Impedance model based fast assessment method and system for grid stability of wind farm

Abstract

The application discloses a kind of based on impedance model's wind farm grid-connected stability fast evaluation method and system, it is related to power grid system technical field, S1, the physical model of wind farm grid-connected system is established;S2, the impedance model of wind farm and power grid is established;S3, suitable evaluation index is selected;S4, impedance matching analysis is carried out;S5, dynamic response characteristic is evaluated;S6, steady-state analysis is carried out;S7, the influence of grid connection on power grid is evaluated;S8, control strategy is designed, and the system is built based on the above method.The based on impedance model's wind farm grid-connected stability fast evaluation method and system, by constructing accurate wind farm and power grid impedance model, and combining multiple evaluation indexes and control strategies, comprehensive, fast evaluation of wind farm grid-connected stability is realized, potential stability problems can also be effectively identified and solved, and powerful support is provided for the safe, efficient grid connection of wind farm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power grid systems, in particular to a wind farm grid-connected stability rapid evaluation method and system based on impedance model. BACKGROUND

[0002] In the development process of wind farm grid-connected technology, how to accurately and quickly evaluate the stability between wind farm and power grid has always been the focus and difficulty of research. The traditional wind farm grid-connected stability evaluation method often relies on complex simulation models and long-term experimental data accumulation, which not only takes a long time, but also is difficult to reflect the dynamic interaction characteristics of wind farm and power grid in real time. In addition, the existing technology lacks in-depth analysis of the impedance characteristics of wind farm and power grid, which makes it difficult to accurately capture potential stability problems in the evaluation process. Especially in the context of high penetration rate of wind power into the power grid, the randomness and volatility of wind farm have increasingly significant impact on the stability of the power grid, and the traditional evaluation method has been difficult to meet the current demand of power system. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a wind farm grid-connected stability rapid evaluation method and system based on impedance model to solve the problems raised in the background.

[0004] To achieve the above purpose, the present application provides the following technical scheme: a wind farm grid-connected stability rapid evaluation method based on impedance model, comprising the following steps:

[0005] S1, establishing a physical model of the wind farm grid-connected system

[0006] Collect data of the wind farm grid-connected system, analyze the overall structure and parameters of the wind farm grid-connected system, and construct a physical model of the wind farm grid-connected system, which shows the interaction relationship between each component in the system and provides a framework for subsequent impedance modeling;

[0007] S2, establishing an impedance model of the wind farm and the power grid

[0008] The impedance model of the wind farm includes the impedance of the wind turbine system, the impedance of the converter and the total impedance of the wind farm; the impedance model of the power grid includes the impedance of the transmission line, the impedance of the transformer and the load impedance of the power grid. By calculating the impedance of the wind farm and the power grid, the complex impedance matrix of the wind farm grid-connected system is obtained;

[0009] S3, selecting appropriate evaluation indicators

[0010] Determine evaluation indicators to measure the stability of wind farm grid-connected systems. These indicators include voltage stability, frequency stability, and power factor. When selecting evaluation indicators, consider the characteristics of the wind farm and the requirements of the power grid. For example, select indicators such as voltage transient response, frequency response, and power fluctuation for analysis.

[0011] S4. Perform impedance matching analysis

[0012] By comparing the impedance of the wind farm and the grid, the stability of the system is judged. Impedance matching analysis is used to identify potential stability issues and ensure that the system remains stable across all operating frequency ranges.

[0013] S5. Evaluate dynamic response characteristics

[0014] Evaluate the wind farm's ability to respond to disturbances during grid connection. By simulating the actual operation of the wind farm and the grid, observe the system's response behavior under disturbances.

[0015] S6. Perform steady-state analysis

[0016] Evaluate the power balance, power factor, and voltage and frequency stability of the wind farm grid-connected system by calculating the system's power flow, load distribution, and voltage and frequency stability, and determine the system's stability under steady-state conditions;

[0017] S7. Evaluate the impact of grid connection on the power grid

[0018] Evaluate the impact of wind farm integration on the power grid, determine whether it will have a negative impact on grid stability, analyze grid voltage fluctuations, frequency changes, and system harmonics, and use power system simulation tools to simulate and analyze the grid after integration;

[0019] S8. Design control strategy

[0020] The control strategy includes wind turbine power control, converter current control, and system voltage and frequency regulation. By designing control algorithms such as PID control and fuzzy control, the system stability and performance are improved. Multiple simulation tests are conducted to determine the optimal control parameters and strategies.

[0021] To further optimize the technical solution, in step S1, the data of the wind farm grid-connected system includes wind speed and direction data, power generation data, wind turbine operation data, grid data, converter and electrical equipment data, environmental factor data, and fault and abnormality data.

[0022] To further optimize this technical solution, in step S2, when establishing the impedance model of the wind farm:

[0023] Impedance of the fan system Expressed as:

[0024]

[0025] wherein, is the resistance of the wind turbine, is the reactance of the wind turbine;

[0026] impedance of the converter is expressed as:

[0027]

[0028] wherein, is the resistance of the converter, is the reactance of the converter;

[0029] total impedance of the wind farm is calculated by the parallel impedance of the wind turbine and the converter:

[0030]

[0031] when establishing the impedance model of the power grid:

[0032] impedance of the transmission line is expressed as:

[0033]

[0034] wherein, is the resistance of the transmission line, is the reactance of the transmission line;

[0035] impedance of the transformer is expressed as:

[0036]

[0037] wherein, is the resistance of the transformer, is the reactance of the transformer;

[0038] load impedance of the power grid is expressed as:

[0039]

[0040] total impedance of the power grid is expressed as:

[0041]

[0042] when calculating the complex impedance matrix of the wind farm grid-connected system:

[0043] The complex impedance matrix of the wind farm and the power grid is represented as follows:

[0044]

[0045] wherein, is the impedance of the interface between the wind farm and the power grid.

[0046] Further optimization of the technical solution, in step S4, the wind farm impedance analysis model and the power grid impedance analysis model are constructed, and the frequency domain analysis is performed to check the impedance characteristics of the system at different frequencies;

[0047] The wind farm impedance analysis model is shown as follows:

[0048]

[0049] wherein, is the impedance of the wind farm, wherein, is the complex frequency variable in the Laplace transform, is the DC resistance of the wind farm, is the inductance of the wind farm, is the time constant of the wind farm;

[0050] The power grid impedance analysis model is shown as follows:

[0051]

[0052] wherein, is the impedance of the power grid, is the DC resistance of the power grid, is the inductance of the power grid, is the time constant of the power grid, is the capacitance of the power grid;

[0053] In the frequency domain analysis, different frequencies are selected, the wind farm impedance analysis model and the power grid impedance analysis model are used to calculate the impedance of the wind farm and the power grid, and the frequency response graph is drawn to compare the matching degree of the wind farm impedance and the power grid impedance.

[0054] Further optimization of the technical solution, in step S5, when evaluating the response capability of the wind farm to the disturbance in the grid connection process, the wind farm dynamic response model and the frequency domain response model are used for evaluation;

[0055] The wind farm dynamic response model is shown as follows:

[0056]

[0057] wherein, is the system voltage at time ) is the change of the wind farm output power, ( ) is the wind farm output power at time ( ) is the load power, ( ) is the reference voltage, ( ) is the equivalent impedance of the wind farm;

[0058] The frequency domain response model is as follows:

[0059]

[0060] wherein, ( ) is the frequency domain response function, ( ) is the angular frequency, ( ) is the time constant of the wind farm system;

[0061] Through the frequency domain analysis, the stability of the system at different frequencies is understood.

[0062] Further optimization of the technical solution, in the step S6, the system is built-in power balance model and voltage stability model to evaluate the stability of the wind farm and the power grid in the long-term operation;

[0063] The power balance model is as follows:

[0064]

[0065] wherein, ( ) is the output power of the wind farm, ( ) is the output power of other power generation equipment, ( ) is the load power demand of the power grid, ( ) is the power loss in the system;

[0066] The voltage stability model is as follows:

[0067]

[0068] wherein, ( ) is the bus voltage of the power grid, ( ) and ( ) are the active and reactive power of the load respectively, ( ) is the impedance of the bus of the power grid.

[0069] Further optimization of the technical solution, in the step S7, when the simulation analysis is carried out, the specific process includes the following process:

[0070] ​Build a simulation model, in the power system simulation tool DIgSILENT PowerFactory, PSS / E, MATLAB / Simulink, build a wind farm model, a power grid model;

[0071] Set up a simulation scenario, simulate the grid-connected operation of the wind farm under normal wind speed and load conditions, and set up different fault and disturbance scenarios such as sudden change of wind speed, sudden increase and decrease of load, and power grid fault to observe the response of the wind farm after grid connection;

[0072] Perform simulation analysis, voltage fluctuation analysis, frequency change analysis and harmonic analysis.

[0073] Further optimize the technical solution, in step S8, the control strategy includes:

[0074] Power control of the wind turbine, based on wind speed prediction and power regulation algorithm of power grid demand, such as combination of maximum power point tracking MPPT and power limiting strategy, to ensure that the output of the wind turbine matches the demand of the power grid;

[0075] Current control of the converter, design the current control loop of the converter, including d-q axis current control, use PI controller to quickly respond to the current demand of the power grid;

[0076] Voltage and frequency regulation, design active regulation strategy for voltage and frequency, such as using droop control or virtual synchronous generator VSG technology to simulate the characteristics of traditional generators.

[0077] A wind farm grid-connected stability rapid evaluation system based on impedance model is built based on the above-mentioned wind farm grid-connected stability rapid evaluation method based on impedance model, including data collection module, model construction module, evaluation index selection module, impedance matching analysis module, dynamic response evaluation module, steady-state analysis module, power grid influence evaluation module and control strategy design module.

[0078] The data collection module receives data from the wind farm and the power grid;

[0079] The model construction module constructs the physical model of the wind farm grid-connected system and the impedance model of the wind farm and the power grid;

[0080] The evaluation index selection module selects evaluation indexes based on user requirements and wind farm characteristics;

[0081] The impedance matching analysis module outputs impedance matching analysis results based on the impedance model of the wind farm and the power grid;

[0082] The dynamic response evaluation module evaluates the response capability of the wind farm to disturbances during grid connection;

[0083] A steady-state analysis module performs steady-state analysis of the system;

[0084] A grid impact assessment module assesses the impact of the wind farm grid connection on the grid, including grid voltage fluctuations, frequency changes, and harmonics.

[0085] A control strategy design module designs the control strategy of the wind farm, including power control of the wind turbine, current control of the converter, and voltage and frequency regulation of the system.

[0086] To further optimize the technical solution, the system further comprises a data management module for recording all assessment data, simulation results and test results and performing data backup, and generating reports based on the assessment data, simulation results and test results.

[0087] Compared with the prior art, the present application provides a wind farm grid connection stability rapid assessment method and system based on impedance model, which has the following beneficial effects:

[0088] The wind farm grid connection stability rapid assessment method and system based on impedance model, by constructing accurate wind farm and grid impedance models, combined with various assessment indicators and control strategies, realizes comprehensive and rapid assessment of wind farm grid connection stability. This method not only improves the accuracy and real-time performance of the assessment, but also effectively identifies and solves potential stability problems, providing strong support for the safe and efficient grid connection of wind farms. At the same time, by designing reasonable control strategies, the stability and performance of the wind farm grid connection system are further improved, promoting the large-scale development and utilization of wind power resources. BRIEF DESCRIPTION OF DRAWINGS

[0089] Figure 1 A flowchart of a wind farm grid connection stability rapid assessment method based on impedance model according to the present application;

[0090] Figure 2 A classification diagram of control strategies in a wind farm grid connection stability rapid assessment method based on impedance model according to the present application;

[0091] Figure 3 A flowchart of simulation analysis in a wind farm grid connection stability rapid assessment method based on impedance model according to the present application;

[0092] Figure 4 A structural flowchart of a wind farm grid connection stability rapid assessment system based on impedance model according to the present application. DETAILED DESCRIPTION

[0093] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0094] Embodiment one: please refer to Figure 1 A rapid evaluation method for wind farm grid-connected stability based on impedance model, comprising the following steps:

[0095] S1, establishing a physical model of a wind farm grid-connected system

[0096] Data of the wind farm grid-connected system are collected, overall structure and parameter analysis of the wind farm grid-connected system are performed, and a physical model of the wind farm grid-connected system is constructed. The physical model shows the interaction relationship between each component in the system, providing a framework for subsequent impedance modeling. All models need accurate parameter settings, such as wind speed, generator rated power, control parameters of the converter, impedance values of the power grid, etc. These parameters will affect the stability analysis results of the system.

[0097] In this embodiment, the data of the wind farm grid-connected system include wind speed and wind direction data, power generation data, wind turbine operation data, power grid data, converter and electrical equipment data, environmental factor data, and fault and abnormal data. The above data specifically include:

[0098] Wind speed and wind direction data: Wind speed data reflect the wind energy resource situation of the area where the wind farm is located, which is a key factor for evaluating the power generation potential and efficiency of the wind farm. Wind direction data have important influence on the layout optimization of the wind farm and the control strategy of the wind turbine, because it determines the main source direction of wind energy.

[0099] Power generation data: Power generation data record the actual power generation of the wind farm under different wind speed and wind direction conditions, which is an important indicator for evaluating the operation performance of the wind farm.

[0100] Wind turbine operation data: including the speed of the wind turbine, the blade angle, the mechanical stress, etc. These data are crucial for monitoring the operation state of the wind turbine, predicting the maintenance needs, and optimizing the performance of the wind turbine.

[0101] Power grid data: Power grid data include voltage, frequency, power factor, etc. of the power grid, which reflect the stability and operation state of the power grid, and have important influence on the stable operation of the wind farm after grid connection.

[0102] Converter and electrical equipment data: The operating data of the converter, such as current, voltage, power factor, etc., are of great significance for evaluating the grid-connected performance and power quality of the wind farm.

[0103] At the same time, the operating data of other electrical equipment in the wind farm, such as transformers, circuit breakers, cables, etc., are also important basis for evaluating system stability and safety.

[0104] Environmental factor data: In addition to wind speed and wind direction, environmental factors such as temperature, humidity, air pressure, etc. may also affect the operation of the wind farm. These data help to more comprehensively evaluate the operating environment and performance of the wind farm.

[0105] Fault and abnormal data: Record the faults and abnormal conditions that occur during the grid connection process of the wind farm, such as equipment failure, grid fluctuation, etc. These data are of great significance for analyzing fault causes, developing response measures and optimizing system performance.

[0106] In the scene application, the collected data types are presented in the form of Table 1.

[0107]

[0108] Table 1

[0109] S2, establish the impedance model of the wind farm and the grid

[0110] The impedance model of the wind farm includes the impedance of the wind turbine system, the impedance of the converter and the total impedance of the wind farm. The impedance model of the grid includes the impedance of the transmission line, the impedance of the transformer and the load impedance of the grid. By calculating the impedance of the wind farm and the grid, the complex impedance matrix of the wind farm grid-connected system is obtained.

[0111] In this embodiment, when establishing the impedance model of the wind farm:

[0112] Impedance of the wind turbine system is represented as:

[0113]

[0114] wherein, R is the resistance of the wind turbine, X is the reactance of the wind turbine;

[0115] Impedance of the converter is represented as:

[0116]

[0117] wherein, R is the resistance of the converter, X is the reactance of the converter;

[0118] Total impedance of the wind farm The calculation is made by means of the parallel impedance of the wind turbine and the converter:

[0119]

[0120] When establishing the impedance model of the grid:

[0121] Impedance of the transmission line is expressed as:

[0122]

[0123] wherein, is the resistance of the transmission line, is the reactance of the transmission line;

[0124] Impedance of the transformer is expressed as:

[0125]

[0126] wherein, is the resistance of the transformer, is the reactance of the transformer;

[0127] Load impedance of the grid is expressed as:

[0128]

[0129] Total impedance of the grid is expressed as:

[0130]

[0131] When calculating the complex impedance matrix of the wind farm grid-connection system:

[0132] is the complex impedance matrix of the wind farm and the grid, the matrix being expressed as:

[0133]

[0134] wherein, is the impedance of the interface of the wind farm and the grid.

[0135] Based on the above model, when calculating the complex impedance matrix of the system, the following steps are used:

[0136] The respective impedance models of the wind farm and the grid are calculated;

[0137] These impedance models are combined into a matrix, taking into account the interface impedance of the wind farm and the grid;

[0138] Through matrix operations (such as inversion or eigenvalue analysis), the complex impedance characteristics of the system can be obtained for subsequent stability analysis.

[0139] S3. Choose appropriate evaluation metrics

[0140] Stability assessment relies on a series of indicators to measure system stability. These indicators include voltage stability, frequency stability, and power factor. When selecting evaluation indicators, the characteristics of the wind farm and the requirements of the power grid should be considered. For example, indicators such as voltage transient response, frequency response, and power fluctuation can be analyzed. The selection of each indicator should be based on the actual application scenario and system requirements to ensure that the evaluation results truly reflect system stability.

[0141] S4. Perform impedance matching analysis

[0142] By comparing the impedance of the wind farm and the grid, the stability of the system is judged. Impedance matching analysis is used to identify potential stability issues and ensure that the system remains stable across all operating frequency ranges.

[0143] In this embodiment, a wind farm impedance analysis model and a power grid impedance analysis model are constructed, and frequency domain analysis is performed to check the impedance characteristics of the system at different frequencies;

[0144] The wind farm impedance analysis model is as follows:

[0145]

[0146] in,( ) is the impedance of the wind farm, where ( ) is the complex frequency variable in Laplace transform, ( ) is the DC resistance of the wind farm (such as the internal resistance of the wind turbine), ( ) is the inductance of the wind farm (such as the inductance of the wind turbine motor), ( ) is the time constant of the wind farm (representing the dynamic response characteristics of the system).

[0147] When the model is used:

[0148] Impedance calculation: Substitute the actual wind farm parameters into the model to calculate the wind farm impedance at different frequencies ( The frequency can be changed by changing ( ) to achieve this.

[0149] Frequency Domain Analysis: Plot the frequency response of the wind farm impedance to examine how it changes at different frequencies. This can help identify if there are sudden impedance changes at certain frequencies that could affect system stability.

[0150] The grid impedance analysis model is shown as follows:

[0151]

[0152] where ( ) is the impedance of the grid, ( ) is the DC resistance of the grid, ( ) is the inductance of the grid, ( ) is the time constant of the grid, and ( ) is the capacitance of the grid.

[0153] When the model is used:

[0154] Impedance calculation: By actually measuring or estimating the grid parameters, the impedance of the grid at different frequencies ( ) is calculated by substituting the model.

[0155] Frequency domain analysis: Draw the frequency response graph of the grid impedance to analyze its characteristics at different frequencies. In particular, the capacitance part of the grid will have a significant impact on high-frequency signals.

[0156] In frequency domain analysis, different frequencies are selected, and the wind farm impedance analysis model and the grid impedance analysis model are used to calculate the impedance of the wind farm and the grid, and the frequency response graph is drawn to compare the matching degree of the impedance of the wind farm and the grid.

[0157] The steps of frequency domain analysis include:

[0158] Impedance calculation: Select different frequencies , and use the above model to calculate the impedance of the wind farm and the grid. Assume that the DC resistance , inductance , time constant of the wind farm.

[0159] For the grid, assume , inductance , capacitance , time constant .

[0160] Draw the frequency response graph: Use the calculated impedance data to draw the frequency response graph. Analyze the change of the amplitude and phase of the impedance with frequency to determine the stability of the system.

[0161] Amplitude response: It can help to judge the power absorption capacity of the system at different frequencies. The sudden change of impedance amplitude may cause system resonance.

[0162] Phase response: The change of phase can help to judge the phase margin of the system and determine whether the system is stable under frequency change.

[0163] Impedance matching: Compares the wind farm impedance to the grid impedance. Significant differences in impedance within the primary operating frequency band can lead to power oscillations or stability issues. Impedance matching can be optimized by adjusting the wind farm's control strategy or supporting grid facilities.

[0164] S5. Evaluate dynamic response characteristics

[0165] Evaluate the wind farm's ability to respond to disturbances during the grid connection process, and observe the system's response behavior under disturbances by simulating the actual operation of the wind farm and the power grid.

[0166] In this embodiment, when evaluating the response capability of a wind farm to disturbances during the grid connection process, a wind farm dynamic response model and a frequency domain response model are used for evaluation;

[0167] The wind farm dynamic response model is as follows:

[0168]

[0169] in,( ) is the system voltage at time ( ) changes, ( ) is the wind farm at time ( ) of power generation, ( ) is the load power, ( ) is the reference voltage, ( ) is the equivalent impedance of the wind farm;

[0170] The frequency domain response model is as follows:

[0171]

[0172] in,( ) is the frequency domain response function, ( ) is the angular frequency, ( ) is the time constant of the wind farm system;

[0173] Through frequency domain analysis, we can understand the stability of the system at different frequencies.

[0174] When using,

[0175] Time-domain simulation: Use the wind farm dynamic response model to calculate voltage variations under actual wind speed and load fluctuations. This helps identify the system's dynamic response characteristics under disturbances and predict possible voltage deviations.

[0176] Frequency Domain Analysis: Apply frequency domain response models for frequency domain analysis to assess the stability of the system at different frequencies. This helps identify possible oscillation modes and dynamic instability issues, ensuring stable operation of the system under various frequency conditions.

[0177] S6, Steady-state analysis

[0178] The power balance, power factor, and voltage and frequency stability of the wind farm grid-connected system are evaluated by calculating the power flow, load distribution, and voltage and frequency stability of the system to determine the stability of the system under steady-state conditions.

[0179] In this embodiment, the system is built-in with a power balance model and a voltage stability model to evaluate the stability of the wind farm and the grid in long-term operation;

[0180] The power balance model is as follows:

[0181]

[0182] where (Pwind) is the output power of the wind farm, (Pother) is the output power of other power generation equipment, (Pload) is the load power demand of the grid, and (Ploss) is the power loss in the system. This model is used to ensure that all power inputs and outputs in the system are equal under steady-state conditions.

[0183] By collecting the output power of the wind farm, the power of other power generation equipment, the load demand, and the system loss data, and substituting them into the model, it can be verified whether the system reaches power balance, and thus whether the system remains stable under steady-state conditions. If the power is not balanced, the output of the wind farm or the configuration of other power generation equipment may need to be adjusted to achieve balance.

[0184] The voltage stability model is as follows:

[0185]

[0186]

[0187] where (Vbus) is the bus voltage of the grid, (Pload) and (Qload) are the active and reactive power of the load, respectively, and (Zbus) is the impedance of the grid bus. This model is used to evaluate whether the bus voltage is within the expected range, thereby ensuring the voltage stability of the grid.

[0188]

[0189] ​​​​​​​​In the steady-state analysis, the active and reactive power of the load and the grid impedance value are substituted into the model to calculate the voltage of the grid bus. If the calculated voltage deviates from the expected range, it may cause voltage instability, and the grid needs to be adjusted or the load distribution needs to be adjusted.

[0190] S7, evaluate the impact of grid connection on the grid

[0191] Evaluate the impact of wind farm grid connection on the grid, determine whether it will have a negative impact on the stability of the grid, analyze the voltage fluctuation, frequency change and system harmonics of the grid, use power system simulation tools to simulate and analyze the grid after grid connection.

[0192] As shown in Figure 3 , in this embodiment, when performing simulation analysis, the following processes are included:

[0193] Construct a simulation model, construct a wind farm model and a grid model in the power system simulation tools DIgSILENT PowerFactory, PSS / E, MATLAB / Simulink;

[0194] Set the simulation scene, simulate the grid connection operation of the wind farm under the condition of normal wind speed and load, and set different fault and disturbance scenes, such as sudden change of wind speed, sudden increase and decrease of load, and grid fault, to observe the response of the wind farm after grid connection;

[0195] Perform simulation analysis, perform voltage fluctuation analysis, frequency change analysis and harmonic analysis.

[0196] S8, design control strategy

[0197] The control strategy includes power control of the wind turbine, current control of the converter, and voltage and frequency regulation of the system, through the design of control algorithm such as PID control and fuzzy control, to improve the stability and performance of the system, and perform multiple simulation tests to determine the optimal control parameters and strategy.

[0198] As shown in Figure 2 , in this embodiment, the control strategy includes:

[0199] Power control of the wind turbine, based on wind speed prediction and power regulation algorithm of grid demand, such as combination of maximum power point tracking MPPT and power limiting strategy, to ensure that the output of the wind turbine matches the demand of the grid;

[0200] Current control of the converter, design the current control loop of the converter, including d-q axis current control, use PI controller to quickly respond to the current demand of the grid;

[0201] Voltage and frequency regulation, active regulation strategies for voltage and frequency design, such as using droop control or virtual synchronous generator VSG technology to simulate the characteristics of traditional generators.

[0202] Embodiment two: please refer to Figure 4 A wind farm grid-connected stability rapid evaluation system based on impedance model is built based on the wind farm grid-connected stability rapid evaluation method based on impedance model described in embodiment one, including data collection module, model construction module, evaluation index selection module, impedance matching analysis module, dynamic response evaluation module, steady state analysis module, grid impact evaluation module and control strategy design module.

[0203] The data collection module receives data from the wind farm and the power grid.

[0204] The model construction module constructs the physical model of the wind farm grid-connected system and the impedance model of the wind farm and the power grid.

[0205] The evaluation index selection module selects evaluation indexes based on user requirements and wind farm characteristics.

[0206] The impedance matching analysis module outputs impedance matching analysis results based on the impedance model of the wind farm and the power grid.

[0207] The dynamic response evaluation module evaluates the response capability of the wind farm to disturbances during the grid connection process.

[0208] The steady state analysis module performs steady state analysis of the system.

[0209] The grid impact evaluation module evaluates the impact of wind farm grid connection on the power grid, including power grid voltage fluctuation, frequency change and harmonic.

[0210] The control strategy design module designs the control strategy of the wind farm, including power control of the wind turbine, current control of the converter and voltage and frequency regulation of the system.

[0211] In this embodiment, the system further includes a data management module for recording all evaluation data, simulation results and test results and performing data backup, and generating reports based on evaluation data, simulation results and test results.

[0212] By recording all evaluation data, simulation results and test results, detailed analysis and summary can be performed to identify potential problems and improvement points in the system and provide basis for future optimization. In addition, the recorded results generate reports, which are shared with relevant departments or institutions for further review and verification.

[0213] At the same time, with the continuous development of wind farms and power grids in technology and operating environment, it is necessary to continuously optimize and update the evaluation method. The system regularly updates the evaluation method, model and control strategy according to new technological progress and operating experience to adapt to changing conditions and requirements. The continuously optimized method includes improving the accuracy of the model, introducing new control technology, and updating the evaluation index, etc. Ensure that the evaluation method keeps pace with the times and maintains its effectiveness and reliability in practical applications.

[0214] The beneficial effects of the present application are:

[0215] The impedance model-based wind farm grid-connected stability rapid evaluation method and system realizes comprehensive and rapid evaluation of wind farm grid-connected stability by constructing accurate wind farm and grid impedance models and combining various evaluation indexes and control strategies. This method not only improves the accuracy and real-time performance of the evaluation, but also effectively identifies and solves potential stability problems, providing strong support for the safe and efficient grid connection of wind farms. At the same time, by designing reasonable control strategies, the stability and performance of the wind farm grid-connected system are further improved, promoting the large-scale development and utilization of wind power resources.

[0216] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the skilled person in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0217] Although embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for rapid assessment of wind farm grid connection stability based on impedance model, characterized in that: The following steps are involved: S1. Establish a physical model of the wind farm grid-connected system Collect data on the wind farm grid-connected system, analyze its overall structure and parameters, and build a physical model of the wind farm grid-connected system. The physical model demonstrates the interaction between the various components in the system and provides a framework for subsequent impedance modeling. S2. Establish impedance models for wind farms and power grids The impedance model of the wind farm includes the impedance of the wind turbine system, the impedance of the converter, and the total impedance of the wind farm. The impedance model of the power grid includes the impedance of the transmission line, the impedance of the transformer, and the load impedance of the power grid. By calculating the impedance of the wind farm and the power grid, the complex impedance matrix of the wind farm grid-connected system is obtained. S3. Choose appropriate evaluation metrics Determine evaluation indicators to measure the stability of wind farm grid-connected systems, including voltage stability, frequency stability, and power factor. When selecting evaluation indicators, consider the characteristics of the wind farm and the requirements of the power grid, including selecting indicators for voltage transient response, frequency response, and power fluctuation for analysis. S4. Perform impedance matching analysis By comparing the impedance of the wind farm and the grid, the stability of the system is judged. Impedance matching analysis is used to identify potential stability issues and ensure that the system remains stable across all operating frequency ranges. Construct wind farm impedance analysis models and grid impedance analysis models, and perform frequency domain analysis to examine the impedance characteristics of the system at different frequencies; The wind farm impedance analysis model is as follows: ； in, is the impedance of the wind farm, where is the complex frequency variable in the Laplace transform, is the DC resistance of the wind farm, is the inductance of the wind farm, is the time constant of the wind farm; The grid impedance analysis model is as follows: ； in, is the impedance of the grid, is the DC resistance of the grid, is the inductance of the grid, is the time constant of the grid, is the capacitance of the grid; In frequency domain analysis, different frequencies are selected, and the wind farm impedance analysis model and the grid impedance analysis model are used to calculate the impedance of the wind farm and the grid. A frequency response diagram is then drawn to compare the matching degree between the wind farm impedance and the grid impedance. S5. Evaluate dynamic response characteristics Evaluate the wind farm's ability to respond to disturbances during grid connection. By simulating the actual operation of the wind farm and the grid, observe the system's response behavior under disturbances. S6. Perform steady-state analysis Evaluate the power balance, power factor, and voltage and frequency stability of the wind farm grid-connected system by calculating the system's power flow, load distribution, and voltage and frequency stability, and determine the system's stability under steady-state conditions; S7. Evaluate the impact of grid connection on the power grid Evaluate the impact of wind farm integration on the power grid, determine whether it will have a negative impact on grid stability, analyze grid voltage fluctuations, frequency changes, and system harmonics, and use power system simulation tools to simulate and analyze the grid after integration; S8. Design control strategy The control strategy includes wind turbine power control, converter current control, and system voltage and frequency regulation. By designing control algorithms, including PID control and fuzzy control, the system stability and performance are improved. Multiple simulation tests are conducted to determine the optimal control parameters and strategies.

2. A method for rapid assessment of wind farm grid connection stability based on impedance model according to claim 1, characterized in that: In step S1, the data of the wind farm grid-connected system includes wind speed and direction data, power generation data, wind turbine operation data, grid data, converter and electrical equipment data, Environmental factor data as well as fault and anomaly data.

3. The method for rapid assessment of wind farm grid connection stability based on impedance model according to claim 1, characterized in that: In step S2, when establishing the impedance model of the wind farm: Impedance of the fan system Expressed as: ； in, is the resistance of the fan, is the reactance of the wind turbine; Impedance of the converter Expressed as: ； in, is the resistance of the converter, is the reactance of the converter; Total impedance of the wind farm The parallel impedance of the wind turbine system and the converter is calculated as follows: ； When establishing the impedance model of the power grid: Impedance of transmission lines Expressed as: ； in, is the resistance of the transmission line, is the reactance of the transmission line; Transformer impedance Expressed as: ； in, is the resistance of the transformer, is the reactance of the transformer; Load impedance of the power grid Expressed as: ； Total impedance of the grid Expressed as: ； When calculating the complex impedance matrix of the wind farm grid-connected system: is the complex impedance matrix of the wind farm grid-connected system, and the matrix is ​​expressed as: ； in, is the impedance of the interface between the wind farm and the grid.

4. The method for rapid assessment of wind farm grid connection stability based on impedance model according to claim 1, characterized in that: In step S5, when evaluating the response capability of the wind farm to disturbances during the grid connection process, the wind farm dynamic response model and the frequency domain response model are used for evaluation; The wind farm dynamic response model is as follows: ； in, is the system voltage at time The amount of change, The wind farm is at time The power generation capacity, is the load power, is the reference voltage, is the equivalent impedance of the wind farm; The frequency domain response model is as follows: ； in, is the frequency domain response function, is the angular frequency, is the time constant of the wind farm; Through frequency domain analysis, we can understand the stability of the system at different frequencies.

5. The method for rapid assessment of wind farm grid connection stability based on impedance model according to claim 1, characterized in that: In step S6, the system has a built-in power balance model and a voltage stability model to evaluate the stability of the wind farm and the power grid in long-term operation; The power balance model is as follows: ； in, is the output power of the wind farm, is the output power of other power generation equipment, is the load power demand of the grid, is the power loss in the system; The voltage stability model is as follows: ； in, is the grid bus voltage, and are the active and reactive powers of the load, is the impedance of the grid bus.

6. The method for rapid assessment of wind farm grid connection stability based on impedance model according to claim 1, characterized in that: In step S7, when performing simulation analysis, the following process is specifically included: Build simulation models, including wind farm models and power grid models using power system simulation tools such as DIgSILENT PowerFactory, PSS / E, and MATLAB / Simulink; Set up simulation scenarios to simulate the grid-connected operation of wind farms under normal wind speed and load conditions, and set up different fault and disturbance scenarios, including sudden changes in wind speed, sudden increases and decreases in load, and grid faults, to observe the response of wind farms after grid connection; Perform simulation analysis to conduct voltage fluctuation analysis, frequency variation analysis, and harmonic analysis.

7. The method for rapid assessment of wind farm grid connection stability based on impedance model according to claim 1, characterized in that: In step S8, in the control strategy: Wind turbine power control, including a power regulation algorithm based on wind speed forecast and grid demand, including maximum power point tracking (MPPT) combined with a power limit strategy to ensure that wind turbine output matches grid demand; Converter current control: Design the converter's current control loop, including dq axis current control, using a PI controller to quickly respond to grid current demand; Voltage and frequency regulation, designing active voltage and frequency regulation strategies, including using droop control or virtual synchronous generator (VSG) technology to simulate the characteristics of traditional generators.

8. A wind farm grid-connected stability rapid assessment system based on an impedance model, constructed based on the wind farm grid-connected stability rapid assessment method based on an impedance model according to any one of claims 1 to 7, characterized in that: It includes data collection module, model building module, evaluation index selection module, impedance matching analysis module, dynamic response evaluation module, steady-state analysis module, power grid impact assessment module and control strategy design module; Data collection module, receiving data from wind farms and power grids; Model building module, which builds the physical model of the wind farm grid-connected system and the impedance model of the wind farm and the power grid; Evaluation indicator selection module, which selects evaluation indicators based on user needs and wind farm characteristics; Impedance matching analysis module, based on the impedance model of wind farm and power grid, outputs impedance matching analysis results; Dynamic response assessment module, which evaluates the wind farm's ability to respond to disturbances during the grid connection process; Steady-state analysis module, to perform steady-state analysis of the system; Grid impact assessment module, which evaluates the impact of wind farm integration on the grid, including grid voltage fluctuations, frequency changes, and harmonics; The control strategy design module designs the control strategy of the wind farm, including the power control of the wind turbine, the current control of the converter, and the voltage and frequency regulation of the system.

9. A wind farm grid connection stability rapid assessment system based on impedance model according to claim 8, characterized in that: The system also includes a data management module for recording all evaluation data, simulation results and test results and performing data backup, and generating reports based on the evaluation data, simulation results and test results.

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