Wideband oscillation suppression method based on integration of oscillation feature extraction and network characteristic set

Abstract

The present application belongs to the technical field of power system control, and relates to a wide-frequency oscillation suppression method based on oscillation characteristic extraction and network characteristic integration, comprising: parallel extraction of independent state quantities of network and follow-up network channels, and analysis of oscillation characteristics through fast Fourier transform; calculation of oscillation frequency point impedance based on an output impedance model, and reverse calculation of integrated coefficients combined with a set target margin; weighting and integration of the two-channel state quantities by using the coefficients and input into a controller for execution; the present application remodels the equivalent output impedance of the converter from the bottom layer, essentially eliminates the negative resistance-capacitive frequency band causing oscillation, and effectively improves the stability margin, parameter robustness and adaptability to complex power grids of the grid-connected system.

Description

Technical Field

[0001] This invention belongs to the field of power system control technology, specifically relating to a broadband oscillation suppression method based on oscillation feature extraction and integrated network characteristics. Background Technology

[0002] In new power systems with a high proportion of renewable energy integration, renewable energy is connected to the grid via converters. Power electronic converters, acting as connection ports, differ from traditional synchronous machines in that their control algorithms are more flexible and can be designed according to control needs. Currently, there are two main control strategies: grid-following (GFL) control and grid-forming (GFM) control. To compensate for the equivalent inertia decay caused by the reduction in the number of traditional synchronous machines, GFM is widely used due to its independent voltage support capability.

[0003] Due to its control loop design, the GFM converter can be considered a voltage source with extremely low equivalent impedance. When connected to a strong power grid, it can be viewed as two voltage sources directly connected in parallel under strong grid conditions, which easily induces wideband oscillations (subsynchronous / supersynchronous oscillations, SSO) and leads to system instability. Furthermore, the stability margin decreases with increasing grid strength. Grid-following control, on the other hand, can better follow the main grid operation under strong grid conditions. There is a harmonization and integration range between the two characteristics. Through proper control design, not only can the wideband oscillations introduced by the GFM converter itself be avoided, but the system's dynamic performance and stability margin can also be further improved.

[0004] However, existing broadband oscillation suppression methods based on impedance reshaping are usually limited to a specific narrow frequency band. When the actual grid impedance changes, the dominant frequency and amplitude of the system's oscillation will drift accordingly, causing the original fixed suppression strategy to fail; at the same time, introducing an additional fixed virtual impedance element often affects and deteriorates the control performance of other frequency bands.

[0005] Therefore, a method is needed to identify and dynamically suppress oscillations in order to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention aims to provide a broadband oscillation suppression method based on oscillation feature extraction and grid-connected characteristics integration, which solves the risk of broadband oscillations (subsynchronous / supersynchronous oscillations) caused by three-phase grid-connected inverters with grid-connected control under strong grid conditions, thereby improving system stability margin and robustness.

[0007] This invention provides the following technical solution: a broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration, comprising the following steps: Step 1: In the controller of the new energy grid-connected inverter, construct parallel-running grid-type control channels and grid-following control channels, and extract the independent state variables of the grid-type control channels and grid-following control channels. In the digital controller of the grid-connected inverter, construct grid-type control channels and grid-following control channels as virtual parallel-running controllers, which constitute two independent control characteristic channels.

[0008] Among them, the grid-type control channel can be a typical structure of any of the following: virtual synchronous generator control, droop control, and inertial matching control. Taking virtual synchronous generator control as an example, it is used to generate frequency based on active power deviation, generate voltage based on reactive power deviation, and further generate current reference information. The grid-type control channel GFL is used to generate synchronous phase based on the phase-locked loop voltage result at the grid connection point, and combined with the given current reference information, the grid-type control can be a current vector control based on phase-locked loop.

[0009] The state variable vector extracted from the network-type control channel is represented as follows:

[0010] in, The synchronization phase angle is generated independently for the network channel; and These are the d-axis and q-axis inductor current reference values ​​obtained from the voltage regulation loop for the network channel.

[0011] Simultaneously, extract the output state variable matrix generated based on the network-type control strategy logic.

[0012] in, The synchronization phase angle is generated independently for the network channel; and These are the d-axis and q-axis inductor current reference values ​​used by the network channel.

[0013] This creates two independent control characteristic channels that can be computed in parallel, providing basic variable inputs for subsequent characteristic integration after oscillation identification.

[0014] Step 2: Real-time acquisition of voltage and current signals at the grid-connected inverter connection point, performing Fast Fourier Transform to extract broadband oscillation characteristics, and identifying the dominant frequency and amplitude of abnormal oscillation components. Real-time acquisition of the three-phase voltage at the grid connection point of the three-phase grid-connected inverter. and three-phase current After sampling period Discretized sampling to obtain current sequence Frequency domain analysis of the grid connection point current signal yields the following expression for the discrete frequency domain sequence:

[0015] in, It is the complex spectrum value corresponding to the kth discrete frequency point; This represents the sequence of sampled values ​​of the three-phase current at the grid connection point at the nth sampling time. N This is the length of the FFT analysis window; n The sampling point number; k Frequency domain index; j It is the imaginary unit.

[0016] Based on the spectral results, the amplitude of the abnormal oscillation component in the frequency domain is extracted in real time. I osc and its dominant frequency f osc Set the safety threshold as I th When the following numerical relationship is satisfied:

[0017] If the system experiences subsynchronous or supersynchronous wideband oscillations at a non-fundamental frequency, then the corresponding dominant frequency is recorded. f osc As the object that needs to be suppressed. Among them, This refers to the grid's fundamental frequency, such as 50Hz. Furthermore, considering the sequence component interaction characteristics of a three-phase grid-connected system under frequency coupling effects, when the system... f osc When oscillation occurs at a certain frequency, in addition to the small-signal response at the corresponding frequency, there will also be an oscillation at the coupling frequency. The mirror response component is generated at this point. Therefore, the oscillation features extracted in this step are not only used for time-domain oscillation identification, but also serve as key interaction frequencies characterizing machine-network coupling, providing target frequency input for subsequent evaluation of the equivalent impedance model and strategy improvement.

[0018] Step 3: Obtain the white-box parameters of the internal controller of the grid-connected converter, establish an analytical model of the single-input single-output (SISO) equivalent positive-sequence output impedance of the converter port in the complex frequency domain, and calculate the frequency impedance and stability margin at the dominant frequency. Since the control strategy used by the internal controller of the grid-connected converter is artificially designed and the control parameters are known, an analytical model of the single-input single-output (SISO) equivalent positive-sequence output impedance of the converter port in the complex frequency domain s is established. Controller parameters include virtual inertia. J Inertia coefficient D p Voltage coefficient K, voltage droop coefficient D, voltage loop integral coefficient K vi Voltage loop proportionality coefficient K vp Phase-locked proportional gainK lp Phase-locked loop integral coefficients K li Integral coefficient of current loop K ii Current loop proportionality coefficient K ip Etc., PWM modulation coefficients, etc.

[0019] The oscillation frequency extracted in step 2 f osc Substitution operator:

[0020] The equivalent positive-sequence output impedance of the converter at this oscillation frequency is obtained as follows:

[0021] in, This is the equivalent resistance component at the oscillation frequency. This is the equivalent reactance component at the oscillation frequency. When the system is... f osc When a wide-frequency oscillation occurs, the converter and the power grid reach the resonant instability boundary at this frequency. Based on this critical resonance condition, the equivalent inductance characterizing the power grid strength can be... Perform inverse estimation:

[0022] This leads to the analytical expression for the equivalent impedance of the power grid under the current operating conditions:

[0023] in, The equivalent inductance is used to characterize the strength of the power grid.

[0024] Based on the Nyquist stability criterion based on impedance ratio, and utilizing the amplitude-phase interaction relationship:

[0025] Calculate the interactive stability margin (including phase margin and magnitude margin) between the converter and the power grid at this frequency point to quantify the instability risk of the system and provide benchmark parameters for subsequent control.

[0026] Step 4: Introduce network integration coefficients and follow-network integration coefficients that satisfy complementary relationships, and perform linear weighted integration on the independent state variables extracted in Step 1 to obtain the fused global state variable vector. Introduce network integration coefficients and follow-network integration coefficients that satisfy complementary relationships, respectively corresponding to… , And it satisfies:

[0027] The network channel state variable vector extracted in step 1 With network channel state variable vector Perform linear integration to obtain the fused global state variable vector:

[0028] Right now:

[0029] in,

[0030] in, For global synchronization phase angle, and These are the integrated d-axis and q-axis current reference values, respectively. By uniformly weighting the synchronization information and current commands, a global control input is formed that simultaneously possesses network support characteristics and network impedance stability characteristics.

[0031] Step 5: Set the target lift margin. Based on the target lift margin and the equivalent positive-sequence output impedance analytical model, calculate the network integration coefficient and the grid integration coefficient that meet the system stability requirements. Addressing the oscillation frequency and insufficient stability margin issues identified in Step 3, a target lift margin is set. h Target to increase margin h The desired improvement in system stability after compensation can be represented by the target phase margin increment as a constraint.

[0032] Under dual-channel integration conditions, the equivalent output impedance of the converter It is about Nonlinear analytic functions:

[0033] in, This represents the impedance mapping relationship determined by the control channel weights, controller parameters, and main circuit parameters. Furthermore, at the oscillation frequency... f osc Construct constraint equations that satisfy the target stability margin h, and obtain the corresponding network integration coefficients:

[0034] In the formula, This is an inverse solver based on the analytical characteristics of impedance at frequency points (i.e., the inverse mapping function from impedance to coefficients). Using this operator, the value that exactly compensates for the margin can be directly calculated within the interval 0 to 1. h Appropriate fixed value and accordingly obtain .

[0035] Step 6: Based on the global state variable vector obtained in Step 4 and the integration coefficients calculated in Step 5, generate a global fused current command and input it to the inner current loop controller for closed-loop control to reshape the system port equivalent impedance and suppress broadband oscillations. The inner current loop controller is a unified current controller for both channels of the network, and its input variables are the integrated d-axis and q-axis current reference values. The global fused current command obtained in Step 5 is then used... , With the actual sampled current , The comparisons are then input into the inner current loop controller with cross-coupling terms. The q-axis control law is implemented in a symmetrical form corresponding to the d-axis. Taking the d-axis as an example, its control law is:

[0036] in, This is a d-axis modulation voltage command; To be synchronized by global phase angle The calculated global synchronization angular frequency; For filtering inductors; The voltage component along the d-axis at the grid connection point.

[0037] Subsequently, based on the fused global synchronization phase angle The coordinate transformation is completed, and the switching signals for driving the power devices of the inverter bridge are generated through the pulse width modulation unit to realize closed-loop control of the grid-connected inverter.

[0038] Due to integration coefficient At the control level, the equivalent impedance of the system ports was reshaped in a directional manner, causing the oscillation frequency to... f osc The surrounding area exhibits unfavorable negative resistive-capacitive characteristics. It satisfies:

[0039] in, This is an operator that takes the real part of a complex number. This mechanism fundamentally fills in the negative damping region that induces resonant instability, preventing the system impedance ratio Nyquist curve from encircling the critical point. This enables rapid, directional suppression of wideband oscillations.

[0040] After the oscillation amplitude falls below the preset safety threshold, the system can continue to operate in this integrated state, or smoothly transition to the grid-based control-dominated mode according to grid demand. This eliminates the risk of wideband oscillations while preserving the converter's grid voltage support and synchronization establishment capabilities without loss, avoiding secondary stability problems caused by hard switching from traditional single control modes.

[0041] The beneficial effects of this invention are: 1. This invention can implement targeted suppression for actual oscillation frequencies, improving the pertinence of broadband oscillation management: This invention does not passively correct local frequency band characteristics by adding virtual impedance or changing control loops, but instead achieves state variable integration with the grid channel, directly changing the external characteristics of the converter port. This can reduce the negative impact of traditional local compensation schemes on non-target frequency bands. Therefore, this invention is more suitable for grid-connected scenarios with significant changes in operating conditions and strong grids.

[0042] 2. This invention can improve the robustness of the system under various power grid conditions. The invention adopts an optimized control strategy configuration process of oscillation feature extraction, equivalent impedance calculation, and coefficient inverse calculation. It can be quantitatively adjusted according to changes in power grid strength, control parameter deviation, and operating mode. It can also improve the system's adaptability to controller parameter perturbations and external impedance fluctuations. It is suitable for complex power grid environments with a high proportion of new energy penetration and effectively achieves good stability and voltage support capability of grid-connected converters.

[0043] 3. This invention can balance the support capability of grid-based control with impedance stability under strong grid conditions. By establishing a continuously adjustable trade-off between grid-based characteristics and grid-following characteristics through normalized integration coefficients, this invention can retain the advantages of grid-based control in voltage support, synchronization establishment, and weak grid adaptation. On the other hand, it can use the more favorable impedance characteristics of grid-following control under strong grid conditions to correct the negative damping region, thereby improving the overall operating performance of the system under different grid intensities. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the control method of the broadband oscillation suppression method based on oscillation feature extraction and root structure network characteristics integration of the present invention; Figure 2 This is a control topology diagram of the network-type control (virtual synchronous machine control) of the present invention; Figure 3 This is a control topology diagram of the grid-type control (constant current control) of the present invention; Figure 4 This is a fast Fourier transform result of the power grid intensity fluctuation of the present invention, which generates wideband oscillation after switching from an equivalent inductance of 5mH to 3mH. Figure 5 The fast Fourier transform result of the wideband oscillation generated after the perturbation of the network control parameters (voltage loop proportional coefficient) of the present invention from 20 to 2 is shown. Figure 6 This is the control block diagram for the weighted integration of angular velocity state variables of the present invention for both network-type and follow-network-type networks; Figure 7 This is a control block diagram for the weighted integration of inductor current reference value state variables in both grid-type and follow-grid-type configurations, as described in an embodiment of the present invention. Figure 8 This is a schematic diagram comparing the stability margins of traditional grid-type control strategies when the power grid intensity is changed from strong to weak according to the present invention. Figure 9 This is a schematic diagram of the output power of the two systems when the power grid intensity is changed from strong to weak according to the present invention; Figure 10 This is a schematic diagram illustrating the control effect of the present invention under power grid intensity fluctuations, from grid-based control to integrated grid control.

[0045] Figure 11 This is a schematic diagram illustrating the control effect of switching from network-based control to integrated network control under the perturbation of the network-based control parameters (voltage loop proportional coefficient) of this invention. Detailed Implementation

[0046] The relevant technologies of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0047] like Figures 1-11 As shown, this embodiment presents a broadband oscillation suppression method based on oscillation feature extraction and grid-connected characteristics integration. In new power systems with a high proportion of renewable energy integration, grid-connected converters are prone to subsynchronous / supersynchronous oscillations (SSOs) when connected to a strong grid or when control parameters are perturbed. This invention introduces a complementary approach, achieving weighted integration of grid-connected and grid-connected commands at the control layer, fundamentally reshaping the equivalent output impedance of the converter, thereby eliminating the key negative resistive-capacitive frequency band that triggers oscillations.

[0048] Step 1: Establish and extract independent state variables for the network construction channel and the network tracking channel. In one embodiment of the present invention, such as... Figure 1 The proposed digital controller strategy is applied in the power grid system where the grid-connected converter shown is located. In the controller, a grid-connected control channel and a grid-following control channel are constructed and virtually run in parallel to extract their respective independent characteristic parameters.

[0049] Combination Figure 2 As shown, this embodiment of the invention provides a control topology diagram for the main components of a network-based control system (taking virtual synchronous machine control as an example). This network channel is based on power synchronization and voltage support mechanisms, forming synchronization angle and voltage outer loop references by simulating rotor and stator equations. Therefore, the state variable vector of the network channel is extracted. ,in Synchronization phase angle generated for network construction channels and These are the reference values ​​for the d-axis and q-axis currents, respectively.

[0050] Combination Figure 3 As shown, this embodiment of the invention provides a control topology diagram for the main components of a grid-following control (constant current control). This grid-following channel generates synchronization information based on a phase-locked loop (PLL) and combines it with a current loop to generate a current reference. Therefore, the state variable vector of the grid-following channel is extracted. .

[0051] Step 2: Perform wideband oscillation feature extraction based on Fast Fourier Transform. Real-time acquisition of voltage and current signals at the connection point of the three-phase grid-connected inverter is performed. After discretization sampling, the amplitude of abnormal oscillation components in the frequency domain is extracted using Fast Fourier Transform (FFT). I osc and its dominant frequency f osc In actual power grids, there are various severe operating conditions that can induce oscillations: such as... Figure 4 As shown, when the system encounters fluctuations in grid strength and the equivalent inductance suddenly drops from 5mH to 3mH (simulating a scenario of enhanced grid strength), the time-domain waveform deteriorates sharply, resulting in a wideband oscillation with a frequency of 35Hz / 65Hz.

[0052] like Figure 5 As shown, the voltage outer loop proportional coefficient of the network controller is known. K vp It has a significant impact on the stability margin when this control parameter is perturbed. K vp When the voltage suddenly drops from 20 to 2, with a grid equivalent impedance of 3mH, it causes a wideband oscillation with a frequency of 35Hz / 65Hz in the system. This can be mitigated by setting a safety threshold. I th and power grid base frequency (e.g., 50Hz), when determining At that time, the system records the dominant frequency. f osc As a suppression target, considering the frequency coupling effect, the coupling frequency is also extracted. The mirror response component at that point is used for subsequent impedance modeling and margin assessment.

[0053] Step 3: Calculate the impedance at the oscillation frequency based on controller parameters and evaluate the stability margin. Due to the frequency coupling effect caused by the asymmetric control of the voltage / current inner and outer loops in traditional network control, its positive sequence output impedance often exhibits severe negative RC characteristics in the subsynchronous / supersynchronous frequency band. Combined with the extracted dominant oscillation frequency... f osc， Establish an analytical model of the equivalent positive-sequence output impedance of the single-input single-output (SISO) converter port. and substitute into the operator Calculate the impedance at the frequency point.

[0054] like Figure 8 and Figure 9 As shown, based on the Nyquist stability criterion based on impedance ratio, the amplitude-phase interaction relationship is utilized. The interaction stability margins (including phase and magnitude margins) between the converter and the grid at this frequency are calculated to quantify the system's instability risk and provide baseline parameters for subsequent control. When the grid strength changes from strong to weak, traditional grid-based control strategies exhibit significant limitations. Under strong grid conditions, the Nyquist curve expands significantly outward due to the grid-machine interaction (impedance as the denominator decreases in absolute value but increases in overall value), and encircles the critical point from the left. This leads to severe negative damping characteristics and divergent instability in the system; however, under weak grid conditions, the curve contracts, allowing the system to remain stable. The calculations in this step can accurately quantify the missing phase margin and amplitude margin under the current operating conditions.

[0055] Step 4: Perform network integration based on state vector weighting. Introduce network integration coefficients that satisfy complementary relationships. Integration coefficient with network ,in The independent state variables extracted in step 1 are normalized and linearly weighted within the interval of 0 to 1.

[0056] like Figure 6 The diagram shows the control block diagram for weighted integration of angular velocity state variables for both network-type and follow-network-type systems, and the global synchronization phase angle is calculated. .

[0057] like Figure 7 The diagram illustrates the control block diagram for weighted integration of inductor current reference state variables in both network-based and root-based configurations, calculating the global command current. and This dual-channel fusion mechanism unifies synchronization information and current commands at the control level, enabling the system to possess both network support capabilities and stable network impedance characteristics in terms of external properties.

[0058] Step 5: Perform back-calculation of the target improvement margin and integration coefficients. Addressing the insufficient stability margin issue revealed in Step 3, a target improvement margin characterizing the system's stability improvement is set. h Under integrated conditions, the equivalent output impedance It is about The nonlinear analytical function. The margin is improved by constructing a function that satisfies this objective. hThe constraint equations are used to introduce a reverse solution operator based on the analytical characteristics of frequency impedance. :

[0059] in, This represents the complex impedance at the grid boundary, determined by both equivalent resistance and equivalent inductance. Using this operator, the compensation margin can be accurately calculated while fully considering line damping and inductive coupling. h The appropriate value required And obtain accordingly This inverse calculation process directly transforms the controller parameter design into explicit frequency domain coefficient tuning.

[0060] Step 6: Execute the closed-loop control to suppress oscillations and restore normal operation. Input the global fused current command to the inner current loop controller with cross-decoupling terms to drive the grid-connected inverter. Because the integration coefficients directionally reshape the system's equivalent positive sequence impedance at the control level, correcting the negative RC characteristics that caused the oscillations, the equivalent impedance at the specified point satisfies:

[0061] To demonstrate the control effect of this invention, an electromagnetic transient simulation model was built using Matlab / Simulink, showing a three-phase converter connected to the AC power grid via an equivalent impedance. The equivalent resistance was used to simulate the line impedance, and the testing focused on the extremely challenging purely inductive extreme condition (i.e., approximately ignoring line resistance). To dynamically adjust the power grid intensity.

[0062] The specific parameters of the system are shown in Table 1.

[0063]

[0064] In a dynamic test scenario simulating power grid strength fluctuations, the system initially operates stably under relatively weak power grid conditions (e.g., a high equivalent inductance). Subsequently, t = t 1. A sudden change in grid strength causes a significant drop in equivalent inductance (e.g., a decrease in the short-circuit ratio). If the system maintains only traditional single-grid control at this time, the three-phase current at the grid connection point will experience critical broadband oscillations after the sudden change. (Combined with...) Figure 4 The frequency domain analysis shows that the system excites significant high-amplitude subsynchronous / supersynchronous oscillations at non-fundamental frequencies (around 35Hz and 65Hz).

[0065] Combination Figure 10 The given time-domain waveform diagram of the control effect under power grid intensity fluctuations allows for a more intuitive observation of this dynamic evolution process. This oscillation characteristic is extracted from the system and... t = t2. After implementing the integrated control based on the grid characteristics proposed in this invention, the simulation waveform clearly shows that as the target improvement margin is supplemented and the integration coefficient takes effect, the oscillation envelope of the grid-connected current converges rapidly, and the system re-establishes equilibrium in a very short time. This set of time-frequency domain comparison experiments proves that this invention endows the converter with adaptability under conditions ranging from a strong grid to an even stronger grid.

[0066] Furthermore, to assess the control system's tolerance to internal parameter perturbations, the embodiment conducted a test on sudden changes in the controller's white-box parameters. This was done when key parameters of the network channel (such as the voltage loop proportional gain) were affected. K vp When subjected to a severe disturbance (a sudden drop from the nominal value of 20 to 2), the impedance phase-frequency characteristics of the original grid control system deviate significantly. At the instant of this parameter change, the grid-connected current under traditional control immediately loses stability, and the three-phase current at the grid connection point experiences critical broadband oscillations. For example... Figure 5 The frequency domain analysis shows that the system excites significant high-amplitude subsynchronous / supersynchronous oscillations at non-fundamental frequencies (around 35Hz and 65Hz).

[0067] Corresponding to Figure 11 In the time-domain transient waveform diagram, after the system executes closed-loop control and seamlessly integrates with the grid structure, the damping advantage of the grid connection channel is precisely introduced and compensates for the negative damping defect of the grid structure channel by weighting the internal state variables. The time-domain results verify that the three-phase current quickly filters out the oscillating components after the integrated control is implemented, perfectly restoring to a high-quality grid-connected operation state. This fully demonstrates that the proposed integrated control strategy can not only resist the severe fluctuations of the external grid structure, but also significantly broaden the stability margin boundary of the system to the drift of internal control parameters.

[0068] In summary, this invention extracts the independent state variables of the grid-connected and grid-connected channels in parallel, analyzes the oscillation characteristics using Fast Fourier Transform, calculates the impedance at the oscillation frequency based on the output impedance model, and calculates the integration coefficient in reverse by combining the set target margin. This coefficient is then used to weight and integrate the state variables of the two channels and apply them to the controller for execution. This invention fundamentally reshapes the equivalent output impedance of the converter, essentially eliminating the negative resistive-capacitive frequency band that causes oscillations, effectively improving the stability margin, parameter robustness, and adaptability to complex power grids of the grid-connected system.

[0069] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration, characterized in that, Includes the following steps: Step 1: In the controller of the new energy grid-connected inverter, construct parallel-running grid-type control channels and grid-following control channels respectively, and extract the independent state variables of the grid-type control channels and the grid-following control channels; Step 2: Real-time acquisition of voltage and current signals at the grid-connected inverter connection point, and fast Fourier transform to extract broadband oscillation characteristics and identify the dominant frequency and amplitude of abnormal oscillation components; Step 3: Obtain the white-box parameters of the internal controller of the grid-connected converter, establish the single-input single-output equivalent positive-sequence output impedance analytical model of the converter port in the complex frequency domain, and calculate the frequency impedance and stability margin at the dominant frequency. Step 4: Introduce network integration coefficients and follow-network integration coefficients that satisfy complementary relationships, and perform linear weighted integration on the independent state variables extracted in Step 1 to obtain the fused global state variable vector. Step 5: Set the target lift margin, and based on the target lift margin and the equivalent positive sequence output impedance analytical model, calculate the network integration coefficient and the network integration coefficient that meet the system stability requirements. Step 6: Based on the global state variable vector obtained in Step 4 and the integration coefficient calculated in Step 5, generate a global fusion current command and input it to the current inner loop controller for closed-loop control to reshape the equivalent impedance of the system port and suppress wideband oscillation.

2. The broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration according to claim 1, characterized in that, In step 1, the independent state variables include: State variable vector extracted from the network-type control channel: in, The synchronization phase angle is generated independently for the network-type control channel. and These are the d-axis and q-axis inductor current reference values ​​obtained by the voltage regulation loop for the network-type control channel. State variable vector extracted from the network control channel: in, The synchronization phase angle is generated independently of the network control channel; and These are the d-axis and q-axis inductor current reference values ​​used by the mesh control channel.

3. The broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration according to claim 1, characterized in that, In step 2, the discrete frequency domain sequence expression for frequency domain analysis of the three-phase current signal at the grid connection point is: in, It is the complex spectrum value corresponding to the k-th discrete frequency point. This represents the sequence of sampled values ​​of the three-phase current at the grid connection point at the nth sampling time. N The length of the FFT analysis window. n The sampling point number, k For frequency domain index, j The imaginary unit; Given the base frequency of the power grid f In a signal of 1, the amplitude of the abnormal oscillation component in the frequency domain is extracted in real time. I osc and its dominant frequency f osc Set the safety threshold as I th When the conditions are met and At that time, it is determined that the system is experiencing wideband oscillation; simultaneously, the image response component under the frequency domain coupling effect is extracted, and the corresponding coupling frequency is... .

4. The broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration according to claim 1, characterized in that, In step 3, the dominant oscillation frequency is... f osc Substitution Operator The equivalent positive-sequence output impedance of the converter at the oscillation frequency point is obtained as follows: in, This is the equivalent resistance component at the oscillation frequency. The equivalent reactance component at the oscillation frequency; reverse estimation of the equivalent inductance of the power grid. This leads to the analytical expression of the equivalent impedance of the power grid under the current operating conditions. Utilizing amplitude-phase interaction: Calculate the interaction stability margin between the converter and the power grid at this frequency point, including phase margin and magnitude margin.

5. The broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration according to claim 1, characterized in that, In step 4, the network integration coefficient Integration coefficient with network Satisfying Relationship: The merged global state variable vector is: in, For global synchronization phase angle, and These are the integrated d-axis and q-axis current reference values, which together form the global fused current command.

6. The broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration according to claim 1, characterized in that, In step 5, the equivalent output impedance of the converter is: in, This represents the impedance mapping relationship determined by the control channel weights, controller parameters, and main circuit parameters. The specific method of the reverse calculation is as follows: at the oscillation frequency The construction of the site meets the target and improves the margin. h From the constraint equations, the corresponding mesh integration coefficients are obtained: In the formula, For the inverse solver based on the analytical characteristics of frequency-point impedance, the equivalent impedance of the power grid is... ,in, and The equivalent resistance and equivalent inductance characterize the grid strength; the values ​​that can be directly calculated in the range of 0 to 1 are used to precisely compensate for this margin. h fixed value and accordingly obtain .

7. The broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration according to claim 1, characterized in that, In step 6, the inner current controller is a unified current controller for both channels of the network. The input variable of the inner current controller is the globally fused current command, and the d-axis control law of the inner current controller is: in, This is a d-axis modulated voltage command. To be synchronized by global phase angle The calculated global synchronization angular frequency, For filtering inductors, The d-axis voltage component at the grid connection point. , This is the actual sampling current; Through integration coefficient The directional reshaping makes the oscillation frequency f osc The negative resistive-capacitive characteristics in the vicinity are weakened or eliminated, satisfying: in, It is an operator that takes the real part of a complex number; thus, it enables rapid suppression of the dominant oscillation frequency band.

8. A grid-connected inverter control device, characterized in that, The control device is used to implement the broadband oscillation suppression method according to any one of claims 1 to 7, and the control device comprises: Memory, used to store computer programs; A processor for executing steps of a broadband oscillation suppression method based on oscillation feature extraction and root network characteristic integration.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the broadband oscillation suppression method as described in any one of claims 1 to 7.

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