Optimization method, control method and device for flexible DC short-delay differential protection

Abstract

The present invention relates to the technical field of power systems, and discloses an optimization method, a control method and a device for flexible direct current short-delay differential protection. The present invention optimizes the differential protection configuration scheme for direct current differential 87DCM protection, wherein a first voltage blocking criterion is added to the corresponding section I, the original second differential current criterion is replaced with the first differential current criterion in the corresponding section II, the original second action delay is extended to the fourth action delay, and the second differential current criterion and the corresponding second action delay are added to the corresponding section III; and the differential protection configuration scheme for AC connection line 87CH protection is optimized, wherein a second voltage blocking criterion is added to the corresponding section I, and the original third differential current criterion and the corresponding fifth action delay are added to the corresponding section II. The present invention can solve the technical problem that when the direct current line of a UHV large-capacity flexible direct current transmission system is struck by lightning, the differential protection malfunctions and blocks the direct current due to the discharge of the arrester.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to an optimization method, a control method and a device for flexible direct current short-delay differential protection. Background Art

[0002] With the gradual maturity of the research and development and application experience of insulated gate bipolar transistor (IGBT) high-power devices, ultra-high voltage and large-capacity flexible DC transmission has become possible. When a ultra-high voltage and large-capacity flexible DC transmission system fails due to lightning strikes, the voltage will rise to a certain extent. In order to limit the voltage rise, a large number of lightning arresters are usually configured in the DC converter station. However, when the DC line is struck by lightning, the lightning arrester will have a discharge current, which will affect the differential protection of the system, causing the differential protection to malfunction and lock the DC.

[0003] In conventional DC, due to the strong overvoltage and overcurrent tolerance of the converter valve, the reference voltage of the arrester can be designed to be higher when the main equipment has sufficient margin. In addition, due to the relatively high setting of the differential protection and the long protection exit time, the arrester discharge current is small and the duration is short under out-of-zone faults, resulting in a lower risk of differential protection action. However, the flexible DC converter valve has a smaller margin for overcurrent and overvoltage. In order to protect the safety of the equipment, the reference voltage of the arrester cannot be too high. At the same time, higher requirements are placed on the rapidity and accuracy of the protection system. The flexible DC differential protection setting is relatively small and the protection exit time is short, which highlights the contradiction between the arrester discharge and the differential protection action.

[0004] Arrester discharge is a transient behavior, usually lasting no more than 3ms. Therefore, the short-delay differential protection with an action delay of less than 5ms is the main cause of coordination problems between arrester discharge and differential protection. In the flexible DC protection system, combined with the location and function of the arrester, the applicant found that the DC differential 87DCM protection section I and the AC connection line 87CH protection section I were the main causes of action due to arrester discharge under DC line lightning faults.

[0005] In the prior art, the criteria for DC differential 87DCM protection and AC connecting line 87CH protection are shown in Table 1, wherein the action delay T1_DCM of the DC differential 87DCM protection section I and the action delay T1_CH of the AC connecting line 87CH protection section I are both less than 5ms.

[0006] Table 1:

[0007]

[0008] In Table 1, IdH is the pole bus DC current, IdN is the neutral line DC current, IvC is the valve side current, IvT is the bushing current on the valve side of the flexible DC transformer, Iset1_DCM is the first differential current criterion constant, and Iset2_DCM is the second differential current criterion constant.

[0009] In view of the risk of DC lockout caused by lightning strike on DC lines resulting in the action of flexible DC 87DCM protection and 87CH protection, an optimization method for flexible DC short-delay differential protection is urgently needed. Summary of the invention

[0010] The present invention provides an optimization method, a control method and a device for flexible direct current short-delay differential protection, optimizes the existing flexible direct current short-delay differential protection criterion, reduces the fault impact range by increasing the voltage criterion and increasing the action delay, and solves the technical problem that when the direct current line of the ultra-high voltage and large-capacity flexible direct current transmission system is struck by lightning, the differential protection malfunctions and blocks the direct current due to the discharge of the lightning arrester.

[0011] A first aspect of the present invention provides an optimization method for flexible DC short-delay differential protection, wherein the flexible DC short-delay differential protection includes DC differential 87DCM protection and AC connecting line 87CH protection, wherein the DC differential 87DCM protection is configured with a first differential current criterion and a corresponding first action delay in the corresponding I section and a second differential current criterion and a corresponding second action delay in the corresponding II section, and the AC connecting line 87CH protection is configured with a third differential current criterion and a corresponding third action delay in the corresponding I section, wherein the first differential current criterion is that the absolute value of the difference between the pole bus DC current and the neutral line DC current is greater than the first differential current criterion constant, the second differential current criterion is that the absolute value of the difference between the pole bus DC current and the neutral line DC current is greater than the second differential current criterion constant, and the third differential current criterion is that the absolute value of the difference between the valve side current and the flexible DC transformer valve side bushing current is greater than the third differential current criterion constant and is differentially operated by phase, and the optimization method comprises:

[0012] The differential protection configuration scheme of the DC differential 87DCM protection is optimized, including: adding a first voltage blocking criterion to the corresponding section I of the DC differential 87DCM protection, wherein the first voltage blocking criterion is that the DC line voltage is less than the first voltage blocking set value; replacing the second differential current criterion with the first differential current criterion in the corresponding section II of the DC differential 87DCM protection, and extending the second action delay to a fourth action delay; adding the second differential current criterion and the corresponding second action delay in the corresponding section III of the DC differential 87DCM protection;

[0013] And, the differential protection configuration scheme of the AC connection line 87CH protection is optimized, including: adding a second voltage lockout criterion to the corresponding section I of the AC connection line 87CH protection, the second voltage lockout criterion being that the valve side voltage is less than the second voltage lockout set value and is differentially operated by phase; adding the third differential current criterion and the corresponding fifth action delay to the corresponding section II of the AC connection line 87CH protection, the fifth action delay being greater than the third action delay.

[0014] According to an achievable manner of the first aspect of the present invention, the optimizing the differential protection configuration scheme of the DC differential 87DCM protection further includes:

[0015] The first voltage blocking value is set to have a value range of 0.9 to 1.1 pu.

[0016] According to an achievable manner of the first aspect of the present invention, the optimizing the differential protection configuration scheme of the DC differential 87DCM protection further includes:

[0017] The value range of the fourth action delay is set to 3 to 6 ms.

[0018] According to an achievable manner of the first aspect of the present invention, the optimization of the differential protection configuration scheme for the AC connection line 87CH protection further includes:

[0019] The second voltage blocking value is set to a value range of 1.2 to 1.5 pu.

[0020] According to an achievable manner of the first aspect of the present invention, the optimization of the differential protection configuration scheme for the AC connection line 87CH protection further includes:

[0021] The value range of the fifth action delay is set to 2.5 to 6 ms.

[0022] According to an achievable manner of the first aspect of the present invention, the optimizing the differential protection configuration scheme of the DC differential 87DCM protection further includes:

[0023] If there are multiple DC line voltage measuring points, the voltage of the DC line voltage measuring point closest to the pole bus DC current measuring point is used as the DC line voltage.

[0024] A second aspect of the present invention provides a control device for flexible DC short-delay differential protection, characterized in that the differential protection configuration scheme of the flexible DC short-delay differential protection is based on the optimization method of the flexible DC short-delay differential protection described in any one of the above achievable methods, and the control device includes:

[0025] The first control module is used to control the corresponding I-stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral DC current satisfying the first differential current criterion reaches the first action delay, and the duration of the DC line voltage satisfying the first voltage blocking criterion reaches the first action delay;

[0026] A second control module is used to control the corresponding II stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral line DC current satisfying the first differential current criterion reaches a fourth action delay;

[0027] The third control module is used to control the corresponding III stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral line DC current satisfying the second differential current criterion reaches the second action delay;

[0028] The fourth control module is used to control the corresponding I-stage action of the AC connection line 87CH protection if the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the third action delay, and the duration of the valve-side voltage satisfying the second voltage blocking criterion reaches the third action delay;

[0029] The fifth control module is used to control the corresponding stage II action of the AC connecting line 87CH protection if the duration of the valve side current and the flexible DC transformer valve side bushing current satisfying the third differential current criterion reaches the fifth action delay.

[0030] A third aspect of the present invention provides a control method for flexible DC short-delay differential protection, characterized in that the differential protection configuration scheme of the flexible DC short-delay differential protection is based on the optimization method of the flexible DC short-delay differential protection described in any one of the above implementation methods, and the control method includes:

[0031] If the duration of the pole busbar DC current and the neutral line DC current satisfying the first differential current criterion reaches the first action delay, and the duration of the DC line voltage satisfying the first voltage blocking criterion reaches the first action delay, the corresponding I stage of the DC differential 87DCM protection is controlled to operate;

[0032] If the duration of the pole busbar DC current and the neutral line DC current satisfying the first differential current criterion reaches the fourth action delay, the corresponding stage II action of the DC differential 87DCM protection is controlled;

[0033] If the duration of the pole busbar DC current and the neutral line DC current satisfying the second differential current criterion reaches the second action delay, the corresponding stage III action of the DC differential 87DCM protection is controlled;

[0034] If the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the third action delay, and the duration of the valve-side voltage satisfying the second voltage blocking criterion reaches the third action delay, the corresponding I stage of the AC connection line 87CH protection is controlled to act;

[0035] If the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the fifth action delay, the corresponding stage II action of the AC connecting line 87CH protection is controlled.

[0036] A fourth aspect of the present invention provides a control device for flexible DC short-delay differential protection, characterized in that it comprises:

[0037] A memory for storing instructions; wherein the instructions are used to implement the control method of the flexible DC short-delay differential protection as described in the above-implemented manner;

[0038] A processor is used to execute instructions in the memory.

[0039] A fifth aspect of the present invention provides a computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the control method of the flexible DC short-delay differential protection as described in the above-implemented manner is implemented.

[0040] It can be seen from the above technical solutions that the present invention has the following advantages:

[0041] The present invention optimizes the differential protection configuration scheme of the DC differential 87DCM protection, wherein a first voltage locking criterion is added to the corresponding section I, the original second differential current criterion is replaced by the first differential current criterion in the corresponding section II, the original second action delay is extended to the fourth action delay, and the second differential current criterion and the corresponding second action delay are added to the corresponding section III; and optimizes the differential protection configuration scheme of the AC connecting line 87CH protection, wherein a second voltage locking criterion is added to the corresponding section I, and the original third differential current criterion and the corresponding fifth action delay are added to the corresponding section II; the present invention avoids power loss caused by differential protection malfunctioning and locking DC by increasing voltage criterion and increasing action delay, can effectively reduce the scope of fault impact, and solves the technical problem that when the DC line of the ultra-high voltage large-capacity flexible DC transmission system is struck by lightning, the differential protection malfunctions and locks DC due to the discharge of the arrester. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 This is a schematic diagram of a DC line of a UHV large-capacity flexible DC transmission system being struck by lightning;

[0044] Figure 2 A topological diagram of a flexible DC short-delay differential protection and a lightning arrester provided in an optional embodiment of the present invention;

[0045] Figure 3 A schematic diagram of an optimization method for flexible DC short-delay differential protection provided by an optional embodiment of the present invention;

[0046] Figure 4 An optional embodiment of the present invention is based on Figure 3 The logic diagram of the differential protection configuration scheme of the DC differential 87DCM protection after optimization by the optimization method shown;

[0047] Figure 5 An optional embodiment of the present invention is based on Figure 3 The logic diagram of the differential protection configuration scheme of the AC connection line 87CH protection after the optimization method is shown;

[0048] Figure 6 A schematic structural diagram of a control device for flexible DC short-delay differential protection provided by an optional embodiment of the present invention;

[0049] Figure 7 A schematic diagram of a control method for flexible DC short-delay differential protection provided in an optional embodiment of the present invention.

[0050] Reference numerals:

[0051] 1-first control module; 2-second control module; 3-third control module; 4-fourth control module; 5-fifth control module. DETAILED DESCRIPTION

[0052] The embodiments of the present invention provide an optimization method, a control method and a device for flexible direct current short-delay differential protection, which are used to solve the technical problem that when a direct current line of a UHV large-capacity flexible direct current transmission system is struck by lightning, the differential protection malfunctions and blocks the direct current due to the discharge of a lightning arrester.

[0053] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below 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.

[0054] The differential protection configuration scheme of the existing flexible DC short-delay differential protection is: the flexible DC short-delay differential protection includes DC differential 87DCM protection and AC connecting line 87CH protection, the DC differential 87DCM protection is configured with a first differential current criterion and a corresponding first action delay in the corresponding I section and a second differential current criterion and a corresponding second action delay in the corresponding II section, the AC connecting line 87CH protection is configured with a third differential current criterion and a corresponding third action delay in the corresponding I section, as shown in Table 1 in the background technology.

[0055] Wherein, the first differential current criterion is that the absolute value of the difference between the pole bus DC current and the neutral line DC current is greater than the first differential current criterion constant, that is, |IdH–IdN|>Iset1_DCM, IdH is the pole bus DC current, IdN is the neutral line DC current, and Iset1_DCM is the first differential current criterion constant;

[0056] The second differential current criterion is that the absolute value of the difference between the pole bus DC current and the neutral line DC current is greater than the second differential current criterion constant, that is, |IdH–IdN|>Iset2_DCM, where Iset2_DCM is the second differential current criterion constant;

[0057] The third differential current criterion is that the absolute value of the difference between the valve side current and the valve side bushing current of the flexible DC transformer is greater than the third differential current criterion constant and is differentially driven by phase, that is, |IvC-IvT|>Iset1_CH (differentially driven by phase), IvC is the valve side current, IvT is the valve side bushing current of the flexible DC transformer, and Iset1_CH is the third differential current criterion constant.

[0058] Based on the differential protection configuration scheme of the flexible DC short-delay differential protection shown in Table 1 in the background technology, when the DC line of the ultra-high voltage large-capacity flexible DC transmission system is subjected to the following Figure 1 When the lightning strike is shown, due to Figure 2 The discharge of the arrester shown in the figure will cause the differential protection to malfunction and block the DC. Figure 2 The arresters in the converter area shown are located within the DC differential protection 87DCM or within the AC link line differential protection 87CH. Figure 2 In the figure, UvC is the valve side voltage and UdL is the DC line voltage.

[0059] To solve the problem of the differential protection misoperation and locking the DC caused by the arrester discharge as described above, the present invention provides an optimization method for flexible DC short-delay differential protection.

[0060] Please refer to Figure 3 , Figure 3 which shows a schematic diagram of an optimization method for flexible DC short-delay differential protection provided by an embodiment of the present invention.

[0061] An optimization method for flexible DC short-delay differential protection provided by an embodiment of the present invention includes:

[0062] Step S1, optimizing the differential protection configuration scheme for the DC differential 87DCM protection, including: adding a first voltage blocking criterion to the corresponding I section of the DC differential 87DCM protection, where the first voltage blocking criterion is that the DC line voltage is less than the first voltage blocking set value; in the corresponding II section of the DC differential 87DCM protection, replacing the second differential current criterion with the first differential current criterion and extending the second action delay to the fourth action delay; in the corresponding III section of the DC differential 87DCM protection, adding the second differential current criterion and the corresponding second action delay;

[0063] And, step S2, optimizing the differential protection configuration scheme for the AC connection line 87CH protection, including: adding a second voltage blocking criterion to the corresponding I section of the AC connection line 87CH protection, where the second voltage blocking criterion is that the valve side voltage is less than the second voltage blocking set value and is phase differential; adding the third differential current criterion and the corresponding fifth action delay to the corresponding II section of the AC connection line 87CH protection, and the fifth action delay is greater than the third action delay.

[0064] It should be noted that steps S1 and S2 are not executed in a specific order.

[0065] To elaborate on the optimization method of the present application in more detail, the following combines Figure 4 to illustrate the differential protection configuration scheme of the DC differential 87DCM protection optimized based on the Figure 3 shown optimization method. As Figure 4 shown, for the optimization of the differential protection configuration scheme of the DC differential 87DCM protection, it includes:

[0066] (1) Adding a voltage blocking criterion to the corresponding I section: UdL < UdL_set, where UdL_set is the first voltage blocking set value;

[0067] Then the original first differential current criterion and the voltage blocking criterion are ANDed to the outlet, and the logic is:

[0068] UdL < UdL_set & |IdH – IdN| > Iset1_DCM;

[0069] The differential current criterion setting value remains unchanged, still being Iset1_DCM; the operating delay of section I remains unchanged, still being T1_DCM (i.e., the first operating delay);

[0070] (2) For section II, the original criterion of section I is adopted: |IdH – IdN| > Iset1_DCM. The differential current criterion setting value remains unchanged, still being Iset1_DCM; the operating delay is extended to T12_DCM (i.e., the fourth operating delay), and T12_DCM > T1_DCM;

[0071] (3) For section III, the original criterion of section II is adopted: |IdH – IdN| > Iset2_DCM. The differential current criterion setting value remains unchanged, still being Iset2_DCM; the operating delay remains unchanged, still being T2_DCM (i.e., the second operating delay).

[0072] Among them, the value of the first voltage blocking lock - in setting UdL_set should consider the following principles:

[0073] Under in - zone faults, UdL < UdL_set should continuously satisfy T1_DCM to ensure the reliable tripping of protection section I; during the lightning arrester discharge process caused by out - of - zone faults, UdL < UdL_set should not continuously satisfy T1_DCM, and protection section I should not trip.

[0074] Based on the above principles, as a feasible implementation method, the value range of UdL_set is set to 0.9 - 1.1 pu. Preferably, the value of UdL_set is set to 1.0 pu.

[0075] Among them, the fourth operating delay T12_DCM should consider the following principles:

[0076] Under the condition of lightning - struck DC lines, the longest time during which the discharge current of the grounding - type lightning arrester within the measurement range of 87DCM protection continuously exceeds Iset1_DCM is less than T12_DCM;

[0077] Under in - zone faults, the optimization scheme of section I of 87DCM protection is withdrawn, and the duration satisfying the first differential current criterion is greater than T12_DCM.

[0078] Based on the above principles, as a feasible implementation method, the value range of T12_DCM is set to 3 - 6 ms. Preferably, the value of T12_DCM is set to 4 ms.

[0079] Based on the above embodiments of the present invention, the comparison of the differential protection configuration scheme of DC differential 87DCM protection before and after optimization is shown in Table 2.

[0080] Table 2:

[0081]

[0082] The following combines Figure 5 to illustrate the differential protection configuration scheme of the AC connection line 87CH protection optimized based on Figure 3 the optimization method shown. As Figure 5 shown, for the optimization of the differential protection configuration scheme of the AC connection line 87CH protection, it includes:

[0083] (1) Add a voltage blocking criterion in the corresponding I segment: UvC < UvC_set, where UvC represents the valve side voltage (three-phase, taking the instantaneous value), and UvC_set represents the second voltage blocking setting value;

[0084] The original third differential current criterion |IvC – IvT| > Iset1_CH and the voltage blocking criterion are taken ANDed by phase and output. The logic is:

[0085] UvCm < UvC_set & |IvCm – IvTm| > Iset1_CH

[0086] In the formula, the subscript m represents phase A / B / C, UvCm represents the valve side voltage of the mth phase, IvCm represents the valve side current of the mth phase, and IvTm is the valve side bushing current of the flexible DC transformer of the mth phase;

[0087] The differential current criterion setting value remains unchanged, still being Iset1_CH; the I segment operation delay remains unchanged, still being T1_CH (i.e., the third operating delay);

[0088] (2) The corresponding II segment follows the original I segment criterion: |IvC – IvT| > Iset1_CH, the differential current criterion setting value remains unchanged, still being Iset1_CH; the operation delay is extended to T12_CH (i.e., the fifth operation delay), and T12_CH > T1_CH.

[0089] Among them, the second voltage blocking setting value UvC_set should consider the following principles:

[0090] Under in-zone faults, UvC < UvC_set should be continuously satisfied for T1_DCM to ensure reliable export of the protection I segment; less than the voltage setting value corresponding to the discharge current of 200A of the valve side arrester (located between the IvC and IvT measurement points).

[0091] Based on the above principles, as a feasible implementation method, the value range of UvC_set is set to 1.2 - 1.5 pu. Preferably, the value of UvC_set is set to 1.3 pu.

[0092] Among them, the fifth operation delay T12_CH should consider the following principles:

[0093] Under the condition of a lightning-struck DC line, the maximum time that the discharge current of the grounding arrester within the 87CH protection measurement point is continuously greater than Iset1_CH is less than T12_CH; under an intra-area fault, the 87CH protection optimization scheme I is exited, and the duration that meets the third differential current criterion is greater than T12_CH.

[0094] Based on the above principle, as an achievable method, the value range of T12_CH is set to 2.5 to 6 ms. Preferably, the value of T12_CH is set to 3 ms.

[0095] Based on the above embodiment of the present invention, a comparison of the differential protection configuration scheme for AC connection line 87CH protection before and after optimization is shown in Table 3.

[0096] Table 3:

[0097]

[0098] The present invention also provides a control device for flexible DC short-delay differential protection, wherein the differential protection configuration scheme of the flexible DC short-delay differential protection is based on the optimization method for flexible DC short-delay differential protection as described in any one of the above achievable methods.

[0099] Figure 6 A schematic structural diagram of a control device for flexible DC short-delay differential protection provided by an embodiment of the present invention is shown.

[0100] A control device for flexible direct current short-delay differential protection provided by an embodiment of the present invention includes:

[0101] The first control module 1 is used to control the corresponding I-stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral DC current satisfying the first differential current criterion reaches the first action delay, and the duration of the DC line voltage satisfying the first voltage blocking criterion reaches the first action delay;

[0102] The second control module 2 is used to control the corresponding II stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral line DC current satisfying the first differential current criterion reaches the fourth action delay;

[0103] The third control module 3 is used to control the corresponding III stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral line DC current satisfying the second differential current criterion reaches the second action delay;

[0104] The fourth control module 4 is used to control the corresponding I-stage action of the AC connection line 87CH protection if the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the third action delay, and the duration of the valve-side voltage satisfying the second voltage blocking criterion reaches the third action delay;

[0105] The fifth control module 5 is used to control the corresponding stage II action of the AC connecting line 87CH protection if the duration of the valve side current and the flexible DC transformer valve side bushing current satisfying the third differential current criterion reaches the fifth action delay.

[0106] The present invention also provides a control method for flexible DC short-delay differential protection, wherein the differential protection configuration scheme of the flexible DC short-delay differential protection is based on the optimization method for the flexible DC short-delay differential protection described in any one of the above embodiments.

[0107] Figure 7 A schematic diagram of a control method for flexible DC short-delay differential protection provided by an embodiment of the present invention is shown.

[0108] A control method for flexible direct current short-delay differential protection provided by an embodiment of the present invention includes:

[0109] Step S10, if the duration of the pole bus DC current and the neutral line DC current satisfying the first differential current criterion reaches the first action delay, and the duration of the DC line voltage satisfying the first voltage blocking criterion reaches the first action delay, control the corresponding I stage of the DC differential 87DCM protection to act;

[0110] Step S20, if the duration of the pole bus DC current and the neutral line DC current satisfying the first differential current criterion reaches the fourth action delay, controlling the corresponding II stage of the DC differential 87DCM protection to act;

[0111] Step S30, if the duration of the pole bus DC current and the neutral line DC current satisfying the second differential current criterion reaches the second action delay, controlling the corresponding stage III action of the DC differential 87DCM protection;

[0112] Step S40, if the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the third action delay, and the duration of the valve-side voltage satisfying the second voltage blocking criterion reaches the third action delay, the corresponding I-stage action of the AC connection line 87CH protection is controlled;

[0113] Step S50: If the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third current difference criterion reaches the fifth action delay, the corresponding stage II action of the AC connection line 87CH protection is controlled.

[0114] It should be noted that the execution order of the above steps S10-S50 is not specific.

[0115] The present invention also provides a control device for flexible DC short-delay differential protection, comprising:

[0116] A memory, used to store instructions; wherein the instructions are used to implement the control method of the flexible DC short-delay differential protection as described in the above embodiment;

[0117] A processor is used to execute instructions in the memory.

[0118] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the control method of the flexible DC short-delay differential protection as described in the above embodiment is implemented.

[0119] The above-mentioned embodiments of the present invention avoid power loss caused by malfunction of differential protection and locking of DC by adding voltage criteria and increasing action delay, and can effectively reduce the scope of fault impact, thereby solving the technical problem of malfunction of differential protection and locking of DC due to discharge of lightning arrester when the DC line of the ultra-high voltage and large-capacity flexible DC transmission system is struck by lightning.

[0120] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the control device embodiments described above are only schematic, for example, the division of the modules is only a logical function division, and there may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another device, or some features can be ignored or not executed.

[0121] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0122] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of software functional modules.

[0123] If the integrated module is implemented in the form of a software function 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 invention is essentially 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. The computer software product is stored in a storage medium, including 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 invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0124] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optimization method for flexible DC short-delay differential protection, the flexible DC short-delay differential protection includes DC differential 87DCM protection and AC connecting line 87CH protection, the DC differential 87DCM protection is configured with a first differential current criterion and a corresponding first action delay in the corresponding I section and a second differential current criterion and a corresponding second action delay in the corresponding II section, the AC connecting line 87CH protection is configured with a third differential current criterion and a corresponding third action delay in the corresponding I section, the first differential current criterion is that the absolute value of the difference between the pole bus DC current and the neutral DC current is greater than the first differential current criterion constant, the second differential current criterion is that the absolute value of the difference between the pole bus DC current and the neutral DC current is greater than the second differential current criterion constant, the third differential current criterion is that the absolute value of the difference between the valve side current and the flexible DC transformer valve side bushing current is greater than the third differential current criterion constant and is differentially operated by phase, characterized in that The optimization method comprises: The differential protection configuration scheme of the DC differential 87DCM protection is optimized, including: adding a first voltage blocking criterion to the corresponding section I of the DC differential 87DCM protection, wherein the first voltage blocking criterion is that the DC line voltage is less than the first voltage blocking set value; replacing the second differential current criterion with the first differential current criterion in the corresponding section II of the DC differential 87DCM protection, and extending the second action delay to a fourth action delay; adding the second differential current criterion and the corresponding second action delay in the corresponding section III of the DC differential 87DCM protection; And, the differential protection configuration scheme of the AC connection line 87CH protection is optimized, including: adding a second voltage lockout criterion to the corresponding section I of the AC connection line 87CH protection, the second voltage lockout criterion being that the valve side voltage is less than the second voltage lockout set value and is differentially operated by phase; adding the third differential current criterion and the corresponding fifth action delay to the corresponding section II of the AC connection line 87CH protection, the fifth action delay being greater than the third action delay.

2. The optimization method for flexible DC short-delay differential protection according to claim 1, characterized in that: The step of optimizing the differential protection configuration scheme for the DC differential 87DCM protection further includes: The first voltage blocking value is set to have a value range of 0.9 to 1.1 pu.

3. The optimization method for flexible DC short-delay differential protection according to claim 1, characterized in that: The step of optimizing the differential protection configuration scheme for the DC differential 87DCM protection further includes: The value range of the fourth action delay is set to 3 to 6 ms.

4. The optimization method for flexible DC short-delay differential protection according to claim 1, characterized in that: The optimization of the differential protection configuration scheme for the AC connection line 87CH protection also includes: The second voltage blocking value is set to a value range of 1.2 to 1.5 pu.

5. The optimization method for flexible DC short-delay differential protection according to claim 1, characterized in that: The optimization of the differential protection configuration scheme for the AC connection line 87CH protection also includes: The value range of the fifth action delay is set to 2.5 to 6 ms.

6. The optimization method for flexible DC short-delay differential protection according to claim 1, characterized in that: The step of optimizing the differential protection configuration scheme for the DC differential 87DCM protection further includes: If there are multiple DC line voltage measuring points, the voltage of the DC line voltage measuring point closest to the pole bus DC current measuring point is used as the DC line voltage.

7. A control device for flexible DC short-delay differential protection, characterized in that: The differential protection configuration scheme of the flexible DC short-delay differential protection is based on the optimization method of the flexible DC short-delay differential protection according to any one of claims 1 to 6, and the control device includes: The first control module is used to control the corresponding I-stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral DC current satisfying the first differential current criterion reaches the first action delay, and the duration of the DC line voltage satisfying the first voltage blocking criterion reaches the first action delay; A second control module is used to control the corresponding II stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral line DC current satisfying the first differential current criterion reaches a fourth action delay; The third control module is used to control the corresponding III stage action of the DC differential 87DCM protection if the duration of the pole bus DC current and the neutral line DC current satisfying the second differential current criterion reaches the second action delay; The fourth control module is used to control the corresponding I-stage action of the AC connection line 87CH protection if the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the third action delay, and the duration of the valve-side voltage satisfying the second voltage blocking criterion reaches the third action delay; The fifth control module is used to control the corresponding stage II action of the AC connecting line 87CH protection if the duration of the valve side current and the flexible DC transformer valve side bushing current satisfying the third differential current criterion reaches the fifth action delay.

8. A control method for flexible DC short-delay differential protection, characterized in that: The differential protection configuration scheme of the flexible DC short-delay differential protection is based on the optimization method of the flexible DC short-delay differential protection according to any one of claims 1 to 6, and the control method includes: If the duration of the pole busbar DC current and the neutral line DC current satisfying the first differential current criterion reaches the first action delay, and the duration of the DC line voltage satisfying the first voltage blocking criterion reaches the first action delay, the corresponding I stage of the DC differential 87DCM protection is controlled to operate; If the duration of the pole busbar DC current and the neutral line DC current satisfying the first differential current criterion reaches the fourth action delay, the corresponding stage II action of the DC differential 87DCM protection is controlled; If the duration of the pole busbar DC current and the neutral line DC current satisfying the second differential current criterion reaches the second action delay, the corresponding stage III action of the DC differential 87DCM protection is controlled; If the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the third action delay, and the duration of the valve-side voltage satisfying the second voltage blocking criterion reaches the third action delay, the corresponding I stage of the AC connection line 87CH protection is controlled to act; If the duration of the valve-side current and the flexible DC transformer valve-side bushing current satisfying the third differential current criterion reaches the fifth action delay, the corresponding stage II action of the AC connecting line 87CH protection is controlled.

9. A control device for flexible DC short-delay differential protection, characterized in that: include: A memory for storing instructions; wherein the instructions are used to implement the control method of the flexible DC short-delay differential protection according to claim 8; A processor is used to execute instructions in the memory.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by the processor, the control method of the flexible DC short-delay differential protection according to claim 8 is implemented.

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