A method, medium and system for correcting additional damping control signal of a converter

Abstract

The present invention discloses a method, medium, and system for correcting an added damping control signal for a converter, comprising: determining, based on an actual synchronous frequency, each element of a transfer function matrix corresponding to the actual synchronous frequency using a pre-fitted calculation formula corresponding to each element, wherein the synchronous frequency includes a subsynchronous frequency and a supersynchronous frequency; calculating, based on each element, the phase and amplitude of each element at the actual synchronous frequency using a relationship between the transfer function matrix corresponding to the actual synchronous frequency and the phase and amplitude; and correcting an input added damping control signal using the phase and amplitude of each element at the actual synchronous frequency to control the output current of the converter. The converter of the present invention accurately tracks the added damping control signal based on the current generated by the corrected signal.

Description

Technical Field

[0001] The present invention relates to the technical field of additional damping control signal correction of a converter, and in particular to an additional damping control signal correction method, medium and system for a converter. Background Art

[0002] New power systems, from source to grid to load, are increasingly incorporating high proportions of renewable energy and power electronics. However, interactions between power electronics devices like wind turbines, photovoltaics, and flexible direct current transmission (HVDC), and between them and the AC / DC grid, can cause broadband oscillations ranging from several Hz to several kHz, seriously threatening the safe and stable operation of power systems. Therefore, research on suppressing broadband oscillations is of great practical significance.

[0003] Previous research has shown that damping control can be used to generate a reference current signal, which can be used to control the converter to inject oscillation-frequency current to improve system damping and thereby suppress oscillations. This suppression method typically requires dedicated converter equipment to generate the oscillation-frequency current, but this solution is expensive. Therefore, existing converter equipment in the system, such as energy storage converters and flexible AC transmission systems (FACTS), can be retrofitted and upgraded to generate sub- / supersynchronous currents for oscillation suppression. Energy storage and FACTS devices are primarily designed to operate at the power frequency (50 Hz) and are not capable of generating currents at other frequencies. Therefore, the control method for this additional current must take into account the converter's existing functionality. The injected current must also accurately track the amplitude and phase of the reference current signal to achieve oscillation suppression. Currently, existing research typically incorporates damping control into the existing converter control, with the generated reference signal directly superimposed on the converter's modulated wave signal. However, since the dynamic characteristics of the converter itself are not taken into account when superimposed on the modulated wave signal, the control link originally set for the industrial frequency has a steady-state error when used for current control at other frequencies; the additional current control link also does not form a closed loop, making it difficult for the actual current generated to accurately track the additional current instruction. Summary of the Invention

[0004] Embodiments of the present invention provide a method, medium, and system for correcting an additional damping control signal of a converter, so as to solve the problem of error in the correction of the additional damping control signal in the prior art.

[0005] In a first aspect, a method for correcting an additional damping control signal of a converter is provided, comprising:

[0006] According to the actual synchronization frequency, each element of the transfer function matrix corresponding to the actual synchronization frequency is determined using a calculation formula corresponding to each element pre-fitted, wherein the synchronization frequency includes: a subsynchronous frequency and a supersynchronous frequency;

[0007] According to each of the elements, the phase and amplitude of each element at the actual synchronization frequency are calculated using a relationship between a transfer function matrix corresponding to the actual synchronization frequency and the phase and amplitude;

[0008] The input additional damping control signal is corrected by using the phase and amplitude of each element at the actual synchronous frequency to control the output current of the converter.

[0009] In a second aspect, a computer-readable storage medium is provided, on which computer program instructions are stored; when the computer program instructions are executed by a processor, the additional damping control signal correction method of the converter as described in the embodiment of the first aspect above is implemented.

[0010] In a third aspect, a system for correcting an additional damping control signal of a converter is provided, comprising:

[0011] An element determination module is used to determine each element of the transfer function matrix corresponding to the actual synchronization frequency using a pre-fitted calculation formula corresponding to each element according to the actual synchronization frequency, wherein the synchronization frequency includes: a subsynchronous frequency and a supersynchronous frequency;

[0012] A parameter determination module is used to calculate the phase and amplitude of each element at the actual synchronization frequency based on each element using the relationship between the transfer function matrix corresponding to the actual synchronization frequency and the phase and amplitude;

[0013] The signal correction module is used to correct the input additional damping control signal by adopting the phase and amplitude of each element at the actual synchronous frequency to control the output current of the converter.

[0014] In this way, in an embodiment of the present invention, the elements in the transfer function matrix of the converter can be determined according to the calculation formula corresponding to the pre-fitted elements, and then the phase and amplitude of the elements can be determined through the relationship between the transfer function matrix and the phase and amplitude, so as to perform amplitude and phase correction on the additional damping control signal, so that the current generated by the converter according to the corrected signal can accurately track the additional damping control signal, thereby reducing errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0016] Figure 1is a flow chart of a method for correcting an additional damping control signal of a converter according to an embodiment of the present invention;

[0017] Figure 2 It is a schematic diagram of the typical converter control structure and the location of the additional damping control signal;

[0018] Figure 3 is a correction control block diagram of a method for correcting an additional damping control signal of a converter according to an embodiment of the present invention;

[0019] Figure 4 1 is a structural block diagram of an additional damping control signal correction system for a converter according to an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of the control effect of 20Hz current when the additional damping control signal is 20 / 80Hz;

[0021] Figure 6 This is a schematic diagram of the control effect of 80Hz current when the additional damping control signal is 20 / 80Hz. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0023] The embodiment of the present invention discloses a method for correcting an additional damping control signal of a converter. Figure 1 As shown, the method includes the following steps:

[0024] Step S101: According to the actual synchronization frequency, each element of the transfer function matrix corresponding to the actual synchronization frequency is determined using the pre-fitted calculation formula corresponding to each element.

[0025] The synchronous frequency includes subsynchronous frequency and supersynchronous frequency.

[0026] Step S102: According to each element, the phase and amplitude of each element at the actual synchronization frequency are calculated using the relationship between the transfer function matrix corresponding to the actual synchronization frequency and the phase and amplitude.

[0027] Based on the transfer function matrix obtained by identification, the error of the output current relative to the input signal when the additional damping control signal is input can be analyzed, so that the amplitude and phase of the reference signal can be corrected, and the corrected signal is added to the converter current inner loop control, so that the converter output current can track the additional damping control signal before correction.

[0028] Assume that the reference value of the current output signal is expressed as:

[0029]

[0030] Δi fsref 、 They are respectively the reference value of the current test signal at the subsynchronous frequency and the reference value of the current test signal at the supersynchronous frequency.

[0031] According to the transfer function matrix The obtained additional damping control signal, that is, the injected current should be corrected to:

[0032]

[0033] For the convenience of derivation, the calculation is performed in phasor form. The relationship between the transfer function matrix, phase and amplitude corresponding to the actual synchronization frequency is:

[0034]

[0035] in, Represents the phase of each element, R 11 ~R 22 Represents the amplitude of each element respectively. The transfer function matrix corresponding to the actual synchronization frequency is represented by The inverse matrix of .

[0036] Step S103: using the phase and amplitude of each element corresponding to the actual synchronous frequency to correct the input additional damping control signal to control the output current of the converter.

[0037] Among them, the method of generating the additional damping control signal can refer to the patent application with application number 202011281961.6 "Adaptive damping control method and device for wind power subsynchronous oscillation", which will not be repeated here.

[0038] Based on the phase and amplitude of each element at the actual synchronous frequency obtained above, it is assumed that the phasor of the desired current output signal is and The phase of the power frequency voltage phasor at the converter grid connection point (i.e. the grid voltage phase) is First, the current phase is corrected (i.e., the phase of the power frequency voltage phasor at the converter grid connection point is subtracted), and the conjugate of the supersynchronous component is taken to obtain the following formula:

[0039]

[0040] in, Represents the correction value. The corrected current is multiplied by the inverse matrix of the transfer function, and the following expression is obtained:

[0041]

[0042] The actual given reference current signal should be the uncorrected current phasor. In practical applications, it is necessary to extract the phase and amplitude of the signal in real time. and I s / I c The cross terms of the above matrix can be obtained directly by using a phase-locked loop and d / q transformation. The cross terms of the above matrix can be obtained by multiplying the power frequency voltage phase-locked result by 2 minus the coupling term. For example, the frequency of the phasor in the time domain is the subsynchronous frequency, and the phase of the supersynchronous frequency phasor is also needed. Considering that the subsupersynchronous frequency has a coupling relationship ω s +ω c =2ω0,ω s and ω c They represent subsynchronous and supersynchronous frequencies respectively, and can be calculated using the following relationship:

[0043]

[0044] in, is the output of the power frequency voltage phase-locked loop, is the output of the super synchronous current phase locked loop.

[0045] Therefore, The corrected additional damping control signal is rewritten as:

[0046]

[0047] in, represents the corrected additional damping control signal, represents the phase of the subsynchronous component of the additional damping control signal extracted by the subsynchronous current phase-locked loop, represents the phase of the super-synchronous component of the additional damping control signal extracted by the super-synchronous current phase-locked loop, It represents the phase of the power frequency voltage phasor of the converter grid connection point extracted by the power frequency voltage phase-locked loop, I s represents the amplitude of the subsynchronous component of the additional damping control signal extracted by the subsynchronous current phase-locked loop and obtained by d / q transformation, I c It represents the amplitude of the supersynchronous component of the additional damping control signal extracted by the supersynchronous current phase-locked loop and obtained by d / q transformation.

[0048] The above method can be Figure 3 The control structure of the correction control is implemented as shown.

[0049] Preferably, before step S101, the method of the embodiment of the present invention further includes:

[0050] 1. Two sets of current test signals with the same preset synchronous frequency are respectively injected into the converter, so that the converter outputs two sets of current output signals and two sets of converter grid-connected point power frequency voltage signals according to the two sets of current test signals.

[0051] The current test signals are generated by simulating the process from generation to suppression of current oscillation. The amplitudes of the subsynchronous components and supersynchronous components of the two sets of current test signals are different and linearly independent.

[0052] Multiple subsynchronous and supersynchronous frequencies are determined based on the frequency range of the current being injected. The process from current oscillation generation to suppression consists of three stages: divergence, constant amplitude, and convergence. The current test signal is a three-phase symmetrical current test signal. Using phase A as an example, the following is an illustration:

[0053] (1) 0~t1 is the divergence stage, and the expression of the current test signal in this stage is:

[0054]

[0055] (2) t1~t2 is the constant amplitude stage. The expression of the current test signal in this stage is:

[0056]

[0057] (3) t2~t3 is the convergence stage, and the expression of the current test signal in this stage is:

[0058]

[0059] Among them, ω s and ω c denote subsynchronous and supersynchronous frequencies, ω s =2πf s , the supersynchronous frequency ω is symmetric about the fundamental wave c =2πf c , f s and f c denote subsynchronous and supersynchronous frequencies, ω s and ω c is the corresponding angular frequency, ω s +ω c =100. I s and I c They represent the amplitudes of the subsynchronous and supersynchronous components respectively, which generally do not exceed 5% of the power frequency amplitude. and denote the phases of subsynchronous and supersynchronous components, respectively, ks1 and k s2 Indicates the signal amplitude divergence rate, k c1 and k c2 Indicates the signal amplitude attenuation rate.

[0060] It can be seen from the above expressions that the response characteristics of the converter at sub-synchronous / super-synchronous frequencies can be measured by the current test signal, so that the transfer function matrix equation can be established according to the response characteristics.

[0061] In specific applications, the above current test signal is discretely sampled according to the sampling rate of the control system, and then injected into the converter control link to record Figure 2 Medium current output signal i abc and the power frequency voltage signal u at the grid connection point of the converter gabc . Figure 2 A typical dual-loop control structure of the converter is shown, where the outer loop controls power or voltage and the inner loop controls current.

[0062] The subsynchronous and supersynchronous components of the two sets of current test signals have different amplitudes and are linearly independent. Therefore, at the same frequency, a current test signal with the same amplitudes of the subsynchronous and supersynchronous components is injected first, the output signal is recorded, and then the amplitudes of the subsynchronous and supersynchronous components of the current test signal are modified, and the signal is injected again and the output signal is recorded.

[0063] Simulate multiple subsynchronous and supersynchronous frequencies as needed. For example, within a preset range (e.g., 5-45 Hz), change the subsynchronous frequency ω at a given rate (e.g., 1 Hz / time). s , repeat the above steps.

[0064] 2. Solve the transfer function matrix equation based on the two sets of current test signals, two sets of current output signals and two sets of power frequency voltage signals at the converter grid connection point corresponding to each preset synchronous frequency to obtain the transfer function matrix corresponding to each preset synchronous frequency.

[0065] According to the frequency coupling characteristics of the converter, it can be assumed that the current test signal i sabc and the actual current output signal i abc There is a transfer function matrix as follows:

[0066]

[0067] Among them, the left side of the equal sign represents the current output signal i abc The vector composed of the secondary / super synchronous current phasors, the rightmost is the current test signal i sabc The vector of the intermediate / super synchronous current phasors, G 11 (s)~G 22(s) represents the four transfer functions, s is the complex frequency, and the superscript * represents the conjugate.

[0068] When s Change within the set range (assuming all ω s The composition set W N ), after obtaining all the data, the transfer function matrix of each frequency can be calculated in turn. s First, process the first set of data and the current test signal i sabc , actual current output signal i abc and the power frequency voltage signal u at the grid connection point of the converter gabc After Fourier analysis of the time domain data to obtain frequency domain data, the current and voltage phasors are calculated using the frequency domain data. Then, the phase angle of the power frequency voltage phasor is subtracted from the current phasor to obtain the frequency ω. s and ω c The phasor Δi fsref1 、 and Δi fs1 、 Among them, ω c The corresponding phasor should be the conjugate phasor. Then process the second set of data and measure the current test signal i sabc , actual current output signal i abc and the power frequency voltage signal u at the grid connection point of the converter gabc After Fourier analysis of the time domain data to obtain frequency domain data, the current and voltage phasors are calculated using the frequency domain data. Then, the phase angle of the power frequency voltage phasor is subtracted from the current phasor to obtain the frequency ω. s and ω c The phasor Δi fsref2 、 and Δi fs2 、 Among them, ω c The corresponding phasors should be conjugate phasors.

[0069] Based on the above theoretical analysis, the specific transfer function matrix equation is as follows:

[0070]

[0071] Among them, Δi fs1,k and Δi fs2,k are the reference values ​​of the two sets of current output signals at the kth subsynchronous frequency, Δi fsref1,k and Δi fsref2,k are the reference values ​​of two sets of current test signals at the kth subsynchronous frequency, and are the reference values ​​of the two sets of current output signals at the kth supersynchronous frequency, and are the reference values ​​of two sets of current test signals at the kth supersynchronous frequency, They represent the transfer function matrix corresponding to the kth synchronization frequency, s k =jω s,k ,ω s,k represents the kth secondary synchronization frequency, and j represents an imaginary number.

[0072] Specifically, the reference values ​​of the two groups of current output signals at the subsynchronous frequency are respectively equal to the frequency domain phasor of the first group of current output signals at the subsynchronous frequency minus the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals, and the frequency domain phasor of the second group of current output signals minus the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals.

[0073] Specifically, the reference values ​​of the two groups of current test signals at the subsynchronous frequency are respectively equal to the frequency domain phasor of the first group of current test signals at the subsynchronous frequency minus the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals, and the frequency domain phasor of the second group of current test signals minus the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals.

[0074] Specifically, the reference values ​​of the two groups of current output signals at the super-synchronous frequency are respectively equal to the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the first group of current output signals at the super-synchronous frequency, and the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the second group of current output signals.

[0075] Specifically, the reference values ​​of the two groups of current test signals at the super-synchronous frequency are respectively equal to the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the first group of current test signals at the super-synchronous frequency, and the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the second group of current test signals.

[0076] The above process is repeated for each preset synchronization frequency, and the transfer function matrix corresponding to all preset synchronization frequencies can be obtained by solving the transfer function matrix equation.

[0077] 3. By fitting the elements at the same position in the transfer function matrix determined by all preset synchronous frequencies, a calculation formula corresponding to the elements at the same position is obtained.

[0078] Specifically, this step includes the following process:

[0079] (1) Establish a calculation formula corresponding to each element of the transfer function matrix corresponding to each preset synchronization frequency.

[0080] Specifically, the calculation formula corresponding to the element is:

[0081]

[0082] Among them, G(s) represents an element, a1~a n , b0~b m Both represent coefficients.

[0083] (2) According to the calculation formula corresponding to the elements, the coefficient fitting equation of the elements at the same position in the transfer function matrix corresponding to each preset synchronization frequency is obtained.

[0084] As mentioned above k =jω s,k The transfer function matrix is k=1,2,……,N. Assume that the order n and m of the denominator and numerator of the general formula of the element are known, the coefficient vector is X, and G 11 (jω s,k ) as an example, the calculation formula of the element is transformed into G(s) = -(A-1) × G(s) + B, A is the denominator of the calculation formula of the element, and B is the numerator of the calculation formula of the element. Then, the following formula can be obtained:

[0085] G 11 (jω s,k )=A(jω s,k )·X.

[0086] According to ω s,k The results of different values ​​are expanded to obtain G 11 The following matrix:

[0087]

[0088] Recorded as

[0089] Through the above analysis, the coefficient fitting equation can be summarized as follows:

[0090]

[0091] Among them, G ij (jω s,k ) represents the element in the i-th row and j-th column of the transfer function matrix corresponding to the k-th preset synchronization frequency.

[0092] (3) Solve the coefficient fitting equation through the multivariate linear regression algorithm to obtain the coefficients of the calculation formula corresponding to the elements.

[0093] Constructed based on the result of the previous step and X, we can use the existing multiple linear regression algorithm to get X.

[0094] In practical applications, it is often impossible to determine the values ​​of n and m in advance. Therefore, the error minimization principle is used to determine the values ​​of n and m. Specifically, this step includes the following process:

[0095] ① Assume the values ​​of n and m, and use the coefficient fitting equation to calculate the coefficients.

[0096] ② By substituting the coefficients obtained by fitting calculation into the calculation formula corresponding to the elements, the elements at the same position in the transfer function matrix corresponding to each preset synchronization frequency are calculated.

[0097] ③ By solving the transfer function matrix equation, the elements at the same position in the transfer function matrix corresponding to each preset synchronization frequency are calculated.

[0098] That is, this step is to calculate the elements in the transfer function matrix by collecting the actual injection current, output current, and power frequency voltage of the converter grid connection point.

[0099] ④ Calculate the total error of the elements at the same position in the transfer function matrix corresponding to all preset synchronization frequencies obtained by the calculation formula corresponding to the elements and by solving the transfer function matrix equation.

[0100] Specifically, the total error is calculated as:

[0101]

[0102] Among them, ε represents the total error, G ij * (jω s,k ) represents the element in the i-th row and j-th column of the transfer function matrix corresponding to the k-th preset synchronization frequency obtained by the calculation formula corresponding to the element.

[0103] ⑤ With the goal of ensuring that each coefficient is not zero and the total error is minimized, determine the values ​​of n and m and the corresponding coefficients.

[0104] Therefore, this step can further fit the transfer function curve represented by the calculation formula of the current element by taking the values ​​of the elements of the transfer function of the discrete frequency points in the previous step, thereby obtaining the elements of the transfer function of the unmeasured frequency points, so that the obtained elements can be used in the aforementioned step S101.

[0105] An embodiment of the present invention further discloses a computer-readable storage medium having computer program instructions stored thereon; when the computer program instructions are executed by a processor, the method for correcting the additional damping control signal of the converter as described in the above embodiment is implemented.

[0106] The embodiment of the present invention also discloses a converter additional damping control signal correction system, such as Figure 4 As shown, the system includes:

[0107] The element determination module 401 is configured to determine, according to the actual synchronization frequency, each element of the transfer function matrix corresponding to the actual synchronization frequency using a pre-fitted calculation formula corresponding to each element.

[0108] The synchronous frequency includes subsynchronous frequency and supersynchronous frequency.

[0109] The parameter determination module 402 is configured to calculate the phase and amplitude of each element at the actual synchronization frequency based on each element using the relationship between the transfer function matrix corresponding to the actual synchronization frequency and the phase and amplitude.

[0110] The signal correction module 403 is configured to correct the input additional damping control signal using the phase and amplitude of each element at the actual synchronous frequency to control the output current of the converter.

[0111] Preferably, the system further comprises:

[0112] The signal injection and output module is used to inject two sets of current test signals with the same preset synchronous frequency into the converter respectively before the step of determining each element of the transfer function matrix corresponding to the actual synchronous frequency using the calculation formula corresponding to each element fitted in advance, so that the converter outputs two sets of current output signals and two sets of converter grid-connected point power frequency voltage signals respectively according to the two sets of current test signals.

[0113] The current test signal is generated by simulating the process from generation to suppression of current oscillation, and the amplitudes of the subsynchronous components and supersynchronous components of the two sets of current test signals are different and linearly independent.

[0114] A matrix solving module is used to solve the transfer function matrix equation based on two sets of current test signals, two sets of current output signals and two sets of power frequency voltage signals at the grid connection point of the converter corresponding to each preset synchronous frequency, so as to obtain the transfer function matrix corresponding to each preset synchronous frequency;

[0115] The general formula fitting module is used to fit the elements at the same position in the transfer function matrix corresponding to all preset synchronous frequencies to obtain the calculation general formula corresponding to the elements at the same position.

[0116] This system is used to implement the correction method of the above embodiment, which will not be described in detail here.

[0117] Application Examples

[0118] The above control method is applied to the energy storage converter with active and reactive power control in the outer loop. Figure 1 The process shown generates 20 / 80Hz current. Figure 5 and Figure 6 As shown, it can be seen that the output current can basically coincide with the input current waveform after about 0.3s, achieving the control effect.

[0119] In summary, the embodiments of the present invention do not require knowledge of the detailed control parameters of the converter, and do not require modeling of the converter. By establishing a transfer function matrix model of the converter at the sub / supersynchronous frequency, the tracking error of the current reference signal at the sub / supersynchronous frequency is analyzed, and the impact of the converter's power frequency dynamics on the sub / supersynchronous current is taken into account, so that the converter can accurately track the additional damping control instructions, so that the existing converters in the system (including but not limited to energy storage converters, FACTS converters, etc.) can also be used as the actuator of the damping controller, thereby achieving oscillation suppression, saving costs compared to additional devices.

[0120] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for correcting an additional damping control signal of a converter, characterized in that: include: According to the actual synchronization frequency, each element of the transfer function matrix corresponding to the actual synchronization frequency is determined using a calculation formula corresponding to each element pre-fitted, wherein the synchronization frequency includes: a subsynchronous frequency and a supersynchronous frequency; According to each of the elements, the phase and amplitude of each element at the actual synchronization frequency are calculated using a relationship between a transfer function matrix corresponding to the actual synchronization frequency and the phase and amplitude; The input additional damping control signal is corrected using the phase and amplitude of each element at the actual synchronous frequency to control the output current of the converter; Before the step of determining each element of the transfer function matrix corresponding to the actual synchronization frequency using the calculation formula corresponding to each pre-fitted element, the method further includes: Injecting two sets of current test signals having the same preset synchronous frequency into the converter, respectively, so that the converter outputs two sets of current output signals and two sets of converter grid-connected point power frequency voltage signals, respectively, according to the two sets of current test signals, wherein the current test signals are generated by simulating the process from generation to suppression of current oscillation, and the amplitudes of subsynchronous components and supersynchronous components of the two sets of current test signals are different and linearly independent; Solve the transfer function matrix equation based on the two sets of current test signals, the two sets of current output signals, and the two sets of power frequency voltage signals at the grid connection point of the converter corresponding to each preset synchronous frequency to obtain the transfer function matrix corresponding to each preset synchronous frequency; By fitting the elements at the same position in the transfer function matrix corresponding to all preset synchronization frequencies, a calculation formula corresponding to the elements at the same position is obtained; The transfer function matrix equation is: ； in, and Respectively k The reference values ​​of the two sets of current output signals at the sub-synchronous frequency, and Respectively k Reference values ​​of two sets of current test signals at sub-synchronous frequencies, and Respectively k The reference values ​​of the two sets of current output signals at super synchronous frequency, and Respectively k The reference values ​​of two sets of current test signals at super synchronous frequency, Respectively represent k The transfer function matrix corresponding to the synchronization frequency is: , Indicates the k Subsynchronous frequency, j Represents an imaginary number.

2. The method for correcting the additional damping control signal of a converter according to claim 1, wherein: The reference values ​​of the two groups of current output signals at the subsynchronous frequency are respectively equal to the frequency domain phasor of the first group of current output signals at the subsynchronous frequency minus the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals, and the frequency domain phasor of the second group of current output signals minus the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals; The reference values ​​of the two groups of current test signals at the subsynchronous frequency are respectively equal to the frequency domain phasor of the first group of current test signals at the subsynchronous frequency minus the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals, and the frequency domain phasor of the second group of current test signals minus the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals; The reference values ​​of the two groups of current output signals at the supersynchronous frequency are respectively equal to the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the first group of current output signals at the supersynchronous frequency, and the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the second group of current output signals; The reference values ​​of the two groups of current test signals at the super-synchronous frequency are respectively equal to the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the first group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the first group of current test signals at the super-synchronous frequency, and the conjugate phasor obtained by subtracting the phase angle of the frequency domain phasor of the second group of converter grid-connected power frequency voltage signals from the frequency domain phasor of the second group of current test signals.

3. The method for correcting the additional damping control signal of a converter according to claim 1, characterized in that: The step of fitting to obtain the calculation formula corresponding to the elements at the same position includes: Establishing a calculation formula corresponding to each element of the transfer function matrix corresponding to each preset synchronization frequency; Obtaining coefficient fitting equations for elements at the same position in the transfer function matrix corresponding to each preset synchronization frequency according to the calculation formula corresponding to the elements; The coefficient fitting equation is solved by a multiple linear regression algorithm to obtain the coefficients of the calculation formula corresponding to the element.

4. The method for correcting the additional damping control signal of a converter according to claim 3, wherein: The step of solving the coefficient fitting equation by a multiple linear regression algorithm to obtain the coefficients of the calculation formula corresponding to the element includes: Assumptions n and m The coefficients are obtained by fitting the coefficient fitting equation; By substituting the coefficients obtained by fitting calculation into the calculation formula corresponding to the elements, the elements at the same position in the transfer function matrix corresponding to each preset synchronization frequency are calculated; By solving the transfer function matrix equation, the elements at the same position in the transfer function matrix corresponding to each preset synchronization frequency are calculated; Calculating the total error of the elements at the same position in the transfer function matrices corresponding to all preset synchronous frequencies obtained by the calculation formula corresponding to the elements and by solving the transfer function matrix equation; With the purpose of each coefficient not being 0 and the total error being minimum, determine n and m The value of and the corresponding coefficient; Wherein, the calculation formula of the total error is: ； in, represents the total error, Indicates the first element obtained by the calculation formula corresponding to the element k The first one in the transfer function matrix corresponding to the preset synchronization frequency i Rank j Elements of a column.

5. The method for correcting the additional damping control signal of a converter according to claim 1, wherein: The relationship between the transfer function matrix, phase and amplitude corresponding to the actual synchronization frequency is: ； in, The transfer function matrix corresponding to the actual synchronization frequency is represented by The inverse matrix of ~ Represents the phase of each element, ~ Represents the amplitude of each element respectively.

6. The method for correcting the additional damping control signal of a converter according to claim 5, characterized in that: The corrected additional damping control signal is: ； in, represents the corrected additional damping control signal, represents the phase of the subsynchronous component of the additional damping control signal extracted by the subsynchronous current phase-locked loop, represents the phase of the super-synchronous component of the additional damping control signal extracted by the super-synchronous current phase-locked loop, It represents the phase of the power frequency voltage phasor of the converter grid connection point extracted by the power frequency voltage phase-locked loop. represents the amplitude of the subsynchronous component of the additional damping control signal extracted by the subsynchronous current phase-locked loop and obtained by d / q transformation, It represents the amplitude of the supersynchronous component of the additional damping control signal extracted by the supersynchronous current phase-locked loop and obtained by d / q transformation.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions; when the computer program instructions are executed by a processor, the method for correcting an additional damping control signal of a converter according to any one of claims 1 to 6 is implemented.

8. A converter additional damping control signal correction system, characterized in that: include: An element determination module is used to determine each element of the transfer function matrix corresponding to the actual synchronization frequency using a pre-fitted calculation formula corresponding to each element according to the actual synchronization frequency, wherein the synchronization frequency includes: a subsynchronous frequency and a supersynchronous frequency; A parameter determination module is used to calculate the phase and amplitude of each element at the actual synchronization frequency based on each element using the relationship between the transfer function matrix corresponding to the actual synchronization frequency and the phase and amplitude; A signal correction module, configured to correct the input additional damping control signal using the phase and amplitude of each element at the actual synchronous frequency to control the output current of the converter; a signal injection and output module, configured to, before the step of determining each element of the transfer function matrix corresponding to the actual synchronous frequency using the pre-fitted calculation formula corresponding to each element, respectively inject two sets of current test signals having the same preset synchronous frequency into the converter, so that the converter outputs two sets of current output signals and two sets of converter grid-connected point power frequency voltage signals according to the two sets of current test signals, respectively, wherein the current test signals are generated by simulating the process from generation to suppression of current oscillations, and the amplitudes of subsynchronous components and supersynchronous components of the two sets of current test signals are different and linearly independent; A matrix solving module is used to solve the transfer function matrix equation based on two sets of current test signals, two sets of current output signals and two sets of power frequency voltage signals at the grid connection point of the converter corresponding to each preset synchronous frequency, so as to obtain the transfer function matrix corresponding to each preset synchronous frequency; A general formula fitting module is used to fit the elements at the same position in the transfer function matrix corresponding to all preset synchronization frequencies to obtain the calculation general formula corresponding to the elements at the same position; The transfer function matrix equation is: ； in, and Respectively k The reference values ​​of the two sets of current output signals at the sub-synchronous frequency, and Respectively k Reference values ​​of two sets of current test signals at sub-synchronous frequencies, and Respectively k The reference values ​​of the two sets of current output signals at super synchronous frequency, and Respectively k The reference values ​​of two sets of current test signals at super synchronous frequency, Respectively represent k The transfer function matrix corresponding to the synchronization frequency is: , Indicates the k Subsynchronous frequency, j Represents an imaginary number.

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