following under the system dq system:

[0139]

[0140] In the formula, u pcc U is the actual voltage at the grid connection point. pcc The steady-state voltage at the grid connection point, Δu pcc For small disturbance signals of grid connection point voltage, The steady-state components of the grid-side converter output voltage on the d and q axes in the main circuit coordinate system after filtering. These are the d-axis and q-axis steady-state components of the grid-side converter output voltage after filtering in the control coordinate system.

[0141] Substituting the above equation into the small disturbance transformation relationship expression of the system dq system and the control dq system, we can obtain the small disturbance transformation relationship expression of the grid-side terminal voltage and current in the system dq system and the control dq system:

[0142]

[0143]

[0144]

[0145] Then, by rearranging, we can obtain:

[0146]

[0147] As a preferred embodiment of the above, in step S20, the grid-side small disturbance dynamic model, considering small disturbances, is a small-signal relationship model describing the voltage and current of the grid-side converter in the dq rotating coordinate system, including:

[0148]

[0149] Where, Δu dq The small-signal dq-axis voltage component of the grid-side converter after filtering, Δu cdq Δi is the dq-axis small-signal component of the grid-side converter output voltage. cdqref The small-signal component of the dq axis of the grid-side converter output current reference value, Δi cdq G represents the small-signal component of the dq-axis output current of the grid-side converter. c Let G be the transfer function of the inner current loop. l G is the transfer function of the filtering stage. o This is the coupling impedance transfer function.

[0150] By describing the voltage and current using a small-signal model in the dq rotating coordinate system, this technical solution can quickly identify the impact of small disturbances on voltage and current, thereby improving the dynamic response performance of the system and ensuring that the converter can quickly adjust its output when faced with external disturbances, reducing response time; coupling impedance transfer function G o This helps reduce the coupling effects between different components within the system, enabling the system to better maintain voltage and current stability when faced with small disturbances, improving disturbance rejection performance, and reducing the impact of the external environment on system operation; through the transfer function G of the filtering stage. l By filtering the output signal, this model can effectively suppress harmonics and other high-frequency components, improve the power quality of the system, and ensure the stable operation of the system under different wind turbine active power output conditions.

[0151] In this embodiment, in step S20, the grid-side small disturbance dynamic model, which considers the influence of the phase-locked loop (PLL) on the small disturbance voltage at the grid connection point, includes:

[0152]

[0153] In the formula, G represents the transfer function characterizing the effect of small disturbances in the phase-locked loop on the grid-side terminal voltage and current, respectively. c Let G be the transfer function of the inner current loop. o The coupling impedance transfer function, The small-signal components of the grid-side converter output voltage and current on the dq axis in the system coordinate system are respectively characterized.

[0154] A small perturbation transfer function for voltage and current is introduced through a phase-locked loop (PLL) model. and It can accurately track the phase change of the grid connection point voltage, ensuring that the voltage phase is synchronized with the grid, which helps to reduce synchronization deviations caused by voltage fluctuations and improve system stability; the inner current transfer function G c The introduction of this feature enhances the system's dynamic response capability when small disturbances occur. The system can quickly adjust the current and promptly compensate for voltage disturbances at the grid connection point, ensuring stable system operation when wind power output changes; the coupling impedance transfer function G o The introduction of this technology effectively reduces the mutual coupling interference between different modules within the system, enhances the system's anti-interference capability under external disturbance conditions, and thus improves the system's operational stability. Through small-signal analysis in the dq-axis rotating coordinate system, the system can accurately describe the changing trends of voltage and current, ensuring high-precision control of the grid-side converter under dynamic operating conditions, which helps improve the overall efficiency and stability of the wind power grid-connected system. Considering the impact of the phase-locked loop on the grid connection point voltage, the system can reduce the impact of external grid fluctuations on the operation of the wind power grid-connected system, ensuring stable grid connection when the wind turbine output fluctuates.

[0155] In step S30, the small-signal model of the DC link voltage, obtained from the DC link topology and active power transmission relationship, is constructed by connecting the generator side and the grid side via a back-to-back DC link. This model includes:

[0156]

[0157] In the formula, U cd U cq These are the d-axis and q-axis components of the grid-side converter output voltage, respectively. cd I cq These are the d-axis and q-axis components of the grid-side converter output current, respectively. dcFor back-to-back DC link output current, U dc This is the voltage across capacitor C1 in the DC link.

[0158] By using a small-signal model of the DC link, the system can accurately analyze and predict the dynamic changes of voltage and current, enhancing the system's response speed and control accuracy to input disturbances; through dq-axis small-signal analysis of voltage and current, the system can effectively monitor the DC capacitance U. dc and output current I dc The model ensures voltage stability under different wind turbine output levels by accurately describing the relationship between DC link voltage and current, thereby reducing the impact of fluctuations on system operation. It also improves the system's immunity to grid voltage fluctuations and wind turbine output changes, ensuring stable system operation.

[0159] Small-signal model for obtaining current loop reference values:

[0160]

[0161] make

[0162] In step S30, the small-signal model of the current loop reference value is obtained by connecting the machine side and the grid side through a back-to-back DC link, including:

[0163] Δi cdqref =G uw G w (G vi Δi cdq +G vu Δu cdq );

[0164] In the formula, G w To characterize the influence factor of output level on wind turbine impedance, G vi G is the small-signal transfer function of the DC link current. vu Let Δu be the small-signal transfer function of the DC link voltage. cdq Δi is the dq-axis small-signal component of the grid-side converter output voltage. cdq This refers to the small-signal component of the dq axis output current of the grid-side converter.

[0165] Using the current reference value provided by the small-signal model, the system can precisely adjust the output of the current loop, improving the current control accuracy. This is crucial for maintaining a stable current output, especially when the wind turbine output fluctuates; the small-signal transfer function G... vi and G vu The introduction of this technology helps the system respond quickly to changes in DC current and voltage, optimizes the dynamic response capability of the current loop control, and reduces current fluctuations caused by power changes; by analyzing the wind turbine output level G...w Regarding the impact of impedance, the system can better adapt to different load conditions, maintain system stability, and avoid system instability caused by output fluctuations. The small-signal model can better handle grid voltage fluctuations and external disturbances, and ensure stable operation of the system under disturbance conditions by adjusting the reference value of the current loop in real time.

[0166] I can be established from the power expression of the DC link. dc With P dc The relation, therefore G w Factors that can be used to characterize the influence of power output level on wind turbine impedance:

[0167] In this embodiment, in step S40, an impedance model of the wind power grid-connected system including the wind turbine output level influencing factor is established. The model of the wind turbine output level influencing factor includes:

[0168]

[0169] In the formula, G w To characterize the influence factor of output level on wind turbine impedance, P dc U is the equivalent output power on the machine side. dc s represents the voltage across capacitor C1 in the DC link, where C1 is the capacitance across the back-to-back link, and s represents the differential symbol d / dt.

[0170] By establishing a model of influencing factors G of wind turbine output level w It can be based on the actual output power P of the fan dc and DC voltage U dc The system dynamically adjusts its impedance to ensure high-precision impedance matching under different loads and turbine output levels. By considering the relationship between turbine output power and DC voltage, the system can reflect the impact of turbine output changes on impedance in real time, thereby quickly adjusting the grid-connected system impedance, improving dynamic response speed, and ensuring the system can quickly adapt to fluctuations in turbine output. Through the capacitor C1 and differential operator s in the model, the system can accurately analyze the impact of changes in DC link capacitor voltage on impedance, thereby improving the system's voltage stability, especially effectively suppressing voltage fluctuations during large-scale turbine output fluctuations. By precisely controlling the impact of turbine output level on impedance, the system can reduce voltage and current fluctuations caused by power fluctuations, thereby improving the power quality of the grid-connected system and reducing harmonic generation.

[0171] Substituting this into the small-signal model of the grid-side current loop considering the influence of the phase-locked loop, we get:

[0172]

[0173] As a preferred embodiment of the above, in step S40, based on the initial impedance model on the grid side, the active power output of the wind turbine is used as the independent variable to establish a wind power grid-connected system impedance model that includes the influence factor of the wind turbine output level. The equivalent impedance of the direct-drive wind turbine itself is defined as the ratio of voltage to current. The wind power grid-connected system impedance model includes:

[0174]

[0175] In the formula, Z pmsg For the impedance model of the wind power grid-connected system, Δu cdq Δi is the dq-axis small-signal component of the grid-side converter output voltage. cdq G represents the small-signal component of the dq-axis output current of the grid-side converter. c Let G be the transfer function of the inner current loop. uw Let G be the voltage outer loop transfer function. o The coupling impedance transfer function, G represents the transfer function characterizing the effect of small disturbances in the phase-locked loop on the grid-side terminal voltage and current, respectively. w To characterize the influence factor of output level on wind turbine impedance, G vi G is the small-signal transfer function of the DC link current. vu This is the small-signal transfer function of the DC link voltage.

[0176] By using the active power output of the wind turbine as the independent variable based on the initial impedance model on the grid side, an influence factor G on the power output level is introduced. w This allows for precise analysis of the dynamic impact of different wind turbine output levels on system impedance. This enables the wind power grid-connected system to maintain accurate impedance matching under different operating conditions, thereby improving the stability of system operation.

[0177] Coupling impedance transfer function G o It helps reduce coupling interference between different components and improves the system's ability to resist external disturbances. Whether it is fluctuation in wind turbine output or disturbances on the grid side, the system can remain stable and reduce voltage or current fluctuations caused by coupling effects.

[0178] Transfer function via small perturbation of phase-locked loop (PLL) and The system can better adjust the phase and amplitude of the grid-side voltage. This adjustment ensures that the system can maintain precise voltage control under conditions of voltage disturbances or power output fluctuations, thereby improving the power quality of the grid-connected system.

[0179] DC link current and voltage small-signal transfer function G c and G uwThe introduction of this technology enables real-time monitoring and adjustment of the current and voltage in the DC link, ensuring precise current control under varying output conditions. This helps reduce the impact of power fluctuations on system stability and improves the efficiency and reliability of the grid-connected system.

[0180] The introduction of the active power output of the wind turbine as an independent variable enables the system to dynamically adjust the impedance model according to the output level of the wind turbine, ensuring that the system can maintain stable operation under various load conditions, reducing the interference of current and voltage fluctuations on system operation, and improving the overall stability of the wind power grid connection system.

[0181] This invention also includes an impedance modeling device for a wind power grid-connected system that considers the active power output of wind power, using the method described above, such as... Figure 7 As shown, it includes:

[0182] The machine-side model building unit is used to build the machine-side model of the direct-drive wind turbine. The machine-side model is based on the machine-side topology and control links of the direct-drive wind turbine, adopts the dq rotating coordinate system, and sets the d-axis along the direction of the permanent magnet flux linkage of the direct-drive generator.

[0183] The grid-side small disturbance dynamic model establishment unit is used to establish a grid-side small disturbance dynamic model of the direct-drive wind turbine based on the machine-side model. The grid-side small disturbance dynamic model is based on the grid-side topology and control loop. The control loop includes a voltage outer loop control model and a current inner loop control model, and considers the influence of phase-locked loop (PLL) on small disturbances in the grid connection point voltage.

[0184] The grid-side initial impedance model construction unit is used to connect the machine side and the grid side through a back-to-back DC link, and to convert the output power of the machine-side converter into a constant power source, ignoring the influence of machine-side dynamics on the grid-side small disturbance dynamic model, and to construct the grid-side initial impedance model.

[0185] The wind turbine output level impedance model improvement unit is used to improve the impedance model based on the initial impedance model on the grid side, taking the active power output of the wind turbine as the independent variable, and establish an impedance model of the wind power grid-connected system that includes the influence factor of the wind turbine output level.

[0186] The system stability assessment unit is used to calculate the equivalent impedance of the wind power grid-connected system under different active power output conditions based on the wind power grid-connected system impedance model, and to assess the stability of the system under different active power output conditions.

[0187] Please see Figure 8 The diagram shows a structural schematic of a computer device provided in an embodiment of this application. An embodiment of this application provides a computer device 400, including a processor 410 and a memory 420. The memory 420 stores a computer program executable by the processor 410. When the computer program is executed by the processor 410, it performs the method described above.

[0188] This application embodiment also provides a storage medium 430, on which a computer program is stored, and the computer program is executed by a processor 410 to perform the above method.

[0189] The storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0190] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0191] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0192] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0193] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0194] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0195] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0196] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0197] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A wind power grid-connected system impedance modeling method considering wind power active power output, characterized in that, Includes the following steps: S10: Establish a machine-side model of the direct-drive wind turbine. The machine-side model is based on the machine-side topology and control loop of the direct-drive wind turbine, adopts the dq rotating coordinate system, and sets the d-axis along the direction of the permanent magnet flux linkage of the direct-drive generator. S20: Based on the machine-side model, establish a grid-side small disturbance dynamic model for the direct-drive wind turbine. The grid-side small disturbance dynamic model is based on the grid-side topology and control loop. The control loop includes a voltage outer loop control model and a current inner loop control model, considering the small disturbance effect of the phase-locked loop on the grid connection point voltage. S30: Connect the machine side and the grid side through a back-to-back DC link, and convert the output power of the machine side converter into a constant power source. Ignore the influence of machine side dynamics on the grid side small disturbance dynamic model, and construct the initial impedance model of the grid side. S40: Based on the initial impedance model on the grid side, the active power output of the wind turbine is used as the independent variable to establish an impedance model of the wind power grid-connected system that includes the influence factor of the wind turbine output level. S50: Based on the impedance model of the wind power grid-connected system, calculate the equivalent impedance of the wind power grid-connected system under different active power output conditions, and evaluate the stability of the system under different active power output conditions.

2. The method of claim 1, wherein the wind power grid-connection system impedance modeling method considering wind power active power output is characterized by, In step S20, the current inner loop control model of the grid-side converter includes: ； In the formula, , These represent the d-axis and q-axis components of the grid-side converter output voltage, respectively. Let be the transfer function of the inner current loop. , These represent the d-axis and q-axis components of the grid-side converter output current reference value, respectively. , These are the d-axis and q-axis components of the grid-side converter output current, respectively. L is the fundamental angular frequency. g This is the grid-side filter inductor.

3. The method of claim 1, wherein the method further comprises: In step S20, the voltage outer loop control model includes: ； In the formula, , These represent the d-axis and q-axis components of the grid-side converter output current reference value, respectively. DC side voltage This is the reference value for the DC side voltage. This is the transfer function of the outer voltage loop.

4. The method of claim 1, wherein the method further comprises: In step S20, the control model that considers the small disturbance effect of the phase-locked loop on the grid connection point voltage includes: ； In the formula, This is the output angular frequency of the phase-locked loop. The transfer function of the phase-locked loop. This is the q-axis component of the grid-side converter output voltage after passing through a filter. The phase angle is the output phase angle of the phase-locked loop, and s is the differential symbol d / dt. , These are the proportional and integral control parameters of the phase-locked loop PI controller.

5. The method of claim 1, wherein, In step S20, the grid-side small disturbance dynamic model, considering small disturbances, describes the small-signal relationship between voltage and current of the grid-side converter in the dq rotating coordinate system, including: ； in, The dq-axis small-signal component of the voltage after filtering by the grid-side converter. This represents the dq-axis small-signal component of the grid-side converter output voltage. The small-signal component of the dq axis is the reference value for the output current of the grid-side converter. This refers to the small-signal component of the dq-axis output current of the grid-side converter. Let be the transfer function of the inner current loop. The transfer function for the filtering stage. This is the coupling impedance transfer function.

6. The method of claim 1, wherein the method further comprises: In step S20, the grid-side small disturbance dynamic model, which considers the influence of the phase-locked loop on the small disturbance voltage at the grid connection point, includes: ； In the formula, , These are the transfer functions characterizing the effect of small disturbances in the phase-locked loop on the grid-side terminal voltage and current. Let be the transfer function of the inner current loop. The coupling impedance transfer function, , The small-signal components of the grid-side converter output voltage and current along the dq axes in the system coordinate system are represented, respectively. The small-signal component of the dq axis is the reference value for the output current of the grid-side converter.

7. The method of claim 1, wherein the method further comprises: In step S30, the small-signal model of the DC link voltage obtained from the DC link topology and active power transmission relationship, which connects the generator side and the grid side via a back-to-back DC link, includes: ； In the formula, , These represent the d-axis and q-axis components of the grid-side converter output voltage, respectively. , These are the d-axis and q-axis components of the grid-side converter output current, respectively. dc For back-to-back DC link output current, U dc This is the voltage across capacitor C1 in the DC link. For small signal quantities of DC-side voltage, This represents the d-axis small-signal component of the grid-side converter output voltage. This represents the d-axis small-signal component of the grid-side converter output current. This represents the q-axis small-signal component of the grid-side converter output current. This represents the q-axis small-signal component of the grid-side converter output voltage.

8. The method of claim 1, wherein the method further comprises: In step S30, the small-signal model for obtaining the current loop reference value by connecting the machine side and the grid side through a back-to-back DC link includes: ； In the formula, To characterize the influence factor of output level on wind turbine impedance, This is the small-signal transfer function of the DC link current. This is the small-signal transfer function of the DC link voltage. This represents the dq-axis small-signal component of the grid-side converter output voltage. This refers to the small-signal component of the dq-axis output current of the grid-side converter. The small-signal component of the dq axis is the reference value for the output current of the grid-side converter. This is the voltage outer loop transfer function.

9. The method of claim 1, wherein the method further comprises: In step S40, the establishment of a wind power grid-connected system impedance model including the wind turbine output level influencing factor, wherein the model of the wind turbine output level influencing factor includes: ； In the formula, To characterize the influence factor of output level on wind turbine impedance, P dc U is the equivalent output power on the machine side. dc s represents the voltage across capacitor C1 in the DC link, where C1 is the capacitance across the back-to-back link, and s represents the differential symbol d / dt.

10. The method of claim 1, wherein the method further comprises: In step S40, based on the initial impedance model on the grid side, the active power output of the wind turbine is used as the independent variable to establish a wind power grid-connected system impedance model that includes the influence factor of the wind turbine output level. The equivalent impedance of the direct-drive wind turbine itself is defined as the ratio of voltage to current. The wind power grid-connected system impedance model includes: ； In the formula, Impedance model for wind power grid-connected system This represents the dq-axis small-signal component of the grid-side converter output voltage. This refers to the small-signal component of the dq-axis output current of the grid-side converter. Let be the transfer function of the inner current loop. Let the voltage outer loop transfer function be... The coupling impedance transfer function, , These are the transfer functions characterizing the effect of small disturbances in the phase-locked loop on the grid-side terminal voltage and current. To characterize the influence factor of output level on wind turbine impedance, This is the small-signal transfer function of the DC link current. This is the small-signal transfer function of the DC link voltage.

11. A wind power grid-connected system impedance modeling device considering wind power active power output, characterized in that, Using the method as described in any one of claims 1 to 10, comprising: The machine-side model building unit is used to build a machine-side model of the direct-drive wind turbine. The machine-side model is based on the machine-side topology and control links of the direct-drive wind turbine, adopts the dq rotating coordinate system, and sets the d-axis along the magnetic flux direction of the permanent magnet of the direct-drive generator. The grid-side small disturbance dynamic model establishment unit is used to establish a grid-side small disturbance dynamic model of the direct-drive wind turbine based on the turbine-side model. The grid-side small disturbance dynamic model is based on the grid-side topology and control loop. The control loop includes a voltage outer loop control model and a current inner loop control model, and considers the influence of phase-locked loop on small disturbances in the grid connection point voltage. The grid-side initial impedance model construction unit is used to connect the machine side and the grid side through a back-to-back DC link, to convert the output power of the machine-side converter into a constant power source, ignore the influence of machine-side dynamics on the grid-side small disturbance dynamic model, and construct the grid-side initial impedance model. The wind turbine output level impedance model improvement unit is used to establish a wind power grid-connected system impedance model that includes the wind turbine output level influence factor, based on the initial impedance model on the grid side and taking the active power output of the wind turbine as the independent variable. The system stability assessment unit is used to calculate the equivalent impedance of the wind power grid-connected system under different active power output conditions based on the impedance model of the wind power grid-connected system, and to assess the stability of the system under different active power output conditions.

12. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1-10.

13. A storage medium having stored thereon a computer program, characterized in that When the computer program is executed by a processor, it implements the method as described in any one of claims 1-10.

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