Wind power system composite oscillation suppression strategy and system based on static synchronous compensator

Abstract

The invention discloses a wind power system composite oscillation suppression strategy and system based on a static synchronous compensator, and the strategy comprises the steps: firstly constructing a sequence impedance model of a GFM-STATCOM and an equivalent wind turbine generator (EWTG) based on a wind power output system containing the GFM-STATCOM; combining the impedance contribution degree beta, analyzing the interaction between the two, and determining the oscillation risk dominant factor of the sub / super-synchronous frequency band; and finally, performing frequency-band suppression: aiming at the problem of negative damping dominance of the subsynchronous frequency band GFM-STATCOM, adopting a control parameter optimization strategy based on parameter sensitivity, and reducing a reactive loop integral coefficient by increasing virtual resistance so as to reduce a negative damping range. In order to solve the problem of negative damping leading of a super-synchronous frequency band EWTG, a virtual admittance control strategy based on voltage feedforward is adopted to reduce the output impedance amplitude of a GFM-STATCOM, the leading position of positive damping of the GFM-STATCOM is enhanced, and then the negative damping of the system is eliminated. According to the invention, precise suppression of composite oscillation is realized, and the stability of a wind power sending system under a weak power grid is improved.

Description

Technical Field

[0001] This invention relates to the field of wind power grid connection and power system stability control technology, specifically to a composite oscillation suppression strategy and system for wind power systems based on a static synchronous compensator. Background Technology

[0002] With the large-scale grid connection of new energy sources, represented by wind power, large-capacity reactive power compensation devices are typically required for new energy power plants to meet grid specifications and improve wind farm operation performance. Among these, the Cascaded H-Bridge (CHB) Static Synchronous Compensator (STATCOM) has been widely used in medium- and high-voltage scenarios due to its modular design, high voltage level, and flexible control. However, as a typical power electronic converter, the traditional grid-following (GFL) STATCOM exhibits complex negative damping characteristics. Its connection to a wind farm exacerbates the interaction between the converter and the grid, easily inducing oscillation problems, posing a serious challenge to the safe grid connection and stable absorption of large-scale new energy sources.

[0003] Impedance-based stability analysis is one of the mainstream methods for studying oscillation problems. Currently, impedance modeling and stability analysis for CHB-STATCOM are relatively well-developed. However, existing research only considers the case where CHB-STATCOM is connected to the system in a grid-based control manner. GFL-STATCOM exhibits significant negative damping over a wide frequency band due to the interaction between the PLL and grid-side impedance, and oscillation suppression strategies are prone to failure when grid-side impedance or operating conditions change. Therefore, applying grid-forming (GFM) technology to the control modification of GFL-STATCOM can enhance voltage support capability and improve adaptability to weak grids to some extent, and has received widespread attention in recent years. Considering the DC-side energy limitations of STATCOM, directly improving the control strategy through grid-forming on the basis of conventional capacitor-equipped STATCOMs—that is, GFM-STATCOM without adding energy storage—is of great significance for improving the stability of large quantities of existing GFL-STATCOMs.

[0004] Current research on GFM-STATCOM mainly focuses on control strategy optimization and transient performance analysis. Some studies have begun to explore the impedance characteristics of GFM-STATCOM and its impact on system stability. However, existing studies are all based on two-level topologies, while CHB-STATCOM differs significantly from two-level topologies in terms of main circuit, control strategy, and harmonic characteristics, and its impedance characteristics still need further analysis. Furthermore, the mechanism by which GFM-STATCOM interacts with large-scale wind farms on system stability remains unclear. Therefore, it is necessary to establish an impedance model for grid-connected CHB-STATCOM without energy storage, thereby revealing its impact on wind power transmission systems from the perspective of impedance mechanisms and proposing corresponding oscillation suppression strategies. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a strategy and system for suppressing composite oscillations in wind power systems based on static synchronous compensators (SRCs). Through a composite impedance reshaping approach, on the one hand, control parameter optimization based on parameter sensitivity is used to eliminate its own subsynchronous negative damping; on the other hand, virtual admittance control based on voltage feedforward is used to enhance its ability to suppress the negative damping of wind turbine generators in the supersynchronous frequency band. This achieves precise suppression of composite oscillations in the system and improves the stability of wind power transmission systems with grid-type SRCs in weak power grids.

[0006] This invention is achieved through the following technical solution: In a first aspect, this application provides a composite oscillation suppression strategy for wind power systems based on static synchronous compensators, comprising the following steps: Step 1: Based on the wind power transmission system including the grid-type static synchronous compensator, construct the impedance model of the grid-type static synchronous compensator and the equivalent wind turbine, and combine the impedance models of the grid-type static synchronous compensator and the equivalent wind turbine to construct the sequence impedance model of the wind power transmission system. Step 2: Based on the sequence impedance model and in conjunction with the impedance contribution. β The interaction between the grid-type static synchronous compensator and the equivalent wind turbine was analyzed, and the dominant factors for the oscillation risk of the wind power transmission system in the subsynchronous / supersynchronous frequency band were determined based on the interaction. Step 3: Based on the dominant factors of subsynchronous frequency band oscillation risk, a control parameter optimization strategy based on parameter sensitivity is adopted. By changing the control parameters of the grid-type static synchronous compensator, the virtual resistance is increased and the reactive power loop integral coefficient is decreased, thereby reducing the negative damping range of the subsynchronous frequency band and suppressing the oscillation of the subsynchronous frequency band. Based on the dominant factors of oscillation risk in the supersynchronous frequency band, a voltage-feedforward-based virtual admittance control strategy is adopted to reduce the impedance amplitude of the grid-type static synchronous compensator output, enhance its positive damping dominance, eliminate the negative damping of the converter-side equivalent impedance in the supersynchronous frequency band, and thus suppress oscillation in the supersynchronous frequency band.

[0007] Preferably, the method for constructing the sequence impedance model of the wind power transmission system is as follows: Based on the multi-harmonic linearization method, the main circuit small-signal model and control system small-signal model of the grid-type static synchronous compensator and the equivalent wind turbine are derived respectively, and the frequency coupling effect is considered in the modeling process. Based on the small-signal model of the main circuit and the small-signal model of the control system, the multi-input multi-output impedance models of the AC side of the grid-type static synchronous compensator and the equivalent wind turbine are determined respectively. The multi-input multi-output impedance model of the grid-type static synchronous compensator and the equivalent wind turbine is converted into the equivalent positive-sequence and negative-sequence single-input single-output sequence impedance model of the wind power transmission system.

[0008] Preferably, the expression for the order impedance model is as follows:

[0009] in, Y gp and Y gn These are the positive and negative net-side admittances, respectively.

[0010] Preferably, the step of basing the impedance model on the order impedance model and combining the impedance contribution is... β This study analyzes the interaction between grid-type static synchronizing compensators and equivalent wind turbine units, and identifies the dominant factors contributing to the oscillation risk of wind power transmission systems in the subsynchronous / supersynchronous frequency bands based on this interaction. These factors include: A certain amount of disturbance is applied to the original impedance of the equivalent wind turbine and the grid-type static synchronous compensator, and the equivalent impedance on the converter side is used as the basis for the disturbance. Z eq-GFM The change yields the impedance sensitivity of the equivalent wind turbine and the grid-type static synchronous compensator output. δ, Then determine the corresponding impedance contribution. β ; Based on impedance contribution β Determine the effect of negative damping of the equivalent wind turbine and grid-type static synchronous compensator on the equivalent impedance of the converter side in different frequency bands. Z eq-GFM Dominant position; Negative damping, which dominates at different frequency bands, is considered the primary factor in oscillation risk.

[0011] Preferably, the dominant factor for the subsynchronous frequency band oscillation risk is the negative damping of the grid-type static synchronous compensator.

[0012] Preferably, the dominant factor in the risk of supersynchronous frequency band oscillation is the negative damping of the equivalent wind turbine.

[0013] Preferably, the impedance sensitivity of the equivalent wind turbine and the grid-type static synchronizing compensator outputs... δ, Then determine the corresponding impedance contribution. β ,as follows:

[0014]

[0015] in, Z EWTG This is the equivalent impedance of the wind turbine. Z GFM-STATCOM The impedance of the grid-type static synchronous compensator. Z eq The equivalent impedance on the converter side. δ This corresponds to the impedance sensitivity. β This represents the corresponding impedance contribution.

[0016] Preferably, based on the dominant cause of negative damping in the supersynchronous frequency band, a virtual admittance control strategy based on voltage feedforward is adopted to enhance positive damping, as follows: The output voltage of the grid-type static synchronous compensator is used as the input signal, which is then processed by the virtual admittance controller. H Y ( s The current loop is then superimposed on the output impedance, which is equivalent to connecting an RLC series resonant circuit in parallel on its output impedance side from a circuit perspective. This reduces the amplitude of the output impedance of the grid-type static synchronous compensator and enhances the dominance of impedance.

[0017] Secondly, this application provides a composite oscillation suppression system for wind power systems based on a static synchronous compensator, comprising: The sequence impedance module is used to construct the impedance model of the grid-type static synchronous compensator and the equivalent wind turbine based on the wind power transmission system including the grid-type static synchronous compensator, and to construct the sequence impedance model of the wind power transmission system by combining the impedance models of the grid-type static synchronous compensator and the equivalent wind turbine. The oscillation factor module is used to apply the sequence impedance model in conjunction with the impedance contribution. β The interaction between the grid-type static synchronous compensator and the equivalent wind turbine was analyzed, and the dominant factors for the oscillation risk of the wind power transmission system in the subsynchronous / supersynchronous frequency band were determined based on the interaction. The oscillation suppression module is designed to address the dominant factors contributing to oscillation risk in the subsynchronous frequency band. It employs a parameter sensitivity-based control parameter optimization strategy by altering the control parameters of the grid-type static synchronous compensator: increasing the virtual resistance and decreasing the reactive power loop integral coefficient, thereby reducing the negative damping range of the subsynchronous frequency band and ultimately suppressing oscillations in the subsynchronous frequency band. Based on the dominant factors of oscillation risk in the supersynchronous frequency band, a voltage-feedforward-based virtual admittance control strategy is adopted to reduce the impedance amplitude of the grid-type static synchronous compensator output, enhance its positive damping dominance, eliminate the negative damping of the converter-side equivalent impedance in the supersynchronous frequency band, and thus suppress oscillation in the supersynchronous frequency band.

[0018] Thirdly, this application provides an electronic device, comprising: Memory, used to store computer programs; A processor is used to implement the steps of the composite oscillation suppression strategy for wind power systems based on static synchronous compensators when executing the computer program.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: This application provides a composite oscillation suppression strategy for wind power systems based on static synchronous compensators (SGMCs). It constructs a sequence impedance model of the grid-type SGMC (GFM-STATCOM) and the equivalent wind turbine (EWTG) using a multi-harmonic linearization method. The modeling process fully considers frequency coupling effects, accurately characterizing the system's electrical characteristics and providing reliable model support for subsequent oscillation analysis. This solves the analytical bias problem caused by neglecting harmonic interactions in traditional modeling. Secondly, it introduces impedance contribution. β Quantifying the interaction of equipment can clearly identify the dominant factors of oscillation risk in the subsynchronous / supersynchronous frequency bands, avoiding ambiguous judgments about oscillation causes and making the design of suppression strategies more targeted. Finally, a frequency band suppression strategy is adopted. For the problem of negative damping dominance of GFM-STATCOM in the subsynchronous frequency band, the negative damping range can be reduced without additional hardware by increasing the virtual resistance and decreasing the reactive power loop integral coefficient through parameter sensitivity optimization. For the problem of negative damping dominance of equivalent wind turbine units in the supersynchronous frequency band, the output impedance amplitude of GFM-STATCOM is reduced by using voltage feedforward virtual admittance control, enhancing its positive damping dominance and effectively eliminating negative damping in this frequency band. This achieves precise suppression of composite oscillations and significantly improves the stability of wind power systems under weak grid conditions.

[0020] This application also proposes a wind power system composite oscillation suppression system based on a static synchronous compensator, an electronic device, and a computer storage medium, which possess all the advantages of the aforementioned wind power system composite oscillation suppression strategy based on a static synchronous compensator. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the composite oscillation suppression strategy for wind power systems based on static synchronous compensators according to the present invention; Figure 2 This is a schematic diagram of the wind power system synchronous oscillation suppression system structure of the static synchronous compensator of the present invention; Figure 3 This is a block diagram of the main circuit and control system of the network-type STATCOM of the present invention; Figure 4 This is a block diagram of the main circuit and control system of the equivalent wind turbine of the present invention; Figure 5 This is a graph showing the impedance contribution and negative damping analysis of the present invention. Figure 6 This is a sensitivity diagram of the control parameters of the present invention; Figure 7 The impedance reshaping effect diagram is shown for the subsynchronous oscillation suppression strategy (parameter optimization) of this invention; Figure 8 The supersynchronous oscillation suppression strategy (virtual admittance) of this invention is different k Y Impedance reshaping effect diagram under different values; Figure 9 The figures show the system stability analysis under three operating conditions without the application of the composite oscillation suppression strategy of this invention. Figure 10 The figure shows the system stability analysis under three operating conditions when the composite oscillation suppression strategy of this invention is applied. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] A composite oscillation suppression strategy for wind power systems based on static synchronous compensators includes the following steps: Step 1: Based on the wind power transmission system including the grid-type static synchronous compensator, construct the impedance model of the grid-type static synchronous compensator and the equivalent wind turbine, and combine the impedance models of the grid-type static synchronous compensator and the equivalent wind turbine to construct the sequence impedance model of the wind power transmission system. Impedance models of GFM-STATCOM and equivalent wind turbines are established. This process requires combining the main circuit structure of the equipment (such as the cascaded H-bridge topology of GFM-STATCOM and the equivalent aggregation structure of the equivalent wind turbine) with the control system logic (such as the DC voltage self-synchronization control and reactive power-voltage droop control of GFM-STATCOM, and the AC voltage-oriented vector control of the equivalent wind turbine). Then, frequency coupling effects are considered using a multi-harmonic linearization method. The impedance models of both are then integrated into a sequence impedance model of the wind power transmission system, achieving an accurate characterization of the overall system impedance. By constructing the sequence impedance model, the complex electrical characteristics of the wind power transmission system can be presented in a clear impedance form, providing reliable model support for subsequent analysis of inter-equipment interactions and oscillation risks. Furthermore, the sequence impedance model can analyze the positive and negative sequence components separately, covering the electrical characteristics of different frequency bands of the system.

[0025] Step 2: Based on the sequence impedance model and in conjunction with the impedance contribution. β The interaction between the grid-type static synchronous compensator and the equivalent wind turbine was analyzed, and the dominant factors for the oscillation risk of the wind power transmission system in the subsynchronous / supersynchronous frequency band were determined based on the interaction. Based on the order impedance model obtained in step 1, an impedance contribution is introduced. β As an evaluation metric, a perturbation is applied to the original impedance of the GFM-STATCOM and the equivalent wind turbine, and the change in the equivalent impedance on the converter side is observed. The impedance sensitivity is then calculated to determine the appropriate impedance. β Value, based on β The values ​​are used to determine the degree of dominance of the two factors on the equivalent impedance of the system in different frequency bands, and then to analyze their interaction. It is found that in the subsynchronous frequency band, the negative damping of GFM-STATCOM is dominant, and in the supersynchronous frequency band, the negative damping of the equivalent wind turbine is dominant, thereby identifying the core causes of oscillation risk in each frequency band.

[0026] Using impedance contribution β The quantifiable impact of equipment on system impedance avoids vague judgments on the dominant factors of oscillation risk, accurately locates the key causes of sub- / supersynchronous frequency band oscillations, provides a clear direction for subsequent frequency band suppression strategies, ensures that suppression measures can directly address the core of the problem, and improves the pertinence of the strategy.

[0027] Step 3: Based on the dominant cause of negative damping risk in the subsynchronous frequency band, a control parameter optimization strategy based on parameter sensitivity is adopted. This is achieved by changing the control parameters of the grid-type static synchronous compensator: increasing the virtual resistance. R v and reduce the reactive power loop integral coefficient k iQ This reduces the negative damping range of the subsynchronous frequency band, thereby suppressing oscillations in the subsynchronous frequency band. Based on the dominant cause of negative damping risk in the supersynchronous frequency band, a virtual admittance control strategy based on voltage feedforward is used to enhance positive damping, as follows: The output voltage of the grid-type static synchronizing compensator is used as the input signal and superimposed onto the current loop after passing through a virtual admittance controller. From a circuit perspective, this is equivalent to connecting an RLC series resonant circuit in parallel on the output impedance side of the grid-type static synchronizing compensator. This reduces the impedance amplitude of the grid-type static synchronizing compensator output, making the positive damping of the grid-type static synchronizing compensator on the equivalent impedance of the converter side in the supersynchronous frequency band go from non-dominant to dominant. This completely eliminates the negative damping of the equivalent impedance of the converter side in the supersynchronous frequency band, thereby suppressing oscillations in the supersynchronous frequency band.

[0028] To address the dominant factors contributing to oscillation risk in the subsynchronous frequency band, a control parameter optimization strategy based on parameter sensitivity is adopted. By analyzing the impact of each control parameter on impedance amplitude and phase, it is determined that increasing the virtual resistance can improve the positive damping characteristics of the impedance, and decreasing the reactive power loop integral coefficient can weaken the negative damping effect, thereby narrowing the negative damping range in the subsynchronous frequency band. To address the dominant factors contributing to oscillation risk in the supersynchronous frequency band, a voltage-feedforward virtual admittance control strategy is adopted. The output voltage of the GFM-STATCOM is processed by the virtual admittance controller and superimposed on the current loop, which is equivalent to connecting an RLC series resonant circuit in parallel on the output impedance side, reducing the impedance amplitude, so that the positive damping of the GFM-STATCOM dominates in the supersynchronous frequency band, and eliminating negative damping.

[0029] The frequency band design suppression strategy avoids the problem of uneven suppression effect of a single strategy on oscillations in different frequency bands. The subsynchronous frequency band is suppressed by optimizing existing control parameters without the need for additional hardware, thus reducing costs. The supersynchronous frequency band enhances the positive damping dominance through virtual admittance control, effectively eliminating the negative damping in this frequency band. The two strategies work together to achieve comprehensive and precise suppression of the subsynchronous / supersynchronous composite oscillations of the system, significantly improving the stability of the wind power transmission system under weak grid conditions.

[0030] In some embodiments, the method for constructing the sequence impedance model of a wind power transmission system is as follows: Based on the multi-harmonic linearization method, the main circuit small-signal model and control system small-signal model of GFM-STATCOM and equivalent wind turbine are derived respectively, and the frequency coupling effect is considered in the modeling process. Based on the small-signal model of the main circuit and the small-signal model of the control system, the multiple-input multiple-output (MIMO) impedance models of the AC side of GFM-STATCOM and EWTG are determined respectively. The MIMO impedance models of GFM-STATCOM and EWTG are converted into equivalent positive-sequence and negative-sequence single-input single-output (SISO) impedance models of wind power transmission systems.

[0031] For the two core devices, GFM-STATCOM and Equivalent Wind Turbine Generator (EWTG), the small-signal models of the main circuit and the control system are derived using the multiharmonic linearization method. This is because in actual system operation, the equipment generates harmonics of different frequencies. The multiharmonic linearization method can accurately capture the interaction between different harmonic components, and the frequency coupling effect must be considered during modeling—after all, the frequency components are not isolated during equipment operation. For example, the harmonics generated by the arm switching action of GFM-STATCOM may interact with the regulation frequency of the control system. Ignoring this effect will cause the model to deviate significantly from the actual situation.

[0032] With the small-signal models of the main circuit and the control system, the MIMO impedance models on the AC side of both can be further determined. The main circuit small-signal model reflects the changes in electrical quantities such as voltage and current in the electrical structure of the equipment (like the cascaded H-bridge submodule of GFM-STATCOM and the equivalent aggregation circuit of EWTG). The control system small-signal model reflects the regulation law of electrical quantities by the control strategy (such as reactive power-voltage droop control of GFM-STATCOM and AC voltage-oriented vector control of EWTG). Only by combining these two models can the relationship between multiple input quantities (such as control signals and grid voltage disturbances) and multiple output quantities (such as output current and impedance characteristics) on the AC side of the equipment be fully presented. This is the origin of the MIMO impedance model.

[0033] Finally, the MIMO impedance model is transformed into equivalent positive-sequence and negative-sequence SISO impedance models. In power system analysis, the positive-sequence component corresponds to the electrical characteristics of normal operation, while the negative-sequence component is related to system asymmetric faults and equipment asymmetric operation. Decomposing the complex MIMO model into positive-sequence and negative-sequence SISO models better aligns with the traditional stability analysis approach for power systems, facilitating subsequent analysis of system oscillation risks for different frequency bands corresponding to different sequence components.

[0034] By using a multi-harmonic linearization method and considering frequency coupling effects, the derived small-signal models of the main circuit and control system can accurately reproduce the electrical characteristics and control response of GFM-STATCOM and EWTG in actual operation, avoiding model distortion caused by ignoring harmonic interaction and frequency coupling.

[0035] The MIMO impedance model fully covers the multivariate correlations on the AC side of the equipment, while the transformed positive-sequence and negative-sequence SISO impedance models simplify the complex multivariate analysis process and conform to the sequence component analysis logic familiar to power system engineers. When analyzing the oscillation risk of the system in different frequency bands (such as subsynchronous and supersynchronous frequency bands), it is possible to more intuitively focus on the impedance characteristics corresponding to the positive-sequence or negative-sequence components, thus reducing the difficulty of analysis.

[0036] This method models GFM-STATCOM and EWTG separately, and then integrates them into a system-level sequence impedance model. This model reflects both the impedance characteristics of individual devices and their interaction within the system. When analyzing the coupling relationship between devices and determining the dominant factors of oscillation risk based on this sequence impedance model, it can cover the overall electrical characteristics of the system.

[0037] In some embodiments, based on the sequence impedance model and in combination with impedance contribution... β This study analyzes the interaction between grid-type static synchronizing compensators and equivalent wind turbine units, and identifies the dominant factors contributing to the oscillation risk of wind power transmission systems in the subsynchronous / supersynchronous frequency bands based on this interaction. These factors include: A certain amount of perturbation is applied to the original impedances of EWTG and GFM-STATCOM, based on the equivalent impedance on the converter side. Z eq-GFM The changes were used to obtain the impedance sensitivity of the EWTG and GFM-STATCOM outputs. δ, Then determine the corresponding impedance contribution. β ; Based on impedance contribution β Determine the equivalent impedance of the converter side for the negative damping of EWTG and GFM-STATCOM at different frequency bands. Z eq-GFM Dominant position; Negative damping, which dominates at different frequency bands, is considered the primary factor in oscillation risk.

[0038] Optionally, the negative damping I of the subsynchronous frequency band is mainly dominated by the negative damping of GFM-STATCOM, that is, the dominant factor of the oscillation risk of the subsynchronous frequency band is the negative damping of GFM-STATCOM; The negative damping II in the supersynchronous band has a limited positive damping effect on improving the negative damping of EWTG because the dominance range of GFM-STATCOM in this band is limited. In other words, the dominant factor of oscillation risk in the supersynchronous band is the negative damping of EWTG.

[0039] To determine the dominant factors contributing to the oscillation risk in the subsynchronous / supersynchronous frequency bands of wind power transmission systems, the key is to first understand the actual impact of two critical devices—the grid-type static synchronizing compensator (GFM-STATCOM) and the equivalent wind turbine generator (EWTG)—on the overall impedance characteristics of the system. In practice, a controllable, certain amount of disturbance is first applied to the original impedances of both the EWTG and the GFM-STATCOM—essentially "gently pushing" the impedance characteristics of the devices—and then the equivalent impedance on the converter side is closely observed. Z eq-GFM The changes were observed. Using this "perturbation-response" method, the impedance sensitivities of EWTG and GFM-STATCOM were calculated. δ ,this δ It can intuitively reflect the degree of impact of changes in the impedance of a single device on the equivalent impedance of the system. Furthermore, based on... δ Further derive the impedance contribution β , β In essence, it is a quantitative indicator of the degree of this influence, which can clearly distinguish which device has more "say" in the system impedance characteristics.

[0040] With impedance contribution β The next step is to analyze the situation at different frequency bands using the sequence impedance model. This is because the dominance of equipment over system impedance varies across different frequency ranges (such as subsynchronous and supersynchronous bands). Through comparison... β The magnitude of the value can determine whether the negative damping of the EWTG or the GFM-STATCOM plays a dominant role in a certain frequency band. For example, in the subsynchronous band, the GFM-STATCOM's... β A higher value means that its negative damping has a greater impact on the system's equivalent impedance, Zeq-GFM. Therefore, the dominant factor in oscillation risk at this frequency band is the negative damping of GFM-STATCOM. However, at the supersynchronous frequency band, the negative damping of GFM-STATCOM... β As the value decreases and the dominant range shrinks, its positive damping cannot effectively offset the negative damping of the EWTG. At this point, the negative damping of the EWTG becomes the key factor affecting the system impedance, and naturally, the dominant factor in the risk of supersynchronous frequency band oscillations. The whole process is like "identifying the responsible party," through... β This "quantitative benchmark" accurately identifies the core sources of oscillation risks in different frequency bands.

[0041] The biggest advantage of this method is that it eliminates the past situation of "vague judgment" on the dominant factors of oscillation risk. Previously, one might only know that the system has oscillation risk, but it wouldn't be clear whether it was a problem with GFM-STATCOM or EWTG. However, by using impedance contribution... β The quantitative analysis can clearly distinguish the "risk sources" of the subsynchronous and supersynchronous frequency bands respectively - the subsynchronous frequency band is locked to the negative damping of GFM-STATCOM, and the supersynchronous frequency band is locked to the negative damping of EWTG, so that there are clear "targets" when formulating suppression strategies, and no more futile efforts will be made.

[0042] Having identified the dominant factors contributing to oscillation risks in different frequency bands, strategies were designed for the subsynchronous band focusing on optimizing the parameters of the GFM-STATCOM and improving its negative damping. For the supersynchronous band, the focus was on enhancing the GFM-STATCOM's ability to suppress the negative damping of the EWTG. This precise matching approach significantly improves the effectiveness of the suppression strategy while avoiding unnecessary hardware modifications or parameter adjustments, reducing engineering costs and implementation difficulty, and better meeting the operational needs of actual wind power systems.

[0043] In some embodiments, based on the dominant cause of negative damping risk in the subsynchronous frequency band, a control parameter optimization strategy based on parameter sensitivity is adopted, which involves changing the control parameters of the grid-type static synchronizing compensator by increasing the virtual resistance. R v and reduce the reactive power loop integral coefficient k iQ This optimizes the negative damping characteristics of the subsynchronous frequency band, including: Based on the dominant factors of subsynchronous frequency band oscillation, a control parameter optimization strategy based on parameter sensitivity is adopted to improve negative damping. The optimization scheme for negative damping frequency band I is to improve the negative damping of GFM-STATCOM within this band.

[0044] First, based on amplitude sensitivity S M and phase angle sensitivity S A The conceptual assessment evaluates the impact of each controller parameter on impedance amplitude and phase. Considering that the negative damping frequency band I involves a fundamental frequency of 50Hz, to avoid the influence of additional controllers on basic control, the impedance reshaping approach is to improve the negative damping frequency band I by adjusting the control parameters. The control parameter optimization strategy based on parameter sensitivity is to increase the virtual resistance. R v and reduce the reactive power loop integral coefficient k iQ The subsynchronous negative damping characteristics of GFM-STATCOM have been improved.

[0045] In some embodiments, based on the dominant cause of negative damping risk in the supersynchronous frequency band, a voltage feedforward-based virtual admittance control strategy is used to enhance positive damping, as follows: Based on the dominant factors of supersynchronous frequency band oscillation, a voltage-feedforward-based virtual admittance control strategy is adopted to enhance positive damping. The optimization scheme for negative damping frequency band II aims to increase the dominance range of the GFM-STATCOM within this band. This is achieved using a voltage-feedforward-based virtual admittance control strategy, implemented in the control system by taking the output voltage of the GFM-STATCOM as the input signal, which is then processed by the virtual admittance controller. H Y ( s The impedance is then superimposed onto the current loop, which, from a circuit perspective, is equivalent to connecting an RLC series resonant circuit in parallel on its output impedance side, thereby reducing the amplitude of the GFM-STATCOM output impedance and enhancing the dominance of impedance.

[0046] Example 1 See Figure 1 A composite oscillation suppression strategy for wind power systems based on static synchronous compensators includes the following five steps: Step 1: Establish the sequence impedance model of the wind power transmission system containing the grid-type static synchronous compensator.

[0047] S1.1. The small-signal model of the main circuit of GFM-STATCOM and EWTG is established by using the multi-harmonic linearization method.

[0048] The research object takes a wind power transmission system containing GFM-STATCOM as an example, and its schematic diagram is as follows: Figure 2 As shown, the wind turbines in the wind farm are connected to the 35kV medium-voltage collection line via a 0.69kV / 35kV step-up transformer T1. A grid-type CHB-STATCOM is connected to the 35kV Point of Common Coupling (PCC) of the power station, and then stepped up by the 35kV / 220kV main transformer T2 before being connected to the power grid via the 220kV high-voltage transmission line.

[0049] CHB-STATCOM main circuit topology is as follows: Figure 3 As shown in (a), each phase arm consists of... N It consists of cascaded full-bridge sub-modules. v sx, i sx (x=a,b,c) represents the three-phase voltage and current. L n and R n These are the equivalent inductance and equivalent resistance of the bridge arm, respectively. C mFor submodule capacitors, v cx This represents the capacitor voltage of the submodule. Its average value model is as follows: Figure 3 As shown in (b), m x For modulated waves, C eq = C m / N This is the equivalent capacitance. v cm The voltage across phase a capacitor is given. The control block diagram of the GFM-STATCOM in constant reactive power control mode is shown below. Figure 3 As shown in (c), it includes a DC voltage self-synchronization control loop, a reactive power-voltage droop control loop, a virtual impedance loop, a fundamental frequency current loop, and a phase-to-phase voltage equalization loop.

[0050] Because this patent focuses on the small-signal stability problem of impedance interaction between wind farms, STATCOM, and weak power grids, it adopts the following for wind farms. Figure 4 The single-machine equivalent aggregation model shown in (a) is simplified by treating the wind turbine, permanent magnet synchronous generator, and machine-side converter as a single controlled current source. The control structure is as follows: Figure 4 As shown in (b), AC voltage-oriented vector control technology is adopted, and the control objective is to maintain the DC bus voltage constant and adjust the output reactive power.

[0051] Figure 3 (a) and Figure 4 (a) The corresponding small-signal models of the main circuits of GFM-STATCOM and EWTG are as follows:

[0052]

[0053] Wherein, the superscript ^ represents the small-signal perturbation component. M a , V cm , I a These are the Toeplitz matrices for the modulated wave, capacitor voltage, and steady-state components of the alternating current, respectively. Y L and Z C These are the equivalent admittance matrix of the bridge arm and the equivalent capacitance-impedance matrix of the submodule, respectively. In the EWTG expression... K m is the PWM gain coefficient, and the meanings of other parameters are the same as those of the small-signal model elements of the GFM-STATCOM main circuit.

[0054] S1.2. The small-signal model of the control system of GFM-STATCOM and EWTG is established by using the multi-harmonic linearization method.

[0055] Figure 3 (c) and Figure 4 (b) The corresponding small-signal control system models for GFM-STATCOM and EWTG are as follows:

[0056]

[0057] in, E v , E qv / i , E i , E vi , E b These are the 7×7 gain coefficient matrices for the DC voltage self-synchronization control loop, reactive power-voltage droop control loop, fundamental frequency current loop, virtual impedance loop, and phase-to-phase voltage equalization loop of GFM-STATCOM, respectively. G v , G qv / i , G i , G pll These are the 7x7 gain coefficient matrices for the DC voltage loop, reactive power loop, fundamental frequency current loop, and phase-locked loop of the EWTG, respectively.

[0058] S1.3. By combining the small-signal model of the main circuit and the small-signal model of the control system, the AC-side MIMO impedance models of GFM-STATCOM and EWTG are obtained.

[0059] Substituting the small-signal model of the control system into the small-signal model of the main circuit, the AC side admittance models of GFM-STATCOM and WTG can be obtained respectively.

[0060]

[0061] in, U It is a 7x7 identity matrix. Y EWTG The equivalent impedance of the transformer, the turns ratio, and the impedance of the collection line also need to be considered.

[0062] In the modeling process, harmonic components are considered up to the third order. The admittance model after considering frequency coupling effects is a MIMO model, and the extracted frequency is... f p andf p -2 f The small-signal response corresponding to 1, its AC-side second-order impedance model can be expressed as:

[0063] Where p represents positive order and n represents negative order. (4,4) represents the element in the fourth row and fourth column of the matrix, and the other symbols have the same meaning.

[0064] To analyze the system's stability from the perspective of impedance mechanism, the MIMO impedance model can be transformed into equivalent positive-sequence and negative-sequence equivalent SISO impedances, which can be expressed as follows:

[0065] in, Y gp and Y gn These are the positive and negative net-side admittances, respectively.

[0066] Since the research approach for positive and negative sequence impedances is consistent, for ease of analysis, the subsequent stability analysis will be based on positive sequence impedance.

[0067] Step 2: Based on the system impedance model, analyze and reveal the different causes and underlying mechanisms of the risk of subsynchronous oscillation and supersynchronous oscillation in the system.

[0068] S2.1, Define the impedance contribution. β Used to analyze the impact of GFM-STATCOM and EWTG on the equivalent impedance of the converter side.

[0069] The equivalent impedance on the converter side is determined by both the EWTG and GFM-STATCOM impedance characteristics. To evaluate the equivalent impedance on the converter side of the object... Z eq-GFM The effect of applying a 10% perturbation to the original impedances of EWTG and GFM-STATCOM was observed, and the equivalent impedance on the converter side was then measured. Z eq-GFM Corresponding changes. Define the output impedance sensitivity of EWTG and STATCOM. δ and contribution to equivalent impedance β They are shown below:

[0070]

[0071] in, δ The impedance sensitivity after applying a 10% perturbation to the corresponding device impedance. Based on... β The degree of influence of the converter on the equivalent impedance is defined as follows: βFrequency bands below 50% are considered non-dominant, while those above 50% are considered dominant.

[0072] S2.2, Based on impedance contribution β This study reveals the interaction between GFM-STATCOM and EWTG and the mechanism by which they affect the equivalent impedance on the converter side.

[0073] The impedance diagram after GFM-STATCOM is connected to the wind farm is as follows: Figure 5 As shown in (a), the contributions of GFM-STATCOM and EWTG are as follows: Figure 5 As shown in (c), the negative damping and contribution results of the impedance are plotted on... Figure 5 (b) provides an intuitive comparison.

[0074] Depend on Figure 5 (a) It can be seen that the equivalent wind farm side impedance after GFM-STATCOM is connected is Z eq-GFM The negative damping characteristic range was reduced from 1-41Hz and 48-729Hz to negative damping band I: 36-50Hz and negative damping band II: 76-94Hz, which is a significant improvement.

[0075] GFM-STATCOM Z eq-GFM The mechanism of influence is analyzed as follows: Except for some subsynchronous and super-frequency bands, the impedance amplitude of GFM-STATCOM is smaller than that of EWTG, meaning that GFM-STATCOM has a larger dominant range. Within the dominant frequency bands of GFM-STATCOM (1-50Hz, 51Hz-83Hz, 94-548Hz, and 856-925Hz), the influence is due to the positive damping characteristics of GFM-STATCOM (1-36Hz and 50-1000Hz). Z eq-GFM The negative damping characteristics caused by EWTG in the impedance characteristics are improved.

[0076] The reason why the station's impedance characteristics have a negative damping frequency band I: 36-50Hz is as follows: Z eq-GFM The impedance characteristics are dominated by GFM-STATCOM inductive negative damping in the 36-48Hz and capacitive negative damping in the 48-50Hz range, respectively.

[0077] Z eq-GFMThe reason for the presence of a negative damping frequency band II (76-94Hz) in the impedance characteristics is as follows: Although the GFM-STATCOM impedance exhibits positive damping characteristics within the 76-94Hz range, its influence on the station impedance is dominant only in the 76-83Hz range. Furthermore, in this frequency band, the optimization effect of its inductive positive damping on the inductive negative damping of the EWTG is not as significant as that of capacitive positive damping. Therefore, the inductive negative damping characteristics of the station are improved but not completely eliminated within the 76-83Hz range. Z eq-GFM The impedance characteristics are dominated by EWTG capacitive negative damping in the 83-94Hz range.

[0078] Step 3: Based on the dominant factors of subsynchronous frequency band oscillation, adopt a control parameter optimization strategy based on parameter sensitivity to improve negative damping.

[0079] S3.1 Based on the mechanism of negative damping in the subsynchronous frequency band of the system, an oscillation suppression strategy for the subsynchronous frequency band is proposed.

[0080] Based on the mechanism analysis in step 2, the equivalent wind farm-side impedance after GFM-STATCOM integration still exhibits negative damping frequency bands I (36-50Hz) and II (76-94Hz), indicating that the system faces subsynchronous and supersynchronous oscillation risks, respectively. Further mechanism analysis reveals that the causes of negative damping in the two frequency bands differ: negative damping frequency band I is primarily dominated by the negative damping of GFM-STATCOM. Therefore, the optimization strategy for negative damping frequency band I aims to improve the negative damping of GFM-STATCOM within this frequency band.

[0081] Considering that the negative damping frequency band I involves the fundamental frequency of 50Hz, to avoid the impact of the additional controller on the basic control, the impedance reshaping approach of the GFM-STATCOM in this embodiment is as follows: The negative damping frequency band I is improved by adjusting the control parameters. It is worth noting that the negative damping of the grid-type converter near the fundamental frequency band is an inherent characteristic of its voltage source external characteristics, especially the negative damping frequency band near 50Hz, which is difficult to completely eliminate. Therefore, the main objective in adjusting the control parameters is to improve the inductive negative damping frequency band of 36-48Hz, while minimizing the deterioration of the negative damping at 50Hz.

[0082] S3.2 Define parameter sensitivity to evaluate the degree of influence of each controller parameter on impedance amplitude and phase.

[0083] Defined amplitude sensitivity S M and phase angle sensitivity S A The expression is as follows

[0084]

[0085] in α k For parameters k The original value is taken as the parameter change amount of 10%, i.e., △ α k =0.1 α k M and A are parameters respectively. k Impedance amplitude and phase at the corresponding values.

[0086] S3.3 Determine the control parameter optimization strategy based on parameter sensitivity.

[0087] Drawing sensitivity Figure 6 At that time, the absolute values ​​of the parameter sensitivity for each parameter in the wide frequency domain are used, and the positive and negative signs of the sensitivity are represented by solid and dashed lines. In the negative damping frequency band I, only the reactive power loop integral coefficient has relatively high parameter sensitivity and its amplitude and phase angle sensitivity are consistent in sign. k iQ and virtual resistance R v Other parameter sensitivities are not plotted. Observe. Figure 6 It can be seen that the reactive power loop integral coefficient within the negative damping frequency band I is... k iQ and virtual resistance R v The amplitudes of both parameters are consistent with the sign of the phase angle sensitivity, where... k iQ Sensitivity is positive. R v The sensitivity is negative, therefore by reducing k iQ or increase R v It can improve inductive negative damping and reduce the amplitude of the STATCOM network, ensuring its dominance.

[0088] Adjust the parameters according to the above rules. k iQ It is 0.6 times the original parameter. R v The impedance after doubling the original parameters is as follows: Figure 7 As shown, the inductive negative damping in the negative damping frequency band I is completely eliminated, and the negative damping frequency band I is reduced from 36-50Hz to 49-50Hz, which greatly reduces the risk of subsynchronous oscillation of the system.

[0089] Step 4: Based on the dominant factors of supersynchronous frequency band oscillation, adopt a voltage feedforward-based virtual admittance control strategy to enhance positive damping.

[0090] S4.1 Based on the mechanism of negative damping in the supersynchronous frequency band, an oscillation suppression strategy for the supersynchronous frequency band is proposed.

[0091] Based on the mechanism analysis in step 2, the reason for the existence of the supersynchronous negative damping frequency band II is that the dominance range of GFM-STATCOM in this frequency band is limited, and the positive damping of GFM-STATCOM has a limited effect on improving the negative damping of EWTG. Therefore, the optimization scheme for negative damping frequency band II is to increase the dominance range of GFM-STATCOM in this frequency band.

[0092] From a circuit perspective, reducing the amplitude of the GFM-STATCOM output impedance can be achieved by connecting an RLC series resonant circuit in parallel on its output impedance side. Furthermore, through design, the inductive and capacitive negative damping of the equivalent impedance can be optimized using the capacitive and inductive reactance components of this circuit. Based on the above principles, this embodiment employs a voltage-feedforward-based virtual admittance control strategy. This strategy is implemented in the control system by using the GFM-STATCOM output voltage as the input signal, which is then processed by the virtual admittance controller. H Y ( s Then superimposed onto the current loop, specifically as follows: Figure 3 (c) As shown in the red dashed box. The virtual admittance controller is selected as a second-order bandpass filter, which can simulate the admittance of the RLC series resonant circuit and reduce the impact of virtual admittance control on the impedance characteristics of other frequency bands. The expression is as follows:

[0093] in, k Y For virtual admittance coefficients, ω c =2π f C The center angular frequency, Q = f C / BW is the quality factor. (Settings are incomplete and require further context.) k Y To improve the dominance of GFM-STATCOM in negative damping band II, set... f C The bandwidth BW ensures that its effective range covers the negative damping frequency band II. Therefore f C The amplitude influence range under sequential coordinates is set to 83Hz (33Hz under dq coordinates), and BW is set to 22Hz according to the range of covering negative damping II.

[0094] S4.2 Observe the virtual admittance coefficient k Y The effect on oscillation suppression is investigated, and its value is determined.

[0095] With the above parameters fixed, observe k Y The effect on impedance characteristics, such as Figure 8 As shown in (a). With k Y Starting from zero, the virtual admittance is increased in equivalent parallel circuits. Y Gradually reshape the output impedance characteristics of the GFM-STATCOM, when k Y When =0.4, Z GFM-STATCOM The amplitude gradually decreases in the 75~91Hz range. Z EWTG This means that the influence of GFM-STATCOM on the equivalent impedance of the converter side has transitioned to a dominant position. Simultaneously, the positive damping introduced by the equivalent virtual admittance in the phase aspect enhances the inductive positive damping of GFM-STATCOM in the 75-83Hz and capacitive positive damping in the 83-91Hz range. Figure 8 (b) is manifested as k Y Equivalent impedance at =0.4 Z eq-GFM The negative damping was completely eliminated, and a purely resistive resonant peak with the largest amplitude was formed at the center frequency of 83Hz. When k Y Increasing the value by 0.5 from 0.4 results in a continuous injection of additional positive damping, leading to a corresponding decrease in the amplitude of the resonance peak, but a further improvement in the phase margin. It is worth noting that... k Y It's not necessarily true that the larger the better. Since this strategy is implemented in a synchronously rotating (dq) coordinate system, the center frequency... f C The virtual admittance at 83Hz (i.e., 50+33Hz) will produce an equivalent admittance in the low-frequency range of 50-33Hz (i.e., 17Hz) due to the mirror effect of spectral shift. k Y The increase in frequency reduces the phase margin in the low-frequency band.

[0096] Therefore, taking into account the range of negative damping frequency band II, sufficient stability margin, and potential impact on the low-frequency band, the final selection was made. k Y =0.5 achieves the elimination of negative damping frequency band II.

[0097] Step 5: Verify the composite oscillation suppression strategy based on impedance reshaping of the grid-type static synchronous compensator to suppress the risk of subsynchronous / supersynchronous oscillation in the wind power transmission system.

[0098] S5.1 Study the oscillation risk of the system before applying the composite oscillation suppression strategy.

[0099] By varying the length of 220kV transmission lines to simulate power grids with different short-circuit ratios (SCR), and based on impedance stability criteria, analysis was conducted under three operating conditions (Condition 1: Line = 100km, SCR = 3.7; Condition 2: Line = 200km, SCR = 2.9; Condition 3: Line = 350km, SCR = 2.3). Figure 9 The network-side impedance shown Z g and equivalent wind farm side impedance Z eq-GFM The amplitude-phase curves are obtained, and the stability of the system is analyzed. From the amplitude-phase curves, it can be seen that when SCR = 3.7, Z g and Z eq-GFM There is an intersection point with a phase margin greater than 0° at 167 Hz and 180 Hz, indicating stable system operation. As the transmission line length increases, the SCR further decreases to 2.9 and 2.3. Z g and Z eq-GFM The presence of intersections with phase margins of -29.9° and -25.3° at 82Hz and 42Hz respectively indicates that the system will experience supersynchronous oscillation at 82Hz and subsynchronous oscillation at 42Hz under operating conditions 2 and 3 respectively.

[0100] S5.2 Verify the effect of applying the composite oscillation suppression strategy on improving system stability.

[0101] The oscillation suppression strategy proposed in this patent can achieve impedance reshaping of GFM-STATCOM, further realizing the equivalent impedance of the converter side. Z eq-GFM To optimize the negative damping frequency band and verify the effectiveness of the above strategy under different operating conditions, the stability analysis results of the wind power transmission system are as follows: Figure 10 As shown. Under operating conditions 1 to 3, the reshaped Z eq and Z eq-GFM The phase margin at all intersection points is greater than 0, and the system can operate stably, further demonstrating the effectiveness of the composite oscillation suppression strategy proposed in this patent.

[0102] This embodiment presents a composite oscillation suppression strategy for wind power systems based on static synchronous compensators (SNCs). It fully reveals the mechanism and causes of negative damping in the subsynchronous / supersynchronous frequency bands: firstly, the grid-type SNC compensator itself exhibits dominant negative damping characteristics in the subsynchronous frequency band; secondly, its positive damping is not dominant in the supersynchronous frequency band, resulting in limited suppression of negative damping by wind turbines. The proposed impedance reshaping-based composite suppression strategy can be used to accurately address the stability issues of wind power systems under weak grid conditions. It can precisely correct the subsynchronous negative damping characteristics dominated by the grid-type SNC compensator through parameter optimization, and effectively enhance its suppression capability for supersynchronous negative damping dominated by wind turbines through virtual admittance. This strategy is suitable for eliminating potential composite oscillation risks from the perspective of impedance mechanisms, contributing to improving the safe and stable operation of large-scale wind power transmission systems.

[0103] Example 2 Correspondingly, this application also provides a composite oscillation suppression system for wind power systems based on a static synchronous compensator, comprising: The sequence impedance module is used to construct the impedance model of the grid-type static synchronous compensator and the equivalent wind turbine based on the wind power transmission system including the grid-type static synchronous compensator, and to construct the sequence impedance model of the wind power transmission system by combining the impedance models of the grid-type static synchronous compensator and the equivalent wind turbine. The oscillation factor module is used to apply the sequence impedance model in conjunction with the impedance contribution. β The interaction between the grid-type static synchronous compensator and the equivalent wind turbine was analyzed, and the dominant factors for the oscillation risk of the wind power transmission system in the subsynchronous / supersynchronous frequency band were determined based on the interaction. The oscillation suppression module is designed to address the dominant factors contributing to oscillation risk in the subsynchronous frequency band. It employs a parameter sensitivity-based control parameter optimization strategy by altering the control parameters of the grid-type static synchronous compensator: increasing the virtual resistance and decreasing the reactive power loop integral coefficient, thereby reducing the negative damping range of the subsynchronous frequency band and ultimately suppressing oscillations in the subsynchronous frequency band. Based on the dominant factors of oscillation risk in the supersynchronous frequency band, a voltage-feedforward-based virtual admittance control strategy is adopted to reduce the impedance amplitude of the grid-type static synchronous compensator output, enhance its positive damping dominance, eliminate the negative damping of the converter-side equivalent impedance in the supersynchronous frequency band, and thus suppress oscillation in the supersynchronous frequency band.

[0104] Compared with the prior art, the present invention has the following beneficial technical effects: This oscillation suppression strategy first establishes a sequence impedance model for a wind power transmission system containing a grid-type static synchronizing compensator (SRC). Based on this, it clearly reveals for the first time the intrinsic mechanism of a composite oscillation—a subsynchronous oscillation dominated by the SRC itself and a supersynchronous oscillation dominated by the wind turbines—and proposes a targeted composite suppression strategy accordingly. This strategy has advantages such as thorough mechanism analysis, precise strategy design, strong targeting for different oscillation modes, and significant suppression effect. Because this invention starts from the fundamental mechanism of oscillation, it can improve the negative damping characteristics dominated by the SRC itself and the wind turbines from the impedance level through parameter optimization and virtual admittance control. This helps to fundamentally solve the potential composite oscillation risk of wind power systems under weak grid conditions, thereby significantly improving the safe and stable operation level of large-scale wind power transmission systems.

[0105] It should be noted that, in the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another device, or some features may be ignored or not executed. The modules described as separate components may or may not be physically separated. The components shown as modules may be one or more physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs.

[0106] Furthermore, in the various embodiments of the present invention, the modules can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The integrated unit described above can be implemented in hardware or as a software functional unit.

[0107] An electronic device provided in this application includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the composite oscillation suppression strategy for wind power systems based on static synchronous compensators as described in any of the above embodiments.

[0108] Another electronic device provided in this application embodiment may further include: an input port connected to a processor for transmitting multimodal data collected by an external acquisition device to the processor; a display unit connected to the processor for displaying the processor's processing results to the outside world; and a communication module connected to the processor for enabling communication between the electronic device and the outside world. The display unit may be a display panel, a laser scanning display, etc.; the communication method adopted by the communication module includes, but is not limited to, Mobile High Definition Link (HML), Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), and wireless connection (including Wi-Fi, Bluetooth, Bluetooth Low Energy, and IEEE 802.11s-based communication technology).

[0109] This application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the steps of the composite oscillation suppression strategy for wind power systems based on static synchronous compensators as described in any of the above embodiments.

[0110] For descriptions of relevant parts of the wind power system composite oscillation suppression system, electronic equipment, and computer-readable storage medium based on static synchronous compensators provided in this application's embodiments, please refer to the detailed descriptions of the corresponding parts in the wind power system composite oscillation suppression strategy based on static synchronous compensators provided in this application's embodiments; they will not be repeated here. Furthermore, parts of the technical solutions provided in this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.

[0111] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A composite oscillation suppression strategy for wind power systems based on static synchronous compensators, characterized in that, Includes the following steps: Step 1: Based on the wind power transmission system including the grid-type static synchronous compensator, construct the impedance model of the grid-type static synchronous compensator and the equivalent wind turbine, and combine the impedance models of the grid-type static synchronous compensator and the equivalent wind turbine to construct the sequence impedance model of the wind power transmission system. Step 2: Based on the sequence impedance model and in conjunction with the impedance contribution. β The interaction between the grid-type static synchronous compensator and the equivalent wind turbine was analyzed, and the dominant factors for the oscillation risk of the wind power transmission system in the subsynchronous / supersynchronous frequency band were determined based on the interaction. Step 3: Based on the dominant factors of subsynchronous frequency band oscillation risk, a control parameter optimization strategy based on parameter sensitivity is adopted. By changing the control parameters of the grid-type static synchronous compensator, the virtual resistance is increased and the reactive power loop integral coefficient is decreased, thereby reducing the negative damping range of the subsynchronous frequency band and suppressing the oscillation of the subsynchronous frequency band. Based on the dominant factors of oscillation risk in the supersynchronous frequency band, a voltage-feedforward-based virtual admittance control strategy is adopted to reduce the impedance amplitude of the grid-type static synchronous compensator output, enhance its positive damping dominance, eliminate the negative damping of the converter-side equivalent impedance in the supersynchronous frequency band, and thus suppress oscillation in the supersynchronous frequency band.

2. The composite oscillation suppression strategy for wind power systems based on static synchronous compensators according to claim 1, characterized in that, The method for constructing the sequence impedance model of the wind power transmission system is as follows: Based on the multi-harmonic linearization method, the main circuit small-signal model and control system small-signal model of the grid-type static synchronous compensator and the equivalent wind turbine are derived respectively, and the frequency coupling effect is considered in the modeling process. Based on the small-signal model of the main circuit and the small-signal model of the control system, the multi-input multi-output impedance models of the AC side of the grid-type static synchronous compensator and the equivalent wind turbine are determined respectively. The multi-input multi-output impedance model of the grid-type static synchronous compensator and the equivalent wind turbine is converted into the equivalent positive-sequence and negative-sequence single-input single-output sequence impedance model of the wind power transmission system.

3. The composite oscillation suppression strategy for wind power systems based on static synchronous compensators according to claim 1, characterized in that, The expression for the sequence impedance model is as follows: in, Y gp and Y gn These are the positive and negative net-side admittances, respectively.

4. The composite oscillation suppression strategy for wind power systems based on static synchronous compensators according to claim 1, characterized in that, The method is based on the sequence impedance model and combined with impedance contribution. β This study analyzes the interaction between grid-type static synchronizing compensators and equivalent wind turbine units, and identifies the dominant factors contributing to the oscillation risk of wind power transmission systems in the subsynchronous / supersynchronous frequency bands based on this interaction. These factors include: A certain amount of disturbance is applied to the original impedance of the equivalent wind turbine and the grid-type static synchronous compensator, and the equivalent impedance on the converter side is used as the basis for the disturbance. Z eq-GFM The change yields the impedance sensitivity of the equivalent wind turbine and the grid-type static synchronous compensator output. δ, Then determine the corresponding impedance contribution. β ; Based on impedance contribution β Determine the effect of negative damping of the equivalent wind turbine and grid-type static synchronous compensator on the equivalent impedance of the converter side in different frequency bands. Z eq-GFM Dominant position; Negative damping, which dominates at different frequency bands, is considered the primary factor in oscillation risk.

5. A composite oscillation suppression strategy for wind power systems based on a static synchronous compensator according to claim 4, characterized in that, The dominant factor contributing to the risk of subsynchronous frequency band oscillation is the negative damping of the grid-type static synchronous compensator.

6. The composite oscillation suppression strategy for wind power systems based on static synchronous compensators according to claim 5, characterized in that, The dominant factor contributing to the risk of supersynchronous frequency band oscillation is the negative damping of the equivalent wind turbine.

7. The composite oscillation suppression strategy for wind power systems based on static synchronous compensators according to claim 4, characterized in that, The impedance sensitivity of the equivalent wind turbine and the grid-type static synchronous compensator output δ, Then determine the corresponding impedance contribution. β ,as follows: in, Z EWTG This is the equivalent impedance of the wind turbine. Z GFM-STATCOM The impedance of the grid-type static synchronous compensator. Z eq The equivalent impedance on the converter side. δ This corresponds to the impedance sensitivity. β This represents the corresponding impedance contribution.

8. The composite oscillation suppression strategy for wind power systems based on static synchronous compensators according to claim 1, characterized in that, Based on the dominant cause of negative damping in the supersynchronous frequency band, a virtual admittance control strategy based on voltage feedforward is adopted to enhance positive damping, as follows: The output voltage of the grid-type static synchronous compensator is used as the input signal, which is then processed by the virtual admittance controller. H Y ( s The current loop is then superimposed on the output impedance, which is equivalent to connecting an RLC series resonant circuit in parallel on its output impedance side from a circuit perspective. This reduces the amplitude of the output impedance of the grid-type static synchronous compensator and enhances the dominance of impedance.

9. A composite oscillation suppression system for wind power systems based on a static synchronous compensator, characterized in that, include: The sequence impedance module is used to construct the impedance model of the grid-type static synchronous compensator and the equivalent wind turbine based on the wind power transmission system including the grid-type static synchronous compensator, and to construct the sequence impedance model of the wind power transmission system by combining the impedance models of the grid-type static synchronous compensator and the equivalent wind turbine. The oscillation factor module is used to apply the sequence impedance model in conjunction with the impedance contribution. β The interaction between the grid-type static synchronous compensator and the equivalent wind turbine was analyzed, and the dominant factors for the oscillation risk of the wind power transmission system in the subsynchronous / supersynchronous frequency band were determined based on the interaction. The oscillation suppression module is designed to address the dominant factors contributing to oscillation risk in the subsynchronous frequency band. It employs a parameter sensitivity-based control parameter optimization strategy by altering the control parameters of the grid-type static synchronous compensator: increasing the virtual resistance and decreasing the reactive power loop integral coefficient, thereby reducing the negative damping range of the subsynchronous frequency band and ultimately suppressing oscillations in the subsynchronous frequency band. Based on the dominant factors of oscillation risk in the supersynchronous frequency band, a voltage-feedforward-based virtual admittance control strategy is adopted to reduce the impedance amplitude of the grid-type static synchronous compensator output, enhance its positive damping dominance, eliminate the negative damping of the converter-side equivalent impedance in the supersynchronous frequency band, and thus suppress oscillation in the supersynchronous frequency band.

10. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the composite oscillation suppression strategy for wind power systems based on a static synchronous compensator as described in any one of claims 1-8 when executing the computer program.

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