A method for configuring a follow-the-sun network control to suppress high-frequency oscillations in a new energy station

Abstract

The present application relates to a kind of for inhibiting new energy station high-frequency oscillation follow / construct network control configuration method, belong to power system high-frequency oscillation stability control technical field.The present application first establishes follow network type converter output impedance analytical model and station aggregation output impedance model, and verifies the accuracy of model by frequency sweep;Second, based on impedance analysis method, identify system high-frequency oscillation risk, determine the target frequency band and expected compensation of impedance remodeling;Then establish the output impedance analytical model of construct network type converter;Finally, whether the branch is transformed as the decision variable of construct network type, with the least number of transformed branch as the target, with the overall impedance of hybrid system satisfying stability margin as the constraint, optimization configuration model is established and mixed integer programming method is used to solve optimal configuration scheme.The present application can remodel station impedance characteristics by optimizing configuration of a small number of construct network type branches, inhibit high-frequency oscillation from the source, with the advantages of small amount of reconstruction, accurate configuration and strong adaptability.

Description

Technical Field

[0001] This invention relates to the field of power system stability control technology, and particularly to the field of high-frequency oscillation suppression technology for energy storage systems, especially a method for controlling and configuring a grid-connected (mixed grid-connected and grid-configured) system to suppress high-frequency oscillations at renewable energy power plants. Background Technology

[0002] With the large-scale development and grid connection of new energy sources such as wind power and photovoltaics, the power system exhibits the "dual high" characteristics of high proportion of renewable energy and high proportion of power electronic equipment. New energy power plants, comprising new energy generating units and energy storage units, primarily achieve grid connection through power electronic converters. Their control methods are mainly divided into two categories: grid-following control and grid-connecting control. Grid-following control tracks the grid voltage phase through a phase-locked loop (PLL) to achieve synchronization with the grid. It has advantages such as fast response speed, simple control structure, and high equipment utilization, and is currently the mainstream control method for operational new energy power plants. However, grid-following control inherently exhibits current source characteristics, and its output impedance may exhibit negative damping characteristics within a specific frequency range, especially in the mid-to-high frequency band. When a new energy power plant connects to a weak grid, transmits power through a series compensation line, or resonates with adjacent equipment, the coupling effect between the grid-following converter and the grid impedance can easily cause high-frequency oscillations. These oscillation frequencies are typically between several hundred hertz and several thousand hertz, and in severe cases, can lead to new energy generating units disconnecting from the grid, equipment damage, power quality deterioration, and even large-scale power outages, seriously threatening the safe and stable operation of the power grid.

[0003] To address the high-frequency oscillation problem in new energy grid-connected systems, existing technologies mainly employ the following countermeasures: First, after oscillations occur, post-event suppression is achieved by adjusting control parameters, engaging damping controllers, or disconnecting some generating units; second, during the planning and design phase, offline simulation analysis is used to reserve a certain stability margin; and third, grid-type control is used to replace grid-following converters, utilizing the positive damping characteristics of grid-type control under weak grid conditions to improve system stability.

[0004] However, the aforementioned existing technologies still have the following shortcomings:

[0005] First, traditional post-event suppression methods have a significant time lag. These methods often only take adjustment measures after the oscillation has occurred, and lack targeted pre-configuration strategies. They are difficult to adapt to the randomness of new energy output and the time-varying nature of grid operation, and cannot fundamentally prevent the occurrence of high-frequency oscillations.

[0006] Second, switching all branches to grid-type control is not the optimal choice. For large-scale renewable energy power plants, although switching all branches to grid-type control can improve system stability, grid-type control has technical challenges such as power sharing and circulating current suppression during large-scale parallel operation. In contrast, grid-type control has relatively mature operating experience and technical solutions in these aspects. Therefore, the full switching method faces many technical challenges in actual engineering.

[0007] Third, there is a lack of scientific optimization configuration methods for hybrid control. Compared to simply using grid-following or grid-forming control at power stations, hybrid control of grid-following and grid-forming can fully leverage the complementary advantages of both control methods while ensuring stability. Minimizing grid-forming control switching retains the mature characteristics of grid-following control under large-scale parallel operation while utilizing the positive damping characteristics of grid-forming control under weak power grids to improve system stability, making it a more reasonable configuration scheme. However, currently, there is a lack of an optimization configuration method that can effectively reshape the overall impedance characteristics of the power station by minimizing the number of grid-forming branch switching. Existing research mostly relies on experience or simple rules for selecting grid-forming branches, making it difficult to quantitatively evaluate the contribution of each branch switching to system stability, and thus failing to guarantee the scientific validity and effectiveness of the configuration scheme.

[0008] Therefore, there is an urgent need to propose an optimized configuration method that can comprehensively consider the differences in impedance characteristics between grid-connected and grid-connected converters and achieve effective suppression of high-frequency oscillations in new energy power plants with the minimum number of grid-connected branch modifications. Summary of the Invention

[0009] The purpose of this invention is to provide a grid-based control configuration method for suppressing high-frequency oscillations in renewable energy power plants. This method addresses the technical challenges of existing technologies, such as significant hysteresis in post-event suppression methods, power sharing and circulating current suppression during full branch switching to grid-based control, and the lack of a scientifically optimized configuration method for hybrid control. This invention can reshape the power plant's impedance characteristics by optimizing the configuration of a small number of grid-based branches, suppressing high-frequency oscillations at the source. It offers advantages such as minimal modification, precise configuration, and strong adaptability.

[0010] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0011] The grid-connected / grid-building control configuration method for suppressing high-frequency oscillations in renewable energy power plants employs an optimized configuration method combining grid-connected and grid-building control. Specifically, it optimizes the selection of certain branches to switch to grid-building control, reshaping the grid-connected impedance characteristics of the renewable energy power plant to effectively suppress high-frequency oscillations with the optimal number of modifications. The method includes the following steps:

[0012] Step 1: Establish analytical models of the output impedance of each grid converter based on the harmonic linearization method. Based on the topology, a aggregated output impedance model of the entire new energy power station is established. A detailed electromagnetic transient model of the new energy power station was established to verify the impedance model by frequency sweep.

[0013] Step 2: Combine with the equivalent impedance of the actual power grid This study identifies oscillation risks in the high-frequency band of new energy power plant grid-connected systems based on impedance analysis; extracts key frequency bands for instability and negative damping characteristics; and determines the target frequency band and expected impedance compensation amount that require impedance reshaping through grid-connected converters. ;

[0014] Step 3: Establish the analytical model of the output impedance of the grid converter The grid-type converter uses virtual synchronous machine control to ensure positive damping characteristics within the target frequency band;

[0015] Step 4: Using whether each branch is converted to a network-type control as the decision variable, the optimal number of converted branches as the objective function, and the requirement that the overall impedance of the hybrid system meets the stability margin requirement as the constraint, an optimal configuration model is established. The optimal configuration model is solved using the mixed integer programming method to obtain the optimal network-type branch configuration scheme, thereby achieving the optimal configuration for suppressing high-frequency oscillations in new energy power stations with the minimum network-type conversion.

[0016] The analytical model of the output impedance of the grid converter described in step 1 The output impedance analytical model includes the effects of phase-locked loop dynamics, inner current loop control, filter parameters, and control delay; the aggregated output impedance model The aggregated output impedance model is obtained by paralleling and aggregating the impedances of each branch. It includes the influence of the impedances of the collector lines and the main transformer.

[0017] The aggregated output impedance model of the new energy power station mentioned in step 1 is expressed as follows:

[0018] (1)

[0019] In the formula: n is the total number of branch roads within the station; Let be the output impedance of the i-th branch connected to the grid converter; Let be the equivalent impedance of the collector line corresponding to the i-th branch; The equivalent impedance of the main transformer.

[0020] The identification of oscillation risk in step 2 uses the Nyquist criterion or the impedance ratio criterion. When the impedance ratio amplitude is 1 and the phase difference is greater than 180°, the system is determined to have oscillation risk.

[0021] The desired impedance compensation amount described in step 2 The equivalent impedance added at the grid connection point to ensure the system meets stability margin requirements. Based on the impedance convergence principle, the overall impedance of the hybrid system after the grid-type branch modification can be expressed as:

[0022] (2)

[0023] In the formula: To maintain the number of branches in the network structure, To maintain the number of branches in the network structure; Let be the output impedance of the grid-type converter in the r-th branch.

[0024] Let the target impedance ratio required for system stability be:

[0025] (3)

[0026] After the modification, the station impedance This can be represented as the aggregate output impedance model of a new energy power station. Add the desired impedance compensation amount .

[0027] (4)

[0028] Then the expected impedance compensation amount Represented as:

[0029] (5)

[0030] In the formula: Here, represents the equivalent impedance of the power grid; e represents the natural constant; GM is the target gain margin, and PM is the target phase margin. The values ​​of GM and PM can be determined according to the actual needs of the system. (Target frequency band) This compensation should shift the impedance phase of the station in that frequency band towards positive damping, ensuring the impedance ratio. The Nyquist curve is far from the point (-1, j0).

[0031] The optimized configuration model mentioned in step 4 is as follows:

[0032] The objective function is:

[0033] (6)

[0034] In the formula: N is the target configuration quantity; These are decision variables.

[0035] The constraints are:

[0036] (7)

[0037] In the formula: n is the total number of branch roads within the station; The output impedance of the i-th branch when maintaining the mesh control; The output impedance when the i-th branch is converted to a network control system; Let be the equivalent impedance of the collector line corresponding to the i-th branch; The equivalent impedance of the main transformer; GM is the equivalent impedance of the power grid; PM is the target magnitude margin; GM is the target phase margin. For the high-frequency bands that need to be suppressed. Angular frequency; Represents angular frequency After the modification, the station impedance Angular frequency The equivalent impedance of the power grid at that time.

[0038] Solving the optimization configuration model described in step 4 includes the following sub-steps:

[0039] Step 4.1: Frequency domain discretization of impedance stability constraints for the hybrid system of root / network.

[0040] Step 4.2: Linearization of the impedance sensitivity of network-type branches for optimal configuration. The perturbation method is used to calculate the sensitivity coefficient of each branch switching on the overall impedance characteristics of the station, transforming the nonlinear impedance constraint into a linear inequality. Specifically, the overall impedance ratio function of the hybrid system is defined as follows:

[0041] (8)

[0042] At the initial unfolding point Linearization is performed at this point. Y represents the selection of Y key frequency points within the target high-frequency band. ; This is the angular frequency corresponding to the Qth frequency point; Angular frequency After the modification, the station impedance Angular frequency Equivalent impedance of the power grid at that time; express The absolute value of the amplitude of the ratio of the station impedance to the equivalent impedance of the power grid after the renovation; for The phase of the ratio of the station impedance to the equivalent impedance of the power grid after the modification.

[0043] Step 4.3: Construction and solution of the hybrid control optimization configuration model of the linearized constraint and objective function. The linearized constraint and objective function are combined to form a hybrid integer linear programming model, and the solver is called to obtain the candidate configuration scheme.

[0044] Step 4.4: Stability verification and iterative correction of the optimized configuration scheme. Substitute the candidate configuration scheme into the original nonlinear impedance constraints for accurate verification. If all frequency points meet the stability margin requirements, the scheme is accepted as the optimal configuration scheme; otherwise, take the output of the current candidate configuration scheme as the new linearization expansion point, add exclusion constraints, and repeat steps 4.2 to 4.4 until a solution that meets the original constraints is found.

[0045] The impedance sensitivity linearization process described in step 4.2 uses the perturbation method to calculate the sensitivity coefficient of each branch switching on the overall impedance characteristics of the station, transforming the nonlinear impedance constraint into a linear inequality.

[0046] Another objective of this invention is to provide a grid-connected control configuration system for suppressing high-frequency oscillations at renewable energy power plants, comprising:

[0047] The modeling module is used to establish analytical models of the output impedance of grid-connected converters and grid-connected converters, as well as aggregated output impedance models of new energy power plants.

[0048] The risk identification module is used to identify oscillation risks in the high-frequency band of the grid-connected system of new energy power plants, and to determine the target frequency band and expected impedance compensation amount for impedance reshaping.

[0049] The optimization configuration module is used to establish and solve the optimization configuration model to determine the optimal network branch configuration scheme;

[0050] The control execution module is used to switch the selected network-type branch to network-type control according to the optimal network-type branch configuration scheme.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) This invention transforms the configuration problem of grid-type branches into a mixed integer programming problem by establishing an optimization configuration model with the objective function of maximizing the number of modified branches. Under the premise of meeting the stability margin requirements of the grid-connected system, it can accurately identify the branch numbers and quantities that need to be modified. Compared with the existing technologies that "all grid-type converters are modified into grid-type converters" or "converters are selected for control modification based on experience", this invention can significantly reduce the number of grid-type converters to be modified, reduce the difficulty of engineering implementation, and achieve effective suppression of high-frequency oscillations with minimal technical cost.

[0053] (2) This invention proposes a linearization method based on impedance sensitivity. By calculating the impact of each branch modification on the overall impedance characteristics of the station, the nonlinear impedance constraint is transformed into a linear inequality, thereby enabling a quantitative assessment of the contribution of each branch modification to the system stability. This sensitivity analysis method provides clear physical guidance for optimal configuration, avoids blind trial and error, and makes the configuration results more theoretically grounded and engineeringally interpretable.

[0054] (3) This invention adopts a solution strategy of linear approximation, accurate verification, and iterative correction. It utilizes the efficiency of the mixed integer programming solver to ensure the calculation speed, and eliminates linearization errors through accurate verification and iterative compensation mechanisms, ensuring that the final configuration scheme strictly meets the original nonlinear impedance constraints. This strategy takes into account both engineering practicality and result reliability, and is applicable to new energy power plants of different scales.

[0055] (4) This invention optimizes the configuration of grid-type branches and utilizes the positive damping impedance characteristic of the grid-type converter in the target frequency band to reshape the grid-connected impedance characteristics of the new energy power station from the source, so that the impedance ratio of the hybrid system meets the Nyquist stability criterion requirements in the key frequency band. Compared with traditional post-event remedial measures such as filtering and damping control, this invention belongs to an active stability control method, which can fundamentally eliminate the conditions for the occurrence of high-frequency oscillations and avoid the risk of chain reactions after oscillation triggering.

[0056] In summary, this invention provides an economical, precise, and efficient method for suppressing high-frequency oscillations in renewable energy power plants. By optimizing the configuration of a few grid-connected branches, the impedance characteristics of the grid-connected system can be effectively reshaped, providing strong technical support for the safe and stable operation of power systems with a high proportion of renewable energy access. Attached Figure Description

[0057] The accompanying drawings, which are provided to further illustrate the invention and form part of this application, are illustrative examples of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention.

[0058] Figure 1 This invention relates to the topology of the new energy power station.

[0059] Figure 2 This invention relates to the grid-connected converter topology and control structure.

[0060] Figure 3 This invention relates to the grid-type converter topology and control structure.

[0061] Figure 4 This is a flowchart of the optimized configuration method of the present invention;

[0062] Figure 5 This is a diagram illustrating the theory and frequency sweep effect of the grid converter of the present invention;

[0063] Figure 6 This is a diagram illustrating the theory and frequency sweep effect of the grid-type converter of the present invention;

[0064] Figure 7 The diagram shows the impedance characteristics of the mesh under different proportions according to the present invention.

[0065] Figure 8 The time-domain simulation waveform of the grid connection point voltage of the new energy power station in this invention when full grid-following control is adopted;

[0066] Figure 9 The Fourier analysis results of the grid connection point voltage of the new energy power station under full grid-following control according to the present invention;

[0067] Figure 10 The time-domain simulation waveform of the grid connection point voltage for the new energy power station of this invention is shown in the figure, where 50% of the control is based on full grid connection and 50% on structural grid connection.

[0068] Figure 11 The Fourier analysis results of the grid connection point voltage for the new energy power stations of this invention are as follows: 50% adopt full grid-connected control and 50% adopt structural grid-connected control.

[0069] Figure 12 The voltage waveform at the grid connection point after applying the optimized configuration scheme of this invention. Detailed Implementation

[0070] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0071] See Figures 1 to 12As shown, the present invention provides a hybrid control optimization configuration method for suppressing high-frequency oscillations in renewable energy power plants. First, it establishes an analytical model of the output impedance of the grid-type converter and a aggregated output impedance model of the power plant, and verifies the accuracy of the models through frequency sweeping. Second, it identifies the risk of high-frequency oscillations in the system based on impedance analysis, determining the target frequency band and expected compensation amount for impedance reshaping. Then, it establishes an analytical model of the output impedance of the grid-type converter. Finally, using whether branches are converted to grid-type configurations as decision variables, minimizing the number of converted branches as the objective, and ensuring the overall impedance of the hybrid system meets the stability margin as a constraint, it establishes an optimization configuration model and uses mixed integer programming to solve for the optimal configuration scheme. This invention can reshape the impedance characteristics of the power plant by optimizing the configuration of a small number of grid-type branches, suppressing high-frequency oscillations at the source. It has the advantages of low modification requirements, precise configuration, and strong adaptability.

[0072] The grid-connected control configuration method for suppressing high-frequency oscillations at renewable energy power plants according to the present invention includes the following steps:

[0073] Step 1: First, establish the analytical model of the output impedance of each grid converter based on the harmonic linearization method. Then, based on the topology, a aggregated output impedance model for the entire renewable energy power station is established. Finally, a detailed electromagnetic transient model of the new energy power station was established to verify the impedance model by frequency sweep.

[0074] Step 2: First, combine the actual power grid equivalent impedance This study identifies oscillation risks in the high-frequency band of new energy power plant grid-connected systems based on impedance analysis; then, it extracts the key frequency bands for instability and negative damping characteristics; finally, it determines the target frequency bands and desired impedance compensation amounts that require impedance reshaping through grid-connected converters. .

[0075] Step 3: Establish the analytical model of the output impedance of the grid converter The grid-type converter is controlled by a virtual synchronous machine to ensure that it exhibits positive damping characteristics within the target frequency band.

[0076] Step 4: Using whether each branch is converted to a network-type control as the decision variable, the optimal number of converted branches as the objective function, and the requirement that the overall impedance of the hybrid system meets the stability margin requirement as the constraint, establish an optimal configuration model; solve the model using mixed integer programming to obtain the optimal network-type branch configuration scheme.

[0077] Furthermore, the analytical model of the output impedance of the grid-connected converter described in step 1... Specifically:

[0078] A grid-connected converter mainly consists of a phase-locked loop (PLL) synchronization stage, a current inner loop control stage, a PWM modulation stage, and a filter stage. The functions of each stage are as follows: the PLL detects the phase of the grid-connected voltage, providing a synchronization reference for current control; the current inner loop control stage generates a modulation wave based on the deviation between the commanded current and the actual feedback current; the PWM modulation stage converts the modulation wave into a switching signal; and the filter stage filters out high-order harmonics near the switching frequency.

[0079] Since this invention mainly focuses on the high-frequency oscillation problem of new energy grid-connected systems, a harmonic linearization method is adopted to establish a single-dimensional impedance model. That is, a small-signal harmonic disturbance is superimposed at the power frequency steady-state operating point to establish a grid-connected converter sequence impedance model that considers the dynamic characteristics of the above-mentioned links.

[0080] For a single grid-connected converter unit, its output impedance can be expressed as:

[0081] (1)

[0082] In the formula: For the Laplace operator; V1 is the imaginary part; V1 is the effective value of the rated voltage. This refers to the small-signal component of the grid connection point voltage. This refers to the small-signal component of the output current of a single generator unit. This refers to the filter inductance value; This refers to the DC bus voltage of the converter. The transfer function of the inner-loop PI controller is expressed as follows: ,in, This is the proportionality coefficient. The integral coefficient; The fundamental frequency; is the cross-coupling coefficient of the inner current loop; This is the equivalent delay of the current acquisition stage; This refers to the DC voltage modulation coefficient; This is the equivalent delay of the voltage acquisition process; The additional impedance term introduced dynamically by the phase-locked loop reflects the influence of the phase-locked loop bandwidth on the impedance characteristics. The specific expression is related to the phase-locked loop structure and parameters. and These are the d-axis and q-axis components of the selected steady-state operating point current.

[0083] For the i-th branch in the new energy power station, including In a grid-type converter unit, each unit is connected in parallel to the branch busbar via AC cables or overhead lines. Considering the impedance differences between the units, the output impedance of the i-th branch is not a simple parallel combination of the unit impedances, but must take into account the influence of the connecting lines. Taking the k-th unit as an example, its output impedance is defined as... The line impedance from the unit to the branch junction is The equivalent impedance of the unit at the branch convergence point is then... for:

[0084] (2)

[0085] Since each unit is connected in parallel at the branch convergence point, according to the principle of parallel circuits, the overall output impedance of the i-th branch is... The parallel value of the equivalent impedance of all units is expressed as:

[0086] (3)

[0087] When the unit models are the same and the line parameters are identical, the overall output impedance of the i-th branch can be simplified as:

[0088] (4)

[0089] Furthermore, the aggregated output impedance model of the new energy power station described in step 1 is specifically as follows:

[0090] A renewable energy power station mainly consists of multiple parallel converter branches, collector lines, a main transformer, and transmission lines. The functions of each component are as follows: the converter branches contain multiple converter units to realize AC-DC conversion and control of energy; the collector lines collect the power from each branch; and the main transformer raises the power station voltage to the grid-connected voltage level.

[0091] Based on the internal topology of the power station, the impedance models of each branch are combined in parallel, taking into account the equivalent impedances of the collector lines and the main transformer. The aggregated output impedance model of the new energy power station can be expressed as:

[0092] (5)

[0093] In the formula: n is the total number of branch roads within the station; The output impedance of the i-th branch and the grid converter is calculated in step (1); Let be the equivalent impedance of the collector line corresponding to the i-th branch. For radial collector networks, the network transformation can be performed using the principle of equal power loss or the principle of constant port voltage. The equivalent impedance of the main transformer is represented as the series connection of leakage reactance and resistance. This aggregated output impedance model simplifies the complex internal topology of the power station to the equivalent impedance at the grid connection point through impedance network modeling, enabling quantitative analysis of the system's oscillation characteristics.

[0094] Furthermore, the frequency sweep verification method for the detailed electromagnetic transient model of the new energy power station described in step 1 is as follows:

[0095] To verify the accuracy of the impedance analytical model, a frequency sweep verification was performed on the detailed electromagnetic transient model in an electromagnetic transient simulation platform. The frequency sweep system mainly includes a frequency sweep control module, a controllable voltage source module, and a measurement module. The frequency sweep control module generates a frequency sweep control signal based on pre-set frequency sweep parameters, including: the frequency sweep start time t and the frequency sweep start frequency. Frequency sweep end frequency Frequency sweep interval Disturbance amplitude The specific implementation steps for frequency sweep verification are as follows:

[0096] a) In the electromagnetic transient model, a controllable voltage source module is connected in series at the grid connection point of the power station;

[0097] b) Set the initial perturbation frequency When the system is running stably, the voltage source injection frequency is controlled at time t to be... Small signal harmonic voltage disturbance , The phase of the injected voltage disturbance; The magnitude of the injected disturbance voltage.

[0098] c) After the system response returns to a steady state, the voltage response at the grid connection point is acquired using the measurement module. and current response ;

[0099] d) Perform Fourier analysis on the acquired time-domain signal to extract the perturbation frequency. Voltage phasor at and current phasor Calculate the impedance value at this frequency. ;

[0100] e) Using frequency sweep intervals Increment the perturbation frequency and repeat steps b) to d) until... ,get Simulated impedance characteristic curves for the frequency band;

[0101] f) Compare the simulation frequency sweep results with the aggregated output impedance model of the new energy power station. The calculation results are compared to ensure that the amplitude and phase errors of the two models are within the allowable range in the frequency band of interest, thereby verifying the accuracy of the analytical model.

[0102] Furthermore, the method for identifying the oscillation risk in the high-frequency band of the new energy power station grid-connected system described in step 2 is as follows:

[0103] Based on impedance analysis, an overall impedance model of the grid-connected system is established. The Nyquist criterion or impedance ratio criterion is used to determine the stability of the system.

[0104] The specific determination method is as follows: within the preset high-frequency band Inside, This is the minimum angular frequency in this frequency band. Find the maximum angular frequency in this frequency band, and then calculate the impedance ratio. The expression is:

[0105] (6)

[0106] Further judgment is made based on the Nyquist stability criterion. If The number of times the Nyquist curve encircles the point (-1, j0) counterclockwise is equal to and The system is stable if the difference in the number of poles in the right half-plane is significant. In engineering applications using Bode plot analysis, the stability criterion simplifies to: if the impedance ratio magnitude is equal to 1 and the phase difference is greater than 180°, i.e., at a certain angular frequency... Place, and If so, the system is at risk of oscillation.

[0107] Extracting the key frequency bands that cause system instability The negative damping characteristic of the impedance ratio within this frequency band, i.e., the region where the impedance phase is less than -90° or greater than 90°, indicates that the station exhibits negative damping characteristics within this frequency band and may resonate with the power grid.

[0108] Furthermore, the target frequency band and desired impedance compensation amount for impedance reshaping via the grid-type converter described in step 2 are specifically as follows:

[0109] Desired impedance compensation The equivalent impedance required at the grid connection point to ensure the system meets stability margin requirements. Based on the impedance convergence principle, the overall impedance of the hybrid system after the grid-type branch modification can be expressed as:

[0110] (7)

[0111] In the formula: To maintain the number of branches in the network structure, To maintain the number of branches in the network structure. Let be the output impedance of the j-th branch connected to the grid converter.

[0112] Let the target impedance ratio required for system stability be:

[0113] (8)

[0114] After the modification, the station impedance This can be represented as the aggregate output impedance model of a new energy power station. Plus expected compensation .

[0115] (9)

[0116] Then the expected impedance compensation amount Represented as:

[0117] (10)

[0118] In the formula: e represents the natural constant; GM is the target gain margin, and PM is the target phase margin. The values ​​of GM and PM can be determined according to the actual needs of the system. The target frequency band is... The compensation amount should cause the impedance phase of the station in this frequency band to shift in the positive damping direction, ensuring that the Nyquist curve of the impedance ratio is far away from the point (-1, j0).

[0119] Furthermore, the analytical model of the output impedance of the grid-type converter described in step 3 is as follows:

[0120] The grid-type converter employs virtual synchronous machine control, primarily comprising a virtual synchronous machine control loop with virtual inertia and damping elements, and a reactive power-voltage droop control loop. The functions of each element are: the virtual synchronous machine control simulates the rotor motion equations of a synchronous generator, providing inertia and damping support; and the reactive power-voltage droop control maintains stable terminal voltage.

[0121] Based on the harmonic linearization method, a sequence impedance model for a grid-type converter is established:

[0122] (11)

[0123] In the formula: K(s) = e -1.5Ts / [(1+s / (1+s / )],in, , , respectively, are the cutoff angular frequencies of the low-pass filters for voltage and current signals, and T is the time period; The fundamental angular frequency; The fundamental frequency; This represents the amplitude of the fundamental current. , is the initial phase angle of the voltage of the grid-type converter; The initial phase angle of the current in the grid-type converter is represented; J is the virtual moment of inertia coefficient, whose main function is to avoid sudden changes in system frequency when the load changes. It is the active damping coefficient, whose main function is to buffer changes in voltage and current when the load changes. The effective value of the internal potential of the grid-type converter is expressed as:

[0124] (12)

[0125] In the formula: D q Q is the reactive power damping coefficient; ref Q is the reactive power setpoint; out Instantaneous reactive power output; V1 is the effective value of the rated voltage; V is the effective value of the output voltage; K is the voltage modulation coefficient.

[0126] Grid-type converters have good stability under weak power grids. Their output impedance is inductive in the high-frequency range, and the impedance phase is between 0° and 90°, exhibiting positive damping characteristics.

[0127] For the i-th branch, if the branch contains multiple grid-connected units, its branch equivalent impedance is... The calculation method is similar to that of a grid-type branch, that is, the impedance of each unit is connected in series with the line impedance and then in parallel, expressed as:

[0128] (13)

[0129] In the formula: The total number of network branches, Let be the equivalent impedance corresponding to the k-th network element in the i-th line. This is the equivalent impedance corresponding to the collector line of the kth grid unit.

[0130] Furthermore, the network-type branch configuration scheme described in step 4 is specifically as follows:

[0131] Whether each branch road is converted into a network-type control system is used as the decision variable. , This indicates that the i-th branch is being transformed into a network structure. This indicates that, while maintaining the network type, an optimal configuration model is established with the objective function of optimizing the number of modified branches and the constraint that the overall impedance of the hybrid system meets the stability margin requirement.

[0132] The objective function is:

[0133] (14)

[0134] In the formula, N represents the target configuration quantity.

[0135] The constraints are:

[0136] (15)

[0137] In the formula: n is the total number of branch roads within the station; The output impedance of the i-th branch when maintaining the mesh control; The output impedance when the i-th branch is converted to a network control system; Let be the equivalent impedance of the collector line corresponding to the i-th branch; The equivalent impedance of the main transformer; GM is the equivalent impedance of the power grid; PM is the target magnitude margin; GM is the target phase margin. For the high-frequency bands that need to be suppressed; Angular frequency; Represents angular frequency After the modification, the station impedance Angular frequency The equivalent impedance of the power grid at that time.

[0138] This invention employs a mixed-integer programming method to solve the optimal allocation model. The specific solution steps are as follows:

[0139] a) Frequency domain discretization of impedance stability constraints in a hybrid system with / with a network

[0140] Since the impedance constraint established in this invention is an infinite-dimensional constraint, the solver cannot process it directly. Therefore, the impedance constraint in the continuous frequency domain needs to be discretized into a constraint condition with a finite number of frequency points, that is, the infinite-dimensional impedance constraint is transformed into a finite-dimensional impedance constraint. In the target high-frequency band... Select Y key frequency points Then the continuous frequency domain constraint is transformed into:

[0141] (16)

[0142] In the formula, This is the angular frequency corresponding to the Qth frequency point; Angular frequency After the modification, the station impedance Angular frequency The equivalent impedance of the power grid at that time.

[0143] To reduce computational load, the principle for frequency selection is to increase sampling density in frequency bands where impedance ratio curves change drastically and to decrease sampling density in frequency bands where changes are gradual.

[0144] b) Linearization of network branch impedance sensitivity for optimized configuration

[0145] The constraints after discretization are still about the decision variables. The nonlinear function is a complex problem, and mixed-integer programming solvers typically require the objective function and constraints to be linear. Therefore, the impedance sensitivity method is used to linearize the nonlinear constraints. Let:

[0146] (17)

[0147] In the formula, Represented as The absolute value of the amplitude of the ratio of the station impedance to the equivalent impedance of the power grid after the renovation; for The phase of the ratio of the station impedance to the equivalent impedance of the power grid after the modification.

[0148] At the initial unfolding point Performing a first-order Taylor expansion at the given point yields a linear approximation:

[0149] (18)

[0150] In the formula, This represents the initial state of the i-th branch.

[0151] Sensitivity coefficient and Using the perturbation method, keeping the configuration of other branches unchanged, only the i-th branch is switched from a root-type network to a cross-network type. The change in impedance characteristics is calculated as an approximation of the sensitivity, i.e.:

[0152] (19)

[0153] In the formula: Let i be a unit vector whose i-th component is 1 and the rest are 0.

[0154] Substituting the above linear approximation into the constraint conditions, we obtain the linear inequality:

[0155] Amplitude constraints:

[0156] (20)

[0157] Phase lower bound constraint:

[0158] (twenty one)

[0159] Phase upper bound constraint:

[0160] (twenty two)

[0161] In the formula: . The impedance amplitude, This is the impedance phase.

[0162] c) Construction and solution of the hybrid control optimization configuration model based on the network structure.

[0163] Combining the linearized constraints with the objective function yields a standard mixed-integer linear programming model:

[0164] The constraints are simplified as follows:

[0165] (twenty three)

[0166] In the formula: , and To solve for the constant term in step b), it can be expressed as:

[0167] (twenty four)

[0168] d) Stability verification and iterative correction of the optimized configuration scheme.

[0169] Due to the approximation error introduced by linearization, the solution obtained... The original nonlinear impedance constraints may not be strictly satisfied. Therefore, the solution results need to be accurately verified.

[0170] Will Substitute the values ​​into the original impedance calculation formula to calculate the precise amplitude ratio at each key frequency point. and phase difference Check if the following conditions are met:

[0171] (25)

[0172] If all frequency points meet the stability margin requirements, then the optimized configuration scheme is accepted as the optimal configuration scheme; if any frequency point does not meet the constraints, then the current configuration scheme is adopted. As a new linearization expansion point, the sensitivity coefficients are recalculated, and exclusion constraints are added to the model. Steps b) to d) are repeated until a solution satisfying the original constraints is found. The final solution satisfying the constraints... As the output of the optimal configuration scheme, record the set of branch numbers that need to be transformed into network-type control. and the total number of branch roads to be renovated This scheme is an optimized configuration result that achieves high-frequency oscillation suppression of new energy power stations with minimal grid structure modification.

[0173] Example:

[0174] See Figure 1As shown, this embodiment uses a direct-drive wind turbine generator as an example. The topology of the new energy power station includes multiple parallel converter branches, collector lines, a main transformer, and grid connection lines. Each branch initially adopts grid-connected control, and after being collected by the collector lines and stepped up by the main transformer, it is connected to the main grid. This topology is an example of the application of the optimized configuration method of this invention.

[0175] See Figure 2 As shown, the grid-connected converter mainly includes a phase-locked loop (PLL) synchronization stage, an inner current loop control stage, a PWM modulation stage, and a filter stage. The PLL is used to detect the phase of the grid-connected voltage, providing a synchronization reference for current control; the inner current loop control stage generates a modulation wave based on the deviation between the command current and the actual feedback current; the PWM modulation stage converts the modulation wave into a switching signal; and the filter stage filters out high-order harmonics near the switching frequency. This topology and control structure are the basis for establishing the analytical model of the grid-connected converter's output impedance in step 1.

[0176] See Figure 3 As shown, the grid-type converter employs virtual synchronous machine control, mainly comprising a virtual synchronous machine control loop and a reactive power-voltage droop control loop. The virtual synchronous machine control simulates the rotor motion equations of a synchronous generator, providing inertia and damping support; the reactive power-voltage droop control maintains stable terminal voltage. This topology and control structure form the basis for establishing the analytical model of the grid-type converter's output impedance in step 3.

[0177] See Figure 4 As shown in the diagram, the overall flowchart of the optimization configuration method of this invention details the complete process from site modeling, impedance analysis, risk identification to the construction and solution of the optimization configuration model. This method determines the optimal network branch configuration scheme through four core steps: frequency domain discretization, impedance sensitivity linearization, mixed-integer linear programming solution, and iterative correction. The solution process is described in detail below:

[0178] First, perform initialization settings. Input the total number of branch lines in the station, as well as the known design parameters for each branch, including grid-type impedance, network-type impedance, collector line impedance, transformer impedance, grid impedance, target frequency range, gain margin, and phase margin. Set the linearization expansion point to a full grid-type initial configuration, assuming that all branches initially use grid-type control. Simultaneously, initialize the exclusion constraint set to an empty set and set the optimal solution search completion flag to an incomplete state.

[0179] Then, the iterative solution loop begins. In each iteration, the following four steps are executed sequentially:

[0180] The first step is frequency domain discretization. Within the specified target high-frequency band, several key frequency points are adaptively selected based on the degree of change in the impedance ratio curve. Intensified sampling is performed in frequency bands with drastic impedance ratio changes, while sparse sampling is performed in frequency bands with gradual changes, in order to reduce computational complexity while ensuring solution accuracy.

[0181] The second step is sensitivity coefficient calculation. For each selected key frequency point, the amplitude and phase of the overall impedance ratio of the hybrid system are calculated under the current linearized expansion point configuration. Subsequently, a trial switching analysis is performed on each branch: keeping the states of other branches unchanged, only this branch is switched from a follow-the-network type to a network-structure type, and the changes in the amplitude and phase of the impedance ratio at each frequency point are calculated after the switch. These changes represent the amplitude and phase sensitivity of this branch to the overall impedance characteristics of the station, reflecting the degree to which the branch modification contributes to the system stability.

[0182] The third step is to construct and solve the optimization model. Using the sensitivity coefficients calculated in the previous step, the nonlinear impedance stability constraints at each frequency point in the original problem are transformed into linear inequality constraints regarding the decision variables. Minimizing the total number of modified branches is taken as the optimization objective. Combined with the linearized amplitude constraints, phase constraints, integer constraints (decision variables taking values ​​of zero or one), and the exclusion inequalities already present in the exclusion constraint set, a standard mixed-integer linear programming model is constructed. The mixed-integer programming solver is then used to solve this model, obtaining a candidate configuration scheme that satisfies all linearization constraints.

[0183] The fourth step is precise verification and iterative correction. The candidate configuration schemes obtained in the previous step are substituted into the original, unlinearized nonlinear impedance calculation model to precisely calculate the impedance ratio amplitude and phase at each key frequency point. Frequency-by-frequency, it is checked whether the preset stability margin requirement is strictly met, i.e., the amplitude does not exceed the reciprocal of the amplitude margin, and the phase falls within the allowable range determined by the target phase margin. If all frequency points satisfy the constraints, the candidate scheme is accepted as the final optimal configuration scheme, the search completion flag is set to completion, and the iteration loop ends. If any frequency point does not satisfy the constraints, an exclusion inequality is constructed based on the currently infeasible candidate scheme, and it is added to the exclusion constraint set to avoid searching for this infeasible configuration again in subsequent iterations. Simultaneously, the current candidate scheme is used as the new linearization expansion point, returning to the second step to start a new round of iterative calculation. This process is repeated until the optimal solution satisfying all original nonlinear constraints is found.

[0184] Finally, after the iteration loop ends, the optimal configuration scheme found is output. Based on the values ​​of each decision variable in the scheme, the set of branch numbers that need to be transformed from follow-mesh control to network control is determined, and the minimum number of branches that need to be transformed is calculated, thus completing the entire optimization configuration process.

[0185] See Figure 5 The figure shows a comparison between the theoretical impedance of the grid-connected converter and the frequency sweep verification results. The solid line in the figure represents the calculated theoretical impedance model of the grid-connected converter based on the harmonic linearization method, while the scatter points represent the simulated values ​​obtained through frequency sweep verification on the electromagnetic transient simulation platform. As can be seen from the figure, the theoretical model and the simulation results are in high agreement across the entire frequency band, verifying the accuracy of the analytical model of the grid-connected converter's output impedance in step 1.

[0186] See Figure 6 The figure shows a comparison between the theoretical impedance of the grid-type converter and the frequency sweep verification results. The solid line in the figure represents the calculated result of the theoretical impedance model of the grid-type converter based on the harmonic linearization method, and the scatter points represent the simulated values ​​obtained from the frequency sweep verification in the electromagnetic transient simulation platform. As can be seen from the figure, the theoretical model and simulation results are in high agreement across the entire frequency band, and the grid-type converter exhibits positive damping characteristics in the impedance phase within the target high-frequency band, verifying the accuracy of the analytical model of the grid-type converter's output impedance in step 3.

[0187] See Figure 7 The figure shows a comparison of the station impedance characteristics under different configuration ratios of grid-connected and network-connected configurations. The figure illustrates the overall station impedance characteristics under three scenarios: full grid-connected control, 50% grid-connected branches, 50% network-connected branches, and full network-connected control. It can be seen that as the proportion of network-connected branches increases, the station's impedance phase in the high-frequency band gradually improves from negative damping to positive damping, verifying the reshaping effect of network-connected branches on the station's impedance characteristics. However, for the current scenario, the 50% grid-connected and 50% network-connected branch configurations cannot effectively suppress oscillations, while full network-connected control, although able to suppress high-frequency oscillations, reduces the system's dynamic response capability, further illustrating the necessity of optimized configuration.

[0188] See Figure 8 The figure shows the Bode plot of the impedance characteristics of a new energy power station when it adopts full grid-connected control. The figure shows that at approximately 910Hz, the impedance ratio amplitude is equal to 1 and the phase difference is greater than 180°, indicating that the system has an oscillation risk at this frequency. This figure corresponds to the process in step 2 of identifying the high-frequency oscillation risk of the system through impedance analysis.

[0189] See Figure 9 The figure shows the time-domain simulation waveform of the grid connection point voltage when the new energy power station adopts full grid-connected control. The system experiences high-frequency oscillations, with an oscillation frequency of approximately 910Hz. Figure 8 The Bode plot analysis results are consistent, verifying that the system under full-follower network control has a high-frequency oscillation risk.

[0190] See Figure 10The figure shows the Bode plot of the impedance characteristics of a new energy power station with a 50% grid-type branch configuration. The figure shows that at a frequency of approximately 1140Hz, the impedance ratio amplitude is equal to 1 and the phase difference is greater than 180°, indicating that even with a 50% grid-type branch configuration, the system may still have the risk of oscillation, and the oscillation frequency has changed.

[0191] See Figure 11 The figure shows the time-domain simulation waveform of the grid connection point voltage when the new energy power station adopts a 50% grid-type branch configuration. The system experiences high-frequency oscillations, with an oscillation frequency of approximately 1140Hz. Figure 10 The Bode plot analysis results are consistent, verifying that the current 50% mesh configuration is still insufficient to completely suppress high-frequency oscillations.

[0192] See Figure 12 As shown, the time-domain simulation waveform of the grid connection point voltage after applying the optimized configuration scheme of this invention is displayed. Using the optimal configuration scheme obtained in step 4, the selected scenario includes 18 new energy branches. The calculation shows that 12 branches were converted to grid-type control, i.e., the grid-type control ratio is 67%. In the simulation, the system voltage waveform quickly recovers to stability, with no obvious high-frequency oscillations. Figure 9 , Figure 11 As can be seen from the comparison, the method of the present invention effectively suppresses high-frequency oscillations with a smaller number of network-type branch modifications, namely 67% rather than all branches, thus verifying the effectiveness of the optimized configuration scheme.

[0193] In summary, this invention identifies the risk of high-frequency oscillations in the system by establishing accurate impedance models for grid-connected and grid-structured converters, establishing an optimal configuration model with the goal of minimizing the switching of grid-structured branches, and solving it using a mixed-integer programming method. Ultimately, it effectively suppresses high-frequency oscillations in the grid-connected system of new energy power plants with the modification of a small number of grid-structured branches. Simulation results verify the effectiveness and superiority of the method presented in this invention.

[0194] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made to the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the grid connection to suppress high-frequency oscillations in renewable energy power plants, characterized in that: By employing an optimized configuration method that combines grid-connected and grid-building control, some branches are selected for grid-building control to reshape the grid-connected impedance characteristics of renewable energy power plants, effectively suppressing high-frequency oscillations with the optimal number of modifications. This includes the following steps: Step 1: Establish analytical models of the output impedance of each grid converter based on the harmonic linearization method. Based on the topology, a aggregated output impedance model of the entire new energy power station is established. A detailed electromagnetic transient model of the new energy power station was established to verify the impedance model by frequency sweep. Step 2: Combine with the equivalent impedance of the actual power grid This study identifies oscillation risks in the high-frequency band of new energy power plant grid-connected systems based on impedance analysis; extracts key frequency bands for instability and negative damping characteristics; and determines the target frequency band and expected impedance compensation amount that require impedance reshaping through grid-connected converters. ; Step 3: Establish the analytical model of the output impedance of the grid converter The grid-type converter uses virtual synchronous machine control to ensure positive damping characteristics within the target frequency band; Step 4: Using whether each branch is converted to a network-type control as the decision variable, the optimal number of converted branches as the objective function, and the requirement that the overall impedance of the hybrid system meets the stability margin requirement as the constraint, an optimal configuration model is established. The optimal configuration model is solved using the mixed integer programming method to obtain the optimal network-type branch configuration scheme, thereby achieving the optimal configuration for suppressing high-frequency oscillations in new energy power stations with the minimum network-type conversion.

2. The method for controlling the grid connection to suppress high-frequency oscillations at renewable energy power plants according to claim 1, characterized in that: The analytical model of the output impedance of the grid converter described in step 1 The output impedance analytical model includes the effects of phase-locked loop dynamics, inner current loop control, filter parameters, and control delay; the aggregated output impedance model The aggregated output impedance model is obtained by paralleling and aggregating the impedances of each branch. It includes the influence of the impedances of the collector lines and the main transformer.

3. The method for tracking / grid control configuration for suppressing high-frequency oscillations in renewable energy power plants according to claim 2, characterized in that: The aggregated output impedance model of the new energy power station mentioned in step 1 is expressed as follows: ； In the formula: n is the total number of branch roads within the station; Let be the output impedance of the i-th branch connected to the grid converter; Let be the equivalent impedance of the collector line corresponding to the i-th branch; The equivalent impedance of the main transformer.

4. The method for controlling the grid connection to suppress high-frequency oscillations at renewable energy power plants according to claim 1, characterized in that: The identification of oscillation risk in step 2 uses the Nyquist criterion or the impedance ratio criterion. When the impedance ratio amplitude is 1 and the phase difference is greater than 180°, the system is determined to have oscillation risk.

5. The method for controlling the grid connection to suppress high-frequency oscillations at renewable energy power plants according to claim 1, characterized in that: The desired impedance compensation amount described in step 2 This is the equivalent impedance added at the grid connection point to ensure the system meets stability margin requirements; according to the impedance convergence principle, the overall impedance of the hybrid system after the grid-type branch modification is expressed as: ； In the formula: To maintain the number of branches in the network structure, To maintain the number of branches in the network structure; Let be the output impedance of the grid-type converter in the r-th branch; The target impedance ratio required for system stability is: ； After the renovation, the station impedance Represented as the aggregate output impedance model of a new energy power station Add the desired impedance compensation amount ; ； Then the expected impedance compensation amount Represented as: ； In the formula: Here, represents the equivalent impedance of the power grid; e represents the natural constant; GM is the target gain margin, and PM is the target phase margin. The values ​​of GM and PM are determined based on the actual requirements of the system; this applies to the target frequency band. The compensation amount should shift the impedance phase of the station in that frequency band towards the positive damping direction to ensure the impedance ratio. The Nyquist curve is far from the point (-1, j0).

6. The method for tracking / grid control configuration for suppressing high-frequency oscillations in renewable energy power plants according to claim 1, characterized in that, The optimized configuration model mentioned in step 4 is as follows: The objective function is: ； In the formula: N is the target configuration quantity; For decision variables; The constraints are: ； In the formula: n is the total number of branch roads within the station; The output impedance of the i-th branch when maintaining the mesh control; The output impedance when the i-th branch is converted to a network control system; Let be the equivalent impedance of the collector line corresponding to the i-th branch; The equivalent impedance of the main transformer; GM is the equivalent impedance of the power grid; PM is the target magnitude margin; GM is the target phase margin. For the high-frequency bands that need to be suppressed; Angular frequency; Angular frequency After the modification, the station impedance Angular frequency The equivalent impedance of the power grid at that time.

7. The method for tracking / grid configuration for suppressing high-frequency oscillations in renewable energy power plants according to claim 1, characterized in that: Solving the optimization configuration model described in step 4 includes the following sub-steps: Step 4.1: Frequency domain discretization of impedance stability constraints for the hybrid system of root / network; Step 4.2: Linearization of impedance sensitivity of network-type branches for optimized configuration. The perturbation method is used to calculate the sensitivity coefficient of each branch switching on the overall impedance characteristics of the station, transforming the nonlinear impedance constraint into a linear inequality; specifically: Define the overall impedance ratio function of the hybrid system as follows: ； At the initial unfolding point Linearization is performed at the specified location; Y represents the selection of Y key frequency points within the target high-frequency band. ; This is the angular frequency corresponding to the Qth frequency point; Angular frequency After the modification, the station impedance Angular frequency Equivalent impedance of the power grid at that time; express The absolute value of the amplitude of the ratio of the station impedance to the equivalent impedance of the power grid after the renovation; for The phase of the ratio of the station impedance to the equivalent impedance of the power grid after the modification; Step 4.3: Construction and solution of the hybrid control optimization configuration model of the linearized constraint and objective function. The linearized constraint and objective function are combined to form a hybrid integer linear programming model. The solver is called to obtain the candidate configuration scheme. Step 4.4: Stability verification and iterative correction of the optimized configuration scheme. Substitute the candidate configuration scheme into the original nonlinear impedance constraints for accurate verification. If all frequency points meet the stability margin requirements, the scheme is accepted as the optimal configuration scheme; otherwise, take the output of the current candidate configuration scheme as the new linearization expansion point, add exclusion constraints, and repeat steps 4.2 to 4.4 until a solution that meets the original constraints is found.

8. The method for tracking / grid control configuration for suppressing high-frequency oscillations in renewable energy power plants according to claim 7, characterized in that: The impedance sensitivity linearization process described in step 4.2 uses the perturbation method to calculate the sensitivity coefficient of each branch switching on the overall impedance characteristics of the station, transforming the nonlinear impedance constraint into a linear inequality.

9. A tracking / grid configuration system for suppressing high-frequency oscillations in renewable energy power plants, implementing the tracking / grid configuration method for suppressing high-frequency oscillations in renewable energy power plants according to any one of claims 1-8, characterized in that: include: The modeling module is used to establish analytical models of the output impedance of grid-connected converters and grid-connected converters, as well as aggregated output impedance models of new energy power plants. The risk identification module is used to identify oscillation risks in the high-frequency band of the grid-connected system of new energy power plants, and to determine the target frequency band and expected impedance compensation amount for impedance reshaping. The optimization configuration module is used to establish and solve the optimization configuration model to determine the optimal network branch configuration scheme; The control execution module is used to switch the selected network-type branch to network-type control according to the optimal network-type branch configuration scheme.

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