Power distribution network protection method, system, device and storage medium adaptive to photovoltaic access

Abstract

The application relates to the field of electronic power technology and discloses a power distribution network protection method, system, equipment and storage medium suitable for photovoltaic access. The method comprises the following steps: a simplified model of a power distribution network is established based on the type, capacity and position of distributed power sources in the power distribution network; the simplified model is analyzed according to preset fault conditions of the power distribution network to obtain an initial relay protection model of the power distribution network; simulation test verification is carried out in a preset application scene to obtain electromechanical transient simulation results of the initial relay protection model, the initial relay protection model is optimized to obtain a target relay protection model; current state information during power distribution network operation is monitored; and the current state information is analyzed based on the target relay protection model to determine whether relay protection is executed on the power distribution network. When the power distribution network is monitored, the power distribution network is protected by the optimized target relay protection model, the relay protection is ensured to be reliable and sensitive, and the operation stability of the power distribution network after the distributed power sources are accessed is improved.

Description

Technical Field

[0001] This invention relates to the field of electronic power technology, and in particular to a distribution network protection method, system, device and storage medium adapted to photovoltaic access. Background Technology

[0002] Economic and social development has led to a continuous increase in human demand for energy, making the development and widespread use of new energy sources a hot topic in power grid energy development. For example, clean energy sources such as distributed photovoltaic (PV) power on the distribution network side contribute to the construction of new power systems. In addition to being characterized by low pollution, high reliability and energy efficiency, and flexible installation locations, distributed power sources, such as PV, are well-suited to the dispersed nature of electricity demand and resource distribution, making them an important measure to resolve the contradictions between economic development, energy production and consumption, and environmental protection.

[0003] However, the high penetration rate of distributed photovoltaic (PV) power generation in the distribution network poses significant challenges to its safe operation, creating potential hazards and causing malfunctions in instantaneous and time-limited instantaneous overcurrent protection systems, thus affecting the network's operational reliability. Furthermore, the extensive use of power electronics technologies following the integration of PV and other distributed power sources may lead to equipment damage and delayed restoration of faulty lines, increasing power outage time for users and reducing the reliability of the distribution system. Therefore, in-depth research into the impact of distributed power sources on the distribution network and corresponding improvement strategies has become an urgent issue to address.

[0004] The above content is only used to help understand the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention

[0005] The main objective of this invention is to provide a distribution network protection method, system, device, and storage medium adapted to photovoltaic access, aiming to solve the technical problem that the current relay protection methods are insufficient after distributed power sources are connected to the distribution network, resulting in reduced reliability of the distribution network operation.

[0006] To achieve the above objectives, the present invention provides a distribution network protection method adapted to photovoltaic (PV) grid integration, the method comprising:

[0007] A simplified model of the distribution network is established based on the type, capacity, and location of distributed power sources in the distribution network;

[0008] The simplified model is analyzed based on the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network.

[0009] In a preset application scenario, the distribution network is simulated and tested using the initial relay protection model to obtain electromechanical transient simulation results.

[0010] The initial relay protection model is optimized based on the electromechanical transient simulation results to obtain the target relay protection model;

[0011] Monitor the operation of the power distribution network and obtain its current status information;

[0012] The current state information is analyzed based on the target relay protection model to determine whether to perform relay protection on the distribution network.

[0013] In some embodiments, establishing a simplified model of the distribution network based on the type, capacity, and location of distributed power sources in the distribution network includes:

[0014] Based on the fault characteristics and bidirectional power flow of distributed power sources, a protection configuration model for the distributed power sources with preset access capacity and location is established.

[0015] The protection configuration model of the distributed power source is simplified based on the control characteristics of power electronic equipment to obtain a simplified model of the distribution network.

[0016] In some embodiments, the step of analyzing the simplified model based on preset fault conditions of the distribution network to obtain an initial relay protection model for the distribution network includes:

[0017] Obtain the preset fault types of the current line protection mode; wherein, the current line protection mode includes three-stage current protection mode and differential protection mode;

[0018] Based on the risk and mechanism of erroneous / failure to operate of the protection criterion under the preset fault type in the preset access distribution network scenario, a preset fault condition is generated;

[0019] Based on the preset fault conditions, new criteria and schemes for relay protection are proposed to analyze the simplified model and obtain the initial relay protection model of the distribution network.

[0020] In some embodiments, the step of performing simulation testing and verification of the distribution network using the initial relay protection model in a preset application scenario to obtain electromechanical transient simulation results includes:

[0021] Obtain the protection setting calculation model for distributed power source access to the distribution network under preset operating conditions;

[0022] Based on the protection setting calculation model, the setting setting under the preset operating mode and the adaptability of the initial relay protection model are analyzed in the preset application scenario to obtain the electromechanical transient simulation results; wherein, the electromechanical transient simulation results include the online setting setting under the preset operating mode and the adaptive protection performance of the relay protection device.

[0023] In some embodiments, optimizing the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model includes:

[0024] Based on the electromechanical transient simulation results, a target relay protection model based on multi-terminal current amplitude comparison is constructed by utilizing the relationship between the amplitude of the current at both ends and the comprehensive load current under normal operation and fault conditions inside and outside the zone.

[0025] In some embodiments, after constructing a target relay protection model based on multi-terminal current amplitude comparison using the magnitude relationship between the terminal currents and the comprehensive load current amplitude under normal operation and internal / external fault conditions, according to the electromechanical transient simulation results, the method further includes:

[0026] Based on the distribution network operation status, fault initial angle, fault type, and grounding impedance value, the applicable scope of the target relay protection model based on multi-terminal current amplitude comparison is analyzed, and the discrimination dead zone of the target relay protection model based on multi-terminal current amplitude comparison is determined.

[0027] In some embodiments, analyzing the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network includes:

[0028] When the analysis of the current status information determines that the fault point is located in the discrimination dead zone, the target protection scheme is composed of the overcurrent three-stage protection mode with direction judgment function, the overcurrent instantaneous overcurrent protection mode, and the target relay protection model.

[0029] The distribution network is subjected to relay protection according to the target protection scheme.

[0030] Furthermore, to achieve the above objectives, the present invention also proposes a distribution network protection system adapted to photovoltaic (PV) grid integration, wherein the distribution network protection system adapted to PV grid integration includes:

[0031] A module is established to create a simplified model of the distribution network based on the type, capacity, and location of distributed power sources in the distribution network.

[0032] An analysis module is used to analyze the simplified model based on the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network.

[0033] The simulation module is used to perform simulation tests and verifications on the distribution network in a preset application scenario using the initial relay protection model, so as to obtain electromechanical transient simulation results.

[0034] The optimization module is used to optimize the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model;

[0035] The monitoring module is used to monitor the operation of the power distribution network and obtain the current status information of the power distribution network.

[0036] The judgment module is used to analyze the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network.

[0037] Furthermore, to achieve the above objectives, the present invention also proposes a distribution network protection device adapted to photovoltaic access. The distribution network protection device adapted to photovoltaic access includes: a memory, a processor, and a program stored in the memory and executable on the processor. When the program is executed by the processor, it implements the steps of the distribution network protection method adapted to photovoltaic access as described in the above embodiments.

[0038] Furthermore, to achieve the above objectives, the present invention also proposes a storage medium storing a distribution network protection program adapted to photovoltaic access, wherein when the distribution network protection program adapted to photovoltaic access is executed by a processor, the steps of the distribution network protection method adapted to photovoltaic access as described in the above embodiments are implemented.

[0039] This invention establishes a simplified model of the distribution network based on the type, capacity, and location of distributed generation sources. It then analyzes the simplified model according to preset fault conditions of the distribution network to obtain an initial relay protection model. Simulation tests are conducted on the distribution network using this initial relay protection model in preset application scenarios to obtain electromechanical transient simulation results. The initial relay protection model is optimized based on these results to obtain a target relay protection model. The operation of the distribution network is monitored to obtain its current state information. Finally, the current state information is analyzed based on the target relay protection model to determine whether relay protection should be implemented. This invention protects the distribution network using the optimized target relay protection model during monitoring, ensuring reliable and sensitive relay protection. This improves the operational stability of distributed generation sources after they are connected to the distribution network and solves the technical problem of insufficient relay protection methods that reduce the reliability of the distribution network after distributed generation sources are connected. Attached Figure Description

[0040] Figure 1This is a schematic diagram of the structure of a distribution network protection device adapted to photovoltaic access in the hardware operating environment of the embodiment of the present invention;

[0041] Figure 2 This is a flowchart illustrating the first embodiment of the distribution network protection method adapted to photovoltaic access of the present invention;

[0042] Figure 3 This is a flowchart illustrating the second embodiment of the distribution network protection method adapted to photovoltaic access of the present invention;

[0043] Figure 4 This is a structural block diagram of the first embodiment of the distribution network protection system adapted to photovoltaic access of the present invention.

[0044] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0045] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0047] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0048] As the world's largest emitter of greenhouse gases, China put forward its long-term climate goal for the first time at the United Nations General Assembly in late September 2020, which is to build a new power system based on new energy sources.

[0049] The widespread integration of clean energy sources such as distributed photovoltaic (PV) power into the distribution network is a crucial way to contribute to the construction of a new power system from the distribution network side. Besides its advantages of low pollution, high reliability and energy efficiency, and flexible installation locations, distributed power sources, such as PV, are well-suited to the dispersed nature of electricity demand and resource distribution. This makes them a vital measure to address the contradictions between economic development, energy production and consumption, and environmental protection. On March 1, 2021, the State Grid Corporation of China explicitly stated: "Vigorously develop clean energy, maximize the development and utilization of new energy sources such as wind power and solar power, and adhere to both centralized and distributed development." It further stated that "by 2025, the distributed PV capacity in the company's operating area will reach 180 million kilowatts, and non-fossil energy will account for 20% of primary energy consumption." On June 20, 2021, the National Energy Administration officially issued the "Pilot Program for the Development of Distributed Photovoltaic Power Generation on Rooftops in Entire Counties (Cities, Districts)," which set clear goals for the development of distributed photovoltaic power generation: "No less than 50% of the total roof area of ​​government buildings can be equipped with photovoltaic power generation; no less than 40% of the total roof area of ​​public buildings such as schools, hospitals, and village committees can be equipped with photovoltaic power generation; no less than 30% of the total roof area of ​​industrial and commercial buildings can be equipped with photovoltaic power generation; and no less than 20% of the total roof area of ​​rural residential buildings can be equipped with photovoltaic power generation."

[0050] However, the high penetration rate of distributed photovoltaic (PV) systems in the distribution network poses significant challenges to the safe operation of the network, primarily in the following aspects: First, PV output power is highly dependent on weather changes. Natural variations such as solar radiation cause fluctuations in PV system power, and user loads also change in real time, with these changes not synchronized with the PV power generation patterns. With high PV penetration, the power generated by PV may exceed the load demand, leading to reverse power flow along feeders and causing feeder voltage rises, sometimes exceeding upper limits, posing a threat to the safe and stable operation of the system. The continuous integration of distributed energy sources like PV impacts the configuration and settings of distribution network automation systems and protection systems. When the PV power output is less than its rated power, the short-circuit current level in the distribution network may be higher than when the PV power output is at its rated power. According to existing setting schemes for the distribution network's instantaneous and time-limited instantaneous overcurrent protection, malfunctions may occur when the PV power output is less than its rated power. Considering the fluctuating nature of PV power output, which is often less than its rated power... Therefore, setting the distribution network current protection based on the short-circuit current level of the distribution network when the photovoltaic power source outputs its rated power will affect the safety and reliability of the distribution network operation.

[0051] It is evident that the high-density, large-scale integration of distributed generation into the distribution network alters the distribution of short-circuit currents, significantly impacting the correct operation of protection systems. Furthermore, distributed generation typically connects to medium- or low-voltage distribution systems, which are mostly single-source radial structures employing instantaneous or time-limited instantaneous protection methods, lacking directionality. While this protection method effectively protects all lines in existing radial distribution networks, the injected power reduces the relay protection range after the integration of distributed generation, failing to reliably protect the entire line and even causing malfunctions in relay protection systems connected to distributed generation systems during faults in other parallel branches. More importantly, the extensive use of power electronics technology following the integration of distributed generation, such as photovoltaic power, fundamentally alters the fault characteristics of the distribution system, leading to unclear fault current characteristics and fault calculation models. If a fault occurs on a line containing a renewable energy source and its protection trips, and the source fails to disconnect to avoid reclosing, asynchronous reclosing of the faulty line may occur, causing equipment damage, delays in restoring the faulty line, increased power outage time for users, and reduced reliability of the distribution system. To ensure the stable and efficient operation of distributed power sources, it is of great significance to study new distribution network protection schemes and parameter setting specifications applicable to distributed power sources after their integration.

[0052] Secondly, in distribution networks with high-penetration photovoltaic (PV) power, after a system failure, distributed generation sources and nearby loads may form power islands. In this case, the islanded network will find it difficult to maintain synchronization with the main grid, and the phase angle difference between them will occur anywhere between 0 and 360°. If reclosing is attempted at this time, the conditions for synchronous reclosing are difficult to meet, and asynchronous reclosing will bring large inrush currents and transient overvoltages, causing significant damage to the generating units and grid equipment. When the islanding detection and disconnection time of a PV power station is long, it causes abnormalities in the timing coordination of automatic transfer switch (ATS) operations, resulting in excessively long ATS times or even failures. Therefore, when a distribution network connected to distributed generation experiences a failure, it can easily lead to local grid islanding, affecting the reliable operation of regional grid reclosing and ATS. More seriously, in islanded operation, abnormal energization of equipment may even endanger the lives of maintenance personnel.

[0053] Active detection methods have been widely studied and applied due to their high accuracy and small blind zone. However, due to the diverse operating conditions of microgrids and the varying types of distributed power sources, grid structures, and load compositions, a single method is currently insufficient to guarantee the accuracy and speed of active detection for all isolated microgrids. Currently, islanding detection methods mainly include communication-based methods, passive detection methods, and active detection methods. The former is highly dependent on communication channels; passive detection methods are simple to implement and have little impact on power quality, but they have blind zones; active detection methods mostly establish positive feedback loops based on the positive feedback relationship between reactive current and frequency, causing the microgrid converter frequency to rapidly change in one direction after voltage loss to achieve islanding detection, promising good reliability, but currently, most methods use a single criterion. In fact, microgrids have complex structures and significant operational variations; islanding detection methods based on a single criterion often cannot fully cover various operating conditions. Therefore, it is necessary to research comprehensive judgment methods based on multiple information sources to minimize the coverage blind zones of each method. Therefore, conducting research on anti-islanding detection in active distribution networks is particularly important for ensuring the reliability of distribution networks including distributed power sources such as photovoltaics and for protecting the safety of operation and maintenance workers.

[0054] The above analysis demonstrates that a thorough investigation into the impact of distributed generation on distribution network relay protection and improvement strategies is urgently needed. In particular, the integration of distributed generation such as photovoltaic (PV) power into the distribution system alters the network structure and power flow distribution, impacting the relay protection of the distribution system. When the PV capacity and location are fixed, the impact of distribution network faults on electrical characteristic quantities may render protection criteria ineffective, potentially leading to protection failure. Therefore, based on protection system schemes adapted to high-penetration PV integration into distribution networks, it is imperative to achieve refined operational logic modeling between protection systems in different areas of the distribution network and between distribution network protection and distributed generation protection, and to propose superior protection coordination strategies.

[0055] In view of the above problems, the present invention proposes a distribution network protection method, system, equipment and storage medium adapted to photovoltaic access.

[0056] Reference Figure 1 , Figure 1 This is a schematic diagram of the structure of a distribution network protection device adapted to photovoltaic access in the hardware operating environment of the embodiment of the present invention.

[0057] like Figure 1As shown, the distribution network protection device adapted for photovoltaic access may include: a processor 1001, such as a central processing unit (CPU), a communication bus 1002, a user interface 1003, a network interface 1004, and a memory 1005. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen, and optionally, it may also include a standard wired interface or a wireless interface. In this invention, the wired interface of the user interface 1003 may be a USB interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be a high-speed random access memory (RAM) or a non-volatile memory (NVM), such as a disk storage device. The memory 1005 may also optionally be a storage device independent of the aforementioned processor 1001.

[0058] Those skilled in the art will understand that Figure 1 The structure shown does not constitute a limitation on distribution network protection equipment adapted to photovoltaic access, and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0059] like Figure 1 As shown, the memory 1005, which serves as a computer storage medium, may include an operating system, a network communication module, a user interface module, and a distribution network protection program adapted to photovoltaic access.

[0060] exist Figure 1 In the photovoltaic-adapted distribution network protection device shown, the network interface 1004 is mainly used to connect to the backend server and communicate data with the backend server; the user interface 1003 is mainly used to connect to user equipment; the photovoltaic-adapted distribution network protection device calls the photovoltaic-adapted distribution network protection program stored in the memory 1005 through the processor 1001 and executes the photovoltaic-adapted distribution network protection method provided in this embodiment of the invention.

[0061] Based on the above hardware structure, an embodiment of the distribution network protection method adapted to photovoltaic access of the present invention is proposed.

[0062] Reference Figure 2 , Figure 2This is a flowchart illustrating a first embodiment of the distribution network protection method adapted to photovoltaic (PV) access according to the present invention. The first embodiment of the distribution network protection method adapted to PV access includes the following steps:

[0063] Step S10: Establish a simplified model of the distribution network based on the type, capacity, and location of distributed power sources in the distribution network.

[0064] Step S20: Analyze the simplified model according to the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network.

[0065] Step S30: In a preset application scenario, the distribution network is simulated and tested using the initial relay protection model to obtain electromechanical transient simulation results.

[0066] Step S40: Optimize the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model.

[0067] Step S50: Monitor the operation of the power distribution network and obtain the current status information of the power distribution network.

[0068] Step S60: Analyze the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network.

[0069] It should be noted that the execution subject of this embodiment is the distribution network protection device adapted to photovoltaic access. The distribution network protection device adapted to photovoltaic access can be an electronic device such as a personal computer or a server, and this embodiment does not limit it.

[0070] For example, the process of establishing a simplified model of the distribution network based on the type, capacity, and location of distributed generation sources in the distribution network may include: establishing a protection configuration model of the distributed generation sources with preset access capacity and location based on the fault characteristics and bidirectional power flow of the distributed generation sources; and simplifying the protection configuration model of the distributed generation sources based on the control characteristics of power electronic equipment to obtain a simplified model of the distribution network. In one example, by studying the typical forms and characteristics of hybrid active distribution networks formed after new energy sources (photovoltaics, energy storage, etc.) are connected to the grid in a preset interface manner, a protection configuration model of distributed generation sources is established to analyze the operating characteristics and fault propagation characteristics of distributed generation sources under DC and AC side network faults (disturbances). New energy sources include, but are not limited to, photovoltaics, wind turbines, and energy storage. This embodiment uses photovoltaics as the new energy source and a distribution network containing distributed generation sources (a distribution network adapted to photovoltaic access) as an example for illustration.

[0071] Specifically, considering the fault characteristics and bidirectional power flow effects of distributed power sources such as photovoltaics, this paper proposes protection configuration schemes and principles for distributed power sources with different access capacities and locations. It also analyzes the coordination and cooperation methods between existing protection and distributed power source grid-connected protection, and formulates corresponding protection setting principles and technical specifications to ensure that the protection device based on the target relay protection model can operate reliably and sensitively when performing relay protection on the distribution network.

[0072] It should be noted that in the study of grid fault characteristics involving distributed generation, distributed generation is generally regarded as a constant current source, or equivalent to a voltage source with internal impedance in a Thevenin circuit. These analytical methods do not fully consider the influence of the complex fault current characteristics of distributed generation under different fault conditions, leading to discrepancies between the proposed grid fault analysis methods and results and the actual situation, thus exhibiting certain limitations. Photovoltaic, wind power, and energy storage distributed generation generally connect to the grid via converters, which employ a dual closed-loop decoupling control strategy with an outer voltage loop and an inner current loop. The outer voltage loop tracks the given voltage value in real time and obtains the active and reactive current components through decoupling formulas, while the inner current loop constantly tracks the obtained active and reactive current components, thereby controlling the active and reactive power output of the photovoltaic power source. However, compared to normal operating conditions, when an asymmetrical fault occurs in a transmission line, the point of common coupling voltage may generate zero and negative sequence components, affecting the three-phase symmetry of the inverter output voltage. The low-voltage ride-through control strategy for photovoltaic power generation systems is a control method based on positive sequence components, avoiding the zero and negative sequence components generated by traditional control strategies, and providing reactive power support to the distribution network. Since the fault duration is generally short, and the changes in ambient temperature and light intensity are minimal during the fault phase, it is generally assumed that the maximum power obtained during the fault period remains essentially unchanged.

[0073] For example, the process of analyzing the simplified model based on the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network may include: obtaining the preset fault type of the current line protection mode; wherein, the current line protection mode includes a three-stage current protection mode and a differential protection mode; generating preset fault conditions based on the false / failure risk and mechanism of the protection criterion under the preset fault type in the preset access distribution network scenario; proposing new relay protection criteria and new schemes based on the preset fault conditions to analyze the simplified model and obtain the initial relay protection model of the distribution network.

[0074] Specifically, this study investigates the erroneous / failure risks and mechanisms of line protection (three-stage current protection, differential protection, etc.) in high-penetration photovoltaic-connected distribution networks under various fault types, including grid-connected, islanded, PQ control, Vf control, VSG control, and low-voltage ride-through conditions, for converters using photovoltaic and other new energy components. The analysis results, i.e., preset fault conditions, are generated. Based on these analysis results, improved protection criteria and schemes are proposed, thus obtaining the initial relay protection model. Understandably, this approach simplifies fault modeling methods while preserving the control characteristics of power electronic equipment. It comprehensively considers factors such as the type, location, and short-circuit capacity of distribution network faults. By analyzing the operating mechanism of photovoltaic and other new energy power generation equipment during fault ride-through, the changing patterns and mutual influences of major electrical quantities, and the contribution of renewable energy grid-connected control strategies to the magnitude of short-circuit current, the accuracy and algorithm feasibility of the lumped parameter model for renewable energy grid-connected line protection are determined. Subsequently, the analysis results are obtained by studying the risk and mechanism of false / failed operation of line protection (three-stage current protection, differential protection, etc.) protection criteria in typical scenarios of distributed power source access to distribution network.

[0075] For example, the process of simulating and verifying the distribution network using the initial relay protection model in a preset application scenario to obtain electromechanical transient simulation results may include: obtaining a protection setting calculation model for distributed power source access to the distribution network under preset operating conditions; analyzing the setting and adaptability of the initial relay protection model under a preset operating mode in the preset application scenario based on the protection setting calculation model to obtain the electromechanical transient simulation results; wherein, the electromechanical transient simulation results include online setting under the preset operating mode and the adaptive protection performance of the relay protection device.

[0076] Specifically, this study investigates the risk and mechanism of erroneous / failure-to-operate protection criteria for line protection (three-stage current protection, differential protection, etc.) in high-penetration photovoltaic (PV) distribution network scenarios under different fault types. Based on the analysis results, improved protection criteria and schemes are proposed, thus obtaining the initial relay protection model. Simulation tests are then conducted in typical application scenarios to verify the protection principle and scheme of the initial relay protection model. Based on the implementation method of the protection configuration scheme for high-penetration PV distribution networks (initial relay protection model), the setting of settings and the adaptability of relay protection devices under complex and variable operating conditions are analyzed. Based on the above analysis, the relay protection setting principles for high-penetration distributed PV distribution networks are derived.

[0077] For example, the process of optimizing the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model may include: constructing a target relay protection model based on multi-terminal current amplitude comparison by utilizing the magnitude relationship between the current at both ends and the comprehensive load current amplitude under normal operation and internal and external fault conditions, based on the electromechanical transient simulation results.

[0078] Specifically, this study analyzes the risk and mechanism of false / failure risks of line protection (three-stage current protection, differential protection, etc.) in typical scenarios of distributed power source access to distribution networks. Based on the above analysis results, a new protection criterion based on multi-terminal current amplitude comparison is constructed by utilizing the different magnitude relationships between the current at both ends and the comprehensive load current amplitude under normal operation and fault conditions inside and outside the zone. This new criterion can accurately distinguish the fault occurrence area and realize a new type of unit-based protection function that does not rely on synchronous measurement.

[0079] For example, the operation of the distribution network is monitored to obtain its current state information. In one example, the operation of the distribution network power system is monitored, and the amplitude and phase information of the three-phase voltage, current, and zero-sequence current are acquired periodically to calculate the amplitude and phase information of the positive and negative zero-sequence components. The current state information includes, but is not limited to, the amplitude and phase information of the positive and negative zero-sequence components. This disclosure does not limit the scope of the current state information.

[0080] For example, the current state information is analyzed based on the target relay protection model to determine whether to perform relay protection on the distribution network. For example, the amplitude and phase information of real-time three-phase voltage and current are used as input features of the target relay protection model to analyze whether the distribution network is faulty, or to analyze the specific fault type and / or fault area of ​​the distribution network, to determine whether to perform relay protection on the distribution network. In this embodiment, distributed power sources such as solar photovoltaic power generation and wind power generation are connected to the microgrid through power electronic devices. The target relay protection model can realize single-level differential protection for distribution network lines with different access capacities and locations of distributed photovoltaic power generation, thereby avoiding the problems of easy false tripping or failure to trip when protecting and reclosing according to existing protection configurations and settings, and improving the operational stability of distributed power sources after they are connected to the distribution network. This research aims to meet the future power grid development trends of high-penetration photovoltaic (PV) power integration and increasingly prominent power electronics characteristics. Focusing on power grid relay protection and control, it investigates the adaptability of existing protection systems in distribution networks with distributed power sources such as PV. It develops new principles for rapid line protection that fully exploit the transient characteristics of faults in the time and frequency domains, comprehensively constructing a security defense system for complex power systems with distributed power source integration in the future, and promoting the integration of distributed renewable energy sources into distribution networks. Establishing and improving the basic theories and key technologies for effectively mitigating the risks of PV integration into distribution networks, and continuously enhancing relay protection technology, will help solve the challenges of distributed power source integration into the power grid.

[0081] It should be noted that the distribution network includes systems with a neutral point that are not effectively grounded. The distribution network may also include 24kV neutral-grounded power grids.

[0082] In this embodiment, a simplified model of the distribution network is established based on the type, capacity, and location of distributed power sources. The simplified model is analyzed according to preset fault conditions of the distribution network to obtain an initial relay protection model. The distribution network is then simulated and tested using the initial relay protection model in a preset application scenario to obtain electromechanical transient simulation results. The initial relay protection model is optimized based on the electromechanical transient simulation results to obtain a target relay protection model. The operation of the distribution network is monitored to obtain its current state information. The current state information is analyzed based on the target relay protection model to determine whether to perform relay protection on the distribution network. This embodiment protects the distribution network using the optimized target relay protection model during monitoring, ensuring reliable and sensitive relay protection, thereby improving the operational stability of distributed power sources after they are connected to the distribution network. This solves the technical problem of insufficient current relay protection methods after distributed power sources are connected to the distribution network, which leads to reduced reliability of the distribution network operation.

[0083] Reference Figure 3 , Figure 3This is a flowchart illustrating the second embodiment of the distribution network protection method adapted to photovoltaic access of the present invention, based on the above. Figure 2 The first embodiment shown presents a second embodiment of the distribution network protection method adapted to photovoltaic access of the present invention.

[0084] In the second embodiment, step S30 includes:

[0085] Step S301: Obtain the protection setting calculation model for distributed power source access to the distribution network under preset operating conditions.

[0086] Step S302: Based on the protection setting calculation model, analyze the setting setting under the preset operating mode and the adaptability of the initial relay protection model in the preset application scenario to obtain the electromechanical transient simulation results; wherein, the electromechanical transient simulation results include the online setting setting under the preset operating mode and the adaptive protection performance of the relay protection device.

[0087] Step S40 includes:

[0088] Step S401: Based on the electromechanical transient simulation results, and utilizing the magnitude relationship between the current at both ends and the comprehensive load current amplitude under normal operation and fault conditions inside and outside the zone, construct a target relay protection model based on multi-terminal current amplitude comparison.

[0089] It should be noted that current protection and longitudinal current differential protection methods are conventional line protection methods in distribution networks. However, most distributed generation (DG) systems currently output DC and then invert it to AC before connecting to the distribution network. Therefore, the polymorphism of fault currents in inverter-type DG directly affects the construction of the distribution network's protection system. Protection designed based on the fault characteristics of inverter-type DG can better meet the requirements for safe operation of the power grid. The current-carrying capacity of power electronics in inverters is limited; therefore, the fault current characteristics of inverter-type DG differ from those of synchronous generators. The former exhibits "polymorphism" and is influenced by many factors. From the perspective of relay protection, the following three aspects need to be considered when constructing a protection system for a distribution network containing inverter-type DG.

[0090] Firstly, the protection setting values ​​need to be determined based on the maximum short-circuit current of the inverter-type distributed power source. Traditional extreme methods based on synchronous generator fault models tend to overestimate the maximum fault current amplitude that the inverter-type distributed power source can provide, potentially leading to a narrowing of the protection range. Because of near-end faults, IGBTs are shut down to prevent damage to power electronic devices, resulting in a reduced fault current. Generally, the fault current of an inverter-type distributed power source is smaller than that of a traditional synchronous generator, primarily depending on the current-carrying capacity of its internal power electronic devices. These factors need to be considered in the setting calculations of protection schemes based on target relay protection models using multi-terminal current amplitude comparison.

[0091] Secondly, the protection scheme (target relay protection model based on multi-terminal current amplitude comparison) should include strategies to address the "polymorphic" characteristics of fault currents. The short-circuit current provided by inverter-type distributed power sources exhibits "polymorphic" characteristics, especially after the power electronic device protection operates, the short-circuit current amplitude decays drastically, with its steady-state value almost reaching zero. Without intervention, current protection may fail to operate. Therefore, the protection scheme based on the target relay protection model using multi-terminal current amplitude comparison should adaptively adopt countermeasures according to changes in the power source fault characteristics to ensure reliable fault clearing.

[0092] Thirdly, the control characteristics of distributed generation (DG) give the distribution network it is connected to complex nonlinear features. Fault analysis methods, such as symmetric classification methods applicable to linear systems, cannot objectively reflect the transient characteristics of active distribution networks with DG integration. In this embodiment, protection under high DG penetration conditions is triggered from two perspectives: grid connection point protection and distribution network protection, involving three levels: "point," "line," and "surface." The protection scheme based on the target relay protection model of multi-terminal current amplitude comparison meets the requirements of relay protection principles and technologies, and the grid connection point protection can also meet the requirements of microgrid distributed autonomy and flexible interaction with the distribution network.

[0093] For example, based on a protection setting calculation model applicable to distributed power generation access to distribution networks under different operating conditions, a power flow calculation section is formed by inputting conventional parameters such as photovoltaic and upstream power sources. Based on electromechanical transient simulation results, online setting of protection values ​​under complex and variable operating modes and adaptive protection functions of relay protection devices are achieved. This ensures that the online setting results are coordinated with distributed power generation control strategies, grid-connected or independent operating conditions, and distributed or centralized access methods. Simultaneously, online verification of the settings for adaptive protection based on improved line protection principles is completed by updating real-time data parameters, actual control strategies, and real-time distribution network topology. Based on the above work, and aiming to balance the safety of distributed renewable energy sources with system reliability and the coordination of transmission line protection configuration and setting, principles and technical specifications for distribution network relay protection setting including distributed power sources are formulated. This provides important standardized support for the standardized grid connection of distributed power sources and the active management and control of distribution networks.

[0094] It should be noted that the following example can be used in this embodiment to implement online setting of complex and variable operating modes and adaptive protection function of relay protection device.

[0095] In one example, adaptive protection adjusts its settings online based on local electrical information. It can modify the online settings according to changes in system operating mode, fault type, and load, thereby expanding the protection range and improving selectivity. Several setting methods can be employed, such as using a composite sequence network to obtain the current setting value from the voltage and current values ​​detected at the protection installation point; decomposing the fault model to obtain a fault-addition network and using the equivalent potential and equivalent impedance on the back side of the protection installation point to obtain the real-time changing current setting value; considering the distance between the protection installation point and the fault point, multiplying the voltage by a factor, using different voltage factors to make the voltage drop measured at different protection installation points on the same line different, and then acting according to the different voltage drop levels; analyzing the fault component based on the two-phase current difference, which is more sensitive than instantaneous overcurrent protection under different operating modes and fault types; and using a filtering algorithm to analyze the fault component to obtain the real-time setting value, etc.

[0096] In one example, protection is constructed using power frequency fault components. Examples include power frequency fault component distance protection, which utilizes the proportional relationship between the influence of the distributed generation (DG) on the protection's activation and operating values; negative-sequence power frequency fault component protection, where the protection device activates when a negative-sequence fault component is detected, and only operates when the maximum positive-sequence fault component is detected, thus determining the fault range; positive-sequence current fault component directional overcurrent protection, which is activated by overcurrent protection, then calculates the phase angle difference of the filtered positive-sequence current fault components, determines the fault direction, and disconnects the faulty line; and a combination of positive-sequence fault component and longitudinal directional protection, which leverages the characteristic that ring networks with dual-ended power supplies generally operate in an open-loop mode.

[0097] In one example, protection is based on multi-point information technology. This protection utilizes intelligent electronic devices, distributed artificial intelligence technology, multi-agent systems, and communication technologies to classify the protection based on different fault isolation algorithms. Examples include wide-area protection based on overcurrent protection; protection based on the maximum fault characteristic information, which is based on the principle of wide-area protection and uses a communication-supported protection algorithm to determine the fault search direction based on current quantity; protection based on a multi-agent system (MAS), which searches for fault-related sections through cooperation between upper and lower level agents; protection that utilizes the communication functions between each agent and the SCADA system to exchange protection information between different locations and determine the fault section based on the comprehensive results of the information; and protection based on advanced feeder terminal units, which can quickly locate the fault area and isolate the fault.

[0098] Based on the above example, in view of the change in fault current characteristics after the intervention of distributed power sources, a protection method based on traditional power information and multi-point information technology can be adopted. The relay protection method proposed in this embodiment is a significant improvement over the three-stage current protection.

[0099] For example, based on the electromechanical transient simulation results, after constructing a target relay protection model based on multi-terminal current amplitude comparison using the magnitude relationship between the current at both ends and the comprehensive load current amplitude under normal operation and internal / external fault conditions, the method further includes: analyzing the applicability of the target relay protection model based on multi-terminal current amplitude comparison according to the distribution network operating status, fault initial angle, fault type, and grounding impedance value conditions, and determining the discrimination dead zone of the target relay protection model based on multi-terminal current amplitude comparison. Analyzing the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network includes: when the analysis of the current state information determines that the fault point is located in the discrimination dead zone, using a three-stage overcurrent protection method with direction determination function, an instantaneous overcurrent protection method, and the target relay protection model to construct a target protection scheme; and performing relay protection on the distribution network according to the target protection scheme.

[0100] Specifically, by changing conditions such as distribution network operating status, fault initial angle, fault type, and grounding impedance value, the applicability range of the proposed new protection criterion based on multi-terminal current amplitude comparison is examined, thereby determining the dead zone for minor and special faults within the zone. When the fault point falls within this dead zone, the existing three-stage overcurrent protection with directional judgment function can still serve as backup protection, cooperating with the proposed new principle protection and existing overcurrent instantaneous trip protection. While the current modulus differential criterion determines that the fault is located within the zone, a single-stage differential accelerated protection scheme is formed by communicating with adjacent line protection units. Simultaneously, based on the control strategy and mode switching method for renewable energy grid-connected and independent operation conditions, the impact of control strategy switching on system impedance characteristics and output short-circuit current is analyzed, and the adaptability of the improved protection criterion for distribution networks containing distributed power sources under different operating conditions is studied.

[0101] This embodiment protects the distribution network by using an optimized target relay protection model when monitoring the distribution network, ensuring reliable and sensitive relay protection, thereby improving the operational stability of distributed power sources after they are connected to the distribution network. It solves the technical problem that the current relay protection method is insufficient after distributed power sources are connected to the distribution network, resulting in reduced operational reliability of the distribution network.

[0102] Furthermore, this embodiment of the invention also proposes a storage medium storing a distribution network protection program adapted to photovoltaic access. When the distribution network protection program adapted to photovoltaic access is executed by a processor, it implements the steps of the distribution network protection method adapted to photovoltaic access described above.

[0103] Since this storage medium adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0104] In addition, refer to Figure 4 This invention also proposes a distribution network protection system adapted to photovoltaic (PV) grid integration, the distribution network protection system adapted to PV grid integration comprising:

[0105] Module 10 is used to establish a simplified model of the distribution network based on the type, capacity, and location of distributed power sources in the distribution network.

[0106] Analysis module 20 is used to analyze the simplified model according to the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network.

[0107] Simulation module 30 is used to perform simulation testing and verification of the distribution network in a preset application scenario using the initial relay protection model, so as to obtain electromechanical transient simulation results;

[0108] Optimization module 40 is used to optimize the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model;

[0109] The monitoring module 50 is used to monitor the operation of the power distribution network and obtain the current status information of the power distribution network.

[0110] The judgment module 60 is used to analyze the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network.

[0111] For example, the process of establishing a simplified model of the distribution network based on the type, capacity, and location of distributed generation sources in the distribution network may include: establishing a protection configuration model of the distributed generation sources with preset access capacity and location based on the fault characteristics and bidirectional power flow of the distributed generation sources; and simplifying the protection configuration model of the distributed generation sources based on the control characteristics of power electronic equipment to obtain a simplified model of the distribution network. In one example, by studying the typical forms and characteristics of hybrid active distribution networks formed after new energy sources (photovoltaics, energy storage, etc.) are connected to the grid in a preset interface manner, a protection configuration model of distributed generation sources is established to analyze the operating characteristics and fault propagation characteristics of distributed generation sources under DC and AC side network faults (disturbances). New energy sources include, but are not limited to, photovoltaics, wind turbines, and energy storage. This embodiment uses photovoltaics as the new energy source and a distribution network containing distributed generation sources (a distribution network adapted to photovoltaic access) as an example for illustration.

[0112] Specifically, considering the fault characteristics and bidirectional power flow effects of distributed power sources such as photovoltaics, this paper proposes protection configuration schemes and principles for distributed power sources with different access capacities and locations. It also analyzes the coordination and cooperation methods between existing protection and distributed power source grid-connected protection, and formulates corresponding protection setting principles and technical specifications to ensure that the protection device based on the target relay protection model can operate reliably and sensitively when performing relay protection on the distribution network.

[0113] It should be noted that in the study of grid fault characteristics involving distributed generation, distributed generation is generally regarded as a constant current source, or equivalent to a voltage source with internal impedance in a Thevenin circuit. These analytical methods do not fully consider the influence of the complex fault current characteristics of distributed generation under different fault conditions, leading to discrepancies between the proposed grid fault analysis methods and results and the actual situation, thus exhibiting certain limitations. Photovoltaic, wind power, and energy storage distributed generation generally connect to the grid via converters, which employ a dual closed-loop decoupling control strategy with an outer voltage loop and an inner current loop. The outer voltage loop tracks the given voltage value in real time and obtains the active and reactive current components through decoupling formulas, while the inner current loop constantly tracks the obtained active and reactive current components, thereby controlling the active and reactive power output of the photovoltaic power source. However, compared to normal operating conditions, when an asymmetrical fault occurs in a transmission line, the point of common coupling voltage may generate zero and negative sequence components, affecting the three-phase symmetry of the inverter output voltage. The low-voltage ride-through control strategy for photovoltaic power generation systems is a control method based on positive sequence components, avoiding the zero and negative sequence components generated by traditional control strategies, and providing reactive power support to the distribution network. Since the fault duration is generally short, and the changes in ambient temperature and light intensity are minimal during the fault phase, it is generally assumed that the maximum power obtained during the fault period remains essentially unchanged.

[0114] For example, the process of analyzing the simplified model based on the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network may include: obtaining the preset fault type of the current line protection mode; wherein, the current line protection mode includes a three-stage current protection mode and a differential protection mode; generating preset fault conditions based on the false / failure risk and mechanism of the protection criterion under the preset fault type in the preset access distribution network scenario; proposing new relay protection criteria and new schemes based on the preset fault conditions to analyze the simplified model and obtain the initial relay protection model of the distribution network.

[0115] Specifically, this study investigates the erroneous / failure risks and mechanisms of line protection (three-stage current protection, differential protection, etc.) in high-penetration photovoltaic-connected distribution networks under various fault types, including grid-connected, islanded, PQ control, Vf control, VSG control, and low-voltage ride-through conditions, for converters using photovoltaic and other new energy components. The analysis results, i.e., preset fault conditions, are generated. Based on these analysis results, improved protection criteria and schemes are proposed, thus obtaining the initial relay protection model. Understandably, this approach simplifies fault modeling methods while preserving the control characteristics of power electronic equipment. It comprehensively considers factors such as the type, location, and short-circuit capacity of distribution network faults. By analyzing the operating mechanism of photovoltaic and other new energy power generation equipment during fault ride-through, the changing patterns and mutual influences of major electrical quantities, and the contribution of renewable energy grid-connected control strategies to the magnitude of short-circuit current, the accuracy and algorithm feasibility of the lumped parameter model for renewable energy grid-connected line protection are determined. Subsequently, the analysis results are obtained by studying the risk and mechanism of false / failed operation of line protection (three-stage current protection, differential protection, etc.) protection criteria in typical scenarios of distributed power source access to distribution network.

[0116] For example, the process of simulating and verifying the distribution network using the initial relay protection model in a preset application scenario to obtain electromechanical transient simulation results may include: obtaining a protection setting calculation model for distributed power source access to the distribution network under preset operating conditions; analyzing the setting and adaptability of the initial relay protection model under a preset operating mode in the preset application scenario based on the protection setting calculation model to obtain the electromechanical transient simulation results; wherein, the electromechanical transient simulation results include online setting under the preset operating mode and the adaptive protection performance of the relay protection device.

[0117] Specifically, this study investigates the risk and mechanism of erroneous / failure-to-operate protection criteria for line protection (three-stage current protection, differential protection, etc.) in high-penetration photovoltaic (PV) distribution network scenarios under different fault types. Based on the analysis results, improved protection criteria and schemes are proposed, thus obtaining the initial relay protection model. Simulation tests are then conducted in typical application scenarios to verify the protection principle and scheme of the initial relay protection model. Based on the implementation method of the protection configuration scheme for high-penetration PV distribution networks (initial relay protection model), the setting of settings and the adaptability of relay protection devices under complex and variable operating conditions are analyzed. Based on the above analysis, the relay protection setting principles for high-penetration distributed PV distribution networks are derived.

[0118] For example, the process of optimizing the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model may include: constructing a target relay protection model based on multi-terminal current amplitude comparison by utilizing the magnitude relationship between the current at both ends and the comprehensive load current amplitude under normal operation and internal and external fault conditions, based on the electromechanical transient simulation results.

[0119] Specifically, this study analyzes the risk and mechanism of false / failure risks of line protection (three-stage current protection, differential protection, etc.) in typical scenarios of distributed power source access to distribution networks. Based on the above analysis results, a new protection criterion based on multi-terminal current amplitude comparison is constructed by utilizing the different magnitude relationships between the current at both ends and the comprehensive load current amplitude under normal operation and fault conditions inside and outside the zone. This new criterion can accurately distinguish the fault occurrence area and realize a new type of unit-based protection function that does not rely on synchronous measurement.

[0120] For example, the operation of the distribution network is monitored to obtain its current state information. In one example, the operation of the distribution network power system is monitored, and the amplitude and phase information of the three-phase voltage, current, and zero-sequence current are acquired periodically to calculate the amplitude and phase information of the positive and negative zero-sequence components. The current state information includes, but is not limited to, the amplitude and phase information of the positive and negative zero-sequence components. This disclosure does not limit the scope of the current state information.

[0121] For example, the current state information is analyzed based on the target relay protection model to determine whether to perform relay protection on the distribution network. For example, the amplitude and phase information of real-time three-phase voltage and current are used as input features of the target relay protection model to analyze whether the distribution network is faulty, or to analyze the specific fault type and / or fault area of ​​the distribution network, to determine whether to perform relay protection on the distribution network. In this embodiment, distributed power sources such as solar photovoltaic power generation and wind power generation are connected to the microgrid through power electronic devices. The target relay protection model can realize single-level differential protection for distribution network lines with different access capacities and locations of distributed photovoltaic power generation, thereby avoiding the problems of easy false tripping or failure to trip when protecting and reclosing according to existing protection configurations and settings, and improving the operational stability of distributed power sources after they are connected to the distribution network. This research aims to meet the future power grid development trends of high-penetration photovoltaic (PV) power integration and increasingly prominent power electronics characteristics. Focusing on power grid relay protection and control, it investigates the adaptability of existing protection systems in distribution networks with distributed power sources such as PV. It develops new principles for rapid line protection that fully exploit the transient characteristics of faults in the time and frequency domains, comprehensively constructing a security defense system for complex power systems with distributed power source integration in the future, and promoting the integration of distributed renewable energy sources into distribution networks. Establishing and improving the basic theories and key technologies for effectively mitigating the risks of PV integration into distribution networks, and continuously enhancing relay protection technology, will help solve the challenges of distributed power source integration into the power grid.

[0122] It should be noted that the distribution network includes systems with a neutral point that are not effectively grounded. The distribution network may also include 24kV neutral-grounded power grids.

[0123] This embodiment proposes a distribution network protection system adapted to photovoltaic (PV) access. The system includes: a modeling module 10 for establishing a simplified model of the distribution network based on the type, capacity, and location of distributed power sources; an analysis module 20 for analyzing the simplified model according to preset fault conditions of the distribution network to obtain an initial relay protection model; a simulation module 30 for performing simulation tests on the distribution network using the initial relay protection model in preset application scenarios to obtain electromechanical transient simulation results; an optimization module 40 for optimizing the initial relay protection model based on the electromechanical transient simulation results to obtain a target relay protection model; a monitoring module 50 for monitoring the operation of the distribution network and obtaining its current state information; and a judgment module 60 for analyzing the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network. This embodiment protects the distribution network by using an optimized target relay protection model when monitoring the distribution network, ensuring reliable and sensitive relay protection, thereby improving the operational stability of distributed power sources after they are connected to the distribution network. It solves the technical problem that the current relay protection method is insufficient after distributed power sources are connected to the distribution network, resulting in reduced operational reliability of the distribution network.

[0124] Other embodiments or specific implementations of the distribution network protection system adapted to photovoltaic access described in this invention can be referred to the above-described method embodiments, and will not be repeated here.

[0125] It should be understood that the above are merely illustrative examples and do not constitute any limitation on the technical solutions of the present invention. In specific applications, those skilled in the art can make settings as needed, and the present invention does not impose any restrictions on this.

[0126] It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of this invention. In practical applications, those skilled in the art can select some or all of the workflow to achieve the purpose of this embodiment according to actual needs, and no restrictions are imposed here.

[0127] In addition, for technical details not described in detail in this embodiment, please refer to the image reconstruction method applied to the electrical impedance imaging system as described above provided in any embodiment of the present invention, which will not be repeated here.

[0128] Furthermore, it should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0129] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0130] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as read-only memory (ROM) / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0131] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A distribution network protection method adapted to photovoltaic access, characterized in that, The distribution network protection method adapted to photovoltaic access includes: A simplified model of the distribution network is established based on the type, capacity, and location of distributed power sources in the distribution network; The simplified model is analyzed based on the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network. In a preset application scenario, the distribution network is simulated and tested using the initial relay protection model to obtain electromechanical transient simulation results. The initial relay protection model is optimized based on the electromechanical transient simulation results to obtain the target relay protection model; Monitor the operation of the power distribution network and obtain its current status information; The current state information is analyzed based on the target relay protection model to determine whether to perform relay protection on the distribution network. A simplified model of the distribution network is established based on the type, capacity, and location of distributed generation sources in the distribution network, including: establishing a protection configuration model of the distributed generation sources with preset access capacity and location based on the fault characteristics and bidirectional power flow of the distributed generation sources; and simplifying the protection configuration model of the distributed generation sources based on the control characteristics of power electronic equipment to obtain a simplified model of the distribution network. The simplified model is analyzed based on the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network. This includes: obtaining the preset fault types of the current line protection mode; wherein the current line protection mode includes a three-stage current protection mode and a differential protection mode; generating preset fault conditions based on the false / failure risk and mechanism of the protection criterion under the preset fault type in the preset access distribution network scenario; and proposing new relay protection criteria and new schemes based on the preset fault conditions to analyze the simplified model and obtain the initial relay protection model of the distribution network. In a preset application scenario, the distribution network is simulated and tested using the initial relay protection model to obtain electromechanical transient simulation results. This includes: obtaining a protection setting calculation model for distributed power sources connected to the distribution network under preset operating conditions; analyzing the setting and adaptability of the initial relay protection model under a preset operating mode in the preset application scenario based on the protection setting calculation model to obtain the electromechanical transient simulation results; wherein, the electromechanical transient simulation results include online setting and adaptive protection performance of the relay protection device under the preset operating mode.

2. The distribution network protection method adapted to photovoltaic access as described in claim 1, characterized in that, The step of optimizing the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model includes: constructing a target relay protection model based on multi-terminal current amplitude comparison by utilizing the magnitude relationship between the current at both ends and the comprehensive load current amplitude under normal operation and internal and external fault conditions, based on the electromechanical transient simulation results.

3. The distribution network protection method adapted to photovoltaic access as described in claim 2, characterized in that, After constructing a target relay protection model based on multi-terminal current amplitude comparison using the magnitude relationship between the current at both ends and the comprehensive load current amplitude under normal operation and internal and external fault conditions, based on the electromechanical transient simulation results, the method further includes: analyzing the applicability of the target relay protection model based on multi-terminal current amplitude comparison according to the distribution network operation status, fault initial angle, fault type and grounding impedance value conditions, and determining the discrimination dead zone of the target relay protection model based on multi-terminal current amplitude comparison.

4. The distribution network protection method adapted to photovoltaic access as described in claim 3, characterized in that, The step of analyzing the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network includes: when the analysis of the current state information determines that the fault point is located in the discrimination dead zone, a target protection scheme is constructed by using a three-stage overcurrent protection mode with direction determination function, an overcurrent instantaneous overcurrent protection mode, and the target relay protection model. The distribution network is subjected to relay protection according to the target protection scheme.

5. A distribution network protection system adapted to photovoltaic access based on the method of any one of claims 1 to 4, characterized in that, The distribution network protection system adapted to photovoltaic access includes: a modeling module, used to establish a simplified model of the distribution network based on the type, capacity, and location of distributed power sources in the distribution network; An analysis module is used to analyze the simplified model based on the preset fault conditions of the distribution network to obtain the initial relay protection model of the distribution network. The simulation module is used to perform simulation tests and verifications on the distribution network in a preset application scenario using the initial relay protection model, so as to obtain electromechanical transient simulation results. The optimization module is used to optimize the initial relay protection model based on the electromechanical transient simulation results to obtain the target relay protection model; The monitoring module is used to monitor the operation of the power distribution network and obtain the current status information of the power distribution network. The judgment module is used to analyze the current state information based on the target relay protection model to determine whether to perform relay protection on the distribution network.

6. A distribution network protection device adapted to photovoltaic access, characterized in that, The distribution network protection device adapted to photovoltaic access includes: a memory, a processor, and a program stored in the memory and executable on the processor. When the program is executed by the processor, it implements the steps of the distribution network protection method adapted to photovoltaic access as described in any one of claims 1 to 4.

7. A storage medium, characterized in that, The storage medium stores a distribution network protection program adapted to photovoltaic access, which, when executed by a processor, implements the steps of the distribution network protection method adapted to photovoltaic access as described in any one of claims 1 to 4.

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