Resonance suppression device for DC transmission system

Abstract

The present application discloses a resonance suppression device for a direct current transmission system, the device comprising a signal acquisition module, a resonance judgment module, a subtractor, a filter branch and a delay branch; the output end of the signal acquisition module is connected to the input end of the resonance judgment module; the signal acquisition module collects the direct current side current and outputs the direct current side current to the resonance judgment module; the resonance judgment module determines the target resonance frequency; the filter branch comprises a filter, the filter filters out the target resonance current corresponding to the target resonance frequency in the direct current side current; the delay branch delays the direct current side current to obtain a delayed current, the delayed current includes currents corresponding to each resonance frequency; the output end of the filter branch is connected to the output end of the delay branch via a subtractor, the subtractor is used to remove the target resonance current from the delay current. It can be seen that the present application can suppress the target resonance current in the direct current transmission system.

Description

Technical Field

[0001] The present application relates to the field of direct current power transmission, and more specifically, to a resonance suppression device for a direct current power transmission system. Background Art

[0002] The DC side of a conventional DC transmission system is usually considered a harmonic voltage source, mainly because the exchange power is equal to the sum of the DC transmission power and the AC transmission power. The DC side voltage is related to the DC transmission power and changes with the change of the DC transmission power. The AC side voltage is related to the AC transmission power and changes with the change of the AC transmission power. In general, the AC power changes less, so the AC side voltage changes less. Based on this, when the exchange power changes significantly, the DC transmission power changes significantly with the exchange power, and the DC side voltage also changes significantly with the DC transmission power. Therefore, in the actual system operation, due to the significant change in the DC side voltage, there is a resonant oscillation on the DC side of the DC transmission system. The resonant oscillation will directly affect the safe and stable operation of the DC transmission system. Based on this, how to suppress the resonant oscillation of the DC transmission system has become a focus of attention. Summary of the invention

[0003] In view of this, the present application provides a resonance suppression device for a DC power transmission system, which is used to suppress the resonant oscillation of the DC power transmission system.

[0004] In order to achieve the above objectives, the proposed solution is as follows:

[0005] A resonance suppression device for a direct current power transmission system, comprising a signal acquisition module, a resonance judgment module, a subtractor, a filter branch and a delay branch;

[0006] The output end of the signal acquisition module is connected to the input end of the resonance judgment module;

[0007] The signal acquisition module is used to collect the DC side current in the DC power transmission system and output the DC side current to the resonance judgment module;

[0008] The resonance judgment module is used to determine the resonance frequencies corresponding to the DC operation mode of the DC power transmission system, and determine the target resonance frequency that needs to be filtered out among the resonance frequencies according to the DC side current;

[0009] The filtering branch comprises a filter, and the filter is used to filter out a target resonant current corresponding to the target resonant frequency in the DC side current;

[0010] The delay branch is used to delay the DC side current to obtain a delayed current, wherein the delayed current includes currents corresponding to each resonant frequency;

[0011] The output end of the filtering branch is connected to the output end of the delay branch through the subtractor;

[0012] The subtractor is used to remove the target resonant current from the delayed current, so as to suppress the target resonant current in the direct current power transmission system.

[0013] Optionally, the resonance judgment module includes a current decomposition unit and a target resonance frequency determination unit;

[0014] The decomposition current unit is used to determine the resonant frequencies corresponding to the DC operation mode of the DC power transmission system, and decompose the DC side current currently collected by the signal acquisition module through a dual spectrum interpolation FFT algorithm at every preset time period to obtain the resonant current corresponding to each resonant frequency;

[0015] The target resonant frequency determination unit is used to determine the target resonant frequency that needs to be filtered out among the resonant frequencies according to the resonant current corresponding to each resonant frequency.

[0016] Optionally, the target resonant frequency determination unit includes a current determination subunit and a current increase subunit;

[0017] The current judging subunit is used to judge whether the resonant current corresponding to each resonant frequency is gradually increasing according to the resonant current corresponding to the resonant frequency;

[0018] The current increasing subunit is used to use the resonant frequency as the target resonant frequency if the resonant current corresponding to the resonant frequency increases gradually.

[0019] Optionally, the current judgment subunit includes a size comparison component, a change number determination component and a current increase determination component;

[0020] The magnitude comparison component is used to determine whether the resonant current corresponding to each resonant frequency is greater than the current corresponding to the resonant frequency in the memory;

[0021] The change number determination component is used to update the change number corresponding to the resonant frequency in the memory to 0 if the resonant current corresponding to the resonant frequency is not greater than the current corresponding to the resonant frequency in the memory; if the resonant current corresponding to the resonant frequency is greater than the current corresponding to the resonant frequency in the memory, update the current corresponding to the resonant frequency in the memory to the resonant current, and add 1 to the change number corresponding to the resonant frequency in the memory, to determine whether the change number corresponding to the resonant frequency is not less than a preset change threshold;

[0022] The current increase determination component is used to determine that the current corresponding to the resonant frequency gradually increases if the number of changes is not less than a preset change threshold.

[0023] Optionally, the current judgment subunit includes a current comparison component, a time processing component and a current change judgment component;

[0024] The current comparison component is used to determine whether the resonant current corresponding to each resonant frequency is greater than the current corresponding to the resonant frequency in the memory;

[0025] The time processing component is used to clear the time corresponding to the resonant frequency in the memory if the resonant current corresponding to the resonant frequency is not greater than the current corresponding to the resonant frequency in the memory; if the resonant current corresponding to the resonant frequency is greater than the current corresponding to the resonant frequency in the memory, store the current time and the resonant frequency in the memory, and update the current corresponding to the resonant frequency in the memory to the resonant current;

[0026] The current change judgment component is used to calculate the resonance period corresponding to the resonance frequency if the resonance current corresponding to the resonance frequency is greater than the current corresponding to the resonance frequency in the memory, and to judge whether the difference between the earliest time and the latest time corresponding to the resonance frequency in the memory is greater than N resonance periods. If the difference between the earliest time and the latest time corresponding to the resonance frequency is greater than N resonance periods, it is determined that the current corresponding to the resonance frequency is gradually increased.

[0027] Optionally, the filter branch also includes a path controller, which is used to control the filter to output the resonant current to the subtractor when the resonance judgment module determines that there is a target resonant frequency, and is also used to control the filter not to output the resonant current to the subtractor when the resonance judgment module does not output the target resonant frequency.

[0028] It can be seen from the above technical solutions that the resonance suppression device of the DC transmission system provided by the present application includes a signal acquisition module, a resonance judgment module, a subtractor, a filter branch and a delay branch; the output end of the signal acquisition module is connected to the input end of the resonance judgment module; the signal acquisition module is used to collect the DC side current in the DC transmission system and output the DC side current to the resonance judgment module; the resonance judgment module is used to determine the resonant frequencies corresponding to the target DC operation mode according to the target DC operation mode of the DC transmission system and a preset table storing the correspondence between each DC operation mode and each resonant frequency, and determine and output the target resonant frequency that needs to be filtered out among the resonant frequencies. In this way, the resonance judgment module in the present application uses the DC side current collected by the signal acquisition module to determine the target resonant frequency of a specific frequency band that needs to be accurately filtered out; the filter branch includes a filter, and the filter The filter is used to filter out the target resonant current corresponding to the target resonant frequency in the DC side current. In this way, the filter in the present application can accurately filter out the target resonant current corresponding to a specific frequency band; the delay branch is used to delay the DC side current to obtain a delayed current, and the delayed current includes currents corresponding to various frequencies. In this way, the same DC side current enters the delay branch and the filter branch in the present application. After passing through the delay branch, the delayed current obtained after the DC side current is delayed is synchronized with the filtered target resonant current; the output end of the filter branch is connected to the output end of the delay branch through the subtractor; the subtractor is used to remove the target resonant current from the delay current to suppress the target resonant current in the DC transmission system. It can be seen that the present application can suppress the target resonant current corresponding to the target resonant frequency in a specific frequency band to suppress the resonant oscillation of the DC transmission system.

[0029] In addition, when determining the target resonant frequency of a specific frequency band that needs to be filtered out, the present application first determines the resonant frequencies corresponding to the target DC operation mode of the DC transmission system, and the target resonant frequency that needs to be filtered out among the resonant frequencies, first determines a frequency band range, and then determines the specific frequency band harmonics in the frequency band range. In this way, the calculation process can be simplified, the amount of calculation can be reduced, and the efficiency of suppressing the resonant oscillation of the DC transmission system can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0031] Figure 1This is a schematic diagram of a resonance suppression device for a direct current power transmission system disclosed in the present application. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0033] Next, combine Figure 1 The resonance suppression device of the direct current power transmission system of the present application is introduced in detail. The resonance suppression device includes a signal acquisition module, a resonance judgment module, a subtractor, a filter branch and a delay branch.

[0034] Among them, the signal acquisition module is used to collect the DC side current in the DC transmission system, and output the collected DC side current to the resonance judgment module.

[0035] In order to allow the signal acquisition module to output the collected DC side current to the resonance judgment module, the output end of the signal acquisition module can be connected to the input end of the resonance judgment module through a wire.

[0036] The resonance judgment module is used to determine the resonance frequencies corresponding to the DC operation mode of the DC power transmission system, and determine the target resonance frequency that needs to be filtered out among the resonance frequencies according to the DC side current collected by the signal acquisition module.

[0037] Specifically, there are three general types of DC operation modes for DC transmission systems: bipolar, single-pole grounding, and single-pole metal connection.

[0038] All resonant frequency points under different DC operation modes can be collected in advance according to line parameters and engineering parameters of the DC power transmission system, and a table can be established to store the DC operation mode and all resonant frequency points under the DC operation mode in the table.

[0039] Among them, the engineering parameters of the DC transmission system include the parameters of the main equipment of the DC transmission system, including the capacity, short-circuit impedance, voltage of the converter transformer and the inductance value of the smoothing reactor.

[0040] Generally speaking, conventional DC transmission systems only respond to frequencies below 300 Hz, so all resonant frequency points under DC operation are below 300 Hz.

[0041] When resonance occurs on the DC side of the DC transmission system, it is necessary to suppress a specific resonant frequency, thereby suppressing the resonance of the DC transmission system, and the specific resonant frequency that needs to be suppressed does not exceed the resonant frequency point corresponding to the DC operation mode corresponding to the DC transmission system recorded in the table.

[0042] Therefore, the resonance judgment module can call the table and search the DC operation mode of the DC transmission system in the table to determine the corresponding resonant frequencies under the DC operation mode, and determine the resonant frequency that needs to be filtered out or suppressed among the resonant frequencies based on the DC side current collected by the signal acquisition module, and use the resonant frequency that needs to be suppressed as the target resonant frequency.

[0043] Among them, the same type of DC operation mode generally corresponds to two or three resonant frequencies.

[0044] When the resonance judgment module determines that the target resonant frequency does not exist, it can be considered that the current DC transmission system does not have resonance and there is no need to suppress resonance; and when the resonance judgment module determines that the target resonant frequency exists, it is necessary to use the filter in the filter branch to filter out the target resonant current corresponding to the target resonant frequency in the DC side current.

[0045] The target resonant frequency generally includes more than one and less than three resonant frequencies.

[0046] The parameters of the filter in the filter branch can be adjusted according to the target resonant frequency determined and output by the resonance judgment module, so that the filter in the filter branch only filters out the target resonant current corresponding to the target resonant frequency in the DC side current.

[0047] The target resonant current of the filter requires time. In order to ensure the synchronization of the current, a delay branch needs to be added. The delay branch is used to delay the DC side current to obtain a delayed current. The delayed current includes the current corresponding to each resonant frequency.

[0048] The output end of the filter branch is connected to the output end of the delay branch through the subtractor;

[0049] The subtractor is used to remove the target resonant current from the delayed current, so as to suppress the target resonant current in the direct current power transmission system.

[0050] A filter branch, a delay branch and a subtractor can be added before the filter link in the DC power transmission system, so that the DC side current from which the target resonant current is filtered out is input into the filter link.

[0051] It can be seen from the above technical solutions that the resonance suppression device of the DC transmission system provided by the present application includes a signal acquisition module, a resonance judgment module, a subtractor, a filter branch and a delay branch; the output end of the signal acquisition module is connected to the input end of the resonance judgment module; the signal acquisition module is used to collect the DC side current in the DC transmission system and output the DC side current to the resonance judgment module; the resonance judgment module is used to determine the resonant frequencies corresponding to the target DC operation mode according to the target DC operation mode of the DC transmission system and a preset table storing the correspondence between each DC operation mode and each resonant frequency, and determine and output the target resonant frequency that needs to be filtered out among the resonant frequencies. In this way, the resonance judgment module in the present application uses the DC side current collected by the signal acquisition module to determine the target resonant frequency of a specific frequency band that needs to be accurately filtered out; the filter branch includes a filter, and the filter The filter is used to filter out the target resonant current corresponding to the target resonant frequency in the DC side current. In this way, the filter in the present application can accurately filter out the target resonant current corresponding to a specific frequency band; the delay branch is used to delay the DC side current to obtain a delayed current, and the delayed current includes currents corresponding to various frequencies. In this way, the same DC side current enters the delay branch and the filter branch in the present application. After passing through the delay branch, the delayed current obtained after the DC side current is delayed is synchronized with the filtered target resonant current; the output end of the filter branch is connected to the output end of the delay branch through the subtractor; the subtractor is used to remove the target resonant current from the delay current to suppress the target resonant current in the DC transmission system. It can be seen that the present application can suppress the target resonant current corresponding to the target resonant frequency in a specific frequency band to suppress the resonant oscillation of the DC transmission system.

[0052] In addition, when determining the target resonant frequency of a specific frequency band that needs to be filtered out, the present application first determines the resonant frequencies corresponding to the target DC operation mode of the DC transmission system, and the target resonant frequency that needs to be filtered out among the resonant frequencies, first determines a frequency band range, and then determines the specific frequency band harmonics that need to be filtered out in the frequency band range. In this way, the calculation process can be simplified, the amount of calculation can be reduced, and the efficiency of suppressing the resonant oscillation of the DC transmission system can be further improved.

[0053] In some embodiments of the present application, the resonance determination module includes a current decomposition unit and a target resonance frequency determination unit. Next, the functions of the current decomposition unit and the target resonance frequency determination unit will be described in detail.

[0054] The decomposition current unit is used to determine the resonant frequencies corresponding to the DC operation mode of the DC power transmission system. At preset time intervals, the DC side current currently collected by the signal acquisition module is decomposed by a dual-spectrum interpolation FFT algorithm to obtain the resonant current corresponding to each resonant frequency.

[0055] The DC side current includes current components corresponding to various frequencies and also includes resonant current components corresponding to various resonant frequencies.

[0056] The length of the time period can be determined according to the usage scenario. Generally speaking, the DC side current currently collected by the signal collection module can be decomposed once every 1ms to obtain the resonant current corresponding to each resonant frequency.

[0057] In a DC power transmission system, a current decomposition unit performs FFT decomposition on the DC side current to obtain current components corresponding to each resonant frequency, and the current components are resonant currents.

[0058] The target resonance frequency determination unit is used to determine the target resonance frequency that needs to be filtered out among the resonance frequencies according to the resonance current corresponding to each resonance frequency.

[0059] The target resonant frequency determination unit may determine whether the resonant current corresponding to each resonant frequency has changed compared with the historical resonant current corresponding to the resonant frequency, and if so, determine that the resonant frequency is the target resonant frequency.

[0060] When the resonant current corresponding to each resonant frequency changes compared with the historical resonant current corresponding to the resonant frequency, it may become larger or smaller.

[0061] It can be seen from the above technical solution that, compared with the previous embodiment, this embodiment provides an optional implementation method for a resonance judgment module to determine the target resonant frequency. Through the above embodiment, the DC side current can be decomposed into a resonant current, and the resonant current can be used to specifically determine the target resonant frequency, thereby further improving the efficiency of the resonance judgment module in determining the target resonant frequency.

[0062] In some embodiments of the present application, the target resonant frequency determination unit includes a current determination subunit and a current increase subunit. Next, the functions of the current determination subunit and the current increase subunit will be described in detail.

[0063] The current judging subunit is used to judge whether the resonant current corresponding to each resonant frequency is gradually increasing according to the resonant current corresponding to the resonant frequency.

[0064] Among them, the resonant current corresponding to each resonant frequency currently decomposed can be compared with the resonant current corresponding to the resonant frequency before the preset time period to determine whether the current resonant frequency has increased. After obtaining the new resonant current corresponding to the resonant frequency, the resonant current corresponding to each resonant frequency currently decomposed can be compared with the resonant current corresponding to the resonant frequency before the preset time period to determine whether the current resonant frequency has increased. When the comparison results corresponding to the resonant frequency have increased for multiple consecutive times, it can be determined that the resonant current corresponding to the resonant frequency has gradually increased.

[0065] Alternatively, the ratio between the change value of the resonant current corresponding to the resonant frequency and the preset time period may be calculated after each preset time period to obtain the current change rate of the resonant current. When the current change rate corresponding to the resonant current is greater than 0 for multiple consecutive times, the resonant frequency may be determined to be the target resonant frequency.

[0066] The current increasing subunit is used to use the resonant frequency as the target resonant frequency if the resonant current corresponding to the resonant frequency increases gradually.

[0067] When resonance occurs, the magnitude of the current will change. Therefore, it is possible to determine whether resonance occurs by determining whether the resonance current corresponding to the resonance frequency increases gradually.

[0068] It can be seen from the above technical solution that this embodiment provides an optional implementation method for a target resonant frequency determination unit to determine the target resonant frequency. Through the above technical solution, it is possible to determine whether the resonant frequency is the target resonant frequency by judging whether the resonant current corresponding to the resonant frequency gradually increases.

[0069] In some embodiments of the present application, the current determination subunit includes a size comparison component, a change number determination component and a current increase determination component. Next, the functions of the size comparison component, the change number determination component and the current increase determination component will be described in detail.

[0070] The size comparison component is used to determine whether the resonant current corresponding to each resonant frequency is greater than the current corresponding to the resonant frequency in the memory.

[0071] The memory stores a current corresponding to each resonance frequency, and the magnitude of the current is the same as the magnitude of the resonance current corresponding to the resonance frequency obtained by decomposition before a preset time period.

[0072] Therefore, by judging whether the resonant current corresponding to each resonant frequency is greater than the current corresponding to the resonant frequency in the memory, it can be determined whether the resonant current corresponding to the resonant frequency is increasing.

[0073] The change number determination component is used to update the change number corresponding to the resonant frequency in the memory to 0 if the resonant current corresponding to the resonant frequency is not greater than the current corresponding to the resonant frequency in the memory; if the resonant current corresponding to the resonant frequency is greater than the current corresponding to the resonant frequency in the memory, update the current corresponding to the resonant frequency in the memory to the resonant current, and add 1 to the change number corresponding to the resonant frequency in the memory to determine whether the change number corresponding to the resonant frequency is not less than a preset change threshold.

[0074] When the resonant current corresponding to the resonant frequency is not greater than the current corresponding to the resonant frequency in the memory, it can be considered that the resonant current corresponding to the current resonant frequency has not increased, and the number of changes corresponding to the resonant frequency is updated to 0.

[0075] The size of the preset change threshold can be set according to the specific usage scenario. Generally speaking, the preset change threshold is not less than 10.

[0076] The current increase determination component is used to determine that the current corresponding to the resonant frequency gradually increases if the number of changes is not less than a preset change threshold.

[0077] When the number of changes corresponding to the resonant frequency is greater than or equal to the change threshold, it can be considered that the current corresponding to the resonant frequency is gradually increasing.

[0078] It can be seen from the above technical solution that after combining the size comparison component, the change number determination component and the current increase determination component in this embodiment, it is possible to determine which resonant frequencies correspond to the resonant currents, which are gradually increasing, and further better determine the target resonant frequency.

[0079] In some embodiments of the present application, the current determination subunit includes a current comparison component, a time processing component and a current change determination component. Next, the functions of the current comparison component, the time processing component and the current change determination component will be described in detail.

[0080] The current comparison component is used to determine whether the resonant current corresponding to each resonant frequency is greater than the current corresponding to the resonant frequency in the memory.

[0081] The function of the current comparison component is consistent with that of the magnitude comparison component in the aforementioned embodiment, and reference may be made to the aforementioned introduction, which will not be repeated here.

[0082] A time processing component is used to clear the time corresponding to the resonant frequency in the memory if the resonant current corresponding to the resonant frequency is not greater than the current corresponding to the resonant frequency in the memory; if the resonant current corresponding to the resonant frequency is greater than the current corresponding to the resonant frequency in the memory, store the current time and the resonant frequency in the memory, and update the current corresponding to the resonant frequency in the memory to the resonant current.

[0083] When the resonant current corresponding to the resonant frequency is less than or equal to the current corresponding to the resonant frequency in the memory, it can be considered that the resonant current has not increased, and the time corresponding to the resonant frequency in the memory is cleared; when the resonant current corresponding to the resonant frequency is greater than the current corresponding to the resonant frequency in the memory, the current time and the resonant frequency are stored in the memory, and the current corresponding to the resonant frequency in the memory is updated to the resonant current.

[0084] The current change judgment component is used to calculate the resonance period corresponding to the resonance frequency if the resonance current corresponding to the resonance frequency is greater than the current corresponding to the resonance frequency in the memory, and to judge whether the difference between the earliest time and the latest time corresponding to the resonance frequency in the memory is greater than N resonance periods. If the difference between the earliest time and the latest time corresponding to the resonance frequency is greater than N resonance periods, it is determined that the current corresponding to the resonance frequency is gradually increased.

[0085] The size of N may be limited according to specific scenarios. Generally speaking, N may be greater than 5.

[0086] It can be seen from the above technical solutions that this embodiment, in combination with the current comparison component, the time processing component and the current change judgment component, can provide another method for determining which resonant frequencies correspond to the resonant current, and in a gradually increasing manner, can further better determine the target resonant frequency.

[0087] In some embodiments of the present application, the filter branch also includes a path controller, which is used to control the filter to output the resonant current to the subtractor when the resonance judgment module determines that there is a target resonant frequency, and is also used to control the filter not to output the resonant current to the subtractor when the resonance judgment module does not output the target resonant frequency.

[0088] When the resonance judgment module determines that there is no target resonance frequency, the resonance current output by the filter can be controlled not to be output to the subtractor.

[0089] It can be seen from the above technical solution that compared with the previous embodiment, this embodiment provides a method for controlling the filter branch. Through the above method, specific frequencies in the DC side current can be suppressed only when specific harmonics need to be filtered out, thereby further improving the practicality of the resonance suppression device of the DC transmission system.

[0090] Optionally, the detailed functions and extended functions of the program may refer to the above description.

[0091] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0092] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0093] The above description of the disclosed embodiments enables professionals and technicians in the field to implement or use the present application. Various modifications to these embodiments will be apparent to professionals and technicians in the field, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. The various embodiments of the present application can be combined with each other. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A resonance suppression device for a direct current transmission system, characterized in that: It includes a signal acquisition module, a resonance judgment module, a subtractor, a filter branch and a delay branch; The output end of the signal acquisition module is connected to the input end of the resonance judgment module; The signal acquisition module is used to collect the DC side current in the DC power transmission system and output the DC side current to the resonance judgment module; The resonance judgment module is used to determine the resonance frequencies corresponding to the DC operation mode of the DC power transmission system, and determine the target resonance frequency that needs to be filtered out among the resonance frequencies according to the DC side current; The filtering branch comprises a filter, and the filter is used to filter out a target resonant current corresponding to the target resonant frequency in the DC side current; The delay branch is used to delay the DC side current to obtain a delayed current, wherein the delayed current includes currents corresponding to each resonant frequency; The output end of the filtering branch is connected to the output end of the delay branch through the subtractor; The subtractor is used to remove the target resonant current from the delayed current, so as to suppress the target resonant current in the direct current power transmission system.

2. The resonance suppression device of a DC power transmission system according to claim 1, characterized in that: The resonance judgment module includes a current decomposition unit and a target resonance frequency determination unit; The decomposition current unit is used to determine the resonant frequencies corresponding to the DC operation mode of the DC power transmission system, and decompose the DC side current currently collected by the signal acquisition module through a dual spectrum interpolation FFT algorithm at every preset time period to obtain the resonant current corresponding to each resonant frequency; The target resonant frequency determination unit is used to determine the target resonant frequency that needs to be filtered out among the resonant frequencies according to the resonant current corresponding to each resonant frequency.

3. The resonance suppression device of a DC power transmission system according to claim 2, characterized in that: The target resonant frequency determination unit includes a current determination subunit and a current increase subunit; The current judging subunit is used to judge whether the resonant current corresponding to each resonant frequency is gradually increasing according to the resonant current corresponding to the resonant frequency; The current increasing subunit is used to use the resonant frequency as the target resonant frequency if the resonant current corresponding to the resonant frequency increases gradually.

4. The resonance suppression device of a DC power transmission system according to claim 3, characterized in that: The current judgment subunit includes a size comparison component, a change number determination component and a current increase determination component; The magnitude comparison component is used to determine whether the resonant current corresponding to each resonant frequency is greater than the current corresponding to the resonant frequency in the memory; The change number determination component is used to update the change number corresponding to the resonant frequency in the memory to 0 if the resonant current corresponding to the resonant frequency is not greater than the current corresponding to the resonant frequency in the memory; if the resonant current corresponding to the resonant frequency is greater than the current corresponding to the resonant frequency in the memory, update the current corresponding to the resonant frequency in the memory to the resonant current, and add 1 to the change number corresponding to the resonant frequency in the memory, to determine whether the change number corresponding to the resonant frequency is not less than a preset change threshold; The current increase determination component is used to determine that the current corresponding to the resonant frequency gradually increases if the number of changes is not less than a preset change threshold.

5. The resonance suppression device of a DC power transmission system according to claim 3, characterized in that: The current judgment subunit includes a current comparison component, a time processing component and a current change judgment component; The current comparison component is used to determine whether the resonant current corresponding to each resonant frequency is greater than the current corresponding to the resonant frequency in the memory; The time processing component is used to clear the time corresponding to the resonant frequency in the memory if the resonant current corresponding to the resonant frequency is not greater than the current corresponding to the resonant frequency in the memory; if the resonant current corresponding to the resonant frequency is greater than the current corresponding to the resonant frequency in the memory, store the current time and the resonant frequency in the memory, and update the current corresponding to the resonant frequency in the memory to the resonant current; The current change judgment component is used to calculate the resonance period corresponding to the resonance frequency if the resonance current corresponding to the resonance frequency is greater than the current corresponding to the resonance frequency in the memory, and to judge whether the difference between the earliest time and the latest time corresponding to the resonance frequency in the memory is greater than N resonance periods. If the difference between the earliest time and the latest time corresponding to the resonance frequency is greater than N resonance periods, it is determined that the current corresponding to the resonance frequency is gradually increased.

6. The resonance suppression device of a DC power transmission system according to claim 1, characterized in that: The filter branch also includes a path controller, which is used to control the filter to output the resonant current to the subtractor when the resonance judgment module determines that there is a target resonant frequency, and is also used to control the filter not to output the resonant current to the subtractor when the resonance judgment module does not output the target resonant frequency.

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