A Method and System for Setting Relay Protection Values of Distribution Networks in the Scenario of Grid-connection of Distributed Power Sources

Abstract

The present invention relates to the technical field of distribution network protection and distributed power grid connection, and particularly to a method and system for setting protection values of a distribution network in the scenario of distributed power grid connection. Through a scientific and reasonable scheme for setting protection values of the distribution network, it covers collecting and obtaining basic data, calculating short-circuit current according to the access situation of distributed power sources and the topological structure of the distribution network, determining protection values based on the calculation results of short-circuit current and the principles of setting protection values, and verifying the protection performance, so as to ensure correct operation when a fault occurs; at the same time, reasonably setting protection values to adapt to the characteristics of distributed power sources, ensuring the selectivity and sensitivity of the protection system; by configuring the reclosing function, improving the power supply reliability and fault recovery ability; at the same time, using an automated data collection and protection setting process to adapt to different distribution network topological structures and ensure the stable operation of the power grid under various structures.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network protection and distributed power grid connection, and in particular to a distribution network protection constant value setting method and system in a distributed power grid connection scenario. Background Art

[0002] With the rapid development of renewable energy, especially the large-scale access of distributed power sources such as photovoltaic power generation and wind power generation, the structure and operation mode of the power system have changed significantly. Distributed power sources are directly connected to the distribution network, which changes the power flow distribution and short-circuit current characteristics of the traditional power grid, bringing new challenges to the safe and stable operation of the power system. When dealing with the connection of distributed power sources to the grid, the traditional distribution network protection system may have problems such as protection refusal, false operation, and poor selectivity, which may lead to power grid safety accidents in serious cases. Therefore, how to scientifically and reasonably formulate the distribution network protection setting scheme based on the characteristics of distributed power sources to ensure that the power grid can isolate the fault area in a timely and effective manner when a fault occurs is an important issue facing the current power system.

[0003] The traditional protection setting method of the distribution network is designed based on the traditional grid structure and power flow mode. It is usually assumed that there is a single, stable power source in the grid, and the characteristics of the grid flow, short-circuit current, etc. change little. However, with the grid connection of distributed power sources, the power flow mode and current distribution in the grid have undergone major changes. For example, the access of distributed power sources may cause the amplitude of the fault current to be lower than the short-circuit current caused by the traditional power source when a fault occurs, making it impossible for the protection device to identify and correctly disconnect the fault point, resulting in the risk of protection refusal to operate; on the other hand, the volatility and uncertainty of distributed power sources may also cause false operation, resulting in unnecessary power outages or large-scale power outages. In addition, the change in grid topology after the access of distributed power sources may cause the original protection setting to be unable to meet the needs of the new operation mode, so it is urgent to adjust and optimize the existing protection setting method in a targeted manner.

[0004] In order to solve these problems, a new distribution network protection setting scheme in the scenario of distributed power grid connection is proposed. This scheme considers the impact of distributed power access and combines the operating characteristics of the current power system to develop a set of adaptable and flexible protection setting strategies. First of all, when determining the protection setting, it is necessary to conduct a detailed analysis of the access mode of distributed power sources and evaluate its impact on the power grid flow and short-circuit current characteristics to ensure the selectivity and accuracy of protection when a fault occurs. In addition, in view of the volatility and uncertainty of distributed power sources, the protection setting scheme also needs to have a certain degree of adaptability and be able to dynamically adjust the protection setting to ensure the stable operation of the power grid under different working conditions. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention is proposed.

[0006] Therefore, the technical problems to be solved by the present invention are as follows: Ensure grid security: In the scenario of distributed power grid connection, the setting of protection values should ensure that the grid can quickly and accurately isolate the fault area in case of a fault, preventing the expansion of the fault. Improve power supply reliability: By reasonably setting protection values, reduce the power outage time and scope of non-fault areas, and improve power supply reliability. Adapt to the characteristics of distributed power sources: Considering the output volatility and uncertainty of distributed power sources, formulate a flexible protection value setting strategy. The distribution network protection value setting scheme in the scenario of distributed power grid connection is a systematic project, which needs to comprehensively consider multiple aspects such as the access mode of distributed power sources, impact analysis, protection value setting principles, and special protection measures. Through a scientific and reasonable setting scheme, ensure the safe and stable operation of the grid in the scenario of distributed power grid connection.

[0007] To solve the above technical problems, the present invention provides the following technical solution. A method for setting distribution network protection values in the scenario of distributed power grid connection includes: collecting and obtaining basic data; calculating short-circuit current according to the access situation of distributed power sources and the topological structure of the distribution network; determining protection values according to the calculation results of short-circuit current and protection value setting principles; and verifying the protection performance to ensure correct operation in case of a fault.

[0008] As a preferred scheme of the method for setting distribution network protection values in the scenario of distributed power grid connection according to the present invention, wherein: the basic data includes the capacity, access location of distributed power sources, the topological structure of the distribution network, and line parameters.

[0009] As a preferred scheme of the method for setting distribution network protection values in the scenario of distributed power grid connection according to the present invention, wherein: the access situation of distributed power sources includes the access mode, capacity, access location, and voltage level of distributed power sources;

[0010] Among them, the access mode includes connecting the power source to the substation busbar, converting the power source voltage through a transformer and transmitting it to the distribution network; using a real-time monitoring system to dynamically adjust the power factor and load adaptability of the accessed power source;

[0011] After the access of a large-capacity distributed power source, if the short-circuit current value at the access point increases, then adjust the protection value; after the access of a small-capacity distributed power source, if the short-circuit current value at the access point decreases, then adjust the sensitivity;

[0012] When the distributed power source is connected to the end of the feeder, the fault current increases; when the distributed power source is connected to the core area of the distribution network, the short-circuit current decreases;

[0013] When connected at a high voltage level, the voltage is reduced by a transformer to match the distribution network voltage; when connected at a low voltage level, it is converted by an inverter to match the distribution network voltage.

[0014] As a preferred embodiment of the method for setting relay protection values in a distribution network under the scenario of distributed power grid connection according to the present invention, wherein: the topological structure of the distribution network includes the connection relationship and topological form of distribution network components;

[0015] Among them, the connection relationship includes radial and ring network types; for the radial type, by real-time monitoring of the grid state, using dynamic load regulation and fault tolerance calculation, and through dispatching optimization to ensure automatic adjustment of power supply compliance; for the ring network type, an adaptive grid is formed in combination with the access of distributed power sources. When a fault occurs, the distributed power sources switch to standby paths and automatically adjust the current distribution to reduce the grid restoration time;

[0016] The topological forms include radial structure, ring network structure, and grid structure; in the radial structure, the current flows through a single path; compared with the radial structure, the number of paths in the ring network structure increases; in the grid structure, the current flows through the grid paths; determining the distribution and flow path of the short-circuit current when a fault occurs.

[0017] As a preferred embodiment of the method for setting relay protection values in a distribution network under the scenario of distributed power grid connection according to the present invention, wherein: calculating the short-circuit current includes, based on Ohm's law, combining the impedance of the power system to represent the short-circuit current, expressed as:

[0018] ,

[0019] Among them, represents the short-circuit current, represents the line-to-ground voltage, represents the total impedance between the fault point and the power source;

[0020] Considering the network topology, the short-circuit current is further expanded, expressed as:

[0021] ,

[0022] Among them, represents the short-circuit current adjusted according to the topology, represents the network impedance of the distribution network.

[0023] As a preferred embodiment of the method for setting relay protection values in a distribution network under the scenario of distributed power grid connection according to the present invention, wherein: the principle of setting relay protection values includes three-stage protection, adopting a protection method combining instantaneous overcurrent protection in section I, time-limited overcurrent protection in section II, and definite-time overcurrent protection in section III;

[0024] Input the protection setting values according to the short-circuit current calculation results, and the system provides setting value suggestions based on the calculated current values;

[0025] The setting value of the first-stage protection is set to , when the short-circuit current exceeds the setting value of the first-stage protection, the first-stage protection immediately operates to isolate the fault area; the setting value of the second-stage protection is set to , when the short-circuit current exceeds the setting value of the second-stage protection and does not reach the setting value of the first-stage protection, the second-stage protection operates after the set time for backup protection; the setting value of the third-stage protection is set to , when the short-circuit current is greater than the setting value of the third-stage protection and does not reach the setting value of the second-stage protection, the set time is increased and it operates after the increased set time;

[0026] Dynamically adjust the protection setting values according to the calculated short-circuit current results. If the setting value of the first-stage protection is set to more than 500 A, the system prompts that the setting value of the first-stage protection causes a delayed operation and reduces the setting value of the first-stage protection; if the setting value of the second-stage protection is set to less than 100 A, the system prompts that it does not operate after the set time, resulting in misoperation of cutting off the normal area, and increases the setting value of the second-stage protection; if the setting value of the third-stage protection is set to less than 30 A, the system prompts that the setting value of the third-stage protection causes misoperation and increases the setting value of the third-stage protection.

[0027] As a preferred solution of the method for setting the protection setting values of the distribution network in the scenario of distributed power grid connection according to the present invention, wherein: the verification of the protection performance includes the adjustment of the protection setting values and the verification of the fault recovery and reclosing;

[0028] Among them, the adjustment of the protection setting values includes adjusting the operating setting values of the protection equipment according to the short-circuit current calculation results and the protection setting value setting principles to ensure correct operation in specific fault situations; the reclosing verification includes configuring the reclosing function according to the actual situation of the distribution network and the fault type, verifying the restoration of power supply after disconnecting the fault and checking the effect after reclosing; the fault recovery includes observing the power supply restoration situation after testing the reclosing.

[0029] Another object of the present invention is to provide a system for setting the protection setting values of the distribution network in the scenario of distributed power grid connection, which can automatically collect basic data, calculate the short-circuit current, set the protection setting values, and perform protection performance verification, so as to improve the safety, reliability and fault response ability of the power grid after the distributed power grid connection.

[0030] To solve the above technical problems, the present invention provides the following technical solution: a system for setting the protection setting values of the distribution network in the scenario of distributed power grid connection, including: a data collection module, a current calculation module, a protection setting module, and a performance verification module;

[0031] The data collection module collects and obtains basic data;

[0032] The current calculation module calculates the short-circuit current according to the access situation of distributed power sources and the topological structure of the distribution network;

[0033] The protection setting module determines the protection setting value according to the short-circuit current calculation result and the protection setting principle;

[0034] The performance verification module verifies the protection performance to ensure correct operation during a fault.

[0035] A computer device includes a memory and a processor. The memory stores a computer program. It is characterized in that when the processor executes the computer program, the steps of a method for setting distribution network protection setting values in a distributed power grid connection scenario as described above are implemented.

[0036] A computer-readable storage medium stores a computer program. It is characterized in that when the computer program is executed by a processor, the steps of a method for setting distribution network protection setting values in a distributed power grid connection scenario as described above are implemented.

[0037] The beneficial effects of the present invention: Through a scientific and reasonable distribution network protection setting value setting scheme, the safety and reliability of the power grid can be effectively improved. After the distributed power source is connected to the grid, it can ensure that the power grid can quickly and accurately isolate the fault area and prevent the spread of the fault; reasonably set the protection setting value to adapt to the characteristics of the distributed power source and ensure the selectivity and sensitivity of the protection system; configure the reclosing function to improve the power supply reliability and fault recovery ability of the power grid; at the same time, adopt an automated data collection, short-circuit current calculation and protection setting value setting process, reduce manual intervention, improve work efficiency, and enhance the intelligent level of distribution network protection; finally, adapt to the characteristics of different distribution network topological structures to ensure the stable operation of the power grid under various structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for description in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 It is a flowchart of a method for setting distribution network protection setting values in a distributed power grid connection scenario provided by an embodiment of the present invention.

[0040] Figure 2 It is a schematic diagram of a simulation model of a method for setting distribution network protection setting values in a distributed power grid connection scenario provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0042] Example 1, referring to Figure 1 , which is an embodiment of the present invention. This embodiment provides a method for setting relay protection values in a distribution network under the scenario of distributed power grid connection, including:

[0043] S1: Collect and obtain basic data.

[0044] It should be noted that, as shown in S1 of Figure 1 , the basic data includes the capacity of the distributed power source, the access location, the topological structure of the distribution network, and the line parameters; among them, the capacity of the distributed power source: includes the maximum output capacity of each power source; the access location: the specific location where the power source is connected to the distribution network, which directly affects the flow and distribution of current; the topological structure of the distribution network: includes the structural layout of the network, and each structure has different effects on the current flow and fault response; the line parameters: cover the electrical characteristics such as the resistance and reactance of the wire;

[0045] Furthermore, the analysis of the above basic data not only involves static collection but also includes dynamic monitoring; for example, the real-time output of distributed power sources such as photovoltaic or wind power may fluctuate due to weather conditions, so real-time data is required for more accurate setting of relay protection values.

[0046] Even further, by collecting data through a real-time monitoring system, the protection strategy can be dynamically adjusted to adapt to changing network conditions and the output of distributed power sources; for example, when the output of a large-capacity power source suddenly increases, it may be necessary to adjust the relay protection values to prevent overload.

[0047] Specifically, the collection of data can be achieved through various sensors and intelligent devices, which are installed at key access points and grid nodes; the collected data is transmitted to the central control panel through a high-speed communication network for in-depth analysis and processing.

[0048] S2: Calculate the short-circuit current according to the access situation of the distributed power source and the topological structure of the distribution network.

[0049] It should be noted that, as shown in S2 of Figure 1 , the access situation of the distributed power source includes the access method, capacity, access location, and voltage level of the distributed power source;

[0050] Access mode: The access mode of distributed power sources determines their contribution to the power grid;

[0051] For example, a power source can be connected to the distribution network through a substation busbar, and the voltage is converted by a transformer and then transmitted to the distribution network; the above access mode usually affects the voltage matching between the power source and the distribution network, and further affects the amplitude and characteristics of the short-circuit current; Capacity and access location: The access location has a particularly important impact on the short-circuit current; when a power source is connected to the core area of the distribution network, the short-circuit current decreases, while when a power source is connected to the end of a feeder, the short-circuit current value near the fault point increases; due to different current paths and different output capabilities of the power source, it directly affects the magnitude of the short-circuit current; Voltage level: Different voltage levels also have an impact on the short-circuit current. High-voltage access usually reduces the voltage through a transformer to match the distribution network voltage, while distributed power sources with low-voltage access perform voltage conversion through an inverter; at this time, the conversion efficiency of the inverter or transformer needs to be considered when calculating the short-circuit current;

[0052] Among them, the access mode includes connecting the power source to the substation busbar, converting the power source voltage through a transformer and transmitting it to the distribution network; using a real-time monitoring system to dynamically adjust the power factor and load adaptability of the access power source;

[0053] When a large-capacity distributed power source is connected, the short-circuit current value at the connection point increases, then adjust the protection setting value; when a small-capacity distributed power source is connected, the short-circuit current value at the connection point decreases, then adjust the sensitivity;

[0054] When a distributed power source is connected to the end of a feeder, the fault current increases; when a distributed power source is connected to the core area of the distribution network, the short-circuit current decreases;

[0055] When accessing at a high voltage level, the voltage is reduced through a transformer to match the distribution network voltage; when accessing at a low voltage level, it is converted through an inverter to match the distribution network voltage.

[0056] Furthermore, when calculating the short-circuit current, it is necessary to consider the basic situation of the power source access and introduce a real-time monitoring system to dynamically adjust the load adaptability and power factor of the system; as the power grid load changes, the output characteristics of the power source will also change accordingly;

[0057] Furthermore, the topology of the distribution network has a decisive impact on the calculation of the short-circuit current. The topology of the distribution network defines the current flow path and distribution pattern; the topology of the distribution network includes the connection relationship and topology form of the distribution network components;

[0058] Among them, the connection relationship includes radial and ring network types;

[0059] Radial type: By real-time monitoring of the power grid status, using dynamic load regulation and fault-tolerant calculation, and ensuring automatic adjustment of power supply compliance through dispatching optimization; Ring network type: Combining the access of distributed power sources to form an adaptive grid. When a fault occurs, the distributed power sources switch to standby paths and reduce the power grid restoration time by automatically adjusting the current distribution.

[0060] The topological forms include radial structure, ring network structure, and grid structure.

[0061] Radial structure: The current flows through a single path; when a fault occurs, the current distribution is simple and the short-circuit current calculation is relatively direct; when a fault occurs, the current near the fault point will increase rapidly, and it is necessary to dynamically optimize the current distribution through real-time monitoring and load regulation system.

[0062] Ring network structure: Compared with the radial type, the number of paths in the ring network distribution network increases and the current flow is more complex; when a fault occurs, the current flows along the original path and also through the standby path; at this time, the concept of adaptive grid is particularly important; in the ring network structure, the access of distributed power sources will affect the current flow path and can automatically adjust the current distribution to reduce the power grid restoration time.

[0063] Grid structure: In the grid distribution network, the current flows through multiple paths and the current distribution is the most complex; at this time, the multiple redundancy of the network requires considering all possible paths in the short-circuit current calculation; similar to the ring network structure, the grid structure can be dynamically adjusted according to the real-time current distribution to ensure that the power grid can quickly recover when a fault occurs.

[0064] Furthermore, calculating the short-circuit current includes, based on Ohm's law, combining the impedance of the power system to represent the short-circuit current, expressed as:

[0065] ,

[0066] where, represents the short-circuit current, which represents the intensity of the current in the power grid when a fault occurs, represents the line-to-ground voltage, which is the voltage from the power supply end to the fault point, represents the total impedance between the fault point and the power supply, which is jointly determined by factors such as the line impedance of the distribution network, the transformer impedance, and the internal impedance of the distributed power source. Regarding the distributed power source as an ideal power source, it is assumed that its internal resistance is small.

[0067] In the distribution network, especially when considering different topological structures (such as radial, ring network, etc.), the current flow path will affect the final short-circuit current magnitude; therefore, the short-circuit current calculation formula should consider the network topology, and the short-circuit current calculation model can be further extended, expressed as:

[0068] ,

[0069] Among them, represents the short-circuit current adjusted according to the topology, which is corrected according to the power grid topology structure. represents the network impedance of the distribution network, taking into account the topological influence of the distribution network. Especially in different types of topological structures (such as loop network type, grid type, etc.), the current flow path and network impedance are different.

[0070] Specifically, input the access parameters of the distributed power source: First, it is necessary to input the detailed access parameters of the distributed power source according to the project requirements, including the access method (for example, access through the substation bus or feeder), power capacity (for example, the maximum output capacity of photovoltaic, wind power or other distributed power sources), voltage level (the voltage matching situation between the distributed power source and the distribution network), and access location (for example, the core area of the distribution network or the end of the feeder). The above parameters determine the impact of the distributed power source on the short-circuit current of the power grid and reflect the current change situation of the power grid after accessing different power sources;

[0071] Select the distribution network topology type and electrical parameters: Second, it is necessary to select the topology type of the distribution network, such as radial type, loop network type or grid type. Each topological structure will affect the current distribution path and flow mode, and needs to be selected according to the actual power grid design; The loop network type and grid type structures involve multiple current flow paths. Pay attention to inputting the electrical parameters of relevant components, especially the impedance of transformers, the resistance and reactance of lines, etc.; The input of the above parameters helps to simulate the current response and behavior of each part of the power grid and ensure the accuracy of the calculation model;

[0072] Use power system analysis software for calculation: After inputting the access parameters and topology information, calculate the short-circuit current; According to the input power grid topology and component parameters, combined with the access situation of the power source, calculate the current; During the calculation process, considering the impedance of each component in the power grid and the current transmission characteristics between the power source and the fault point, obtain the short-circuit current value when the fault occurs;

[0073] Adjust the protection setting value: Finally, according to the calculation result, adjust the setting value of the protection device; If the calculated short-circuit current is too large, resulting in misoperation or overload of the protection device, it is necessary to appropriately reduce the protection setting value to ensure that the system can respond in time when a fault occurs and prevent the damage of overcurrent; If the short-circuit current is too small, it will lead to insufficient sensitivity of the protection system and inability to effectively identify small faults. It is necessary to improve the protection sensitivity to ensure that even slight current fluctuations can be detected in time and the fault area can be cut off.

[0074] S3: Determine the protection setting value according to the short-circuit current calculation result and the protection setting principle.

[0075] It should be noted that, as Figure 1 shown in S3, the protection setting principle includes three-section protection, and the protection method combines instantaneous overcurrent protection in section I, time-limited overcurrent protection in section II, and definite-time overcurrent protection in section III.

[0076] Furthermore, the protection in section I: instantaneous cut-off, the protection range is a part of this section of the line, and it is used to quickly cut off serious faults;

[0077] The protection in section II: time-limited cut-off, the protection range is the full length of this section of the line and a part of the next-level line, and it serves as the backup of the protection in section I;

[0078] The protection in section III: definite-time overcurrent protection, the protection range is the full length of this section of the line and the full length of the lower-level line, and it serves as the backup of the protection in section II;

[0079] The protection setting value is input according to the short-circuit current calculation result, and the system provides a setting value suggestion based on the calculated current value.

[0080] Furthermore, the main function of the protection in section I is to quickly cut off the serious fault area, and it is usually used to handle sudden and extremely serious faults such as short circuits; the setting of the protection value in section I needs to be based on the rapid change of the short-circuit current and achieve action in an extremely short time; when setting the protection value in section I, first, the power system will calculate the short-circuit current to obtain the current value of the current fault point; if the calculated short-circuit current exceeds the set protection value in section I (for example, 300A), the protection in section I will immediately act and quickly cut off the fault area; if the protection value in section I is set too high (for example, exceeding 500A), the system will issue a warning indicating that the protection action may be delayed, resulting in the failure to isolate the fault in time; at this time, the system will suggest reducing the protection value in section I to ensure that it can quickly respond when the current exceeds the set value and prevent the above-mentioned fault from spreading;

[0081] The protection of section II is the backup protection for the protection of section I, mainly used to handle relatively minor faults or provide a second layer of protection when the protection of section I fails to act in a timely manner; the protection of section II usually has a set time delay to ensure that the fault area can be cut off in a timely manner when the protection of section I fails; the setting of the protection value of section II usually requires that it act when the short-circuit current is greater than the set value of section II but does not reach the protection value of section I; for example, the set value of the protection of section II is set to 150A; when the short-circuit current exceeds 150A but is lower than 300A, the protection of section II will act after the set time delay; if the protection value of section II is set too low (such as set to 100A), the system will remind the user that this setting may cause the protection of section II to be too sensitive, so that it may trigger the protection action during normal load fluctuations, resulting in mis-cutting of the normal area; at this time, the system will recommend increasing the protection value of section II to ensure that the protection of section II will only be triggered in the event of a real fault; the system allows the user to adjust the time delay of the protection of section II, usually set between a few hundred milliseconds and a few seconds; this time delay ensures the priority of the protection of section I and also provides the protection of section II with response time;

[0082] The protection of section III is used as the ultimate protection, usually for handling relatively persistent and extensive faults; its setting purpose is to prevent the large-scale paralysis of the power grid due to faults when the protection of section II fails or the current remains large; the setting of the protection value of section III usually requires that it act when the short-circuit current is large (such as exceeding the protection value of section II); for example, the set value of the protection of section III is set to 50A; when the current is greater than 50A but does not reach the set value of section II, the protection of section III will act after an additional set time; ensure that the most serious faults in the power grid can be finally cut off, and avoid the equipment and lines being in an overcurrent state for a long time; if the protection value of section III is set too low (for example, set to 30A), the system will remind that this value will cause misoperation, especially in the case of large current fluctuations; at this time, the system will recommend increasing the protection value of section III to ensure that it will only be started in the event of a truly serious fault; the protection of section III requires a longer time delay to ensure that when the protection of section II fails to respond in a timely manner, the protection of section III can effectively supplement; for example, the delay time of the protection of section III may be set to a few seconds to avoid overprotection of short-term faults; the system provides an adjustable time delay setting, which is adjusted according to the fault type and operating state of the power grid;

[0083] When setting the protection value, it is necessary to consider the change of the short-circuit current after the access of distributed power sources, and appropriately adjust the protection value to ensure the selectivity and sensitivity of the protection; special protection measures are also required, including anti-islanding protection: install an anti-islanding protection device at the connection point of the distributed power source, and quickly cut off the connection between the distributed power source and the power grid when an islanding phenomenon is detected; reclosing configuration: configure the reclosing function according to the actual situation and fault type of the distribution network to improve the power supply reliability.

[0084] Specifically, Section I protection: It is mainly used to quickly cut off serious faults, such as emergency faults like short circuits; this section of protection is usually set to the lowest current value. Once the short-circuit current exceeds the set value of Section I, the protection device will act immediately, quickly cut off the fault area, and prevent the expansion of the fault;

[0085] Section II protection: It is usually used for relatively minor faults or as a backup for Section I protection. When the short-circuit current reaches the set value of Section I, Section II protection will act after a set time delay, usually cutting off a wider area to ensure that the fault does not spread to a farther area;

[0086] Section III protection: Time-delay overcurrent protection, as the final protection level. When the fault area is not isolated by the first two sections of protection, Section III protection will act by increasing the set time to ensure that a wider area can be effectively protected and prevent equipment damage caused by continuous overcurrent;

[0087] Integration of special protection measures: Anti-islanding protection: Combining the output characteristics of distributed power sources in short-circuit current calculation, an anti-islanding protection device is installed at the point of common coupling; when it detects the disappearance of short-circuit current (islanding phenomenon) or the isolated operation of distributed power sources, it quickly cuts off the connection between the distributed power source and the power grid to avoid chaos in power grid operation; Reclosing function: Configuration basis: According to whether the short-circuit current quickly returns to the normal current value after the fault is cleared, determine the number of reclosing operations and the time interval; Setting goal: Ensure power supply can be restored after the fault is cleared, and at the same time avoid secondary impact on the area where the fault has not been cleared caused by the reclosing operation.

[0088] By combining the short-circuit current calculation results, the three-stage protection can more accurately adapt to the current change characteristics after the integration of distributed power sources; Section I protection responds quickly, Section II protection provides backup, Section III protection provides full coverage, and together with the cooperation of anti-islanding protection and reclosing function, the entire distribution network protection scheme has higher reliability and selectivity.

[0089] S4: Verify the protection performance to ensure correct operation when a fault occurs.

[0090] It should be noted that, as Figure 1 shown in S4, verifying the protection performance includes protection setting value adjustment and fault recovery and reclosing verification;

[0091] Among them, protection setting value adjustment includes adjusting the action setting value of the protection device according to the short-circuit current calculation results and protection setting value setting principles to ensure correct operation under specific fault conditions; Reclosing verification includes configuring the reclosing function according to the actual situation of the distribution network and the fault type, verifying power supply restoration after disconnecting the fault and checking the effect after reclosing; Fault recovery includes observing the power supply restoration situation after testing the reclosing.

[0092] Furthermore, the protection performance verification not only needs to be simulated and verified through simulation software, but also needs to be experimentally verified on-site. The simulation verification can simulate different types of fault scenarios (such as single-phase grounding, three-phase short circuit, etc.) by constructing a power grid model to test the action sensitivity and selectivity of protection equipment under various operating conditions. The on-site experiment can verify the response performance of the protection device under real working conditions by actually triggering a fault or a fault simulation device. This dual verification method combining simulation and experiment helps to improve the reliability and accuracy of protection settings.

[0093] Even further, during the verification process, the dynamic changes in power grid operation, such as load fluctuations, uncertainties in distributed power generation output, etc., should be fully considered. The verification needs to verify the performance of protection equipment under different load levels and various distributed power generation output conditions to ensure that the protection settings can adapt to various operating states. In addition, the time coordination of the protection device needs to be tested emphatically to verify whether good coordinated actions can be achieved among the upper-level protection, lower-level protection, and same-level protection, and to avoid misoperation or refusal to operate.

[0094] Specifically, the reclosing verification not only needs to test its basic functions, but also needs to verify its coordination performance with the protection device. For example, after a fault occurs, the reclosing needs to complete the reclosing action in time after the protection equipment removes the fault and ensure that no secondary impact is caused to the incompletely cleared fault. In addition, it also needs to be verified whether the reclosing can automatically withdraw after multiple reclosing failures to avoid further damage to the equipment or causing more serious faults.

[0095] The above is a schematic solution of a method for setting distribution network protection settings in a distributed power grid connection scenario of this embodiment. It should be noted that the technical solution of the system for the method for setting distribution network protection settings in a distributed power grid connection scenario belongs to the same concept as the above technical solution of the method for setting distribution network protection settings in a distributed power grid connection scenario. For the details not described in detail in the technical solution of the system for the method for setting distribution network protection settings in a distributed power grid connection scenario in this embodiment, reference can be made to the description of the technical solution of the above method for setting distribution network protection settings in a distributed power grid connection scenario.

[0096] A system for setting distribution network protection settings in a distributed power grid connection scenario in this embodiment is characterized in that it includes: a data collection module, a current calculation module, a protection setting module, and a performance verification module;

[0097] The data collection module collects and obtains basic data;

[0098] The current calculation module calculates the short-circuit current according to the access situation of distributed power sources and the topological structure of the distribution network;

[0099] The protection setting module determines protection settings according to the short-circuit current calculation results and protection setting principles;

[0100] The performance verification module verifies the protection performance to ensure correct operation when a fault occurs.

[0101] This embodiment also provides a computing device applicable to a method for setting distribution network protection settings in a distributed power grid connection scenario, including:

[0102] A memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement a method for setting distribution network protection settings in a distributed power grid connection scenario as proposed in the above embodiment.

[0103] This embodiment also provides a storage medium with a computer program stored thereon, and when the program is executed by a processor, it implements a method for setting distribution network protection settings in a distributed power grid connection scenario as proposed in the above embodiment.

[0104] The storage medium proposed in this embodiment and a method for setting distribution network protection settings in a distributed power grid connection scenario proposed in the above embodiment belong to the same inventive concept. Technical details not described in detail in this embodiment can be referred to in the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0105] If the above functions are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or a part of this technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0106] Logic and / or steps described otherwise herein, for example, can be considered as a defined sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or used in combination with these instruction execution systems, apparatus, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0107] It should be understood that various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, any one or a combination of the following techniques well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

[0108] Example 2, referring to Figure 2 , which is an embodiment of the present invention. This embodiment provides a method for setting distribution network protection settings in a distributed power grid connection scenario. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0109] Fault simulation and current calculation: For different fault types, use simulation tools (such as ETAP, DIgSILENT, or MATLAB, etc.) to simulate the current distribution after a fault occurs; according to the impedance parameters of the power grid, calculate the short-circuit current values of each node and line, and focus on the changes in the current distribution at the fault point, the end of the feeder, and the distributed power grid connection point; the calculation results obtained: the short-circuit current values of each fault point: including the amplitude and phase of the short-circuit current at the fault point, to clarify the current characteristics of the power grid after a fault occurs; the current distribution of key nodes and lines: mark the short-circuit current of each key point (such as the distributed power grid connection point, the end of the feeder, etc.); the contribution of the distributed power grid to the short-circuit current: calculate the current output of the distributed power grid under different fault conditions and evaluate its impact on the short-circuit current of the entire power grid.

[0110] I. Experimental conditions:

[0111] Experimental platform: Use DIgSILENT or MATLAB / Simulink.

[0112] Network structure: Radial and loop network distribution network topologies, including distributed power access points.

[0113] II. Equipment parameters:

[0114] Main transformer capacity: 50 MVA.

[0115] Distributed power capacity: 1.5 MW.

[0116] Line impedance: , .

[0117] Fault types: Three-phase short circuit and single-phase grounding fault.

[0118] III. Experimental steps:

[0119] (1) Establish a simulation model:

[0120] Create a distribution network model including a substation, distributed power sources, and multiple feeders. Adopt two topologies: radial and loop network types; set the distributed power access points at different positions and record the distribution changes of short-circuit currents.

[0121] (2) Set fault scenarios:

[0122] Simulate three-phase short circuit and single-phase grounding faults at the end of each feeder and the distributed power access points. Record the magnitude of the short-circuit current and the current flow path for each fault point.

[0123] (3) Design of experimental group and control group:

[0124] Control group: Traditional distribution network without protection setting adjustment. Experimental group: Adopt the protection setting adjustment method proposed in the present invention and introduce distributed power sources.

[0125] (4) Verification of protection performance:

[0126] Compare the operation of protection devices in the experimental group and the control group under different fault scenarios, including operation time, sensitivity, and selectivity. Verify the effectiveness of the reclosing function and the anti-islanding protection device.

[0127] (5) Data analysis:

[0128] Statistical protection operation time, misoperation rate, and refusal rate in the experimental group and the control group when a fault occurs. Compare the protection performance of the two groups through tables and graphs, as shown in Table 1 below and Figure 2 shown:

[0129] Table 1 Key data in the simulation experiment

[0130]

[0131] Figure 2 : Create two structures, namely the radial topology and the ring network topology, and display them with different layouts; add distributed power access points (marked with special icons); mark the key fault points and show the current flow path through arrows; use different colors and line widths to show the magnitude and direction of the current; provide explanatory labels to clarify the key devices and data characteristics.

[0132] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario, characterized in that: include: Collect and obtain basic data; Calculate the short-circuit current based on the access status of distributed generation and the topological structure of the distribution network; Determine the protection setting value based on the short-circuit current calculation results and the protection setting value setting principle; Verify protection performance to ensure correct operation when a fault occurs; The distributed power access situation includes the access mode, capacity, access location and voltage level of the distributed power source; The access method includes connecting the power supply to the substation bus, converting the power supply voltage through a transformer and transmitting it to the distribution network; using a real-time monitoring system to dynamically adjust the power factor and load adaptability of the connected power supply; When a large-capacity distributed power source is connected, the short-circuit current value at the access point increases, so the protection setting value is adjusted; when a small-capacity distributed power source is connected, the short-circuit current value at the access point decreases, so the sensitivity is adjusted; When the distributed generation is connected to the end of the feeder, the fault current increases; when the distributed generation is connected to the core area of ​​the distribution network, the short-circuit current decreases; When connected at a high voltage level, the voltage is reduced through a transformer to match the voltage of the distribution network; when connected at a low voltage level, the voltage is converted through an inverter to match the voltage of the distribution network; The calculation of the short-circuit current includes the total impedance Z between the fault point and the power supply. total , using the formula Calculate the basic circuit current; When considering the network impedance Z of the distribution network network When using the formula Calculate the adjusted short-circuit current; Among them, I sc Indicates short-circuit current, V L Indicates the line-to-ground voltage, Z total Represents the total impedance between the fault point and the power supply; I sc，adjusted represents the short-circuit current adjusted according to the topology, z network Represents the network impedance of the distribution network; The protection setting principle includes three-stage protection, which adopts a protection mode combining stage I instantaneous current quick-break protection, stage II time-limited current quick-break protection and stage III time-limited overcurrent protection; Input the protection setting value according to the short-circuit current calculation result, and the system will provide setting value suggestions based on the calculated current value; The protection setting value of stage I is set to I1=300A. When the short-circuit current exceeds the protection setting value of stage I, stage I protection will immediately operate to isolate the fault area. The protection setting value of stage II is set to I2=150A. When the short-circuit current exceeds the protection setting value of stage II but does not reach the protection setting value of stage I, stage II protection will operate after the set time and perform backup protection. The protection setting value of stage III is set to I3=50A. When the short-circuit current is greater than the protection setting value of stage III but does not reach the protection setting value of stage II, the set time will be increased and the protection will operate after the increased set time. The protection setting is dynamically adjusted according to the calculated short-circuit current result. If the protection setting of stage I is set to more than 500A, the system will prompt that the protection setting of stage I causes delayed action, and the protection setting of stage I will be lowered; if the protection setting of stage II is set to less than 100A, the system will prompt that it does not act after the set time, resulting in misleading cutting off of the normal area, and the protection setting of stage II will be increased; if the protection setting of stage III is set to less than 30A, the system will prompt that the protection setting of stage III causes false action, and the protection setting of stage III will be increased.

2. A method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario according to claim 1, characterized in that: The basic data includes the capacity of the distributed power source, the access location, the topological structure of the distribution network and the line parameters.

3. A method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario according to claim 2, characterized in that: The topological structure of the distribution network includes the connection relationship and topological form of the distribution network components; Among them, the connection relationship includes radial type and ring network type; the radial type ensures automatic adjustment of power supply by real-time monitoring of power grid status, using dynamic load adjustment and fault-tolerant calculation, and scheduling optimization; the ring network type forms an adaptive grid by combining the access of distributed power sources. When a fault occurs, the distributed power sources switch to the backup path and automatically adjust the current distribution to reduce the power grid recovery time; Topological forms include radial structure, ring network structure and mesh structure; in radial structure, current flows through a single path; compared with radial structure, ring network structure has more paths; in mesh structure, current flows through mesh path; it determines the distribution and flow path of short-circuit current when a fault occurs.

4. A method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario according to claim 3, characterized in that: The protection performance verification includes protection setting adjustment and fault recovery and reclosing verification; Among them, protection setting adjustment includes adjusting the action settings of the protection equipment according to the short-circuit current calculation results and the protection setting principles to ensure correct operation under specific fault conditions; reclosing verification includes configuring the reclosing function according to the actual situation of the distribution network and the fault type, verifying the restoration of power supply after disconnecting the fault and checking the effect of reclosing; fault recovery includes observing the restoration of power supply after testing the reclosing.

5. A distribution network protection setting value setting system in a distributed power grid-connected scenario, using a distribution network protection setting value setting method in a distributed power grid-connected scenario as described in any one of claims 1 to 4, characterized in that: include: Data collection module, current calculation module, protection setting module and performance verification module; The data collection module collects and obtains basic data; The current calculation module calculates the short-circuit current according to the access status of the distributed power source and the topological structure of the distribution network; The protection setting module determines the protection setting value according to the short-circuit current calculation result and the protection setting value setting principle; The performance verification module verifies the protection performance to ensure correct operation when a fault occurs.

6. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of a method for setting a distribution network protection constant in a distributed power grid-connected scenario described in any one of claims 1 to 4 are implemented.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a method for setting a distribution network protection constant value in a distributed power grid-connected scenario described in any one of claims 1 to 4 are implemented.

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