An electrical automation control system for hybrid power grids and an oscillation suppression method

Abstract

The application provides an electrical automation control system and an oscillation suppression method for a hybrid power grid. The system collects voltage phasors and current phasors of each wind farm grid-connected point in the hybrid power grid; determines the power frequency impedance variation of each wind farm grid-connected point according to all voltage phasors and current phasors in the power frequency band; determines the oscillation threshold when the hybrid power grid is in sub-super synchronous oscillation according to the oscillation frequency and output power of each wind farm grid-connected point, and screens out the dominant oscillation source when the state switching causes sub-super synchronous oscillation from each wind farm grid-connected point according to the oscillation threshold and all power frequency impedance variations; suppresses the weak grid interaction instability in the sub-synchronous frequency band of the wind farm where the dominant oscillation source is located, and blocks the super-synchronous frequency band oscillation caused by the resonance between the dominant oscillation source and the equipment in the hybrid power grid during the state transition. The scheme can suppress the sub-super synchronous oscillation when the hybrid power grid fails to switch to an island state.

Description

Technical Field

[0001] This application relates to the field of electrical automation control technology, and more specifically, to an electrical automation control system and oscillation suppression method for a hybrid power grid. Background Technology

[0002] A hybrid power grid is a new type of power system structure that combines AC and DC subgrids. It can effectively integrate distributed energy resources and realize flexible allocation of electrical energy. Electrical automation control of hybrid power grids refers to the use of automation technology, information technology, etc. to monitor, control and coordinate various electrical equipment and systems in the hybrid power grid in order to achieve the stability, efficiency and reliability of the power grid.

[0003] The dense integration of power equipment, weak damping characteristics, and multi-source heterogeneous interaction in hybrid power grids can trigger severe sub-supersynchronous oscillations. Furthermore, islanded operation during hybrid power grid faults further lowers the trigger threshold for sub-supersynchronous oscillations, amplifying their harmful effects. Current technologies typically suppress oscillations by adjusting the output of suppression devices based on converter oscillation voltage and current, or by collecting the transmission power of the grid connection point's tie line to identify oscillations and adjust the grid voltage amplitude. However, simultaneously measuring sub-supersynchronous oscillations requires wideband measurement equipment. Frequency domain analysis of wideband oscillation signals is prone to problems such as spectral leakage and the picket fence effect, leading to reduced measurement accuracy and affecting the accurate location of the oscillation source. Therefore, how to suppress sub-supersynchronous oscillations during the islanded operation of a hybrid power grid during a fault has become a pressing problem for the industry. Summary of the Invention

[0004] This application provides an electrical automation control system and oscillation suppression method for a hybrid power grid, which can suppress subsynchronous oscillations when the hybrid power grid switches to islanded state due to a fault.

[0005] In a first aspect, this application provides an oscillation suppression method for a hybrid power grid, used by an electrical automation control system to suppress oscillations in the hybrid power grid, wherein the hybrid power grid includes multiple wind farm grid connection points, and the hybrid power grid switches from a grid-connected state to an islanded state and oscillates during a fault, comprising the following steps:

[0006] Collect voltage and current phasors at the grid connection points of each wind farm in the hybrid power grid;

[0007] The change in power frequency impedance at each wind farm grid connection point is determined based on all voltage and current phasors in the power frequency band when the state switch triggers sub-supersynchronous oscillation.

[0008] The oscillation threshold of the hybrid power grid during sub-supersynchronous oscillation is determined by the oscillation frequency and output power of each wind farm grid connection point. Based on the oscillation threshold and all power frequency impedance changes, the dominant oscillation source that causes sub-supersynchronous oscillation during state switching is screened from each wind farm grid connection point.

[0009] Weak grid interaction instability suppression is performed on the subsynchronous frequency band of the wind farm where the dominant oscillation source is located, and the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and equipment in the hybrid grid during state transition is blocked.

[0010] In some embodiments, determining the change in power frequency impedance at each wind farm grid connection point during sub-supersynchronous oscillation caused by state switching based on all voltage and current phasors in the power frequency band specifically includes:

[0011] Determine the steady-state period of the hybrid power grid prior to the fault;

[0012] Determine the fault period of the hybrid power grid after the fault occurs;

[0013] The steady-state power frequency impedance of each wind power grid connection point before the fault is determined based on all voltage phasors and current phasors of the power frequency band and the steady-state time period.

[0014] Based on all voltage phasors and current phasors of the power frequency band and the fault period, determine the fault power frequency impedance of each wind power grid connection point when the sub-supersynchronous oscillation is triggered.

[0015] The change in power frequency impedance at each wind farm grid connection point is determined based on all steady-state power frequency impedances and all fault power frequency impedances when the state switch triggers sub-supersynchronous oscillation.

[0016] In some embodiments, determining the oscillation threshold during the sub-supersynchronous oscillation of the hybrid power grid based on the oscillation frequency and output power of each wind farm's grid connection point specifically includes:

[0017] Spectral analysis was performed on the collected voltage and current phasors to obtain multiple spectral distributions;

[0018] Multiple sub-supersynchronous frequency components are extracted from all the spectrum distributions and used as the oscillation frequency of sub-supersynchronous oscillation at each wind power grid connection point.

[0019] The output power of each wind farm's grid connection point is determined based on the voltage and current phasors at the time of the fault.

[0020] The oscillation threshold of the hybrid power grid is obtained by correlating the characteristics of subsynchronous oscillation at each wind farm grid connection point based on all oscillation frequencies and all output power.

[0021] In some embodiments, the dominant oscillation source for subsynchronous oscillations triggered by state switching is screened from each wind farm grid connection point based on the oscillation threshold and all power frequency impedance changes, specifically including:

[0022] Select a wind farm grid connection point as the selected grid connection point, and compare the power frequency impedance change of the selected grid connection point with the oscillation threshold.

[0023] If the change in power frequency impedance at the selected grid connection point is greater than the oscillation threshold, then the selected grid connection point will be used as a candidate oscillation source.

[0024] Continue to identify candidate oscillation sources among the remaining wind farm grid connection points;

[0025] The dominant oscillation source is determined when a state switch triggers a sub-supersynchronous oscillation based on all candidate oscillation sources.

[0026] In some embodiments, the suppression of weak grid interaction instability in the subsynchronous frequency band of the wind farm where the dominant oscillation source is located specifically includes:

[0027] Determine the grid impedance characteristics when the wind farm where the dominant oscillation source is located is in a weak grid;

[0028] The power grid impedance characteristics are used to identify multiple negative damping frequency points when interactive instability occurs in the subsynchronous frequency band.

[0029] An adaptive damping controller is added to the wind farm where the dominant oscillation source is located, and then the adaptive damping controller applies phase compensation to each negative damping frequency point to suppress weak grid interaction instability.

[0030] The phase compensation is adjusted based on the change in power frequency impedance of the wind farm where the dominant oscillation source is located.

[0031] In some embodiments, the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and equipment in the hybrid power grid during the blocking state transition specifically includes:

[0032] Determine multiple overfrequency coupling impedances between the dominant oscillation source and equipment in the hybrid power grid at the supersynchronous frequency;

[0033] Based on the supersynchronous frequency and all the supersynchronous coupling impedances, determine multiple supersynchronous resonance points when the dominant oscillation source resonates with the equipment in the hybrid power grid to induce supersynchronous frequency band oscillations.

[0034] A supersynchronous virtual impedance controller is introduced in the wind farm where the dominant oscillation source is located, and multiple virtual impedances under the supersynchronous frequency band of the dominant oscillation source are generated by the supersynchronous virtual impedance controller.

[0035] Determine the compensation amount for modulus matching of the virtual impedance at each supersynchronous resonant point and all over-frequency coupling impedances.

[0036] The supersynchronous virtual impedance controller is adjusted based on all compensation values ​​to suppress the oscillation of the dominant oscillation source.

[0037] In some embodiments, voltage and current phasors at the grid connection points of each wind farm in the hybrid power grid are collected by a synchronous phasor measurement unit.

[0038] In some embodiments, the wind farm grid connection point is the connection node between the wind farm and the power grid, and includes wind turbine generators, converters and local control equipment.

[0039] In some embodiments, the hybrid power grid consists of multiple wind farm grid connection points interconnected in parallel and connected by transmission lines.

[0040] Secondly, this application provides an electrical automation control system for a hybrid power grid, which includes an oscillation suppression unit, the oscillation suppression unit comprising:

[0041] The data acquisition module is used to acquire the voltage and current phasors at the grid connection points of each wind farm in the hybrid power grid.

[0042] The processing module is used to determine the change in power frequency impedance at each wind farm grid connection point when the state switch triggers sub-supersynchronous oscillation based on all voltage and current phasors in the power frequency band.

[0043] The processing module is also used to determine the oscillation threshold of the hybrid power grid during sub-supersynchronous oscillation by using the oscillation frequency and output power of each wind farm grid connection point, and to screen out the dominant oscillation source when the state switching causes sub-supersynchronous oscillation from each wind farm grid connection point based on the oscillation threshold and all power frequency impedance changes.

[0044] The execution module is used to suppress weak grid interaction instability in the subsynchronous frequency band of the wind farm where the dominant oscillation source is located, and to block the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and the equipment in the hybrid grid during the state transition.

[0045] The technical solutions provided by the embodiments disclosed in this application have the following beneficial effects:

[0046] The electrical automation control system and oscillation suppression method for the hybrid power grid provided in this application first collects the voltage and current phasors of each wind farm grid connection point in the hybrid power grid; determines the change in power frequency impedance of each wind farm grid connection point when the state switch causes sub-supersynchronous oscillation based on all voltage and current phasors in the power frequency band; determines the oscillation threshold of the hybrid power grid during sub-supersynchronous oscillation by using the oscillation frequency and output power of each wind farm grid connection point; and selects the dominant oscillation source from each wind farm grid connection point during sub-supersynchronous oscillation caused by the state switch based on the oscillation threshold and all power frequency impedance changes; performs weak grid interaction instability suppression on the sub-synchronous frequency band of the wind farm where the dominant oscillation source is located, and blocks the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and equipment in the hybrid power grid during the state transition.

[0047] Therefore, in the oscillation suppression method for hybrid power grids in this application, firstly, the voltage and current phasors of each wind farm grid connection point in the hybrid power grid are collected; based on all voltage and current phasors in the power frequency band, the power frequency impedance change of each wind farm grid connection point during sub-supersynchronous oscillations caused by state switching is determined; among them, is a parameter value describing the change in amplitude and phase of the power frequency impedance of each wind farm grid connection point when the hybrid power grid switches from grid-connected to islanded state due to a fault. This parameter is used to assess the risk of sub-supersynchronous oscillations during state switching of the hybrid power grid and to reflect the amplitude and direction of impedance changes during state switching, facilitating the subsequent location of the oscillation source of the dominant oscillation during state switching of the hybrid power grid. Secondly, through each The oscillation frequency and output power of the wind farm's grid connection point determine the oscillation threshold for the sub-supersynchronous oscillation of the hybrid power grid. Based on this oscillation threshold and all power frequency impedance changes, the dominant oscillation source causing sub-supersynchronous oscillations during state transitions is screened from each wind farm's grid connection point. This dominant oscillation source is the one that plays a major driving role in the generation, maintenance, or aggravation of sub-supersynchronous oscillations in the hybrid power grid during state transitions, such as switching from grid connection to islanding. This source is used to accurately locate the key triggers for oscillations during hybrid power grid state transitions. Finally, weak grid interaction instability suppression is applied to the sub-synchronous frequency band of the wind farm where the dominant oscillation source is located, and the supersynchronous frequency band oscillations caused by resonance between the dominant oscillation source and equipment in the hybrid power grid during state transitions are blocked. This scheme can suppress sub-supersynchronous oscillations when the hybrid power grid switches from fault to islanding. Attached Figure Description

[0048] Figure 1 This is an exemplary flowchart of a hybrid power grid oscillation suppression method according to some embodiments of this application;

[0049] Figure 2 This is an exemplary flowchart illustrating the determination of an oscillation threshold according to some embodiments of this application;

[0050] Figure 3These are example diagrams of impedance characteristic curves shown according to some embodiments of this application;

[0051] Figure 4 This is a schematic diagram of the structure of an oscillation suppression unit according to some embodiments of this application;

[0052] Figure 5 This is a schematic diagram of the structure of a computer device for implementing a hybrid power grid oscillation suppression method according to some embodiments of this application. Detailed Implementation

[0053] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0054] refer to Figure 1 The figure is an exemplary flowchart of a hybrid power grid oscillation suppression method according to some embodiments of this application. The oscillation suppression method of the hybrid power grid mainly includes the following steps:

[0055] In step 101, the voltage phasors and current phasors of each wind farm grid connection point in the hybrid power grid are collected.

[0056] In practical implementation, synchronous phasor measurement units are deployed at each wind farm grid connection point in the hybrid power grid to synchronously acquire the original full-frequency voltage and current signals of each wind farm grid connection point during a fault. The voltage and current components of each wind farm grid connection point are extracted using the Fourier transform module built into the synchronous phasor measurement unit. Both voltage and current components are in complex form, containing both effective values ​​and phase angles. All voltage and current components are timestamped based on a synchronous clock to ensure spatiotemporal consistency of data from different measurement points. Specifically, a single wind farm grid connection point... Each wind farm grid connection point corresponds to a set of voltage and current phasors. The acquisition frequency in this application is 13kHz. The hybrid power grid consists of multiple wind farm grid connection points connected in parallel and interconnected through transmission lines. The wind farm grid connection point is the connection node between the wind farm and the power grid, including wind turbine generators, converters, and local control equipment. The wind farm converter supports dual-mode switching between "grid-connected" and "network-connected" modes. That is, it operates in grid-connected mode when the hybrid power grid is connected to the grid, and switches to network-connected mode when the hybrid power grid is isolated. Other methods can be used to determine the mode in other embodiments, which are not limited here.

[0057] In step 102, the change in power frequency impedance at each wind farm grid connection point is determined based on all voltage and current phasors in the power frequency band when the state switch triggers sub-supersynchronous oscillation.

[0058] In some embodiments, determining the change in power frequency impedance at each wind farm grid connection point during sub-supersynchronous oscillation caused by state switching based on all voltage and current phasors in the power frequency band can be achieved using the following steps:

[0059] Determine the steady-state period of the hybrid power grid prior to the fault;

[0060] Determine the fault period of the hybrid power grid after the fault occurs;

[0061] The steady-state power frequency impedance of each wind power grid connection point before the fault is determined based on all voltage phasors and current phasors of the power frequency band and the steady-state time period.

[0062] Based on all voltage phasors and current phasors of the power frequency band and the fault period, determine the fault power frequency impedance of each wind power grid connection point when the sub-supersynchronous oscillation is triggered.

[0063] The change in power frequency impedance at each wind farm grid connection point is determined based on all steady-state power frequency impedances and all fault power frequency impedances when the state switch triggers sub-supersynchronous oscillation.

[0064] In specific implementation, determining the steady-state period of the hybrid power grid before the fault can be achieved in the following way: All power frequency voltage and current phasors of each wind farm grid-connected point are sorted according to the acquisition time to obtain the power frequency voltage phasor amplitude sequence and power frequency current phasor amplitude sequence of each wind farm grid-connected point. One wind farm grid-connected point is selected as the chosen grid-connected point. The short-time energy entropy of the power frequency voltage phasor amplitude sequence of the chosen grid-connected point within each sliding window is calculated using the sliding window energy entropy algorithm. The sliding window size is 20ms. Short-time energy entropy is a parameter describing the complexity of the energy distribution of a voltage signal within a short time period, used to reflect the energy distribution within a local time range. The stability and fluctuation characteristics of the voltage signal; if the rate of change of short-time energy entropy of the selected grid connection point is less than the change threshold within 5 consecutive sliding windows, then the time range composed of the 5 consecutive sliding windows is taken as the candidate steady-state period of the selected grid connection point, and the candidate steady-state periods of the remaining wind farm grid connection points are determined. The period in which all the obtained candidate steady-state periods overlap is taken as the steady-state period of the hybrid grid. The steady-state period refers to the period in which the voltage phasor amplitude changes tend to stabilize in a short time during the operation of the hybrid grid. The change threshold can be set according to the specific operating conditions. In this application, it is set to 0.05%. Other methods can be used to determine it in other embodiments, which are not limited here.

[0065] In specific implementation, the fault period of the hybrid power grid after a fault can be determined in the following way: The voltage and current phasors of each wind farm grid connection point are sorted according to the acquisition time to obtain the power frequency voltage phasor amplitude sequence and power frequency current phasor amplitude sequence of each wind farm grid connection point. One wind farm grid connection point is selected as the selected grid connection point. The voltage assignment mutation rate of the power frequency voltage phasor amplitude sequence of the selected grid connection point at the corresponding acquisition time is calculated. All acquisition times with voltage assignment mutation rates exceeding 0.1 are marked as the fault time points of the selected grid connection point after the fault. Multiple fault time points of the remaining wind farm grid connection points are then determined. The time period consisting of the overlapping fault time points among all obtained fault time points is taken as the fault period of the hybrid power grid after the fault. The fault period refers to the time period during which the voltage and current in the hybrid power grid become significantly unstable after the fault occurs. Other methods can also be used in other embodiments, which are not limited here.

[0066] In specific implementation, determining the steady-state power frequency impedance of each wind farm grid connection point before the fault, based on all voltage and current phasors of the power frequency band and the steady-state period, can be achieved in the following way: First, select a wind farm grid connection point as the selected grid connection point. Then, perform Kalman filtering on the voltage and current phasors of all power frequency bands of the selected grid connection point during the steady-state period to eliminate noise during data acquisition and measurement. Next, obtain the steady-state power frequency impedance of the selected grid connection point from the voltage and current phasors of all power frequencies during the steady-state period after noise elimination, using the least squares method and Ohm's law. Finally, calculate the phase difference between multiple voltage and current phasors of the selected grid connection point during the steady-state period. (The last sentence appears to be incomplete and possibly refers to a separate calculation.) One sampling time corresponds to one phase difference between a voltage phasor and a current phasor. All obtained phase differences are used as the impedance angle of the selected grid connection point during the steady-state period. The steady-state power frequency impedance and multiple impedance angles of the remaining wind farm grid connection points are then determined. The steady-state power frequency impedance refers to the complex ratio of the voltage phasor to the current phasor at the wind farm grid connection point under the stable operating state after the hybrid grid state switch. It reflects the equivalent electrical characteristics of the grid connection point at the power frequency. The steady-state power frequency impedance is in complex form, with the real part being the resistance component, characterizing the active power loss characteristics of the grid connection point, and the imaginary part being the reactance component, representing the reactive energy storage characteristics of the grid connection point. Other methods can be used to determine the impedance in other embodiments, which are not limited here.

[0067] In specific implementation, the fault power frequency impedance of each wind farm grid connection point during the fault period, based on all voltage and current phasors of the power frequency band and the fault period, can be determined in the following way: First, select a wind farm grid connection point as the selected grid connection point. Calculate the impedance at each sampling time point during the fault period using the recursive least squares method for all power frequency voltage and current phasors of the selected grid connection point during the fault period. Second, calculate the phase difference between multiple voltage and current phasors of the selected grid connection point during the fault period. One sampling time during the fault period corresponds to one phase difference between a voltage and current phasor. All obtained phase differences are used as the impedance angle of the selected grid connection point during the fault period. This is then analyzed using a matrix laboratory (Matrix). The Laboratory (MATLAB) calculates the rate of change of each impedance angle at the corresponding acquisition time, and marks the sampling time corresponding to the rate of change of all impedance angles greater than 5 as the oscillation time. Finally, the average value of the impedance at all oscillation times is used as the fault power frequency impedance when the selected grid connection point triggers sub-supersynchronous oscillation during the fault period, and the fault power frequency impedance of the remaining wind farm grid connection points is further determined. Other methods can be used to determine the fault power frequency impedance in other embodiments, which are not limited here.

[0068] It should be noted that when calculating the rate of change of impedance angle, the rates of change of impedance angle for subsynchronous and supersynchronous frequencies are statistically analyzed separately. The corresponding sampling time is marked as the oscillation moment if and only if any frequency band meets the judgment condition (the rate of change of impedance angle is greater than 5). The fault power frequency impedance refers to the complex ratio of the voltage phasor to the current phasor at the wind farm grid connection point during the fault period (unstable operation state) caused by the switching of hybrid grid state. It reflects the dynamic equivalent electrical characteristics of the wind farm grid connection point at the power frequency. The fault power frequency impedance is in complex form, with the real part being the resistance component, characterizing the active power loss characteristics of the grid connection point during the oscillation (including equipment internal resistance and oscillation-induced additional losses), and the imaginary part being the reactance component, characterizing the reactive energy storage characteristics of the grid connection point during the oscillation (including line reactance and dynamic reactance changes caused by oscillation).

[0069] In specific implementation, the change in power frequency impedance of each wind farm grid connection point during sub-supersynchronous oscillation caused by state switching, based on all steady-state power frequency impedances and all fault power frequency impedances, can be achieved as follows: Select one wind farm grid connection point as the selected grid connection point. Use the difference between the mean impedance angle during the steady-state period and the mean impedance angle during the fault period of the selected grid connection point as the impedance phase change of the selected grid connection point. Then, substitute the steady-state power frequency impedance, fault power frequency impedance, and impedance phase change of the selected grid connection point into the calculation formula to obtain the power frequency impedance change of the selected grid connection point. Continue to determine the power frequency impedance changes of the remaining wind farm grid connection points. The calculation formula for the power frequency impedance change can be: Power frequency impedance change = Other methods may be used to determine this in other embodiments, which are not limited here.

[0070] It should be noted that the power frequency impedance change in this application is a parameter value describing the change in amplitude and phase of the power frequency impedance at each wind farm grid connection point when the hybrid power grid switches from grid-connected to islanded state due to a fault. It is used to assess the risk of subsynchronous oscillations during the state switching process of the hybrid power grid and to reflect the amplitude and direction of impedance changes during the state switching process, which is convenient for locating the oscillation source of the dominant oscillation during the state switching of the hybrid power grid. When the grid is connected, the hybrid power grid is supported by the large grid, and the power frequency impedance fluctuation at the wind farm grid connection point is small. At this time, the wind farm converter operates in a "grid-following" mode and is not prone to oscillation. However, after the fault switch to islanded state, the hybrid power grid loses the support of the large grid, and the equivalent impedance increases sharply. The wind farm converter needs to switch to "grid-building" operation (virtual inertia, damping control). The control parameters of the wind farm converter and the weak grid impedance are prone to form negative damping coupling, which can cause subsynchronous oscillations. At the same time, the capacitive branch at the output end of the wind farm resonates with the inductive impedance of the islanded system, which can cause supersynchronous oscillations. Both of these oscillations can cause a sudden change in the power frequency impedance at the wind farm grid connection point.

[0071] In step 103, the oscillation threshold of the hybrid power grid during sub-supersynchronous oscillation is determined by the oscillation frequency and output power of each wind farm grid connection point. Based on the oscillation threshold and all power frequency impedance changes, the dominant oscillation source that causes sub-supersynchronous oscillation during state switching is selected from each wind farm grid connection point.

[0072] In some embodiments, reference Figure 2 As shown, this figure is an exemplary flowchart for determining the oscillation threshold in some embodiments of this application. In this embodiment, determining the oscillation threshold during the sub-supersynchronous oscillation of the hybrid power grid by using the oscillation frequency and output power of each wind farm grid connection point can be achieved through the following steps:

[0073] First, in step 1031, the collected voltage phasors and current phasors are subjected to spectral analysis to obtain multiple spectral distributions;

[0074] Secondly, in step 1032, multiple sub-supersynchronous frequency components are extracted from all the spectrum distributions as the oscillation frequency of each wind power grid connection point during sub-supersynchronous oscillation.

[0075] Furthermore, in step 1033, the output power of each wind farm grid connection point is determined based on the voltage phasor and current phasor at the time of the fault.

[0076] Finally, in step 1034, the characteristics of sub-supersynchronous oscillation at each wind farm grid connection point are correlated based on all oscillation frequencies and all output power to obtain the oscillation threshold of the hybrid power grid.

[0077] In specific implementation, the collected voltage and current phasors are subjected to spectral analysis to obtain multiple spectral distributions. This can be achieved in the following way: the voltage and current phasors of each wind farm grid connection point are processed in the time domain (e.g., windowed by the Hanning window function) to obtain the windowed voltage and current phasor sequences of each wind farm grid connection point. Then, a fast Fourier transform is performed on all the voltage and current phasor sequences to obtain the spectral distribution of each wind farm grid connection point. Each wind farm grid connection point corresponds to one spectral distribution. The spectral distribution refers to the distribution of voltage and current at different frequency components of the wind farm grid connection point. The spectral distribution consists of multiple frequency points and multiple energies, with each frequency point corresponding to one energy. Other methods can also be used to determine the spectral distribution in other embodiments, which are not limited here.

[0078] In specific implementation, extracting multiple sub-supersynchronous frequency components from all spectral distributions as the oscillation frequencies of each wind farm grid-connected point during sub-supersynchronous oscillation can be achieved in the following way: Select a spectral distribution as the chosen spectral distribution, judge all peak values ​​of the chosen spectral distribution within the 20-120Hz frequency band, mark all frequency points within this frequency band whose energy is greater than 15% of the power frequency energy as sub-supersynchronous frequency components, and use the set of all sub-supersynchronous frequency components as the oscillation frequency of the wind farm grid-connected point corresponding to the chosen spectral distribution, and continue to determine the oscillation frequencies of the remaining spectral distributions corresponding to the wind farm grid-connected points; wherein, when a fault occurs, the resonance and negative damping effect caused by the impedance change of the hybrid grid leads to a significant increase in the energy of a specific frequency point, and the oscillation frequency is the oscillation frequency of each wind farm grid-connected point when the hybrid grid switches from the grid-connected state to the islanded state; other methods can also be used to determine this in other embodiments, which are not limited here.

[0079] In specific implementation, determining the output power of each wind farm grid connection point based on the voltage and current phasors during a fault can be achieved in the following way: The voltage and current phasors at the power frequency of each wind farm grid connection point during the fault period are substituted into the instantaneous power calculation formula. A phasor-based calculation method is used to calculate the power consumed by each wind farm grid connection point during state switching and the exchange power related to reactance, obtaining the instantaneous power of each wind farm grid connection point at each sampling time point during the fault period. The average of all instantaneous powers corresponding to each wind farm grid connection point is taken as the output power of each wind farm grid connection point. Here, the output power refers to the power transmitted from the wind farm grid connection point to the hybrid grid, reflecting the power support capability of the wind farm to the hybrid grid during fault state switching. The instantaneous power refers to the power transmitted from the wind farm grid connection point to the hybrid grid at each sampling time point during the fault period, including active power and reactive power. Other methods can also be used in other embodiments, which are not limited here.

[0080] In specific implementation, the oscillation threshold of the hybrid power grid is obtained by associating the characteristics of sub-supersynchronous oscillations at each wind farm grid connection point based on all oscillation frequencies and all output powers. This can be achieved in the following way: Select a wind farm grid connection point as the selected grid connection point, and use the output power, oscillation frequency, and power frequency impedance change of the selected grid connection point as feature vectors, inputting them into the training model (such as a support vector machine model). At the same time, use historical oscillation data of the hybrid power grid (which can be obtained from power industry organizations and associations) as samples to perform feature association training on the output power, oscillation frequency, and power frequency impedance change of the selected grid connection point to obtain the oscillation risk score of the selected grid connection point. The oscillation risk score describes the risk level of oscillation at the wind farm grid connection point during state switching and is used to quantify the similarity with its corresponding historical oscillation data. Then, the weighted average of the oscillation risk scores of each wind farm grid connection point is calculated to obtain the oscillation threshold of the hybrid power grid. Other methods can also be used to determine this in other embodiments, which are not limited here.

[0081] It should be noted that the oscillation threshold in this application refers to the threshold of the risk level of the hybrid power grid entering a critical oscillation state when switching from a grid-connected state to an islanded state. It is used to measure the risk level of oscillation in the hybrid power grid during state switching and to determine whether the hybrid power grid has entered a critical oscillation state during state switching, which facilitates the subsequent screening of oscillation sources.

[0082] In some embodiments, the dominant oscillation source for subsynchronous oscillations triggered by state switching can be selected from each wind farm grid connection point based on the oscillation threshold and all power frequency impedance changes using the following steps:

[0083] Select a wind farm grid connection point as the selected grid connection point, and compare the power frequency impedance change of the selected grid connection point with the oscillation threshold.

[0084] If the change in power frequency impedance at the selected grid connection point is greater than the oscillation threshold, then the selected grid connection point will be used as a candidate oscillation source.

[0085] Continue to identify candidate oscillation sources among the remaining wind farm grid connection points;

[0086] The dominant oscillation source is determined when a state switch triggers a sub-supersynchronous oscillation based on all candidate oscillation sources.

[0087] In specific implementation, the dominant oscillation source during state switching can be determined based on all candidate oscillation sources in the following way: cluster analysis is performed on all impedance angles of each candidate oscillation source using a clustering algorithm (such as hierarchical clustering algorithm), and the cluster with the largest change in average power frequency impedance is selected as the key cluster. The candidate oscillation source with the largest change in power frequency impedance is then selected from the key cluster as the dominant oscillation source during state switching. Other methods can also be used in other embodiments, which are not limited here.

[0088] It should be noted that the dominant oscillation source in this application refers to the oscillation source that plays a major driving role in the generation, maintenance or aggravation of sub-supersynchronous oscillations of the hybrid power grid during state switching scenarios such as switching from grid connection to islanding. It is used to accurately locate the key causes of oscillations during state switching of the hybrid power grid and provide a clear target for the subsequent formulation of targeted oscillation suppression strategies. In addition, if the change in power frequency impedance of the selected grid connection point is less than or equal to the oscillation threshold, no processing is performed on the selected grid connection point.

[0089] In step 104, weak grid interaction instability suppression is performed on the subsynchronous frequency band of the wind farm where the dominant oscillation source is located, and the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and the equipment in the hybrid grid during the state transition is blocked, thereby obtaining the oscillation energy index of the hybrid grid during the state transition.

[0090] In some embodiments, the suppression of weak grid interaction instability in the subsynchronous frequency band of the wind farm where the dominant oscillation source is located can be achieved by the following steps:

[0091] Determine the grid impedance characteristics when the wind farm where the dominant oscillation source is located is in a weak grid;

[0092] The power grid impedance characteristics are used to identify multiple negative damping frequency points when interactive instability occurs in the subsynchronous frequency band.

[0093] An adaptive damping controller is added to the wind farm where the dominant oscillation source is located, and then the adaptive damping controller applies phase compensation to each negative damping frequency point to suppress weak grid interaction instability.

[0094] The phase compensation is adjusted based on the change in power frequency impedance of the wind farm where the dominant oscillation source is located.

[0095] In specific implementation, determining the grid impedance characteristics of the wind farm where the dominant oscillation source is located when it is in a weak grid can be achieved in the following way: First, plot all impedance amplitudes and impedance angles of the grid connection point of the wind farm where the dominant oscillation source is located during the fault period using MATLAB to create impedance characteristic curves. These curves describe the impedance characteristics of the grid connection point of the wind farm where the dominant oscillation source is located, with the horizontal axis representing frequency, the vertical axis representing impedance amplitude, and the horizontal axis representing impedance angle. (Refer to...) Figure 3 As shown in the figure, this is an example diagram of impedance characteristic curves in some embodiments of this application. Next, based on all voltage phasors at the grid connection point of the wind farm where the dominant oscillation source is located during the fault period, the short-circuit ratio at each frequency point is calculated. Then, the set of all frequency points at the grid connection point of the wind farm where the dominant oscillation source is located, where the short-circuit ratio is less than 3 and the impedance angle is greater than 45°, is taken as the frequency region of the weak grid of the wind farm where the dominant oscillation source is located. Finally, the set of impedance amplitude, impedance angle, and short-circuit ratio corresponding to each frequency point within the frequency region of the weak grid is taken as the grid impedance characteristic when the wind farm where the dominant oscillation source is located is in a weak grid condition. The grid impedance characteristic describes the impedance of the main oscillation source under weak grid conditions. Other methods can be used to determine this in other embodiments, which are not limited here.

[0096] In specific implementation, identifying multiple negative damping frequency points when interactive instability occurs in the subsynchronous frequency band through the grid impedance characteristics can be achieved in the following way: The impedance angle of the subsynchronous frequency band (20-50Hz) in the grid impedance characteristics is judged, and all frequency points with impedance angles greater than 90° in this band are marked as interactive instability points. All interactive instability points are matched with all sub-supersynchronous frequency components of the wind farm grid connection point where the dominant oscillation source is located. All interactive instability points with a frequency difference less than 2Hz are selected as negative damping frequency points when interactive instability occurs. Here, a negative damping frequency point refers to a frequency point where the oscillation energy of the hybrid grid is amplified, leading to continuous or even intensified oscillation. When the impedance angle of a certain frequency point is greater than 90°, it indicates that the frequency point has negative damping characteristics and is prone to interactive instability. Other methods can also be used to determine this in other embodiments, which are not limited here.

[0097] In specific implementation, an adaptive damping controller is added to the wind farm where the dominant oscillation source is located. The adaptive damping controller then applies phase compensation to each negative damping frequency point to suppress weak grid interaction instability. This can be achieved as follows: An adaptive damping controller is connected to the inner current loop of the converter in the wind farm where the dominant oscillation source is located. This adaptive damping controller adopts a "proportional + multi-frequency resonant controller" structure (i.e., a complex proportional resonant controller). By adjusting the resonant parameters of the resonant controller, each negative damping frequency point is set to the center frequency of the resonant term of the resonant controller, thereby suppressing... The current signals at each negative damping frequency point are amplified, and then the converter outputs the reverse compensation voltage at each negative damping frequency point to cancel the original negative damping characteristics. At the same time, the difference between the original impedance angle formed by the interaction between the hybrid power grid and the converter at each negative damping frequency point and the positive damping critical value is calculated. This difference is used as the phase compensation to suppress the instability of the weak power grid interaction. Finally, the total impedance angle formed by the interaction between the converter current inner loop and the weak power grid is compensated by adjusting the time constant and proportional coefficient of the correction circuit in combination with phase compensation. Other methods can be used to determine this in other embodiments, which are not limited here.

[0098] It should be noted that the amplification of the current signal at each negative damping frequency point is usually 5-10 times the original current signal frequency, and is set to 5 times in this application; the critical value of positive damping refers to the boundary value when the hybrid power grid transitions from a positive damping state to a negative damping state, and is set to 90° in this application.

[0099] In some embodiments, the supersynchronous frequency band oscillation induced by the resonance between the dominant oscillation source and the equipment in the hybrid power grid during the blocking state transition can be achieved by the following steps:

[0100] Determine multiple overfrequency coupling impedances between the dominant oscillation source and equipment in the hybrid power grid at the supersynchronous frequency;

[0101] Based on the supersynchronous frequency and all the supersynchronous coupling impedances, determine multiple supersynchronous resonance points when the dominant oscillation source resonates with the equipment in the hybrid power grid to induce supersynchronous frequency band oscillations.

[0102] A supersynchronous virtual impedance controller is introduced in the wind farm where the dominant oscillation source is located, and multiple virtual impedances under the supersynchronous frequency band of the dominant oscillation source are generated by the supersynchronous virtual impedance controller.

[0103] Determine the compensation amount for modulus matching of the virtual impedance at each supersynchronous resonant point and all over-frequency coupling impedances.

[0104] The supersynchronous virtual impedance controller is adjusted based on all compensation values ​​to suppress the oscillation of the dominant oscillation source.

[0105] In specific implementation, determining the multiple over-frequency coupling impedances between the dominant oscillator and the equipment in the hybrid power grid at the supersynchronous frequency can be achieved in the following way: First, the 60-120Hz frequency band in the spectrum distribution of the wind farm grid connection point where the dominant oscillator is located is taken as the supersynchronous frequency band of the dominant oscillator. Second, multiple target frequency points are formed by screening frequency points with amplitudes greater than or equal to 0.05 pu and located in the supersynchronous frequency band from the voltage and current phasors of the power frequency collected from the wind farm grid connection point where the dominant oscillator is located. Then, each target frequency point is set using a complex bandpass filter. The center frequency is determined and the voltage and current components at each supersynchronous frequency are filtered out. Finally, the complex phasors (including amplitude and phase information) of the components (voltage and current) at each supersynchronous frequency are calculated using discrete Fourier transform, and the over-frequency coupling impedance between the dominant oscillator and the equipment in the hybrid power grid at each supersynchronous frequency is calculated using the phasor ratio. The over-frequency coupling impedance refers to the impedance generated by the interaction between the dominant oscillator and other equipment in the hybrid power grid at the supersynchronous frequency. In other embodiments, other methods can be used to determine this impedance, which is not limited here.

[0106] In specific implementation, determining multiple supersynchronous resonance points for the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillator and the equipment in the hybrid power grid, based on the supersynchronous frequency and all supersynchronous coupling impedances, can be achieved in the following way: The phase angle at each supersynchronous frequency point is obtained by combining the complex phasors of the voltage and current components at each supersynchronous frequency point with the phase angle calculation formula, where the phase angle is in complex form. Thus, all supersynchronous frequency points with an absolute real part of the supersynchronous coupling impedance less than or equal to 0.1 and an absolute phase angle less than or equal to 5° are marked as supersynchronous resonance points. A supersynchronous resonance point refers to a specific frequency point within the supersynchronous frequency band where the hybrid power grid resonates due to the coupling impedance characteristics between the dominant oscillator and other equipment in the hybrid power grid. Other methods can also be used to determine this in other embodiments, which are not limited here.

[0107] In a specific implementation, a supersynchronous virtual impedance controller is introduced into the wind farm where the dominant oscillation source is located. The generation of multiple virtual impedances at the supersynchronous frequency band of the dominant oscillation source through this controller can be achieved in the following way: a complex proportional resonant controller is integrated as a virtual impedance controller within the current inner loop of the converter controller in the wind farm where the dominant oscillation source is located. The virtual impedance at each supersynchronous resonant point is generated through the transfer function of the virtual impedance controller, where the transfer function is a function reflecting the amplitude and phase of the virtual impedance at different frequencies. Other methods can be used to determine the impedance in other embodiments, which are not limited here.

[0108] In specific implementation, the multiple compensation quantities for determining the virtual impedance at each supersynchronous resonance point and all over-frequency coupling impedances for magnitude matching can be achieved in the following way: adjust the transfer function in the virtual impedance controller so that the magnitude of the virtual impedance at each supersynchronous resonance point is equal to the magnitude of the corresponding over-frequency coupling impedance and opposite in phase, thereby obtaining the compensation quantity at each supersynchronous resonance point. Here, the above-mentioned compensation quantity refers to the amount of virtual impedance that needs to be adjusted to suppress supersynchronous resonance. In other embodiments, other methods can also be used to determine the compensation quantity, which is not limited here.

[0109] In specific implementation, the oscillation suppression of the dominant oscillation source by adjusting the supersynchronous virtual impedance controller based on all compensation values ​​can be achieved in the following way: the compensation value corresponding to each supersynchronous resonance point is converted into a parameter update command to adjust the gain adjustment of each resonance term in the transfer function of the virtual impedance controller. A high-speed clock (e.g., 200MHz) of a Field-Programmable Gate Array is used to achieve nanosecond-level parameter updates to ensure that all resonance terms take effect simultaneously. This allows the adjusted virtual impedance controller to process the current signal at the grid connection point of the wind farm where the dominant oscillation source is located, generating control commands containing the oscillation current components at each supersynchronous resonance point and dynamically limiting the current and voltage. Simultaneously, the converter of the wind farm where the dominant oscillation source is located outputs a compensation current in the supersynchronous frequency band that is out of phase with the oscillation current. This compensation current forms a virtual impedance at each supersynchronous resonance point that is out of phase with the over-frequency coupling impedance, ultimately consuming the oscillation energy of the supersynchronous frequency band of the hybrid power grid and achieving oscillation suppression. Other methods can also be used in other embodiments, which are not limited here.

[0110] Furthermore, in another aspect of this application, in some embodiments, this application provides an electrical automation control system for a hybrid power grid, which includes an oscillation suppression unit, referenced... Figure 4 The figure is a schematic diagram of the structure of an oscillation suppression unit according to some embodiments of this application. The oscillation suppression unit includes: a data acquisition module 401, a processing module 402, and an execution module 403, which are described below:

[0111] The acquisition module 401 in this application is mainly used to acquire the voltage phasors and current phasors of each wind farm grid connection point in the hybrid power grid;

[0112] Processing module 402, in this application, is used to determine the change in power frequency impedance at each wind farm grid connection point when the state switching triggers sub-supersynchronous oscillation based on all voltage phasors and current phasors of the power frequency band.

[0113] It should be noted that the processing module 402 in this application is also used to determine the oscillation threshold of the hybrid power grid during sub-supersynchronous oscillation by using the oscillation frequency and output power of each wind farm grid connection point, and to screen out the dominant oscillation source when the state switching causes sub-supersynchronous oscillation from each wind farm grid connection point according to the oscillation threshold and all power frequency impedance changes.

[0114] The execution module 403 in this application is mainly used to suppress weak grid interaction instability in the subsynchronous frequency band of the wind farm where the dominant oscillation source is located, and to block the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and the equipment in the hybrid grid during the state transition.

[0115] In addition, this application also provides a computer device, the computer device including a memory and a processor, the memory storing code, and the processor being configured to acquire the code and execute the above-described hybrid power grid oscillation suppression method.

[0116] In some embodiments, reference Figure 5 The figure is a schematic diagram of the structure of a computer device implementing a hybrid power grid oscillation suppression method according to some embodiments of this application. The hybrid power grid oscillation suppression method in the above embodiments can be implemented through... Figure 5 The computer device shown is used to implement this, and the computer device includes at least one processor 501, a communication bus 502, a memory 503, and at least one communication interface 504.

[0117] Processor 501 can be a general-purpose central processing unit (CPU) or an application-specific integrated circuit (ASIC).

[0118] The communication bus 502 can be used to transmit information between the aforementioned components.

[0119] Memory 503 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital versatile optical discs, Blu-ray discs, etc.), magnetic disks or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto. Memory 503 may exist independently and be connected to processor 501 via communication bus 502. Memory 503 may also be integrated with processor 501.

[0120] The memory 503 stores program code for executing the scheme of this application, and its execution is controlled by the processor 501. The processor 501 executes the program code stored in the memory 503. The program code may include one or more software modules. The method used in the above embodiments can be implemented by the processor 501 and one or more software modules in the program code in the memory 503.

[0121] Communication interface 504 uses any transceiver-like device to communicate with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc.

[0122] In a specific implementation, as one example, a computer device may include multiple processors, each of which may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. Here, a processor may refer to one or more devices, circuits, and / or processing cores used to process data (e.g., computer program instructions).

[0123] The aforementioned computer device can be a general-purpose computer device or a special-purpose computer device. In specific implementations, the computer device can be a desktop computer, a portable computer, a network server, a handheld digital assistant (PDA), a mobile phone, a tablet computer, a wireless terminal device, a communication device, or an embedded device. This application does not limit the type of computer device.

[0124] In addition, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for suppressing oscillations in a hybrid power grid.

[0125] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0126] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for suppressing oscillations in a hybrid power grid, used in an electrical automation control system to suppress oscillations in the hybrid power grid, wherein, The hybrid power grid includes multiple wind farm grid connection points. During a fault, the hybrid power grid switches from a grid-connected state to an islanded state and experiences oscillations. The method is characterized by the following steps: Collect voltage and current phasors at the grid connection points of each wind farm in the hybrid power grid; The change in power frequency impedance at each wind farm grid connection point is determined based on all voltage and current phasors in the power frequency band when the state switch triggers sub-supersynchronous oscillation. The oscillation threshold of the hybrid power grid during sub-supersynchronous oscillation is determined by the oscillation frequency and output power of each wind farm grid connection point. Based on the oscillation threshold and all power frequency impedance changes, the dominant oscillation source that causes sub-supersynchronous oscillation during state switching is screened from each wind farm grid connection point. Weak grid interaction instability suppression is performed on the subsynchronous frequency band of the wind farm where the dominant oscillation source is located, and the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and equipment in the hybrid grid during state transition is blocked; Specifically, the change in power frequency impedance at each wind farm grid connection point during sub-supersynchronous oscillation caused by state switching, determined based on all voltage and current phasors in the power frequency band, includes: Determine the steady-state period of the hybrid power grid prior to the fault; Determine the fault period of the hybrid power grid after the fault occurs; The steady-state power frequency impedance of each wind power grid connection point before the fault is determined based on all voltage phasors and current phasors of the power frequency band and the steady-state time period. Based on all voltage phasors and current phasors of the power frequency band and the fault period, determine the fault power frequency impedance of each wind power grid connection point when the sub-supersynchronous oscillation is triggered. The change in power frequency impedance at each wind farm grid connection point is determined based on all steady-state power frequency impedances and all fault power frequency impedances when the state switch triggers sub-supersynchronous oscillation. Specifically, determining the oscillation threshold for the sub-supersynchronous oscillation of the hybrid power grid by using the oscillation frequency and output power of each wind farm's grid connection point includes: Spectral analysis was performed on the collected voltage and current phasors to obtain multiple spectral distributions; Multiple sub-supersynchronous frequency components are extracted from all the spectrum distributions and used as the oscillation frequency of sub-supersynchronous oscillation at each wind power grid connection point. The output power of each wind farm's grid connection point is determined based on the voltage and current phasors at the time of the fault. The oscillation threshold of the hybrid power grid is obtained by correlating the characteristics of subsynchronous oscillation at each wind farm grid connection point based on all oscillation frequencies and all output power.

2. The method as described in claim 1, characterized in that, Based on the oscillation threshold and all power frequency impedance changes, the dominant oscillation sources that trigger subsynchronous oscillations during state switching at each wind farm grid connection point are specifically selected, including: Select a wind farm grid connection point as the selected grid connection point, and compare the power frequency impedance change of the selected grid connection point with the oscillation threshold. If the change in power frequency impedance at the selected grid connection point is greater than the oscillation threshold, then the selected grid connection point will be used as a candidate oscillation source. Continue to identify candidate oscillation sources among the remaining wind farm grid connection points; The dominant oscillation source is determined when a state switch triggers a sub-supersynchronous oscillation based on all candidate oscillation sources.

3. The method as described in claim 1, characterized in that, Suppressing weak grid interaction instability in the subsynchronous frequency band of the wind farm where the dominant oscillation source is located specifically includes: Determine the grid impedance characteristics when the wind farm where the dominant oscillation source is located is in a weak grid; The power grid impedance characteristics are used to identify multiple negative damping frequency points when interactive instability occurs in the subsynchronous frequency band. An adaptive damping controller is added to the wind farm where the dominant oscillation source is located, and then the adaptive damping controller applies phase compensation to each negative damping frequency point to suppress weak grid interaction instability. The phase compensation is adjusted based on the change in power frequency impedance of the wind farm where the dominant oscillation source is located.

4. The method as described in claim 1, characterized in that, The supersynchronous frequency band oscillations caused by the resonance between the dominant oscillation source and equipment in the hybrid power grid during the blocking state transition specifically include: Determine multiple overfrequency coupling impedances between the dominant oscillation source and equipment in the hybrid power grid at the supersynchronous frequency; Based on the supersynchronous frequency and all the supersynchronous coupling impedances, determine multiple supersynchronous resonance points when the dominant oscillation source resonates with the equipment in the hybrid power grid to induce supersynchronous frequency band oscillations. A supersynchronous virtual impedance controller is introduced in the wind farm where the dominant oscillation source is located, and multiple virtual impedances under the supersynchronous frequency band of the dominant oscillation source are generated by the supersynchronous virtual impedance controller. Determine the compensation amount for modulus matching of the virtual impedance at each supersynchronous resonant point and all over-frequency coupling impedances. The supersynchronous virtual impedance controller is adjusted based on all compensation values ​​to suppress the oscillation of the dominant oscillation source.

5. The method as described in claim 1, characterized in that, The voltage and current phasors of each wind farm grid connection point in the hybrid power grid are collected by the synchronous phasor measurement unit.

6. The method as described in claim 1, characterized in that, The wind farm grid connection point is the connection node between the wind farm and the power grid, and includes wind turbine generators, converters and local control equipment.

7. The method as described in claim 1, characterized in that, The hybrid power grid consists of multiple wind farm grid connection points connected in parallel and linked by transmission lines.

8. An electrical automation control system for a hybrid power grid, wherein the electrical automation control of the hybrid power grid is performed using the method described in any one of claims 1 to 7, characterized in that, The electrical automation control system of this hybrid power grid includes an oscillation suppression unit, which comprises: The data acquisition module is used to acquire the voltage and current phasors at the grid connection points of each wind farm in the hybrid power grid. The processing module is used to determine the change in power frequency impedance at each wind farm grid connection point when the state switch triggers sub-supersynchronous oscillation based on all voltage and current phasors in the power frequency band. The processing module is also used to determine the oscillation threshold of the hybrid power grid during sub-supersynchronous oscillation by using the oscillation frequency and output power of each wind farm grid connection point, and to screen out the dominant oscillation source when the state switching causes sub-supersynchronous oscillation from each wind farm grid connection point based on the oscillation threshold and all power frequency impedance changes. The execution module is used to suppress weak grid interaction instability in the subsynchronous frequency band of the wind farm where the dominant oscillation source is located, and to block the supersynchronous frequency band oscillation caused by the resonance between the dominant oscillation source and the equipment in the hybrid grid during the state transition.

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