Distributed power supply intertripping method and system for fault section of alternating-current power distribution network

Abstract

The invention discloses an alternating-current power distribution network fault section distributed power supply intertripping method and system, and the method comprises the steps: starting protection when a fault phase power frequency voltage sampling point meets a set condition, and judging that a fault occurs; the amplitude relation between the opposite-end power frequency fault current and the direction criterion threshold value is calculated, and the opposite-end power frequency fault current is used for judging the fault direction; a preset frequency characteristic signal is injected through a converter control loop, and an active boundary is constructed to identify a fault direction; adopting a matrix pencil algorithm to extract a characteristic signal as a protection criterion input; and determining a fault section and triggering intertripping based on the amplitude of the characteristic signal and the local electrical quantity. According to the invention, the active boundary is constructed by using the current converter, the distributed power supply intertripping is realized during the protection action of the home terminal, the protection sensitivity and reliability are easy to improve, and the protection has the whole-line quick-action capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system relay protection, and in particular relates to a method and system for co-switching distributed power sources in a fault section of an AC power distribution network. Background Art

[0002] As the penetration rate of distributed power generation (DGs) in distribution networks increases significantly, the high proportion of access is exacerbating the shortcomings of traditional distribution network fault handling mechanisms. Traditional anti-islanding protection devices are subject to the 2-second action time limit required by the "Technical Regulations for the Integration of Photovoltaic Power Stations into Power Systems." This delay design is primarily based on two considerations: 1. Confirmation of islanding status requires continuous monitoring of voltage / frequency offset to avoid malfunction caused by transient disturbances; 2. Protective devices must coordinate with the reclosing sequence of upstream circuit breakers. However, this delay can prevent the arc at the fault point from being extinguished quickly. Statistics show that approximately 35% of permanent faults in power grids are caused by arc reignition. Furthermore, delayed operation can cause disordered disconnection of distributed generation (DGs), reducing the reclosing success rate by 40%-60%.

[0003] The bidirectional power supply characteristics of distributed generation (DGs) alter the fault current distribution pattern: the influx of multiple sources reduces the fault current amplitude by 20%-50%, and the fault current phase shift can reach 15°-30°. This significantly degrades the sensitivity and selectivity of traditional power-frequency protection criteria. Simulations show that in distribution networks with DG penetration exceeding 30%, the false tripping rate of overcurrent protection can exceed 25%.

[0004] The fault current output capability of distributed power supplies with power electronic interfaces is limited, with their maximum short-circuit current typically not exceeding 1.2-2 times the rated current. Traditional overcurrent protection settings, however, must avoid the maximum load current (typically 1.5-2 times the rated value), resulting in a drop in protection sensitivity of over 60%, potentially leading to failure to operate in the event of a ground fault across a transition resistor.

[0005] The multi-terminal power supply network changes the unidirectional fault current path of the traditional radial power grid, making it difficult to coordinate the timing of upstream and downstream protection actions. The step time is reduced to 0.1-0.2s, and an intersection appears in the inverse time characteristic curve, resulting in a 35% increase in the risk of protection over-step action.

[0006] In view of this, if the distributed power supply in the fault section can be disconnected, the impact of the distributed power supply on reclosing and feeder automation can be avoided. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to address the deficiencies in the above-mentioned prior art and provide a method and system for co-cutting distributed power sources in a fault section of an AC distribution network, so as to solve the technical problems of fault arc extinction delay and high reclosing failure rate caused by the delay in the action of traditional anti-islanding protection, as well as insufficient protection sensitivity and selectivity in high-penetration distributed power supply scenarios.

[0008] The present invention adopts the following technical solutions: A method for disconnecting distributed power sources in a faulty section of an AC power distribution network comprises the following steps: When the power frequency voltage sampling point of the fault phase meets the set conditions, the protection is activated and it is determined that a fault has occurred; Calculate the amplitude relationship between the opposite-end power frequency fault current and the direction judgment threshold, and use the opposite-end power frequency fault current to determine the fault direction; A preset frequency characteristic signal is injected through the converter control loop to construct an active boundary to identify the fault direction; Matrix bundle algorithm is used to extract characteristic signals as protection criterion input; Based on the amplitude of the characteristic signal and local electrical quantities, the fault section is determined and the joint disconnection is triggered.

[0009] Preferably, the protection mechanism is activated when the sampling data is greater than the activation criterion for three consecutive times.

[0010] Preferably, the start criteria are as follows:

[0011] in, The first phase voltage of the power frequency fault k The absolute value of the sampling points; The power frequency phase voltage in normal operation kN S The absolute value of the sampling points; N S is the number of sampling points in a sampling period; is the starting criterion threshold.

[0012] Preferably, when the direction criterion threshold I set =1.2 I DGmax When the protection is started, the directional element starts calculating at the first sampling point that meets the start criterion. When , it is judged as a forward fault; otherwise, it is a reverse fault. I DGmax The maximum short-circuit current provided to downstream distributed generation.

[0013] Preferably, when the peer end is judged to be a forward fault, the active boundary injects a preset characteristic frequency representing the forward fault of the peer end. f1 signal; on the contrary, when it is judged as a reverse fault, the active boundary injects the preset characteristic frequency representing the reverse fault of the opposite end f 2 signals.

[0014] Preferably, the characteristic signal voltage command injected into the active boundary is:

[0015] in, is the voltage command amplitude, is the frequency of the voltage command, Initial phase of voltage command.

[0016] Preferably, a matrix bundle algorithm is used to extract characteristic signals. By constructing a Hankel matrix, determining the system order through singular value decomposition, constructing a D matrix, and extracting characteristic parameters, the amplitude and phase angle of the corresponding signal frequency are obtained as follows:

[0017]

[0018] in, A i 、 θ i are the amplitude and initial phase angle of the characteristic signal respectively, R i is the complex amplitude.

[0019] Preferably, if both the local protection and the distributed power supply side meet the criteria, it is determined to be an intra-zone fault and the distributed power supply in the faulty section is disconnected; if any of the criteria is not met, it is determined to be an extra-zone fault and the protection action is locked.

[0020] Preferably, the full-line quick-acting protection criterion of the protection end is set as follows:

[0021] The protection criteria for distributed power supply in the fault section are set as follows:

[0022] in, I k is the fundamental frequency current on the protection side of this end, I L.max It is the maximum load current when the line is operating normally. U aω1 、 U bω1 、U cω1 The frequencies representing the forward faults of the three phases of the protection end extracted by the matrix bundle algorithm are f 1 specific response voltage signal,U aω2 、 U bω2 、U cω2 The frequency of the reverse fault characterizing the three-phase protection end is f 2 voltage signal, U set is the setting value of protection; k is the reliability factor of protection, U DG is the fundamental frequency voltage on the distributed power supply side of the fault section, U E It is the fundamental frequency rated voltage of the distributed power supply side in the fault section.

[0023] In a second aspect, an embodiment of the present invention provides a system for co-switching distributed power sources in a fault section of an AC distribution network, comprising: The startup module starts the protection when the power frequency voltage sampling point of the fault phase meets the set conditions and determines that a fault has occurred; The discrimination module calculates the amplitude relationship between the opposite-end power frequency fault current and the direction judgment threshold, and uses the opposite-end power frequency fault current to discriminate the fault direction; The injection module injects a preset frequency characteristic signal through the converter control loop to construct an active boundary to identify the fault direction; Input module, which uses matrix bundle algorithm to extract characteristic signals as protection criterion input; The output module determines the fault section and triggers joint switching based on the amplitude of the characteristic signal and local electrical quantities.

[0024] In a third aspect, a computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for disconnecting distributed power sources in a fault section of an AC distribution network when executing the computer program.

[0025] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, comprising a computer program, which, when executed by a processor, implements the steps of the above-mentioned method for disconnecting distributed power sources in a fault section of an AC distribution network.

[0026] In a fifth aspect, a chip comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the above-mentioned method for disconnecting distributed power sources in a faulty section of an AC distribution network are implemented.

[0027] In a sixth aspect, an embodiment of the present invention provides an electronic device, comprising a computer program, which, when executed by the electronic device, implements the steps of the above-mentioned method for disconnecting distributed power sources in a fault section of an AC distribution network.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects: A distributed generation (DG) co-tripping method for faulty sections of AC distribution networks utilizes power frequency voltage difference mutations for fault detection, circumventing the problem of traditional overcurrent protection being affected by DG output fluctuations. A directional criterion based on the comparison of opposite-end short-circuit current thresholds addresses the problem of ambiguity in fault current direction caused by multiple power feeds. A matrix bundle algorithm uses Hankel matrix singular value decomposition to extract features before transient signals decay, addressing the difficulty in capturing features due to the rapid decay of high-frequency components. By constructing a complete logical chain of "fault detection - direction determination - active boundary - feature extraction - co-tripping criterion", a closed-loop protection action process is achieved.

[0029] Furthermore, a moving time window is used for continuous monitoring, and the window length can capture voltage mutations and filter out transient interference such as lightning strikes.

[0030] Furthermore, a 1.2-fold factor achieves the best balance between sensitivity and selectivity.

[0031] Furthermore, 125Hz is located between the 3rd harmonic (150Hz) and the 5th harmonic (250Hz), avoiding the main harmonic interference area; 175Hz is the half-frequency point of the 7th harmonic (350Hz), avoiding integer frequency interference; the signal amplitude is controlled at 5%-10% of the rated voltage, which not only ensures signal strength but also does not affect the converter's fault ride-through capability.

[0032] Furthermore, the Hankel matrix dimension N×(L-N+1) is optimized to N=20 and L=100, which reduces the amount of calculation while ensuring a frequency resolution of 0.1 Hz; the singular value decomposition is used to screen the first three principal components to effectively suppress random noise.

[0033] Furthermore, criterion 1 ensures that load fluctuations are not misjudged, and the measured load current fluctuation range is controlled within ±15%; criterion 2 covers the low voltage ride-through threshold of distributed power sources; the reliability coefficient is determined through Monte Carlo simulation optimization, balancing the protection margin and action speed; the local current and characteristic signal dual criteria are jointly verified, and the fault identification accuracy within the area is increased to 98.7%.

[0034] It can be understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0035] In summary, the method of the present invention utilizes the converter to construct an active boundary to realize the distributed power supply switching when the local protection is actuated, which not only facilitates the improvement of protection sensitivity and reliability, but also enables the protection to have full-line fast action capability.

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] Figure 1 Control strategy for active boundaries; Figure 2 Flowchart of the present invention; Figure 3 This is the distribution network model diagram with the converter system; Figure 4 shows the fault characteristic diagram of protection 1 and 3 under intra-zone fault, where (a) is the specific response feature extracted by the matrix bundle algorithm at measurement point 1, (b) is the voltage amplitude-frequency characteristic, and (c) is the specific response feature extracted by the matrix bundle algorithm at measurement point 3. Figure 5 shows the fault characteristic diagram of protection 1 and 3 under out-of-zone fault, where (a) is the specific response feature extracted by the matrix bundle algorithm at measurement point 1, (b) is the voltage amplitude-frequency characteristic, and (c) is the specific response feature extracted by the matrix bundle algorithm at measurement point 3. Figure 6 A schematic diagram of a computer device provided in accordance with an embodiment of the present invention; Figure 7 The present invention is a block diagram of an electronic device according to an embodiment of the present invention.

[0039] Among them, 60. Computer device; 61. Processor; 62. Memory; 63. Computer program; 600. Electronic device; 610. Processing unit; 620. Storage unit; 6201. Random access memory unit; 6202. Cache memory unit; 6203. Read-only memory unit; 6204. Program / Utility; 6205. Program module; 630. Bus; 640. Display unit; 650. Input / output interface; 660. Network adapter; 700. External device. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] In the description of the present invention, it is to be understood that the terms “include” and “comprise” indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0042] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0043] It should be further understood that the term "and / or" as used in the present specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0044] It should be understood that although the terms "first," "second," and "third" may be used to describe preset ranges in embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0045] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0046] The accompanying drawings illustrate various schematic diagrams of structures according to embodiments disclosed herein. These figures are not drawn to scale; for clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0047] The present invention provides a method for co-tripping distributed power sources in a fault section of an AC distribution network. The method utilizes a converter to generate preset deterministic response signals for different disturbances to construct an active boundary, and forms a definite coordination relationship with single-ended protection. When the protection is actuated, the distributed power sources are co-tripped, realizing single-ended full-line fast-acting protection, and effectively improving the speed and reliability of relay protection in new power systems.

[0048] Example 1 The present invention provides a method for disconnecting distributed power sources in a fault section of an AC power distribution network, comprising the following steps: S1. After the fault occurs, the fault phase voltage drops rapidly, which is quite different from the normal operation state. The starting criterion is shown in formula (1): (1) in, The first phase voltage of the power frequency fault k The absolute value of the sampling points; The power frequency phase voltage in normal operation kN S The absolute value of the sampling points; N S is the number of sampling points in a sampling period; The threshold value for starting judgment is set according to the voltage fluctuation during normal operation and a certain margin is reserved. =0.2pu.

[0049] To ensure the reliability of the starting conditions, the protection mechanism is activated when the sampling data is greater than the trigger threshold for three consecutive times.

[0050] S2. Use the opposite-end power frequency fault current to determine the fault direction; Assuming that the positive direction of the AC line current is from the busbar to the line, for the opposite system, it is the distributed power supply outgoing line flowing toward the AC grid side. The direction criterion based on the opposite power frequency fault current is shown in Equation (2).

[0051] (2) in, is the opposite-end power frequency fault phase current; I set The threshold value of direction judgment is taken into account, the sampling error in the sampling process is considered, and the maximum short-circuit current provided by the distributed power supply in the downstream is set. I set =1.2 I DGmax , I DGmaxThe maximum short-circuit current provided to the downstream distributed generation. After the protection is activated, the directional element begins calculation at the first sampling point that meets the startup criteria. If it meets the criteria, it is judged as a forward fault; otherwise, it is judged as a reverse fault.

[0052] S3. When the converter is performing fault ride-through, the active boundary construction control strategy is carried out synchronously. The active boundary is indirectly constructed by implanting the preset response characteristic signal. When the opposite end is judged as a forward fault, the active boundary injects the preset characteristic frequency representing the opposite end forward fault. f 1 signal; on the contrary, when it is judged as a reverse fault, the active boundary injects the preset characteristic frequency representing the reverse fault of the opposite end f 2 signal, the injection link of the detection signal is as follows Figure 1 shown.

[0053] The characteristic signal voltage command injected into the active boundary is: (3) in, is the voltage command amplitude, is the frequency of the voltage command, Initial phase of voltage command.

[0054] S4, extracting characteristic signals; During the fault occurrence and current limiting control and boundary signal injection control phases, the transient fault current contains a large number of harmonic and periodic components, and these components exhibit attenuation characteristics. To reduce the algorithm's sensitivity to noise and improve computational efficiency, a matrix bundle algorithm is used to extract characteristic signals.

[0055] The signal model is expressed as: (4) in, M Represents the order of the signal model; for the i-th signal component, R i represents the complex amplitude, A i represents the amplitude of the signal, θ i Represents the initial phase of the signal; s i represents the complex frequency, that is , α i represents the attenuation factor, ω i Represents the phase angle frequency; the matrix bundle algorithm constructs the Hankel matrix, determines the system order through singular value decomposition, constructs the D matrix and extracts the characteristic parameters. Finally, the amplitude and phase angle of the corresponding signal frequency are obtained by equations (5)-(7).

[0056] (5) (6) (7) in, A i 、 θ i are the amplitude and initial phase angle of the characteristic signal respectively.

[0057] S5. Criteria for local protection and distributed power supply side protection.

[0058] The criterion for the full-line quick-acting protection at the protection end is set as follows: (8) in, I k is the fundamental frequency current on the protection side of this end, I L.max It is the maximum load current when the line is operating normally. U aω1 、 U bω1 、U cω1 The frequencies representing the forward faults of the three phases of the protection end extracted by the matrix bundle algorithm are f 1 specific response voltage signal, U aω2 、 U bω2 、U cω2 The frequency of the reverse fault characterizing the three-phase protection end is f 2 voltage signal, U set is the setting value of protection; k It is the reliability coefficient of protection, generally taken as 0.8~0.9.

[0059] The protection criteria for distributed power supply in the fault section are set as follows: (9) in, U DG is the fundamental frequency voltage on the distributed power supply side of the fault section, U E It is the fundamental frequency rated voltage of the distributed power supply side in the fault section.

[0060] If the protection terminal determines that a forward fault has occurred on the line, the fundamental frequency voltage on the distributed power supply side of the fault section is lower than the set value, and the frequency is f 1, which indicates a forward fault, has three-phase response voltage signals exceeding the set value, and the frequency is fIf the three-phase response voltage signals of the reverse fault are all less than the set value, it is judged as an internal fault, the protection terminal is activated, and the distributed power supply in the fault section is also activated. Otherwise, it is an external fault, the protection terminal does not operate, and the distributed power supply in the fault section does not operate.

[0061] At this point, the distributed power supply in the fault section is switched off.

[0062] Those skilled in the art will appreciate that various aspects of the present invention may be implemented as systems, methods, or program products. Accordingly, various aspects of the present invention may be implemented in the following forms: entirely in hardware, entirely in software (including firmware, microcode, etc.), or in a combination of hardware and software, collectively referred to herein as "circuits," "modules," or "platforms."

[0063] Example 2 The present invention provides a distributed power supply inter-cutting system for a faulty section of an AC distribution network. The system can be used to implement the above-mentioned distributed power supply inter-cutting method for a faulty section of an AC distribution network. Specifically, the distributed power supply inter-cutting system for a faulty section of an AC distribution network includes a starting module, a discrimination module, an injection module, an input module, and an output module.

[0064] Among them, the starting module starts protection when the power frequency voltage sampling point of the fault phase meets the set conditions and determines that a fault has occurred; The discrimination module calculates the amplitude relationship between the opposite-end power frequency fault current and the direction judgment threshold, and uses the opposite-end power frequency fault current to discriminate the fault direction; The injection module injects a preset frequency characteristic signal through the converter control loop to construct an active boundary to identify the fault direction; Input module, which uses matrix bundle algorithm to extract characteristic signals as protection criterion input; The output module determines the fault section and triggers joint switching based on the amplitude of the characteristic signal and local electrical quantities.

[0065] Example 3 The present invention provides a terminal device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, graphics processing units (GPUs), tensor processing units (TPUs), digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to implement corresponding method processes or corresponding functions; the processor described in the embodiment of the present invention can be used for the operation of a method for disconnecting distributed power sources in a fault section of an AC distribution network, including: When the power-frequency voltage sampling point of the fault phase meets the set conditions, protection is activated and a fault is determined to have occurred. The amplitude relationship between the opposite-end power-frequency fault current and the direction judgment threshold is calculated, and the opposite-end power-frequency fault current is used to determine the fault direction. A preset frequency characteristic signal is injected through the converter control loop to construct an active boundary to identify the fault direction. A matrix bundle algorithm is used to extract the characteristic signal as the protection judgment input. Based on the amplitude of the characteristic signal and local electrical quantities, the fault section is determined and the interlocking trip is triggered.

[0066] See also Figure 6 The terminal device is a computer device. The computer device 60 of this embodiment includes: a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable by the processor 61. When executed by the processor 61, the computer program 63 implements the AC distribution network fault section distributed power generation inter-cutting method of the embodiment. To avoid repetition, the details are not described here. Alternatively, when executed by the processor 61, the computer program 63 implements the functions of each model / unit in the AC distribution network fault section distributed power generation inter-cutting system of the embodiment. To avoid repetition, the details are not described here.

[0067] The computer device 60 may be a desktop computer, a notebook computer, a PDA, a cloud server, or other computing devices. The computer device 60 may include, but is not limited to, a processor 61 and a memory 62. It will be understood by those skilled in the art that Figure 6This is merely an example of the computer device 60 and does not constitute a limitation of the computer device 60 . The computer device 60 may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the computer device may also include input and output devices, network access devices, buses, etc.

[0068] The processor 61 may be a central processing unit (CPU), or other general-purpose processors, a graphics processing unit (GPU), a tensor processing unit (TPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0069] The memory 62 may be an internal storage unit of the computer device 60, such as a hard disk or memory of the computer device 60. The memory 62 may also be an external storage device of the computer device 60, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the computer device 60.

[0070] Furthermore, the memory 62 may include both an internal storage unit of the computer device 60 and an external storage device. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 may also be used to temporarily store data that has been output or is about to be output.

[0071] See also Figure 7 The terminal device is an electronic device 600, which is implemented as a general-purpose computing device. The components of the electronic device may include, but are not limited to, at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different platform components (including the storage unit 620 and the processing unit 610), and a display unit 640.

[0072] The storage unit stores program codes, which can be executed by the processing unit 610, so that the processing unit 610 performs the steps according to various exemplary embodiments of the present invention described in the above method section of this specification. For example, the processing unit 610 can perform the following steps: Figure 2 Follow the steps shown in .

[0073] The storage unit 620 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 6201 and / or a cache memory unit 6202 , and may further include a read-only memory unit (ROM) 6203 .

[0074] The storage unit 620 may also include a program / utility 6204 having a set (at least one) of program modules 6205, such program modules 6205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment.

[0075] Bus 630 may represent one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

[0076] The electronic device 600 may also communicate with one or more external devices 700 (e.g., a keyboard, a pointing device, a Bluetooth device, etc.), one or more devices that enable a user to interact with the electronic device 600, and / or any device that enables the electronic device 600 to communicate with one or more other computing devices (e.g., a router, a modem). Such communication may occur via an input / output interface 650. Furthermore, the electronic device 600 may also communicate with one or more networks (e.g., a local area network, a wide area network, and / or a public network, such as the Internet) via a network adapter 660. The network adapter 660 may communicate with other modules of the electronic device 600 via a bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules may be used in conjunction with the electronic device 600, including but not limited to microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage platforms.

[0077] Example 4 The present invention also provides a storage medium, specifically a computer-readable storage medium. The computer-readable storage medium is a memory device in a terminal device, used to store programs and data. It is understood that the computer-readable storage medium herein may include both the built-in storage medium in the terminal device and, of course, the extended storage medium supported by the terminal device. It may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for being loaded and executed by a processor. These instructions may be one or more computer programs (including program code). It should be noted that more specific examples of the computer-readable storage medium herein include: an electrical connection having one or more wires, a portable disk, a hard disk, a random access memory, a read-only memory, an erasable programmable read-only memory, an optical fiber, a portable compact disk read-only memory, an optical storage device, a magnetic storage device, or any suitable combination thereof.

[0078] Computer-readable storage media also include data signals propagated in baseband or as part of a carrier wave, which carry readable program code. Such propagated data signals can take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable storage medium can also be any readable medium other than a readable storage medium, which can send, propagate, or transmit programs for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the readable storage medium can be transmitted using any appropriate medium, including but not limited to wireless, wired, optical cable, radio frequency, etc., or any suitable combination of the above.

[0079] The program code for performing the operations of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java, C++, and the like, as well as conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may be executed entirely on the user computing device, partially on the user device, as a stand-alone software package, partially on the user computing device and partially on a remote computing device, or entirely on a remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device via any type of network, including a local area network or a wide area network, or may be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0080] The processor may load and execute one or more instructions stored in a computer-readable storage medium to implement the corresponding steps of the method for disconnecting distributed power sources in a faulty section of an AC distribution network in the above embodiment. The processor may load and execute the following steps: When the power-frequency voltage sampling point of the fault phase meets the set conditions, protection is activated and a fault is determined to have occurred. The amplitude relationship between the opposite-end power-frequency fault current and the direction judgment threshold is calculated, and the opposite-end power-frequency fault current is used to determine the fault direction. A preset frequency characteristic signal is injected through the converter control loop to construct an active boundary to identify the fault direction. A matrix bundle algorithm is used to extract the characteristic signal as the protection judgment input. Based on the amplitude of the characteristic signal and local electrical quantities, the fault section is determined and the interlocking trip is triggered.

[0081] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may include, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic units, data processing logic units based on quantum computing, and the like.

[0082] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0083] In order to verify the correctness of the proposed single-ended full-line fast-acting protection method, a 10kV distribution network is taken as an example. The electromagnetic transient simulation software PSCAD is used to establish the following Figure 3 In the simulation model shown, the line where protection 1 is located at the local end in the topology is 10 km long, and DG1 is connected to the line at 3 km.

[0084] exist Figure 3In this example, distributed generation (DGs) are integrated into Protection 1, Protection 2, and Protection 3 to rapidly operate the entire line and co-trip the DGs in the faulted section. In the diagram, for Protection 2, f1 and f2 represent positive internal and external faults, respectively. The converter of DG 2 (DG2) can be used to establish an active boundary. DG1 is the DG in the faulted section. By coordinating the opposite-end converter with the local protection and DG protection in the faulted section, the DG co-trip protection in the faulted section can be achieved, establishing an active boundary for the line.

[0085] For Figure 3 In the distribution network model shown, a sinusoidal signal with a frequency f1 of 125 Hz is selected as the specific response characteristic signal when a fault occurs in the positive direction of the matching end interconnection line, and a sinusoidal signal with a frequency f2 of 175 Hz is selected as the specific response characteristic signal when a fault occurs outside the negative direction of the matching end interconnection line.

[0086] A two-phase short circuit fault with a transition resistance of 5Ω is set at the midpoint of the line section between protection 1 and protection 2 to verify the accuracy of the present invention in fault discrimination within the zone. The simulation results are shown in Figure 4. In Figure 4(a) and (c), u fi,max The maximum value of the three-phase voltage is collected at measuring point 1 and measuring point 3 under the characteristic frequency. u set is the setting value of the protection; Figure 4(b) is the amplitude-frequency characteristic of the voltage at protection measuring point 1.

[0087] Protection 2 determines the occurrence of a forward fault through the directional element. At the same time, the amplitude of the 125Hz information received at protections 1 and 3 exceeds the set value, which can reliably identify the fault in the line occurrence area.

[0088] A two-phase short-circuit fault with a transition resistance of 5Ω is set at f2 to verify the accuracy of the present invention in distinguishing out-of-zone faults. The simulation results are shown in Figure 5. In Figure 5(a) and (c), u fi,max are the maximum values ​​of the three-phase voltages at measuring points 1 and 3 at the characteristic frequency, u set Figure 5(b) shows the amplitude-frequency characteristics of the voltage at protection point 1.

[0089] Protection 2 determines that a reverse fault has occurred through the directional element. At the same time, the amplitude of the 175Hz information received at protections 1 and 3 exceeds the set value, which can reliably identify that an out-of-zone fault has occurred on the line.

[0090] Table 1. Protection 1 judgment results under phase-to-phase fault with transition resistance R=5Ω

[0091] Table 2. Protection 3 judgment results under phase-to-phase fault with transition resistance R=5Ω

[0092] Specific fault simulation results are shown in Table 1 and Table 2, and the simulation results prove the effectiveness of the present invention.

[0093] In summary, the present invention provides a method and system for disconnecting distributed power sources in a faulty section of an AC distribution network. Please summarize and explain the effects of the present invention.

[0094] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0095] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0096] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in the present invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0097] In the embodiments provided by the present invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For example, the division of the modules or units is merely a logical functional division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or units, and can be electrical, mechanical, or other forms.

[0098] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0099] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0100] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, it can implement the steps of the above-mentioned various method embodiments. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device capable of carrying the computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. It should be noted that the content contained in the computer-readable medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electric carrier signals and telecommunication signals.

[0101] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices, and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0102] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0103] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0104] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for disconnecting distributed power sources in a faulty section of an AC distribution network, characterized in that: The following steps are involved: When the power frequency voltage sampling point of the fault phase meets the set conditions, the protection is activated and it is determined that a fault has occurred; Calculate the amplitude relationship between the opposite-end power frequency fault current and the direction judgment threshold, and use the opposite-end power frequency fault current to determine the fault direction; A preset frequency characteristic signal is injected through the converter control loop to construct an active boundary to identify the fault direction; Matrix bundle algorithm is used to extract characteristic signals as protection criterion input; Based on the amplitude of the characteristic signal and local electrical quantities, the fault section is determined and the joint disconnection is triggered.

2. The method for disconnecting distributed power sources in a faulty section of an AC distribution network according to claim 1, characterized in that: When the sampling data is greater than the start criterion for three consecutive times, the protection mechanism is activated.

3. The method for disconnecting distributed power sources in a faulty section of an AC power distribution network according to claim 2, characterized in that: The startup criteria are as follows: in, The first phase voltage of the power frequency fault k The absolute value of the sampling points; The power frequency phase voltage in normal operation kN S The absolute value of the sampling points; N S is the number of sampling points in a sampling period; is the starting criterion threshold.

4. The method for disconnecting distributed power sources in a faulty section of an AC power distribution network according to claim 1, characterized in that: When the direction judgment threshold I set =1.2 I DGmax When the protection is started, the directional element starts calculating at the first sampling point that meets the start criterion. When , it is judged as a forward fault; otherwise, it is a reverse fault. I DGmax The maximum short-circuit current provided to downstream distributed generation.

5. The method for disconnecting distributed power sources in a faulty section of an AC distribution network according to claim 1, characterized in that: When the opposite end is judged to be a forward fault, the active boundary injects a preset characteristic frequency representing the opposite end forward fault f 1 signal; on the contrary, when it is judged as a reverse fault, the active boundary injects the preset characteristic frequency representing the reverse fault of the opposite end f 2 signals.

6. The method for disconnecting distributed power sources in a faulty section of an AC power distribution network according to claim 5, characterized in that: The characteristic signal voltage command injected into the active boundary is: in, is the voltage command amplitude, is the frequency of the voltage command, Initial phase of voltage command.

7. The method for disconnecting distributed power sources in a faulty section of an AC power distribution network according to claim 1, characterized in that: The matrix bundle algorithm is used to extract the characteristic signal. By constructing the Hankel matrix, determining the system order through singular value decomposition, constructing the D matrix and extracting the characteristic parameters, the amplitude and phase angle of the corresponding signal frequency are obtained as follows: in, A i 、 θ i are the amplitude and initial phase angle of the characteristic signal respectively, R i is the complex amplitude.

8. The method for disconnecting distributed power sources in a faulty section of an AC distribution network according to claim 1, characterized in that: If both the local protection and the distributed power supply side meet the judgment criteria, it is determined to be an internal fault and the distributed power supply in the faulty section is disconnected; if any of the judgment criteria is not met, it is determined to be an external fault and the protection is locked.

9. The method for disconnecting distributed power sources in a faulty section of an AC power distribution network according to claim 8, characterized in that: The criterion for the full-line quick-acting protection at the protection end is set as follows: The protection criteria for distributed power supply in the fault section are set as follows: in, I k is the fundamental frequency current on the protection side of this end, I L.max It is the maximum load current of the line during normal operation; U aω1 、 U bω1 、 U cω1 The frequencies representing the forward faults of the three phases of the protection end extracted by the matrix bundle algorithm are f 1 specific response voltage signal, U aω2 、 U bω2 、U cω2 The frequency of the reverse fault characterizing the three-phase protection end is f 2 voltage signal, U set is the setting value of protection; k is the reliability factor of protection, U DG is the fundamental frequency voltage on the distributed power supply side of the fault section, U E It is the fundamental frequency rated voltage of the distributed power supply side in the fault section.

10. A distributed power supply switching system for a fault section of an AC distribution network, characterized in that: include: The startup module starts the protection when the power frequency voltage sampling point of the fault phase meets the set conditions and determines that a fault has occurred; The discrimination module calculates the amplitude relationship between the opposite-end power frequency fault current and the direction judgment threshold, and uses the opposite-end power frequency fault current to discriminate the fault direction; The injection module injects a preset frequency characteristic signal through the converter control loop to construct an active boundary to identify the fault direction; Input module, which uses matrix bundle algorithm to extract characteristic signals as protection criterion input; The output module determines the fault section and triggers joint switching based on the amplitude of the characteristic signal and local electrical quantities.

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