A method and related device for subsynchronous oscillation suppression of a wind farm dc system

Abstract

This application discloses a method and related equipment for suppressing subsynchronous oscillations in a wind farm connected to a DC system. The method includes: scanning the subsynchronous oscillation frequency of the raw instantaneous data at the wind farm's grid connection point to obtain the dominant oscillation characteristic quantity; if the current operating condition meets the conditions for implementing the suppression strategy based on the system operating state and the dominant oscillation characteristic quantity, then performing a modulation feasibility analysis on the current operating condition based on the system operating state to obtain boundary constraints; generating an original modulation quantity based on the dominant oscillation characteristic quantity, boundary constraints, and electrical feedback signals; performing amplitude limiting and safety verification on the original modulation quantity to generate a subsynchronous oscillation suppression command, and sending the subsynchronous oscillation suppression command to the DC system to achieve subsynchronous oscillation suppression of the wind farm. This application can ensure that the suppression command is safe and reliable, does not exceed the limits, and can quickly and timely suppress subsynchronous oscillations, and can be widely applied in the field of wind farm grid connection control technology.

Description

Technical Field

[0001] This application relates to the field of wind farm grid connection control technology, and in particular to a method and related equipment for suppressing subsynchronous oscillations in a wind farm via a DC system. Background Technology

[0002] Currently, subsynchronous oscillation is a significant potential risk during the operation of large-scale wind farms, which could potentially damage the wind turbine drive shaft. The DC system connected to the wind farm can generate a current with opposite phase and the same amplitude after detecting the subsynchronous oscillation characteristic subfrequency current harmonic.

[0003] However, as wind farms continue to expand in scale and become more widely distributed, the operation of wind turbines of different capacities, regions, and models results in the characteristic frequency of subsynchronous oscillations no longer being singular, but exhibiting multi-frequency characteristics. This makes the previous method of DC systems only being able to detect and suppress fixed frequencies ineffective. In addition, the characteristic harmonics of subsynchronous oscillations are attenuated to a certain extent when they are transmitted from the oscillation source to the DC system. This means that when the DC system detects the oscillation, the oscillation may already be very severe, and the suppression effect is not obvious.

[0004] In summary, the technical problems existing in the relevant technologies need to be improved. Summary of the Invention

[0005] The embodiments of this application aim to at least partially solve one of the technical problems in the related art. Therefore, the main objective of the embodiments of this application is to propose a method and related equipment for suppressing subsynchronous oscillations in a wind farm via a DC system. This method ensures that the suppression command is safe and reliable, operates within limits, and can quickly act on the DC system to suppress subsynchronous oscillations in a timely manner, thereby improving the subsynchronous oscillation suppression effect.

[0006] To achieve the above objectives, one aspect of this application proposes a method for suppressing subsynchronous oscillations in a wind farm via a DC system, the method comprising the following steps: Obtain the raw instantaneous value data of the current wind farm grid connection point; wherein, the raw instantaneous value data includes the instantaneous values ​​of three-phase voltage and three-phase current; The original instantaneous value data is subjected to subsynchronous oscillation frequency scanning processing to obtain the target dominant oscillation characteristic quantity; The system operating status corresponding to the current wind farm operating condition is obtained, and based on the system operating status and the target dominant oscillation characteristic quantity, it is determined whether the current wind farm operating condition meets the conditions for implementing the suppression strategy; wherein, the system operating status includes the wind farm operating status and the DC system operating status; If it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, then a modulation feasibility analysis is performed on the current wind farm operating conditions based on the system operating status to obtain boundary constraint structured data. Based on the target dominant oscillation characteristic, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point, the original DC power modulation quantity is generated; The original DC power modulation amount is limited and safety verified to generate a subsynchronous oscillation suppression command, which is then sent to the DC system so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command.

[0007] In some embodiments, performing subsynchronous oscillation frequency scanning processing on the original instantaneous value data to obtain the target dominant oscillation characteristic quantity includes: The original instantaneous data is subjected to mode transformation to obtain electrical components; The electrical components are bandpass filtered to obtain the subsynchronous frequency band residual signal; A dynamic data window corresponding to the subsynchronous band residual signal is constructed, and the subsynchronous band residual signal within the current data window is fitted online and subjected to spectrum analysis to obtain the original dominant oscillation characteristic quantity; wherein, the original dominant oscillation characteristic quantity includes the original dominant oscillation frequency and the original dominant oscillation amplitude; The original dominant oscillation feature is subjected to a credibility verification, and the original dominant oscillation feature that passes the credibility verification is subjected to event locking processing to generate the target dominant oscillation feature; wherein, the target dominant oscillation feature includes the target dominant oscillation frequency and the target dominant oscillation amplitude.

[0008] In some embodiments, if it is determined that the current wind farm operating condition meets the conditions for implementing the suppression strategy, then a modulation feasibility analysis is performed on the current wind farm operating condition based on the system operating state to obtain boundary constraint structured data, including: When it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, a suppression enable flag is generated; Based on the DC system operating state in the system operating state, calculate the DC modulation margin corresponding to the current wind farm operating condition; Based on the suppression enable flag, the DC modulation margin, and the current DC power in the DC system operating state, the boundary constraint structured data is constructed.

[0009] In some embodiments, the electrical feedback signal includes a raw frequency deviation signal, and the generation of the raw DC power modulation quantity based on the target dominant oscillation characteristic, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point includes: The original frequency deviation signal is bandpass filtered to obtain the subsynchronous frequency band component; Based on the target dominant oscillation frequency in the target dominant oscillation characteristic quantity, phase compensation is performed on the subsynchronous frequency band component to obtain the subsynchronous frequency band signal. Based on the target dominant oscillation amplitude in the target dominant oscillation characteristic quantity and the current DC power in the boundary constraint structured data, a dynamic gain coefficient is calculated, and an adaptive gain adjustment is performed on the subsynchronous frequency band signal based on the dynamic gain coefficient to generate the original DC power modulation amount.

[0010] In some embodiments, the step of limiting and verifying the original DC power modulation amount, generating a subsynchronous oscillation suppression command, and sending the subsynchronous oscillation suppression command to the DC system, so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command, includes: The original DC power modulation amount is limited according to the preset absolute limiting value to obtain the limited DC power modulation amount. Based on the DC modulation margin in the boundary constraint structured data, the limiting DC power modulation amount is subjected to margin verification processing to generate the target DC power modulation amount. Based on the target DC power modulation amount, the subsynchronous oscillation suppression command is generated and sent to the DC system; In the power reference value input terminal of the DC system, the target DC power modulation amount in the subsynchronous oscillation suppression command is algebraically added to the original power reference value in the power reference value input terminal to obtain the target power reference value, so as to perform subsynchronous oscillation suppression on the current wind farm according to the target power reference value.

[0011] In some embodiments, after sending the subsynchronous oscillation suppression command to the DC system, the method further includes: Dynamically monitor the current DC power response data of the DC system; When it is determined that the current DC power response data is abnormal, the DC power modulation for the next cycle is stopped, the current alarm information is generated and reported to the target host system, and the subsynchronous oscillation suppression command and the current DC power response data are recorded in the fault recording system.

[0012] To achieve the above objectives, another aspect of this application proposes a subsynchronous oscillation suppression device for a wind farm via a DC system, the device comprising the following modules: The raw instantaneous value data acquisition module is used to acquire the raw instantaneous value data of the current wind farm grid connection point; wherein, the raw instantaneous value data includes the instantaneous values ​​of three-phase voltage and three-phase current; The subsynchronous oscillation frequency scanning module is used to perform subsynchronous oscillation frequency scanning processing on the original instantaneous value data to obtain the target dominant oscillation characteristic quantity; The suppression strategy implementation condition judgment module is used to obtain the system operating status corresponding to the current wind farm operating condition, and determine whether the current wind farm operating condition meets the suppression strategy implementation condition based on the system operating status and the target dominant oscillation characteristic quantity; wherein, the system operating status includes the wind farm operating status and the DC system operating status; The modulation feasibility analysis module is used to perform a modulation feasibility analysis on the current wind farm operating conditions based on the system operating status if it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, and to obtain boundary constraint structured data. The DC power modulation generation module is used to generate the original DC power modulation based on the target dominant oscillation characteristic, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point. The subsynchronous oscillation suppression command generation module is used to limit and verify the original DC power modulation amount, generate a subsynchronous oscillation suppression command, and send the subsynchronous oscillation suppression command to the DC system so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command.

[0013] To achieve the above objectives, another aspect of this application provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described method.

[0014] To achieve the above objectives, another aspect of the embodiments of this application proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method.

[0015] To achieve the above objectives, another aspect of this application provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0016] The embodiments of this application include at least the following beneficial effects: This application provides a method and related equipment for suppressing subsynchronous oscillations in a wind farm's DC system. This solution, by scanning the original instantaneous data for subsynchronous oscillation frequencies, can accurately capture all potential subsynchronous oscillation frequencies and amplitudes under the current wind farm operating conditions, and screen out the dominant oscillation characteristic quantities. This allows the embodiments of this application to go beyond single-frequency suppression, identifying multiple subsynchronous oscillation components over a wider frequency range, effectively expanding the coverage and suppression range of subsynchronous oscillation characteristic frequencies. By simultaneously collecting DC data from the grid side and wind farm electrical data from the power source side, and monitoring the wind farm and DC operating status in real time, it can begin responding at the onset of subsynchronous oscillations, avoiding the continuation and amplification of oscillation risks. Furthermore, By combining the wind farm and DC operating status with the target dominant oscillation characteristic quantity, it is possible to accurately determine the conditions for implementing suppression strategies, enabling precise triggering and on-demand implementation of suppression strategies. By performing modulation feasibility analysis on the current wind farm operating conditions to obtain structured boundary constraint data, it is possible to ensure that subsequent modulation operations are always performed within the system's safe operating boundaries, thus improving system operational safety. By combining dominant oscillation characteristics, system constraints, and real-time electrical feedback, it is possible to accurately generate DC power modulation quantities adapted to the current wind farm operating conditions. Finally, by limiting the modulation quantity and performing safety verification to generate suppression commands and issuing them for execution, it is possible to ensure that the suppression commands are safe and reliable, do not exceed the limits, and can quickly act on the DC system to suppress subsynchronous oscillations in a timely manner, thereby improving the subsynchronous oscillation suppression effect. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the steps of a method for suppressing subsynchronous oscillations in a wind farm via a DC system, as provided in an embodiment of this application. Figure 2 This is a schematic diagram of the overall process of a method for suppressing subsynchronous oscillations in a wind farm via a DC system, provided in an embodiment of this application. Figure 3 This is a schematic diagram of the structure of a subsynchronous oscillation suppression device for a wind farm via a DC system, provided in an embodiment of this application. Figure 4 This is a schematic diagram of the hardware structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0019] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various concepts, but unless otherwise stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words “if,” “when,” or “in response to a determination” as used herein may be interpreted as “when…” or “when…” or “in response to a determination.”

[0020] As used in this application, the terms "at least one", "multiple", "each", "any", etc., "at least one" includes one, two or more, "multiple" includes two or more, "each" refers to each of the corresponding multiples, and "any" refers to any one of the multiples.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0022] As an example, subsynchronous oscillation is a potentially significant risk during the operation of large-scale wind farms, which is very likely to damage the wind turbine drive shaft. The DC system connected to the wind farm can generate a current with opposite phase and the same amplitude after detecting the subsynchronous oscillation characteristic subfrequency current harmonic.

[0023] However, as wind farms continue to expand in scale and become more widely distributed, the operation of wind turbines of different capacities, regions, and models results in the characteristic frequency of subsynchronous oscillations no longer being singular, but exhibiting multi-frequency characteristics. This makes the previous method of DC systems only being able to detect and suppress fixed frequencies ineffective. In addition, the characteristic harmonics of subsynchronous oscillations are attenuated to a certain extent when they are transmitted from the oscillation source to the DC system. This means that when the DC system detects the oscillation, the oscillation may already be very severe, and the suppression effect is not obvious.

[0024] In view of this, this application provides a method and related equipment for suppressing subsynchronous oscillations in a wind farm via a DC system. This method, by scanning the original instantaneous data for subsynchronous oscillation frequencies, can accurately capture all potential subsynchronous oscillation frequencies and amplitudes under the current wind farm operating conditions, and screen out the dominant oscillation characteristic quantities. This allows the application to go beyond single-frequency suppression, identifying multiple subsynchronous oscillation components over a wider frequency range, effectively expanding the coverage and suppression range of subsynchronous oscillation characteristic frequencies. By simultaneously collecting DC data from the grid side and wind farm electrical data from the power source side, and monitoring the wind farm and DC operating status in real time, it can respond at the onset of subsynchronous oscillations, avoiding the continuation and amplification of oscillation risks. Furthermore, by... By combining the electric field and DC operating status with the target dominant oscillation characteristic quantity, it is possible to accurately determine the conditions for implementing suppression strategies, enabling precise triggering and on-demand implementation of suppression strategies. By performing modulation feasibility analysis on the current wind farm operating conditions to obtain structured boundary constraint data, it is possible to ensure that subsequent modulation operations are always carried out within the system's safe operating boundaries, thereby improving system operational safety. By combining dominant oscillation characteristics, system constraints, and real-time electrical feedback, it is possible to accurately generate DC power modulation quantities adapted to the current wind farm operating conditions. Finally, by limiting the modulation quantity and performing safety verification to generate suppression commands and issuing them for execution, it is possible to ensure that the suppression commands are safe and reliable, do not exceed the limits, and can quickly act on the DC system to suppress subsynchronous oscillations in a timely manner, thereby improving the subsynchronous oscillation suppression effect.

[0025] This application provides a method for suppressing subsynchronous oscillations in a wind farm connected to a DC system, relating to the field of wind farm grid-connected control technology. This method can be applied to a terminal, a server, or software running on either a terminal or a server. In some embodiments, the terminal can be a smartphone, tablet, laptop, desktop computer, smart speaker, smartwatch, or vehicle terminal, but is not limited to these. The server can be configured as an independent physical server, a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms. The server can also be a node server in a blockchain network. The software can be an application implementing a method for suppressing subsynchronous oscillations in a wind farm connected to a DC system, but is not limited to the above forms.

[0026] This application can be used in a wide variety of general-purpose or special-purpose computer system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics devices, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices. This application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform specific tasks or implement specific abstract data types. This application can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0027] Please see Figure 1 , Figure 1 This is an optional flowchart of a method for suppressing subsynchronous oscillations in a wind farm via a DC system, as provided in an embodiment of this application. Figure 1 The method may include, but is not limited to, steps S101 to S106.

[0028] Step S101: Obtain the original instantaneous value data of the current wind farm grid connection point; wherein, the original instantaneous value data includes the instantaneous values ​​of three-phase voltage and three-phase current; The point of common coupling (PCC) is the common node connecting the internal collection system of the wind farm to the external AC power grid, and it is also the key electrical interface for wind power to enter the grid.

[0029] The raw instantaneous data refers to the original electrical sampling data directly collected at the grid connection point, without any processing such as filtering, coordinate transformation, or numerical calculation. It only reflects the real waveforms of voltage and current changing in real time. The raw instantaneous data includes the instantaneous values ​​of three-phase voltage and three-phase current.

[0030] In the specific implementation, firstly, by installing a high-precision broadband measurement device or connecting to an existing synchronous phasor measurement unit at the wind farm grid connection point (PCC), the raw instantaneous value data stream of the grid connection point is collected in real time and synchronously. The raw instantaneous value data stream includes the instantaneous values ​​of three-phase voltage u_a(t), u_b(t), u_c(t) and the instantaneous values ​​of three-phase current i_a(t), i_c(t), i_c(t).

[0031] Step S102: Perform subsynchronous oscillation frequency scanning processing on the original instantaneous value data to obtain the target dominant oscillation characteristic quantity; In some embodiments, step S102 may include: performing mode transformation processing on the original instantaneous value data to obtain electrical components; performing bandpass filtering processing on the electrical components to obtain subsynchronous band residual signals; constructing a dynamic data window corresponding to the subsynchronous band residual signals, and performing online fitting and spectrum analysis on the subsynchronous band residual signals within the current data window to obtain the original dominant oscillation characteristic quantity; wherein, the original dominant oscillation characteristic quantity includes the original dominant oscillation frequency and the original dominant oscillation amplitude; performing credibility verification on the original dominant oscillation characteristic quantity, and performing event locking processing on the original dominant oscillation characteristic quantity that passes the credibility verification to generate a target dominant oscillation characteristic quantity; wherein, the target dominant oscillation characteristic quantity includes the target dominant oscillation frequency and the target dominant oscillation amplitude.

[0032] The original dominant oscillation characteristic parameters are subsynchronous oscillation characteristic parameters that have been initially identified through algorithms such as frequency scanning and spectrum analysis, but have not yet undergone reliability screening and stability locking. They mainly include the original dominant oscillation frequency and the original dominant oscillation amplitude. The target dominant oscillation characteristic parameters are stable, reliable, and effective subsynchronous oscillation characteristic parameters that are finally obtained after the original dominant oscillation characteristic parameters have undergone reliability verification, outlier removal, and oscillation event locking. They mainly include the target dominant oscillation frequency and the target dominant oscillation amplitude.

[0033] In the specific implementation, firstly, the acquired instantaneous values ​​of three-phase voltage u_a(t), u_b(t), u_c(t) and three-phase current i_a(t), i_c(t), i_c(t) are converted into voltage components u_α(t), u_β(t) and current components i_α(t), i_β(t) in a two-phase stationary coordinate system through Clark transform or Park transform, respectively. Then, the voltage components u_α(t), u_β(t) and current components i_α(t), i_β(t) in the two-phase stationary coordinate system are further converted into voltage components u_d(t), u_q(t) and current components i_d(t), i_q(t) in a rotating coordinate system. Finally, the voltage components u_d(t), u_q(t) and current components i_d(t), i_q(t) in the rotating coordinate system are filtered out by a bandpass filter to remove power frequency components and higher-order components. Harmonics are analyzed to obtain the subsynchronous band residual signals Δu(t) and Δi(t). Next, a dynamic data window is established for the subsynchronous band residual signals Δu(t) and Δi(t). The Prony algorithm, TLS-ESPRIT algorithm, or adaptive notch filter are used to perform online fitting and spectral analysis on the data within the current data window, identifying and calculating the dominant oscillation mode with the highest energy within the current data window. The specific parameters of the dominant oscillation mode include the dominant oscillation frequency f_SSO and the dominant oscillation amplitude A_SSO. This step yields the original dominant oscillation characteristic. Further, the original dominant oscillation characteristic is verified for reliability and confirmed for events to obtain the target dominant oscillation characteristic. The target dominant oscillation characteristic includes the locked oscillation frequency f_SSO_lock (i.e., the target dominant oscillation frequency) and the locked oscillation amplitude A_SSO_lock (i.e., the target dominant oscillation amplitude).

[0034] In the embodiments of this application, by using mode transformation, bandpass filtering, dynamic data window analysis, and credibility verification and event locking processing, stable and reliable subsynchronous dominant oscillation characteristics can be accurately and in real time extracted after filtering out interference noise. This effectively avoids misidentification and result jumps caused by disturbances and frequency drift, providing accurate and reliable input parameters for subsequent oscillation suppression and improving the stability and accuracy of system detection and control.

[0035] Step S103: Obtain the system operating status corresponding to the current wind farm operating condition, and determine whether the current wind farm operating condition meets the conditions for implementing the suppression strategy based on the system operating status and the target dominant oscillation characteristic quantity; wherein, the system operating status includes the wind farm operating status and the DC system operating status; Among them, the current wind farm operating condition is the actual operating condition of the wind farm at the current moment, which is formed by a combination of factors such as wind speed, number of operating units, active power output, and electrical characteristics of the grid connection point, reflecting the overall operating conditions of the wind farm at the current moment.

[0036] The system operating status includes both the wind farm operating status and the DC system operating status. The wind farm operating status consists of parameters describing the wind farm's own operation, which may include current wind speed, total active power output P_wind, turbine type (doubly fed / direct driven), and number of grid-connected turbines. The DC system operating status consists of parameters describing the operation of the DC system connected to the wind farm, which may include DC transmission power P_dc, DC voltage V_dc, converter station firing angle / shutdown angle, and current control mode (constant power / constant current).

[0037] The conditions for implementing the suppression strategy are pre-set judgment conditions that must be met to initiate subsynchronous oscillation suppression control.

[0038] Step S104: If it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, then a modulation feasibility analysis is performed on the current wind farm operating conditions based on the system operating status to obtain boundary constraint structured data. In some embodiments, step S104 may include: generating a suppression enable flag when it is determined that the current wind farm operating condition meets the suppression strategy input conditions; calculating the DC modulation margin corresponding to the current wind farm operating condition based on the DC system operating state in the system operating state; and constructing boundary constraint structured data based on the suppression enable flag, the DC modulation margin, and the current DC power in the DC system operating state.

[0039] The suppression enable flag is an identifier used to indicate whether the current wind farm operating conditions allow the implementation of the subsynchronous oscillation suppression strategy.

[0040] DC modulation margin refers to the maximum adjustable space for a DC transmission system to safely and stably increase or decrease the transmission power under the current operating state. It is divided into upward modulation margin and downward modulation margin. It is a core constraint parameter that limits the power modulation range and is used to prevent DC power regulation from exceeding the operating limits of the equipment.

[0041] In this embodiment, by generating a suppression enable flag, calculating the DC modulation margin, and constructing boundary constraint structured data, the safe adjustable range and input permission conditions of DC power modulation can be clearly defined, providing clear operational boundary constraints for subsequent suppression command generation, effectively avoiding power modulation exceeding limits or over-modulation problems, improving the feasibility of oscillation suppression, and ensuring the safe and stable operation of the DC system and wind farm connected to the grid.

[0042] Step S105: Based on the target dominant oscillation characteristic quantity, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point, generate the original DC power modulation quantity; The electrical feedback signal includes a frequency deviation signal, defined as the difference between the measured frequency at the grid connection point and the rated frequency. The measured frequency originates from the voltage waveform acquired in step S101 and is calculated in real time using a phase-locked loop (PLL) or zero-crossing detection algorithm, with an update rate of no less than 1 kHz. This frequency deviation signal naturally contains a frequency modulation component caused by subsynchronous oscillation and is the preferred input for the subsynchronous oscillation command generation strategy.

[0043] In this embodiment of the application, the electrical feedback signal also includes a power deviation signal, which is defined as the difference between the measured active power at the wind farm grid connection point and the steady-state reference value, and is used as a substitute input for frequency deviation when the frequency measurement is severely disturbed.

[0044] In some embodiments, step S105 may include: performing bandpass filtering on the original frequency deviation signal to obtain a subsynchronous frequency band component; performing phase compensation on the subsynchronous frequency band component based on the target dominant oscillation frequency in the target dominant oscillation characteristic quantity to obtain a subsynchronous frequency band signal; calculating a dynamic gain coefficient based on the target dominant oscillation amplitude in the target dominant oscillation characteristic quantity and the current DC power in the boundary constraint structured data, and performing adaptive gain adjustment on the subsynchronous frequency band signal based on the dynamic gain coefficient to generate the original DC power modulation amount.

[0045] In this embodiment, a pure subsynchronous frequency band component is extracted by bandpass filtering and adaptive phase compensation is achieved by combining it with the dominant oscillation frequency. At the same time, the modulation gain is dynamically adjusted according to the oscillation amplitude and DC operating power. This ensures that the suppression signal phase matches to provide effective damping, and allows the modulation intensity to adapt to the actual oscillation degree and DC operating conditions, which greatly improves the accuracy, adaptability and damping effect of oscillation suppression.

[0046] Step S106: Limit and verify the original DC power modulation amount, generate a subsynchronous oscillation suppression command, and send the subsynchronous oscillation suppression command to the DC system so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command.

[0047] In some embodiments, step S106 may include: limiting the original DC power modulation amount according to a preset absolute limiting value to obtain a limited DC power modulation amount; performing margin verification processing on the limited DC power modulation amount according to the DC modulation margin in the boundary constraint structured data to generate a target DC power modulation amount; generating a subsynchronous oscillation suppression command based on the target DC power modulation amount and sending the subsynchronous oscillation suppression command to the DC system; and performing algebraic addition of the target DC power modulation amount in the subsynchronous oscillation suppression command and the original power reference value in the power reference value input terminal of the DC system to obtain a target power reference value, so as to perform subsynchronous oscillation suppression on the current wind farm according to the target power reference value.

[0048] The DC system refers to the DC transmission system built in conjunction with the wind farm for transmitting wind power to other regions. It is typically a flexible DC transmission system or a basic DC transmission system. In practice, the AC power generated by the wind farm is collected and connected to the DC system. The DC system then performs rectification, DC transmission, and inversion for grid connection, enabling long-distance transmission of wind power to the main power grid. Simultaneously, the DC system has the ability to rapidly adjust the transmitted power and can generate damping torque through superimposed power modulation commands, thereby suppressing subsynchronous oscillations generated during the grid-connected operation of the wind farm.

[0049] This application embodiment ensures that the final generated target DC power modulation is within a safe and adjustable range by performing multi-level limiting and margin verification on the original DC power modulation amount, thus avoiding the risk of exceeding limits and over-modulation. By superimposing the suppression command onto the original power reference value of the DC system, damping can be quickly applied to suppress subsynchronous oscillations without changing the basic DC power transmission function. This improves the suppression effect while ensuring the safety and stability of the DC system and the grid-connected operation of the wind farm.

[0050] In some embodiments, after sending the subsynchronous oscillation suppression command to the DC system, the method may further include: dynamically monitoring the current DC power response data of the DC system; when it is determined that the current DC power response data is abnormal, stopping the DC power modulation for the next cycle, generating current alarm information and reporting it to the target host system, and recording the subsynchronous oscillation suppression command and the current DC power response data to the fault recording system.

[0051] This application embodiment dynamically monitors the power response of the DC system and promptly blocks modulation, reports alarms, and records fault waveforms when abnormalities occur. This can quickly avoid system risks caused by abnormal suppression strategies, while retaining complete fault data for subsequent analysis and location, further improving the safety of wind farm operation via DC grid connection.

[0052] Steps S101 to S106 of this application embodiment, by performing subsynchronous oscillation frequency scanning processing on the original instantaneous value data, can accurately capture all potential subsynchronous oscillation frequencies and amplitudes under the current wind farm operating conditions, and screen out the dominant oscillation characteristic quantities. This allows this application embodiment to go beyond single-frequency suppression and identify multiple subsynchronous oscillation components over a wider frequency range, effectively expanding the coverage and suppression range of subsynchronous oscillation characteristic frequencies. By simultaneously collecting DC and wind farm electrical data from the grid side and the power source side, and monitoring the wind farm and DC operating status in real time, a response can begin at the onset of subsynchronous oscillation, avoiding the continuation and amplification of oscillation risks. Furthermore, by monitoring the wind farm and DC operating status... By combining the dominant oscillation characteristics, the system can accurately determine the conditions for implementing suppression strategies, enabling precise triggering and on-demand implementation of these strategies. Through modulation feasibility analysis of the current wind farm operating conditions, structured boundary constraint data is obtained, ensuring that subsequent modulation operations always operate within the system's safe operating boundaries, thus improving system operational safety. By combining dominant oscillation characteristics, system constraints, and real-time electrical feedback, the system can accurately generate DC power modulation quantities suitable for the current wind farm operating conditions. Finally, by limiting and verifying the modulation quantity, suppression commands are generated and issued for execution, ensuring the suppression commands are safe, reliable, and do not exceed limits. These commands can also quickly act on the DC system, promptly suppressing subsynchronous oscillations and improving the subsynchronous oscillation suppression effect.

[0053] To explain in detail the principles of the technical solution of this application, the overall process of this application will be described below with reference to some specific embodiments. It is easy to understand that the following is an explanation of the technical principles of this application and should not be regarded as a limitation of this application.

[0054] Please see Figure 2 , Figure 2 This is a schematic diagram of the overall process of a method for suppressing subsynchronous oscillations in a wind farm via a DC system, as provided in an embodiment of this application. Figure 2 As shown in the figure, the overall process of a method for suppressing subsynchronous oscillations in a wind farm via a DC system provided in this application mainly includes the following steps A-C: A. Wind farm subsynchronous oscillation frequency scan; The purpose of step A is to monitor and identify the risk of subsynchronous oscillations in the wind farm in real time, and to accurately calculate the frequency and amplitude of the oscillations. The specific implementation of step A includes, but is not limited to, the following steps A1-A3: A1. Data Acquisition: In the specific implementation, firstly, by installing a high-precision broadband measurement device at the wind farm grid connection point (PCC) or connecting to an existing synchronous phasor measurement unit, the raw instantaneous value data stream of the grid connection point is acquired in real time and synchronously. The raw instantaneous value data stream includes the instantaneous values ​​of three-phase voltage u_a(t), u_b(t), u_c(t) and the instantaneous values ​​of three-phase current i_a(t), i_c(t), i_c(t). Then, the raw instantaneous value data stream acquired in step A1 is transmitted in real time to step A2 for processing.

[0055] Regarding sampling requirements, in this embodiment of the application, to accurately capture the subsynchronous components in the range of 5Hz-50Hz, the sampling frequency must satisfy the Nyquist sampling theorem, and preferably the sampling frequency fs≥10kHz. It should be noted that the acquisition requirements can be set according to monitoring accuracy, hardware performance, and operating conditions in practical applications, and are not limited to the above examples; this embodiment of the application does not impose any limitations on this.

[0056] A2. Signal Processing and Feature Extraction: A2.1 Mode Transformation: The instantaneous three-phase voltage values ​​u_a(t), u_b(t), u_c(t) and the instantaneous three-phase current values ​​i_a(t), i_c(t), i_c(t) collected in step A1 are converted into voltage components u_α(t), u_β(t) and current components i_α(t), i_β(t) in a two-phase stationary coordinate system by Clark transformation or Park transformation, respectively. Then, the voltage components u_α(t), u_β(t) and current components i_α(t), i_β(t) in the two-phase stationary coordinate system are further converted into voltage components u_d(t), u_q(t) and current components i_d(t), i_q(t) in a rotating coordinate system.

[0057] A2.2 Filtering out power frequency components: The voltage components u_d(t), u_q(t) and current components i_d(t), i_q(t) in the rotating coordinate system are passed through a bandpass filter to filter out power frequency components and higher harmonics, resulting in residual signals Δu(t) and Δi(t) in the subsynchronous frequency band, such as 5Hz~45Hz. The residual signals Δu(t) and Δi(t) in the subsynchronous frequency band are the specific manifestations of the subsynchronous components contained in the original instantaneous value data stream collected in step A1.

[0058] In step A2.2, since the subsynchronous oscillation signal is usually a weak modulation signal superimposed on the power frequency, the pure disturbance component can be extracted after filtering out the power frequency, that is, the subsynchronous frequency band residual signals Δu(t) and Δi(t) are obtained.

[0059] A2.3 Frequency Scanning Algorithm: First, a dynamic data window is established for the subsynchronous band residual signals Δu(t) and Δi(t) obtained in step A2.2. For example, the window length can be selected as 100ms~200ms, corresponding to 2-5 subsynchronous cycles, and the sliding step size is generally half a cycle. Then, the Prony algorithm, TLS-ESPRIT algorithm or adaptive notch filter is used to perform online fitting and spectrum analysis on the data in the current data window, identify and calculate the dominant oscillation mode with the largest energy in the current data window. The specific parameters of the dominant oscillation mode include the dominant oscillation frequency f_SSO and the dominant oscillation amplitude A_SSO.

[0060] The dominant oscillation frequency f_SSO (unit: Hz) serves as the design basis for the phase compensation stage in subsequent step C; the dominant oscillation amplitude A_SSO (unit: pu or kV) is used to determine the severity of the oscillation and serves as the input for gain adjustment in step C.

[0061] A3. Credibility Verification and Event Confirmation Step A3 is used to post-process the calculation results of multiple data windows continuously output in step A2 to eliminate misjudgments caused by accidental interference, and finally confirm the subsynchronous oscillation event, outputting a stable oscillation frequency and dominant oscillation amplitude.

[0062] A3.1 Data Caching and Consistency Comparison: First, establish a first-in-first-out (FIFO) cache queue of length M (e.g., M=5) to store the dominant oscillation frequency f_i and dominant oscillation amplitude A_i (i=1,...,M) calculated from the most recent M data windows. Then, whenever a new set of calculation results (f_n, A_n) is generated in step A2, the new calculation result (f_n, A_n) is stored in the FIFO cache queue, and the standard deviation σ_f of all frequency values ​​in the current FIFO cache queue is calculated. If the standard deviation σ_f is greater than the preset frequency fluctuation threshold ε (e.g., ε=0.5Hz), it indicates that the frequency dispersion in the queue is too large, which may contain noise or interference points. In this case, the result of the current data window is not used for event confirmation, the queue is cleared or the earliest data point is removed, and subsequent data is awaited.

[0063] A3.2 Continuous Trigger Counting: First, set up an event counter K with an initial value of 0; then, for each data window that passes the consistency check (i.e., the point is determined to be reliable), determine whether its dominant oscillation amplitude A_n exceeds the preset trigger threshold A_th (e.g., 0.01 pu), as follows: If the dominant oscillation amplitude A_n > the preset start threshold A_th, then the counter K = K + 1; If the dominant oscillation amplitude A_n ≤ the preset start threshold A_th, then the counter K is cleared to zero; If a data window is removed due to a consistency check, the counter K remains unchanged, or is reset to zero depending on the specific design or for safety reasons.

[0064] A3.3 Event Confirmation and Parameter Locking: When the counter K continuously reaches the preset number of confirmations N (e.g., N=3, corresponding to 3 consecutive trusted data windows exceeding the threshold), the occurrence of a secondary synchronous oscillation event is formally confirmed. At this time, the locking rules for the dominant oscillation frequency f_SSO and the dominant oscillation amplitude A_SSO are as follows: Lock the oscillation frequency f_SSO_lock: Take the average frequency of the N data windows involved in the counting, that is, lock the oscillation frequency f_SSO_lock=(f_{n-N+1}+...+f_n) / N to ensure the smoothness and accuracy of the frequency value; Lock oscillation amplitude A_SSO_lock: Take the maximum (or latest) amplitude of the N data windows involved in the counting to reflect the most severe degree of oscillation, i.e., lock oscillation amplitude A_SSO_lock=max(A_{n-N+1},...,A_n).

[0065] In this embodiment, the locked oscillation frequency f_SSO_lock and the locked oscillation amplitude A_SSO_lock are used as the output of step A and sent to step C in real time for suppressing instruction generation.

[0066] A3.4 is continuously updated: During the duration of the oscillation event, the above verification is performed on subsequent data windows. If the lock oscillation frequency drifts significantly (e.g., exceeds the preset frequency band), the process of step A above is re-executed to update f_SSO_lock and A_SSO_lock, thereby achieving dynamic tracking.

[0067] B. Collection of wind farm and DC operation status; The purpose of step B is to collect the boundary conditions before the implementation of the suppression measures, in order to determine whether the current operating conditions are suitable for implementing the suppression strategy and to calculate the control strength. The specific implementation of step B includes, but is not limited to, the following steps B1-B3: B1. Wind farm operation status collection: Data content includes: current wind speed, total active power output of the wind farm P_wind, type of turbines in the wind farm (doubly fed / direct driven) and number of grid-connected turbines, etc.

[0068] The operating status of the wind farm can be used to assess the source of oscillation energy. For example, if the wind farm output is too low (e.g., less than 10% of the rated power), the oscillation energy may be weak. The suppression strategy needs to consider the setting of modulation dead zone. The specific handling of modulation dead zone is reflected in step C2.3 below.

[0069] B2. DC system operating status collection: Data content: DC transmission power P_dc, DC voltage V_dc, converter station firing angle / shutdown angle, current control mode (constant power / constant current), etc.

[0070] The operating status of the DC system can be used to assess the controllability margin of the DC system. For example, if the DC system is operating at full capacity (e.g., P_dc is close to its rated value), the suppression command can only adjust the power downwards; if the DC system is operating at minimum power, the suppression command can only adjust the power upwards.

[0071] B3. Feasibility Analysis of State Logic Judgment and Modulation: Step B3, based on the oscillation characteristic quantity output in step A and the wind farm operation status and DC system operation status collected in step B, determines whether the current wind farm operating condition meets the conditions for the suppression strategy to be implemented through preset multi-dimensional logic rules, and determines the allowable modulation direction and intensity margin, providing boundary constraints for generating safe suppression commands in step C.

[0072] B3.1 Comprehensive judgment of input conditions, namely the above-mentioned conditions for implementing the suppression strategy: The following three basic conditions must be met simultaneously as admission criteria for the implementation of the suppression strategy: Condition 1, Oscillation amplitude exceeds threshold: The locked oscillation amplitude A_SSO_lock output in step A must be greater than the preset start threshold A_th (typical value 0.01pu). This threshold is used to distinguish between effective oscillation and background noise to avoid frequent device operation.

[0073] For example, the condition is met when the detected amplitude is 0.03 pu; the condition is not met if the amplitude is only 0.005 pu.

[0074] Condition 2: The wind farm has a controllable energy base: The total active power output P_wind of the wind farm must be greater than the minimum output threshold P_wind_min (typically 10% of rated capacity). The physical mechanism of this condition is that when the wind farm output is too low, the oscillation energy is weak, and the additional control measures will not only have limited effect, but may also cause unnecessary power fluctuations due to modulation.

[0075] For example, a wind farm with a rated capacity of 300MW currently has an output of 180MW (60%), which satisfies the condition; if the output is only 15MW (5%), the condition does not exist.

[0076] Condition 3: The DC system can receive modulation commands: The DC system must be in an operating mode capable of receiving additional power modulation (usually constant power control mode), and the converter station control system must have no fault-blocking signals, and the relevant communication channels must be normal. For multi-terminal or multi-pole DC systems, this condition is considered met as long as at least one pole is available.

[0077] For example, the condition is met when the DC is operating in constant power mode and there is no alarm; if the power modulation function is deactivated due to constant voltage mode or pole maintenance state, the condition is not met.

[0078] B3.2 Modulation Margin Calculation: When all three conditions in step B3.1 are met, the system determines that the suppression strategy is allowed, and further calculates the controllable margin of DC for the limiting control in step C: The up-modulation margin M_up = P_dc_max - P_dc_current, where P_dc_max is the maximum allowable power under the current DC operating mode (usually the rated value), and P_dc_current is the current DC transmission power; Down modulation margin M_down = P_dc_current - P_dc_min, where P_dc_min is the minimum DC technical power (considering the lower limit of stable operation of the converter, such as 10% of the rated power).

[0079] If the modulation margin in a certain direction is too small (e.g., less than the preset modulation dead zone, such as 1% of the rated power), then step C should limit the modulation amount in that direction, or even allow only unidirectional modulation.

[0080] For example, assuming the current DC transmission power is 2000MW, the rated power is 3000MW, and the minimum power is 300MW, then bidirectional modulation is allowed when the up margin is 1000MW and the down margin is 1700MW; if the current DC transmission power is 2950MW and the up margin is only 50MW, then the actual allowed up modulation amount is extremely small, and step C needs to be automatically limited.

[0081] B3.3 Special Operating Condition Handling: Low wind farm output condition: When condition 2 in step B3.1 is not met, even if the oscillation amplitude exceeds the limit, the suppression strategy is locked and an event record of "wind farm output is too low, suppression is not activated" is reported to the monitoring system.

[0082] DC Unadjustable Operating Condition: When condition 3 in step B3.1 is not met, the suppression strategy is blocked and a "DC modulation unavailable" alarm is reported, prompting the operator to check the DC control mode or equipment status.

[0083] Multi-terminal / multi-pole DC: If some poles are available, margin calculation and subsequent modulation are only performed on the available poles; unavailable poles are not involved in suppression. Furthermore, the additional instructions generated in step C must be issued separately for each pole.

[0084] B3.4 Output data format: Step B3 ultimately outputs the following boundary constraint structured data to step C as the safety boundary for the generation of the suppression instruction: Suppress the enable flag: enable_flag: ENABLE or DISABLE; If ENABLE is enabled, the following information is provided: the current power P_dc_current of each available pole; the up margin M_up and down margin M_down of each available pole; and the suggested modulation direction (bidirectional / upward only / downward only). If DISABLE is not enabled, a reason code will be provided (such as AMPLITUDE_BELOW_THRESHOLD, WIND_POWER_TOO_LOW, DC_MODULATION_UNAVAILABLE).

[0085] This output ensures that step C can generate both effective and safe suppression instructions, provided that the system boundaries are fully understood.

[0086] C. The subsynchronous oscillation command is generated and sent to the DC system.

[0087] Step C is the core execution step of this application. Based on the oscillation characteristic quantities (frequency f_SSO_lock, amplitude A_SSO_lock) output from step A, the boundary constraint structured data output from step B, and the electrical feedback signal from the real-time measurement system, an original additional damping control signal (i.e., the original modulation quantity described below) is generated. Then, the additional damping control signal, after safety verification, is sent to the DC control system in the form of a subsynchronous oscillation suppression command to achieve active suppression of subsynchronous oscillations. The specific implementation of step C includes, but is not limited to, the following steps C1-C3: C1. Suppress instruction generation algorithm: Step C1 involves fusing broadband measurement information with the system operating boundary and generating an additional power modulation quantity that precisely matches the oscillation frequency and is appropriately adapted to the amplitude through dynamic phase compensation and adaptive gain adjustment.

[0088] C1.1 Input signal definition: (1) Oscillation characteristic quantity from step A: Locked oscillation frequency f_SSO_lock (unit: Hz); Lock the oscillation amplitude A_SSO_lock (unit: pu); (2) Boundary constraints from step B: suppress enable flag enable_flag (if it is DISABLE, this step will not be executed); DC current power P_dc_current (unit: MW); up modulation margin M_up and down modulation margin M_down for each available pole (unit: MW); (3) Feedback signals from the real-time measurement system: Frequency deviation Δf: Defined as the difference between the measured frequency at the grid connection point and the rated frequency (50Hz), i.e., frequency deviation Δf = f_measure - 50. The measured frequency f_measure originates from the voltage waveform acquired in step A1 and is calculated in real time through a phase-locked loop (PLL) or zero-crossing detection algorithm, with an update rate of no less than 1kHz. This frequency deviation signal naturally contains a frequency modulation component caused by subsynchronous oscillation and is the preferred input for the subsynchronous oscillation command generation strategy; Power deviation ΔP: Defined as the difference between the measured active power at the grid connection point of the wind farm and the steady-state reference value, used as a substitute input for frequency deviation Δf when the frequency measurement is severely disturbed.

[0089] C1.2 Overall Architecture of Control Link: The suppression command generation link in this embodiment adopts a four-stage cascaded structure of bandpass filtering, phase compensation, gain adjustment, and amplitude limiting output. Specifically, firstly, the original frequency deviation Δf is filtered by a bandpass filter to obtain the subsynchronous frequency band component Δf_band; then, the subsynchronous frequency band component Δf_band is phase compensated to obtain the subsynchronous frequency band signal Δf_compensated (i.e., the phase-corrected signal); next, the subsynchronous frequency band signal Δf_compensated is adaptively gain-adjusted using a dynamic gain coefficient K to obtain the original modulation amount ΔP_raw; further, the original modulation amount ΔP_raw is amplitude-limited and margin-checked to obtain the final target modulation amount ΔP_order; finally, the target modulation amount ΔP_order is sent to the DC system in the form of a subsynchronous oscillation suppression command to achieve active suppression of subsynchronous oscillation.

[0090] C1.3 generates the original modulation amount: C1.3.1 Bandpass Filter: The original frequency deviation signal Δf contains various frequency components, such as power frequency fluctuations, interharmonics, and noise. To extract the effective components related to subsynchronous oscillations, the passband range of the bandpass filter is set to 5Hz~45Hz, covering the typical subsynchronous oscillation frequency band. The filter type is either an Infinite Impulse Response (IIR) filter or a Finite Impulse Response (FIR) filter. The design specifications must ensure that the amplitude is flat within the passband and the phase characteristics are as linear as possible (to facilitate subsequent compensation).

[0091] In this step, the original frequency deviation Δf is filtered by a bandpass filter to obtain the subsynchronous frequency band component Δf_band, which is the frequency deviation signal containing only the subsynchronous frequency band component.

[0092] C1.3.2 Phase Compensation: The core of subsynchronous oscillation suppression lies in ensuring that the electromagnetic torque generated by the additional power modulation falls within the positive damping region of the shaft mechanical oscillation. Since phase lag exists in DC systems, AC power grids, and measurement components, phase lead compensation must be performed on the input signal.

[0093] In this embodiment, firstly, using the lock oscillation frequency f_SSO_lock provided in step A as the current dominant oscillation frequency, the required compensation angle φ_comp is determined. The compensation angle φ_comp can be tuned through offline simulation or field testing, with a typical value of 30°~60°. Then, combining the lock oscillation frequency f_SSO_lock and the compensation angle φ_comp, the time constants T_lead and T_lag of the compensation stage are dynamically calculated. Next, based on the time constants T_lead and T_lag, a transfer function G_comp(s) is designed using multiple cascaded first-order lead-lag stages. The transfer function G_comp(s) is: G_comp(s)=[(1+sT_lead) / (1+sT_lag)]^k; Where T_lead and T_lag are time constants, dynamically calculated based on f_SSO_lock to ensure a preset lead angle φ_comp is provided at frequency f_SSO_lock; k is the number of elements (usually 2 or 3); and s is a Laplace complex variable.

[0094] After constructing the transfer function G_comp(s), the subsynchronous band component Δf_band obtained in step C1.3.1 is input into the transfer function G_comp(s), and the subsynchronous band signal Δf_compensated is output, which is the subsynchronous band signal after phase correction. The phase of the signal Δf_compensated has been adjusted to the optimal value, so that the final generated power modulation can provide positive damping.

[0095] In the specific implementation, when step A detects an oscillation frequency drift, f_SSO_lock is updated. This step will also immediately recalculate the time constants T_lead and T_lag to achieve frequency-adaptive phase compensation and avoid the failure of traditional fixed-parameter filters when the frequency shifts.

[0096] C1.3.3 Adaptive gain adjustment: In this embodiment, to match the suppression intensity with the severity of oscillation, a dynamic gain coefficient K is set, wherein the formula for calculating the dynamic gain coefficient K is: K=K_base×(A_SSO_lock / A_ref)×α(P_dc_current); Wherein, K_base is the base gain coefficient, tuned through offline simulation (typical value 0.1~0.5 pu / Hz); A_SSO_lock / A_ref is the amplitude normalization factor, A_SSO_lock is the locked oscillation amplitude, and A_ref is the reference amplitude (e.g., 0.01 pu). The amplitude normalization factor makes the gain increase linearly with the oscillation amplitude, achieving small suppression of small oscillations and strong suppression of large oscillations; α(P_dc_current) is the DC power influence factor, P_dc_current is the current DC power. The DC power influence factor is used to consider the modulation capability of DC under different load levels.

[0097] For example, α = min(1, P_dc_current / P_rated) or a more complex nonlinear function ensures that the gain is appropriately reduced under light load to avoid overmodulation, where P_rated is the rated power.

[0098] In this step, the amplitude of the original modulation amount ΔP_raw = K × Δf_compensated is adaptively matched with the oscillation amplitude and the DC operating point. The original modulation amount ΔP_raw (unit: MW or pu) has the correct phase (providing positive damping) and the appropriate amplitude (intensity adaptation), but the original modulation amount ΔP_raw has not yet been checked for safety boundaries, so the amplitude limiting and safety check in step C2 are required.

[0099] C2. Limiting and Security Verification: Step C2 ensures that the additional control signal does not exceed the safe operating range of the DC system by limiting the amplitude and adjusting the margin of the original modulation amount ΔP_raw.

[0100] C2.1 Amplitude Limiting: First, set an absolute limit value ΔP_max, which is usually ±5% of the rated DC power (e.g., 150MW) to prevent excessive modulation from impacting the converter; then, limit the original modulation amount ΔP_raw to obtain the limited DC power modulation amount ΔP_clipped=max(min(ΔP_raw,+ΔP_max),-ΔP_max).

[0101] C2.2 Margin Check and Orientation Adaptation: Based on the modulation margin provided in step B, further limit the modulation amount: If the limited DC power modulation amount ΔP_clipped > 0 (up modulation), then the maximum allowed up modulation amount is M_up. The actual output DC power modulation amount ΔP_limited = min(ΔP_clipped, M_up), and the actual output DC power modulation amount ΔP_limited is used as the final target modulation amount ΔP_order.

[0102] If the limited DC power modulation amount ΔP_clipped < 0 (down modulation), then the maximum allowed down modulation amount is M_down. The actual output DC power modulation amount ΔP_limited = max(ΔP_clipped, -M_down), and the actual output DC power modulation amount ΔP_limited is used as the final target modulation amount ΔP_order.

[0103] If the margin in a certain direction is zero or extremely small (e.g., less than 1% of the rated power), the modulation amount in that direction is automatically set to zero to avoid exceeding the limit.

[0104] C2.3 Dead-band handling: To prevent frequent operation caused by minor disturbances, a modulation dead-band ΔP_deadband is set (e.g., 0.5% of the rated power). If |ΔP_limited| < ΔP_deadband, the final output ΔP_order = 0.

[0105] C2.4 Output the final modulation command: After the above verification, the final target modulation amount ΔP_order is obtained. The final target modulation amount ΔP_order exists in the form of a subsynchronous oscillation suppression command. This command is strictly limited within the safety boundary of the DC system and is only output when the actual oscillation amplitude is large enough.

[0106] C3. Command Sending: Step C3 sends the subsynchronous oscillation suppression command ΔP_order to the DC control and protection system in real time through the high-speed communication channel.

[0107] C3.1 Communication Interface and Protocol: Fiber optic communication is used to ensure low latency and high reliability. The communication protocol follows DC control and protection system standards (such as IEC61850 or proprietary protocols), and the data format includes timestamps, command values, checksums, etc.

[0108] C3.2 Superposition method: At the power reference value input terminal of the DC system, the subsynchronous oscillation suppression command ΔP_order is algebraically added to the original power reference value P_ref to form a new power reference value P_ref_new=P_ref+ΔP_order.

[0109] For multi-terminal or multi-pole DC, the modulation command of each pole is superimposed on the reference value of the corresponding pole.

[0110] C3.3 Monitoring and Feedback: After sending the subsynchronous oscillation suppression command, monitor the actual power response of the DC system. If an abnormality occurs (such as commutation failure warning, overvoltage, etc.), immediately block the subsequent modulation process and report the alarm. In addition, record the subsynchronous oscillation suppression command and DC response data to the fault recording system for offline analysis.

[0111] It should be noted that this embodiment is only a brief illustrative description of the overall process of a method for suppressing subsynchronous oscillations in a wind farm via a DC system. Detailed descriptions of each step can be found in the relevant content of the foregoing embodiments, and will not be repeated here. It is understood that this application does not impose any limitations on this.

[0112] In summary, the subsynchronous oscillation suppression method for wind farms via DC systems provided in this application mainly relates to the field of wind farm grid connection control technology, and can be applied to scenarios including but not limited to high-voltage DC engineering. The subsynchronous oscillation suppression method for wind farms via DC systems provided in this application can be applied to suppressing the risk of subsynchronous oscillations in large-scale wind farms via DC transmission systems. Compared with other related subsynchronous oscillation suppression technologies, the subsynchronous oscillation suppression method provided in this application has the following advantages: Firstly, unlike the traditional model where the grid side and power supply side are independently managed and their data is fragmented, this application breaks down the data silos between the grid-side DC and the power supply side DC. By synchronously collecting electrical data from the grid-side DC and the power supply side wind farm, it enables real-time monitoring and collection of the wind farm and DC operating status. It can start responding at the beginning of the subsynchronous oscillation, thus avoiding the continuation and amplification of oscillation risks. Secondly, this application has a wider range of suppressing subsynchronous oscillation characteristic frequencies. It is not limited to a single frequency, but rather by performing subsynchronous oscillation frequency scanning processing on the original instantaneous value data of the wind farm grid connection point. This allows for the identification and suppression of multiple subsynchronous oscillation frequencies over a wider range, making it suitable for multi-frequency oscillation hazards under complex operating conditions. Third, this application adds a modulation feasibility analysis step before the suppression strategy is implemented, and generates boundary constraint structured data based on the system operating status, avoiding problems such as system overload and equipment damage caused by blindly implementing suppression strategies in traditional methods, thereby improving the oscillation suppression effect and system operation safety. Fourth, the DC power modulation quantity generated in this application is achieved by integrating the target dominant oscillation characteristic quantity, boundary constraint structured data and grid connection point electrical feedback signal to realize multi-dimensional collaborative modulation. Compared with the traditional method of generating modulation quantity based on a single basis, it greatly improves the accuracy and dynamic adaptability of the modulation quantity, ensuring that the suppression command fits the current operating condition requirements.

[0113] Please see Figure 3 This application also provides a subsynchronous oscillation suppression device 300 for a wind farm via a DC system, which can implement the above-mentioned method. The device includes the following modules: The raw instantaneous value data acquisition module 301 is used to acquire the raw instantaneous value data of the current wind farm grid connection point; wherein, the raw instantaneous value data includes the instantaneous values ​​of three-phase voltage and three-phase current; The subsynchronous oscillation frequency scanning module 302 is used to perform subsynchronous oscillation frequency scanning processing on the original instantaneous value data to obtain the target dominant oscillation characteristic quantity; The suppression strategy input condition judgment module 303 is used to obtain the system operating status corresponding to the current wind farm operating condition, and determine whether the current wind farm operating condition meets the suppression strategy input condition based on the system operating status and the target dominant oscillation characteristic quantity; wherein, the system operating status includes the wind farm operating status and the DC system operating status; The modulation feasibility analysis module 304 is used to perform a modulation feasibility analysis on the current wind farm operating conditions based on the system operating status if it is determined that the current wind farm operating conditions meet the conditions for the suppression strategy to be implemented, and to obtain boundary constraint structured data. The DC power modulation generation module 305 is used to generate the original DC power modulation based on the target dominant oscillation characteristic, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point. The subsynchronous oscillation suppression command generation module 306 is used to limit and verify the original DC power modulation amount, generate a subsynchronous oscillation suppression command, and send the subsynchronous oscillation suppression command to the DC system so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command.

[0114] It is understood that the content of the above method embodiments is applicable to the present device embodiments. The specific functions implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0115] This application also provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described method. This electronic device can be any smart terminal, including tablet computers, in-vehicle computers, etc.

[0116] It is understood that the content of the above method embodiments is applicable to this device embodiment. The specific functions implemented by this device embodiment are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0117] Please see Figure 4 , Figure 4 The hardware structure of an electronic device according to another embodiment is illustrated. The electronic device includes: The processor 401 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this application. The memory 402 can be implemented as a read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory 402 can store the operating system and other applications. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 402 and is called and executed by the processor 401 using the methods described above in the embodiments of this application. Input / output interface 403 is used to implement information input and output; The communication interface 404 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, Ethernet cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.). Bus 405 transmits information between various components of the device (e.g., processor 401, memory 402, input / output interface 403, and communication interface 404); The processor 401, memory 402, input / output interface 403 and communication interface 404 are connected to each other within the device via bus 405.

[0118] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method.

[0119] It is understood that the content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0120] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0121] It is understood that the content of the above method embodiments is applicable to the embodiments of this program product. The specific functions implemented by the embodiments of this program product are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0122] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0123] This application provides a method and related equipment for suppressing subsynchronous oscillations in a wind farm's DC system. By scanning the original instantaneous data for subsynchronous oscillation frequencies, it can accurately capture all potential subsynchronous oscillation frequencies and amplitudes under the current wind farm operating conditions and screen out the dominant oscillation characteristic quantities. This allows the application to go beyond single-frequency suppression, identifying multiple subsynchronous oscillation components over a wider frequency range, effectively expanding the coverage and suppression range of subsynchronous oscillation characteristic frequencies. By simultaneously collecting DC data from the grid side and wind farm electrical data from the power source side, and monitoring the wind farm and DC operating status in real time, it can respond at the onset of subsynchronous oscillations, avoiding the continuation and amplification of oscillation risks. Furthermore, by combining the wind farm and... By combining the DC operating status with the target dominant oscillation characteristic quantity, it is possible to accurately determine the conditions for the implementation of suppression strategies, enabling precise triggering and on-demand implementation of suppression strategies. By performing modulation feasibility analysis on the current wind farm operating conditions to obtain structured boundary constraint data, it is possible to ensure that subsequent modulation operations are always carried out within the system's safe operating boundaries, thereby improving system operational safety. By combining the dominant oscillation characteristics, system constraints, and real-time electrical feedback, it is possible to accurately generate DC power modulation quantities adapted to the current wind farm operating conditions. Finally, by limiting the modulation quantity and performing safety verification to generate suppression commands and issuing them for execution, it is possible to ensure that the suppression commands are safe and reliable, do not exceed the limits, and can quickly act on the DC system to suppress subsynchronous oscillations in a timely manner, thereby improving the subsynchronous oscillation suppression effect.

[0124] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0125] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0126] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0127] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0128] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0129] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0130] 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 the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0131] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0132] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0133] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes multiple instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing programs, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0134] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A method for subsynchronous oscillation suppression of a wind farm DC system, characterized in that, The method includes the following steps: Obtain the raw instantaneous value data of the current wind farm grid connection point; wherein, the raw instantaneous value data includes the instantaneous values ​​of three-phase voltage and three-phase current; The original instantaneous value data is subjected to subsynchronous oscillation frequency scanning processing to obtain the target dominant oscillation characteristic quantity; The system operating status corresponding to the current wind farm operating condition is obtained, and based on the system operating status and the target dominant oscillation characteristic quantity, it is determined whether the current wind farm operating condition meets the conditions for implementing the suppression strategy; wherein, the system operating status includes the wind farm operating status and the DC system operating status; If it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, then a modulation feasibility analysis is performed on the current wind farm operating conditions based on the system operating status to obtain boundary constraint structured data. Based on the target dominant oscillation characteristic, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point, the original DC power modulation quantity is generated; The original DC power modulation amount is limited and safety verified to generate a subsynchronous oscillation suppression command. The subsynchronous oscillation suppression command is then sent to the DC system so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command.

2. The method of claim 1, wherein, The subsynchronous oscillation frequency scanning process performed on the original instantaneous value data to obtain the target dominant oscillation characteristic quantity includes: The original instantaneous data is subjected to mode transformation to obtain electrical components; The electrical components are bandpass filtered to obtain the subsynchronous frequency band residual signal; A dynamic data window corresponding to the subsynchronous band residual signal is constructed, and the subsynchronous band residual signal within the current data window is fitted online and subjected to spectrum analysis to obtain the original dominant oscillation characteristic quantity; wherein, the original dominant oscillation characteristic quantity includes the original dominant oscillation frequency and the original dominant oscillation amplitude; The original dominant oscillation feature is subjected to a credibility verification, and the original dominant oscillation feature that passes the credibility verification is subjected to event locking processing to generate the target dominant oscillation feature; wherein, the target dominant oscillation feature includes the target dominant oscillation frequency and the target dominant oscillation amplitude.

3. The method of claim 1, wherein, If it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, then a modulation feasibility analysis is performed on the current wind farm operating conditions based on the system operating status to obtain boundary constraint structured data, including: When it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, a suppression enable flag is generated; Based on the DC system operating state in the system operating state, calculate the DC modulation margin corresponding to the current wind farm operating condition; Based on the suppression enable flag, the DC modulation margin, and the current DC power in the DC system operating state, the boundary constraint structured data is constructed.

4. The method of claim 1, wherein, The electrical feedback signal includes the original frequency deviation signal. The generation of the original DC power modulation quantity based on the target dominant oscillation characteristic, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point includes: The original frequency deviation signal is bandpass filtered to obtain the subsynchronous frequency band component; Based on the target dominant oscillation frequency in the target dominant oscillation characteristic quantity, phase compensation is performed on the subsynchronous frequency band component to obtain the subsynchronous frequency band signal. Based on the target dominant oscillation amplitude in the target dominant oscillation characteristic quantity and the current DC power in the boundary constraint structured data, a dynamic gain coefficient is calculated, and an adaptive gain adjustment is performed on the subsynchronous frequency band signal based on the dynamic gain coefficient to generate the original DC power modulation amount.

5. The method according to claim 1, characterized in that, The process of limiting and verifying the original DC power modulation, generating a subsynchronous oscillation suppression command, and sending the subsynchronous oscillation suppression command to the DC system, so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command, includes: The original DC power modulation amount is limited according to the preset absolute limiting value to obtain the limited DC power modulation amount. Based on the DC modulation margin in the boundary constraint structured data, the limiting DC power modulation amount is subjected to margin verification processing to generate the target DC power modulation amount. Based on the target DC power modulation amount, the subsynchronous oscillation suppression command is generated and sent to the DC system; In the power reference value input terminal of the DC system, the target DC power modulation amount in the subsynchronous oscillation suppression command is algebraically added to the original power reference value in the power reference value input terminal to obtain the target power reference value, so as to perform subsynchronous oscillation suppression on the current wind farm according to the target power reference value.

6. The method according to claim 1, characterized in that, After sending the subsynchronous oscillation suppression command to the DC system, the method further includes: Dynamically monitor the current DC power response data of the DC system; When it is determined that the current DC power response data is abnormal, the DC power modulation for the next cycle is stopped, the current alarm information is generated and reported to the target host system, and the subsynchronous oscillation suppression command and the current DC power response data are recorded in the fault recording system.

7. A device for subsynchronous oscillation damping of a wind farm dc system, characterized in that The device includes the following modules: The raw instantaneous value data acquisition module is used to acquire the raw instantaneous value data of the current wind farm grid connection point; wherein, the raw instantaneous value data includes the instantaneous values ​​of three-phase voltage and three-phase current; The subsynchronous oscillation frequency scanning module is used to perform subsynchronous oscillation frequency scanning processing on the original instantaneous value data to obtain the target dominant oscillation characteristic quantity; The suppression strategy implementation condition judgment module is used to obtain the system operating status corresponding to the current wind farm operating condition, and determine whether the current wind farm operating condition meets the suppression strategy implementation condition based on the system operating status and the target dominant oscillation characteristic quantity; wherein, the system operating status includes the wind farm operating status and the DC system operating status; The modulation feasibility analysis module is used to perform a modulation feasibility analysis on the current wind farm operating conditions based on the system operating status if it is determined that the current wind farm operating conditions meet the conditions for implementing the suppression strategy, and to obtain boundary constraint structured data. The DC power modulation generation module is used to generate the original DC power modulation based on the target dominant oscillation characteristic, the boundary constraint structured data, and the electrical feedback signal of the current wind farm grid connection point. The subsynchronous oscillation suppression command generation module is used to limit and verify the original DC power modulation amount, generate a subsynchronous oscillation suppression command, and send the subsynchronous oscillation suppression command to the DC system so that the DC system can suppress the subsynchronous oscillation of the current wind farm based on the subsynchronous oscillation suppression command.

8. An electronic device, comprising: The electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method according to any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 8. When the computer program is executed by a processor, it implements the method of any one of claims 1 to 6.

10. A computer program product comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 6.

Images