New energy DC power distribution network fault identification method and system

Abstract

The invention discloses a new energy direct current power distribution network fault identification method and system, and belongs to the field of new energy direct current power distribution network control and protection. After a fault occurs, controlling all the power electronic direct-current transformers to start a current limiting strategy, and selecting the power electronic direct-current transformers on two feeder sides to adjust phase shift angles so as to inject a dual-frequency detection signal; listing a network equation based on a one-mode circuit fault-free model, collecting voltage and current signals of each feeder line, and solving line parameters and tail end equivalent capacitance; line fault identification is realized by calculating the relative capacitance deviation and combining a preset criterion; and if all the feeders have no fault, identifying a bus fault in combination with the feeder current according to a bus criterion. The method does not need to depend on communication, adapts to multiple feeder types, can accurately recognize line and bus faults, and effectively improves the fault detection and recognition capability of the new energy DC power distribution network.

Description

Technical Field

[0001] This invention belongs to the field of control and protection technology of new energy DC distribution networks, and specifically relates to a fault identification method and system for new energy DC distribution networks. Background Technology

[0002] To address the growing demand from high-proportion wind and solar power grid integration, as well as data centers and industrial DC loads, new energy DC distribution systems that optimize energy transmission paths and reduce power conversion stages are gaining increasing attention. In these systems, power electronic DC transformers possess excellent modularity and scalability, facilitating redundant configurations and enhancing system reliability. Simultaneously, their inherent voltage transformation and electrical isolation functions provide a foundation for building flexible and efficient DC network architectures. The extensive integration of highly controllable power electronic equipment allows for proactive current limiting during DC faults, reducing reliance on traditional high-capacity DC circuit breakers and enabling the use of lower-cost disconnect switches. This reduces the need for protection speed and enhances the focus on high reliability.

[0003] Existing protection schemes for new energy DC power distribution systems can be broadly categorized into two types: passive detection methods and active detection protection. Current research on passive detection methods mainly focuses on further mining fault information and improving algorithm performance to enhance protection reliability and sensitivity. However, to obtain pure fault characteristics before they are affected by the control effects of power electronic equipment, and to complete fault identification before the rapid blocking of power electronic equipment, the passive detection protection principle is being forced to evolve towards the traveling wave process at the initial moment of the fault. Research on passive detection protection principles operating over longer time periods is therefore limited. Active detection leverages the high controllability of power electronic devices to proactively inject characteristic signals into the faulty network, identifying faults based on the network's response to these signals. However, most existing active detection methods rely on communication methods or coordination between different protection devices, and research primarily focuses on modular multilevel converters (MMCs) and voltage source converters (VSCs) in AC / DC hybrid distribution networks. There are few collaborative control and protection schemes for DC distribution networks that utilize power electronic DC transformers for active injection.

[0004] To address the aforementioned issues, this invention proposes a fault identification scheme based on active injection from a power electronic DC transformer in a new energy DC power distribution system, thereby improving the fault detection and identification capabilities of the new energy DC power distribution system. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of the existing technology by providing a method and system for fault identification in new energy DC distribution networks. This method achieves synchronous injection of low-power dual-frequency detection signals by changing the phase shift angle of the power electronic DC transformer. Based on this, the terminal capacitance parameters of different feeders are identified, revealing that the calculated values ​​for healthy lines are close to the actual values, while those for faulty lines are significantly larger. Based on this, a relative capacitance deviation and fluctuation criterion is constructed to achieve fault line identification, thus solving the technical problems of insufficient timeliness of passive detection, reliance on communication / poor adaptability of active detection, and weak accuracy and adaptability in fault identification.

[0006] The present invention adopts the following technical solution: A method for fault identification in a new energy DC distribution network includes the following steps: When a fault occurs, the current limiting strategy is activated for all power electronic DC transformers in the new energy DC distribution network. The phase shift angle of the power electronic DC transformers on the m-th and m+1-th feeders is modulated to achieve synchronous injection of low-power dual-frequency detection signals. The voltage and current signals at the beginning of each feeder are collected under the dual-frequency detection signal. Based on the preset fault-free model network equation, the line parameters and terminal equivalent capacitance parameters of each feeder are solved. Calculate the relative capacitance deviation of each feeder ; Based on the obtained relative capacitance deviation, a preset line fault criterion is used to determine whether each feeder is a faulty line. When the relative capacitance deviation of all feeders is not greater than the preset setting value, the current at the beginning of all feeders is collected. If three consecutive sampling points meet the preset bus fault criteria, then the new energy DC distribution network is determined to have experienced a bus fault.

[0007] Preferably, the line parameters and terminal equivalent capacitance parameters of each feeder are solved as follows: Selected m The power electronic DC transformer on the feeder line adjusts the phase shift angle via additional control, with a superimposed frequency of [frequency value missing]. f sinusoidal modulation disturbance angle of 1 θ dec To achieve synchronous injection of low-power dual-frequency detection signals; based on the fault-free model of a single-mode circuit, write network equations at the detection signal frequency; Acquisition except for injection feeder m The voltage and current signals at the beginning of each of the other feeders are collected, and the real and imaginary parts of the network equations corresponding to the two injection frequencies in the fault-free model of the mode circuit at the probe signal frequency are extracted respectively. Four real equations are constructed to solve for the unknown parameters. R i , L i andC eq ; Selected m The power electronic DC transformer on feeder +1 adjusts the phase shift angle via additional control, with a superimposed frequency of... f sinusoidal modulation disturbance angle of 1 θ dec This enables the synchronous injection of low-power dual-frequency detection signals; Acquisition except for injection feeder m The voltage and current signals at the beginning of each feeder other than +1 are collected, and the real and imaginary parts of the network equations corresponding to the two injection frequencies in the fault-free model of the single-mode circuit at the probe signal frequency are extracted respectively. Four real equations are constructed to solve the first... i Line l i lumped resistor R i , No. i Line l i Concentrated inductance L i Equivalent capacitance of power electronic devices at the feeder end C eq .

[0008] Preferably, the fault-free model of the single-mode circuit writes the network equations below the frequency of the probe signal as follows:

[0009] in, and These represent the frequencies injected at the beginning of the protected line. f The voltage and current phasors measured below, and These represent the frequencies injected at the beginning of the protected line. f The voltage and current phasors measured below, R i and L i They represent the first i Line l i Lumped parameter resistor and inductance parameters, i =1, 2, ..., n , i ≠ m , C eq This represents the equivalent capacitance of the power electronic devices at the end of the feeder.

[0010] Preferably, if a power electronic DC transformer is connected to the end of the feeder, then C eq =CH / N i C H This indicates its high-voltage side capacitance. N i Indicates the first i The number of sub-modules connected in series on the high-voltage side of the power electronic DC transformer on the line; if the feeder is a wind power collection line, then C eq = C cov , C cov This represents the simplified equivalent capacitance parameter of the wind turbine converter.

[0011] Preferably, relative capacitance deviation for:

[0012] in, This represents the equivalent capacitance parameters of the power electronic devices at the end of each feeder obtained from the solution.

[0013] Preferably, the line fault criterion is:

[0014] in, It is the setting value for determining feeder faults.

[0015] Preferably, the setting value for determining feeder faults Take 0.1.

[0016] Preferably, the busbar criterion is:

[0017] in, I set The threshold for auxiliary judgment of bus faults For the sum of the currents of each feeder, Let J be the current value of feeder j. This represents the total number of feeders.

[0018] Preferably, the threshold of the bus fault auxiliary criterion I set The value is 0.05 pu.

[0019] Secondly, embodiments of the present invention provide a fault identification system for a new energy DC distribution network, comprising: The injection module, when a fault occurs, controls all power electronic DC transformers in the new energy DC distribution network to start the current limiting strategy, selects the power electronic DC transformers on the m-th and m+1-th feeders to modulate the phase shift angle, and realizes the synchronous injection of low-power dual-frequency detection signals. The acquisition module acquires the voltage and current signals at the beginning of each feeder under the dual-frequency detection signal, and solves the line parameters and terminal equivalent capacitance parameters of each feeder based on the preset fault-free model network equation. The calculation module calculates the relative capacitance deviation of each feeder. ; The judgment module uses a preset line fault criterion to determine whether each feeder is a faulty line based on the obtained relative capacitance deviation. The identification module collects the current at the beginning of all feeders when the relative capacitance deviation of all feeders is not greater than the preset setting value. If three consecutive sampling points meet the preset bus fault criteria, it determines that a bus fault has occurred in the new energy DC distribution network.

[0020] Thirdly, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method for identifying faults in a new energy DC distribution network.

[0021] Fourthly, embodiments of the present invention provide a computer-readable storage medium including a computer program, which, when executed by a processor, implements the steps of the above-described method for identifying faults in a new energy DC distribution network.

[0022] Fifthly, a chip includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described new energy DC distribution network fault identification method.

[0023] Sixthly, embodiments of the present invention provide an electronic device including a computer program, which, when executed by the electronic device, implements the steps of the above-described new energy DC distribution network fault identification method.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects: A fault identification method for new energy DC distribution networks is proposed. After a fault occurs, all power electronic DC transformers are first controlled to activate a current-limiting strategy, which quickly suppresses the fault current amplitude, preventing equipment damage due to overcurrent and providing a stable window for subsequent fault identification. This overcomes the timeliness limitations of passive detection, which requires identification before equipment lockout. By selecting a feeder and modulating the phase-shift angle to inject a dual-frequency detection signal, the method eliminates the need for multi-device communication or coordination, overcoming the communication bottleneck of existing active detection methods. Subsequent steps involve parameter calculation and deviation determination based on signal acquisition, followed by bus fault identification through current sampling. This forms a line-bus full-coverage identification logic, avoiding the limitation of traditional schemes that can only identify a single fault type. The current-limiting step provides a stable environment for signal injection, parameter calculation provides data support for deviation calculation, and deviation judgment and bus criterion complement each other, ensuring reliable identification under different fault scenarios and improving the completeness and stability of fault identification in new energy DC distribution networks.

[0025] Furthermore, by refining the parameter solution logic, the accuracy and reliability of fault identification are improved. The core of this approach is to write network equations based on a fault-free model of a single-mode circuit. This model eliminates interference from transient fault components, focusing on the steady-state electrical characteristics at the frequency of the probe signal. This ensures that the acquired voltage and current signals only reflect the inherent parameters of the line and the response of the probe signal, avoiding interference from fault transients in parameter solution and solving the problem of existing solutions being greatly affected by fault transients. By selecting two feeders, the m-th and m+1-th, to inject signals respectively, a data redundancy verification mechanism is formed. While injection from a single feeder may cause parameter deviations due to line interference, alternating injection from two feeders allows for error correction through data comparison, improving the accuracy of parameter solution. Meanwhile, the solution method for constructing four real equations by extracting the real and imaginary parts of the equations at two injection frequencies is clearly defined. For the three unknown parameters of resistance, inductance, and equivalent capacitance, the overdetermined solution of the four equations can reduce the impact of measurement noise on the results, ensure that the line parameters and the calculated value of the equivalent capacitance at the end are closer to the actual value, provide an accurate data basis for subsequent relative capacitance deviation calculation, avoid misjudgment of faults due to inaccurate parameters, and further enhance the accuracy of fault identification.

[0026] Furthermore, the specific network equations of the fault-free circuit model are clearly defined, providing a standardized and quantifiable mathematical basis for parameter solving in principle, thus solving the problems of fuzzy network models and unclear solution logic in existing schemes. The equations clearly define the quantitative relationships between voltage and current phasors at the beginning of the protected line and line parameters, as well as the equivalent capacitance at the end, at different frequencies. This transforms abstract electrical network characteristics into concrete mathematical expressions, enabling parameter solving to shift from empirical estimation to precise calculation. Simultaneously, the equations explicitly limit the applicable range of i=1, 2, ..., n, i≠m, ensuring that the signals collected from feeders other than the injected feeder m strictly match the parameters of the i-th line solved by the equations, avoiding inaccurate solutions for the injected feeder. This standardized equation design not only provides a unified basis for parameter solving in different scenarios, improving the repeatability and versatility of the method, but also allows for rapid location of parameter solving anomalies through the direct correlation between voltage and current phasors and parameters in the equations. This facilitates subsequent fault feature extraction, provides reliable mathematical support for relative capacitance deviation calculation, and indirectly improves the accuracy of fault diagnosis.

[0027] Furthermore, this method addresses the issue of inaccurate calculation of the equivalent capacitance Ceq at the end of the feeder in new energy DC distribution networks due to the diverse types of feeders, significantly improving its adaptability to different feeder scenarios. In new energy DC distribution networks, feeder ends may connect to power electronic DC transformers or wind turbine converters. The capacitance characteristics of these two types of equipment differ significantly: for power electronic DC transformers, the high-voltage side sub-modules are connected in series, and the capacitance needs to consider the voltage division effect, conforming to the electrical principle that the total capacitance of series capacitors is inversely proportional to the number of series capacitors; for wind turbine converters in wind power collection lines, the capacitance characteristics are uniform, and a simplified equivalent capacitance Ccov is directly used to match their actual electrical characteristics. Existing solutions often ignore the differences in feeder types and use a uniform formula to calculate Ceq, resulting in large deviations between the calculated and actual values, affecting fault diagnosis. This method sets separate calculation logics for the two typical feeder types to ensure accurate Ceq benchmark values ​​for different feeders, providing an accurate actual value reference for subsequent relative capacitance deviation calculations. This avoids the failure of deviation judgment due to inaccurate Ceq benchmark values, enabling reliable fault identification in different feeder scenarios such as wind power collection and load power supply, thus expanding the applicability of the method.

[0028] Furthermore, by clarifying the formula for calculating relative capacitance deviation, the "quantitative extraction" of fault characteristics is realized in principle, solving the problems of vague fault characteristics and strong subjectivity in judgment in existing solutions. The core logic of relative capacitance deviation is to quantify the degree of abnormality of line parameters by calculating the proportion of the difference. For healthy lines, due to the absence of fault interference, the calculated Ceq is close to the actual value with a small deviation; for faulty lines, due to the introduction of additional equivalent capacitance at the fault point, the calculated Ceq is significantly larger with a large deviation. This transforms the difference in capacitance parameters into a directly comparable numerical indicator, avoiding the reliance on easily disturbed characteristic quantities such as voltage fluctuation amplitude and current harmonic content in traditional solutions, and reducing the impact of environmental noise and load fluctuations on fault judgment. At the same time, the equivalent capacitance parameters of the power electronic devices at the end of each feeder obtained from the calculation are directly related to the parameter calculation results of the previous steps, forming a data closed loop of parameter calculation and deviation calculation, ensuring that the data source for deviation calculation is true and reliable. By quantifying the deviation, fault judgment is transformed from qualitative observation to quantitative comparison, improving the objectivity and consistency of judgment. Even in scenarios with different fault distances and varying transition resistances, the deviation values ​​can accurately distinguish between healthy and faulty lines, strengthening the robustness of fault identification.

[0029] Furthermore, by setting a fault criterion for lines with relative capacitance deviations exceeding a set value, a standardized fault judgment logic is constructed, solving the problems of existing solutions lacking clear criteria and being prone to misjudgment / missed judgment due to human experience. Utilizing the characteristic that the relative capacitance deviation of a faulty line is significantly greater than that of a healthy line, a clear threshold is established through a preset set value: when the deviation of a feeder exceeds the threshold, it is determined to be a faulty line; otherwise, it is a healthy line. This criterion is directly linked to the relative capacitance deviation calculation results of the preceding steps, forming a judgment link of deviation calculation-threshold comparison, ensuring logical consistency. Existing active or passive detection schemes often rely on fuzzy judgment methods such as signal response trends and waveform feature matching, which are prone to failure under complex operating conditions. This criterion achieves standardized judgment through a quantitative threshold, measuring all fault distances and transition resistances using the same standard, avoiding the problem of judgment standards changing with operating conditions and improving the stability of fault identification. At the same time, the criterion is concise and clear, easy to implement in engineering, and can be directly embedded into the algorithm logic of protection devices, reducing software programming complexity and providing convenience for engineering applications of fault identification.

[0030] Furthermore, in the actual operation of new energy DC distribution networks, sampling errors and data fluctuations can cause slight fluctuations in relative capacitance deviation. If the setting value is too small, normal fluctuations may be misjudged as faults, leading to malfunctions in protection. If the setting value is too large, minor faults may be missed, resulting in protection failure to operate. PSCAD simulation verification shows that a setting value of 0.1 can effectively avoid the influence of sampling errors and data fluctuations—the deviation of healthy lines is less than 0.1, while the deviation of faulty lines is much greater than 0.1. This setting value can accurately capture the abnormal characteristics of faulty lines while filtering interference signals under normal operating conditions. This setting value is based on actual simulation data, rather than subjective estimation, ensuring that the false trip rate and failure rate of fault identification are both low in engineering applications. This improves the practicality and engineering reliability of the method, providing key parameter support for the practical application of fault identification.

[0031] Furthermore, based on Kirchhoff's Current Law: when a bus fault occurs, the fault point is located on the bus, and each feeder itself is not faulty, so the relative capacitance deviation of all feeders does not exceed the set value; however, a bus fault will cause each feeder to supply current to the fault point. Although the output current of the grid connection point drops to zero under the current limiting strategy, the algebraic sum of the currents at the beginning of each feeder is still not zero. Based on this, the criterion sets that after the signal injection stabilizes for 10ms, three consecutive sampling points satisfy the current algebraic sum condition. This ensures that the sampling data is acquired after the detection signal reaches a steady state, and also eliminates misjudgments caused by instantaneous current fluctuations through the constraint of three consecutive sampling points. This criterion accurately locates the bus fault through the dual conditions of no line fault + abnormal current algebraic sum, filling the gap in bus fault identification in traditional solutions, forming a fault identification system covering the entire line-bus scenario, and improving the comprehensiveness of fault handling in new energy DC distribution networks.

[0032] It is understood that the beneficial effects of the second to sixth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0033] In summary, this invention does not rely on communication. It injects dual-frequency signals through a power electronic DC transformer, solves parameters using a single-mode model, identifies line faults based on relative capacitance deviation criteria, and determines bus faults based on the KCL principle. It is adaptable to multiple feeder types, has strong anti-interference capabilities, is unaffected by fault distance or transition resistance, and can accurately cover line and bus faults, significantly improving the accuracy and reliability of fault identification in new energy DC distribution networks.

[0034] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the identification process of the present invention; Figure 2 This is a model diagram of the new energy DC distribution network of the present invention; Figure 3 A schematic diagram of a computer device provided in an embodiment of the present invention; Figure 4 This is a block diagram of a chip provided according to an embodiment of the present invention.

[0036] Among them, 60. Computer equipment; 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 Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0039] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this 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.

[0040] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0041] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the 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.

[0042] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0043] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0044] This invention provides a fault identification method for new energy DC distribution networks. It utilizes the control characteristics of power electronic DC transformers to actively generate detection signals, eliminating the need for additional equipment and avoiding the delay problem of passive detection relying on the natural characteristics of faults. Based on the capacitance parameter deviation, a criterion is constructed, where the calculated equivalent capacitance of the faulty line deviates significantly from the actual value and is less affected by the transition resistance. A bus current criterion is introduced, and when there is no fault in the line, the algebraic sum of non-zero currents is detected by the KCL law to accurately distinguish between line faults and bus faults. By actively injecting dual-frequency detection signals combined with the relative capacitance deviation criterion, the core problem of fault identification in new energy DC distribution networks is solved.

[0045] Please see Figure 1 The present invention provides a fault identification method for a new energy DC distribution network, comprising the following steps: S1. After the fault occurs, all power electronic DC transformers in the DC distribution network activate the current limiting strategy, and select one of the feeders (assuming it is the first one). m The power electronic DC transformer on the strip adjusts the phase shift angle through additional control, with a superimposed frequency of [frequency value missing]. f sinusoidal modulation disturbance angle of 1 θ dec To achieve low-power dual-frequency detection signal ( f 1 and 2f 1) Synchronous injection; S2. Write the network equations based on the fault-free model of a single-mode circuit at the frequency of the detection signal. The calculation formula is as follows: (1) in, and These represent the frequencies injected at the beginning of the protected line. f The voltage and current phasors measured below, and These represent the frequencies injected at the beginning of the protected line. f The voltage and current phasors measured below, R i and L i They represent the first i Line l i ( i =1, 2, ..., n , i ≠ m Lumped parameter resistance and inductance parameters, C eq This represents the equivalent capacitance of the power electronic devices at the end of the feeder. If a power electronic DC transformer is connected to the end of the feeder, then... C eq =C H / N i C H This indicates its high-voltage side capacitance. N i ( i =1, 2, ..., n , i ≠ m ) indicates the first i The number of sub-modules connected in series on the high-voltage side of the power electronic DC transformer on this line; if the feeder is a wind power collection line, then... C eq = C cov , C cov This represents the simplified equivalent capacitance parameter of the wind turbine converter.

[0046] S3, Acquisition except for injection feeder m The voltage and current signals at the beginning of each of the other feeders are collected, and the real and imaginary parts of the equations corresponding to the two injection frequencies in step S2 are extracted respectively. Four real equations are constructed to solve for the unknown parameters. R i , L i andC eq ; S4. Select another feeder (assuming it is the first one). m The power electronic DC transformer on (+1 item) adjusts the phase shift angle through additional control, with a superimposed frequency of... f sinusoidal modulation disturbance angle of 1 θ dec To achieve low-power dual-frequency detection signal ( f 1 and 2 f 1) Synchronous injection; S5. Write the network equations for the detection frequency signal based on the fault-free model of a single-mode circuit. The calculation formula is as follows: (2) in, i =1, 2, ..., n , i ≠( m +1).

[0047] S6, Acquisition except for injection feeder m The voltage and current signals at the beginning of each feeder other than +1 are collected, and the real and imaginary parts of the equations corresponding to the two injection frequencies in step S2 are extracted respectively. Four real equations are constructed to solve for the unknown parameters. R i , L i and C eq ; S7. Calculate the values ​​of each feeder ( i =1, 2, ..., n The relative capacitance deviation; The calculation formula is as follows: (3) in, This represents the equivalent capacitance parameters of the power electronic devices at the end of each feeder obtained from the solution.

[0048] S8. Identify line faults; Use the following formula to diagnose faults: (4) in, It is the setting value for determining feeder faults.

[0049] Considering the impact of sampling errors and data fluctuations, this invention Take 0.1.

[0050] S9. When all protection measurement points of all lines fail to meet the internal line fault criteria, it is necessary to further determine whether a bus fault has occurred. For bus faults, according to Kirchhoff's Current Law (KCL), although the output current of the grid connection point will drop to zero under the current limiting strategy, the algebraic sum of the currents of each line is still not zero. Therefore, the following bus fault criterion is introduced: after the signal is injected and stabilized for 10 ms, if three consecutive sampling points meet the criterion, the fault is determined to be a bus fault, thus obtaining a fault identification scheme for new energy DC distribution networks based on active injection by power electronic DC transformers.

[0051] Busbar criteria: (5) in, I set The threshold value for the auxiliary criterion of bus faults is 0.05 pu in this invention.

[0052] In another embodiment of the present invention, a fault identification system for a new energy DC distribution network is provided. This system can be used to implement the above-mentioned fault identification method for a new energy DC distribution network. Specifically, the fault identification system for a new energy DC distribution network includes an injection module, a data acquisition module, a calculation module, a judgment module, and an identification module.

[0053] Among them, the injection module controls all power electronic DC transformers in the new energy DC distribution network to start the current limiting strategy after a fault occurs, selects the power electronic DC transformers on the m-th and m+1-th feeders to modulate the phase shift angle, and realizes the synchronous injection of low-power dual-frequency detection signals. The acquisition module acquires the voltage and current signals at the beginning of each feeder under the dual-frequency detection signal, and solves the line parameters and terminal equivalent capacitance parameters of each feeder based on the preset fault-free model network equation. The calculation module calculates the relative capacitance deviation of each feeder. ; The judgment module uses a preset line fault criterion to determine whether each feeder is a faulty line based on the obtained relative capacitance deviation. The identification module collects the current at the beginning of all feeders when the relative capacitance deviation of all feeders is not greater than the preset setting value. If three consecutive sampling points meet the preset bus fault criteria, it determines that a bus fault has occurred in the new energy DC distribution network.

[0054] This invention provides a terminal device comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or 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 and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment can be used in the operation of a fault identification method for new energy DC distribution networks, including: When a fault occurs, the current-limiting strategy is activated for all power electronic DC transformers in the new energy DC distribution network. The phase-shift angle of the power electronic DC transformers on feeders m and m+1 is modulated to achieve synchronous injection of low-power dual-frequency detection signals. Voltage and current signals at the beginning of each feeder under the dual-frequency detection signals are collected. Based on the preset fault-free model network equations, the line parameters and equivalent capacitance parameters at the ends of each feeder are solved. The relative capacitance deviation of each feeder is calculated. Based on the obtained relative capacitance deviation, a preset line fault criterion is used to determine whether each feeder is a faulty line; when the relative capacitance deviation of all feeders is not greater than the preset setting value, the current at the beginning of all feeders is collected. If three consecutive sampling points meet the criteria, it is determined that a bus fault has occurred in the new energy DC distribution network.

[0055] Please see Figure 3 The terminal device is a computer device. In this embodiment, the computer device 60 includes a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and executable on the processor 61. When executed by the processor 61, the computer program 63 implements the method for estimating the concentration of radioactive iodine species in the containment structure after an accident, as described in this embodiment. To avoid repetition, these details are not elaborated here. Alternatively, when executed by the processor 61, the computer program 63 implements the functions of each model / unit in the fault identification system of the new energy DC distribution network in this embodiment. To avoid repetition, these details are not elaborated here.

[0056] Computer device 60 can be a desktop computer, laptop, handheld computer, cloud server, or other computing device. Computer device 60 may include, but is not limited to, a processor 61 and a memory 62. Those skilled in the art will understand that... Figure 3 This is merely an example of computer device 60 and does not constitute a limitation on computer device 60. It may include more or fewer components than shown, or combine certain components, or different components. For example, computer device may also include input / output devices, network access devices, buses, etc.

[0057] The processor 61 may be a Central Processing Unit (CPU), or 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. A general-purpose processor may be a microprocessor or any conventional processor.

[0058] The memory 62 can be an internal storage unit of the computer device 60, such as a hard disk or RAM of the computer device 60. The memory 62 can also be an external storage device of the computer device 60, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., provided on the computer device 60.

[0059] Furthermore, the memory 62 may include both internal storage units of the computer device 60 and external storage devices. The memory 62 is used to store computer programs and other programs and data required by the computer device. The memory 62 can also be used to temporarily store data that has been output or will be output.

[0060] Please see Figure 4The terminal device is an electronic device 600, which is manifested in the form of 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 storage unit 620 and processing unit 610), a display unit 640, etc.

[0061] The storage unit stores program code, which can be executed by the processing unit 610 to perform the steps described in the method section of this specification according to various exemplary embodiments of the present invention. For example, the processing unit 610 can perform actions such as... Figure 1 The steps are shown in the figure.

[0062] Storage unit 620 may include a readable medium in the form of a volatile storage unit, such as random access memory (RAM) 6201 and / or cache memory 6202, and may further include a read-only memory (ROM) 6203.

[0063] Storage unit 620 may also include a program / utility 6204 having a set (at least one) program module 6205, such program module 6205 including but not limited to: operating system, one or more application programs, other program modules and program data, each or some combination of these examples may include an implementation of a network environment.

[0064] Bus 630 can represent one or more of several types of bus structures, including a memory cell bus or memory cell controller, a peripheral bus, a graphics acceleration port, a processing unit, or a local bus using any of the multiple bus structures.

[0065] Electronic device 600 can also communicate with one or more external devices 700 (e.g., keyboard, pointing device, Bluetooth device, etc.), and with one or more devices that enable a user to interact with electronic device 600, and / or with any device that enables electronic device 600 to communicate with one or more other computing devices (e.g., router, modem). This communication can be performed via input / output interface 650. Furthermore, electronic device 600 can also communicate with one or more networks (e.g., local area network, wide area network, and / or public network, such as the Internet) via network adapter 660. Network adapter 660 can communicate with other modules of electronic device 600 via bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with 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.

[0066] Example 4 This invention also provides a storage medium, specifically a computer-readable storage medium, which is a memory device in a terminal device for storing programs and data. It is understood that the computer-readable storage medium here can include both built-in storage media in the terminal device and extended storage media supported by the terminal device; it can 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 loading and execution by a processor, which can be one or more computer programs (including program code). More specific examples of the computer-readable storage medium include: an electrical connection with one or more wires, a portable disk, a hard disk, random access memory, read-only memory, erasable programmable read-only memory, optical fiber, portable compact disk read-only memory, optical storage device, magnetic storage device, or any suitable combination thereof.

[0067] Computer-readable storage media also include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable storage medium can also be any readable medium other than a readable storage medium that can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the readable storage medium can be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, radio frequency, etc., or any suitable combination thereof.

[0068] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute 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. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0069] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the fault identification method for new energy DC distribution networks in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor in the following steps: When a fault occurs, the current-limiting strategy is activated for all power electronic DC transformers in the new energy DC distribution network. The phase-shift angle of the power electronic DC transformer on the m-th feeder is modulated to achieve synchronous injection of low-power dual-frequency detection signals. The voltage and current signals at the beginning of each feeder (excluding the m-th feeder) under the dual-frequency detection signals are collected. Based on the preset fault-free model network equations, the line parameters and equivalent capacitance parameters at the end of each feeder are solved. The relative capacitance deviation of each feeder is calculated. Based on the obtained relative capacitance deviation, a preset line fault criterion is used to determine whether each feeder is a faulty line; when the relative capacitance deviation of all feeders is not greater than the preset setting value, the current at the beginning of all feeders is collected. If three consecutive sampling points meet the criteria, it is determined that a bus fault has occurred in the new energy DC distribution network.

[0070] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0071] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0072] To further verify the method proposed in this invention, a simulation model was established in the electromagnetic transient simulation software PSCAD as follows: Figure 2 The diagram shows a new energy DC distribution network model. This system is a hybrid wind-solar-storage access structure, where each component is boosted by a converter before being routed through a collection branch. l 1 to l 3. Connect to the collection bus, and then via the DC transmission line.l 0 accesses remote sites; among which, branch lines l 4 and l 5 are each connected to a DC load. Considering the short transmission distance of this system, the merging branch... l 1 to l 5. Load switches are only configured on the busbar side, while DC transmission lines... l Load switches are configured at both ends for isolation and protection. The main system parameters are as follows: the rated voltage of the DC grid is ±10 kV; the power electronic DC transformer submodules adopt a parallel input and series output structure, with a total of 10 submodules configured; DC transmission lines... l The length is 25 km, and it converges with branch roads. l 1. l 2. l The three are 10 km, 8 km, and 5 km respectively, for load-bearing branch roads. l 4 and l All five are 10 km long.

[0073] The protection discrimination results for different fault locations are shown in Table 1. The specific fault settings are as follows: f 1 to f 3 represents an inter-pole short-circuit fault on the collecting branch. f 4 and f 5 indicates an inter-pole short-circuit fault on the load feeder. f 6 indicates a DC bus fault. f 7 represents an inter-pole short-circuit fault on the DC transmission line. In this simulation, the threshold for the bus criterion is set to 21.21 A.

[0074] Table 1 Protection discrimination under different fault conditions

[0075] Table 1 shows that for fault-collecting branches, the calculated equivalent capacitance is greater than the actual parameter; while the parameters of the corresponding healthy branches remain within a reasonable range. For DC bus faults or DC transmission line faults, the protection measurement points of each branch do not meet the internal fault criteria, but they do meet the auxiliary fault criteria for bus faults. Therefore, the proposed method can accurately identify faulty branches at different fault locations, and is not affected by fault distance or transition resistance, effectively verifying the feasibility and effectiveness of the proposed fault identification method for new energy DC distribution networks based on active injection from power electronic DC transformers.

[0076] In summary, this invention provides a fault identification method and system for new energy DC distribution networks. By identifying the terminal capacitance parameters of different feeders, it was found that the calculated values ​​for healthy lines are close to the actual values, while those for faulty lines are significantly larger. Based on this, a relative capacitance deviation and fluctuation criterion is constructed to achieve fault line identification. This method can effectively improve the fault detection and identification capabilities of new energy DC distribution systems, solving the problems of insufficient accuracy and sensitivity in fault detection and identification in existing technologies. Through simulation verification, this method can accurately identify faulty branches at different fault locations and is unaffected by fault distance and transition resistance, verifying the feasibility and effectiveness of the proposed fault identification method for new energy DC distribution networks based on active injection from power electronic DC transformers.

[0077] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to 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 embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0078] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0079] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0080] In the embodiments provided by this 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 instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0081] The units described as separate components may or may not be physically separate. 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 the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0082] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0083] If the integrated module / unit is implemented as 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, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random-access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed 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 electrical carrier signals and telecommunication signals.

[0084] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus, and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0085] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0086] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0087] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for fault identification in a new energy DC distribution network, characterized in that, Includes the following steps: S1. When a fault occurs, control all power electronic DC transformers in the new energy DC distribution network to start the current limiting strategy, select the power electronic DC transformers on the m-th and m+1-th feeders to modulate the phase shift angle, and realize the synchronous injection of low-power dual-frequency detection signals. S2. Collect the voltage and current signals at the beginning of each feeder under the dual-frequency detection signal, and solve the line parameters and terminal equivalent capacitance parameters of each feeder based on the preset fault-free model network equation. S3. Calculate the relative capacitance deviation of each feeder. ; S4. Based on the obtained relative capacitance deviation, use the preset line fault criteria to determine whether each feeder is a faulty line. S5. When the relative capacitance deviation of all feeders is not greater than the preset setting value, collect the current at the beginning of all feeders. If three consecutive sampling points meet the preset bus fault criterion, it is determined that a bus fault has occurred in the new energy DC distribution network.

2. The fault identification method for new energy DC distribution networks according to claim 1, characterized in that, Solve for the line parameters and terminal equivalent capacitance parameters of each feeder, specifically: Selected m The power electronic DC transformer on the feeder line adjusts the phase shift angle via additional control, with a superimposed frequency of [frequency value missing]. f sinusoidal modulation disturbance angle of 1 θ dec To achieve synchronous injection of low-power dual-frequency detection signals; based on the fault-free model of a single-mode circuit, write network equations at the detection signal frequency; Acquisition except for injection feeder m The voltage and current signals at the beginning of each of the other feeders are collected, and the real and imaginary parts of the network equations corresponding to the two injection frequencies in the fault-free model of the mode circuit at the probe signal frequency are extracted respectively. Four real equations are constructed to solve for the unknown parameters. R i , L i and C eq ; Selected m The power electronic DC transformer on feeder +1 adjusts the phase shift angle via additional control, with a superimposed frequency of... f sinusoidal modulation disturbance angle of 1 θ dec This enables the synchronous injection of low-power dual-frequency detection signals; Acquisition except for injection feeder m The voltage and current signals at the beginning of each feeder other than +1 are collected, and the real and imaginary parts of the network equations corresponding to the two injection frequencies in the fault-free model of the single-mode circuit at the probe signal frequency are extracted respectively. Four real equations are constructed to solve the first... i Line l i lumped resistor R i , No. i Line l i Concentrated inductance L i Equivalent capacitance of power electronic devices at the feeder end C eq .

3. The fault identification method for new energy DC distribution networks according to claim 2, characterized in that, The fault-free model of a single-mode circuit has the following network equations at the frequency of the probe signal: in, and These represent the frequencies injected at the beginning of the protected line. f The voltage and current phasors measured below, and These represent the frequencies injected at the beginning of the protected line. f The voltage and current phasors measured below, R i and L i They represent the first i Line l i Lumped parameter resistor and inductance parameters, i =1, 2, ..., n , i ≠ m , C eq This represents the equivalent capacitance of the power electronic devices at the end of the feeder.

4. The fault identification method for new energy DC distribution networks according to claim 3, characterized in that, If a power electronic DC transformer is connected to the end of the feeder, then C eq =C H / N i C H This indicates its high-voltage side capacitance. N i Indicates the first i The number of sub-modules connected in series on the high-voltage side of the power electronic DC transformer on the line; if the feeder is a wind power collection line, then C eq = C cov , C cov This represents the simplified equivalent capacitance parameter of the wind turbine converter.

5. The fault identification method for new energy DC distribution networks according to claim 1, characterized in that, Relative capacitance deviation for: in, This represents the equivalent capacitance parameters of the power electronic devices at the end of each feeder obtained from the solution.

6. The fault identification method for new energy DC distribution networks according to claim 1, characterized in that, The line fault criterion is as follows: in, It is the setting value for determining feeder faults.

7. The fault identification method for new energy DC distribution networks according to claim 6, characterized in that, Setting values ​​for determining feeder faults Take 0.

1.

8. The fault identification method for new energy DC distribution networks according to claim 1, characterized in that, Busbar criteria: in, I set The threshold for auxiliary judgment of bus faults For the sum of the currents of each feeder, Let J be the current value of feeder j. This represents the total number of feeders.

9. The fault identification method for new energy DC distribution networks according to claim 8, characterized in that, Threshold of auxiliary criterion for bus fault I set The value is 0.05 pu.

10. A fault identification system for a new energy DC distribution network, characterized in that, include: The injection module, when a fault occurs, controls all power electronic DC transformers in the new energy DC distribution network to start the current limiting strategy, selects the power electronic DC transformers on the m-th and m+1-th feeders to modulate the phase shift angle, and realizes the synchronous injection of low-power dual-frequency detection signals. The acquisition module acquires the voltage and current signals at the beginning of each feeder under the dual-frequency detection signal, and solves the line parameters and terminal equivalent capacitance parameters of each feeder based on the preset fault-free model network equation. The calculation module calculates the relative capacitance deviation of each feeder. ; The judgment module uses a preset line fault criterion to determine whether each feeder is a faulty line based on the obtained relative capacitance deviation. The identification module collects the current at the beginning of all feeders when the relative capacitance deviation of all feeders is not greater than the preset setting value. If three consecutive sampling points meet the preset bus fault criteria, it determines that a bus fault has occurred in the new energy DC distribution network.

Images