Distribution network protection fixed value setting method and system in distributed power supply grid-connected scene

Abstract

The invention relates to the technical field of power distribution network protection and distributed power supply grid connection, in particular to a power distribution network protection fixed value setting method and system under a distributed power supply grid connection scene. The method comprises the steps of collecting and acquiring basic data, calculating short-circuit current according to a distributed power supply access condition and a topological structure of a power distribution network, determining a protection fixed value and verifying protection performance according to a short-circuit current calculation result and a protection fixed value setting principle, and ensuring correct action when a fault occurs; meanwhile, a protection fixed value is reasonably set, the characteristics of the distributed power supply are adapted, and the selectivity and sensitivity of a protection system are guaranteed; by configuring a reclosing function, the power supply reliability and the fault recovery capability are improved; meanwhile, automatic data collection and protection setting processes are utilized to adapt to different power distribution network topological structures, and stable operation of the power grid under various structures is ensured.

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 above problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the technical problems to be solved by the present invention are: ensuring the safety of the power grid: in the scenario of distributed power generation grid connection, the setting of protection settings should ensure that the power grid can quickly and accurately isolate the fault area when a fault occurs to prevent the fault from expanding. Improving power supply reliability: through reasonable protection setting, the power outage time and scope of non-fault areas can be reduced, and the power supply reliability can be improved. Adapting to the characteristics of distributed power sources: considering the output volatility and uncertainty of distributed power sources, a flexible protection setting strategy is formulated. The setting scheme of distribution network protection settings in the scenario of distributed power generation grid connection is a systematic project, which needs to comprehensively consider multiple aspects such as the access method of distributed power sources, impact analysis, protection setting principles, and special protection measures. Through a scientific and reasonable setting scheme, the safe and stable operation of the power grid in the scenario of distributed power generation grid connection is ensured.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: a method for setting distribution network protection constants in a distributed power grid-connected scenario, comprising: collecting and acquiring basic data; calculating the short-circuit current according to the distributed power access situation and the topological structure of the distribution network; determining the protection constant according to the short-circuit current calculation result and the protection constant setting principle; and verifying the protection performance to ensure that it can operate correctly when a fault occurs.

[0008] As a preferred solution of the method for setting the constant value of distribution network protection in a distributed power grid-connected scenario described in the present invention, the basic data includes the capacity, access location, topological structure and line parameters of the distributed power source.

[0009] As a preferred solution of the method for setting the fixed value of distribution network protection in a distributed power grid-connected scenario described in the present invention, wherein: the distributed power access situation includes the access mode, capacity, access location and voltage level of the distributed power; 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.

[0010] As a preferred solution of the method for setting the fixed value of distribution network protection in a distributed power grid-connected scenario described in the present invention, wherein: 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.

[0011] As a preferred solution of the method for setting the fixed value of distribution network protection in a distributed power grid-connected scenario described in the present invention, the calculation of the short-circuit current includes representing the short-circuit current based on Ohm's law and combining the impedance of the power system, which is expressed as: , in, Indicates the short-circuit current, Indicates the line-to-ground voltage. It represents the total impedance between the fault point and the power supply; Considering the network topology, the short-circuit current is further expanded and expressed as: , in, represents the short-circuit current adjusted according to the topology, Represents the network impedance of the distribution network.

[0012] As a preferred solution of the distribution network protection setting value setting method in a distributed power grid-connected scenario described in the present invention, wherein: the protection setting value 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 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 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 be activated after the set time and provide backup protection; the protection setting value of stage III is set to When the short-circuit current is greater than the protection setting value of stage III but less than the protection setting value of stage II, the setting time is increased and the device will operate after the increased setting 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.

[0013] As a preferred solution of the method for setting the fixed value of distribution network protection in a distributed power grid-connected scenario described in the present invention, wherein: the protection performance verification includes protection fixed value 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.

[0014] Another object of the present invention is to provide a distribution network protection constant setting system in a distributed power grid-connected scenario, which can automatically collect basic data, calculate short-circuit current, set protection constants, and perform protection performance verification, thereby improving the safety, reliability and fault response capability of the power grid after the distributed power sources are connected to the grid.

[0015] In order to solve the above technical problems, the present invention provides the following technical solutions: a distribution network protection setting value setting system in a distributed power grid-connected scenario, comprising: a data collection module, a current calculation module, a protection setting module and a 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.

[0016] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of the method for setting a distribution network protection constant in a distributed power grid-connected scenario as described above are implemented.

[0017] 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 the distribution network protection constant setting method in a distributed power grid-connected scenario as described above are implemented.

[0018] The beneficial effects of the present invention are as follows: through a scientific and reasonable distribution network protection constant value setting scheme, the safety and reliability of the power grid can be effectively improved, and after the distributed power source is connected to the grid, it is ensured that the power grid can quickly and accurately isolate the fault area to prevent the fault from spreading; the protection constant value is reasonably set to adapt to the characteristics of the distributed power source and ensure the selectivity and sensitivity of the protection system; the reclosing function is configured to improve the power supply reliability and fault recovery capability of the power grid; at the same time, automated data collection, short-circuit current calculation and protection constant value setting process are adopted to reduce manual intervention, improve work efficiency, and enhance the intelligent level of distribution network protection; finally, it adapts to the characteristics of different distribution network topologies to ensure the stable operation of the power grid under various structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0020] Figure 1 A flow chart of a method for setting a distribution network protection constant value in a distributed power grid-connected scenario provided by an embodiment of the present invention.

[0021] Figure 2 A schematic diagram of a simulation model of a method for setting a distribution network protection constant value in a distributed power grid-connected scenario provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0023] Example 1, reference Figure 1 , is an embodiment of the present invention, which provides a method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario, including: S1: Collect and obtain basic data.

[0024] It should be noted that if Figure 1 As shown in S1, the basic data includes the capacity of distributed power sources, access location, topological structure of distribution network and line parameters; the capacity of distributed power sources: including the maximum output capacity of each power source; 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: including the structural layout of the network, each structure has different effects on current flow and fault response; line parameters: covering the electrical characteristics of the wires such as resistance and reactance; Furthermore, the analysis of the above basic data involves not only static collection but also dynamic monitoring; for example, the real-time output of distributed power sources such as photovoltaic or wind power generation may fluctuate due to weather conditions, so real-time data is needed for more accurate protection setting.

[0025] Furthermore, by collecting data through real-time monitoring systems, protection strategies can be dynamically adjusted to adapt to changing network conditions and distributed power output; for example, when a large-capacity power supply suddenly increases its output, the protection setting may need to be adjusted to prevent overload.

[0026] Specifically, data collection can be achieved through various sensors and smart devices installed at key access points and grid nodes; the collected data is transmitted to the central control panel via high-speed communication networks for in-depth analysis and processing.

[0027] S2: Calculate the short-circuit current based on the access status of distributed power sources and the topological structure of the distribution network.

[0028] It should be noted that if Figure 1 As shown in S2, the distributed power access situation includes the access mode, capacity, access location and voltage level of the distributed power; Access method: The access method of distributed power sources determines the contribution of the power source to the power grid; For example, the power supply can be connected to the distribution network through the substation bus, and the voltage is converted by the transformer and then transmitted to the distribution network; the above access method usually affects the voltage matching between the power supply and the distribution network, and then affects the amplitude and characteristics of the short-circuit current; Capacity and access location: The impact of the access location on the short-circuit current is particularly important; when the power supply is connected to the core area of ​​the distribution network, the short-circuit current decreases, and when the power supply is connected to the end of the feeder, the short-circuit current value near the fault point increases; because of the different current paths and the different output capacities of the power supply, the magnitude of the short-circuit current is directly affected; Voltage level: Different voltage levels will also affect the short-circuit current. High-voltage level access usually reduces the voltage through a transformer to match the distribution network voltage, while low-voltage level access to distributed power sources uses an inverter for voltage conversion; at this time, the conversion efficiency of the inverter or transformer needs to be considered when calculating the short-circuit current; 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.

[0029] Furthermore, when calculating the short-circuit current, it is necessary to consider the basic situation of power supply access and introduce a real-time monitoring system to dynamically adjust the load adaptability and power factor of the system; as the grid load changes, the output characteristics of the power supply will also change; Furthermore, the topological structure of the distribution network has a decisive influence on the short-circuit current calculation. The topological structure of the distribution network defines the flow path and distribution pattern of the current; 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; Radial type: through real-time monitoring of the grid status, using dynamic load adjustment and fault-tolerant calculation, and dispatch optimization to ensure that the power supply meets automatic adjustment; Ring network type: combined with the access of distributed power sources to form an adaptive grid, when a fault occurs, the distributed power sources switch to the backup path and automatically adjust the current distribution to reduce the grid recovery time; Topological forms include radial structure, ring network structure and grid structure; 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 the current distribution needs to be dynamically optimized through real-time monitoring and load regulation systems; Ring network structure: Compared with the radial type, the ring network distribution network has more paths and the flow of current is more complicated. When a fault occurs, the current flows along the original path and through the backup 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 flow path of the current, and the current distribution can be automatically adjusted to reduce the grid recovery time. Grid structure: In a grid-type distribution network, current flows through multiple paths and the current distribution is the most complex. At this time, the multiple redundancy of the network requires that all possible paths be considered 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 be quickly restored when a fault occurs.

[0030] Furthermore, the calculation of the short-circuit current includes expressing the short-circuit current based on Ohm's law in combination with the impedance of the power system, which is expressed as: , in, Indicates short-circuit current, which represents the intensity of the current in the power grid when a fault occurs. Indicates the line-to-ground voltage, which is the voltage from the power supply end to the fault point. It represents the total impedance from the fault point to the power source, which is determined by the line impedance of the distribution network, the transformer impedance, the internal impedance of the distributed power source, etc. The distributed power source is regarded as an ideal power source and its internal resistance is assumed to be small. In the distribution network, especially when considering different topologies (such as radial network, ring network, etc.), the path of current flow will affect the final short-circuit current; therefore, the calculation formula of short-circuit current should consider the network topology, and the short-circuit current calculation model can be further expanded and expressed as: , in, Indicates the short-circuit current after topology adjustment, which is corrected according to the grid topology. It represents the network impedance of the distribution network, taking into account the topological influence of the distribution network, especially in different types of topologies (such as ring network, mesh network, etc.), the current flow path and network impedance are different.

[0031] Specifically, input the access parameters of distributed power sources: First, it is necessary to input the detailed access parameters of distributed power sources according to project requirements, including access mode (for example, access through substation bus or feeder), power capacity (for example, the maximum output capacity of photovoltaic, wind or other distributed power sources), voltage level (voltage matching between distributed power sources and 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 distributed power sources on the short-circuit current of the power grid and reflect the current changes of the power grid after connecting to different power sources; Select the distribution network topology type and electrical parameters: Secondly, you need to select the distribution network topology type, such as radial, ring or mesh. Each topology structure will affect the distribution path and flow mode of the current, and needs to be selected according to the actual grid design; Ring and mesh structures involve multiple current flow paths, so pay attention to inputting the electrical parameters of related components, especially the impedance of the transformer, the resistance and reactance of the line, etc.; the input of the above parameters helps simulate the current response and behavior of each part of the grid to ensure the accuracy of the calculation model; Use power system analysis software to perform calculations: After inputting access parameters and topology information, short-circuit current is calculated; current is calculated based on the input grid topology and component parameters, combined with the access status of the power supply; during the calculation process, the impedance of each component in the grid and the current transmission characteristics between the power supply and the fault point are taken into account to obtain the short-circuit current value when the fault occurs; Adjust the protection settings: Finally, adjust the settings of the protection equipment based on the calculation results. If the calculated short-circuit current is too large, causing the protection equipment to malfunction or overload, the protection settings need to be appropriately lowered to ensure that the system can respond in time to prevent damage from overcurrent when a fault occurs. If the short-circuit current is too small, the protection system will lack sensitivity and will not be able to effectively identify small faults. The protection sensitivity needs to be increased to ensure that even slight current fluctuations can be detected in time and the fault area can be removed.

[0032] S3: Determine the protection setting value based on the short-circuit current calculation results and the protection setting value setting principle.

[0033] It should be noted that if Figure 1 As shown in S3, 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.

[0034] Furthermore, Section I protection: instantaneous quick tripping, the protection range is part of this section of the line, used to quickly cut off serious faults; Section II protection: limited time quick trip, the protection range is the whole length of this section of line and part of the next level line, serving as a backup for Section I protection; Section III protection: time-limited overcurrent protection, the protection range is the entire length of this section of the line and the entire length of the lower-level line, serving as a backup for Section II 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.

[0035] Furthermore, the main function of the stage I protection is to quickly cut off the serious fault area, which is usually used to deal with sudden and extremely serious faults such as short circuits; the setting value of the stage I protection needs to be based on the rapid change of the short-circuit current and realize the action in a very short time; when setting the stage I protection setting value, 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 stage I protection setting value (for example, 300A), the stage I protection will act immediately to quickly cut off the fault area; if the stage I protection setting value is set too high (for example, more than 500A), the system will issue a warning to indicate that the protection action may be delayed, resulting in the failure to isolate the fault in time; at this time, the system will recommend lowering the stage I protection setting value to ensure that when the current exceeds the set value, it can respond quickly and prevent the above-mentioned fault from expanding; Section II protection is the backup protection for Section I protection, and is mainly used to handle minor faults or provide a second layer of protection when Section I protection does not act in time. Section II protection usually has a set time delay to ensure that the fault area can be cut off in time when Section I protection fails. Section II protection setting value usually requires that it will act when the short-circuit current is greater than Section II setting value but less than Section I protection setting value. For example, the section protection setting value is set to 150A. When the short-circuit current exceeds 150A but is less than 300A, Section II protection will act after the set time delay. If Section II protection setting value is too low (such as set to 100A), the system will remind the user that this setting may cause Section II protection to be too sensitive, which may trigger protection action during normal load fluctuations, resulting in the wrong cutting off of the normal area. At this time, the system will suggest increasing Section II protection setting value to ensure that the section protection is triggered only in real fault conditions. The system allows the user to adjust the time delay of Section II protection, which is usually set between several hundred milliseconds and a few seconds. This time delay ensures the priority of Section I protection and also provides time for the section to respond. As the final protection, stage III protection is usually used to deal with more persistent and widespread faults. Its purpose is to prevent the grid from being paralyzed on a large scale due to faults when the section protection fails or the current is continuously large. The setting of the stage III protection setting usually requires that it be activated when the short-circuit current is large (such as exceeding the stage II protection setting). For example, the stage III protection setting is set to 50A. When the current is greater than 50A but does not reach the stage II setting, the stage III protection will not be activated until the set time is increased. This ensures that the most serious faults in the grid can be finally cut off to avoid equipment and lines being in an overcurrent state for a long time. If the stage III protection setting is too low (for example, it is set to 30A), the system will remind that the setting will cause false operation, especially when the current fluctuates greatly. At this time, the system will recommend increasing the stage III protection setting to ensure that it will only be activated in the case of a truly serious fault. Stage III protection requires a longer time delay to ensure that when stage II protection fails to respond in time, stage III protection can effectively supplement it. For example, the delay time of stage III protection may be set to a few seconds to avoid overprotection for short-term faults. The system provides adjustable time delay settings, which are adjusted according to the fault type and operating status of the grid. When setting the protection setting, it is necessary to consider the change of short-circuit current after the distributed power source is connected, and adjust the protection setting appropriately to ensure the selectivity and sensitivity of the protection; special protection measures are also required, including anti-islanding protection: install anti-islanding protection devices at the distributed power source grid connection point, and quickly cut off the connection between the distributed power source and the grid when the islanding phenomenon is detected; reclosing configuration: configure the reclosing function according to the actual situation of the distribution network and the fault type to improve the power supply reliability.

[0036] Specifically, stage I protection is used to quickly cut off serious faults, such as short circuits and other emergency faults. This stage of protection is usually set to the lowest current value. Once the short-circuit current exceeds the stage I setting value, the protection device will immediately operate to quickly cut off the fault area to prevent the fault from spreading. Stage II protection: usually used for relatively minor faults or as a backup for stage I protection. When the short-circuit current reaches the set value of stage I, stage II protection will operate after a set time delay, usually to cut off a wider area to ensure that the fault does not spread to a more distant area. Stage III protection: Definite time overcurrent protection, as the final protection level, when the fault area is not isolated by the first two stages of protection, Stage III protection will increase the set time to ensure that a wider area can be effectively protected to avoid equipment damage caused by continuous overcurrent; Integration of special protection measures: Anti-islanding protection: In combination with the output characteristics of distributed power sources in short-circuit current calculation, anti-islanding protection devices are installed at the grid connection point; when it is detected that the short-circuit current disappears (islanding phenomenon) or the distributed power sources are operating in isolation, the connection between the distributed power sources and the grid is quickly cut off to avoid chaotic grid operation; Reclosing function: Configuration basis: Determine the number of reclosing operations and the time interval based on whether the calculated short-circuit current quickly recovers to the normal current value after the fault is cleared; Setting target: Ensure that power supply can be restored after the fault is cleared, and at the same time avoid secondary impact of the reclosing operation on the fault area where it has not been cleared.

[0037] By combining the short-circuit current calculation results, the three-stage protection can more accurately adapt to the current change characteristics after the distributed power source is connected to the grid; stage I protection responds quickly, stage II protection provides backup, and stage III protection provides full coverage. Coupled with the collaboration of anti-islanding protection and reclosing functions, the entire distribution network protection solution has higher reliability and selectivity.

[0038] S4: Check protection performance to ensure correct operation when a fault occurs.

[0039] It should be noted that if Figure 1 As shown in S4, 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 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.

[0040] Furthermore, protection performance verification requires not only simulation verification through simulation software, but also experimental verification on site; simulation verification can simulate different types of fault scenarios (such as single-phase grounding, three-phase short circuit, etc.) by building a power grid model, and test the action sensitivity and selectivity of the protection equipment under various operating conditions; on-site experiments can verify the response performance of the protection device under real working conditions by actually triggering the fault or fault simulation equipment; this dual verification method combining simulation and experiment helps to improve the reliability and accuracy of the protection setting.

[0041] Furthermore, during the verification process, the dynamic changes in power grid operation should be fully considered, such as load fluctuations, uncertainty in the output of distributed power sources and other factors; the verification needs to verify the performance of the protection equipment under different load levels and a variety of distributed power output conditions to ensure that the protection settings can adapt to various operating conditions; in addition, it is also necessary to focus on testing the time coordination of the protection device to verify whether the upper-level protection, lower-level protection and same-level protection can achieve good coordinated action to avoid false operation or refusal to operate.

[0042] Specifically, the verification of the reclosing switch not only requires testing its basic functions, but also verification of its coordination performance with the protection device; for example, when a fault occurs, the reclosing switch needs to complete the reclosing action in time after the protection device removes the fault, and ensure that there will be no secondary impact on the fault that has not been completely cleared; in addition, it is also necessary to verify whether the reclosing switch can automatically exit after multiple reclosing failures to avoid further damage to the equipment or cause more serious faults.

[0043] The above is a schematic scheme of a method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario of this embodiment. It should be noted that the technical scheme of the system of the method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario and the technical scheme of the method for setting a fixed value of distribution network protection in the above-mentioned distributed power grid-connected scenario belong to the same concept. The details not described in detail in the technical scheme of the system for setting a fixed value of distribution network protection in a distributed power grid-connected scenario in this embodiment can be referred to the description of the technical scheme of the method for setting a fixed value of distribution network protection in the above-mentioned distributed power grid-connected scenario.

[0044] In this embodiment, a distribution network protection setting value setting system in a distributed power grid-connected scenario is characterized by comprising: a data collection module, a current calculation module, a protection setting module and a 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.

[0045] This embodiment further provides a computing device, which is applicable to a method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario, including: A memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute computer executable instructions to implement a distribution network protection constant setting method in a distributed power grid-connected scenario as proposed in the above embodiment.

[0046] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, a distribution network protection constant value setting method in a distributed power grid-connected scenario as proposed in the above embodiment is implemented.

[0047] The storage medium proposed in this embodiment and the distribution network protection constant setting method in a distributed power grid-connected scenario proposed in the above embodiment belong to the same inventive concept. The technical details not described in detail in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0048] If the functions are implemented in the form of software functional 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, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0049] Logic and / or steps otherwise described herein, for example, may be considered as an ordered list of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (e.g., a computer-based system, a system including a processor, or other system that can fetch instructions from and execute instructions on, an instruction execution system, apparatus, or device). For purposes of this specification, a "computer-readable medium" may be any device that can contain, store, communicate, propagate, or transmit a program for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0050] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned 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, it can be implemented by any one of the following technologies known in the art or a combination thereof: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0051] Example 2, reference Figure 2 , is an embodiment of the present invention. This embodiment provides a distribution network protection constant setting method in a distributed power grid-connected scenario. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0052] Fault simulation and current calculation: For different fault types, simulation tools (such as ETAP, DIqSILENT or MATLAB, etc.) are used to simulate the current distribution after the fault occurs; according to the impedance parameters of the power grid, the short-circuit current value of each node and line is calculated, focusing on the current distribution changes at the fault point, the end of the feeder and the access point of the distributed power generation; the calculation results obtained are: the short-circuit current value of each fault point: including the short-circuit current amplitude and phase of the fault point, clarifying the current characteristics of the power grid after the fault occurs; current distribution of key nodes and lines: the short-circuit current of each key point (such as the access point of the distributed power generation, the end of the feeder, etc.) is marked; the contribution of distributed power to the short-circuit current: the current output of the distributed power generation under different fault conditions is calculated to evaluate its impact on the short-circuit current of the entire power grid.

[0053] 1. Experimental conditions: Experimental platform: DIgSILENT or MATLAB / Simulink.

[0054] Network structure: radial and ring distribution network topologies, including distributed power access points.

[0055] 2. Equipment parameters: Main transformer capacity: 50 MVA.

[0056] Distributed power generation capacity: 1.5 MW.

[0057] Line impedance: , .

[0058] Fault type: three-phase short circuit and single-phase grounding fault.

[0059] 3. Experimental steps: (1) Establishing simulation model: Create a distribution network model that includes substations, distributed power sources, and multiple feeders. Use two topologies: radial and ring; set distributed power access points at different locations and record the distribution changes of short-circuit current.

[0060] (2) Set the fault scenario: Simulate three-phase short circuit and single-phase ground fault at each feeder end and distributed generation access point. Record the magnitude of short circuit current and current flow path for each fault point.

[0061] (3) Experimental and control group design: Control group: a traditional distribution network without protection setting setting. Experimental group: a network that adopts the protection setting setting method proposed in the present invention and introduces distributed power sources.

[0062] (4) Protection performance verification: Compare the action of protection equipment in different fault scenarios between the experimental group and the control group, including action time, sensitivity and selectivity. Verify the effectiveness of the reclosing function and anti-islanding protection device.

[0063] (5) Data analysis: The protection action time, false action and refusal rate of the experimental group and the control group when the fault occurs are statistically analyzed. The protection performance of the two groups is compared through tables and graphs, as shown in Table 1 and Figure 2 As shown: Table 1 Key data in the simulation experiment

[0064] Figure 2 : Create radial and ring topologies, each with a different layout; add distributed power access points (marked with special icons); mark key fault points and use arrows to show current flow paths; use different colors and line widths to show current size and direction; provide descriptive labels to clarify key equipment and data characteristics.

[0065] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in 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.

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 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.

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 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.

5. A method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario according to claim 4, characterized in that: The calculation of the short-circuit current includes expressing the short-circuit current based on Ohm's law and combining the impedance of the power system, which is expressed as: ， in, Indicates the short-circuit current, Indicates the line-to-ground voltage. It represents the total impedance between the fault point and the power supply; Considering the network topology, the short-circuit current is further expanded and expressed as: ， in, represents the short-circuit current adjusted according to the topology, Represents the network impedance of the distribution network.

6. A method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario according to claim 5, characterized in that: 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 , when the short-circuit current exceeds the set value of stage I protection, stage I protection will immediately operate to isolate the fault area; The protection setting value of stage II is set to 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 be activated after the set time and provide backup protection; the protection setting value of stage III is set to When the short-circuit current is greater than the protection setting value of stage III but less than the protection setting value of stage II, the setting time is increased and the device will operate after the increased setting time. The protection setting is dynamically adjusted according to the calculated short-circuit current result. If the protection setting of stage I exceeds 500A, the system will prompt that the protection setting of stage I causes delayed action and lower the protection setting of stage I. If the protection setting value of stage II is set lower than 100A, the system will prompt that it has not been operated after the set time, resulting in misleading cutting off of the normal area, and the protection setting value of stage II should be increased; if the protection setting value of stage III is set lower than 30A, the system will prompt that the protection setting of stage III has caused false operation, and the protection setting value of stage III should be increased.

7. A method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario according to claim 6, 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.

8. A system for setting a fixed value of distribution network protection in a distributed power grid-connected scenario, using a method for setting a fixed value of distribution network protection in a distributed power grid-connected scenario as claimed in any one of claims 1 to 7, 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.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: 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 7 are implemented.

10. 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 in a distributed power grid-connected scenario described in any one of claims 1 to 7 are implemented.

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