Filter parameter design method and system for inhibiting high-frequency harmonic transmission of direct current system

Abstract

The invention discloses a filter parameter design method and system for suppressing high-frequency harmonic transmission of a direct current system, and the method comprises the steps: detecting a branch current effective value of a filter at a valve side or a network side of a converter transformer under the excitation of current sources with different frequencies and amplitudes applied to the valve side or the network side of the converter transformer; calculating the sum of the branch current effective values of the filter under the excitation of the current sources with different frequencies; determining an equivalent high-frequency voltage source applied to the two ends of the filter according to the sum of the effective values of the branch current so as to obtain a temperature rise value of the filter caused by the high-frequency voltage source equivalent to different high-frequency harmonic current; and adjusting parameters of the filter according to a comparison result of the temperature rise value and a preset standard value. According to the scheme, parameter optimization design of the filter can be achieved, the suppression effect of high-frequency harmonic transmission is improved, the filter is prevented from being damaged, and therefore stable operation of the converter transformer is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current power transmission, and in particular to a filter parameter design method and system for suppressing high-frequency harmonic transmission of a direct current system. Background Art

[0002] There is a certain amount of background harmonics on the valve side or grid side of the converter transformer, and high-frequency harmonics of different frequencies may cause resonance between the coils inside the converter transformer. The converter transformer is the core equipment in the DC transmission system, and the reliable operation of the converter transformer is an important guarantee for the stable operation of the DC transmission system.

[0003] The filter is an important device in the DC transmission system, which plays an important role in preventing the high-frequency harmonics generated by the DC system from affecting the AC system. However, the existing technology lacks a test solution for the filter parameters under harsh working conditions, which easily leads to unreasonable filter parameter design. For example, when the temperature rise data is abnormal, the high-frequency harmonic transmission suppression effect may not be effectively performed, and even the filter may be damaged, thereby affecting the stable operation of the converter transformer. Summary of the invention

[0004] In view of the above-mentioned defects, the present invention provides a filter parameter design method and system for suppressing high-frequency harmonic transmission in a DC system, which can realize the parameter optimization design of the filter, improve the suppression effect of high-frequency harmonic transmission, avoid filter damage, and thus ensure the stable operation of the converter transformer.

[0005] An embodiment of the present invention provides a filter parameter design method for suppressing high-frequency harmonic transmission of a DC system, the method comprising: Detecting the effective value of the branch current of the filter on the valve side or the grid side of the converter transformer under the excitation of the current source of different frequencies applied on the valve side or the grid side of the converter transformer; Calculate the sum of the effective values ​​of the branch currents of the filter under the excitation of current sources of different frequencies; Determine the equivalent high-frequency voltage source applied to both ends of the filter according to the sum of the effective values ​​of the branch currents, so as to obtain the temperature rise value of the filter caused by the high-frequency voltage source equivalent to different high-frequency harmonic currents; According to the comparison result of the temperature rise value and the preset standard value, the parameters of the filter are adjusted.

[0006] Preferably, the method further comprises: Detecting the voltage across the filter under the excitation of current sources with different frequencies and amplitudes applied on the valve side or the grid side of the converter transformer; Adding the voltages borne by the filter under the excitation of current sources with different frequencies and amplitudes to obtain a voltage sum; Adding the voltage sum to the maximum continuous operating voltage of the device connected in parallel with the filter to obtain the maximum continuous operating voltage of the filter; The parameters of the filter are adjusted according to a comparison result between the maximum continuous operation voltage and a preset standard continuous operation voltage.

[0007] Preferably, the equivalent high-frequency voltage source applied to both ends of the filter is determined according to the sum of the effective values ​​of the branch currents, so as to obtain the temperature rise values ​​of the filter caused by different high-frequency harmonic currents equivalent to the high-frequency voltage source, including: Calculating an equivalent high-frequency voltage source applied to both ends of the filter according to the capacitance of the filter; The sum of the effective values ​​of the filter branch currents under the excitation of current sources of different frequencies is taken as the current flowing through the filter, thereby recording the temperature rise data of the filter within a preset time period.

[0008] Preferably, the amplitude range of the high-frequency current source applied on the valve side or the grid side of the converter transformer is the amplitude range obtained by performing Fourier analysis on the current on the valve side or the grid side when the converter transformer is actually operating.

[0009] Preferably, the process of determining the frequency range of applying the high-frequency current source on the valve side or the grid side of the converter transformer comprises: Applying harmonics of different frequencies in a preset high-frequency harmonic frequency band to the outside of the converter transformer; Calculating the response voltage between coils inside the converter transformer under different frequency harmonic excitations respectively; Calculate the ratio of the response voltage under harmonic excitation of different frequencies to the mean value of the response voltage at other frequencies; The frequency range is determined according to the frequencies whose calculated ratios are greater than a preset threshold.

[0010] The embodiment of the present invention further provides a filter parameter design system for suppressing high-frequency harmonic transmission of a DC system, the system comprising: An excitation module, used for calculating the effective value of the branch current of the filter on the valve side or the grid side of the converter transformer under the excitation of the current source of different frequencies applied on the valve side or the grid side of the converter transformer; A calculation module, used for calculating the sum of effective values ​​of branch currents of the filter under the excitation of current sources of different frequencies; An equivalent module is used to determine an equivalent high-frequency voltage source applied to both ends of the filter according to the sum of the effective values ​​of the branch currents, so as to obtain the temperature rise value of the filter caused by different high-frequency harmonic currents equivalent to the high-frequency voltage source; The design module is used to adjust the parameters of the filter according to the comparison result between the temperature rise value and the preset standard value.

[0011] Furthermore, the system also includes a voltage detection module, which is used to: Applying a high-frequency current source on the valve side or the grid side of the converter transformer to determine the voltage across the filter under the excitation of the current source with different frequencies and amplitudes; Adding the voltages borne by the filter under the excitation of current sources with different frequencies and amplitudes to obtain a voltage sum; Adding the voltage sum to the maximum continuous operating voltage of the device connected in parallel with the filter to obtain the maximum continuous operating voltage of the filter; The parameters of the filter are adjusted according to a comparison result between the maximum continuous operation voltage and a preset standard continuous operation voltage.

[0012] Preferably, the equivalent module is specifically used for: Calculating an equivalent high-frequency voltage source applied to both ends of the filter according to the capacitance of the filter; The sum of the effective values ​​of the filter branch currents under the excitation of current sources of different frequencies is taken as the current flowing through the filter, thereby recording the temperature rise data of the filter within a preset time period.

[0013] Preferably, the amplitude range of the high-frequency current source applied on the valve side or the grid side of the converter transformer is the amplitude range obtained by performing Fourier analysis on the current on the valve side or the grid side when the converter transformer is actually operating.

[0014] Preferably, the process of determining the frequency range of applying the high-frequency current source on the valve side or the grid side of the converter transformer comprises: Applying harmonics of different frequencies in a preset high-frequency harmonic frequency band to the outside of the converter transformer; Calculating the response voltage between coils inside the converter transformer under different frequency harmonic excitations respectively; Calculate the ratio of the response voltage under harmonic excitation of different frequencies to the mean value of the response voltage at other frequencies; According to the frequency whose calculated ratio is greater than the preset threshold, the frequency range is determined The filter parameter design method and system for suppressing high-frequency harmonic transmission of a DC system provided by the present invention detects the effective value of the branch current of the filter on the valve side or the grid side of the converter transformer under the excitation of current sources of different frequencies and amplitudes applied on the valve side or the grid side of the converter transformer; calculates the sum of the effective values ​​of the branch currents of the filter under the excitation of current sources of different frequencies; determines the equivalent high-frequency voltage source applied to both ends of the filter according to the sum of the effective values ​​of the branch currents, so as to obtain the temperature rise values ​​of the filter caused by the different high-frequency harmonic currents equivalent to the high-frequency voltage source; and adjusts the parameters of the filter according to the comparison result of the temperature rise value with the preset standard value. This scheme can realize the parameter optimization design of the filter, improve the suppression effect of high-frequency harmonic transmission, avoid filter damage, and thus ensure the stable operation of the converter transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a flow chart of a filter parameter design method for suppressing high-frequency harmonic transmission of a DC system provided by an embodiment of the present invention; Figure 2 1 is a schematic diagram of the system structure of a converter transformer valve-side filter provided in an embodiment of the present invention; Figure 3 1 is a schematic diagram of the system structure of a grid-side filter of a converter transformer provided by an embodiment of the present invention; Figure 4 It is a structural schematic diagram of a filter parameter design system for suppressing high-frequency harmonic transmission of a DC system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] See also Figure 1 , is a flow chart of a filter parameter design method for suppressing high-frequency harmonic transmission of a DC system provided by an embodiment of the present invention, the method comprising steps S1 to S4: Step S1, detecting the effective value of the branch current of the filter on the valve side or the grid side of the converter transformer under the excitation of the current source of different frequencies applied on the valve side or the grid side of the converter transformer; Step S2, calculating the sum of the effective values ​​of the branch currents of the filter under the excitation of current sources of different frequencies; Step S3, determining an equivalent high-frequency voltage source applied to both ends of the filter according to the sum of the effective values ​​of the branch currents, so as to obtain a temperature rise value of the filter caused by different high-frequency harmonic currents equivalent to the high-frequency voltage source; Step S4, adjusting the parameters of the filter according to the comparison result between the temperature rise value and the preset standard value.

[0018] In the specific implementation of this embodiment, when designing the filter capacitor parameters, the calculation process of the filter branch current under the influence of high-frequency harmonics and the filter temperature rise experimental process under high-frequency harmonics are designed, specifically: By applying a high-frequency current source on the valve side of the converter transformer, the effective value of the branch current of the filter under the current source excitation of different frequencies is calculated; The effective values ​​of the filter branch currents under the excitation of current sources of different frequencies are added together, and based on the sum of the effective values ​​of the filter branch currents, an equivalent high-frequency voltage source is applied to both ends of the filter, and the temperature rise caused by the different high-frequency harmonic currents equivalent to the high-frequency voltage is obtained. That is, based on the sum of the effective values ​​of the branch currents, the equivalent high-frequency voltage source applied to both ends of the filter is determined, and the temperature rise value caused by the different high-frequency harmonic currents equivalent to the obtained high-frequency voltage source is caused to the filter.

[0019] The temperature rise value of a capacitor means that under the excitation of high-frequency harmonic current or high-frequency harmonic voltage, the temperature of the capacitor will first rise and then remain constant. The temperature difference in this process is called the temperature rise value.

[0020] According to the comparison result of the temperature rise value and the preset standard value, the parameters of the filter are adjusted.

[0021] In the past, the harmonic sources in the power system were mainly some low-frequency devices, such as traditional thyristor rectifiers, etc. The harmonics they generated were mainly low-order harmonics, and the harmonic content below 3kHz was relatively high, and the impact on the system was also mainly reflected in the low-frequency band. The detection and analysis technology at that time was limited, and there were certain difficulties in the detection and analysis of high-frequency harmonics, and it was difficult to accurately grasp the characteristics and impact of high-frequency harmonics. In addition, early power equipment had a relatively strong tolerance to low-frequency harmonics, and the impact of low-frequency harmonics on equipment was relatively small. Therefore, when designing filters, the main focus was on harmonics below 3kHz to meet the basic needs at the time.

[0022] However, with the development of power electronics technology, a large number of high-frequency power equipment have been put into use, such as high-frequency switching power supplies, high-frequency inverters, etc. These devices will generate abundant high-frequency harmonics ranging from tens of kHz to hundreds of kHz. If the filter does not consider the impact of these high-frequency harmonics, it will not be able to effectively filter out the harmonics, resulting in a decrease in power quality and affecting the normal operation of other equipment.

[0023] High-frequency harmonics can cause a series of hazards in the power system, such as causing additional heat loss in transformers, cables and other equipment, and accelerating insulation aging; they may also interfere with communications and data networks, affecting the normal operation of the power system's control, protection and measurement systems.

[0024] In filters, capacitors are one of the key components that determine their filtering performance. Capacitor parameters such as capacitance, withstand voltage, and loss directly affect the filter's filtering effect on harmonics of different frequencies. In high-frequency harmonic environments, these capacitor parameters change more significantly, requiring more precise design and selection.

[0025] The influence of high-frequency characteristics must be considered when designing filter parameters. Under high-frequency harmonics, the equivalent circuit model of the capacitor will change. Parameters such as equivalent series resistance (ESR) and equivalent series inductance (ESL) can no longer be ignored. These parameters will affect the heating and voltage distribution of the capacitor, and thus affect the performance and reliability of the filter. By optimizing the parameters of the capacitor, the filter can have better filtering effect and stability under high-frequency harmonics.

[0026] When designing the parameters of the filter, if the difference between the current temperature rise data and the standard value exceeds the preset normal value, it means that the filter parameters need to be adjusted, and the equivalent series resistance ESR, equivalent series inductance ESL and other parameters need to be adjusted to optimize the heat generation and voltage distribution of the capacitor and improve the performance and reliability of the filter. Compared with the prior art, this case proposes a temperature rise test method for the filter under the influence of high-frequency harmonics. The manufacturer will design products that meet the insulation requirements based on this parameter, and take the test products for testing in advance to ensure that the temperature rise test value will not exceed the proposed temperature rise value, so as to ensure the effect of the filter in suppressing the transmission of high-frequency harmonics in the DC system and avoid damage to the filter, thereby ensuring the stable operation of the converter transformer. Through the detection of harsh working condition parameters: detect the changes in capacitor parameters under harsh working conditions, such as high temperature, high humidity, high voltage and other environmental conditions. Through the design and detection of capacitor parameters, it can be ensured that the filter can work normally under various harsh working conditions, and the reliability and adaptability of the filter can be improved.

[0027] In another embodiment provided by the present invention, the method further includes a detection process of the maximum continuous operating voltage of the filter, specifically: By applying a high-frequency current source on the valve side or the grid side of the converter transformer, the voltage across the filter under the excitation of the current source with different frequencies and amplitudes is determined; Add the voltages that the filter is subjected to when excited by current sources of different frequencies and amplitudes; The added voltage is superimposed on the maximum continuous operating voltage of other devices connected in parallel with the filter to obtain the maximum continuous operating voltage of the filter; The parameters of the filter are adjusted according to a comparison result between the maximum continuous operation voltage and a preset standard continuous operation voltage.

[0028] It should be noted that other equipment and the filter will be connected in parallel to the valve side of the converter transformer. Therefore, the maximum continuous operating voltage of other equipment should be superimposed on the sum of the voltages across the filter under the excitation of high-frequency current sources of different frequencies.

[0029] When designing the parameters of the filter, if the difference between the current maximum continuous operating voltage and the standard continuous operating voltage exceeds the preset normal value, it means that the filter parameters need to be adjusted to adjust parameters such as the equivalent series resistance ESR and the equivalent series inductance ESL to optimize the voltage distribution of the capacitor.

[0030] This application considers the maximum continuous operating voltage calculation method and temperature rise test method of the filter under the influence of high-frequency harmonics from tens of kHz to hundreds of kHz. Previously, the filter design only focused on harmonics below 3kHz, so the essence of the solution is still the parameter design of the capacitor itself, realizing the parameter optimization design under harsh working conditions. By optimizing the parameters of the capacitor, the filter can have better filtering effect and stability under high-frequency harmonics.

[0031] In another embodiment provided by the present invention, when performing equivalent calculation of temperature rise data, the following steps are specifically included: According to the capacitance of the filter, determining an equivalent high-frequency voltage source applied to both ends of the filter; Apply a certain high-frequency voltage source, determine the equivalent voltage source excitation, ensure that the current flowing through the filter under the equivalent voltage source excitation is the sum of the effective values ​​of the filter branch currents under the excitation of current sources of different frequencies, and record the temperature rise data of the filter within a preset time period.

[0032] The present application adds the effective values ​​of the filter branch currents under the excitation of current sources of different frequencies, and according to the sum of the effective values ​​of the filter branch currents, calculates an equivalent high-frequency voltage source to be applied to both ends of the filter, and uses the high-frequency voltage equivalent to the high-frequency harmonic current to cause the temperature rise of the filter. This scheme has the advantages of simple calculation method and adaptability to multiple scenarios. It can be widely used in the field of DC transmission engineering technology according to actual engineering needs.

[0033] In another embodiment provided by the present invention, the amplitude range of the high-frequency current source applied to the valve side or the grid side of the converter transformer is the amplitude obtained by Fourier analysis of the current on the valve side and the grid side when the converter transformer is actually running. Specifically: The amplitude of the high-frequency current source applied on the valve side of the converter transformer is given according to the Fourier analysis result of the recorded wave data on the valve side of the converter transformer in the actual project.

[0034] In another embodiment provided by the present invention, there is a risk of resonance between the coils inside the converter transformer under the excitation of currents of different frequencies. The frequency of the high-frequency current source should be selected to be a frequency band that is easy to cause resonance between the coils inside the converter transformer. When the frequency range is specifically determined, the following steps are performed: Applying harmonics of different frequencies in a preset high-frequency harmonic frequency band to the outside of the converter transformer; Applying a high-frequency harmonic source on the grid side and valve side of the converter transformer, and calculating the response voltage between the coils inside the converter transformer under different frequency harmonic excitations; Under high-frequency harmonic excitation of some frequencies, the voltage between the internal coils is relatively high, so the ratio of the response voltage under harmonic excitation of different frequencies to the average value of the response voltage at other frequencies is calculated; The frequency range is determined based on the frequency at which the calculated ratio is greater than a preset threshold value. That is, when there are high-frequency harmonics of several kHz to several hundred kHz outside the converter transformer, under the excitation of high-frequency harmonics of certain frequencies, the voltage between the coils inside the converter transformer will be much greater than the response under the excitation of high-frequency harmonics of other frequencies, which is determined as the frequency range.

[0035] It should be noted that the filter parameter detection method for suppressing high-frequency harmonic transmission of a DC system provided in this solution is not only applicable to filters installed on the grid side of a converter transformer, but can also be applied to filters installed on the valve side of a converter transformer.

[0036] For specific implementation, see Figure 2 , is a schematic diagram of the system structure of the converter transformer valve side filter provided by an embodiment of the present invention. Converter transformer valve side A phase high frequency current source 1, converter transformer valve side B phase high frequency current source 2, converter transformer valve side C phase high frequency current source 3, converter transformer valve side A phase filter 4, converter transformer valve side B phase filter 5, converter transformer valve side C phase filter 6, A phase converter transformer 7, B phase converter transformer 8, C phase converter transformer 9. Among them, the grid side of the ABC three-phase converter transformer adopts the star connection method, and the valve side of the ABC three-phase converter transformer adopts the delta connection method. The high frequency current source and filter of the A phase are connected to the connection point of the A phase and the B phase, the high frequency current source and filter of the B phase are connected to the connection point of the B phase and the C phase, and the high frequency current source and filter of the C phase are connected to the connection point of the A phase and the C phase.

[0037] By applying a three-phase high-frequency current source on the valve side of the ABC three-phase converter transformer, the phase difference is 120 degrees. In this way, the voltages borne by the filter under the excitation of current sources of different frequencies are added. The added voltage is superimposed on the maximum continuous operating voltage of other devices connected in parallel with the filter to obtain the maximum continuous operating voltage of the filter. The parameters of the filter are designed according to the maximum continuous operating voltage, while reducing the impact of high-frequency components on the converter transformer, ensuring that the filter body will not be damaged due to overvoltage or overcurrent.

[0038] The effective values ​​of the filter branch currents under the excitation of current sources of different frequencies are added together. Based on the sum of the effective values ​​of the filter branch currents, an equivalent high-frequency voltage source is calculated and applied to both ends of the filter. The temperature rise caused by the high-frequency voltage equivalent to the high-frequency harmonic current on the filter is calculated.

[0039] According to the capacitance of the filter, a specific equivalent voltage source amplitude and frequency are selected to ensure that under the excitation of the equivalent voltage source, the current flowing through the filter is the sum of the effective values ​​of the filter branch currents under the excitation of the current sources of different frequencies on the valve side of the converter transformer. On the other hand, the amplitude of the equivalent voltage source should not exceed the calculated maximum continuous operating voltage of the filter.

[0040] As a parallel embodiment, see Figure 3 , is a schematic diagram of the system structure of the grid-side filter of the converter transformer provided by an embodiment of the present invention. Figure 3 As shown, the A-phase high-frequency current source 10, the B-phase high-frequency current source 11, the C-phase high-frequency current source 12, the A-phase filter 13, the B-phase filter 14, and the C-phase filter 15 are provided on the grid side of the converter transformer. The grid side of the ABC three-phase converter transformer adopts the star connection method, and the valve side of the ABC three-phase converter transformer adopts the delta connection method. The high-frequency current source and filter of the A-phase are connected to the connection point of the A-phase and the B-phase, the high-frequency current source and filter of the B-phase are connected to the connection point of the B-phase and the C-phase, and the high-frequency current source and filter of the C-phase are connected to the connection point of the A-phase and the C-phase.

[0041] Based on the differences in the structural diagrams, the specific steps in the design of filter parameters for suppressing the transmission of high-frequency harmonics in the DC system are similar, including the following steps: By applying a three-phase high-frequency current source with a phase difference of 120 degrees on the grid side of the ABC three-phase converter transformer, the voltages borne by the filter under the excitation of current sources of different frequencies are added. The added voltage is superimposed on the maximum continuous operating voltage of other devices connected in parallel with the filter to obtain the maximum continuous operating voltage of the filter.

[0042] By applying a three-phase high-frequency current source with a phase difference of 120 degrees on the grid side of the ABC three-phase converter transformer, the current flowing through the filter branch is calculated under the excitation of different frequency current sources.

[0043] The effective values ​​of the filter branch currents under the excitation of current sources of different frequencies are added together. Based on the sum of the effective values ​​of the filter branch currents, an equivalent high-frequency voltage source is calculated and applied to both ends of the filter. The temperature rise caused by the high-frequency voltage equivalent to the high-frequency harmonic current on the filter is calculated.

[0044] According to the capacitance of the filter, a specific equivalent voltage source amplitude and frequency are selected to ensure that under the excitation of the equivalent voltage source, the current flowing through the filter is the sum of the effective values ​​of the filter branch currents under the excitation of the current sources of different frequencies on the grid side of the converter transformer. On the other hand, the amplitude of the equivalent voltage source should not exceed the calculated maximum continuous operating voltage of the filter.

[0045] The embodiment of the present invention also provides a filter parameter design system for suppressing high-frequency harmonic transmission of a DC system, see Figure 4 , is a schematic diagram of the structure of a filter parameter design system for suppressing high-frequency harmonic transmission of a DC system provided by an embodiment of the present invention, the system comprising: An excitation module, used for calculating the effective value of the branch current of the filter on the valve side or the grid side of the converter transformer under the excitation of the current source of different frequencies applied on the valve side or the grid side of the converter transformer; A calculation module, used for calculating the sum of effective values ​​of branch currents of the filter under the excitation of current sources of different frequencies; An equivalent module is used to determine an equivalent high-frequency voltage source applied to both ends of the filter according to the sum of the effective values ​​of the branch currents, so as to obtain the temperature rise value of the filter caused by different high-frequency harmonic currents equivalent to the high-frequency voltage source; The design module is used to adjust the parameters of the filter according to the comparison result between the temperature rise value and the preset standard value.

[0046] It should be noted that the filter parameter design system for suppressing high-frequency harmonic transmission of a DC system provided in an embodiment of the present invention can execute the filter parameter design method for suppressing high-frequency harmonic transmission of a DC system described in any of the above embodiments. The specific functions of the filter parameter design system for suppressing high-frequency harmonic transmission of a DC system will not be described here.

[0047] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A filter parameter design method for suppressing high-frequency harmonic transmission in a DC system, characterized in that: The method comprises: Detecting the effective value of the branch current of the filter on the valve side or the grid side of the converter transformer under the excitation of the current source of different frequencies applied on the valve side or the grid side of the converter transformer; Calculate the sum of the effective values ​​of the branch currents of the filter under the excitation of current sources of different frequencies; Determine the equivalent high-frequency voltage source applied to both ends of the filter according to the sum of the effective values ​​of the branch currents, so as to obtain the temperature rise value of the filter caused by the high-frequency voltage source equivalent to different high-frequency harmonic currents; According to the comparison result of the temperature rise value and the preset standard value, the parameters of the filter are adjusted.

2. The filter parameter design method for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 1, characterized in that: The method further comprises: Detecting the voltage across the filter under the excitation of current sources with different frequencies and amplitudes applied on the valve side or the grid side of the converter transformer; Adding the voltages borne by the filter under the excitation of current sources with different frequencies and amplitudes to obtain a voltage sum; Adding the voltage sum to the maximum continuous operating voltage supported by the device connected in parallel with the filter to obtain the maximum continuous operating voltage of the filter; The parameters of the filter are adjusted according to a comparison result between the maximum continuous operation voltage and a preset standard continuous operation voltage.

3. The filter parameter design method for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 1, characterized in that: According to the sum of the effective values ​​of the branch currents, an equivalent high-frequency voltage source applied to both ends of the filter is determined, so as to obtain the temperature rise values ​​of the filter caused by the high-frequency voltage source equivalent to different high-frequency harmonic currents, including: Calculating an equivalent high-frequency voltage source applied to both ends of the filter according to the capacitance of the filter; The sum of the effective values ​​of the filter branch currents under the excitation of current sources of different frequencies is taken as the current flowing through the filter, thereby recording the temperature rise data of the filter within a preset time period.

4. The filter parameter design method for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 1, characterized in that: The amplitude range of the high-frequency current source applied on the valve side or the grid side of the converter transformer is the amplitude range obtained by performing Fourier analysis on the current on the valve side or the grid side when the converter transformer is in operation.

5. The filter parameter design method for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 1, characterized in that: The process of determining the frequency range of applying the high-frequency current source on the valve side or the grid side of the converter transformer includes: Applying harmonics of different frequencies in a preset high-frequency harmonic frequency band to the outside of the converter transformer; Calculating the response voltage between coils inside the converter transformer under different frequency harmonic excitations respectively; Calculate the ratio of the response voltage under harmonic excitation of different frequencies to the mean value of the response voltage at other frequencies; The frequency range is determined according to the frequencies whose calculated ratios are greater than a preset threshold.

6. A filter parameter design system for suppressing high-frequency harmonic transmission in a DC system, characterized in that: The system comprises: An excitation module, used to detect the effective value of the branch current of the filter on the valve side or the grid side of the converter transformer under the excitation of the current source of different frequencies applied on the valve side or the grid side of the converter transformer; A calculation module, used for calculating the sum of effective values ​​of branch currents of the filter under the excitation of current sources of different frequencies; An equivalent module is used to determine an equivalent high-frequency voltage source applied to both ends of the filter according to the sum of the effective values ​​of the branch currents, so as to obtain a temperature rise value of the filter caused by different high-frequency harmonic currents equivalent to the high-frequency voltage source; The design module is used to adjust the parameters of the filter according to the comparison result between the temperature rise value and the preset standard value.

7. The filter parameter design system for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 6, characterized in that: The system further comprises a voltage detection module, which is used to: Detecting the voltage across the filter under the excitation of current sources with different frequencies and amplitudes applied on the valve side or the grid side of the converter transformer; Adding the voltages borne by the filter under the excitation of current sources with different frequencies and amplitudes to obtain a voltage sum; Adding the voltage sum to the maximum continuous operating voltage of the device connected in parallel with the filter to obtain the maximum continuous operating voltage of the filter; The parameters of the filter are adjusted according to a comparison result between the maximum continuous operation voltage and a preset standard continuous operation voltage.

8. The filter parameter design system for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 6, characterized in that: The equivalent module is specifically used for: Calculating an equivalent high-frequency voltage source applied to both ends of the filter according to the capacitance of the filter; The sum of the effective values ​​of the filter branch currents under the excitation of current sources of different frequencies is taken as the current flowing through the filter, thereby recording the temperature rise data of the filter within a preset time period.

9. The filter parameter design system for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 6, characterized in that: The amplitude range of the high-frequency current source applied on the valve side or the grid side of the converter transformer is the amplitude range obtained by performing Fourier analysis on the current on the valve side or the grid side when the converter transformer is actually in operation.

10. The filter parameter design system for suppressing high-frequency harmonic transmission of a DC system as claimed in claim 6, characterized in that: The process of determining the frequency range of applying the high-frequency current source on the valve side or the grid side of the converter transformer includes: Applying harmonics of different frequencies in a preset high-frequency harmonic frequency band to the outside of the converter transformer; Calculating the response voltage between coils inside the converter transformer under different frequency harmonic excitations respectively; Calculate the ratio of the response voltage under harmonic excitation of different frequencies to the mean value of the response voltage at other frequencies; The frequency range is determined according to the frequencies whose calculated ratios are greater than a preset threshold.

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