A method, device, equipment and storage medium for determining resonance risk

Abstract

The present application discloses a resonance risk determination method, device, equipment and storage medium, which obtains the harmonic voltage on the AC side of the DC transmission system and the harmonic current on the DC side, and obtains the equipment protection setting and harmonic coefficient of the DC transmission system, and then obtains the harmonic impedance threshold of the DC transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient, compares the harmonic impedance threshold with the actual harmonic impedance value obtained, and determines the resonance risk based on the comparison result. This scheme obtains the equipment protection setting and the harmonic coefficient of the DC transmission system to be determined, and then uses the equipment protection setting and the harmonic coefficient to calculate the harmonic impedance threshold, so that the resonance risk is determined according to the characteristics of the DC transmission system itself, which can improve the accuracy of the resonance risk determination.

Description

Technical Field

[0001] The present application relates to the field of direct current transmission technology, and in particular to a resonance risk determination method, device, equipment and storage medium. Background Art

[0002] The DC transmission system is composed of the power electronic inverter side, and the operation of the inverter side will mainly rely on the control system. The introduction of the control system makes the entire system have the possibility of negative damping, especially when the primary impedance is relatively low, which increases the possibility of weak damping or negative damping in the system, resulting in the risk of resonance in the system under disturbance.

[0003] In the existing resonance risk determination method, the same standard is often used to determine the resonance risk for different DC transmission systems, without considering the characteristics of the DC transmission system itself, resulting in inaccurate determination results. Summary of the invention

[0004] In view of this, the present application provides a resonance risk determination method, apparatus, device and storage medium, which are used to solve the defect that the prior art uses the same standard to determine the resonance risk, does not consider the characteristics of the DC transmission system itself, and thus leads to inaccurate determination results.

[0005] To achieve the above objectives, the proposed solution is as follows:

[0006] In a first aspect, a resonance risk determination method is provided, comprising:

[0007] Obtaining harmonic voltage on the AC side and harmonic current on the DC side of the DC transmission system;

[0008] Obtaining equipment protection settings and harmonic coefficients of the DC power transmission system;

[0009] Obtaining a harmonic impedance threshold of the DC power transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient;

[0010] Obtaining an actual harmonic impedance value of the DC power transmission system;

[0011] The actual harmonic impedance value is compared with the harmonic impedance threshold value, and the resonance risk is determined based on the comparison result.

[0012] Preferably, obtaining the harmonic impedance threshold of the DC power transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient includes:

[0013] Obtaining a first threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side, and the harmonic coefficient;

[0014] Obtaining a second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting value;

[0015] comparing the first threshold to a second threshold;

[0016] The larger value between the first threshold and the second threshold is used as the harmonic impedance threshold.

[0017] Preferably, obtaining the first threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side, and the harmonic coefficient includes:

[0018] The harmonic voltage on the AC side is represented as U acn , the harmonic current on the DC side is expressed as I dcn , the harmonic coefficient is represented as D, the first threshold is represented as Z1, then according to U acn and I dcn The calculation formula for obtaining the first threshold is:

[0019]

[0020] Where n represents the harmonic order.

[0021] Preferably, obtaining the second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting value includes:

[0022] The device protection setting is represented by K, and the second threshold is represented by Z2. acn ,I dcn The calculation formula of the second threshold is obtained by summing K:

[0023]

[0024] Preferably, comparing the actual harmonic impedance value with the harmonic impedance threshold and determining the resonance risk based on the comparison result includes: judging whether the actual harmonic impedance value is less than the harmonic impedance threshold; if so, determining that the DC power transmission system has a resonance risk.

[0025] Preferably, the method further comprises: if it is determined that the actual harmonic impedance value is not less than the harmonic impedance threshold, determining that the DC power transmission system has no resonance risk.

[0026] In a second aspect, a resonance risk determination device includes:

[0027] A voltage and current acquisition module, used to acquire the harmonic voltage on the AC side and the harmonic current on the DC side of the DC transmission system;

[0028] An equipment protection setting value and harmonic coefficient acquisition module, used to obtain equipment protection setting values ​​and harmonic coefficients of the DC power transmission system;

[0029] A harmonic impedance threshold obtaining module, used to obtain the harmonic impedance threshold of the DC power transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient;

[0030] An actual harmonic impedance value acquisition module, used to acquire the actual harmonic impedance value of the DC power transmission system;

[0031] The resonance risk determination module is used to compare the actual harmonic impedance value with the harmonic impedance threshold value, and determine the resonance risk based on the comparison result.

[0032] Preferably, the harmonic impedance threshold obtaining module includes:

[0033] A first threshold value obtaining module, used to obtain a first threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side, and the harmonic coefficient;

[0034] A second threshold value obtaining module is used to obtain the second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting value;

[0035] A comparison module, configured to compare the first threshold with a second threshold;

[0036] The harmonic impedance threshold value finally obtains the module, which is used to take the larger value of the first threshold value and the second threshold value as the harmonic impedance threshold value.

[0037] In a third aspect, a resonance risk determination device includes a memory and a processor;

[0038] The memory is used to store programs;

[0039] The processor is used to execute the program to implement the various steps of the resonance risk determination method as described in the first aspect.

[0040] In a fourth aspect, a storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the resonance risk determination method as described in the first aspect are implemented.

[0041] It can be seen from the above technical scheme that the present application obtains the harmonic voltage on the AC side of the DC transmission system and the harmonic current on the DC side, and obtains the equipment protection setting and harmonic coefficient of the DC transmission system, and then obtains the harmonic impedance threshold of the DC transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient, compares the harmonic impedance threshold with the actual harmonic impedance value obtained, and determines the resonance risk based on the comparison result. This scheme obtains the equipment protection setting and the harmonic coefficient of the DC transmission system to be determined, and then uses the equipment protection setting and the harmonic coefficient to calculate the harmonic impedance threshold, so that the resonance risk is judged after comprehensively considering the characteristics of the DC transmission system itself, thereby improving the accuracy of the resonance risk judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of an optional structure of a direct current transmission system provided in an embodiment of the present application;

[0043] Figure 2 A schematic diagram of an optional structure of the DC side of the DC power transmission system provided in an embodiment of the present application;

[0044] Figure 3 An optional flow chart of a resonance risk determination method provided in an embodiment of the present application;

[0045] Figure 4 A schematic diagram of a resonance risk determination device provided in an embodiment of the present application;

[0046] Figure 5 A schematic diagram of the structure of a resonance risk determination device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0047] 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.

[0048] The DC transmission system is composed of the power electronic inverter side, and the operation of the inverter side will mainly rely on the control system. The introduction of the control system makes the entire system have the possibility of negative damping, especially when the primary impedance is relatively low, which increases the possibility of weak damping or negative damping in the system, resulting in the system not attenuating or even resonant amplification under disturbance. The overall structure of the DC transmission system can be shown as follows Figure 1 shown.

[0049] The DC side of a conventional DC transmission system is usually considered a harmonic voltage source, mainly because its DC side voltage is directly related to the AC side voltage. Usually, the AC system voltage changes little, so the DC side can be considered a harmonic voltage source. Because the DC side is usually considered a harmonic voltage source, the low impedance point of the parallel connection is usually paid attention to during the DC loop resonance scan to prevent large harmonic currents from appearing on the DC side.

[0050] According to the above analysis, the DC side equivalent circuit can be Figure 2 As shown, Figure 2 Only the influence of single-pole harmonic source is considered in the figure. In the actual system, the other pole including the opposite station will generate harmonic source, and there is interaction between them. This effect may be positive damping or negative damping. In order to simplify the analysis, only single-pole effect is considered here. The DC side of the DC transmission system is composed of harmonic voltage source and harmonic impedance in series, where the harmonic impedance is Figure 2 The Z shown in d The impedance should also include the harmonic impedance of the station, where L1 and L2 represent flat impedance, L3 and L4 represent equivalent impedance, ① and ③ represent pole lines, and ② represents ground pole line.

[0051] In the prior art, in order to ensure that the DC side resonance does not generate large harmonic currents, many aspects are considered. Therefore, the DC transmission system needs to be optimized and designed, which usually requires repeated design verification, as follows:

[0052] 1) Equipment protection settings on the DC side. For example, the equipment protection settings of smoothing reactors, DC filters, coupling capacitors, impulse capacitors, etc. will take the corresponding harmonic settings into consideration to determine the equipment protection settings. Among them, the harmonic tolerance of the DC transmission system will be considered during the design of the DC filter.

[0053] 2) DC bias of converter transformer: The DC bias of converter transformer mainly depends on the power frequency component on the DC side.

[0054] Among them, the influence of three factors is mainly considered. The first is the influence of the DC side power frequency resonance; the second is the inductive influence of the parallel AC line, which is related to the parallel length and distance of the AC line; the third is the influence of the grounding current, which is related to the grounding site selection design.

[0055] 3) Configuration of AC filter: When the DC side of the DC transmission system resonates at integer multiples of the frequency, it will cause large harmonic currents corresponding to the ±1 frequency on the AC side, thus affecting the configuration of the AC filter on the AC side, and may even require the configuration of a low-order filter on the AC side.

[0056] However, the above requirements will lead to a large increase in equipment costs. Therefore, it is crucial to determine the resonance risk of the DC transmission system. In the existing resonance risk determination methods, the same standard is often used to determine the resonance risk for different DC transmission systems, without considering the characteristics of the DC transmission system itself, resulting in inaccurate determination results.

[0057] Based on the above defects, the embodiment of the present application provides a resonance risk determination solution. Figure 3 The resonance risk determination method of the present application is described as follows: Figure 3 As shown, the method includes:

[0058] S1: Obtain the harmonic voltage on the AC side and the harmonic current on the DC side of the DC transmission system.

[0059] Among them, the harmonic transfer characteristics of the AC side are: the positive sequence nth harmonic voltage on the AC side will generate n-1th harmonic voltage on the DC side, and the negative sequence nth harmonic voltage on the AC side will generate n+1th harmonic voltage on the DC side.

[0060] The harmonic transfer characteristics of the DC side are as follows: the nth harmonic current on the DC side generates n+1th positive sequence harmonic current and n-1th negative sequence harmonic current when transmitted on the AC side.

[0061] S2: Obtain the equipment protection settings and harmonic coefficients of the DC transmission system.

[0062] In DC projects, 50Hz protection and 100Hz protection are commonly configured protections in DC projects, that is, the harmonic frequencies of the DC transmission system are 50Hz and 100Hz. The protection configurations are: IdN_50Hz>I_set+*IdN, IdN_100Hz>I_set+*IdN. Among them, 50Hz protection is mainly used to protect the abnormal triggering caused by the fault of the converter valve triggering system. 100Hz is used as a backup protection, mainly for asymmetric fault protection of the AC system.

[0063] Among them, the equipment protection setting list for 50Hz protection can be shown in Table 1 below:

[0064] Table 1

[0065] Serial number name Fixed value unit Correspondence 1 50Hz alarm setting 0.02 pu I_set 2 50Hz ratio coefficient setting value 0.05 k_set 3 50Hz motion customization 0.0333 pu 4 50Hz switching time setting 200 ms 5 50Hz power fallback time setting 3000 ms 6 50Hz action time setting 5000 ms 7 50Hz Throw-out 1

[0066] The equipment protection setting list for 100Hz protection can be shown in Table 2 below:

[0067] Table 2

[0068] Serial number name Fixed value unit Correspondence 1 100Hz alarm setting 0.03 pu I_set 2 100Hz ratio coefficient setting value 0.05 k_set 3 100Hz motion customization 0.0333 pu 4 100Hz switching time setting 800 ms 5 100Hz action time setting 3000 ms 6 100Hz Throw and Throw 1

[0069] The equipment protection settings of the above-mentioned 50Hz protection and 100Hz protection are generally derived from the input provided by the converter valve manufacturer, that is, the tolerance capacity of the equipment.

[0070] According to Table 1 and Table 2, the device protection setting value of 50Hz protection can be 0.02, and the device protection setting value of 100Hz protection can be 0.03.

[0071] S3: The harmonic impedance threshold of the DC transmission system is obtained based on the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient.

[0072] S4: Obtain the actual harmonic impedance value of the DC transmission system.

[0073] S5: Compare the actual harmonic impedance value with the harmonic impedance threshold, and determine the resonance risk based on the comparison result.

[0074] It can be seen from the technical solutions provided in the above embodiments that the present application obtains the harmonic voltage on the AC side of the DC transmission system and the harmonic current on the DC side, and obtains the equipment protection setting and harmonic coefficient of the DC transmission system, and then obtains the harmonic impedance threshold of the DC transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient, compares the harmonic impedance threshold with the actual harmonic impedance value obtained, and determines the resonance risk based on the comparison result. This solution obtains the equipment protection setting and the harmonic coefficient of the DC transmission system to be determined, and then uses the equipment protection setting and the harmonic coefficient to calculate the harmonic impedance threshold, so that the resonance risk is determined after comprehensively considering the characteristics of the DC transmission system itself, thereby improving the accuracy of the resonance risk determination.

[0075] Optionally, in step S3, a harmonic impedance threshold of the DC power transmission system is obtained according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient. The process may include:

[0076] S31: Obtain a first threshold value according to the harmonic voltage on the AC side, the harmonic current and the harmonic coefficient on the DC side.

[0077] The first threshold can be expressed as the harmonic impedance threshold on the DC side, and the harmonic voltage on the AC side is expressed as U acn , the harmonic current on the DC side is expressed as I dcn , the harmonic coefficient is represented as D, the first threshold is represented as Z1, then according to U acn and I dcn The calculation formula for the first threshold is:

[0078]

[0079] Where n represents the harmonic order.

[0080] S32: Obtain a second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting.

[0081] The device protection setting is represented by K, and the second threshold is represented by Z2. According to U acn ,I dcn The calculation formula of the second threshold is obtained by summing up K:

[0082]

[0083] S33: Compare the first threshold with the second threshold.

[0084] S34: The larger value between the first threshold and the second threshold is used as the harmonic impedance threshold.

[0085] Optionally, in the above step S5, the actual harmonic impedance value is compared with the harmonic impedance threshold value, and the resonance risk is determined based on the comparison result. The process may include:

[0086] Determine whether the actual harmonic impedance value is less than the harmonic impedance threshold;

[0087] If so, it is determined that the DC power transmission system has a resonance risk; if not, it is determined that the DC power transmission system has no resonance risk.

[0088] The actual harmonic impedance value is defined as Z dc , that is, the following comparison formula can be obtained:

[0089]

[0090] Specifically, when the above formula is satisfied, it can be determined that there is no resonance risk on the DC side of the DC transmission system; if it is not satisfied, it can be determined that there is a resonance risk on the DC side of the DC transmission system.

[0091] Specifically, for a 12-pulse converter, the calculation formula for the harmonic voltage on the DC side of the DC transmission system can be expressed as follows:

[0092]

[0093]

[0094] In the above expressions, the subscripts "ac" and "dc" represent the AC side and DC side of the converter, respectively; the superscripts "+" and "-" represent the positive sequence and negative sequence, respectively; and They are the positive sequence nth harmonic voltage and initial phase on the AC side respectively; and are the negative sequence voltage and the initial phase of the negative sequence voltage on the AC side respectively; μ is the commutation overlap angle.

[0095] That is, as the commutation overlap angle increases, the voltage transmitted from the AC side to the DC side of the DC transmission system decreases. In order to ensure the design margin and reduce the calculation workload, the commutation angle can be assumed to be zero to retain the calculation margin.

[0096] In the DC circuit of the DC transmission system, there are two main sources of power frequency harmonic voltage. One is the fundamental frequency voltage induced on the DC line by the AC current flowing through the AC line, and the other is the 50Hz AC voltage component on the DC side after the AC bus positive sequence secondary voltage passes through the converter valve. The AC induced voltage along the line is difficult to quantitatively analyze, so in the simulation calculation, only the influence of the AC bus positive sequence secondary voltage is considered. It is generally assumed that the AC bus has a positive sequence secondary voltage equivalent to 1% of the fundamental frequency voltage. It usually occurs when the AC filter and the AC system resonate.

[0097] Therefore, when the harmonic frequency on the DC side of the DC transmission system is 50Hz, the actual harmonic impedance value requirements are as follows: Therefore, the comparative formula for resonance risk judgment can be expressed as:

[0098]

[0099] The generation of second harmonic voltage in DC circuit mainly comes from AC negative sequence fundamental voltage and positive sequence tertiary voltage. For the convenience of analysis, only 2% of the negative sequence fundamental voltage is considered in the calculation. Generally, 1% of the negative sequence fundamental voltage is taken, and considering the influence of the positive sequence tertiary voltage, 2% is taken.

[0100] Therefore, when the harmonic frequency on the DC side of the DC transmission system is 100Hz, the actual harmonic impedance value requirements are as follows: Therefore, the comparative formula for resonance risk judgment can be expressed as:

[0101]

[0102] The following is a description of a resonance risk determination device provided in an embodiment of the present application. The resonance risk determination device described below and the resonance risk determination method described above can be referenced to each other.

[0103] Combination Figure 4 , the resonance risk determination device is introduced, such as Figure 4 As shown, the determination device may include:

[0104] The voltage and current acquisition module 10 is used to acquire the harmonic voltage on the AC side and the harmonic current on the DC side of the DC power transmission system;

[0105] An equipment protection setting value and harmonic coefficient acquisition module 20, used to acquire equipment protection setting values ​​and harmonic coefficients of the DC power transmission system;

[0106] A harmonic impedance threshold obtaining module 30 is used to obtain a harmonic impedance threshold of the DC power transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the device protection setting value and the harmonic coefficient;

[0107] An actual harmonic impedance value acquisition module 40 is used to acquire the actual harmonic impedance value of the DC power transmission system;

[0108] The resonance risk determination module 50 is configured to compare the actual harmonic impedance value with the harmonic impedance threshold value, and determine the resonance risk based on the comparison result.

[0109] Optionally, the harmonic impedance threshold obtaining module 30 in the determination device may include:

[0110] A first threshold value obtaining module, used to obtain a first threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side, and the harmonic coefficient;

[0111] A second threshold value obtaining module is used to obtain the second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting value;

[0112] A comparison module, configured to compare the first threshold with a second threshold;

[0113] The harmonic impedance threshold value finally obtains the module, which is used to take the larger value of the first threshold value and the second threshold value as the harmonic impedance threshold value.

[0114] Furthermore, the embodiment of the present application provides a resonance risk determination device. Optionally, Figure 5 The hardware structure diagram of the resonance risk determination device is shown in FIG. Figure 5 The hardware structure of the resonance risk determination device may include: at least one processor 01 , at least one communication interface 02 , at least one memory 03 and at least one communication bus 04 .

[0115] In the embodiment of the present application, the number of the processor 01 , the communication interface 02 , the memory 03 , and the communication bus 04 is at least one, and the processor 01 , the communication interface 02 , and the memory 03 communicate with each other through the communication bus 04 .

[0116] The processor 01 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0117] The memory 03 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), etc., such as at least one disk memory.

[0118] The memory stores a program, and the processor can call the program stored in the memory, and the program is used to execute the resonance risk determination method described in the method embodiment.

[0119] Optionally, the detailed functions and extended functions of the program may refer to the description of the resonance risk determination method in the method embodiment.

[0120] An embodiment of the present application further provides a storage medium, which can store a program suitable for execution by a processor, and the program is used to execute the resonance risk determination method described in the method embodiment.

[0121] Specifically, the storage medium may be a computer-readable storage medium, and the computer-readable storage medium may be an electronic memory such as a flash memory, an EEPROM (Electrically Erasable Programmable Read-Only Memory), an EPROM, a hard disk or a ROM.

[0122] Optionally, the detailed functions and extended functions of the program may refer to the description of the resonance risk determination method in the method embodiment.

[0123] In addition, the functional modules in the various embodiments of the present disclosure can be integrated together to form an independent part, or each module can exist separately, or two or more modules can be integrated to form an independent part. If the function is implemented in the form of a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present disclosure is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for a computer device (which can be a personal computer, a live broadcast device, or a network device, etc.) to perform all or part of the steps of the methods of the various embodiments of the present disclosure.

[0124] 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.

[0125] 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.

[0126] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. 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 risk determination method, characterized in that: include: Obtaining harmonic voltage on the AC side and harmonic current on the DC side of the DC transmission system; Obtaining equipment protection settings and harmonic coefficients of the DC power transmission system; Obtaining a harmonic impedance threshold of the DC power transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient; Obtaining an actual harmonic impedance value of the DC power transmission system; The actual harmonic impedance value is compared with the harmonic impedance threshold value, and the resonance risk is determined based on the comparison result.

2. The method according to claim 1, characterized in that The step of obtaining the harmonic impedance threshold of the DC power transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting value and the harmonic coefficient includes: Obtaining a first threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side, and the harmonic coefficient; Obtaining a second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting value; comparing the first threshold to a second threshold; The larger value between the first threshold and the second threshold is used as the harmonic impedance threshold.

3. The method according to claim 2, characterized in that The obtaining of the first threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the harmonic coefficient includes: The harmonic voltage on the AC side is represented as U acn , the harmonic current on the DC side is expressed as I dcn , the harmonic coefficient is represented as D, the first threshold is represented as Z1, then according to U acn and I dcn The calculation formula for obtaining the first threshold is: Where n represents the harmonic order.

4. The method according to claim 3, characterized in that: The obtaining of the second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting value comprises: The device protection setting is represented by K, and the second threshold is represented by Z2. acn ,I dcn The calculation formula of the second threshold is obtained by summing K:

5. The method according to claim 1, characterized in that The comparing the actual harmonic impedance value with the harmonic impedance threshold value and determining the resonance risk based on the comparison result includes: Determining whether the actual harmonic impedance value is less than the harmonic impedance threshold; If so, it is determined that the DC power transmission system has a resonance risk.

6. The method according to claim 5, characterized in that Also includes: If it is determined that the actual harmonic impedance value is not less than the harmonic impedance threshold, it is determined that the direct current power transmission system has no resonance risk.

7. A resonance risk determination device, characterized in that: include: A voltage and current acquisition module, used to acquire the harmonic voltage on the AC side and the harmonic current on the DC side of the DC transmission system; An equipment protection setting value and harmonic coefficient acquisition module, used to obtain equipment protection setting values ​​and harmonic coefficients of the DC power transmission system; A harmonic impedance threshold obtaining module, used to obtain the harmonic impedance threshold of the DC power transmission system according to the harmonic voltage on the AC side, the harmonic current on the DC side, the equipment protection setting and the harmonic coefficient; An actual harmonic impedance value acquisition module, used to acquire the actual harmonic impedance value of the DC power transmission system; The resonance risk determination module is used to compare the actual harmonic impedance value with the harmonic impedance threshold value, and determine the resonance risk based on the comparison result.

8. The device according to claim 7, characterized in that The harmonic impedance threshold obtaining module includes: A first threshold value obtaining module, used to obtain a first threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side, and the harmonic coefficient; A second threshold value obtaining module is used to obtain the second threshold value according to the harmonic voltage on the AC side, the harmonic current on the DC side and the equipment protection setting value; A comparison module, configured to compare the first threshold with a second threshold; The harmonic impedance threshold value finally obtains the module, which is used to take the larger value of the first threshold value and the second threshold value as the harmonic impedance threshold value.

9. A resonance risk determination device, characterized in that: including memory and processor; The memory is used to store programs; The processor is used to execute the program to implement each step of the resonance risk determination method according to any one of claims 1 to 6.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, each step of the resonance risk determination method according to any one of claims 1 to 6 is implemented.

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