Harmonic protection method and device for direct-current power transmission system with multiple parallel converters

Abstract

The invention discloses a harmonic protection method and device for a direct-current power transmission system with multiple parallel converters. The method comprises the steps that the direct current of each converter and the current of the pole bus line side are collected; calculating the harmonic content in the direct current of each converter based on the direct current of each converter, and calculating the harmonic content of the pole bus line side current based on the pole bus line side current; configuring harmonic protection for each converter by taking the harmonic content in the direct current of each converter as a fault characteristic quantity; configuring harmonic protection for pole bus public area equipment by taking the harmonic content of the pole bus line side current as a fault characteristic quantity; and determining the converter needing to be locked according to the harmonic endurance capability of the converter, and isolating the locked converter. By adopting the technical scheme of the invention, the equipment can be effectively prevented from being damaged by heat generated by harmonic waves, and the situation that the fault isolation range is expanded due to simultaneous action of harmonic protection of a plurality of converters can be avoided.

Description

Technical Field

[0001] The present invention belongs to the field of direct current transmission, and in particular relates to a harmonic protection method and device for a direct current transmission system with multiple converters connected in parallel. Background Art

[0002] The structure of a DC transmission system with two converters in parallel is as follows: Figure 1 As shown, IDCP1 and IDCN1 are respectively the high and low-end currents of converter 1, and their values ​​are exactly the same when converter 1 is in operation; IDCP2 and IDCN2 are respectively the high and low-end currents of converter 2, and their values ​​are also exactly the same when converter 2 is in operation; IDL is the current on the line side of the pole bus; IDNC is the current on the converter side of the pole neutral bus; IDNE is the current on the line side of the pole neutral bus grounding pole, and the arrow next to the current indicates the positive direction of the current. When converters 1 and 2 are operating normally, IDNE is exactly equal to IDL, and IDNC contains more current from the DC filter branch than IDNE and IDL, but the fundamental wave, second harmonic and other harmonic components that cannot pass through the DC filter branch are exactly the same as IDNE and IDL.

[0003] When extracting the harmonic components of the DC current of converter 1, the harmonic components of IDCN1 can be extracted as the fault characteristic quantity, or the harmonic components of IDCP1 can be extracted as the fault characteristic quantity. When extracting the harmonic components of the DC current of converter 2, the harmonic components of IDCN2 can be extracted as the fault characteristic quantity, or the harmonic components of IDCP2 can be extracted as the fault characteristic quantity. When extracting the harmonic components of the pole bus line side current, the harmonic components of IDL can be extracted as the fault characteristic quantity, or the harmonic components of the pole neutral bus grounding pole line side current IDNE or the harmonic components of the pole neutral bus converter side current IDNC can be extracted as an alternative.

[0004] when Figure 1 When the converter 1 shown in the figure fails, the DC currents IDCP1 and IDCN1 of converter 1, the DC currents IDCP2 and IDCN2 of converter 2, the pole bus line side current IDL, and the pole neutral bus line side current will all have harmonics. If the harmonic tolerance of converter 2 is much lower than that of converter 1, then the harmonic protection of converter 2 may be activated and locked before the harmonic protection of converter 1, which will eventually lead to the failure of isolating the faulty converter 1. Similarly, when converter 2 fails, the harmonic protection of converter 1 may also be activated first, resulting in the failure of isolating the faulty converter 2.

[0005] The innovative point of the patent with the publication number CN105277848A and the invention name "A method for identifying the fault location when the DC harmonic protection is activated" is to simultaneously detect the harmonic components of the DC current on the rectifier side and the inverter side, and use the relative size of the harmonic components of the DC current on both sides to determine whether the actual location of the fault is the rectifier side or the inverter side. The innovative point of the patent with the publication number CN105552835A and the invention name "A method for preventing false operation of 50Hz harmonic protection of DC lines" is to use the AC positive sequence second harmonic voltage to accurately determine the excitation inrush current, and lock the 50Hz harmonic protection when there is an excitation inrush current to prevent the 50Hz harmonic protection from false operation. The innovative point of the patent with the publication number CN105226607A and the invention name "A method for 100Hz harmonic protection of ultra-high voltage DC layered access system" is to determine whether the three-phase voltage on the valve group network side and the extracted second harmonic components in the polar neutral bus current meet the set conditions to identify which AC power grid of the series valve group has a fault.

[0006] In summary, the current harmonic protection has the disadvantage of being unable to accurately identify the faulty converter when applied to a DC transmission system with multiple converters in parallel, and the prior art does not involve harmonic protection for a DC transmission system with multiple converters in parallel. Summary of the invention

[0007] The purpose of the present application is to provide a harmonic protection method and device for a DC transmission system with multiple converters in parallel, so as to solve the problem that the harmonic protection in the DC transmission system with multiple converters in parallel cannot accurately identify the faulty converter, thereby causing the harmonic protection to mistakenly isolate the normal converter and thus expand the fault isolation range.

[0008] In order to achieve the above objectives, this application adopts the following technical solutions:

[0009] According to a first aspect of the present application, a harmonic protection method for a DC power transmission system with multiple converters connected in parallel is proposed, the method comprising:

[0010] Collect the DC current of each converter and the current on the pole bus line side;

[0011] Calculating the harmonic content of the DC current of each converter based on the DC current of each converter, and calculating the harmonic content of the pole bus line side current based on the pole bus line side current;

[0012] configuring harmonic protection for each converter using the harmonic content in the DC current of each converter as a fault characteristic;

[0013] Harmonic protection is configured for the pole bus common area equipment using the harmonic content of the pole bus line side current as a fault characteristic quantity.

[0014] The converter that needs to be blocked is determined by taking into account the harmonic tolerance capability of the converter, and the blocked converter is isolated.

[0015] According to some embodiments, determining a converter that needs to be blocked taking into account the harmonic tolerance capability of the converter, and isolating the blocked converter comprises:

[0016] According to the harmonic tolerance capability of the converter, the converter that needs to be locked is determined by setting the harmonic protection constant or adding the harmonic protection fault converter selection logic, and the locked converter is isolated; the harmonic protection fault converter selection logic is used to determine the converter that needs to be locked according to the harmonic phase and / or amplitude in the converter's DC current.

[0017] According to some embodiments, when the harmonic tolerance capability of each converter is the same and inverse time harmonic protection is adopted, the harmonic protection of all converters is set to the same constant value, and when the harmonic protection of any converter is activated, only the converter is locked, and the remaining converters continue to operate normally after the locked converter is isolated.

[0018] According to some embodiments, when the harmonic tolerance capabilities of the converters are different or time-limited harmonic protection is adopted, harmonic protection is first configured for each converter according to the harmonic tolerance capability of each converter, and then the harmonic protection fault converter selection logic is configured. After the harmonic protection of any converter is actuated, a harmonic protection action signal is sent to the harmonic protection fault converter selection logic. The harmonic protection fault converter selection logic determines the converter that needs to be locked and isolates the locked converter.

[0019] According to some embodiments, the harmonic protection fault converter selection logic is implemented by any of the following methods or a combination of two or more methods. When two or more methods are used in combination, the methods are in an OR relationship:

[0020] Method 1: Calculate the harmonic phase in the DC current of each converter and the harmonic phase of the current on the pole bus line side, and select the converter that has the same harmonic phase as the current on the pole bus line side as the converter that needs to be blocked;

[0021] Method 2: When the total number of parallel converters is greater than or equal to 3, calculate the harmonic phase in the DC current of each converter, and select the converter whose harmonic phase is inconsistent with other converters as the converter that needs to be locked;

[0022] Method 3: Calculate the harmonic phase in the DC current of each converter and the harmonic phase of the current on the pole bus line side, and select the converter that has the same harmonic phase as the current on the pole bus line side but inconsistent with the harmonic phase of other converters as the converter that needs to be blocked;

[0023] Method 4: Calculate the harmonic amplitude in the DC current of each converter and select the converter with the largest amplitude as the converter that needs to be blocked.

[0024] According to some embodiments, the harmonic protection fault converter selection logic further includes, when the converter that needs to be locked cannot be determined based on the harmonic phase and / or amplitude in the converter DC current, selecting the converter in harmonic protection action as the converter that needs to be locked.

[0025] According to some embodiments, the method further comprises: when the harmonic protection of the pole bus common area equipment is activated before the harmonic protection of all converters, locking all converters.

[0026] According to a second aspect of the present application, a harmonic protection device for a DC power transmission system with multiple converters connected in parallel is proposed, comprising:

[0027] Fault collection unit: collects the DC current of each converter and the current on the pole bus line side;

[0028] A calculation unit: calculating the harmonic content in the DC current of each converter based on the DC current of each converter, and calculating the harmonic content of the pole bus line side current based on the pole bus line side current;

[0029] The determination unit: configures harmonic protection for each converter by taking the harmonic content in the DC current of each converter as the fault characteristic; configures harmonic protection for the pole bus common area equipment by taking the harmonic content of the pole bus line side current as the fault characteristic; determines the converter that needs to be locked by taking into account the harmonic tolerance capacity of the converter, and isolates the locked converter.

[0030] According to some embodiments, the determining of the converter that needs to be blocked taking into account the harmonic tolerance capability of the converter and isolating the blocked converter specifically includes:

[0031] According to the harmonic tolerance capability of the converter, the converter that needs to be locked is determined by setting the harmonic protection constant or adding the harmonic protection fault converter selection logic, and the locked converter is isolated; the harmonic protection fault converter selection logic is used to determine the converter that needs to be locked according to the harmonic phase and / or amplitude in the converter's DC current.

[0032] According to some embodiments, the determination unit further comprises: when the harmonic protection of the pole bus common area equipment is activated before the harmonic protection of all converters, all converters are locked.

[0033] According to a third aspect of the present application, an electronic device is proposed, comprising a processor and a memory, wherein the memory stores a program, and the program can be loaded by the processor to execute the aforementioned harmonic protection method for a DC transmission system with multiple converters in parallel.

[0034] According to a fourth aspect of the present application, a computer-readable storage medium is proposed, storing a computer program, characterized in that when the computer program is executed by a processor, the harmonic protection method for a DC transmission system with multiple converters in parallel is implemented.

[0035] Compared with the prior art, the beneficial effect of the present application is that by adopting the technical solution of the present invention, by considering the harmonic tolerance capability of the converter, the faulty valve group causing the harmonic protection action can be effectively detected and isolated in a DC transmission system with multiple converters operating in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The schematic diagram of the converter station structure of a DC transmission system with two converters connected in parallel;

[0037] Figure 2 The schematic diagram of the converter station structure of a DC transmission system with n converters connected in parallel;

[0038] Figure 3 This is a flow chart of an embodiment of a harmonic protection method for a DC power transmission system with multiple converters connected in parallel according to the present application;

[0039] Figure 4 This is a schematic diagram of an embodiment of a harmonic protection device for a DC power transmission system with multiple converters connected in parallel according to the present application.

[0040] Figure 5 A structural diagram of an electronic device provided for this application. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0042] like Figure 3 The flowchart of a harmonic protection method for a DC power transmission system with multiple converters connected in parallel is provided in an embodiment of the present application, and includes the following steps:

[0043] S100: collecting the DC current of each converter and the current on the pole bus line side;

[0044] like Figure 2The schematic diagram of the converter station structure of a DC transmission system with n converters connected in parallel is shown. The DC current of each converter is collected, i.e., IDCN1 or IDCP1 of converter 1 is collected as the DC current of converter 1, IDCN2 or IDCP2 of converter 2 is collected as the DC current of converter 2, ..., IDCNn or IDCPn of converter n is collected as the DC current of converter n. The current on the line side of the pole bus is collected, i.e., the current IDL is directly collected, or IDNE or IDNC is collected as an alternative.

[0045] S200: Calculate the harmonic content in the DC current of each converter based on the DC current of each converter, and calculate the harmonic content of the pole bus line side current based on the pole bus line side current.

[0046] The harmonic content in this embodiment may be the content of the 50 Hz harmonic component or the content of other harmonic components, such as 100 Hz, according to actual engineering conditions.

[0047] S300: configuring harmonic protection for each converter using the harmonic content in the DC current of each converter as a fault characteristic; configuring harmonic protection for the pole bus common area equipment using the harmonic content of the pole bus line side current as a fault characteristic.

[0048] The converter is a key device for realizing AC-DC conversion in the DC transmission system. Due to its working principle, harmonics will inevitably be generated during operation. During normal operation, the harmonic content in the converter DC current is within a certain range. When the converter fails, such as valve short circuit, abnormal trigger pulse, etc., the harmonic content in the DC current will change significantly. Taking these harmonic contents as fault characteristics, by setting reasonable protection thresholds and criteria, when the detected harmonic content exceeds the threshold, the harmonic protection of the converter will be activated.

[0049] The pole bus is a key part connecting the converter and the DC transmission line. The pole bus common area equipment includes busbars, disconnectors, grounding switches, etc. The harmonic content of the pole bus line side current also has a specific distribution and range during normal operation. When the pole bus common area equipment fails, such as bus short circuit, insulation damage, etc., it will cause the harmonic content of the pole bus line side current to be abnormal. Harmonic protection is configured with this harmonic content as the fault characteristic quantity. By monitoring the harmonic changes of the pole bus line side current, when the harmonic content exceeds the normal range and reaches the protection action value, the harmonic protection of the pole bus common area equipment is activated.

[0050] S400: taking into account the harmonic tolerance capability of the converter, determining the converter that needs to be blocked, and isolating the blocked converter.

[0051] As mentioned above, the harmonic tolerance capabilities of the converters may be different. A non-faulty converter may operate before a faulty converter due to its low harmonic tolerance capabilities. Therefore, the harmonic tolerance capabilities of the converters are taken into account to determine the converters that need to be locked and isolate the locked converters.

[0052] In some embodiments, determining a converter that needs to be blocked by taking into account the harmonic tolerance capability of the converter, and isolating the blocked converter specifically includes:

[0053] According to the harmonic tolerance capability of the converter, the converter that needs to be locked is determined by setting the harmonic protection constant or adding the harmonic protection fault converter selection logic, and the locked converter is isolated; the harmonic protection fault converter selection logic is used to determine the converter that needs to be locked according to the harmonic phase and / or amplitude in the converter's DC current.

[0054] In a preferred embodiment, when the harmonic tolerance capability of each converter is the same and inverse time harmonic protection is adopted, the harmonic protection of all converters is set to the same constant value, and when the harmonic protection of any converter is activated, only the converter is locked, and the remaining converters continue to operate normally after the locked converter is isolated.

[0055] In a preferred embodiment, when the harmonic tolerance capabilities of the converters are different or time-limited harmonic protection is adopted, harmonic protection is first configured for each converter according to the harmonic tolerance capability of each converter, and then the harmonic protection fault converter selection logic is configured. After the harmonic protection of any converter is actuated, a harmonic protection action signal is sent to the harmonic protection fault converter selection logic. The harmonic protection fault converter selection logic determines the converter that needs to be locked and isolates the locked converter.

[0056] In a preferred embodiment, the harmonic protection fault converter selection logic is implemented by any of the following methods or a combination of two or more methods. When two or more methods are used in combination, the methods are in an OR relationship:

[0057] Method 1: Calculate the harmonic phase in the DC current of each converter and the harmonic phase of the current on the pole bus line side, and select the converter that has the same harmonic phase as the current on the pole bus line side as the converter that needs to be blocked;

[0058] Method 2: When the total number of parallel converters is greater than or equal to 3, calculate the harmonic phase in the DC current of each converter, and select the converter whose harmonic phase is inconsistent with other converters as the converter that needs to be locked;

[0059] Method 3: Calculate the harmonic phase in the DC current of each converter and the harmonic phase of the current on the pole bus line side, and select the converter that has the same harmonic phase as the current on the pole bus line side but inconsistent with the harmonic phase of other converters as the converter that needs to be blocked;

[0060] Method 4: Calculate the harmonic amplitude in the DC current of each converter and select the converter with the largest amplitude as the converter that needs to be blocked.

[0061] In some embodiments, the harmonic protection fault converter selection logic further includes, when the converter that needs to be locked cannot be determined based on the harmonic phase and / or amplitude in the converter's DC current, selecting the converter in harmonic protection action as the converter that needs to be locked.

[0062] In some embodiments, the harmonic protection method for a DC power transmission system with multiple converters in parallel further includes: when the harmonic protection of the pole bus common area equipment is activated before the harmonic protection of all converters, all converters are locked.

[0063] The following is combined with Figure 2 Explain the specific implementation case 2:

[0064] like Figure 2 As shown, it is assumed that the harmonic tolerance capabilities of converters 1 to n are the same, so the constants of the harmonic protection of converters 1 to n are set to the same value. When the harmonic protection of converter m is activated, only converter m is locked. After converter m is isolated, the other converters continue to operate normally.

[0065] The following is combined with Figure 2 Explain the specific implementation case three:

[0066] like Figure 2 As shown, assuming that the harmonic tolerance capabilities of converters 1 to n are different and converter k has the lowest harmonic tolerance capability, firstly, converters 1 to n are respectively configured with harmonic protection according to their respective harmonic tolerance capabilities, and harmonic protection fault converter selection logic is also configured. The harmonic protection fault converter selection logic receives the harmonic protection action signals of converters 1 to n. When converter m fails, the harmonic protection of converter k may be activated before the harmonic protection of converter m because converter k has the lowest harmonic tolerance capability. The harmonic protection fault converter selection logic selects converter m, whose harmonic phase is consistent with the harmonic phase of the current on the pole bus line side, as the converter that needs to be locked and isolated, rather than converter k for harmonic protection action. After converter m is isolated, the remaining converters still operate normally.

[0067] The following is combined with Figure 2 Explain the specific implementation case 4:

[0068] like Figure 2As shown, assuming that the harmonic tolerance capabilities of converters 1 to n are different and converter k has the lowest harmonic tolerance capability, converters 1 to n are first configured with harmonic protection according to their respective harmonic tolerance capabilities, and harmonic protection fault converter selection logic is also configured. The harmonic protection fault converter selection logic receives the harmonic protection action signals of converters 1 to n. When converter m fails, the harmonic protection of converter k may be activated before the harmonic protection of converter m because converter k has the lowest harmonic tolerance capability. The harmonic protection fault converter selection logic selects converter m, whose harmonic phase is inconsistent with the harmonic phase of other converters, as the converter that needs to be locked and isolated, rather than converter k for harmonic protection action. After converter m is isolated, the remaining converters still operate normally.

[0069] The following is combined with Figure 2 Explain the specific implementation case 5:

[0070] like Figure 2 As shown, assuming that the harmonic tolerance capabilities of converters 1 to n are different and converter k has the lowest harmonic tolerance capability, firstly, converters 1 to n are respectively configured with harmonic protection according to their respective harmonic tolerance capabilities, and harmonic protection fault converter selection logic is also configured. The harmonic protection fault converter selection logic receives the harmonic protection action signals of converters 1 to n. When converter m fails, the harmonic protection of converter k may be activated before the harmonic protection of converter m because converter k has the lowest harmonic tolerance capability. The harmonic protection fault converter selection logic selects converter m, whose harmonic phase is consistent with the harmonic phase of the current on the pole bus line side but inconsistent with the harmonic phase of other converters, as the converter that needs to be locked and isolated, rather than converter k for harmonic protection action. After converter m is isolated, the remaining converters still operate normally.

[0071] The following is combined with Figure 2 Explain the specific implementation case 6:

[0072] like Figure 2As shown, assuming that the harmonic tolerance capabilities of converters 1 to n are different and converter k has the lowest harmonic tolerance capability, firstly, converters 1 to n are respectively configured with harmonic protection according to their respective harmonic tolerance capabilities, and harmonic protection fault converter selection logic is also configured. The harmonic protection fault converter selection logic receives the harmonic protection action signals of converters 1 to n. When an AC field fault occurs, the harmonic protection of converter k may be activated before the harmonic protection of other converters because converter k has the lowest harmonic tolerance capability. At this time, the harmonic phases of converters 1 to n are very likely to be exactly the same. The harmonic protection fault converter selection logic selects converter k for harmonic protection action as the converter that needs to be locked and isolated. After converter k is isolated, the remaining converters still operate normally.

[0073] The following is combined with Figure 2 Explain the specific implementation case seven:

[0074] like Figure 2 As shown, assuming that the harmonic tolerance capabilities of converters 1 to n are different and converter k has the lowest harmonic tolerance capability, firstly, converters 1 to n are respectively configured with harmonic protection according to their respective harmonic tolerance capabilities, and harmonic protection fault converter selection logic is also configured, and the harmonic protection fault converter selection logic receives the harmonic protection action signals of converters 1 to n. The harmonic protection fault converter selection logic selects converter m with the largest harmonic amplitude as the converter that needs to be locked and isolated, rather than converter k for harmonic protection action.

[0075] The following is combined with Figure 2 Explain the specific implementation case eight:

[0076] like Figure 2 As shown, firstly, harmonic protection is configured for converters 1 to converter n and the pole bus common area equipment respectively according to their respective harmonic tolerance capabilities. When the harmonic protection of the pole bus common area equipment is activated before the harmonic protection of all converters, all converters are locked.

[0077] like Figure 4 The figure shows a harmonic protection device 500 for a DC power transmission system with multiple converters connected in parallel provided by an embodiment of the present application, comprising a fault collection unit 501, a calculation unit 502, and a determination unit 503. Among them:

[0078] Fault collection unit 501: collects the DC current of each converter and the current on the pole bus line side.

[0079] The calculation unit 502 calculates the harmonic content in the DC current of each converter based on the DC current of each converter, and calculates the harmonic content of the pole bus line side current based on the pole bus line side current.

[0080] Determination unit 503: configure harmonic protection for each converter based on the harmonic content in the DC current of each converter as a fault characteristic; configure harmonic protection for the pole bus common area equipment based on the harmonic content of the pole bus line side current as a fault characteristic; determine the converter that needs to be locked by taking into account the harmonic tolerance capability of the converter, and isolate the locked converter.

[0081] In a preferred embodiment, the determining of the converter that needs to be blocked taking into account the harmonic tolerance of the converter and isolating the blocked converter specifically includes:

[0082] According to the harmonic tolerance capability of the converter, the converter that needs to be locked is determined by setting the harmonic protection constant or adding the harmonic protection fault converter selection logic, and the locked converter is isolated; the harmonic protection fault converter selection logic is used to determine the converter that needs to be locked according to the harmonic phase and / or amplitude in the converter's DC current.

[0083] In a preferred embodiment, the determination unit further comprises: when the harmonic protection of the pole bus common area equipment is activated before the harmonic protection of all converters, all converters are locked.

[0084] The device performs functions similar to the method provided above. For other functions, please refer to the previous description and will not be repeated here.

[0085] Figure 5 The structure diagram of an electronic device provided by the present application is shown. It includes a processor and a memory. The memory stores computer instructions. When the computer instructions are executed by the processor, the processor executes the computer instructions to achieve the following. Figure 3 The method and refinement scheme shown.

[0086] It should be understood that the above device embodiments are only illustrative, and the device disclosed in the present invention can also be implemented in other ways. For example, the division of units / modules described in the above embodiments is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units, modules or components can be combined, or can be integrated into another system, or some features can be ignored or not executed.

[0087] In addition, unless otherwise specified, each functional unit / module in each embodiment of the present invention may be integrated into one unit / module, each unit / module may exist physically separately, or two or more units / modules may be integrated together. The above-mentioned integrated unit / module may be implemented in the form of hardware or in the form of a software program module.

[0088] If the integrated unit / module is implemented in the form of hardware, the hardware may be a digital circuit, an analog circuit, etc. The physical implementation of the hardware structure includes but is not limited to transistors, memristors, etc. If not otherwise specified, the processor or chip may be any appropriate hardware processor, such as a CPU, a GPU, an FPGA, a DSP, an ASIC, etc. If not otherwise specified, the on-chip cache, the off-chip memory, and the memory may be any appropriate magnetic storage medium or magneto-optical storage medium, such as a resistive random access memory RRAM (Resistive Random Access Memory), a dynamic random access memory DRAM (Dynamic Random Access Memory), a static random access memory SRAM (Static Random-Access Memory), an enhanced dynamic random access memory EDRAM (Enhanced Dynamic Random Access Memory), a high-bandwidth memory HBM (High-Bandwidth Memory), a hybrid memory cube HMC (Hybrid Memory Cube), etc.

[0089] If the integrated unit / module is implemented in the form of a software program module and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a memory and includes several instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present disclosure. The aforementioned memory includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0090] The present application also provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the following Figure 3 The method and refinement scheme shown.

[0091] It should be clearly understood that the present application describes how to form and use specific examples, but the present application is not limited to any details of these examples. On the contrary, based on the teaching of the content disclosed in the present application, these principles can be applied to many other embodiments.

[0092] In addition, it should be noted that the above figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not intended to be limiting. It is easy to understand that the processes shown in the above figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0093] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A harmonic protection method for a DC power transmission system with multiple converters connected in parallel, characterized in that: The method comprises: Collect the DC current of each converter and the current on the pole bus line side; Calculating the harmonic content of the DC current of each converter based on the DC current of each converter, and calculating the harmonic content of the pole bus line side current based on the pole bus line side current; configuring harmonic protection for each converter using the harmonic content in the DC current of each converter as a fault characteristic; Using the harmonic content of the current on the pole bus line side as a fault characteristic quantity, configuring harmonic protection for the pole bus common area equipment; The converter that needs to be blocked is determined by taking into account the harmonic tolerance capability of the converter, and the blocked converter is isolated.

2. The harmonic protection method for a DC power transmission system with multiple converters in parallel as claimed in claim 1, characterized in that: The method of determining the converter that needs to be blocked by taking into account the harmonic tolerance capability of the converter and isolating the blocked converter comprises: According to the harmonic tolerance capability of the converter, the converter that needs to be locked is determined by setting the harmonic protection constant or adding the harmonic protection fault converter selection logic, and the locked converter is isolated; the harmonic protection fault converter selection logic is used to determine the converter that needs to be locked according to the harmonic phase and / or amplitude in the converter's DC current.

3. The harmonic protection method for a DC power transmission system with multiple converters in parallel as claimed in claim 2, characterized in that: When the harmonic tolerance capability of each converter is the same and inverse time harmonic protection is adopted, the harmonic protection of all converters is set to the same constant value, and when the harmonic protection of any converter is activated, only the converter is locked, and the other converters continue to operate normally after the locked converter is isolated.

4. The harmonic protection method for a DC power transmission system with multiple converters in parallel as claimed in claim 2, characterized in that: When the harmonic tolerance capabilities of the converters are different or time-limited harmonic protection is used, first configure harmonic protection for each converter according to its harmonic tolerance capability, and then configure the harmonic protection fault converter selection logic. After the harmonic protection of any converter is actuated, a harmonic protection action signal is sent to the harmonic protection fault converter selection logic. The harmonic protection fault converter selection logic determines the converter that needs to be locked and isolates the locked converter.

5. The harmonic protection method for a DC power transmission system with multiple converters in parallel as claimed in claim 2, characterized in that: The harmonic protection fault converter selection logic is implemented by any of the following methods or a combination of two or more methods. When two or more methods are used in combination, the methods are in an OR relationship: Method 1: Calculate the harmonic phase in the DC current of each converter and the harmonic phase of the current on the pole bus line side, and select the converter that has the same harmonic phase as the current on the pole bus line side as the converter that needs to be blocked; Method 2: When the total number of parallel converters is greater than or equal to 3, calculate the harmonic phase in the DC current of each converter, and select the converter whose harmonic phase is inconsistent with other converters as the converter that needs to be locked; Method 3: Calculate the harmonic phase in the DC current of each converter and the harmonic phase of the current on the pole bus line side, and select the converter that has the same harmonic phase as the current on the pole bus line side but inconsistent with the harmonic phase of other converters as the converter that needs to be blocked; Method 4: Calculate the harmonic amplitude in the DC current of each converter and select the converter with the largest amplitude as the converter that needs to be blocked.

6. A harmonic protection method for a DC power transmission system with multiple converters in parallel as claimed in claim 2, characterized in that: The harmonic protection fault converter selection logic also includes, when the converter that needs to be locked cannot be determined according to the harmonic phase and / or amplitude in the converter DC current, selecting the converter in harmonic protection action as the converter that needs to be locked.

7. The harmonic protection method for a DC power transmission system with multiple converters in parallel as claimed in claim 1, characterized in that: The method further comprises: when the harmonic protection of the pole bus common area equipment is activated before the harmonic protection of all converters, all converters are locked.

8. A harmonic protection device for a DC power transmission system with multiple converters connected in parallel, characterized in that: The device comprises: Fault collection unit: collects the DC current of each converter and the current on the pole bus line side; A calculation unit: calculating the harmonic content in the DC current of each converter based on the DC current of each converter, and calculating the harmonic content of the pole bus line side current based on the pole bus line side current; The determination unit: configures harmonic protection for each converter by taking the harmonic content in the DC current of each converter as the fault characteristic; configures harmonic protection for the pole bus common area equipment by taking the harmonic content of the pole bus line side current as the fault characteristic; determines the converter that needs to be locked by taking into account the harmonic tolerance capacity of the converter, and isolates the locked converter.

9. The device according to claim 8, characterized in that The method of determining a converter that needs to be blocked by taking into account the harmonic tolerance capability of the converter and isolating the blocked converter specifically includes: According to the harmonic tolerance capability of the converter, the converter that needs to be locked is determined by setting the harmonic protection constant or adding the harmonic protection fault converter selection logic, and the locked converter is isolated; the harmonic protection fault converter selection logic is used to determine the converter that needs to be locked according to the harmonic phase and / or amplitude in the converter's DC current.

10. The device according to claim 8, characterized in that The determination unit further includes: when the harmonic protection of the pole bus common area equipment is activated before the harmonic protection of all converters, all converters are locked.

11. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores a program, and the program can be loaded by the processor to execute the method as claimed in any one of claims 1 to 7.

12. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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