A method, apparatus, device and medium for suppressing broadband oscillation of a converter

Abstract

The application discloses a method and device for suppressing wide-frequency oscillation of a converter, equipment and a medium, and belongs to the field of power grid safety. The method is as follows: obtaining the fundamental equivalent impedance of the converter corresponding to the fundamental frequency and the wide-frequency equivalent impedance corresponding to each interference frequency through a preset interference signal; judging the damping characteristic of the converter according to the real part of the fundamental equivalent impedance; if the damping characteristic is positive, and the imaginary part of at least one wide-frequency equivalent impedance satisfies a preset resonance criterion, determining a resonance frequency band from all interference frequencies, and adjusting the current control loop parameters of the converter according to the resonance frequency band until all imaginary parts do not satisfy the preset resonance criterion, so as to realize wide-frequency oscillation suppression; wherein, the preset resonance criterion is determined according to the reactance characteristic of the wide-frequency equivalent impedance. The application can improve the accuracy of wide-frequency oscillation suppression of the converter.

Description

Technical Field

[0001] This application relates to the field of power grid safety, and in particular to a method, apparatus, equipment and medium for suppressing wideband oscillations in a converter. Background Technology

[0002] With the continuous expansion of new energy grid connection, converters are increasingly widely used in power grids. During the coupled operation of converters and the power grid, interactions can easily occur within different frequency ranges, leading to broadband oscillations. These oscillations can affect the stability of system operation, thus necessitating the suppression of broadband oscillations in converters.

[0003] In existing technologies, methods for suppressing converter oscillations are mostly based on fundamental impedance analysis or small-signal models to determine stability and adjust control parameters accordingly. However, these methods typically rely on idealized modeling or offline analysis results, making it difficult to reflect the dynamic characteristics of the converter under the influence of grid impedance changes and multi-frequency coupling during actual operation, leading to inaccurate broadband oscillation suppression. Furthermore, while some methods incorporate frequency domain analysis, they suffer from biases in identifying resonant frequency bands, making it difficult to match control parameter adjustments with actual oscillation characteristics, resulting in inaccurate broadband oscillation suppression. Summary of the Invention

[0004] This application provides a method, apparatus, device, and medium for suppressing wideband oscillations in converters, which can solve the problem of low accuracy in suppressing wideband oscillations in existing technologies.

[0005] Some embodiments of this application provide a method for suppressing wideband oscillations in a converter, including: The equivalent impedance of the converter at each frequency after a preset interference signal is injected is obtained; the equivalent impedance includes: the fundamental equivalent impedance at the fundamental frequency and the broadband equivalent impedance at each interference frequency. The damping characteristics of the converter are determined based on the real part of the fundamental equivalent impedance. If the damping characteristic is a positive damping characteristic, and the imaginary part of at least one of the wideband equivalent impedances satisfies the preset resonance criterion, the resonant frequency band between the power grid and the converter is determined from all the interference frequencies, and the current control loop parameters of the converter are adjusted according to the resonant frequency band until the imaginary part of all the wideband equivalent impedances no longer satisfies the preset resonance criterion, so as to achieve wideband oscillation suppression; wherein, the preset resonance criterion is determined based on the reactance characteristics of the wideband equivalent impedance.

[0006] Compared with existing technologies, the above embodiments have the following beneficial effects: This application injects a preset interference signal into the converter control signal to excite the converter at multiple frequencies, and calculates the equivalent impedance based on the voltage and current responses corresponding to each frequency point, thereby achieving online acquisition of the converter's impedance characteristics in the fundamental frequency and wide frequency range; furthermore, by judging the damping characteristics based on the real part of the fundamental equivalent impedance, and on this basis, by judging the imaginary part of the wide frequency equivalent impedance, the frequency range in which the converter and the grid satisfy the resonance condition is identified, and by adjusting the current control loop parameters to change the bandwidth of the current control loop, the equivalent impedance in the frequency range is changed from capacitive to inductive characteristics, thereby breaking the impedance coupling resonance condition between the grid and the converter. Through the above method, frequency segment adjustment based on impedance characteristics is realized, improving the accuracy of wide frequency oscillation suppression.

[0007] Furthermore, in some embodiments of this application, after determining the damping characteristics of the converter based on the real part of the fundamental equivalent impedance, the method further includes: if the damping characteristic is a negative damping characteristic, adjusting the phase-locked loop parameters of the converter based on the real part of the fundamental equivalent impedance to adjust the fundamental equivalent impedance until the damping characteristic is a positive damping characteristic.

[0008] Compared with existing technologies, the above embodiments have the following advantages: After identifying the fundamental equivalent impedance and determining that the converter is in a negative damping state, the phase-locked loop (PLL) parameters are adaptively adjusted based on the real part of the equivalent impedance. This allows the dynamic characteristics of the PLL to match the changes in grid impedance in real time, thereby changing the phase relationship between the converter output voltage and current and improving the system damping level. With iterative adjustment of the parameters, the converter's equivalent impedance gradually changes from negative damping to positive damping, effectively eliminating the source of oscillating energy injected into the grid and avoiding the amplification and propagation of broadband oscillations.

[0009] Further, the phase-locked loop parameters include: a first proportional gain and a first integral gain of the phase-locked loop; adjusting the phase-locked loop parameters of the converter according to the real part of the fundamental equivalent impedance includes: The first adjustment step size within the current adjustment cycle is determined based on the real part of the fundamental equivalent impedance. The first proportional gain is reduced based on the first adjustment step size; The first integral gain is updated based on the adjusted first proportional gain to adjust the phase-locked loop parameters.

[0010] Compared with the prior art, the above embodiments have the following beneficial effects: by determining the adjustment step size based on the real part of the fundamental equivalent impedance and adjusting the proportional gain of the phase-locked loop by reducing the amplitude, while simultaneously updating the integral gain, the phase-locked loop parameters can adaptively change with the degree of negative damping. This avoids the problem of insufficient adaptation to different grid strengths under fixed parameter conditions, enabling the converter to adjust the control parameters in a timely manner when negative damping occurs, causing the real part of the equivalent impedance to change from a negative value to a positive value, thereby improving the pertinence and stability of negative damping suppression.

[0011] Further, determining the first adjustment step size within the current adjustment period based on the real part of the fundamental equivalent impedance includes: Based on the real part of the fundamental equivalent impedance and a preset inertial time constant, an adjustment coefficient characterizing the oscillation energy intensity of the current system is calculated; wherein, the inertial time constant is obtained by calibration according to the quantization range of the real part; Multiply the adjustment coefficient by the preset maximum reduction ratio to obtain the first adjustment step size within the current adjustment cycle.

[0012] Compared with the prior art, the above embodiments have the following beneficial effects: by introducing an adjustment coefficient calculated based on the real part and the inertial time constant, and combining it with the maximum reduction ratio to determine the adjustment step size, the adjustment range of the phase-locked loop parameters can be continuously changed with the negative damping strength, thereby avoiding system oscillation or over-adjustment problems caused by parameter mutations, making the negative damping suppression process smoother and more controllable, and improving the dynamic stability of the system during parameter adjustment.

[0013] Further, the current control loop parameters include: a second proportional gain and a second integral gain of the current control loop; determining the resonant frequency band between the power grid and the converter from all the interference frequencies, and adjusting the current control loop parameters of the converter according to the resonant frequency band, includes: From all the broadband equivalent impedances, select the first broadband equivalent impedance whose imaginary part satisfies the preset resonance criterion, and construct the resonance frequency band based on the interference frequencies corresponding to all the first broadband equivalent impedances; Calculate the target resonant angular velocity based on the largest interference frequency in the resonant frequency band, and determine the target bandwidth threshold of the current control loop based on the target resonant angular velocity; Obtain the actual bandwidth frequency of the current control loop within the current adjustment cycle, and adjust the second proportional gain according to the actual bandwidth frequency and the target bandwidth threshold; Based on the adjusted second proportional gain, the second integral gain is updated synchronously to ensure that the resonant frequency band is within the active control range of the current control loop; wherein the active control range is determined by the actual bandwidth frequency.

[0014] Compared with existing technologies, the above embodiments have the following beneficial effects: By selecting impedances whose imaginary parts satisfy the resonance criterion from various broadband equivalent impedances, and constructing a resonance frequency band based on the corresponding interference frequency, the resonance identification is expanded from a single frequency point judgment to a holistic judgment of the frequency range. This allows the resonance characteristics formed by multi-frequency coupling between the power grid and the converter to be reflected, improving the completeness and accuracy of resonance identification. Furthermore, by determining the target resonance angular velocity based on the resonance frequency band, and setting the target bandwidth threshold of the current control loop accordingly, and then adjusting the proportional gain based on the relationship between the actual bandwidth and the target bandwidth, the bandwidth of the current control loop can cover the resonance frequency band. This ensures that the equivalent impedance of the converter within this frequency band remains inductive, avoiding the formation of impedance matching conditions between the capacitive converter and the inductive power grid, and improving the suppression capability of broadband resonance.

[0015] Further, adjusting the second proportional gain based on the actual bandwidth frequency and the target bandwidth threshold includes: Calculate the frequency deviation between the actual bandwidth frequency and the target bandwidth threshold, and determine the second adjustment step size of the second proportional gain within the current adjustment period; When the actual bandwidth frequency is less than the target bandwidth threshold, the second proportional gain is increased based on the second adjustment step size so that the actual bandwidth frequency is not less than the target bandwidth threshold.

[0016] Compared with the prior art, the above embodiments have the following beneficial effects: by determining the adjustment step size of the proportional gain based on the deviation between the actual bandwidth frequency and the target bandwidth threshold, and adjusting the increase when the actual bandwidth is less than the target bandwidth, the current control loop parameters can be adaptively adjusted with the bandwidth deviation, thereby avoiding the problems of slow convergence speed or over-adjustment caused by fixed step size adjustment, and improving the efficiency and stability of the bandwidth adjustment process.

[0017] Further, obtaining the equivalent impedance of the converter at various frequencies after the injection of a preset interference signal includes: The electrical signal output by the converter under the influence of the interference signal is collected; Extract electrical signal components corresponding to each frequency from the electrical signal; wherein, the electrical signal components include: voltage components and current components corresponding to the frequency; The corresponding equivalent impedances are calculated based on the ratio of the voltage component to the current component.

[0018] Compared with the prior art, the above embodiments have the following beneficial effects: by extracting the frequency components of the converter output electrical signal and calculating the equivalent impedance based on the voltage and current components corresponding to each frequency point, the impedance acquisition process can achieve the extraction of impedance characteristics at multiple frequency points without additional external excitation equipment, thereby improving the real-time performance and practicality of impedance identification, and providing a data foundation for subsequent negative damping identification and resonance determination based on impedance characteristics.

[0019] Another embodiment of this application provides a wideband oscillation suppression device for a converter, including: a data acquisition module, a judgment module, and an execution module; The acquisition module is used to acquire the equivalent impedance of the converter at various frequencies after a preset interference signal is injected; the equivalent impedance includes: the fundamental equivalent impedance at the fundamental frequency and the broadband equivalent impedance at each interference frequency. The judgment module is used to determine the damping characteristics of the converter based on the real part of the fundamental equivalent impedance. The execution module is configured to, if the damping characteristic is a positive damping characteristic and the imaginary part of at least one of the wideband equivalent impedances satisfies a preset resonance criterion, determine the resonant frequency band between the power grid and the converter from all the interference frequencies, and adjust the current control loop parameters of the converter according to the resonant frequency band until the imaginary part of all the wideband equivalent impedances no longer satisfies the preset resonance criterion, so as to achieve wideband oscillation suppression; wherein, the preset resonance criterion is determined based on the reactance characteristics of the wideband equivalent impedance.

[0020] Another embodiment of this application also provides a terminal device, including: a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein when the processor executes the computer program, it implements the steps of the wideband oscillation suppression method of the converter of this application.

[0021] Another embodiment of this application also provides a computer-readable storage medium item, including: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform steps such as the broadband oscillation suppression method of the converter of this application. Attached Figure Description

[0022] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1This is a flowchart illustrating a broadband oscillation suppression method for a converter provided in some embodiments of this application; Figure 2 This is a schematic diagram of the structure of a wideband oscillation suppression device for a converter provided in some embodiments of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] In the description of the embodiments 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, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0030] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0031] In existing technologies, methods for suppressing converter oscillations are mostly based on fundamental impedance analysis or small-signal models to determine stability and adjust control parameters accordingly. However, these methods typically rely on idealized modeling or offline analysis results, making it difficult to reflect the dynamic characteristics of the converter under the influence of grid impedance changes and multi-frequency coupling during actual operation, leading to inaccurate broadband oscillation suppression. Furthermore, while some methods incorporate frequency domain analysis, they suffer from biases in identifying resonant frequency bands, making it difficult to match control parameter adjustments with actual oscillation characteristics, resulting in inaccurate broadband oscillation suppression.

[0032] Please refer to Figure 1 To address the problem of inaccurate broadband oscillation suppression in existing converters, this application provides a broadband oscillation suppression method for converters, comprising the following steps S101 to S103: S101: Obtain the equivalent impedance of the converter at each frequency after a preset interference signal is injected; the equivalent impedance includes: the fundamental equivalent impedance at the fundamental frequency and the broadband equivalent impedance at each interference frequency.

[0033] This application abandons the introduction of external hardware excitation sources and adopts a software injection method. Specifically, a digital disturbance signal (i.e., the interference signal) within a preset frequency range is directly superimposed on the modulation wave signal (i.e., the control signal) output by the converter control loop. Since the modulation wave directly determines the duty cycle of the inverter switching transistors, the disturbance is linearly mapped to the output of the converter through a pulse width modulation process, thereby achieving dynamic injection of sweep frequency interference during converter operation without changing the main circuit structure.

[0034] Furthermore, in some embodiments of this application, obtaining the equivalent impedance of the converter at various frequencies after the injection of a preset interference signal includes: The electrical signal output by the converter under the influence of the interference signal is collected; Extract electrical signal components corresponding to each frequency from the electrical signal; wherein, the electrical signal components include: voltage components and current components corresponding to the frequency; The corresponding equivalent impedances are calculated based on the ratio of the voltage component to the current component.

[0035] Since the interference signal is a digital disturbance signal constructed within a preset frequency range, it contains multiple frequency components of different frequencies. Each frequency component, after being injected through a modulated wave and subjected to pulse width modulation, is mapped to the converter output side, thereby exciting the converter at the corresponding frequency. Therefore, each frequency component in the interference signal corresponds to an excitation frequency, and the converter generates corresponding voltage and current responses (i.e., electrical signal components) at each frequency, which are used to calculate the equivalent impedance corresponding to the frequency. Using the fundamental frequency as a reference, each interference frequency can correspond to an integer multiple or a non-integer multiple of the fundamental frequency; this application uses an integer multiple as an example for explanation.

[0036] Preferably, in some embodiments of this application, the frequency includes: a fundamental frequency and several interference frequencies.

[0037] Preferably, in some embodiments of this application, the equivalent impedance is calculated using the following formula: ; in, The equivalent impedance is the kth harmonic. Each order of harmonic corresponds to a frequency, and the frequency corresponding to the 1st harmonic is the fundamental frequency. and These are the voltage and current components corresponding to the kth harmonic, respectively; and These are the amplitudes of the voltage and current components corresponding to the kth harmonic, respectively. and These are the phase angles of the voltage and current components corresponding to the kth harmonic, respectively.

[0038] This application extracts the frequency components of the converter output electrical signal and calculates the equivalent impedance based on the voltage and current components corresponding to each frequency point. This allows the impedance acquisition process to extract the impedance characteristics at multiple frequency points without the need for additional external excitation equipment, thereby improving the real-time performance and practicality of impedance identification and providing a data foundation for subsequent negative damping identification and resonance determination based on impedance characteristics.

[0039] S102: Determine the damping characteristics of the converter based on the real part of the fundamental equivalent impedance.

[0040] Preferably, in some embodiments of the application, after obtaining the equivalent impedance corresponding to each frequency, the real and imaginary parts of each equivalent impedance are obtained using the following formula: ; in, for The real part; for The imaginary part; It is an imaginary number.

[0041] Preferably, in some embodiments of this application, determining the damping characteristics of the converter based on the real part of the fundamental equivalent impedance includes: obtaining the real part of the equivalent impedance corresponding to the fundamental frequency, determining whether the real part is greater than 0, and if it is greater than 0, determining that the damping characteristics of the current converter are positive damping characteristics, and if it is less than 0, determining that the damping characteristics of the current converter are negative damping characteristics.

[0042] Furthermore, in some embodiments of this application, after determining the damping characteristics of the converter based on the real part of the fundamental equivalent impedance, the method further includes: if the damping characteristics are negative damping characteristics, adjusting the phase-locked loop parameters of the converter based on the real part of the fundamental equivalent impedance to adjust the fundamental equivalent impedance until the damping characteristics are positive damping characteristics.

[0043] The phase-locked loop (PLL) is a crucial component in the converter control system, and its parameter configuration significantly impacts the converter's equivalent impedance characteristics. When the PLL's gain parameter is improperly tuned, the converter is prone to exhibiting negative damping characteristics over a preset wide frequency range (e.g., 100Hz to 1.5kHz). Under this negative damping, the converter injects energy into the resonant frequency band of the power grid, which is related to the inductance and capacitance parameters, leading to a decrease in the system's resonance attenuation capability and even causing oscillation amplification. Therefore, properly configuring the PLL parameters to enable the converter to exhibit positive damping characteristics in the corresponding frequency band is of great significance for suppressing wideband oscillations and improving system stability.

[0044] This application identifies the negative damping characteristic by using the equivalent impedance of the converter obtained in step S101, and then changes the value in real time. (PLL's first proportional gain) (The first integral gain of the PLL) converts negative damping into positive damping, eliminating the oscillating energy source.

[0045] The closed-loop transfer function of the PLL is: ; in: For complex frequency domain operators , ; This is the complex frequency domain form of the small phase signal tracked by the PLL, and the time domain is... ; The complex frequency domain form of the actual phase small signal of the power grid is given by the time domain as follows: ; The closed-loop transfer function of a phase-locked loop (PLL) characterizes the closed-loop tracking characteristic of the PLL output phase to the grid input phase disturbance, and is a complex frequency domain operator. The function; This represents the phase voltage amplitude.

[0046] Due to traditional and Both are fixed gain converters, and their parameters cannot be modified according to the grid connection status during grid connection. However, improper gain parameter settings can lead to tracking phase lag in specific frequency bands, resulting in out-of-phase output voltage and current, and exhibiting negative damping characteristics. This application proposes adaptive gain modification during grid connection. When the acquisition detects that the converter exhibits negative damping, the step size is adaptively adjusted according to the degree of negative damping. and .

[0047] Furthermore, in some embodiments of this application, the phase-locked loop parameters include: a first proportional gain and a first integral gain of the phase-locked loop; adjusting the phase-locked loop parameters of the converter according to the real part of the fundamental equivalent impedance includes the following steps S1021 to S1023: S1021: Determine the first adjustment step size within the current adjustment cycle based on the real part of the fundamental equivalent impedance.

[0048] Furthermore, in some embodiments of this application, determining the first adjustment step size within the current adjustment period based on the real part of the fundamental equivalent impedance includes: Based on the real part of the fundamental equivalent impedance and a preset inertial time constant, an adjustment coefficient characterizing the oscillation energy intensity of the current system is calculated; wherein, the inertial time constant is obtained by calibration according to the quantization range of the real part; Multiply the adjustment coefficient by the preset maximum reduction ratio to obtain the first adjustment step size within the current adjustment cycle.

[0049] Preferably, in some embodiments of this application, the formula for calculating the first adjustment step size is: ; in, The first adjustment step size; To represent the maximum relative reduction percentage, this application's embodiment uses 75%; The inertial time constant is based on The quantization range is calibrated to 0.5 in this embodiment.

[0050] This application introduces an adjustment coefficient calculated based on the real part and the inertial time constant, and determines the adjustment step size by combining the maximum reduction ratio. This allows the adjustment amplitude of the phase-locked loop parameters to change continuously with the negative damping strength, thereby avoiding system oscillation or over-adjustment problems caused by parameter mutations. This makes the negative damping suppression process smoother and more controllable, and improves the dynamic stability of the system during parameter adjustment.

[0051] S1022: Adjust the first proportional gain by reducing the amplitude based on the first adjustment step size.

[0052] Preferably, in some embodiments of this application, the first proportional gain is adjusted using the following formula: ); in, This is the adjusted first proportional gain; This is the initial proportional gain before adjustment.

[0053] S1023: Update the first integral gain according to the adjusted first proportional gain to adjust the phase-locked loop parameters.

[0054] Preferably, in some embodiments of this application, the first integral gain is updated using the following formula: ; in, This is the updated first integral gain; The peak value of the rated phase voltage at the power grid frequency is 311V. For example, if the phase voltage is 220V, then the peak voltage is 311V.

[0055] It should be noted that steps S1021 to S1023 are an iterative process. By continuously adjusting the first proportional gain and the first integral gain, the real part of the equivalent impedance corresponding to the fundamental frequency tends to a positive value from a negative value. When the real part is positive, the iterative process of steps S1021 to S1023 is completed.

[0056] This application determines the adjustment step size based on the real part of the fundamental equivalent impedance and adjusts the proportional gain of the phase-locked loop by reducing the amplitude, while simultaneously updating the integral gain. This allows the phase-locked loop parameters to adaptively change with the degree of negative damping, thereby avoiding the problem of insufficient adaptation to different grid strengths under fixed parameter conditions. This enables the converter to adjust the control parameters in a timely manner when negative damping occurs, causing the real part of the equivalent impedance to change from a negative value to a positive value, thus improving the targeting and adjustment stability of negative damping suppression.

[0057] S103: If the damping characteristic is a positive damping characteristic, and the imaginary part of at least one of the wideband equivalent impedances satisfies the preset resonance criterion, the resonant frequency band between the power grid and the converter is determined from all the interference frequencies, and the current control loop parameters of the converter are adjusted according to the resonant frequency band until the imaginary part of all the wideband equivalent impedances no longer satisfies the preset resonance criterion, so as to achieve wideband oscillation suppression; wherein, the preset resonance criterion is determined based on the reactance characteristics of the wideband equivalent impedance.

[0058] The equivalent reactance characteristic of a converter changes with frequency. It typically exhibits inductive characteristics at power frequency or low frequencies, while its impedance gradually transitions from inductive to capacitive in the mid-to-high frequency range. The current control loop plays a dominant role in the reactance characteristics of the converter in the mid-to-high frequency range, and its parameter configuration directly affects the frequency position of the inductive-to-capacitive transition. By adaptively adjusting the parameters of the current control loop, the frequency of this reactance transition can be adjusted, thereby allowing the converter's impedance characteristics to avoid the resonant frequency band formed by the grid's inductance and capacitance parameters. This reduces the risk of resonance and achieves active suppression of system oscillations.

[0059] Preferably, in some embodiments of this application, the current control loop is a second-order PI control unity negative feedback system, and the open-loop transfer function is: ; in, Let be the open-loop transfer function of the current control loop, which is a complex frequency domain operator. The function; It is the second proportional gain corresponding to the current control loop; It is the second integral gain corresponding to the current control loop; It is the value of the filter inductance for grid connection of the converter.

[0060] The phase lag characteristic that determines the current control loop is the phase difference between the actual current and the commanded current. The calculation formula is: ; in, It is the angular velocity, calculated by the phase-locked loop; This is the optimal damping ratio, typically taken as 0.707 (when...). hour); It is the natural angular frequency. .

[0061] Depend on and Angular frequency critical threshold (Also the actual bandwidth frequency), the calculation formula is: ; when At this time, the current control loop actively controls the current, and the actual current lags slightly behind the commanded current (ultimately lags behind the grid voltage), and the equivalent impedance of the converter is inductive; when At this time: the current control loop is out of control, the filter capacitor dominates the current characteristics, the actual current leads the grid voltage, and the equivalent impedance of the converter is capacitive.

[0062] From the above formula, we can see that When it increases, Increase It also increased and improved accordingly. This broadens the active control frequency range of the current control loop, making the equivalent impedance inductive, and vice versa.

[0063] Further, in some embodiments of this application, the current control loop parameters include: a second proportional gain and a second integral gain of the current control loop; the step of determining the resonant frequency band between the power grid and the converter from all the interference frequencies, and adjusting the current control loop parameters of the converter according to the resonant frequency band, includes the following steps S1031 to S1034: S1031: From all the broadband equivalent impedances, select the first broadband equivalent impedance whose imaginary part satisfies the preset resonance criterion, and construct the resonance frequency band according to the interference frequency corresponding to all the first broadband equivalent impedances.

[0064] Preferably, in some embodiments of this application, the step of screening the first broadband equivalent impedance whose imaginary part satisfies the preset resonance criterion includes: based on the equivalent impedance obtained in S101, determining the imaginary part of the corresponding equivalent impedance at each interference frequency. If it is approximately equal to 0, then this equivalent impedance is taken as the first broadband equivalent impedance. It is understandable that when... At that time, the interference frequency Resonance is prone to occur because the equivalent inductance of the power grid and the equivalent capacitance of the converter both change with the increasing frequency of the interference source, resulting in multiple resonance points. Each resonance point corresponds to an interference frequency and an equivalent impedance. Therefore, the interference frequency at which resonance occurs can be obtained through simulation and plotting. , , The aforementioned interference frequencies together form the resonant frequency band.

[0065] S1032: Calculate the target resonant angular velocity based on the largest interference frequency in the resonant frequency band, and determine the target bandwidth threshold of the current control loop based on the target resonant angular velocity.

[0066] Preferably, in some embodiments of this application, it is assumed that the maximum interference frequency currently recorded is Then the maximum interference frequency can be determined. The angular velocity corresponding to the maximum resonance condition is , Maximum interference frequency The corresponding angular velocity; the target bandwidth threshold of the current control loop is set based on the following formula. : .

[0067] Because adjustments are needed Furthermore widening Let the actual bandwidth frequency of the current control loop be... Always not less than the target bandwidth threshold This ensures that the entire resonant frequency band falls within the active control range of the inner current loop (i.e., w < 0.05). This ensures that the converter maintains inductive impedance within the resonant frequency band, breaking the LC resonance condition between the capacitive converter and the inductive power grid.

[0068] S1033: Obtain the actual bandwidth frequency of the current control loop in the current adjustment cycle, and adjust the second proportional gain according to the actual bandwidth frequency and the target bandwidth threshold.

[0069] Furthermore, in some embodiments of this application, adjusting the second proportional gain based on the actual bandwidth frequency and the target bandwidth threshold includes: Calculate the frequency deviation between the actual bandwidth frequency and the target bandwidth threshold, and determine the second adjustment step size of the second proportional gain within the current adjustment period; When the actual bandwidth frequency is less than the target bandwidth threshold, the second proportional gain is increased based on the second adjustment step size so that the actual bandwidth frequency is not less than the target bandwidth threshold.

[0070] Preferably, in some embodiments of this application, the second adjustment step size The calculation formula is: ; ; in, yes The maximum adjustment step size; E is the bandwidth deviation ratio; T is the inertia time constant, which is less than 0.3. The larger the value, the smoother the step size.

[0071] Preferably, in some embodiments of this application, the adjustment formula for the second proportional gain is: ; ; in, This is the adjusted second proportional gain; To adjust the previous proportional gain; and These are the upper and lower limits of the second proportional gain, respectively. In this embodiment of the application, Using 150% of the initial second proportional gain, Using 30% of the initial second proportional gain, the initial second proportional gain , It is the power frequency of the feeder.

[0072] This application filters impedances whose imaginary parts satisfy the resonance criterion from various broadband equivalent impedances and constructs a resonance frequency band based on the corresponding interference frequency. This expands resonance identification from a single frequency point judgment to a holistic judgment of the frequency range, thereby reflecting the resonance characteristics formed by multi-frequency coupling between the power grid and the converter, and improving the completeness and accuracy of resonance identification. Furthermore, by determining the adjustment step size of the proportional gain based on the deviation between the actual bandwidth frequency and the target bandwidth threshold, and adjusting the increase when the actual bandwidth is less than the target bandwidth, the current control loop parameters can be adaptively adjusted according to the bandwidth deviation. This avoids the problems of slow convergence speed or over-adjustment caused by fixed step size adjustment, and improves the efficiency and stability of the bandwidth adjustment process.

[0073] S1034: Based on the adjusted second proportional gain, synchronously update the second integral gain so that the resonant frequency band is within the active control range of the current control loop; wherein, the active control range is determined by the actual bandwidth frequency.

[0074] Preferably, in some embodiments of this application, the update formula for the second integral gain is: ; in, This is the updated second integral gain.

[0075] It is understandable that step S104 is an iterative process, in which the second proportional gain and the second integral gain are updated according to the second adjustment step size of each adjustment cycle, so that the resonant frequency segment falls within the active control range of the current control loop. At this time, the imaginary part of each equivalent impedance corresponding to the interference frequency is greater than 0.

[0076] By determining the target resonant angular velocity based on the resonant frequency band and setting the target bandwidth threshold of the current control loop accordingly, and then adjusting the proportional gain based on the relationship between the actual bandwidth and the target bandwidth, the bandwidth of the current control loop can cover the resonant frequency band. This ensures that the equivalent impedance of the converter in this frequency band remains inductive, avoids impedance matching conditions between the capacitive converter and the inductive power grid, and improves the ability to suppress broadband resonance.

[0077] In summary, the broadband oscillation suppression method for converters provided in this application has the following advantages compared with the prior art: (1) Currently, most impedance scanning methods require independent excitation sources, which are costly and impractical. This application uses harmonic superposition within the modulation wave of the control converter, which is cost-effective and convenient for impedance scanning; (2) Currently, impedance scanning is mostly offline, requiring the converter to be powered off before operation, which is complex and time-consuming due to manual intervention. This application uses real-time online impedance scanning, which enables rapid impedance identification; (3) Currently, the control strategy parameters of the PLL phase-locked loop are fixed and cannot be changed, which can easily lead to negative damping in the system. This application identifies the negative damping by real-time identification of the system impedance, and then uses adaptive variable step-size iterative parameter adjustment of the phase-locked loop until the negative damping is converted to positive damping, thus eliminating the negative damping and the oscillation energy source; (4) Currently, the current loop gain parameters are fixed and cannot be changed, which can easily lead to resonance due to matching with the grid impedance. This application identifies each resonance point by impedance scanning, and then uses adaptive variable step-size iterative parameter adjustment of the current loop gain to increase the bandwidth and eliminate the resonance point.

[0078] like Figure 2 As shown, based on the above-described method embodiments, one embodiment of this application provides a wideband oscillation suppression device for a converter, including: a data acquisition module 201, a judgment module 202, and an execution module 203; The acquisition module 201 is used to acquire the equivalent impedance of the converter at each frequency after a preset interference signal is injected; the equivalent impedance includes: the fundamental equivalent impedance at the fundamental frequency and the broadband equivalent impedance at each interference frequency. The judgment module 202 is used to determine the damping characteristics of the converter based on the real part of the fundamental equivalent impedance. The execution module 203 is configured to, if the damping characteristic is a positive damping characteristic and the imaginary part of at least one of the wideband equivalent impedances satisfies a preset resonance criterion, determine the resonant frequency band between the power grid and the converter from all the interference frequencies, and adjust the current control loop parameters of the converter according to the resonant frequency band until the imaginary part of all the wideband equivalent impedances no longer satisfies the preset resonance criterion, so as to achieve wideband oscillation suppression; wherein, the preset resonance criterion is determined based on the reactance characteristics of the wideband equivalent impedance.

[0079] Furthermore, in some embodiments of this application, the phase-locked loop parameters include: a first proportional gain and a first integral gain of the phase-locked loop; the execution module 203 is further configured to, after determining the damping characteristic of the converter based on the real part of the fundamental equivalent impedance, if the damping characteristic is a negative damping characteristic, adjust the phase-locked loop parameters of the converter based on the real part of the fundamental equivalent impedance to adjust the fundamental equivalent impedance until the damping characteristic is a positive damping characteristic.

[0080] Further, in some embodiments of this application, the execution module 203 includes: a first calculation unit, a first adjustment unit, and a first update unit; the execution module 203 is also used to adjust the phase-locked loop parameters of the converter according to the real part of the fundamental equivalent impedance, including: The first calculation unit is used to determine the first adjustment step size within the current adjustment period based on the real part of the fundamental equivalent impedance; The first adjustment unit is used to adjust the first proportional gain by a reduction based on the first adjustment step size; The first update unit is used to update the first integral gain according to the adjusted first proportional gain, so as to adjust the phase-locked loop parameters.

[0081] Further, in some embodiments of this application, the first calculation unit is configured to determine a first adjustment step size within the current adjustment period based on the real part of the fundamental equivalent impedance, including: Based on the real part of the fundamental equivalent impedance and a preset inertial time constant, an adjustment coefficient characterizing the oscillation energy intensity of the current system is calculated; wherein, the inertial time constant is obtained by calibration according to the quantization range of the real part; Multiply the adjustment coefficient by the preset maximum reduction ratio to obtain the first adjustment step size within the current adjustment cycle.

[0082] Further, in some embodiments of this application, the execution module 203 includes: a construction unit, a second calculation unit, a second adjustment unit, and a second update unit; the execution module 203 is used to determine the resonant frequency band between the power grid and the converter from all the interference frequencies, and to adjust the current control loop parameters of the converter according to the resonant frequency band, including: The filtering unit is used to filter out the first broadband equivalent impedance whose imaginary part satisfies the preset resonance criterion from all the broadband equivalent impedances, and to construct the resonance frequency band according to the interference frequency corresponding to all the first broadband equivalent impedances. The second calculation unit is used to calculate the target resonant angular velocity based on the largest interference frequency in the resonant frequency band, and to determine the target bandwidth threshold of the current control loop based on the target resonant angular velocity. The second adjustment unit is used to obtain the actual bandwidth frequency of the current control loop in the current adjustment cycle, and adjust the second proportional gain according to the actual bandwidth frequency and the target bandwidth threshold. The second update unit is used to synchronously update the second integral gain based on the adjusted second proportional gain, so that the resonant frequency band is within the active control range of the current control loop; wherein the active control range is determined by the actual bandwidth frequency.

[0083] Furthermore, in some embodiments of this application, the second adjustment unit is configured to adjust the second proportional gain according to the actual bandwidth frequency and the target bandwidth threshold, including: Calculate the frequency deviation between the actual bandwidth frequency and the target bandwidth threshold, and determine the second adjustment step size of the second proportional gain within the current adjustment period; When the actual bandwidth frequency is less than the target bandwidth threshold, the second proportional gain is increased based on the second adjustment step size so that the actual bandwidth frequency is not less than the target bandwidth threshold.

[0084] Further, in some embodiments of this application, the acquisition module 201 includes: an acquisition unit, an extraction unit, and a third calculation unit; the acquisition module 201 is used to acquire the equivalent impedance of the converter at various frequencies after a preset interference signal is injected, including: The acquisition unit is used to acquire the electrical signal output by the converter under the influence of the interference signal; The extraction unit is used to extract electrical signal components corresponding to each frequency from the electrical signal; wherein, the electrical signal components include: voltage components and current components corresponding to the frequency; The third calculation unit is used to calculate the corresponding equivalent impedances based on the ratio of the voltage component to the current component.

[0085] In summary, the broadband oscillation suppression device for converters provided in this application has the following advantages compared to the prior art: This application injects a preset interference signal into the converter control signal to excite the converter at multiple frequencies, and calculates the equivalent impedance based on the voltage and current responses at each frequency point, thereby achieving online acquisition of the converter's impedance characteristics within the fundamental frequency and broadband range. Furthermore, by judging the damping characteristics based on the real part of the fundamental equivalent impedance, and further, by judging the imaginary part of the broadband equivalent impedance, the frequency range where the converter and the grid satisfy the resonance condition is identified. By adjusting the current control loop parameters to change the bandwidth of the current control loop, the equivalent impedance within the frequency range is changed from capacitive to inductive characteristics, thereby breaking the impedance coupling resonance condition between the grid and the converter. Through the above methods, frequency-segmented adjustment based on impedance characteristics is achieved, improving the accuracy of broadband oscillation suppression.

[0086] It is understood that the above-described device embodiments correspond to the method embodiments of this application, and can implement the wideband oscillation suppression method for converters provided by any of the above-described method embodiments of this application.

[0087] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided in this application, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0088] Based on the above embodiments of the wideband oscillation suppression method for converters, another embodiment of this application provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the wideband oscillation suppression method for converters according to any embodiment of this application.

[0089] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete this application. The one or more module units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0090] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0091] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0092] Based on the above-described method embodiments, another embodiment of this application provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the wideband oscillation suppression method for a converter described in any of the above-described method embodiments of this application.

[0093] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

Claims

1. A method of wideband oscillation suppression for a current transformer, comprising: include: The equivalent impedance of the converter at each frequency after a preset interference signal is injected is obtained. The equivalent impedance includes: the fundamental equivalent impedance at the fundamental frequency and the broadband equivalent impedance at each interference frequency. The damping characteristics of the converter are determined based on the real part of the fundamental equivalent impedance. If the damping characteristic is a positive damping characteristic, and the imaginary part of at least one of the wideband equivalent impedances satisfies the preset resonance criterion, the resonant frequency band between the power grid and the converter is determined from all the interference frequencies, and the current control loop parameters of the converter are adjusted according to the resonant frequency band until the imaginary part of all the wideband equivalent impedances no longer satisfies the preset resonance criterion, so as to achieve wideband oscillation suppression; wherein, the preset resonance criterion is determined based on the reactance characteristics of the wideband equivalent impedance.

2. The method of claim 1, wherein the variable frequency converter is a voltage source converter. After determining the damping characteristics of the converter based on the real part of the fundamental equivalent impedance, the method further includes: if the damping characteristics are negative damping characteristics, adjusting the phase-locked loop parameters of the converter based on the real part of the fundamental equivalent impedance to adjust the fundamental equivalent impedance until the damping characteristics are positive damping characteristics.

3. The method of claim 2, wherein the step of applying a high frequency signal to the transformer is performed by applying a high frequency signal to the primary winding of the transformer. The phase-locked loop (PLL) parameters include: a first proportional gain and a first integral gain of the PLL; adjusting the PLL parameters of the converter according to the real part of the fundamental equivalent impedance includes: The first adjustment step size within the current adjustment cycle is determined based on the real part of the fundamental equivalent impedance. The first proportional gain is reduced based on the first adjustment step size; The first integral gain is updated based on the adjusted first proportional gain to adjust the phase-locked loop parameters.

4. The method of claim 3, wherein the frequency of the reference signal is varied in response to a change in the frequency of the input signal. Determining the first adjustment step size within the current adjustment cycle based on the real part of the fundamental equivalent impedance includes: Based on the real part of the fundamental equivalent impedance and a preset inertial time constant, an adjustment coefficient characterizing the oscillation energy intensity of the current system is calculated; wherein, the inertial time constant is obtained by calibration according to the quantization range of the real part; Multiply the adjustment coefficient by the preset maximum reduction ratio to obtain the first adjustment step size within the current adjustment cycle.

5. The broadband oscillation suppression method for a converter as described in claim 1, characterized in that, The current control loop parameters include: the second proportional gain and the second integral gain of the current control loop; determining the resonant frequency band between the power grid and the converter from all the interference frequencies, and adjusting the current control loop parameters of the converter according to the resonant frequency band, includes: From all the broadband equivalent impedances, select the first broadband equivalent impedance whose imaginary part satisfies the preset resonance criterion, and construct the resonance frequency band based on the interference frequencies corresponding to all the first broadband equivalent impedances; Calculate the target resonant angular velocity based on the largest interference frequency in the resonant frequency band, and determine the target bandwidth threshold of the current control loop based on the target resonant angular velocity; Obtain the actual bandwidth frequency of the current control loop within the current adjustment cycle, and adjust the second proportional gain according to the actual bandwidth frequency and the target bandwidth threshold; Based on the adjusted second proportional gain, the second integral gain is updated synchronously to ensure that the resonant frequency band is within the active control range of the current control loop; wherein the active control range is determined by the actual bandwidth frequency.

6. The broadband oscillation suppression method for a converter as described in claim 5, characterized in that, The step of adjusting the second proportional gain according to the actual bandwidth frequency and the target bandwidth threshold includes: Calculate the frequency deviation between the actual bandwidth frequency and the target bandwidth threshold, and determine the second adjustment step size of the second proportional gain within the current adjustment period; When the actual bandwidth frequency is less than the target bandwidth threshold, the second proportional gain is increased based on the second adjustment step size so that the actual bandwidth frequency is not less than the target bandwidth threshold.

7. A broadband oscillation suppression method for a converter as described in any one of claims 1 to 6, characterized in that, The step of obtaining the equivalent impedance of the converter at various frequencies after the preset interference signal is injected includes: The electrical signal output by the converter under the influence of the interference signal is collected; Extract electrical signal components corresponding to each frequency from the electrical signal; wherein, the electrical signal components include: voltage components and current components corresponding to the frequency; The corresponding equivalent impedances are calculated based on the ratio of the voltage component to the current component.

8. A broadband oscillation suppression device for a converter, characterized in that, include: The module consists of a data acquisition module, a judgment module, and an execution module. The acquisition module is used to acquire the equivalent impedance of the converter at various frequencies after a preset interference signal is injected. The equivalent impedance includes: the fundamental equivalent impedance at the fundamental frequency and the broadband equivalent impedance at each interference frequency. The judgment module is used to determine the damping characteristics of the converter based on the real part of the fundamental equivalent impedance. The execution module is configured to, if the damping characteristic is a positive damping characteristic and the imaginary part of at least one of the wideband equivalent impedances satisfies a preset resonance criterion, determine the resonant frequency band between the power grid and the converter from all the interference frequencies, and adjust the current control loop parameters of the converter according to the resonant frequency band until the imaginary part of all the wideband equivalent impedances no longer satisfies the preset resonance criterion, so as to achieve wideband oscillation suppression; wherein, the preset resonance criterion is determined based on the reactance characteristics of the wideband equivalent impedance.

9. A terminal device, characterized in that, The device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements a wideband oscillation suppression method for a converter as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed, it controls the device on which the computer-readable storage medium is located to perform a wideband oscillation suppression method for a converter as described in any one of claims 1 to 7.

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