A method, device, equipment and medium for suppressing broadband oscillation of an MMC converter station

Abstract

This invention relates to the field of oscillation suppression technology, and particularly to a method, apparatus, equipment, and medium for broadband oscillation suppression in MMC converter stations. The invention obtains the time-domain components of the voltage response and current disturbance of the MMC converter station to determine the equivalent impedance frequency characteristic curve and short-circuit ratio; based on the voltage response time-domain components, it determines the oscillation voltage amplitude, oscillation energy proportion, and the frequency band of the disturbance; using the oscillation energy proportion and the short-circuit ratio of the MMC converter station, it determines the admittance magnitude; based on the equivalent impedance frequency characteristic curve and the original impedance phase angle, it determines the admittance phase angle; based on the admittance magnitude, oscillation voltage amplitude, and admittance phase angle, it determines the total damping current and the corrected d-axis current control command and q-axis current control command of the MMC converter station, and controls the MMC converter station to achieve precise broadband oscillation suppression in the presence of multiple frequency band oscillations. This results in good operating condition adaptability and improved operating efficiency of the MMC converter station.

Description

Technical Field

[0001] This invention relates to the field of oscillation suppression technology, and in particular to a method, apparatus, equipment and medium for broadband oscillation suppression in MMC converter stations. Background Technology

[0002] The existing method for oscillation suppression in Modular Multilevel Converter (MMC) converter stations involves installing a pre-designed virtual impedance controller with fixed parameters in the MMC converter station control system. Before commissioning, this method involves determining the grid parameters under rated operating conditions, calculating the virtual impedance amplitude and phase angle for each frequency band through offline simulation, and then inputting these parameters into the controller. During MMC operation, the controller continuously outputs the virtual impedance with fixed parameters, providing additional damping at specific frequency bands to suppress oscillations. While this method achieves some oscillation suppression under relatively stable grid conditions, it fails to suppress severe oscillations in weak grid conditions due to insufficient damping when the equivalent short-circuit ratio changes significantly. Conversely, excessively large parameters may lead to over-damping in strong grid conditions, consuming the converter station's reactive power capacity. Furthermore, fixed-parameter virtual impedance controllers are typically designed for only a specific frequency band, limiting their application scope and resulting in poor oscillation suppression performance. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a broadband oscillation suppression method, apparatus, equipment and medium for MMC converter stations, in order to solve the technical problems of poor virtual impedance suppression effect and limited application range in existing oscillation suppression methods.

[0004] Firstly, a method for suppressing broadband oscillations in an MMC converter station is provided, the method comprising:

[0005] Step 100: Obtain the rated voltage, rated power, voltage response time-domain component, and current disturbance time-domain component of the MMC converter station at the current moment; obtain the original impedance phase angle and the original equivalent admittance at the center frequency of the M sub-bands of the MMC converter station at the previous moment; the current control loop on the AC side of the MMC converter station at the current moment contains a broadband disturbance signal, which covers N frequency points, and divides the N frequency points into M sub-bands, where N is a positive integer greater than 1, M is a positive integer greater than 1, and N is greater than or equal to M;

[0006] Step 200: Based on the voltage response time-domain component, the current disturbance time-domain component, the rated voltage, the rated power, and the preset rated frequency of the MMC converter station, determine the equivalent impedance frequency characteristic curve and the short-circuit ratio of the MMC converter station. The equivalent impedance frequency characteristic curve includes the equivalent impedance of the MMC converter station at N frequency points, the equivalent impedance amplitude of the MMC converter station at N frequency points, and the equivalent impedance phase angle of the MMC converter station at N frequency points.

[0007] Step 300: Determine the oscillation voltage amplitude and oscillation energy percentage of the M sub-frequency bands based on the voltage response time-domain component, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands.

[0008] Step 400: First, multiply the preset admittance reference value by the oscillation energy ratio of the m-th sub-frequency band, and then divide it by the short-circuit ratio of the MMC converter station to determine the admittance magnitude value of the m-th sub-frequency band, where m = 1, 2, ..., M;

[0009] Step 500: Determine the admittance phase angle at the center frequency of the M sub-bands at the current moment based on the equivalent impedance frequency characteristic curve, the center frequencies of the M sub-bands, and the original impedance phase angle at the center frequencies of the M sub-bands.

[0010] Step 600: Determine the total damping current of the M sub-frequency bands based on the admittance magnitude of the M sub-frequency bands, the oscillation voltage amplitude of the M sub-frequency bands, the admittance phase angle of the M sub-frequency bands, and the center frequency of the M sub-frequency bands.

[0011] Step 700: Based on the total damping current of the M sub-frequency bands, the preset d-axis current control command, and the preset q-axis current control command, determine the modified d-axis current control command and the modified q-axis current control command of the MMC converter station, and control the MMC converter station according to the modified d-axis current control command and the modified q-axis current control command.

[0012] Secondly, a broadband oscillation suppression device for MMC converter stations is provided, the MMC converter station broadband oscillation suppression device comprising:

[0013] The data acquisition module is used to acquire the rated voltage, rated power, voltage response time-domain component, and current disturbance time-domain component of the MMC converter station at the current moment, and to acquire the original impedance phase angle and the original equivalent admittance at the center frequency of the M sub-bands of the MMC converter station at the previous moment. The current control loop on the AC side of the MMC converter station at the current moment contains a broadband disturbance signal, which covers N frequency points. The N frequency points are divided into M sub-bands, where N is a positive integer greater than 1, M is a positive integer greater than 1, and N is greater than or equal to M.

[0014] The first calculation module is used to determine the equivalent impedance frequency characteristic curve and the short-circuit ratio of the MMC converter station based on the voltage response time-domain component, the current disturbance time-domain component, the rated voltage, the rated power, and the preset rated frequency of the MMC converter station. The equivalent impedance frequency characteristic curve includes the equivalent impedance of the MMC converter station at N frequency points, the equivalent impedance amplitude of the MMC converter station at N frequency points, and the equivalent impedance phase angle of the MMC converter station at N frequency points.

[0015] The second calculation module is used to determine the oscillation voltage amplitude and the oscillation energy ratio of the M sub-frequency bands based on the voltage response time-domain component, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands.

[0016] The admittance modulus determination module is used to first multiply the preset admittance reference value by the oscillation energy ratio of the m-th sub-frequency band, and then divide it by the short-circuit ratio of the MMC converter station to determine the admittance modulus value of the m-th sub-frequency band, where m = 1, 2, ..., M;

[0017] The admittance phase angle determination module is used to determine the admittance phase angle at the center frequency of the M sub-bands at the current moment based on the equivalent impedance frequency characteristic curve, the center frequencies of the M sub-bands, and the original impedance phase angles at the center frequencies of the M sub-bands.

[0018] The total damping current determination module is used to determine the total damping current of the M sub-frequency bands based on the admittance magnitude values ​​of the M sub-frequency bands, the oscillation voltage amplitudes of the M sub-frequency bands, the admittance phase angles of the M sub-frequency bands, and the center frequencies of the M sub-frequency bands.

[0019] The current control command generation module is used to determine the corrected d-axis current control command and the corrected q-axis current control command of the MMC converter station based on the total damping current of the M sub-frequency bands, the preset d-axis current control command, and the preset q-axis current control command, and to control the MMC converter station according to the corrected d-axis current control command and the corrected q-axis current control command.

[0020] Thirdly, an electronic device is provided, including a processor and a memory, wherein the memory is used to store computer programs; and the processor is used to execute the programs stored in the memory to implement the broadband oscillation suppression method for MMC converter stations described in the first aspect.

[0021] Fourthly, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when the computer program is executed by a processor, it implements the broadband oscillation suppression method for MMC converter stations described in the first aspect.

[0022] The beneficial effects of this invention compared to existing technologies are as follows: By acquiring the voltage response time-domain component, current disturbance time-domain component, rated voltage, and rated power of the MMC converter station at the current moment, the equivalent impedance frequency characteristic curve and short-circuit ratio of the MMC converter station are determined; subsequently, based on the voltage response time-domain component and preset upper and lower frequency thresholds for each sub-frequency band, the oscillation voltage amplitude and oscillation energy proportion of each sub-frequency band are determined, thereby determining the frequency band where the disturbance occurs; using preset admittance reference values, the oscillation energy proportion of each sub-frequency band, and the short-circuit ratio of the MMC converter station, the admittance magnitude of each sub-frequency band is determined; again, based on the equivalent impedance frequency characteristic curve, the center frequency of each sub-frequency band, and the original impedance phase angles of the MMC converter station acquired at the previous moment, the admittance phase angle of each sub-frequency band is determined; based on each The admittance magnitude, oscillation voltage amplitude, admittance phase angle, and center frequency of each sub-band are used to determine the total damping current for each sub-band, preparing for oscillation suppression. Finally, based on the total damping current, preset d-axis current control commands, and preset q-axis current control commands, the corrected d-axis and q-axis current control commands for the MMC converter station are determined. These commands are then used to control the MMC converter station. In the case of multiple frequency band oscillations, precise broadband oscillation suppression is achieved, while avoiding excessive damping that occupies the converter station's reactive power capacity and does not interfere with normal power transmission functions. This demonstrates good adaptability to different operating conditions and improves the operating efficiency of the MMC converter station. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of an application environment for a broadband oscillation suppression method for MMC converter stations provided in Embodiment 1 of the present invention;

[0025] Figure 2 This is a flowchart illustrating a broadband oscillation suppression method for an MMC converter station provided in Embodiment 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the control system application of a broadband oscillation suppression method for MMC converter stations provided in Embodiment 1 of the present invention;

[0027] Figure 4 This is a schematic diagram of the structure of a broadband oscillation suppression device for an MMC converter station provided in Embodiment 8 of the present invention;

[0028] Figure 5 This is a schematic diagram of the structure of an electronic device provided in Embodiment 10 of the present invention. Detailed Implementation

[0029] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] Embodiment 1 of the present invention provides a method for suppressing broadband oscillations in MMC converter stations. This method can be applied to applications such as... Figure 1 In the aforementioned application environment, the MMC converter station communicates with the control system. The control system receives three-phase voltage data collected by voltage transformers and three-phase current data collected by current transformers in the MMC converter station, and outputs drive signals to the MMC converter station. The control system includes, but is not limited to, terminal devices such as handheld computers, desktop computers, laptops, ultra-mobile personal computers (UMPCs), netbooks, cloud terminal devices, and personal digital assistants (PDAs). The MMC converter station is equipped with voltage transformers and current transformers. The voltage transformers collect three-phase voltage data, and the current transformers collect three-phase current data. The MMC converter station also needs to receive drive signals from the control system.

[0031] See Figure 2 This is a flowchart illustrating a broadband oscillation suppression method for MMC converter stations provided in Embodiment 1 of the present invention. The aforementioned broadband oscillation suppression method for MMC converter stations can be applied to... Figure 1 The client in the process connects to the target database via a pre-defined Application Programming Interface (API). When the target database is driven to perform corresponding tasks, corresponding task logs are generated, which can be collected through the API. For example... Figure 2 As shown, the broadband oscillation suppression method for the MMC converter station may include the following steps:

[0032] Step 100: Obtain the rated voltage, rated power, voltage response time-domain component, and current disturbance time-domain component of the MMC converter station at the current moment; obtain the original impedance phase angle and the original equivalent admittance at the center frequency of the M sub-bands of the MMC converter station at the previous moment; the current control loop on the AC side of the MMC converter station at the current moment contains a broadband disturbance signal, which covers N frequency points, and divides the N frequency points into M sub-bands, where N is a positive integer greater than 1, M is a positive integer greater than 1, and N is greater than or equal to M;

[0033] Among them, MMC converter stations refer to stations that include modular multilevel converters (MMC converters). The Multilevel Converter (MMC) converter station employs a three-phase, six-arm topology. Each arm contains an arm inductor and several cascaded sub-modules. These sub-modules typically use a half-bridge or full-bridge structure and are commonly used in high-voltage direct current (HVDC) or flexible direct current (DC) transmission systems. Through the switching control of numerous sub-modules within the MMC, bidirectional energy conversion between AC and DC is achieved. Rated voltage refers to the standard operating voltage of the MMC converter station under normal operating conditions; it is the nominal voltage specified during the design of the MMC converter station. Rated power refers to the maximum power that the MMC converter station can continuously output under normal operating conditions; it is an important parameter for measuring the safe and stable operation capability of the MMC converter station. The voltage response time-domain component is obtained by real-time acquisition of the three-phase AC bus voltage through voltage transformers installed on the MMC converter station bus, converting the acquired three-phase voltage to the dq synchronous rotating coordinate system using a standard Park transform, and extracting the voltage response time-domain component from the voltage dq component. The current disturbance time-domain component refers to the voltage response time-domain component obtained by real-time acquisition of the three-phase AC bus voltage through voltage transformers installed on the MMC converter station bus. The current transformer collects the three-phase current of the AC bus in real time. The collected three-phase current is converted to the dq synchronous rotating coordinate system using the standard Park transform to obtain the dq component of the current. The time-domain component of the current disturbance is extracted from the dq component. The original impedance phase angle is calculated using a small-signal model of the phase-locked loop (PLL) installed in the MMC converter station control system, referring to the patent application text with publication number CN106953350A, entitled "A Small-Signal Modeling Method for PLL in a Dual-Ended MMC-HVDC System". The M original equivalent admittances are... The impedance model obtained by interconnecting the flexible DC system and AC system installed in the MMC converter station control system is referred to in the journal article entitled "Stability Analysis and Control Parameter Tuning of Flexible DC Transmission" published in the March 2017 issue of the Journal of Electrical Engineering, Vol. 32, No. 6. The broadband disturbance signal refers to the disturbance signal with a frequency component distributed over a wide range that is superimposed on the current control loop on the AC side of the MMC converter station. The broadband disturbance signal can originate from disturbances on the AC grid side, disturbances on the DC line side, or disturbances in the internal control loop of the MMC converter station.

[0034] The method for extracting the time-domain component of current disturbance from the current dq component is as follows: A low-pass filter with a cutoff frequency of 1Hz is used to filter the current dq component, and the rotational angular velocity of the dq transform is equal to the rated frequency. The rated frequency steady-state current component is extracted. The difference between the rated frequency steady-state current component and the current dq component is the time-domain component of the current disturbance. This time-domain component of the current disturbance is used to represent the disturbance of broadband disturbance signals in the current. When using a low-pass filter with a cutoff frequency of 1Hz to filter the current dq component, the 0Hz DC component that passes through corresponds to the current at the rated frequency in the three-phase current of the MMC converter station; all components above 1Hz that are filtered out correspond to the oscillating current components in the three-phase current of the MMC converter station that deviate from the rated frequency by more than 1Hz. The 1Hz cutoff frequency effectively preserves all oscillation information while completely filtering out the rated frequency steady-state component.

[0035] Similarly, the method for extracting the voltage response time-domain component from the voltage dq component is as follows: use a low-pass filter with a cutoff frequency of 1Hz to filter the voltage dq component, and the rotational angular velocity of the dq transform is equal to the rated frequency to extract the rated frequency steady-state voltage component. Subtract the rated frequency steady-state voltage component from the voltage dq component, and the difference is the voltage response time-domain component. The voltage response time-domain component is used to reflect the dynamic response of the power grid to broadband disturbance signals.

[0036] For example, a broadband disturbance signal includes a first disturbance signal in a first frequency band, a second disturbance signal in a second frequency band, and a third disturbance signal in a third frequency band, wherein the frequency in the third frequency band is greater than the frequency in the second frequency band, the frequency in the second frequency band is greater than the frequency in the first frequency band, and the first frequency band, the second frequency band, and the third frequency band include N frequency points, where N is a positive integer greater than 1.

[0037] Step 200: Based on the voltage response time-domain component, the current disturbance time-domain component, the rated voltage, the rated power, and the preset rated frequency of the MMC converter station, determine the equivalent impedance frequency characteristic curve and the short-circuit ratio of the MMC converter station. The equivalent impedance frequency characteristic curve includes the equivalent impedance of the MMC converter station at N frequency points, the equivalent impedance amplitude of the MMC converter station at N frequency points, and the equivalent impedance phase angle of the MMC converter station at N frequency points.

[0038] Among them, the rated frequency refers to the fundamental frequency of the AC system designed for the MMC converter station, usually 50Hz or 60Hz, used as the frequency reference in the impedance characteristic curve and to normalize the frequency components in the disturbance signal; the equivalent impedance frequency characteristic curve is a curve describing the change of the equivalent impedance (complex number) of the MMC converter station port with frequency over a wide frequency range (covering N frequency points); the short-circuit ratio is a dimensionless index that measures the strength of the grid's support for the MMC converter station, reflecting the ratio of the short-circuit capacity of the bus at the MMC converter station's connection point to the rated power of the converter station; the equivalent impedance refers to the impedance at a specific frequency (i.e., any frequency point among the N frequency points) of the MMC converter station. The ratio of the voltage response phasor to the current disturbance phasor at the converter station port; the equivalent impedance is a complex number, including a real part (resistive component) and an imaginary part (reactant component), used to fully describe the amplitude-frequency and phase-frequency response characteristics of the MMC converter station at that frequency; the equivalent impedance magnitude refers to the magnitude of the equivalent impedance at a specific frequency, reflecting the total impedance capability of the MMC converter station to current disturbances at that frequency, the larger the magnitude, the greater the voltage response caused by the same current disturbance; the equivalent impedance phase angle refers to the degree of lead (positive angle, inductive) or lag (negative angle, capacitive) of the voltage response relative to the current disturbance, used to judge the impedance characteristics and stability trend of the converter station at that frequency.

[0039] Step 300: Determine the oscillation voltage amplitude and oscillation energy percentage of the M sub-frequency bands based on the voltage response time-domain component, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands.

[0040] Among them, the upper frequency threshold refers to the highest frequency boundary value of each sub-band when dividing the frequency band according to the frequency of the broadband disturbance signal; the lower frequency threshold refers to the lowest frequency boundary value of each sub-band when dividing the frequency band according to the frequency of the broadband disturbance signal; the oscillation voltage amplitude refers to the voltage amplitude corresponding to the time domain component of the voltage response in each sub-band; and the oscillation energy ratio refers to the proportion of oscillation energy in each sub-band to the total energy of the broadband disturbance.

[0041] Step 400: First, multiply the preset admittance reference value by the oscillation energy ratio of the m-th sub-frequency band, and then divide it by the short-circuit ratio of the MMC converter station to determine the admittance magnitude value of the m-th sub-frequency band, where m = 1, 2, ..., M;

[0042] Among them, the admittance reference value is the reference scale that guides the calculation of the admittance modulus value, mapping the influence of the oscillation energy ratio and short-circuit ratio of each sub-frequency band to the actual admittance value; the admittance modulus value refers to the amplitude of the equivalent admittance of the MMC converter station calculated in each sub-frequency band.

[0043] For example, the admittance magnitude |Y| of the m-th sub-band v,m| can be expressed by the formula |Y v,m |=Y base ×η m ÷SCR, where m represents the m-th sub-band, m = 1, 2, ..., M, and M represents the total number of sub-bands; |Y v,m | represents the admittance magnitude of the m-th sub-band, in units of S; Y base Indicates the preset admittance reference value, in units of S; η m The value represents the proportion of oscillation energy in the m-th sub-frequency band, dimensionless; SCR represents the short-circuit ratio of the MMC converter station, dimensionless. When the rated power of the MMC converter station is 3000MW and the rated voltage of the MMC converter station is 500kV, the preset reference admittance is 6S, and 0.3% to 0.5% of the reference admittance is taken as the admittance reference value, that is, 0.018S to 0.03S, preferably 0.02S.

[0044] Step 500: Determine the admittance phase angle at the center frequency of the M sub-bands at the current moment based on the equivalent impedance frequency characteristic curve, the center frequencies of the M sub-bands, and the original impedance phase angle at the center frequencies of the M sub-bands.

[0045] The center frequency refers to the single frequency value of the overall frequency position of the m-th sub-band. It is usually taken as the geometric mean or arithmetic mean of the sub-bands, compressing the broadband characteristics of each sub-band into a representative frequency point, which is used to find the corresponding impedance phase angle from the equivalent impedance frequency characteristic curve. The admittance phase angle refers to the phase angle of the equivalent admittance of the MMC converter station in the m-th sub-band, reflecting the degree of lead or lag of the voltage response of the MMC converter station relative to the current disturbance at the center frequency of the sub-band.

[0046] For example, the admittance phase angle θ at the center frequency of the m-th sub-band at the current time. v,m (f) c,m ,t) can be expressed by the formula θ v,m (f) c,m ,t)=-{[∠Z mmc0 (f) c,m ,t-1)+∠Z grid (f) c,m ,t)]÷2}, where m represents the m-th sub-band, m=1,2,…,M, M represents the total number of sub-bands; t represents the current time; t-1 represents the previous time; f c,m θ represents the center frequency of the m-th sub-band; v,m (f) c,m (t) represents the center frequency f of the m-th sub-band at the current time t. c,m Admittance phase angle at point Z; ∠Z mmc0 (f) c,m(t-1) represents the center frequency f of the m-th sub-band at the previous time t-1. c,m The original impedance phase angle at point Z; ∠Z grid (f) c,m (t) represents the center frequency f of the m-th sub-band at the current time t. c,m The admittance phase angle at that point.

[0047] Step 600: Determine the total damping current of the M sub-frequency bands based on the admittance magnitude of the M sub-frequency bands, the oscillation voltage amplitude of the M sub-frequency bands, the admittance phase angle of the M sub-frequency bands, and the center frequency of the M sub-frequency bands.

[0048] The total damping current refers to the total current that the MMC converter station needs to output to suppress voltage oscillations in each sub-frequency band. It comprehensively considers the influence of the admittance magnitude, oscillation voltage amplitude, admittance phase angle, and center frequency of each sub-frequency band, and is used to generate damping control commands. Because the damping currents of each sub-frequency band are independent, multi-band coordinated suppression can be achieved through linear superposition. The oscillation modes of different sub-frequency bands can be suppressed simultaneously at the same time without time-division processing.

[0049] Step 700: Based on the total damping current of the M sub-frequency bands, the preset d-axis current control command, and the preset q-axis current control command, determine the modified d-axis current control command and the modified q-axis current control command of the MMC converter station, and control the MMC converter station according to the modified d-axis current control command and the modified q-axis current control command.

[0050] Among them, the d-axis current control command refers to the original active current reference value calculated by the outer loop active power controller based on the system reference values ​​(such as rated active power and AC bus voltage command) of the MMC converter station, in A; the q-axis current control command refers to the original reactive current reference value calculated by the outer loop reactive power controller based on the system reference values ​​(such as reactive power and AC bus voltage command) of the MMC converter station, in A; the corrected d-axis current control command refers to the current command finally sent to the d-axis PI controller after superimposing the original d-axis current control command with the d-axis damped current component calculated from the total damped current; the corrected q-axis current control command refers to the current command finally sent to the q-axis PI controller after superimposing the original q-axis current control command with the q-axis damped current component calculated from the total damped current.

[0051] For example, first perform a dq transformation on the total damping current of the M sub-bands to obtain the d-axis total damping current i of the MMC converter station. d,damp The total damped current i along the q-axis of the MMC converter station q,damp The revised d-axis current control command i for the MMC converter stationd,new This can be expressed by the formula i d,new =i d,ref +i d,damp , where i d,new This represents the corrected d-axis current control command for the MMC converter station, in A; i d,ref This indicates the preset d-axis current control command, in amperes (A); i d,damp This represents the total d-axis damping current of the MMC converter station, in amperes (A). The modified q-axis current control command i for the MMC converter station... q,new This can be expressed by the formula i q,new =i q,ref +i q,damp , where i q,new This represents the modified q-axis current control command for the MMC converter station, in amperes (A); i q,ref This indicates the preset q-axis current control command, in amperes (A); i q,damp This represents the total damping current along the q-axis of the MMC converter station, expressed in amperes (A).

[0052] like Figure 4 As shown, the control system of the MMC converter station adopts dual closed-loop vector control in the dq coordinate system. The control system includes an outer loop active power controller, an inner loop active power controller, a d-axis PI current controller, and a q-axis PI current controller. The wideband disturbance signal is injected after the outer loop active power controller and before the d-axis PI current controller. The total damping current is injected before the d-axis PI current controller and the q-axis PI current controller of the MMC converter station. Finally, by superimposing the total damping current of the d-axis of the MMC converter station with the preset d-axis current control command, and superimposing the total damping current of the q-axis of the MMC converter station with the preset q-axis current control command, the drive signal of the MMC converter station is output, thereby controlling the MMC converter station to achieve wideband disturbance suppression.

[0053] The broadband oscillation suppression method for MMC converter stations in this embodiment determines the equivalent impedance frequency characteristic curve and short-circuit ratio of the MMC converter station by using the voltage response time-domain component, current disturbance time-domain component, rated voltage, and rated power acquired at the current moment. Then, based on the voltage response time-domain component and preset upper and lower frequency thresholds for each sub-frequency band, the oscillation voltage amplitude and oscillation energy proportion of each sub-frequency band are determined. Finally, using preset admittance reference values, the oscillation energy proportion of each sub-frequency band, and the short-circuit ratio of the MMC converter station, the admittance magnitude of each sub-frequency band is determined. Based on the equivalent impedance frequency characteristic curve, the center frequency of each sub-band, and the original impedance phase angles of the MMC converter station obtained at the previous moment, the admittance phase angle of each sub-band is determined. Based on the admittance magnitude, oscillation voltage amplitude, admittance phase angle, and center frequency of each sub-band, the total damping current of each sub-band is determined. Finally, based on the total damping current, the preset d-axis current control command, and the preset q-axis current control command, the corrected d-axis current control command and the corrected q-axis current control command of the MMC converter station are determined, thereby achieving control of the MMC converter station. Compared with existing technologies, this invention achieves precise broadband oscillation suppression in the case of multiple frequency band oscillations coexisting in the MMC converter station, while avoiding excessive damping that occupies the reactive power capacity of the converter station and not interfering with normal power transmission functions. It has good adaptability to operating conditions and improves the operating efficiency of the MMC converter station.

[0054] In Embodiment 2, step 200 includes:

[0055] Step 201: Convert the voltage response time-domain component into voltage response frequency-domain values ​​at N frequency points, and convert the current disturbance time-domain component into current disturbance frequency-domain values ​​at N frequency points.

[0056] Among them, the voltage response frequency domain value refers to the complex frequency domain representation obtained by Fourier transform (or other frequency domain transformation) of the voltage response time domain component at each frequency point; the current disturbance frequency domain value refers to the complex frequency domain representation obtained by Fourier transform (or other frequency domain transformation) of the current disturbance time domain component at each frequency point.

[0057] Step 202: Divide the voltage response frequency domain value at the nth frequency point by the current disturbance frequency domain value at the nth frequency point to determine the equivalent impedance of the MMC converter station at the nth frequency point and the equivalent impedance frequency characteristic curve of the MMC converter station, n=1, 2, ..., N;

[0058] The equivalent impedance refers to the complex ratio obtained by dividing the voltage response frequency domain value by the current disturbance frequency domain value at each frequency point, reflecting the resistance characteristics of the MMC converter station port to current disturbances at that frequency.

[0059] For example, the equivalent impedance Z of the MMC converter station at the nth frequency point. gird (f) n Z can be expressed by the formula. gird (f) n )=Δu p (f) n )÷Δi p (f) n ), where f n Z represents the nth frequency point, where n = 1, 2, ..., N, and N represents the total number of frequency points, in Hz; gird (f) n () indicates that the MMC converter station is at the nth frequency point f n The equivalent impedance at the point is expressed in Ω; Δu p (f) n () indicates that the MMC converter station is at the nth frequency point f n The voltage response frequency domain value at Δi, in V; p (f) n () indicates that the MMC converter station is at the nth frequency point f n The frequency domain value of the current disturbance at the specified location, in amperes (A).

[0060] Step 203: Based on the equivalent impedance frequency characteristic curve, determine the equivalent impedance amplitude and the equivalent impedance phase angle at N frequency points.

[0061] The equivalent impedance magnitude refers to the magnitude of the equivalent impedance of the MMC converter station at each frequency point; the equivalent impedance phase angle refers to the phase angle of the equivalent impedance of the MMC converter station at each frequency point, i.e., the phase difference between current and voltage. For example, the equivalent impedance phase angle ∠Z of the MMC converter station at the nth frequency point. gird (f) n This can be expressed by the formula ∠Z. gird (f) n )=∠Δu p (f) n )-∠Δi p (f) n ), where f n This represents the nth frequency point, where n = 1, 2, ..., N, and N represents the total number of frequency points, in Hz; ∠Z gird (f) n () indicates that the MMC converter station is at the nth frequency point f n The equivalent impedance phase angle at the point is expressed in degrees or rad; ∠Δu p (f) n () indicates that the MMC converter station is at the nth frequency point f n The phase of the voltage response in the frequency domain at a given point, in degrees or rad; ∠Δip (f) n () indicates that the MMC converter station is at the nth frequency point f n The phase of the current disturbance in the frequency domain, expressed in degrees or rad.

[0062] Step 204: Determine the equivalent impedance magnitude at the rated frequency based on the equivalent impedance frequency characteristic curve and the rated frequency.

[0063] The equivalent impedance magnitude refers to the amplitude of the equivalent impedance of the MMC converter station at its rated frequency, which is the ratio of the magnitude of the voltage response in the frequency domain to the magnitude of the current disturbance in the frequency domain at the rated frequency. For example, the equivalent impedance magnitude |Z of the MMC converter station at its rated frequency. gird (f0) can be expressed by the formula |Z gird (f0)|=|Δu p (f0)|÷|Δi p (f0)|, where f0 represents the rated frequency of the MMC converter station in Hz; |Z gird (f0) represents the equivalent impedance magnitude of the MMC converter station at the rated frequency f0, in Ω; |Δu p (f0) represents the magnitude of the voltage response in the frequency domain at the rated frequency f0 of the MMC converter station, in V or kV; |Δi p (f0) represents the magnitude of the current disturbance frequency domain value at the rated frequency f0 of the MMC converter station, in A or kA.

[0064] Step 205: Squaring the rated voltage and dividing it by the equivalent impedance modulus at the rated frequency and the rated power, determines the short-circuit ratio at the rated frequency.

[0065] The short-circuit ratio refers to the voltage support strength of the AC system for the MMC converter station. The larger the short-circuit ratio, the stronger the operating capability of the MMC converter station (i.e., the smaller the equivalent impedance). Even if the MMC converter station operates at full power, the impact on the AC bus voltage is very small, and the system operates stably. The smaller the short-circuit ratio, the weaker the operating capability of the MMC converter station (i.e., the larger the equivalent impedance). Power fluctuations of the MMC converter station will significantly cause voltage fluctuations, which can easily lead to oscillations or instability.

[0066] For example, the short-circuit ratio SCR(f0) of an MMC converter station at its rated frequency can be expressed by the formula: SCR(f0) = (U N ) 2 ÷[|Z gird (f0)|×(P) N ) 2], where f0 represents the rated frequency of the MMC converter station, in Hz; SCR(f0) represents the short-circuit ratio of the MMC converter station at the rated frequency f0, dimensionless; U N This indicates the rated voltage of the MMC converter station, in units of V or kV; |Z gird (f0) represents the equivalent impedance magnitude of the MMC converter station at the rated frequency f0, in Ω; P N This indicates the rated power of the MMC converter station, expressed in W or MW. Therefore, a larger equivalent impedance modulus at the rated frequency results in a smaller short-circuit ratio, poorer operational capability, and a higher risk of oscillation between the MMC converter station and the power grid. Conversely, a smaller equivalent impedance modulus at the rated frequency results in a larger short-circuit ratio, stronger operational capability, and minimal impact on the AC bus voltage even when operating at full power.

[0067] The broadband oscillation suppression method for MMC converter stations in this embodiment converts the time-domain components of voltage response and current disturbance into frequency-domain values ​​of voltage response and current disturbance at various frequency points, thereby determining the equivalent impedance frequency characteristic curve of the MMC converter and the equivalent impedance of the MMC converter station at each frequency point. Subsequently, based on the equivalent impedance frequency characteristic curve, the equivalent impedance amplitude and equivalent impedance phase angle at each frequency point are determined. Next, using the equivalent impedance frequency characteristic curve and the rated frequency of the MMC converter station, the equivalent impedance magnitude of the MMC converter station at the rated frequency is determined. Finally, based on the rated voltage and rated power of the MMC converter station and the equivalent impedance magnitude of the MMC converter station at the rated frequency, the short-circuit ratio of the MMC converter station at the rated frequency is determined. Compared with existing technologies, this invention calculates the equivalent impedance of the MMC converter station at various frequency points, determines the equivalent impedance frequency characteristic curve, and uses the rated voltage, rated power, and rated frequency of the MMC converter station to determine the short-circuit ratio of the MMC converter station at the rated frequency. This accurately assesses the AC grid strength at the connection point of the MMC converter station, provides a data basis for the early warning and suppression of broadband oscillations, and ensures the stable operation of the MMC converter station under complex grid conditions.

[0068] In Embodiment 3, after step 500 and before step 600, the following is also included:

[0069] Step 801: Determine the virtual admittance at the center frequency of the M sub-bands based on the admittance magnitude values ​​of the M sub-bands and the admittance phase angle at the center frequency of the M sub-bands;

[0070] Virtual admittance refers to an equivalent admittance value with a clear physical meaning, constructed in reverse using the admittance magnitude and admittance phase angle to achieve broadband oscillation suppression. For example, the virtual admittance Y at the center frequency of the m-th sub-band. v,m It can be expressed by the formula Y v,m =|Y v,m |×exp[j×θ v,m (f) c,m ], where m represents the m-th sub-band, m = 1, 2, ..., M, and M represents the total number of sub-bands; Y v,m |Y represents the virtual admittance at the center frequency of the m-th sub-band, in units of S; v,m | represents the admittance magnitude of the m-th sub-band, in units of S; exp(·) represents the exponential function, exp(x) = e x e≈2.72; j represents the imaginary unit, satisfying j 2 =-1, dimensionless; f c,m θ represents the center frequency of the m-th sub-band, in Hz; v,m (f) c,m () represents the center frequency f of the m-th sub-band. c,m The admittance phase angle at the point, in degrees or rad.

[0071] Step 802: Based on the original equivalent admittance at the center frequency of the M sub-bands, the virtual admittance at the center frequency of the M sub-bands, the equivalent impedance at the N frequency points, and the admittance magnitude of the M sub-bands, determine the first corrected admittance magnitude of the M sub-bands at the current time.

[0072] The first corrected admittance magnitude refers to a more accurate estimate of the admittance magnitude obtained by first correcting the original admittance magnitude after using the mathematical relationship between the virtual admittance, the original equivalent admittance, the equivalent impedance and the original admittance magnitude in the same frequency band to eliminate or reduce the calculation error of the admittance magnitude caused by frequency aliasing, noise and other factors in the original measurement.

[0073] The broadband oscillation suppression method for MMC converter stations in this embodiment determines the virtual admittance at the center frequency of each sub-frequency band by using the admittance magnitude and admittance phase angle at the center frequency of each sub-frequency band. Finally, using the initially acquired original equivalent admittance of the MMC converter station, the virtual admittance at the center frequency of each sub-frequency band, the admittance magnitude of each sub-frequency band, and the equivalent impedance at each frequency point, the first corrected admittance magnitude of each sub-frequency band is determined. Compared with the prior art, this invention introduces the virtual admittance at the center frequency of each sub-frequency band for multiple data verification, ensuring the impedance-admittance physical consistency between electrical quantities in each sub-frequency band, enhancing the robustness of the oscillation suppression strategy under weak grid or harmonic distortion conditions, significantly reducing the false trigger rate in broadband oscillation suppression, and improving the dynamic response speed of the MMC converter station.

[0074] In Embodiment 4, step 802 includes:

[0075] Step 8021: Summing the original equivalent admittance at the center frequency of the m-th sub-band and the virtual admittance of the m-th sub-band, and taking the reciprocal, to determine the equivalent impedance after superimposing the virtual admittance at the center frequency of the m-th sub-band;

[0076] The equivalent impedance after superimposing the virtual admittance refers to the equivalent complex impedance value calculated by superimposing the original measured or calculated equivalent admittance of the MMC converter station when it is not affected by oscillations with the virtual admittance constructed in reverse to achieve oscillation suppression.

[0077] For example, the equivalent impedance Z after superimposed virtual admittance at the center frequency of the m-th sub-band. mmc,new (f) c,m Z can be expressed by the formula. mmc,new (f) c,m ) = 1 ÷ [Y mmc0 (f) c,m )+Y v,m ], where m represents the m-th sub-band, m = 1, 2, ..., M, and M represents the total number of sub-bands; f c,m Z represents the center frequency of the m-th sub-band, in Hz; mmc,new (f) c,m () represents the center frequency f of the m-th sub-band. c,m The equivalent impedance after superimposed virtual admittance at Y, in Ω; mmc0 (f) c,m () represents the center frequency f of the m-th sub-band. c,m The original equivalent admittance at Y is expressed in units of S; v,m f represents the center frequency of the m-th sub-band. c,m The virtual admittance at the given point is expressed in s (s).

[0078] Step 8022: Determine the equivalent impedance at the center frequency of the M sub-bands based on the equivalent impedance of the N frequency points.

[0079] Step 8023: Divide the equivalent impedance after superimposed virtual admittance at the center frequency of the m-th sub-band by the equivalent impedance at the center frequency of the m-th sub-band to determine the impedance ratio at the center frequency of the m-th sub-band.

[0080] Impedance ratio, at the center frequency of the same sub-band, refers to the ratio between the equivalent impedance of the MMC converter station after adding virtual admittance and its own equivalent impedance when unaffected by oscillations. It reflects the degree to which the introduction of virtual admittance changes the impedance characteristics of the original MMC converter station and is a key dimensionless indicator for judging whether broadband oscillations are effectively suppressed. For example, the impedance ratio L(f) at the center frequency of the m-th sub-band... c,m ) can be expressed by the formula L(f) c,m =Z mmc,new (f) c,m )÷Z grid (f) c,m ), where m represents the m-th sub-band, m = 1, 2, ..., M, and M represents the total number of sub-bands; f c,m L(f) represents the center frequency of the m-th sub-band, in Hz; c,m () represents the center frequency f of the m-th sub-band. c,m The impedance ratio at Z is dimensionless; mmc,new (f) c,m () represents the center frequency f of the m-th sub-band. c,m The equivalent impedance after superimposed virtual admittance at Z, in Ω; grid (f) c,m () represents the center frequency f of the m-th sub-band. c,m The equivalent impedance at a given frequency is expressed in Ω. The impedance ratio is a core indicator for judging the stability of the interaction between the MMC converter station and the power grid. According to the Nyquist stability criterion, the system stability requirement is that the phase angle of the impedance ratio at each frequency point does not exceed ±180°.

[0081] Step 8024: Determine the phase angle of the impedance ratio at the center frequency of the M sub-bands based on the impedance ratio at the center frequency of the M sub-bands;

[0082] The phase angle of the impedance ratio refers to the angle of the impedance ratio relative to the positive real axis in the complex plane at the center frequency of the same sub-band. It quantitatively describes the phase difference between the equivalent impedance of the MMC converter station after superimposing virtual admittance and the equivalent impedance of the MMC converter station when it is not affected by oscillation. The phase angle of the impedance ratio is one of the key indicators for judging whether the MMC converter station is experiencing broadband oscillation, and it is directly related to the phase margin and damping characteristics of the MMC converter station. For example, when using the four-quadrant arctangent function to calculate the phase angle of the impedance ratio at the center frequency of M sub-bands, the phase angle ∠L(f) of the impedance ratio at the center frequency of the m-th sub-band is... c,m ) can be expressed by the formula ∠L(f c,m =atan2(Im[L(f)) c,m )], Re[L(f c,m )])×(180°÷π), where m represents the m-th sub-band, m=1, 2, …, M, and M represents the total number of sub-bands; f c,m ∠L(f) represents the center frequency of the m-th sub-band, in Hz; c,m () represents the center frequency f of the m-th sub-band. c,m The phase angle of the impedance ratio at the point is in degrees; atan2(·) represents the arctangent function in the four quadrants; L(f c,m () represents the center frequency f of the m-th sub-band. c,m The impedance ratio at the point is dimensionless; Im[L(f c,m [)] represents the center frequency f of the m-th sub-band. c,m The real part of the impedance ratio at the point; Re[L(f)] c,m [)] represents the center frequency f of the m-th sub-band. c,m The imaginary part of the impedance ratio at the center frequency. When calculating the phase angle of the impedance ratio at the center frequency of M sub-bands using the four-quadrant arctangent function, the value range is [-180°, 180°]. This can correctly handle the case where the complex number is in each quadrant and avoid quadrant confusion leading to misjudgment of the margin.

[0083] Step 8025: Subtract the absolute value of the phase angle of the impedance ratio at the center frequency of the m-th sub-band from 180° to determine the phase margin of the m-th sub-band.

[0084] Among them, phase margin refers to the remaining phase safety margin of the MMC converter station from the current state to the critical stability boundary (i.e., when the impedance ratio phase angle reaches ±180°) in the stability criterion of broadband oscillation suppression. It quantitatively describes the ability of the MMC converter station to resist phase disturbances and avoid oscillations.

[0085] For example, the phase margin of the m-th sub-band can be expressed by the formula PM. m =180°-|∠L(f c,m)|, where m represents the m-th sub-band, m=1,2,…,M, and M represents the total number of sub-bands; f c,m PM represents the center frequency of the m-th sub-band, in Hz. m L(f) represents the phase margin of the m-th sub-band, in degrees; c,m () represents the center frequency f of the m-th sub-band. c,m The impedance ratio at point L is dimensionless; ∠L(f c,m () represents the center frequency f of the m-th sub-band. c,m The phase angle of the impedance ratio at a given point is expressed in degrees. The larger the phase margin of a sub-band, the more stable that sub-band is; the smaller the phase margin of a sub-band, the closer that sub-band is to the instability boundary.

[0086] Step 8026: Determine the first corrected admittance magnitude values ​​of the M sub-frequency bands based on the admittance magnitude values ​​of the M sub-frequency bands, the phase margin of the M sub-frequency bands, and a preset phase margin threshold.

[0087] Among them, the phase margin threshold refers to the critical value (or critical interval) of the phase margin used to determine whether the MMC converter station meets the stability requirements in the stability criterion for broadband oscillation suppression; the admittance magnitude after the first correction refers to the corrected admittance magnitude calculated by weighting, scaling or mapping functions using the admittance magnitude and phase margin of each sub-band, with the deviation of the phase margin from the preset phase margin threshold as the correction basis.

[0088] For example, the first corrected admittance magnitude value |Y in the m-th sub-band v,m | new This can be expressed by the formula |Y v,m | new =|Y v,m |×[1+(PM min -PM m )÷PM min ], where m represents the m-th sub-band, m = 1, 2, ..., M, and M represents the total number of sub-bands; |Y v,m | new The first corrected admittance magnitude value of the m-th sub-band is expressed in s; |Y v,m | represents the admittance magnitude of the m-th sub-band, in units of S; PM m This represents the phase margin of the m-th sub-band, in degrees (°); PM min This represents the preset phase margin threshold, with a preferred value of 30°, expressed in degrees.

[0089] At the same time, the correction coefficient K = 1 + (PM) min -PM m )÷PM minThe value range is (1, 2], when the phase margin PM of the m-th sub-band m When the phase margin is 0°, the correction factor K is at most 2; when the phase margin of the m-th sub-band is PM m Approaching the preset phase margin threshold PM min When the correction factor K approaches 1; when the phase margin PM of the m-th sub-band... m Equal to the preset phase margin threshold PM min At this time, the admittance magnitude remains at its current value and no correction is performed to prevent the admittance magnitude from becoming zero or negative.

[0090] Therefore, the phase margin PM of the m-th sub-band can be determined. m The smaller the phase margin, the greater the correction magnitude. Insufficient phase margin indicates poor stability of the MMC converter station, requiring an increase in the admittance magnitude to increase damping injection and improve stability. Sufficient phase margin maintains the current parameters to avoid introducing unnecessary control losses. After each correction of the admittance magnitude, the equivalent impedance and impedance ratio of the MMC converter station at the center frequency of each sub-band, as well as the phase margin of each sub-band, need to be recalculated. Iteration continues until the phase margin of all sub-bands is not less than a preset margin threshold, or the number of iterations reaches a preset upper limit (preferred to be 3 iterations). After iteration, the final admittance magnitude and corresponding admittance phase angle after the first correction for each sub-band are output, together forming the virtual admittance of each sub-band. Through a two-stage design of open-loop calculation and closed-loop verification, the parameters of the virtual admittance of each sub-band simultaneously meet two objectives: adaptively allocating damping according to grid strength and oscillation intensity, and ensuring that the phase margin of each sub-band is not lower than the safety threshold. This avoids both insufficient damping leading to a continuous increase in oscillation and improper parameter settings leading to new instability risks.

[0091] The broadband oscillation suppression method for MMC converter stations in this embodiment determines the equivalent impedance after superimposed virtual admittance at the center frequency of each sub-band by using the original equivalent admittance and virtual admittance corresponding to the center frequency of each sub-band; using the equivalent impedance after superimposed virtual admittance and the equivalent impedance at the center frequency of each sub-band, the impedance ratio at the center frequency of each sub-band is determined; then, based on the impedance ratio, the phase angle of the impedance ratio at the center frequency of each sub-band is determined; using the phase angle of the impedance ratio, the phase margin of each sub-band is determined; finally, based on the admittance magnitude and phase margin of each sub-band, as well as a preset phase margin threshold, the first corrected admittance magnitude of each sub-band is determined. Compared to existing technologies, this invention determines the phase margin of each sub-band by calculating the phase angle of the impedance ratio at the center frequency of each sub-band of the MMC converter station, and determines the admittance magnitude after the first correction using the admittance magnitude of each sub-band. It establishes a closed-loop correction mechanism for admittance magnitude, phase margin, and preset phase margin threshold. Through multi-sub-band segmentation processing and four-quadrant phase angle calculation of the MMC converter station, the accuracy of impedance ratio phase angle calculation is significantly improved, margin misjudgment caused by phase quadrant confusion is eliminated, and quantitative assessment and adaptive suppression of broadband oscillation risk are achieved.

[0092] In Embodiment 5, after step 802, the method further includes:

[0093] Based on the admittance magnitude values ​​of the M sub-frequency bands, the first corrected admittance magnitude values ​​of the M sub-frequency bands, and the preset filtering coefficients, the second corrected admittance magnitude values ​​of the M sub-frequency bands are determined.

[0094] The filter coefficient is a preset parameter used in the second correction process to balance the weight ratio between the calculated admittance magnitude (uncorrected calculated value) and the first corrected admittance magnitude, with a value range of [0, 1]. The second corrected admittance magnitude is the final estimated admittance magnitude obtained by weighting and fusing the first corrected admittance magnitude with the calculated admittance magnitude (uncorrected calculated value) according to the preset filter coefficient.

[0095] Because the operating conditions of the receiving-end grid of the MMC converter station are not static, line switching, load changes, and unit output adjustments can all cause changes in equivalent impedance and oscillation characteristics. To ensure the continued effectiveness of broadband oscillation suppression, the entire process needs to be periodically re-executed to update the virtual admittance of each sub-band.

[0096] For example, the second corrected admittance magnitude value |Y in the m-th sub-band v,m | final This can be expressed by the formula |Y v,m | final =α×|Y v,m |new +(1-α)×|Y v,m |, where m represents the m-th sub-band, m = 1, 2, ..., M, and M represents the total number of sub-bands; |Y v,m | final |Y represents the admittance magnitude after the second correction for the m-th sub-band, in units of S; v,m | new The first corrected admittance magnitude value of the m-th sub-band is expressed in s; |Y v,m | represents the admittance magnitude of the m-th sub-frequency band, in units of S; α represents the preset filter coefficient, with a preferred value of 0.3 and a range of [0, 1]. A larger preset filter coefficient results in a greater weight for the first corrected admittance magnitude of the m-th sub-frequency band, leading to faster parameter updates, suitable for scenarios where MMC converter station operating conditions change frequently; a smaller preset filter coefficient results in a smaller weight for the first corrected admittance magnitude of the m-th sub-frequency band, leading to smoother parameter changes, suitable for scenarios where MMC converter station operating conditions are relatively stable. The preferred preset filter coefficient value is 0.3, meaning that each update mixes the old and new parameters in a 3:7 ratio, resulting in a gradual parameter change. This effectively prevents sudden changes in the admittance magnitude from impacting the MMC converter station's current control loop, ensuring control stability.

[0097] Every preset update cycle, the equivalent impedance calculation, energy proportion calculation of each sub-band, virtual admittance calculation of each sub-band, and total damping current generation are all re-executed to update the virtual admittance of each sub-band. For example, the preset update cycle is determined based on the time scale of equivalent impedance change (usually from seconds to minutes) and the computing power of the MMC converter station. The preferred value for the preset update cycle is 5 seconds, meaning that steps 100 to 700 are re-executed every 5 seconds. With a preset update cycle of 5 seconds, for slowly changing MMC converter station operating conditions, such as minute-level load changes, the operating conditions of the MMC converter station can be tracked in a timely manner. For suddenly changing operating conditions, such as line tripping, although the equivalent impedance changes abruptly at the moment of tripping, the oscillation usually takes hundreds of milliseconds to develop from excitation. Within the 5-second update cycle, the oscillation can still be continuously suppressed by the damping current without interrupting the suppression effect. After the next update cycle is completed, the virtual admittance parameters of each sub-band will be automatically adjusted to values ​​that match the new grid conditions.

[0098] The broadband oscillation suppression method for MMC converter stations in this embodiment utilizes preset filtering coefficients to filter the admittance magnitude values ​​of each sub-frequency band and the first-corrected admittance magnitude values ​​of each sub-frequency band, thereby determining the second-corrected admittance magnitude values ​​of each sub-frequency band. Compared to existing technologies, this invention re-executes the entire process calculation every preset update cycle and performs smoothing filtering on the admittance magnitude values, ensuring that the virtual admittance of each sub-frequency band continuously tracks the dynamic changes in the operating conditions of the MMC converter station. This guarantees the long-term effectiveness of broadband oscillation suppression under various operating modes and improves oscillation suppression efficiency.

[0099] In Example 6, step 300 includes:

[0100] Step 301: Determine the oscillation energy of the M sub-frequency bands based on the time-frequency power spectral density of the N frequency points, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands.

[0101] Among them, the upper frequency threshold refers to the upper cutoff frequency of each preset sub-frequency band; the lower frequency threshold refers to the lower cutoff frequency of each preset sub-frequency band; and the oscillation energy refers to the integral of the time-frequency power spectral density with respect to frequency within each preset sub-frequency band, used to characterize the oscillation power intensity of the MMC converter station within each sub-frequency band. For example, the oscillation energy E of the m-th sub-frequency band... m It can be expressed by the formula as follows Where m represents the m-th sub-band; E m This represents the oscillation energy of the m-th sub-band, expressed in V. 2 ;f m,high This represents the preset upper limit threshold for the m-th sub-band, in Hz; f m,low represents the preset lower threshold of the m-th sub-band, in Hz; t represents the current time, in seconds; n represents the n-th frequency point; f n Represents the frequency at the nth frequency point, in Hz; |Δu d (t, f) n )| 2 f represents the nth frequency point at the current time t. n The time-frequency power spectral density at a given location is expressed in V. 2 / Hz. In the m-th sub-band [f m,low f m,high Integrating the time-frequency power spectral density within the sub-band is equivalent to summing the energy contributions of all frequency points within that sub-band, resulting in the oscillation energy E of the m-th sub-band. m This directly reflects the intensity of the oscillation in that sub-band.

[0102] For example, the 2–1000 Hz frequency band is divided into 3 sub-bands, and the f of the first sub-band... 1,low=2Hz、f 1,high =50Hz, the second sub-band's f 2,low =50Hz, f 2,high =100Hz, the third sub-band's f 3,low =100Hz, f 3,high =1000Hz. Taking a tripping scenario as an example, after the trip, the oscillation energy at the 25Hz frequency point is released in a concentrated manner. The oscillation energy E1 of the first sub-band [2Hz, 50Hz] will increase significantly, while the oscillation energy E2 of the second sub-band [50Hz, 100Hz] and the oscillation energy E3 of the third sub-band [100Hz, 1000Hz] will decrease relatively.

[0103] Step 302: Take the square root of the oscillation energy of the M sub-frequency bands to determine the oscillation voltage amplitude of the M sub-frequency bands;

[0104] The oscillation voltage amplitude refers to the equivalent voltage amplitude obtained by converting the oscillation energy of each sub-frequency band. Its physical meaning is the effective voltage value or voltage amplitude of the oscillation signal within that frequency band, used to generate the damping current of each sub-frequency band. For example, the oscillation voltage amplitude u of the m-th sub-frequency band at current time t... osc,m (t) can be expressed by the formula u osc,m (t) = E m （1÷2） Where m represents the m-th sub-band; t represents the current time in seconds; u osc,m (t) represents the oscillation voltage amplitude of the m-th sub-frequency band at the current time t, in V; E m This represents the oscillation energy of the m-th sub-band, expressed in V. 2 .

[0105] Step 303: Divide the oscillation energy of the m-th sub-frequency band by the sum of the oscillation energies of the M sub-frequency bands to determine the oscillation energy percentage of the m-th sub-frequency band, where m = 1, 2, ..., M.

[0106] For example, the proportion of oscillation energy η in the m-th sub-band m This can be expressed by the formula η m =E m ÷ (E1+E2+…+E M ), where m represents the m-th sub-band, m = 1, 2, ..., M, and M represents the total number of sub-bands; η m Let η represent the proportion of oscillation energy in the m-th sub-band, with a value range of [0, 1], and η1 + η2 + ... + η M =1, dimensionless; E m This represents the oscillation energy of the m-th sub-band, expressed in V. 2The oscillation energy of each sub-band can quantify the concentration of oscillation energy distribution in each sub-band and convert it into a normalized allocation weight, so that the sub-band with more concentrated oscillation can obtain more damping force. For example, before the tripping scenario, the energy of the three sub-bands is relatively evenly distributed, η1=0.2, η2=0.3, η3=0.5. After the tripping, the first sub-band oscillates violently, η1 increases to 0.7, η2 decreases to 0.2, and η3 decreases to 0.1. This change in proportion directly drives subsequent steps to allocate more damping force to the first sub-band without manual intervention. When the oscillation frequency of the first sub-band is below 10Hz, due to the limitation of the time window length, the frequency resolution of the short-time Fourier transform within a single window is 10Hz, which is insufficient to accurately locate the specific frequency point. However, the oscillation energy is still completely accumulated in the oscillation energy E1 of the first sub-band, which does not affect the calculation of the proportion of oscillation energy η1 of the first sub-band and the subsequent allocation of damping force. If fine identification of frequencies below 10Hz is required, the analysis time window of the sub-synchronous sub-band can be extended to 0.5s separately.

[0107] By quantizing the oscillation energy distribution of broadband oscillations in each sub-band in real time, the oscillation state is transformed into the oscillation energy ratio of each sub-band that can be directly used for damping force allocation. This avoids applying excessive damping to sub-bands with less severe oscillations and improves the power transmission efficiency of the MMC converter station.

[0108] The broadband oscillation suppression method for MMC converter stations in this embodiment first determines the oscillation energy of each sub-frequency band based on the time-frequency power spectral density at each frequency point, the preset upper frequency threshold of each sub-frequency band, and the preset lower frequency threshold of each sub-frequency band. Then, the square root of the oscillation energy of each sub-frequency band is taken to determine the oscillation voltage amplitude of each sub-frequency band. Finally, the oscillation energy of each sub-frequency band is divided by the sum of the oscillation energies of all sub-frequency bands to determine the proportion of oscillation energy in each sub-frequency band. Compared with existing technologies, this invention quantifies the oscillation energy distribution of broadband oscillations in each sub-frequency band in real time, transforming the oscillation state into the proportion of oscillation energy in each sub-frequency band that can be directly used for damping force allocation. This provides a data foundation for subsequent precise suppression of broadband oscillations, facilitates on-demand suppression of broadband oscillations, and significantly improves oscillation suppression efficiency.

[0109] In Example 7, step 600 includes:

[0110] Step 601: Determine the damping current of the m-th sub-frequency band based on the admittance magnitude of the m-th sub-frequency band, the oscillation voltage amplitude of the m-th sub-frequency band, the admittance phase angle at the center frequency of the m-th sub-frequency band, and the center frequency of the m-th sub-frequency band.

[0111] The damping current refers to the control quantity used to dissipate oscillation energy and suppress oscillation amplitude. When this current is injected into the MMC converter station, it generates damping power opposite to the oscillation direction in the sub-band, thereby achieving active oscillation suppression. For example, the damping current i in the m-th sub-band at current time t... damp,m (t) can be expressed by the formula i damp,m (t) = |Y v,m |×u osc,m (t)×cos[2π×f c,m ×t+θ v,m (f) c,m ], where m represents the m-th sub-band; t represents the current time in seconds; i damp,m (t) represents the damping current of the m-th sub-frequency band at time t, in A; |Y v,m | represents the admittance magnitude of the m-th sub-band, in units of S; u osc,m (t) represents the oscillation voltage amplitude of the m-th sub-frequency band at the current time t, in V; f c,m θ represents the center frequency of the m-th sub-band, in Hz; v,m (f) c,m () represents the center frequency f of the m-th sub-band. c,m The admittance phase angle is expressed in degrees or rad. When an oscillating voltage occurs in a certain sub-frequency band, a damping current synchronized with the oscillation frequency is automatically generated in that sub-frequency band. By adjusting the admittance phase angle, an appropriate phase difference is formed between the damping current and the oscillation voltage, thereby consuming the oscillation energy. The amplitude of the damping current is determined by both the admittance magnitude and the amplitude of the oscillation voltage. The more intense the oscillation, the larger the amplitude of the oscillation voltage, and the larger the amplitude of the generated damping current, forming a natural proportional response mechanism. The admittance phase angle determines the phase relationship between the damping current and the oscillation voltage, ensuring that the damping current is exactly at the optimal phase for consuming the oscillation energy.

[0112] Step 602: Sum the damping currents of the M sub-frequency bands to determine the total damping current of the M sub-frequency bands.

[0113] For example, at the current time t, the total damping current i of the M sub-bands damp,total (t) can be expressed by the formula:

[0114] ,

[0115] Where m represents the m-th sub-frequency band; i damp,total (t) represents the total damping current of the M sub-frequency bands at the current time t, in A; i damp,m(t) represents the damping current of the m-th sub-frequency band at the current time t, in A. The damping currents of each sub-frequency band are independent of each other, and multi-frequency band coordinated suppression is achieved through linear superposition. The oscillation modes of different sub-frequency bands can be suppressed simultaneously at the same time without time-division processing.

[0116] The broadband oscillation suppression method for MMC converter stations in this embodiment utilizes the admittance magnitude and oscillation voltage amplitude of each sub-frequency band, the center frequency of each sub-frequency band, and the admittance phase angle at the center frequency of each sub-frequency band to determine the damping current of each sub-frequency band. Finally, the damping currents of each sub-frequency band are summed to determine the total damping current of the MMC converter station. Compared with the prior art, this invention achieves precise suppression of broadband oscillations by calculating the damping current in each frequency band and then summing them, avoiding the problems of over-suppression or under-suppression of oscillations, and significantly improving the stable operation capability of the MMC converter station.

[0117] In Example 8, as Figure 3 As shown, a broadband oscillation suppression device 40 for an MMC converter station is provided, comprising:

[0118] The data acquisition module 410 is used to acquire the rated voltage, rated power, voltage response time-domain component, and current disturbance time-domain component of the MMC converter station at the current moment, and to acquire the original impedance phase angle and the original equivalent admittance at the center frequency of the M sub-bands of the MMC converter station at the previous moment. The current control loop on the AC side of the MMC converter station at the current moment contains a broadband disturbance signal, which covers N frequency points and divides the N frequency points into M sub-bands, where N is a positive integer greater than 1, M is a positive integer greater than 1, and N is greater than or equal to M.

[0119] The first calculation module 420 is used to determine the equivalent impedance frequency characteristic curve and the short-circuit ratio of the MMC converter station based on the voltage response time-domain component, the current disturbance time-domain component, the rated voltage, the rated power, and the preset rated frequency of the MMC converter station. The equivalent impedance frequency characteristic curve includes the equivalent impedance of the MMC converter station at N frequency points, the equivalent impedance amplitude of the MMC converter station at N frequency points, and the equivalent impedance phase angle of the MMC converter station at N frequency points.

[0120] The second calculation module 430 is used to determine the oscillation voltage amplitude and the oscillation energy ratio of the M sub-frequency bands based on the voltage response time domain component, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands.

[0121] The admittance modulus determination module 440 is used to first multiply the preset admittance reference value by the oscillation energy ratio of the m-th sub-frequency band, and then divide it by the short-circuit ratio of the MMC converter station to determine the admittance modulus value of the m-th sub-frequency band, where m = 1, 2, ..., M;

[0122] The admittance phase angle determination module 450 is used to determine the admittance phase angle at the center frequency of the M sub-bands at the current moment based on the equivalent impedance frequency characteristic curve, the center frequencies of the M sub-bands, and the original impedance phase angles at the center frequencies of the M sub-bands.

[0123] The total damping current determination module 460 is used to determine the total damping current of the M sub-frequency bands based on the admittance magnitude values ​​of the M sub-frequency bands, the oscillation voltage amplitudes of the M sub-frequency bands, the admittance phase angles of the M sub-frequency bands, and the center frequencies of the M sub-frequency bands.

[0124] The current control command generation module 470 is used to determine the corrected d-axis current control command and the corrected q-axis current control command of the MMC converter station based on the total damping current of the M sub-frequency bands, the preset d-axis current control command, and the preset q-axis current control command, and to control the MMC converter station according to the corrected d-axis current control command and the corrected q-axis current control command.

[0125] Optionally, the first calculation module 420 mentioned above includes:

[0126] The time-frequency domain conversion submodule is used to convert the voltage response time-domain component into voltage response frequency-domain values ​​at N frequency points, and to convert the current disturbance time-domain component into current disturbance frequency-domain values ​​at N frequency points.

[0127] The equivalent impedance and equivalent impedance frequency characteristic curve determination submodule is used to divide the voltage response frequency domain value at the nth frequency point by the current disturbance frequency domain value at the nth frequency point to determine the equivalent impedance of the MMC converter station at the nth frequency point and the equivalent impedance frequency characteristic curve of the MMC converter station, n=1, 2, ..., N;

[0128] The equivalent impedance magnitude and equivalent impedance phase angle determination submodule is used to determine the equivalent impedance magnitude and equivalent impedance phase angle at N frequency points based on the equivalent impedance frequency characteristic curve.

[0129] The equivalent impedance magnitude determination submodule is used to determine the equivalent impedance magnitude at the rated frequency based on the equivalent impedance frequency characteristic curve and the rated frequency.

[0130] The short-circuit ratio determination submodule is used to square the rated voltage and divide it by the equivalent impedance magnitude at the rated frequency and the rated power to determine the short-circuit ratio at the rated frequency.

[0131] Optionally, the aforementioned broadband oscillation suppression device 40 for the MMC converter station further includes:

[0132] The virtual admittance determination module is used to determine the virtual admittance at the center frequency of the M sub-bands based on the admittance magnitude values ​​of the M sub-bands and the admittance phase angle at the center frequency of the M sub-bands;

[0133] The first admittance magnitude determination module is used to determine the first corrected admittance magnitude of the M sub-frequency bands at the current time based on the original equivalent admittance at the center frequency of the M sub-frequency bands, the virtual admittance at the center frequency of the M sub-frequency bands, the equivalent impedance at the N frequency points, and the admittance magnitude of the M sub-frequency bands.

[0134] Optionally, the above-mentioned first admittance magnitude determination module includes:

[0135] The first equivalent impedance determination submodule is used to sum the original equivalent admittance at the center frequency of the m-th sub-band and the virtual admittance of the m-th sub-band, and then take the reciprocal to determine the equivalent impedance after superimposed virtual admittance at the center frequency of the m-th sub-band.

[0136] The second equivalent impedance determination submodule is used to determine the equivalent impedance at the center frequency of the M sub-frequency bands based on the equivalent impedance at the N frequency points.

[0137] The impedance ratio determination submodule is used to divide the equivalent impedance after superimposed virtual admittance at the center frequency of the m-th sub-band by the equivalent impedance at the center frequency of the m-th sub-band to determine the impedance ratio at the center frequency of the m-th sub-band.

[0138] The phase angle determination submodule for impedance ratio is used to determine the phase angle of the impedance ratio at the center frequency of the M sub-bands based on the impedance ratio at the center frequency of the M sub-bands;

[0139] The phase margin determination submodule is used to determine the phase margin of the m-th sub-frequency band by subtracting the absolute value of the phase angle of the impedance ratio at the center frequency of the m-th sub-frequency band from 180°.

[0140] The first admittance modulus determination submodule is used to determine the first corrected admittance modulus values ​​of the M sub-frequency bands based on the admittance modulus values ​​of the M sub-frequency bands, the phase margin of the M sub-frequency bands, and a preset phase margin threshold.

[0141] Optionally, the aforementioned broadband oscillation suppression device 40 for the MMC converter station further includes:

[0142] The second admittance magnitude determination module is used to determine the second corrected admittance magnitude of the M sub-frequency bands based on the admittance magnitude of the M sub-frequency bands, the first corrected admittance magnitude of the M sub-frequency bands, and the preset filtering coefficients.

[0143] Optionally, the second computing module 430 mentioned above includes:

[0144] The oscillation energy determination submodule is used to determine the oscillation energy of the M sub-frequency bands based on the time-frequency power spectral density of the N frequency points, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands.

[0145] The oscillation voltage amplitude determination submodule is used to take the square root of the oscillation energy of the M sub-frequency bands to determine the oscillation voltage amplitude of the M sub-frequency bands;

[0146] The oscillation energy ratio determination submodule is used to divide the oscillation energy of the m-th sub-frequency band by the sum of the oscillation energies of the M sub-frequency bands to determine the oscillation energy ratio of the m-th sub-frequency band, where m = 1, 2, ..., M.

[0147] Optionally, the admittance phase angle determination module 450 mentioned above includes:

[0148] The first damping current determination submodule is used to determine the damping current of the mth sub-frequency band based on the admittance magnitude of the mth sub-frequency band, the oscillation voltage amplitude of the mth sub-frequency band, the admittance phase angle at the center frequency of the mth sub-frequency band, and the center frequency of the mth sub-frequency band.

[0149] The second damping current determination submodule is used to sum the damping currents of the M sub-frequency bands to determine the total damping current of the M sub-frequency bands.

[0150] Specific limitations regarding the broadband oscillation suppression device for MMC converter stations can be found in the above description of the broadband oscillation suppression method for MMC converter stations, and will not be repeated here. Each module in the aforementioned broadband oscillation suppression device for MMC converter stations can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in the electronic device, or stored in software in the memory of the electronic device, so that the processor can call and execute the corresponding operations of each module.

[0151] In embodiment nine, an electronic device 50 is provided; please refer to [reference needed]. Figure 4It includes a memory 510 and a processor 520, wherein the memory 510 is used to store computer programs; the processor 520 is used to execute the programs stored in the memory 510 to implement the broadband oscillation suppression method for MMC converter stations described in any embodiment of this application.

[0152] In Embodiment 10, a computer-readable storage medium is provided, which stores a computer program that, when executed by a processor, implements the broadband oscillation suppression method for MMC converter stations described in any embodiment of this application.

[0153] In this application, "multiple" refers to two or more.

[0154] In this application, unless otherwise expressly defined, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0155] The terms “first,” “second,” “third,” “fourth,” etc., in this application (if present) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0156] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0157] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, if the method includes steps A and B, it means that the method may include steps A and B performed sequentially, or it may include steps B and A performed sequentially. For example, if the method may also include step C, it means that step C may be added to the method in any order. For example, the method may include steps A, B, and C, or it may include steps A, C, and B, or it may include steps C, A, and B, etc.

[0158] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for suppressing broadband oscillations in an MMC converter station, characterized in that, The broadband oscillation suppression method for the MMC converter station includes: Step 100: Obtain the rated voltage, rated power, voltage response time-domain component, and current disturbance time-domain component of the MMC converter station at the current moment; obtain the original impedance phase angle and the original equivalent admittance at the center frequency of the M sub-bands of the MMC converter station at the previous moment; the current control loop on the AC side of the MMC converter station at the current moment contains a broadband disturbance signal, which covers N frequency points, and divides the N frequency points into M sub-bands, where N is a positive integer greater than 1, M is a positive integer greater than 1, and N is greater than or equal to M; Step 200: Based on the voltage response time-domain component, the current disturbance time-domain component, the rated voltage, the rated power, and the preset rated frequency of the MMC converter station, determine the equivalent impedance frequency characteristic curve and the short-circuit ratio of the MMC converter station. The equivalent impedance frequency characteristic curve includes the equivalent impedance of the MMC converter station at N frequency points, the equivalent impedance amplitude of the MMC converter station at N frequency points, and the equivalent impedance phase angle of the MMC converter station at N frequency points. Step 300: Determine the oscillation voltage amplitude and oscillation energy percentage of the M sub-frequency bands based on the voltage response time-domain component, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands. Step 400: First, multiply the preset admittance reference value by the oscillation energy ratio of the m-th sub-frequency band, and then divide it by the short-circuit ratio of the MMC converter station to determine the admittance magnitude value of the m-th sub-frequency band, where m = 1, 2, ..., M; Step 500: Determine the admittance phase angle at the center frequency of the M sub-bands at the current moment based on the equivalent impedance frequency characteristic curve, the center frequencies of the M sub-bands, and the original impedance phase angle at the center frequencies of the M sub-bands. Step 600: Determine the total damping current of the M sub-frequency bands based on the admittance magnitude of the M sub-frequency bands, the oscillation voltage amplitude of the M sub-frequency bands, the admittance phase angle of the M sub-frequency bands, and the center frequency of the M sub-frequency bands. Step 700: Based on the total damping current of the M sub-frequency bands, the preset d-axis current control command, and the preset q-axis current control command, determine the modified d-axis current control command and the modified q-axis current control command of the MMC converter station, and control the MMC converter station according to the modified d-axis current control command and the modified q-axis current control command.

2. The broadband oscillation suppression method for MMC converter stations according to claim 1, characterized in that, Step 200 includes: Step 201: Convert the voltage response time-domain component into voltage response frequency-domain values ​​at N frequency points, and convert the current disturbance time-domain component into current disturbance frequency-domain values ​​at N frequency points. Step 202: Divide the voltage response frequency domain value at the nth frequency point by the current disturbance frequency domain value at the nth frequency point to determine the equivalent impedance of the MMC converter station at the nth frequency point and the equivalent impedance frequency characteristic curve of the MMC converter station, n=1, 2, ..., N; Step 203: Based on the equivalent impedance frequency characteristic curve, determine the equivalent impedance amplitude and the equivalent impedance phase angle at N frequency points. Step 204: Determine the equivalent impedance magnitude at the rated frequency based on the equivalent impedance frequency characteristic curve and the rated frequency. Step 205: Squaring the rated voltage and dividing it by the equivalent impedance modulus at the rated frequency and the rated power, determines the short-circuit ratio at the rated frequency.

3. The broadband oscillation suppression method for MMC converter stations according to claim 2, characterized in that, After step 500 and before step 600, the following is also included: Step 801: Determine the virtual admittance at the center frequency of the M sub-bands based on the admittance magnitude values ​​of the M sub-bands and the admittance phase angle at the center frequency of the M sub-bands; Step 802: Based on the original equivalent admittance at the center frequency of the M sub-bands, the virtual admittance at the center frequency of the M sub-bands, the equivalent impedance at the N frequency points, and the admittance magnitude of the M sub-bands, determine the first corrected admittance magnitude of the M sub-bands at the current time.

4. The broadband oscillation suppression method for MMC converter stations according to claim 3, characterized in that, Step 802 includes: Step 8021: Summing the original equivalent admittance at the center frequency of the m-th sub-band and the virtual admittance of the m-th sub-band, and taking the reciprocal, to determine the equivalent impedance after superimposing the virtual admittance at the center frequency of the m-th sub-band; Step 8022: Determine the equivalent impedance at the center frequency of the M sub-bands based on the equivalent impedance of the N frequency points. Step 8023: Divide the equivalent impedance after superimposed virtual admittance at the center frequency of the m-th sub-band by the equivalent impedance at the center frequency of the m-th sub-band to determine the impedance ratio at the center frequency of the m-th sub-band. Step 8024: Determine the phase angle of the impedance ratio at the center frequency of the M sub-bands based on the impedance ratio at the center frequency of the M sub-bands; Step 8025: Subtract the absolute value of the phase angle of the impedance ratio at the center frequency of the m-th sub-band from 180° to determine the phase margin of the m-th sub-band. Step 8026: Determine the first corrected admittance magnitude values ​​of the M sub-frequency bands based on the admittance magnitude values ​​of the M sub-frequency bands, the phase margin of the M sub-frequency bands, and a preset phase margin threshold.

5. The broadband oscillation suppression method for MMC converter stations according to claim 3, characterized in that, Following step 802, the following also includes: Based on the admittance magnitude values ​​of the M sub-frequency bands, the first corrected admittance magnitude values ​​of the M sub-frequency bands, and the preset filtering coefficients, the second corrected admittance magnitude values ​​of the M sub-frequency bands are determined.

6. The broadband oscillation suppression method for MMC converter stations according to claim 1, characterized in that, Step 300 includes: Step 301: Determine the oscillation energy of the M sub-frequency bands based on the time-frequency power spectral density of the N frequency points, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands. Step 302: Take the square root of the oscillation energy of the M sub-frequency bands to determine the oscillation voltage amplitude of the M sub-frequency bands; Step 303: Divide the oscillation energy of the m-th sub-frequency band by the sum of the oscillation energies of the M sub-frequency bands to determine the oscillation energy percentage of the m-th sub-frequency band, where m = 1, 2, ..., M.

7. The broadband oscillation suppression method for MMC converter stations according to claim 1, characterized in that, Step 600 includes: Step 601: Determine the damping current of the m-th sub-frequency band based on the admittance magnitude of the m-th sub-frequency band, the oscillation voltage amplitude of the m-th sub-frequency band, the admittance phase angle at the center frequency of the m-th sub-frequency band, and the center frequency of the m-th sub-frequency band. Step 602: Sum the damping currents of the M sub-frequency bands to determine the total damping current of the M sub-frequency bands.

8. A broadband oscillation suppression device for an MMC converter station, characterized in that, The broadband oscillation suppression device for the MMC converter station includes: The data acquisition module is used to acquire the rated voltage, rated power, voltage response time-domain component, and current disturbance time-domain component of the MMC converter station at the current moment, and to acquire the original impedance phase angle and the original equivalent admittance at the center frequency of the M sub-bands of the MMC converter station at the previous moment. The current control loop on the AC side of the MMC converter station at the current moment contains a broadband disturbance signal, which covers N frequency points. The N frequency points are divided into M sub-bands, where N is a positive integer greater than 1, M is a positive integer greater than 1, and N is greater than or equal to M. The first calculation module is used to determine the equivalent impedance frequency characteristic curve and the short-circuit ratio of the MMC converter station based on the voltage response time-domain component, the current disturbance time-domain component, the rated voltage, the rated power, and the preset rated frequency of the MMC converter station. The equivalent impedance frequency characteristic curve includes the equivalent impedance of the MMC converter station at N frequency points, the equivalent impedance amplitude of the MMC converter station at N frequency points, and the equivalent impedance phase angle of the MMC converter station at N frequency points. The second calculation module is used to determine the oscillation voltage amplitude and the oscillation energy ratio of the M sub-frequency bands based on the voltage response time-domain component, the preset upper frequency threshold of the M sub-frequency bands, and the preset lower frequency threshold of the M sub-frequency bands. The admittance modulus determination module is used to first multiply the preset admittance reference value by the oscillation energy ratio of the m-th sub-frequency band, and then divide it by the short-circuit ratio of the MMC converter station to determine the admittance modulus value of the m-th sub-frequency band, where m = 1, 2, ..., M; The admittance phase angle determination module is used to determine the admittance phase angle at the center frequency of the M sub-bands at the current moment based on the equivalent impedance frequency characteristic curve, the center frequencies of the M sub-bands, and the original impedance phase angles at the center frequencies of the M sub-bands. The total damping current determination module is used to determine the total damping current of the M sub-frequency bands based on the admittance magnitude values ​​of the M sub-frequency bands, the oscillation voltage amplitudes of the M sub-frequency bands, the admittance phase angles of the M sub-frequency bands, and the center frequencies of the M sub-frequency bands. The current control command generation module is used to determine the corrected d-axis current control command and the corrected q-axis current control command of the MMC converter station based on the total damping current of the M sub-frequency bands, the preset d-axis current control command, and the preset q-axis current control command, and to control the MMC converter station according to the corrected d-axis current control command and the corrected q-axis current control command.

9. An electronic device, characterized in that, It includes a processor and a memory, wherein the memory is used to store computer programs; the processor is used to execute the programs stored in the memory to implement the broadband oscillation suppression method for MMC converter stations as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the broadband oscillation suppression method for MMC converter stations according to any one of claims 1-7.

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