Method for determining the distance protection of AC lines at the receiving end of a new energy transmission system via flexible direct transmission

Abstract

This invention discloses a method for determining distance protection on the receiving-end AC line of a new energy transmission system via flexible direct current transmission. The method includes: collecting voltage and current data of the three phases at the protection point, wherein the protection point is located on the AC line from the flexible direct current transmission system to the receiving end; calculating the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero-sequence current phasor for each of the three phases based on the voltage and current data; calculating the phase-to-phase phase difference / phase-to-phase phase difference of the three phases at the protection point based on the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero-sequence current phasor; and determining whether the distance protection at the protection point is activated based on the phase-to-phase phase difference / phase-to-phase phase difference.

Description

Technical Field

[0001] This invention relates to the field of power grid technology, and more specifically, to a method for determining the distance protection of AC lines at the receiving end of a new energy transmission system via flexible direct transmission. Background Technology

[0002] In recent years, my country's installed capacity and power generation of new energy sources have grown rapidly. In the future, the proportion of new energy sources in the new power system will further increase. Large-scale new energy transmission via flexible DC transmission lines has become a typical scenario in the new power system. Several large-scale new energy transmission projects via flexible DC transmission lines have been put into operation in my country. Among them, the onshore Zhangbei ±500kV four-terminal flexible DC grid and the Rudong offshore wind power transmission project were put into operation in 2020 and 2021, respectively.

[0003] Distance protection is the most important backup protection for high-voltage lines. In engineering, phase-comparison distance protection with positive-sequence voltage polarization is commonly used, distinguishing between internal and external faults by comparing the phase relationship between the compensation voltage and the polarization voltage. When a fault occurs on the receiving-end AC line of a new energy transmission system via flexible DC transmission, the short-circuit current characteristics provided by the flexible DC side differ significantly from those of conventional power supplies due to the characteristics of power electronic devices and control strategies. This can lead to incorrect operation of the AC line distance protection. Domestic and international scholars have conducted theoretical analysis and simulation verification work on this issue. Currently, the impact of flexible DC side control strategies on the electrical characteristics of the fault and distance protection after an AC system fault focuses on the case of short-circuit faults through transition resistors. However, faults through transition resistors are only a part of short-circuit faults, and the existing analysis of the adaptability of distance protection under metallic fault conditions is not yet complete. Existing fault control strategies are complex and diverse, and the impact of fault types on distance protection is also different; the adaptability of distance protection under various operating conditions still needs to be explored. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for determining the distance protection of AC lines at the receiving end of a new energy transmission system via flexible direct transmission.

[0005] According to one aspect of the present invention, a method for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission is provided, comprising:

[0006] The voltage and current data of the three phases are collected by phase, and the protection point is set on the AC line from the flexible DC transmission system to the receiving end.

[0007] Based on the voltage and current data, calculate the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero sequence current phasor for each of the three phases.

[0008] Based on the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero sequence current phasor, calculate the phase difference / phase-to-phase difference of the three phases at the protection point.

[0009] Determine whether the distance protection at the protected location is activated based on the phase difference between phases or the phase difference between phases.

[0010] Optionally, the operation of determining whether the distance protection at the protected location is activated based on the phase difference / inter-phase phase difference includes:

[0011] Based on the protection action boundary, the preset margin value, and the phase difference / phase-to-phase difference, determine whether the distance protection at the protection point is activated.

[0012] Optionally, based on the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero-sequence current phasor, the formula for calculating the phase difference of the three phases at the protection point is as follows:

[0013]

[0014] in, These are positive-sequence phase voltage phasors. For phase current phasors, Here is the zero-sequence current phasor, where k = (Z0 - Z1) / 3Z1, where Z0 is the zero-sequence impedance and Z1 is the positive-sequence impedance.

[0015] Optionally, based on the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor and the phase current phasor / phase-to-phase current phasor, the calculation formula for the phase-to-phase phase difference of the three phases at the protection point is as follows:

[0016]

[0017] in, These are positive-sequence phase-to-phase voltage phasors. Let be the phase current phasor, where

[0018] Optionally, the operation of determining whether to activate distance protection at the protection point based on the protection action boundary, a preset margin value, and the phase difference includes:

[0019] exist Under the first condition of judgment, the distance protection at the protected location is activated, wherein, Based on phase difference, θ is the protection action boundary, and γ is the margin value;

[0020] Under the first judgment condition, the distance protection at the protected location is turned off.

[0021] Optionally, the operation of determining whether to activate distance protection at the protection point based on the protection action boundary, a preset margin value, and the phase-to-phase difference includes:

[0022] exist Under the second condition, the distance protection at the protected location is activated, wherein... Based on the phase difference between phases, θ is the protection action boundary, and γ is the margin value;

[0023] Under the second condition, the distance protection at the protected location is turned off.

[0024] According to another aspect of the present invention, a device for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission is provided, comprising:

[0025] The acquisition module is used to acquire the voltage and current data of the three phases at the protection point, which is located on the AC line from the flexible DC transmission system to the receiving end.

[0026] The first calculation module is used to calculate the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero sequence current phasor of the three phases based on voltage and current data.

[0027] The second calculation module is used to calculate the phase difference / phase difference between the three phases at the protection point based on the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor and zero sequence current phasor.

[0028] The determination module is used to determine whether the distance protection at the protected location is activated based on the phase difference between phases / phases between phases.

[0029] According to another aspect of the present invention, a computer-readable storage medium is provided, the storage medium storing a computer program for performing the methods described in any of the above aspects of the present invention.

[0030] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method described in any of the preceding aspects of the present invention.

[0031] Therefore, the method for determining the distance protection of the receiving-end AC line in a new energy transmission system provided by this invention uses the measured voltage and current values ​​on the local side of the line protection point. The applicability of the distance protection principle is determined by judging the phase relationship between the positive sequence voltage and the measured current values. When the distance protection principle is applicable, the distance protection can be activated. When the distance protection principle fails, relevant measures such as disabling the distance protection must be taken to prevent incorrect operation of the distance protection. Attached Figure Description

[0032] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures:

[0033] Figure 1 This is a flowchart illustrating a method for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission, provided by an exemplary embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a fault in the receiving end AC line of a new energy transmission system via flexible direct transmission, provided by an exemplary embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram illustrating the operating principle of distance protection under metallic fault conditions within a conventional power grid line area, provided by an exemplary embodiment of the present invention.

[0036] Figure 4A This is a schematic diagram of the adaptability of phase-to-phase short-circuit fault distance protection within the flexible DC receiving-end line area provided by an exemplary embodiment of the present invention;

[0037] Figure 4B This is a schematic diagram illustrating the adaptability of distance protection for phase-to-phase short-circuit faults outside the reverse zone of a flexible DC receiving-end line according to an exemplary embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of the voltage waveform for flexible DC side protection provided in an exemplary embodiment of the present invention;

[0039] Figure 6 This is a schematic diagram of the measured current waveform for flexible DC side protection provided in an exemplary embodiment of the present invention;

[0040] Figure 7 This is a schematic diagram of the operation of the inter-phase distance protection stage I during an intra-zone fault, provided by an exemplary embodiment of the present invention.

[0041] Figure 8 This is a schematic diagram of the operation of the phase-to-phase distance protection stage I under a reverse zone external fault provided in an exemplary embodiment of the present invention;

[0042] Figure 9 This is a schematic diagram of the structure of a device for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission, provided in an exemplary embodiment of the present invention.

[0043] Figure 10 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. Detailed Implementation

[0044] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0045] It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention.

[0046] Those skilled in the art will understand that the terms "first," "second," etc., in the embodiments of the present invention are only used to distinguish different steps, devices, or modules, and do not represent any specific technical meaning, nor do they indicate a necessary logical order between them.

[0047] It should also be understood that in the embodiments of the present invention, "multiple" can refer to two or more, and "at least one" can refer to one, two or more.

[0048] It should also be understood that any component, data or structure mentioned in the embodiments of the present invention can generally be understood as one or more unless explicitly defined or given contrary instructions in the context.

[0049] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0050] It should also be understood that the description of the various embodiments in this invention emphasizes the differences between the various embodiments, and the similarities or similarities can be referred to each other. For the sake of brevity, they will not be described in detail.

[0051] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0052] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0053] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0054] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0055] The embodiments of this invention can be applied to electronic devices such as terminal devices, computer systems, and servers, and can operate together with a wide range of other general-purpose or special-purpose computing system environments or configurations. Well-known examples of terminal devices, computing systems, environments, and / or configurations suitable for use with electronic devices such as terminal devices, computer systems, and servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments including any of the above systems, etc.

[0056] Electronic devices such as terminal devices, computer systems, and servers can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers can be implemented in distributed cloud computing environments, where tasks are executed by remote processing devices linked through communication networks. In distributed cloud computing environments, program modules can reside on local or remote computing system storage media, including storage devices.

[0057] Exemplary methods

[0058] Figure 1 This is a flowchart illustrating a method for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission, provided by an exemplary embodiment of the present invention. This embodiment can be applied to electronic devices, such as… Figure 1 As shown, the method 100 for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission includes the following steps:

[0059] Step 101: Collect the voltage and current data of the three phases at the protection point, wherein the protection point is set on the AC line from the flexible DC transmission system to the receiving end.

[0060] Step 102: Based on the voltage and current data, calculate the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero sequence current phasor for each of the three phases.

[0061] Step 103: Calculate the phase difference / phase-to-phase difference of the three phases at the protection point based on the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor and zero sequence current phasor.

[0062] Step 104: Determine whether the distance protection at the protection point is activated based on the phase difference between phases / phase-to-phase difference.

[0063] Specifically, Figure 2 This diagram illustrates a fault in the receiving-end AC line of a new energy transmission system via flexible direct current transmission. (Reference) Figure 1 and Figure 2 As shown, the protection points can be located at points M and N between the flexible DC transmission line and the receiving-end AC grid. The number and location of these protection points are not limited in this scheme and can be set by the user according to their needs. The new energy source can be wind power. For example, by collecting the three-phase voltage at protection points M and N, six sets of voltage and current data can be collected.

[0064] Therefore, the method for determining the distance protection of the receiving-end AC line in a new energy transmission system provided by this invention uses the measured voltage and current values ​​on the local side of the line protection point. The applicability of the distance protection principle is determined by judging the phase relationship between the positive sequence voltage and the measured current values. When the distance protection principle is applicable, the distance protection can be activated. When the distance protection principle fails, relevant measures such as disabling the distance protection must be taken to prevent incorrect operation of the distance protection.

[0065] Optionally, the operation of determining whether the distance protection at the protected location is activated based on the phase difference / inter-phase phase difference includes:

[0066] Based on the protection action boundary, the preset margin value, and the phase difference / phase-to-phase difference, determine whether the distance protection at the protection point is activated.

[0067] Optionally, based on the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero-sequence current phasor, the formula for calculating the phase difference of the three phases at the protection point is as follows:

[0068]

[0069] in, These are positive-sequence phase voltage phasors. For phase current phasors, Here is the zero-sequence current phasor, where k = (Z0 - Z1) / 3Z1, where Z0 is the zero-sequence impedance and Z1 is the positive-sequence impedance.

[0070] Optionally, based on the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor and the phase current phasor / phase-to-phase current phasor, the calculation formula for the phase-to-phase phase difference of the three phases at the protection point is as follows:

[0071]

[0072] in, These are positive-sequence phase-to-phase voltage phasors. Let be the phase current phasor, where

[0073] Optionally, the operation of determining whether to activate distance protection at the protection point based on the protection action boundary, a preset margin value, and the phase difference includes:

[0074] exist Under the first condition of judgment, the distance protection at the protected location is activated, wherein, Based on phase difference, θ is the protection action boundary, and γ is the margin value;

[0075] Under the first judgment condition, the distance protection at the protected location is turned off.

[0076] Optionally, the operation of determining whether to activate distance protection at the protection point based on the protection action boundary, a preset margin value, and the phase-to-phase difference includes:

[0077] exist Under the second condition, the distance protection at the protected location is activated, wherein... Based on the phase difference between phases, θ is the protection action boundary, and γ is the margin value;

[0078] Under the second condition, the distance protection at the protected location is turned off.

[0079] Specifically, (1) collect the voltage u(t) and current i(t) at the protection point on this side according to phase, and calculate the voltage phasor of each phase. and phase current phasors

[0080] (2) Calculate the positive sequence phase voltage phasors respectively. in Calculate the positive sequence phase-to-phase voltage phasor Calculate the interphase current phasor Zero-sequence current phasor

[0081] (3) Based on the protection activation status, calculate the protection installation location per phase. Or calculated by phase intervals

[0082] (4) Combining the protection action boundary θ, and considering a certain margin γ, when or When the distance protection is open, the distance protection is activated; otherwise, the distance protection on both sides is locked.

[0083] In addition, existing positive sequence voltage polarization ratio-based distance protection criteria:

[0084]

[0085] in To compensate for voltage, For grounding distance relays, the set impedance is measured at the voltage. Measuring current The subscripts 0 and 1 represent the zero-sequence and positive-sequence components, respectively. For phase-to-phase distance relays... Polarization voltage is used to reflect the voltage phase before a fault, providing a phase reference for the compensation voltage. Positive sequence voltage is commonly used as the polarization quantity. θ is the protection action boundary, generally taken as 90°. The distance protection action principle diagram for a metallic fault within the time zone when θ = 90° is shown below. Figure 2 The diagram illustrates the operating principle of distance protection in the event of a metallic fault within a traditional power grid line area. Figure 2 China E M E N These are the power supply potentials on the protection side and the opposite side, respectively. When a metal fault occurs within the zone... At that time, distance protection is most sensitive. or At that time, the distance protection is located at the action boundary.

[0086] To further analyze the relationship between distance protection adaptability and measurement quantities, Substituting θ = 90° into equation (1), where Z K To protect the impedance between the installation point and the fault point, the ratio-based distance protection criterion with positive sequence voltage polarization can be expressed as:

[0087]

[0088] The action characteristics of further splitting (2): Distance protection aims to determine Z by k With Z set The size relationship distinguishes faults inside and outside the line area, i.e., arg(1 / (Z) k -Z set ))part.

[0089] In the event of a metallic fault within the zone, assuming the line impedance angle is equal to the set impedance angle, use... Indicates (generally) ), that is, arg(1 / (Z k -Z set ))=90°, by Figure 1 It can be seen that at this time Distance protection is the most sensitive and reliable. In the event of a metallic fault outside the protection zone, and The phase remains approximately unchanged, arg(1 / (Z) k -Zset )) = -90°, at this time The distance protection function is reliable and does not activate.

[0090] The above analysis shows that the adaptability of distance protection is... and arg(1 / (Z) k -Z set The decision is made jointly by two parts. In traditional power grids, and The phase is mainly affected by the system power angle and transition resistance. In actual system operation, the power angle is relatively small during stable operation, especially under metallic fault conditions. Therefore, the distance protection action is mainly determined by arg(1 / (Z)). k -Z set )) Decision: In the case of a metallic fault within the zone, arg(1 / (Z) k -Z set When the angle is 90°, and there is a metallic fault outside the zone, arg(1 / (Z)) = 90°. k -Z set ))=-90°.

[0091] Unlike traditional power grids, renewable energy power grids are affected by power electronic control, and after a fault... and The phase is controlled and no longer satisfies condition, The value will affect the adaptability of distance protection. Considering the protection action boundary θ and a certain margin γ, let Z... set Phase angle is (Generally, the value is a fixed value of 87°, but this scheme uses a value of 90°), when Distance protection has the highest sensitivity; when or Distance protection sensitivity decreases, but it still has some adaptability; except for the above situations, distance protection adaptability is insufficient, and it is recommended to disable distance protection.

[0092] In addition, (1) there is a risk of distance protection failing to operate during metallic faults within the zone:

[0093] With attachment Figure 2 Taking the F1-point flexible DC transmission system as an example, where a phase-to-phase fault (BC phase) occurs on the receiving-end AC line, for the distance protection on the M side, after the fault... and Phase control: Taking the receiving-end converter station using unit factor control and negative sequence current suppression strategy after a fault as an example, at this time... because Therefore In this situation, the distance protection action is as follows: Figure 4A As shown: When Z k With Z set Phase is and At that time, it can be seen Located at the action boundary, the distance protection sensitivity is low, and its ability to withstand signal transmission and calculation errors is poor. Furthermore, when Z... k Phase angle greater than Z set At phase angles, the adaptability of distance protection will be further reduced, and the phenomenon of distance protection refusing to operate may occur.

[0094] (2) Distance protection is at risk of maloperation during metallic faults outside the reverse zone.

[0095] With attachment Figure 2 Taking a phase-to-phase (BC) fault on the receiving-end AC line of the flexible DC transmission system at point F2 as an example, for the distance protection on the N side, after the fault... and Phase control: Taking the receiving-end converter station using unit factor control and negative sequence current suppression strategy after a fault as an example, at this time... because Therefore In this situation, the distance protection action is as follows: Figure 4B As shown: When Z k With Z set Phase is and At that time, it can be seen Located at the action boundary, it has poor tolerance to signal transmission and calculation errors, and when Z k Phase angle greater than Z set When the phase angle is too high, the adaptability of the distance protection will be further reduced, and the distance protection may malfunction.

[0096] Furthermore, the method provided in this application is implemented as follows:

[0097] The following setup was built in the PSCAD / EMTDC simulation platform. Figure 1 The end-to-end flexible DC transmission system model shown depicts a receiving-end converter station that, after a fault, adopts a unity power factor control strategy and a negative sequence current suppression strategy to connect to a 500kV AC system. The AC line length is 20km, the positive sequence impedance per unit length of the transmission line is 0.034+j0.375Ω / km, the zero sequence impedance is 0.256+j1.266Ω / km, and the inter-line mutual inductance is 0.259+j0.763Ω / km.

[0098] (1) Fault distance protection in the forward zone fails to operate

[0099] A metallic phase-to-phase fault (BC) occurs at point F1 in the diagram. The fault duration is 0.2s, and it disappears after 0.6s. The voltage and current waveforms measured at the protection device on side M after the fault are shown below. Figure 5 , 6As shown. When θ is 90°, the operating range is 90°~270°, and the distance protection operation is as follows. Figure 7 As shown.

[0100] (2) Malfunction of the reverse zone fault distance protection

[0101] When a phase-to-phase short-circuit fault occurs at point F2 on the AC line, the protection operation of the phase-to-phase distance relay with positive sequence voltage polarization on the N side is as follows: Figure 8 As shown.

[0102] Therefore, the method for determining the distance protection of the receiving-end AC line in a new energy transmission system provided by this invention uses the measured voltage and current values ​​on the local side of the line protection point. The applicability of the distance protection principle is determined by judging the phase relationship between the positive sequence voltage and the measured current values. When the distance protection principle is applicable, the distance protection can be activated. When the distance protection principle fails, relevant measures such as disabling the distance protection must be taken to prevent incorrect operation of the distance protection.

[0103] Exemplary device

[0104] Figure 9 This is a schematic diagram of the structure of a device for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission, provided in an exemplary embodiment of the present invention. Figure 9 As shown, the device 900 includes:

[0105] The acquisition module 910 is used to acquire voltage and current data of the three phases at the protection point, wherein the protection point is installed on the AC line from the flexible DC transmission system to the receiving end.

[0106] The first calculation module 920 is used to calculate the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero sequence current phasor of the three phases respectively based on the voltage data and the current data.

[0107] The second calculation module 930 is used to calculate the phase difference / phase difference between the three phases at the protection point based on the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, the phase current phasor / phase-to-phase current phasor and the zero sequence current phasor.

[0108] The determination module 940 is used to determine whether the distance protection at the protection point is activated based on the phase difference / phase-to-phase difference.

[0109] Optionally, module 940 is defined, including:

[0110] The determination submodule is used to determine whether the distance protection at the protection point is activated based on the protection action boundary, the preset margin value, and the phase difference / interphase difference.

[0111] Optionally, the calculation formula of the second calculation module 930 is as follows:

[0112]

[0113] in, The positive-sequence phase voltage phasor. The phase current phasor. Let be the zero-sequence current phasor, where k = (Z0 - Z1) / 3Z1, where Z0 is the zero-sequence impedance and Z1 is the positive-sequence impedance.

[0114] Optionally, the calculation formula of the second calculation module 930 is as follows:

[0115]

[0116] in, The positive-sequence interphase voltage phasor. Let be the phase current phasor, where

[0117] Optionally, module 940 is defined, including:

[0118] The first enabling submodule is used to... Under the first determination condition, the distance protection at the protected location is activated, wherein, Based on the phase difference, θ is the protection action boundary, and γ is the margin value;

[0119] The first closing submodule is used to close the distance protection at the protected location under the first determination condition.

[0120] Optionally, module 940 is defined, including:

[0121] The second enabling submodule is used to... Under the second determination condition, the distance protection at the protected location is activated, wherein, Based on the phase difference between phases, θ is the protection action boundary, and γ is the margin value;

[0122] The second shut-off submodule is used to shut off the distance protection at the protected location under the second determination condition.

[0123] Exemplary electronic devices

[0124] Figure 10This is the structure of an electronic device provided in an exemplary embodiment of the present invention. The electronic device may be either or both of a first device and a second device, or a standalone device independent of them, which may communicate with the first device and the second device to receive acquired input signals from them. Figure 10 A block diagram of an electronic device according to an embodiment of the present invention is illustrated. Figure 10 As shown, the electronic device 100 includes one or more processors 101 and memory 102.

[0125] The processor 101 may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0126] The memory 102 may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may include, for example, random access memory (RAM) and / or cache memory. The non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. One or more computer program instructions may be stored on the computer-readable storage medium, and the processor 101 may execute the program instructions to implement the methods for information mining of historical change records and / or other desired functions of the software programs of the various embodiments of the present invention described above. In one example, the electronic device may also include an input device 103 and an output device 104, which are interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0127] In addition, the input device 103 may also include, for example, a keyboard, a mouse, etc.

[0128] The output device 104 can output various information to the outside. The output device 104 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0129] Of course, for the sake of simplicity, Figure 10 Only some of the components of the electronic device relevant to the present invention are shown, omitting components such as buses, input / output interfaces, etc. In addition, the electronic device may include any other suitable components depending on the specific application.

[0130] Exemplary computer program products and computer-readable storage media

[0131] In addition to the methods and devices described above, embodiments of the present invention may also be computer program products, which include computer program instructions that, when executed by a processor, cause the processor to perform the steps of the methods for information mining of historical change records according to various embodiments of the present invention as described in the "Exemplary Methods" section of this specification.

[0132] The computer program product can be written in any combination of one or more programming languages ​​to perform the operations of the embodiments of the present invention. The programming languages ​​include object-oriented programming languages ​​such as Java and C++, as well as conventional procedural programming languages ​​such as C or similar languages. The program code can be executed entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server.

[0133] Furthermore, embodiments of the present invention may also be computer-readable storage media storing computer program instructions thereon, which, when executed by a processor, cause the processor to perform the steps of the methods for information mining of historical change records according to various embodiments of the present invention as described in the "Exemplary Methods" section above.

[0134] The computer-readable storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof.

[0135] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0136] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For system embodiments, since they largely correspond to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0137] The block diagrams of devices, systems, devices, and systems involved in this invention are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, systems, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0138] The methods and systems of the present invention may be implemented in many ways. For example, they may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order of steps for the methods is for illustrative purposes only, and the steps of the methods of the present invention are not limited to the order specifically described above unless otherwise specifically stated. Furthermore, in some embodiments, the present invention may also be implemented as a program recorded on a recording medium, the program comprising machine-readable instructions for implementing the methods according to the present invention. Thus, the present invention also covers recording media storing programs for performing the methods according to the present invention.

[0139] It should also be noted that in the systems, apparatus, and methods of the present invention, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered equivalents of the present invention. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the invention. Therefore, the invention is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0140] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the invention to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission, characterized in that, include: The voltage and current data of the three phases of the protection point are collected by phase, wherein the protection point is installed on the AC line from the flexible DC transmission system to the receiving end. Based on the voltage data and the current data, calculate the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero sequence current phasor for each of the three phases. Based on the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, the phase current phasor / phase-to-phase current phasor, and the zero sequence current phasor, calculate the phase-to-phase phase difference / phase-to-phase phase difference of the three phases at the protection point. Based on the phase difference / phase-to-phase difference, determine whether the distance protection at the protected location is activated; The operation of determining whether the distance protection at the protection point is activated based on the phase difference / interphase phase difference includes: Based on the protection action boundary, the preset margin value, and the phase difference / phase-to-phase difference, determine whether the distance protection at the protection point is activated; Based on the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor, the phase current phasor / phase-to-phase current phasor, and the zero-sequence current phasor, the formula for calculating the phase-to-phase phase difference of the three phases at the protection point is as follows: in, The positive-sequence phase voltage phasor. The phase current phasor. Let be the zero-sequence current phasor, where , K =( Z 0- Z 1) / 2 Z 1, among which, Z 0 Zero-sequence impedance, Z 1 It is a positive sequence impedance; The operation of determining whether the distance protection at the protection point is activated based on the protection action boundary, the preset margin value, and the phase difference includes: In satisfying Under the first determination condition, the distance protection at the protected location is activated, wherein, According to the phase difference, The boundary of the protection action, The margin value; If the first determination condition is not met, the distance protection at the protected location is turned off.

2. The method according to claim 1, characterized in that, Based on the positive-sequence phase voltage phasor / positive-sequence phase-to-phase voltage phasor and the phase current phasor / phase-to-phase current phasor, the calculation formula for the phase-to-phase phase difference of the three phases at the protection point is as follows: in, The positive-sequence interphase voltage phasor. Let be the interphase current phasor, where .

3. The method according to claim 2, characterized in that, The operation of determining whether the distance protection at the protection point is activated based on the protection action boundary, the preset margin value, and the phase difference between phases includes: In satisfying Under the second determination condition, the distance protection at the protected location is activated, wherein, To be based on the phase difference between phases, The boundary of the protection action, The margin value; If the second determination condition is not met, the distance protection at the protected location is turned off.

4. A device for determining the distance protection of the receiving-end AC line in a new energy transmission system via flexible direct transmission, used to implement the method described in claim 1, characterized in that, include: The acquisition module is used to acquire voltage and current data of the three phases at the protection point, wherein the protection point is installed on the AC line from the flexible DC transmission system to the receiving end. The first calculation module is used to calculate the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, phase current phasor / phase-to-phase current phasor, and zero sequence current phasor of the three phases respectively based on the voltage data and the current data. The second calculation module is used to calculate the phase difference / phase difference between the three phases at the protection point based on the positive sequence phase voltage phasor / positive sequence phase-to-phase voltage phasor, the phase current phasor / phase-to-phase current phasor and the zero sequence current phasor. The determination module is used to determine whether the distance protection at the protection point is activated based on the phase difference / phase-to-phase difference.

5. A computer-readable storage medium, characterized in that, The storage medium stores a computer program for performing the method described in any one of claims 1-3.

6. An electronic device, characterized in that, The electronic device includes: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method described in any one of claims 1-3.

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