A method and device for determining the action of a protection for a split address cascaded extra-high voltage direct current line

Abstract

The application discloses a kind of address cascade extra-high voltage direct current line protection action determination method and device.Therein, method includes: based on fault waveform, the fault component of line first end positive and negative voltage, current is calculated;Based on the fault component of line first end positive and negative voltage, current, the difference mode quantity, common mode quantity of fault voltage, current is calculated;Based on the difference mode quantity, common mode quantity of fault voltage, current, fault reverse traveling wave difference mode component and common mode component are calculated;Based on fault reverse traveling wave difference mode component and common mode component, traveling wave protection criterion is constructed, and voltage amplitude is based on voltage drop speed and voltage amplitude and forms voltage mutation variable protection criterion;Based on traveling wave protection criterion and voltage mutation variable protection criterion, the protection action of direct current line is determined.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, and more specifically, to a method and apparatus for determining the operation of a cascaded ultra-high voltage DC line protection system. Background Technology

[0002] Line commutated converter based high-voltage direct current (LCC-HVDC) transmission technology holds a significant position in long-distance power transmission due to its mature engineering technology, low cost, high withstand voltage, and large current capacity. However, traditional point-to-point LCC-HVDC systems struggle to adapt to the dispersed access needs of hydropower, wind power, and solar power resources, resulting in low transmission efficiency and high wind and solar curtailment rates. my country's renewable energy resources and load demand exhibit a clear inverse distribution pattern. Cascaded ultra-high-voltage direct current (UHVDC) transmission systems offer advantages such as integrating dispersed renewable energy access and improving system operational flexibility. They have become a key technology for the development of integrated hydropower, wind power, and solar power systems, and a core solution supporting cross-regional energy allocation and the construction of new power systems.

[0003] The location-cascaded ultra-high voltage direct current (UHVDC) transmission system involves the separate construction of high- and low-voltage converter stations at the sending end, utilizing cascaded DC lines to achieve coordinated power transmission from multiple energy bases. However, the unique cascaded structure at the sending end of the location-cascaded UHVDC transmission system presents significant challenges to existing relay protection technologies.

[0004] Existing DC transmission line protection is divided into single-ended quantity protection and double-ended quantity protection. Single-ended quantity protection uses only local electrical quantities for line fault identification, does not rely on communication between the two ends of the line, and has a relatively fast operating speed, often used as the main line protection. Fault traveling waves contain rich fault information, reflecting the fault location, transition resistance, etc. Some scholars have constructed standard fitting functions and generalized logistic functions to fit the ground mode fault current based on fault information analysis of the fault traveling wave front, forming single-ended quantity traveling wave protection. However, the attenuation and dispersion of the ground mode component during propagation along the line are severe, and it only exists in single-pole grounding faults, thus the reliability of this protection is poor. Furthermore, the above two protection methods require fitting algorithms, involving complex calculations and iterations, resulting in high algorithm complexity. Some scholars utilize the blocking effect of line boundaries on high-frequency current components, and construct protection based on wavelet transform to extract the high-frequency transient energy difference between faults inside and outside the fault zone. The setting of the protection criterion threshold value depends on simulation. Dual-end quantity protection for DC transmission lines uses electrical quantities at both ends of the line to distinguish faults inside and outside the DC line area. It has high selectivity and reliability, but the communication transmission delay at both ends of the line needs to be considered, resulting in lower protection speed. Some scholars use the time difference of the fault traveling wave arriving at each converter station for fault discrimination, which requires a high sampling frequency and fast communication and information synchronization between stations.

[0005] The multi-segment topology of cascaded UHVDC transmission lines in a cascaded, multi-site system complicates the traveling wave propagation path. The impedance-frequency characteristics differences caused by the separate locations of high- and low-end converters exacerbate traveling wave attenuation and distortion. Traditional polar wave / ground mode wave identification methods based on a single reflection and refraction law may struggle to accurately distinguish between faults inside and outside the transmission zone. Current HVDC line protection schemes face significant challenges in the application scenario of cascaded, multi-site UHVDC transmission systems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and apparatus for determining the action of protection systems in cascaded ultra-high voltage direct current lines with different addresses.

[0007] According to one aspect of the present invention, a method for determining the operation of cascaded ultra-high voltage direct current line protection is provided, comprising: Based on the fault waveform, calculate the fault components of the positive and negative voltage and current at the beginning of the line; Based on the fault components of the positive and negative voltage and current at the beginning of the line, calculate the differential modulus and common modulus of the fault voltage and current. Calculate the differential-mode and common-mode components of the fault reverse traveling wave based on the differential and common-mode quantities of fault voltage and current; Based on the differential-mode and common-mode components of the fault reverse traveling wave, a traveling wave protection criterion is constructed, and a voltage surge protection criterion is constructed based on the voltage drop rate and voltage amplitude. Based on the traveling wave protection criterion and the voltage surge protection criterion, the protection action of the DC line is determined.

[0008] Optionally, based on the fault waveform, the fault components of the positive and negative voltages and currents at the beginning of the line are calculated, including: The positive and negative voltages and currents at the beginning of the line are obtained based on the fault waveform. The fault components of the positive and negative voltages and currents at the beginning of the line are calculated based on the voltages and currents at the beginning of the line.

[0009] Optionally, the calculation expressions for the differential modulus and common modulus of the fault voltage and current are as follows: In the formula, U 1. U 0、 I 1. I 0 represents the differential-mode voltage and common-mode current, respectively. U p , U n , I p , I n These are positive and negative voltage fault components and current fault components.

[0010] Optionally, the calculation expressions for the differential-mode component and common-mode component of the fault-reverse traveling wave are as follows: In the formula, U b1 , U b0 These are the differential-mode component and the common-mode component of the reverse traveling wave, respectively. Z C1 , Z C0 These are the differential-mode impedance and the common-mode impedance, respectively, which are inherent parameters of the line.

[0011] Optionally, the expression for the traveling wave protection criterion is: In the formula, U b1set , U b0set These are the differential mode setpoint and the common mode setpoint, respectively. dU b0setAssign values ​​to common mode mutations.

[0012] Optionally, the expression for the voltage surge protection criterion is: In the formula, d U set , U setlow These are the voltage surge setpoint and the low voltage setpoint, respectively.

[0013] Optionally, the protection action of the DC line is determined based on the traveling wave protection criterion and the voltage surge protection criterion, including: If the fault waveform of the DC line meets the traveling wave protection criterion, the DC line is determined to be an intra-zone fault, and the traveling wave protection is activated. If the fault waveform of the DC line meets the voltage surge protection criterion, the DC line is determined to be an intra-zone fault, and the voltage surge protection is activated.

[0014] According to another aspect of the present invention, a device for determining the operation of a cascaded ultra-high voltage direct current line protection system is provided, comprising: The first calculation module is used to calculate the fault components of the positive and negative voltage and current at the beginning of the line based on the fault waveform. The second calculation module is used to calculate the differential modulus and common modulus of fault voltage and current based on the fault components of the positive and negative voltage and current at the beginning of the line. The third calculation module is used to calculate the differential mode component and common mode component of the fault reverse traveling wave based on the differential mode and common mode of the fault voltage and current. The module is used to construct traveling wave protection criteria based on the differential mode component and common mode component of the fault reverse traveling wave, and to construct voltage surge protection criteria based on voltage drop rate and voltage amplitude. The determination module is used to determine the protection action of the DC line based on the traveling wave protection criterion and the voltage surge protection criterion.

[0015] 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.

[0016] 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.

[0017] Therefore, this invention provides a method for evaluating the adaptability of protection for cascaded UHVDC lines. For cascaded UHVDC lines, it calculates characteristic quantities such as the differential mode, common mode component, and common mode mutation of the fault reverse traveling wave, clarifying the selectivity of DC line traveling wave protection and line voltage mutation protection in cascaded lines. This can provide some reference value for the configuration and setting of existing protection systems. Attached Figure Description

[0018] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 This is a flowchart illustrating a method for determining the action of a cascaded ultra-high voltage direct current line protection system according to an exemplary embodiment of the present invention. Figure 2 This is a topology diagram of an address-cascaded ultra-high voltage direct current transmission system provided by an exemplary embodiment of the present invention; Figures 3a-3d This is an exemplary embodiment of the present invention providing intra-regional high-resistivity faults and extra-regional faults. f 1. Fault traveling wave protection characteristic quantities: schematic diagram of line voltage, line differential mode voltage reverse traveling wave, line common mode voltage reverse traveling wave, and line common mode voltage reverse traveling wave abrupt change; Figure 4 This is an exemplary embodiment of the present invention providing a fault on L2 of an 800kV high-voltage DC line outside the designated area ( f 9) Schematic diagram of the traveling wave path; Figures 5a-5d This is an exemplary embodiment of the present invention providing a high-voltage DC line fault ( f 9) Fault at the end of the cascaded line ( f 3) Traveling wave protection characteristic quantities: schematic diagram of line voltage, line differential mode voltage reverse traveling wave, line common mode voltage reverse traveling wave, and line common mode voltage reverse traveling wave abrupt change; Figure 6a , Figure 6b This is an exemplary embodiment of the present invention providing intra-regional high-resistivity faults and extra-regional faults. f 1. Fault voltage surge protection characteristic: Line voltage, line voltage surge diagram; Figure 7a , Figure 7b This is an exemplary embodiment of the present invention providing a high-voltage DC line fault ( f 9) Fault at the end of the cascaded line ( f 3) Voltage Sudden Change Protection Characteristic Quantities: Line voltage, schematic diagram of line voltage sudden change; Figure 8 This is a schematic diagram of the structure of the address-cascaded ultra-high voltage DC line protection action determination device provided in an exemplary embodiment of the present invention; Figure 9This is the structure of an electronic device provided in an exemplary embodiment of the present invention. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Exemplary methods Figure 1 This is a schematic flowchart illustrating a method for determining the action of cascaded ultra-high voltage direct current line protection according to 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 action of cascaded UHVDC line protection includes the following steps: Step 101: Based on the fault waveform, calculate the fault components of the positive and negative voltage and current at the beginning of the line; Step 102: Based on the fault components of the positive and negative voltage and current at the beginning of the line, calculate the differential modulus and common modulus of the fault voltage and current. Step 103: Calculate the differential-mode component and common-mode component of the fault reverse traveling wave based on the differential mode and common mode of the fault voltage and current; Step 104: Based on the differential mode component and common mode component of the fault reverse traveling wave, construct the traveling wave protection criterion, and based on the voltage drop rate and voltage amplitude, construct the voltage change amount protection criterion. Step 105: Determine the protection action of the DC line based on the traveling wave protection criterion and the voltage surge protection criterion.

[0033] Specifically, this invention provides a method for evaluating the adaptability of protection for cascaded ultra-high voltage direct current (UHVDC) lines. For cascaded UHVDC transmission systems, it calculates characteristic quantities such as the differential mode, common mode component, and common mode mutation of the fault reverse traveling wave, analyzes and clarifies the selectivity of DC line traveling wave protection and voltage mutation protection in cascaded lines, and can provide some reference value for the configuration and setting of existing protection systems.

[0034] like Figure 2 The diagram shows a typical topology of a cascaded, distributed ultra-high voltage direct current (UHVDC) transmission system. This invention proposes a method for evaluating the protection adaptability of cascaded, distributed UHVDC lines, the method comprising the following steps: Step 1: Obtain the positive and negative voltages and currents at the beginning of the line based on the fault waveform, and calculate the fault components of the positive and negative voltages and currents of the line.

[0035] Step 2: Based on the fault components in Step 1, calculate the differential modulus and common modulus of the fault voltage and current using Equation (1).

[0036] (1) In the formula, U 1. U 0、 I 1. I 0 represents the differential-mode voltage and common-mode current, respectively. U p , U n , I p , I n These are positive and negative voltage fault components and current fault components.

[0037] Step 3: Based on the differential mode and common mode of Step 2, calculate the differential mode component and common mode component of the fault reverse traveling wave according to Equation (2).

[0038] (2) In the formula, U b1 , U b0 These are the differential-mode component and the common-mode component of the reverse traveling wave, respectively. Z C1 , Z C0These are the differential-mode impedance and the common-mode impedance, respectively, which are inherent parameters of the line.

[0039] Step 4: Construct the traveling wave protection criterion based on the differential mode component and common mode component of the above-mentioned fault reverse traveling wave, as shown in the following formula.

[0040] (3) In the formula, U b1set , U b0set These are the differential mode setpoint and the common mode setpoint, respectively. dU b0set Assign values ​​to common mode mutations.

[0041] Step 5: Construct a voltage surge protection criterion based on the voltage drop rate and voltage amplitude, as shown in the following formula.

[0042] (4) In the formula, d U set , U setlow These are the voltage surge setpoint and the low voltage setpoint, respectively.

[0043] Step 6: Perform protection discrimination based on the criteria formed by equations (3) and (4). If equation (3) is satisfied, it is judged as an intra-zone fault, and the traveling wave protection operates; if equation (4) is satisfied, it is judged as an intra-zone fault, and the voltage surge protection operates. Compare the degree of drop of differential-mode voltage reverse traveling wave and common-mode voltage reverse traveling wave after the fault in typical intra-zone and intra-zone fault scenarios, as well as the magnitude of the common-mode voltage reverse traveling wave surge, voltage change rate, and voltage amplitude, to determine the selectivity of DC line protection.

[0044] Specifically, the traveling wave protection criterion mainly relies on the attenuation effect of the line boundary on the high-frequency components of the fault traveling wave. The voltage change rate is significantly lower for faults outside the protection zone than for faults within the zone, thus enabling fault identification. However, for cascaded UHVDC lines with separate locations, the boundary elements configured on the line side are relatively weak (50mH smoothing reactor). Therefore, for protection at the line's starting point, the protection at the end of the protection zone... f 3. High resistance fault and outside the zone f 1. Traveling wave protection may not be able to reliably distinguish between faults.

[0045] Figures 3a-3d Draw the end points within the cascaded line area f 3. High-resistance grounding fault ( R f =300 ) and outside the area f 1 Fault ( R f =0 The simulation waveform diagram shows that the fault occurred...t =2s, sampling frequency is 20kHz. For example Figures 3a-3d As shown, outside the area f 1. During a fault, the voltage drop at the beginning of the line is more severe than during a fault within the zone. During a fault outside the zone, both the differential-mode voltage reverse traveling wave and the common-mode voltage reverse traveling wave drop more severely than during a fault within the zone. The sudden change in the common-mode voltage reverse traveling wave at the beginning of the line under both fault conditions is | dU b0 / dt| The timeouts are 221.1 kV / 0.2 ms and 152.7 kV / 0.2 ms respectively (within 2 ms after the fault). dU b0 / dt| The maximum value), that is, the change in the reverse traveling wave of the fault voltage outside the zone is greater than the change in the reverse traveling wave of the fault voltage inside the zone, causing the traveling wave protection to lose its selectivity.

[0046] For cascaded line protection, a fault on the 800kV high-voltage DC line L2 ( f 9) is an out-of-area fault. f The traveling wave generated by fault 9 will mainly travel directly to the cascaded line L1 via the DC filter and reach protection 1 (e.g., Figure 4 The smoothing reactor can be approximated as being bypassed and not on the traveling wave path. Therefore, for the first-end protection 1 of the DC cascaded line L1, in f The traveling wave generated by the fault at 9 o'clock arrives directly without passing through the smoothing reactor, making it difficult for the traveling wave protection to distinguish between faults within the line end zone and such faults outside the zone.

[0047] Figures 5a-5d Draw the fault at the beginning of an 800kV high-voltage direct current line ( f 9, R f =0 ) and end-of-line faults within the cascaded line area ( f 3, R f =100 The simulation waveform diagram. (For example...) Figures 5a-5d As shown, outside the area f 9. During a fault, the voltage drop at the beginning of the line is more severe than during a fault within the zone. During a fault outside the zone, both the differential-mode voltage reverse traveling wave and the common-mode voltage reverse traveling wave drop more severely than during a fault within the zone. The sudden change in the common-mode voltage reverse traveling wave at the beginning of the line under both fault conditions is | dU b0 / dt| The timeouts are 399.7 kV / 0.2 ms and 227.5 kV / 0.2 ms respectively (within 2 ms after the fault). dU b0 / dt|The maximum value), that is, the voltage reverse traveling wave change is greater when the fault occurs outside the zone than when the fault occurs inside the zone, causing the traveling wave protection to lose its selectivity.

[0048] Similar to traveling wave protection, the effectiveness of voltage surge protection is also affected by line boundary elements. For cascaded lines, weak line boundaries can lead to problems at the end of the protection zone. f 3. High resistance fault and outside the zone f 1. The protection may not be able to reliably distinguish between faults.

[0049] Figures 6a-6b Draw the end points within the cascaded line area f 3 High-resistance faults ( R f =300 ) and outside the area f 1 Fault ( R f =0 The simulation waveform diagram is shown below. Figures 6a-6b As shown, outside the area f The voltage drop at the beginning of the line during a fault is more severe than during a fault within the zone. The voltage change in the line under both fault conditions is | dU / dt| The timeouts are 334.9 kV / 0.2 ms and 248.3 kV / 0.2 ms respectively (within 2 ms after the fault). dU / dt| The maximum value), that is, the voltage change is greater when the fault is outside the zone than when the fault is inside the zone, causing the voltage change protection to lose its selectivity.

[0050] For cascaded line voltage surge protection, a fault on the 800kV high-voltage DC line L2 ( f 9) is an out-of-area fault. f The traveling wave generated by fault 9 will mainly travel directly to the cascaded line L1 via the DC filter and reach protection 1. The smoothing reactor can be approximated as being bypassed, so the voltage surge protection has difficulty distinguishing between faults within the line end zone and such external faults.

[0051] Figures 7a-7b Draw the fault at the beginning of an 800kV high-voltage direct current line ( f 9, R f =0 ) and cascaded line end faults ( f 3, R f =100 The simulation waveform diagram. (For example...) Figures 7a-7b As shown, outside the area f9. During a fault, the voltage drop at the beginning of the line is more severe than during a fault within the zone. The voltage change in the line under both fault conditions is | dU / dt| The timeouts are 574.7 kV / 0.2 ms and 355.3 kV / 0.2 ms respectively (within 2 ms after the fault). dU / dt| The maximum value), that is, the voltage change is greater when the fault occurs outside the zone than when the fault occurs inside the zone, and the voltage change protection loses its selectivity.

[0052] In a specific embodiment of the present invention, based on the PSCAD simulation platform, and taking a real-world engineering project as an example, an electromagnetic transient model of a cascaded UHVDC transmission system was built. The fault points were set as follows: Figure 1 As shown, the distributed construction at the sending end enables complementary transmission of new energy sources, with a rated transmission capacity of 8000MW and a DC voltage level of ±800kV, solving the problem of limited capacity of a single converter station. For the distributed cascaded UHVDC transmission system, voltage balance control is added to the high-voltage valve group to achieve active control of the DC voltage of the high- and low-end valve groups.

[0053] For cascaded UHVDC lines with separate addresses, the characteristic quantities such as the differential mode, common mode component, and common mode mutation of the reverse traveling wave during faults were calculated. The analysis clarified that the traveling wave protection and line voltage mutation protection of DC lines may lose selectivity when there is a fault f3 at the end of the line and faults f1 and f9 outside the zone. The simulation verified the correctness of the above theoretical derivation.

[0054] Therefore, this invention provides a method for evaluating the adaptability of protection for cascaded ultra-high voltage direct current (UHVDC) lines. In cascaded UHVDC transmission systems, high-voltage and low-voltage stations are connected via cascaded lines. The electromagnetic interaction between converters of different voltage levels will produce fault characteristics distinct from traditional DC transmission, making the applicability of protection unclear. To address this, this invention calculates characteristic quantities such as the differential mode, common mode component, and common mode abrupt change of the fault reverse traveling wave, clarifying the selectivity of DC line traveling wave protection and line voltage abrupt change protection in cascaded lines. This can provide valuable reference for the configuration and setting of existing protection systems.

[0055] Exemplary device Figure 8 This is a schematic diagram of the structure of a cascaded ultra-high voltage direct current line protection action determination device provided in an exemplary embodiment of the present invention. Figure 8 As shown, the device 800 includes: The first calculation module 810 is used to calculate the fault components of the positive and negative voltage and current at the beginning of the line based on the fault waveform. The second calculation module 820 is used to calculate the differential modulus and common modulus of fault voltage and current based on the fault components of the positive and negative voltage and current at the beginning of the line. The third calculation module 830 is used to calculate the differential mode component and common mode component of the fault reverse traveling wave based on the differential mode and common mode of the fault voltage and current. Module 840 is used to construct traveling wave protection criteria based on the differential mode component and common mode component of the fault reverse traveling wave, and to construct voltage surge protection criteria based on voltage drop rate and voltage amplitude. The determination module 850 is used to determine the protection action of the DC line based on the traveling wave protection criterion and the voltage surge protection criterion.

[0056] Optionally, the first computing module 810 includes: The positive and negative voltages and currents at the beginning of the line are obtained based on the fault waveform. The fault components of the positive and negative voltages and currents at the beginning of the line are calculated based on the voltages and currents at the beginning of the line.

[0057] Optionally, the calculation expressions for the differential modulus and common modulus of the fault voltage and current are as follows: In the formula, U 1. U 0、 I 1. I 0 represents the differential-mode voltage and common-mode current, respectively. U p , U n , I p , I n These are positive and negative voltage fault components and current fault components.

[0058] Optionally, the calculation expressions for the differential-mode component and common-mode component of the fault-reverse traveling wave are as follows: In the formula, U b1 , U b0 These are the differential-mode component and the common-mode component of the reverse traveling wave, respectively. Z C1 , Z C0 These are the differential-mode impedance and the common-mode impedance, respectively, which are inherent parameters of the line.

[0059] Optionally, the expression for the traveling wave protection criterion is: In the formula, U b1set , U b0set These are the differential mode setpoint and the common mode setpoint, respectively. dU b0set Assign values ​​to common mode mutations.

[0060] Optionally, the expression for the voltage surge protection criterion is: In the formula, d U set , U setlow These are the voltage surge setpoint and the low voltage setpoint, respectively.

[0061] Optionally, module 850 is defined, including: If the fault waveform of the DC line meets the traveling wave protection criterion, the DC line is determined to be an intra-zone fault, and the traveling wave protection is activated. If the fault waveform of the DC line meets the voltage surge protection criterion, the DC line is determined to be an intra-zone fault, and the voltage surge protection is activated.

[0062] Exemplary electronic devices Figure 9 This is the structure of an electronic device provided in an exemplary embodiment of the present invention. For example... Figure 9 As shown, the electronic device 90 includes one or more processors 91 and memory 92.

[0063] The processor 91 may be a central processing unit (CPU) or other form of processing unit with data processing and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions.

[0064] The memory 92 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 91 may execute the program instructions to implement the methods of the software programs of the various embodiments of the present invention described above, and / or other desired functions. In one example, the electronic device may also include an input device 93 and an output device 94, these components being interconnected via a bus system and / or other forms of connection mechanisms (not shown).

[0065] In addition, the input device 93 may also include, for example, a keyboard, a mouse, etc.

[0066] The output device 94 can output various information to the outside. The output device 94 may include, for example, a display, a speaker, a printer, and a communication network and its connected remote output devices, etc.

[0067] Of course, for the sake of simplicity, Figure 9 Only some of the components of this 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.

[0068] Exemplary computer program products and computer-readable storage media In addition to the methods and apparatus 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 in the methods according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0069] 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.

[0070] 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 according to various embodiments of the present invention described in the "Exemplary Methods" section above.

[0071] 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, system, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) 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 devices, magnetic storage devices, or any suitable combination thereof.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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 thereof.

Claims

1. A method for determining the action of cascaded ultra-high voltage direct current line protection, characterized in that, include: Based on the fault waveform, calculate the fault components of the positive and negative voltage and current at the beginning of the line; Based on the fault components of the positive and negative voltage and current at the beginning of the line, calculate the differential modulus and common modulus of the fault voltage and current. The differential-mode component and common-mode component of the fault reverse traveling wave are calculated based on the differential-mode and common-mode components of the fault voltage and current. Based on the differential-mode and common-mode components of the fault reverse traveling wave, a traveling wave protection criterion is constructed, and a voltage surge protection criterion is constructed based on the voltage drop rate and voltage amplitude. Based on the traveling wave protection criterion and the voltage surge protection criterion, the protection action of the DC line is determined.

2. The method according to claim 1, characterized in that, Based on the fault waveform, calculate the fault components of the positive and negative voltages and currents at the beginning of the line, including: The positive and negative voltages and currents at the beginning of the line are obtained based on the fault waveform. The fault components of the positive and negative voltages and currents at the beginning of the line are calculated based on the voltages and currents at the beginning of the line.

3. The method according to claim 1, characterized in that, The calculation expressions for the differential modulus and common modulus of the fault voltage and current are as follows: In the formula, U 1. U 0、 I 1. I 0 represents the differential-mode voltage and common-mode current, respectively. U p , U n , I p , I n These are positive and negative voltage fault components and current fault components.

4. The method according to claim 3, characterized in that, The calculation expressions for the differential-mode component and common-mode component of the fault reverse traveling wave are as follows: In the formula, U b1 , U b0 These are the differential-mode component and the common-mode component of the reverse traveling wave, respectively. Z C1 , Z C0 These are the differential-mode impedance and the common-mode impedance, respectively, which are inherent parameters of the line.

5. The method according to claim 4, characterized in that, The expression for the traveling wave protection criterion is: In the formula, U b1set , U b0set These are the differential mode setpoint and the common mode setpoint, respectively. dU b0set Assign values ​​to common mode mutations.

6. The method according to claim 1, characterized in that, The expression for the voltage surge protection criterion is: In the formula, d U set , U setlow These are the voltage surge setpoint and the low voltage setpoint, respectively.

7. The method according to claim 1, characterized in that, Based on the traveling wave protection criterion and the voltage surge protection criterion, the protection action of the DC line is determined, including: If the fault waveform of the DC line meets the traveling wave protection criterion, then the DC line is determined to be an intra-zone fault, and the traveling wave protection action is initiated. If the fault waveform of the DC line meets the voltage surge protection criterion, then the DC line is determined to be an intra-zone fault, and the voltage surge protection action is initiated.

8. A device for determining the action of a cascaded ultra-high voltage direct current line protection system, characterized in that, include: The first calculation module is used to calculate the fault components of the positive and negative voltage and current at the beginning of the line based on the fault waveform. The second calculation module is used to calculate the differential modulus and common modulus of fault voltage and current based on the fault components of the positive and negative voltage and current at the beginning of the line. The third calculation module is used to calculate the differential mode component and common mode component of the fault reverse traveling wave based on the differential mode and common mode of the fault voltage and current. The module is used to construct a traveling wave protection criterion based on the differential mode component and common mode component of the fault reverse traveling wave, and to construct a voltage surge protection criterion based on the voltage drop rate and voltage amplitude. The determination module is used to determine the protection action of the DC line based on the traveling wave protection criterion and the voltage surge protection criterion.

9. The apparatus according to claim 8, characterized in that, The first calculation module includes: The positive and negative voltages and currents at the beginning of the line are obtained based on the fault waveform. The fault components of the positive and negative voltages and currents at the beginning of the line are calculated based on the voltages and currents at the beginning of the line.

10. The apparatus according to claim 8, characterized in that, The calculation expressions for the differential modulus and common modulus of the fault voltage and current are as follows: In the formula, U 1. U 0、 I 1. I 0 represents the differential-mode voltage and common-mode current, respectively. U p , U n , I p , I n These are positive and negative voltage fault components and current fault components.

11. The apparatus according to claim 10, characterized in that, The calculation expressions for the differential-mode component and common-mode component of the fault reverse traveling wave are as follows: In the formula, U b1 , U b0 These are the differential-mode component and the common-mode component of the reverse traveling wave, respectively. Z C1 , Z C0 These are the differential-mode impedance and the common-mode impedance, respectively, which are inherent parameters of the line.

12. The apparatus according to claim 11, characterized in that, The expression for the traveling wave protection criterion is: In the formula, U b1set , U b0set These are the differential mode setpoint and the common mode setpoint, respectively. dU b0set Assign values ​​to common mode mutations.

13. The apparatus according to claim 8, characterized in that, The expression for the voltage surge protection criterion is: In the formula, d U set , U setlow These are the voltage surge setpoint and the low voltage setpoint, respectively.

14. The apparatus according to claim 8, characterized in that, The module to be determined includes: If the fault waveform of the DC line meets the traveling wave protection criterion, then the DC line is determined to be an intra-zone fault, and the traveling wave protection action is initiated. If the fault waveform of the DC line meets the voltage surge protection criterion, then the DC line is determined to be an intra-zone fault, and the voltage surge protection action is initiated.

15. 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 1-7.

16. 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 1-7.

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