Optimization control system for rapid fault recovery of power distribution network based on low-voltage flexible interconnection device

Abstract

The invention discloses a power distribution network fault rapid recovery optimization control system based on a low-voltage flexible interconnection device, and relates to the technical field of power grid fault optimization control, and the system comprises the following modules: a main network operation state prediction module which respectively obtains the voltage, current, phase and frequency of each line of a main network, and obtains a power grid operation state prediction module; a fault risk line is captured in main network lines through parameter periodicity judgment in each line of a main network, an off-network island data adjustment module is executed according to the fault risk line, a involved line is obtained according to a fault result of the fault risk line, and a involved database is established through the involved line; according to the scheme, the difference of voltage, phase and frequency of a grid-connected line in a main network and an off-grid island is calculated in an off-grid island data adjustment module, and an adjustment strategy is formulated according to a predicted fault line risk level; therefore, quick adjustment is facilitated, off-network switching is facilitated, and meanwhile, off-network island electronic equipment damage caused by frequent and large-amplitude adjustment of the catastrophe is avoided.

Description

Technical Field

[0001] This invention relates to the field of power grid fault optimization control technology, specifically to an optimized control system for rapid recovery of distribution network faults based on low-voltage flexible interconnection devices. Background Technology

[0002] Low-voltage flexible interconnection devices are the core equipment of future smart distribution networks. Based on power electronics technology, they act like a precise intelligent power dispatcher, flexibly connecting different distribution areas or feeders. They can not only optimize power flow, improve efficiency and renewable energy consumption during normal operation, but also achieve millisecond-level rapid response during grid faults. By precisely controlling active and reactive power, they can seamlessly transfer loads, support voltage, and assist in building stable islands, achieving seamless self-healing recovery of fault areas. This upgrades the traditional distribution network from a passive "rigid structure" to an active, highly resilient flexible organism. Off-grid and grid-connected switching is a key mode transition in power system operation, especially crucial in modern power grids with a high proportion of renewable energy integration. Grid-connected switching refers to the process by which distributed generation or microgrids, operating independently, adjust their voltage, frequency, and phase to strictly synchronize with the main grid and then seamlessly integrate into the main grid. Off-grid switching, on the other hand, is the rapid and smooth transition of the local system from a controlled current source mode to an autonomous voltage source mode during main grid failures or planned islanding operations, maintaining internal voltage and frequency stability and ensuring uninterrupted power supply to critical loads. During the grid-connected to off-grid switching process, if it is a planned switch, the voltage and other parameters of the island can be adjusted in advance to be the same as before grid connection, thus achieving a smooth and fluctuation-free off-grid switch. However, if an off-grid switch is forced due to a main grid fault, the island does not have enough time to adjust the voltage and other parameters in advance. Directly switching to off-grid mode will cause the power equipment to be impacted by the inrush current. If the switch is not made, it will cause power outages for users. In order to facilitate early warning of the grid connection status of non-faulty areas based on the main grid's operating status, and to make early warning adjustments to the island's voltage and other parameters, thereby facilitating rapid off-grid switch after a fault and rapid recovery after a fault, we propose an optimized control system for rapid recovery of distribution network faults based on low-voltage flexible interconnection devices. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices, thereby solving the aforementioned problems in existing technologies.

[0004] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: an optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices, comprising the following modules: The main network operation status prediction module acquires the voltage, current, phase and frequency of each line in the main network. It periodically judges the fault risk lines in the main network based on the parameters of each line. It executes the off-grid island data adjustment module based on the fault risk lines. It obtains the related lines based on the fault results of the fault risk lines and establishes a related database based on the related lines. The grid-connected line perception and assessment module obtains the location of faulty risk lines in the main network, locates related lines in the main network based on the location of faulty risk lines, obtains grid-connected risk lines by combining related lines and the related database, obtains the operating status of all grid-connected risk lines, and sets risk levels for all grid-connected risk lines based on the operating status. Based on the risk level, it determines whether the grid-connected risk lines should execute the off-grid islanding data adjustment module. The off-grid island data adjustment module obtains the adjustment difference between the main grid and the voltage, phase, and frequency of the current off-grid island, formulates an adjustment strategy for the adjustment difference based on the risk level, and adjusts the voltage, phase, and frequency of the corresponding off-grid island according to the adjustment strategy.

[0005] Preferably, in the main network operation status prediction module, fault-risk lines in the main network are captured by periodically judging the parameters of each line in the main network. Specifically: Step 1: Set the capture cycle. Continuously acquire the current in each line of the main network through the capture cycle. Obtain the current difference by subtracting the current acquired in the current capture cycle from the current acquired in the previous capture cycle for the same line. Set a current difference fluctuation safety preset threshold. Determine whether the current difference is higher than the current difference fluctuation safety preset threshold. If the current difference is higher than the current difference fluctuation safety preset threshold, mark the current value of the line as 1. If the current difference is lower than or equal to the current difference fluctuation safety preset threshold, mark the current value of the line as 0. Step 2: Continuously acquire the voltage of each line in the main network through the capture cycle. Obtain the voltage difference by subtracting the voltage acquired in the current capture cycle from the voltage acquired in the previous capture cycle for the same line. Set a voltage difference fluctuation safety preset threshold and determine whether the voltage difference is higher than the voltage difference fluctuation safety preset threshold. If the voltage difference is higher than the voltage difference fluctuation safety preset threshold, mark the voltage value of the line as 1. If the voltage difference is lower than or equal to the voltage difference fluctuation safety preset threshold, mark the voltage value of the line as 0. Step 3: Continuously acquire the phase of each line in the main network through the capture cycle. Obtain the phase difference by subtracting the phase acquired in the current capture cycle from the phase acquired in the previous capture cycle for the same line. Set a safety preset threshold for phase difference fluctuation. Determine whether the phase difference is higher than the safety preset threshold for phase difference fluctuation. If the phase difference is higher than the safety preset threshold for phase difference fluctuation, mark the phase value of the line as 1. If the phase difference is lower than or equal to the safety preset threshold for phase difference fluctuation, mark the phase value of the line as 0. Step 4: Continuously acquire the frequency of each line in the main network through the capture cycle. The frequency difference is obtained by subtracting the frequency acquired in the current capture cycle from the frequency acquired in the previous capture cycle for the same line. Set a preset safety threshold for frequency difference fluctuation. Determine whether the frequency difference is higher than the preset safety threshold. If the frequency difference is higher than the preset safety threshold, mark the frequency value of the line as 1. If the frequency difference is lower than or equal to the preset safety threshold, mark the frequency value of the line as 0. Step 5: The risk coefficient is obtained by weighted summation of the current, voltage, phase and frequency values ​​of the same capture cycle in the same line. A preset threshold for the risk coefficient is set, and it is determined whether the risk coefficient is higher than the preset threshold. If the risk coefficient is higher than the preset threshold, the line is marked as a fault risk line.

[0006] Preferably, in the main network operation status prediction module, the related lines are obtained based on the fault results of the fault risk lines, and a related database is established through the related lines, specifically as follows: Step 1: Obtain the fault results of the fault-risk line. Determine whether the line has experienced a fault based on the fault results of the fault-risk line. If the fault-risk line has experienced a fault, obtain all other faulty lines in the main network at the time of the fault and mark them as suspicious lines. Step 2: Obtain the capture cycle time of the fault risk line and mark it as the fault location time. Obtain the risk coefficient of all suspicious lines with the fault location time of the fault risk line. Set a preset threshold for the safety coefficient, and the preset threshold for the safety coefficient is less than the preset threshold for the risk coefficient. Determine whether the risk coefficient of all suspicious lines is lower than the preset threshold for the safety coefficient. If the risk coefficient of a suspicious line is lower than the preset threshold for the safety coefficient, mark the suspicious line as an associated line. Step 3: Establish a connection database, mark the faulty risk lines and all corresponding connection lines, and store them in the connection database.

[0007] Preferably, in the grid-connected line perception and assessment module, the location of faulty risk lines in the main network is obtained, and related lines in the main network are located based on the location of the faulty risk lines. The grid-connected risk lines are then obtained by combining the related lines and the associated database. Specifically: Step 1: Obtain the location of the faulty risk line in the main network, obtain all the subordinate lines of the faulty risk line and mark them as subordinate lines, obtain all the same level lines connected in parallel with the faulty line and mark them as power flow transfer lines, and combine the subordinate lines and power flow transfer lines and mark them as associated lines. Step 2: Obtain all connected lines of the faulty risk line through the connected database, obtain all associated lines of the faulty risk line, combine all connected lines and all associated lines and delete duplicate lines to obtain the grid connection risk line.

[0008] Preferably, in the grid-connected line perception and assessment module, the operating status of all grid-connected risk lines is obtained, and a risk level is assigned to all grid-connected risk lines based on the operating status, specifically as follows: Step 1: Obtain the fault location time. Based on the fault location time, obtain the risk coefficient of all grid-connected risk lines and mark it as the location time risk coefficient. Based on the fault location time, obtain the risk coefficient of all grid-connected risk lines in the previous capture cycle and mark it as the location time risk coefficient. Step 2: Obtain the location risk coefficient fluctuation value by subtracting the location time risk coefficient from the location time risk coefficient. Determine whether the location risk coefficient fluctuation value of all grid-connected risk lines is less than 0. If the location risk coefficient fluctuation value of a grid-connected risk line is less than 0, mark the grid-connected risk line as a level 4 risk. If the location risk coefficient fluctuation value of a grid-connected risk line is equal to 0, mark the grid-connected risk line as a level 3 risk. If the location risk coefficient fluctuation value of a grid-connected risk line is greater than 0, proceed to Step 3. Step 3: Set a preset threshold for the risk coefficient fluctuation value, and determine whether the location risk coefficient fluctuation value of the grid-connected risk line is less than the preset threshold. If the location risk coefficient fluctuation value of the grid-connected risk line is less than or equal to the preset threshold, then the grid-connected risk line is marked as a level 2 risk. If the location risk coefficient fluctuation value of the grid-connected risk line is greater than the preset threshold, then the grid-connected risk line is marked as a level 1 risk.

[0009] Preferably, in the grid-connected line perception and assessment module, the system determines whether the off-grid islanding data adjustment module should be executed for grid-connected risk lines based on the risk level. Specifically: Step 1: Determine whether the grid-connected risk line is a Level 1 or Level 2 risk. If the grid-connected risk line is a Level 1 or Level 2 risk, immediately execute the off-grid islanding data adjustment module on that line. If the grid-connected risk line is not a Level 1 or Level 2 risk, proceed to Step 2. Step 2: Obtain the current risk coefficient of the grid-connected risk line, obtain the risk coefficient of the fault location time of the grid-connected risk line, and determine whether the current risk coefficient is higher than the risk coefficient of the fault location time. If the current risk coefficient is higher than the risk coefficient of the fault location time, then increase the risk level of the grid-connected risk line by one level in the direction of high risk, and repeat Step 1. If the current risk coefficient is lower than or equal to the risk coefficient of the fault location time, then repeat Step 2.

[0010] Preferably, in the off-grid island data adjustment module, the adjustment difference is obtained based on the voltage, phase, and frequency of the main grid and the current off-grid island. Specifically, fault-risk lines and grid-connected risk lines are marked as lines to be adjusted. The voltage, phase, and frequency of the line to be adjusted in the main grid are obtained. The voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located are obtained. The voltage difference to be adjusted is obtained by subtracting the voltage of the line to be adjusted in the main grid from the voltage of the off-grid island in the area where the line to be adjusted is located. The phase difference to be adjusted is obtained by subtracting the phase of the line to be adjusted in the main grid from the phase of the off-grid island in the area where the line to be adjusted is located. The frequency difference to be adjusted is obtained by subtracting the frequency of the line to be adjusted in the main grid from the frequency of the off-grid island in the area where the line to be adjusted is located. The adjustment difference of the line to be adjusted is obtained by combining the voltage difference, phase difference, and frequency difference to be adjusted of the same line to be adjusted.

[0011] Preferably, in the off-grid island data conditioning module, a conditioning strategy for the conditioning difference is formulated based on the risk level, and the voltage, phase, and frequency in the corresponding off-grid island are adjusted according to the conditioning strategy, specifically as follows: Step 1: Determine if the line to be adjusted is a fault-risk line. If it is, immediately adjust the adjustment differential of the line to make the voltage, phase, and frequency of the off-grid island in the area where the line is located consistent with the voltage, phase, and frequency of the line in the main grid. If the line to be adjusted is a grid-connected risk line, proceed to Step 2. Step 2: Determine the risk level of the line to be adjusted. If the risk level of the line to be adjusted is Level 1, immediately adjust the adjustment difference of the line to be adjusted so that the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located are consistent with the voltage, phase, and frequency of the line to be adjusted in the main grid. If the risk level of the line to be adjusted is Level 2, set an adjustment buffer interval time, immediately adjust the adjustment difference of the line to be adjusted by half, and after the adjustment buffer interval time ends, adjust the remaining adjustment difference of the line to be adjusted until the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located are consistent with the voltage, phase, and frequency of the line to be adjusted in the main grid.

[0012] (III) Beneficial Effects This invention provides an optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices, which has the following beneficial effects: (1) In the grid-connected line perception and assessment module, this scheme locates the associated lines in the main network by the location of the fault risk line, and selects the lines that will be affected according to the line distribution. Then, it combines the associated lines and the entanglement database to obtain the grid-connected risk lines. After detecting the fault risk lines, it quickly captures all grid-connected risk lines with fault impact risk, and sets the risk level for these grid-connected risk lines according to their current operating status. This makes it easier to judge whether to adjust the parameters of the off-grid island in advance according to the risk level, and also makes it easier to formulate the adjustment strategy of the off-grid island parameters according to the risk level. This makes it easier to speed up the adjustment speed of the off-grid island parameters when the risk level is high, and also makes it easier to gradually adjust the off-grid island parameters when the risk level is low. This avoids the damage caused by the surge impact of the adjustment of the off-grid island electronic equipment due to blind and rapid adjustment, and avoids the situation of frequent and large-scale adjustment based on rumors.

[0013] (2) In the off-grid island data adjustment module, this scheme calculates the voltage, phase and frequency difference of the grid-connected line in the main grid and its off-grid island, so as to make it easier to grasp the adjustment range of its off-grid island parameters. Based on the predicted risk level of the fault line, the adjustment strategy is formulated, which facilitates quick adjustment and convenient off-grid switching while avoiding frequent large-scale adjustments caused by speculation, which may damage the off-grid island electronic equipment. Attached Figure Description

[0014] Figure 1 This is a flowchart of the optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices, as described in this invention. Figure 2 This is a schematic diagram of the module structure of the optimized control system for rapid recovery of power distribution network faults based on a low-voltage flexible interconnection device, as described in this invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please see Figures 1-2 This invention provides an optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices, comprising the following modules: The main network operation status prediction module acquires the voltage, current, phase and frequency of each line in the main network. It periodically judges the fault risk lines in the main network based on the parameters of each line. It executes the off-grid island data adjustment module based on the fault risk lines. It obtains the related lines based on the fault results of the fault risk lines and establishes a related database based on the related lines. The grid-connected line perception and assessment module obtains the location of faulty risk lines in the main network, locates related lines in the main network based on the location of faulty risk lines, obtains grid-connected risk lines by combining related lines and the related database, obtains the operating status of all grid-connected risk lines, and sets risk levels for all grid-connected risk lines based on the operating status. Based on the risk level, it determines whether the grid-connected risk lines should execute the off-grid islanding data adjustment module. The off-grid island data adjustment module obtains the adjustment difference between the main grid and the voltage, phase, and frequency of the current off-grid island, formulates an adjustment strategy for the adjustment difference based on the risk level, and adjusts the voltage, phase, and frequency of the corresponding off-grid island according to the adjustment strategy.

[0017] In this embodiment, the main grid operation status prediction module detects faulty risk lines in the main grid by monitoring the voltage, current, phase, and frequency fluctuations of each line. It adjusts the voltage, current, phase, and frequency of the off-grid islands in the area where the faulty risk lines are located to be the same as those in the main grid. This facilitates a smooth and seamless switch from grid-connected to off-grid status after a faulty line fails. Based on the fault results of the faulty risk lines, it obtains the related lines and establishes a related database. This facilitates the capture of the distribution of affected lines based on historical fault records. It also facilitates subsequent fault warnings for related lines based on the data in the related database, thus facilitating rapid off-grid switching after a fault and rapid recovery after a fault. This solution locates associated lines in the main network by identifying the location of faulty risk lines in the grid-connected line perception and assessment module. Based on the line distribution, it selects lines that will be affected and, combined with the associated lines and the related database, identifies grid-connected risk lines. This allows for rapid capture of all grid-connected risk lines with potential fault impact after detection. Risk levels are assigned to these risk lines based on their current operating status, facilitating subsequent assessment of whether to adjust their off-grid islanding parameters in advance. It also facilitates the development of off-grid islanding parameter adjustment strategies based on risk levels. This allows for faster adjustment of off-grid islanding parameters at high risk levels and gradual adjustment at low risk levels, avoiding damage to off-grid islanded electronic equipment from inrush current surges caused by blind, rapid adjustments and preventing frequent, large-scale adjustments based on unforeseen circumstances. This solution calculates the voltage, phase, and frequency differences of the grid-connected line in the main grid and its off-grid island in the off-grid island data adjustment module, thereby making it easier to determine the adjustment range of its off-grid island parameters. Based on the predicted risk level of the faulty line, an adjustment strategy is formulated, which facilitates rapid adjustment and convenient off-grid switching while avoiding frequent and large-scale adjustments that could damage the electronic equipment on the off-grid island. It is worth mentioning that the weight values ​​in this scheme can be obtained through the analytic hierarchy process (AHP), and the preset threshold values ​​can be obtained through the weight analysis method. These will not be elaborated on further here.

[0018] In the main network operation status prediction module, fault-risk lines are periodically identified by periodically judging the parameters of each line in the main network. Specifically: Step 1: Set the capture cycle. Continuously acquire the current in each line of the main network through the capture cycle. Obtain the current difference by subtracting the current acquired in the current capture cycle from the current acquired in the previous capture cycle for the same line. Set a current difference fluctuation safety preset threshold. Determine whether the current difference is higher than the current difference fluctuation safety preset threshold. If the current difference is higher than the current difference fluctuation safety preset threshold, mark the current value of the line as 1. If the current difference is lower than or equal to the current difference fluctuation safety preset threshold, mark the current value of the line as 0. Step 2: Continuously acquire the voltage of each line in the main network through the capture cycle. Obtain the voltage difference by subtracting the voltage acquired in the current capture cycle from the voltage acquired in the previous capture cycle for the same line. Set a voltage difference fluctuation safety preset threshold and determine whether the voltage difference is higher than the voltage difference fluctuation safety preset threshold. If the voltage difference is higher than the voltage difference fluctuation safety preset threshold, mark the voltage value of the line as 1. If the voltage difference is lower than or equal to the voltage difference fluctuation safety preset threshold, mark the voltage value of the line as 0. Step 3: Continuously acquire the phase of each line in the main network through the capture cycle. Obtain the phase difference by subtracting the phase acquired in the current capture cycle from the phase acquired in the previous capture cycle for the same line. Set a safety preset threshold for phase difference fluctuation. Determine whether the phase difference is higher than the safety preset threshold for phase difference fluctuation. If the phase difference is higher than the safety preset threshold for phase difference fluctuation, mark the phase value of the line as 1. If the phase difference is lower than or equal to the safety preset threshold for phase difference fluctuation, mark the phase value of the line as 0. Step 4: Continuously acquire the frequency of each line in the main network through the capture cycle. The frequency difference is obtained by subtracting the frequency acquired in the current capture cycle from the frequency acquired in the previous capture cycle for the same line. Set a preset safety threshold for frequency difference fluctuation. Determine whether the frequency difference is higher than the preset safety threshold. If the frequency difference is higher than the preset safety threshold, mark the frequency value of the line as 1. If the frequency difference is lower than or equal to the preset safety threshold, mark the frequency value of the line as 0. Step 5: The risk coefficient is obtained by weighted summation of the current, voltage, phase and frequency values ​​of the same capture cycle in the same line. A preset threshold for the risk coefficient is set, and it is determined whether the risk coefficient is higher than the preset threshold. If the risk coefficient is higher than the preset threshold, the line is marked as a fault risk line.

[0019] In this embodiment, since the current, voltage, phase and frequency in the line will fluctuate significantly before the line fault, the faulty line can be predicted by continuously monitoring the fluctuation of the current, voltage, phase and frequency in the line. This makes it easier to adjust the parameters of the faulty line in advance and provide early warning, so as to facilitate a seamless switch from the grid-connected state to the off-grid state after the line fault.

[0020] In the main network operation status prediction module, the related lines are obtained based on the fault results of the fault risk lines, and a related line database is established through the related lines. Specifically: Step 1: Obtain the fault results of the fault-risk line. Determine whether the line has experienced a fault based on the fault results of the fault-risk line. If the fault-risk line has experienced a fault, obtain all other faulty lines in the main network at the time of the fault and mark them as suspicious lines. Step 2: Obtain the capture cycle time of the fault risk line and mark it as the fault location time. Obtain the risk coefficient of all suspicious lines with the fault location time of the fault risk line. Set a preset threshold for the safety coefficient, and the preset threshold for the safety coefficient is less than the preset threshold for the risk coefficient. Determine whether the risk coefficient of all suspicious lines is lower than the preset threshold for the safety coefficient. If the risk coefficient of a suspicious line is lower than the preset threshold for the safety coefficient, mark the suspicious line as an associated line. Step 3: Establish a connection database, mark the faulty risk lines and all corresponding connection lines, and store them in the connection database.

[0021] In this embodiment, the affected lines are obtained based on the fault results of the faulty risk lines, and an affected line database is established through the affected lines. This makes it easier to capture the distribution of affected lines based on historical fault records, and further facilitates fault warnings for the affected lines based on the data in the affected line database. This also facilitates rapid switching off the network after a fault and rapid recovery after a fault.

[0022] In the grid-connected line perception and assessment module, the location of fault-risk lines in the main network is obtained. Based on the location of the fault-risk lines, related lines in the main network are located. Combining the related lines and the interconnection database, the grid-connected risk lines are obtained, specifically: Step 1: Obtain the location of the faulty risk line in the main network, obtain all the subordinate lines of the faulty risk line and mark them as subordinate lines, obtain all the same level lines connected in parallel with the faulty line and mark them as power flow transfer lines, and combine the subordinate lines and power flow transfer lines and mark them as associated lines. Step 2: Obtain all connected lines of the faulty risk line through the connected database, obtain all associated lines of the faulty risk line, combine all connected lines and all associated lines and delete duplicate lines to obtain the grid connection risk line.

[0023] In this embodiment, the associated lines of the faulty risk line are located in the main network by the location of the faulty risk line. Then, the lines that will be affected are selected according to the line distribution. The associated lines and the related database are combined to obtain the grid-connected risk lines. After the faulty risk lines are detected, all grid-connected risk lines with fault impact risk are captured quickly, which facilitates the early warning of subsequent adjustment of their off-grid islanding parameters.

[0024] In the grid-connected line perception and assessment module, the operating status of all grid-connected risk lines is obtained, and a risk level is assigned to each line based on its operating status. Specifically: Step 1: Obtain the fault location time. Based on the fault location time, obtain the risk coefficient of all grid-connected risk lines and mark it as the location time risk coefficient. Based on the fault location time, obtain the risk coefficient of all grid-connected risk lines in the previous capture cycle and mark it as the location time risk coefficient. Step 2: Obtain the location risk coefficient fluctuation value by subtracting the location time risk coefficient from the location time risk coefficient. Determine whether the location risk coefficient fluctuation value of all grid-connected risk lines is less than 0. If the location risk coefficient fluctuation value of a grid-connected risk line is less than 0, mark the grid-connected risk line as a level 4 risk. If the location risk coefficient fluctuation value of a grid-connected risk line is equal to 0, mark the grid-connected risk line as a level 3 risk. If the location risk coefficient fluctuation value of a grid-connected risk line is greater than 0, proceed to Step 3. Step 3: Set a preset threshold for the risk coefficient fluctuation value, and determine whether the location risk coefficient fluctuation value of the grid-connected risk line is less than the preset threshold. If the location risk coefficient fluctuation value of the grid-connected risk line is less than or equal to the preset threshold, then the grid-connected risk line is marked as a level 2 risk. If the location risk coefficient fluctuation value of the grid-connected risk line is greater than the preset threshold, then the grid-connected risk line is marked as a level 1 risk.

[0025] In this embodiment, the risk level is determined based on the changes in the line operation of the grid-connected risk line when a fault is predicted on the fault-risk line. This facilitates subsequent judgment on whether to adjust the parameters of the off-grid islanding based on the risk level, and also facilitates the formulation of adjustment strategies for the off-grid islanding parameters based on the risk level. This allows for faster adjustment of the off-grid islanding parameters at high risk levels and gradual adjustment at low risk levels, avoiding damage to the off-grid islanding electronic equipment caused by blind and rapid adjustments, and avoiding frequent and large-scale adjustments based on unforeseen circumstances.

[0026] In the grid-connected line perception and assessment module, the system determines whether the off-grid islanding data adjustment module should be executed for grid-connected lines at risk based on the risk level. Specifically: Step 1: Determine whether the grid-connected risk line is a Level 1 or Level 2 risk. If the grid-connected risk line is a Level 1 or Level 2 risk, immediately execute the off-grid islanding data adjustment module on that line. If the grid-connected risk line is not a Level 1 or Level 2 risk, proceed to Step 2. Step 2: Obtain the current risk coefficient of the grid-connected risk line, obtain the risk coefficient of the fault location time of the grid-connected risk line, and determine whether the current risk coefficient is higher than the risk coefficient of the fault location time. If the current risk coefficient is higher than the risk coefficient of the fault location time, then increase the risk level of the grid-connected risk line by one level in the direction of high risk, and repeat Step 1. If the current risk coefficient is lower than or equal to the risk coefficient of the fault location time, then repeat Step 2.

[0027] In this embodiment, the operational fluctuations of the grid-connected risk line are comprehensively judged based on the risk level and the current operating status of the line. This allows for further adjustment of the risk level while determining whether the off-grid islanding data adjustment module needs to be executed immediately. This facilitates faster adjustment of the off-grid islanding parameters at high risk levels and gradual adjustment at low risk levels. It avoids damage to the off-grid islanding electronic equipment caused by blind and rapid adjustments and avoids frequent and large-scale adjustments based on unfounded rumors.

[0028] In the off-grid island data adjustment module, the adjustment difference is obtained based on the voltage, phase, and frequency of the main grid and the current off-grid island. Specifically, fault-risk lines and grid-connected risk lines are marked as lines to be adjusted. The voltage, phase, and frequency of the line to be adjusted in the main grid are obtained, as well as the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located. The voltage difference to be adjusted is obtained by subtracting the voltage of the line to be adjusted in the main grid from the voltage of the off-grid island in the area where the line to be adjusted is located. The phase difference to be adjusted is obtained by subtracting the phase of the line to be adjusted in the main grid from the phase of the off-grid island in the area where the line to be adjusted is located. The frequency difference to be adjusted is obtained by subtracting the frequency of the line to be adjusted in the main grid from the frequency of the off-grid island in the area where the line to be adjusted is located. The adjustment difference of the line to be adjusted is obtained by combining the voltage difference, phase difference, and frequency difference of the same line to be adjusted.

[0029] In the off-grid island data conditioning module, a conditioning strategy for the conditioning difference is formulated based on the risk level, and the voltage, phase, and frequency in the corresponding off-grid island are adjusted according to the conditioning strategy, specifically as follows: Step 1: Determine if the line to be adjusted is a fault-risk line. If it is, immediately adjust the adjustment differential of the line to make the voltage, phase, and frequency of the off-grid island in the area where the line is located consistent with the voltage, phase, and frequency of the line in the main grid. If the line to be adjusted is a grid-connected risk line, proceed to Step 2. Step 2: Determine the risk level of the line to be adjusted. If the risk level of the line to be adjusted is Level 1, immediately adjust the adjustment difference of the line to be adjusted so that the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located are consistent with the voltage, phase, and frequency of the line to be adjusted in the main grid. If the risk level of the line to be adjusted is Level 2, set an adjustment buffer interval time, immediately adjust the adjustment difference of the line to be adjusted by half, and after the adjustment buffer interval time ends, adjust the remaining adjustment difference of the line to be adjusted until the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located are consistent with the voltage, phase, and frequency of the line to be adjusted in the main grid.

[0030] In this embodiment, by calculating the voltage, phase, and frequency differences of the grid-connected line in the main grid and its off-grid island, it is easier to determine the required adjustment range of the off-grid island parameters. An adjustment strategy is formulated based on the predicted risk level of the faulty line, thus facilitating rapid adjustment and convenient off-grid switching while avoiding frequent, large-scale adjustments that could damage the off-grid island's electronic equipment. It is worth noting that after the adjustment buffer interval ends, since the main grid parameters may fluctuate slightly over time, adjusting all remaining adjustment differences of the line to be adjusted after the buffer interval ends means directly adjusting the current parameters in the off-grid island to be exactly the same as those in the main grid. The specific adjustment method can be achieved using phase-locked loop (PLL) technology, and the specific execution steps will not be elaborated upon here.

[0031] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0032] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0033] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. An optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices, characterized in that, Includes the following modules: The main network operation status prediction module acquires the voltage, current, phase and frequency of each line in the main network. It periodically judges the fault risk lines in the main network based on the parameters of each line. It executes the off-grid island data adjustment module based on the fault risk lines. It obtains the related lines based on the fault results of the fault risk lines and establishes a related database based on the related lines. The grid-connected line perception and assessment module obtains the location of faulty risk lines in the main network, locates related lines in the main network based on the location of faulty risk lines, obtains grid-connected risk lines by combining related lines and the related database, obtains the operating status of all grid-connected risk lines, and sets risk levels for all grid-connected risk lines based on the operating status. Based on the risk level, it determines whether the grid-connected risk lines should execute the off-grid islanding data adjustment module. The off-grid island data adjustment module obtains the adjustment difference between the main grid and the voltage, phase, and frequency of the current off-grid island, formulates an adjustment strategy for the adjustment difference based on the risk level, and adjusts the voltage, phase, and frequency of the corresponding off-grid island according to the adjustment strategy.

2. The optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices according to claim 1, characterized in that: In the main network operation status prediction module, fault-risk lines are periodically identified by periodically judging the parameters of each line in the main network. Specifically: Step 1: Set the capture cycle. Continuously acquire the current in each line of the main network through the capture cycle. Obtain the current difference by subtracting the current acquired in the current capture cycle from the current acquired in the previous capture cycle for the same line. Set a current difference fluctuation safety preset threshold. Determine whether the current difference is higher than the current difference fluctuation safety preset threshold. If the current difference is higher than the current difference fluctuation safety preset threshold, mark the current value of the line as 1. If the current difference is lower than or equal to the current difference fluctuation safety preset threshold, mark the current value of the line as 0. Step 2: Continuously acquire the voltage of each line in the main network through the capture cycle. Obtain the voltage difference by subtracting the voltage acquired in the current capture cycle from the voltage acquired in the previous capture cycle for the same line. Set a voltage difference fluctuation safety preset threshold and determine whether the voltage difference is higher than the voltage difference fluctuation safety preset threshold. If the voltage difference is higher than the voltage difference fluctuation safety preset threshold, mark the voltage value of the line as 1. If the voltage difference is lower than or equal to the voltage difference fluctuation safety preset threshold, mark the voltage value of the line as 0. Step 3: Continuously acquire the phase of each line in the main network through the capture cycle. Obtain the phase difference by subtracting the phase acquired in the current capture cycle from the phase acquired in the previous capture cycle for the same line. Set a safety preset threshold for phase difference fluctuation. Determine whether the phase difference is higher than the safety preset threshold for phase difference fluctuation. If the phase difference is higher than the safety preset threshold for phase difference fluctuation, mark the phase value of the line as 1. If the phase difference is lower than or equal to the safety preset threshold for phase difference fluctuation, mark the phase value of the line as 0. Step 4: Continuously acquire the frequency of each line in the main network through the capture cycle. The frequency difference is obtained by subtracting the frequency acquired in the current capture cycle from the frequency acquired in the previous capture cycle for the same line. Set a preset safety threshold for frequency difference fluctuation. Determine whether the frequency difference is higher than the preset safety threshold. If the frequency difference is higher than the preset safety threshold, mark the frequency value of the line as 1. If the frequency difference is lower than or equal to the preset safety threshold, mark the frequency value of the line as 0. Step 5: The risk coefficient is obtained by weighted summation of the current, voltage, phase and frequency values ​​of the same capture cycle in the same line. A preset threshold for the risk coefficient is set, and it is determined whether the risk coefficient is higher than the preset threshold. If the risk coefficient is higher than the preset threshold, the line is marked as a fault risk line.

3. The optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices according to claim 2, characterized in that: In the main network operation status prediction module, the related lines are obtained based on the fault results of the fault risk lines, and a related line database is established through the related lines. Specifically: Step 1: Obtain the fault results of the fault-risk line. Determine whether the line has experienced a fault based on the fault results of the fault-risk line. If the fault-risk line has experienced a fault, obtain all other faulty lines in the main network at the time of the fault and mark them as suspicious lines. Step 2: Obtain the capture cycle time of the fault risk line and mark it as the fault location time. Obtain the risk coefficient of all suspicious lines with the fault location time of the fault risk line. Set a preset threshold for the safety coefficient, and the preset threshold for the safety coefficient is less than the preset threshold for the risk coefficient. Determine whether the risk coefficient of all suspicious lines is lower than the preset threshold for the safety coefficient. If the risk coefficient of a suspicious line is lower than the preset threshold for the safety coefficient, mark the suspicious line as an associated line. Step 3: Establish a connection database, mark the faulty risk lines and all corresponding connection lines, and store them in the connection database.

4. The optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices according to claim 1, characterized in that: In the grid-connected line perception and assessment module, the location of fault-risk lines in the main network is obtained. Based on the location of the fault-risk lines, related lines in the main network are located. Combining the related lines and the interconnection database, the grid-connected risk lines are obtained, specifically: Step 1: Obtain the location of the faulty risk line in the main network, obtain all the subordinate lines of the faulty risk line and mark them as subordinate lines, obtain all the same level lines connected in parallel with the faulty line and mark them as power flow transfer lines, and combine the subordinate lines and power flow transfer lines and mark them as associated lines. Step 2: Obtain all connected lines of the faulty risk line through the connected database, obtain all associated lines of the faulty risk line, combine all connected lines and all associated lines and delete duplicate lines to obtain the grid connection risk line.

5. The optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices according to claim 2, characterized in that: In the grid-connected line perception and assessment module, the operating status of all grid-connected risk lines is obtained, and a risk level is assigned to each line based on its operating status. Specifically: Step 1: Obtain the fault location time. Based on the fault location time, obtain the risk coefficient of all grid-connected risk lines and mark it as the location time risk coefficient. Based on the fault location time, obtain the risk coefficient of all grid-connected risk lines in the previous capture cycle and mark it as the location time risk coefficient. Step 2: Obtain the location risk coefficient fluctuation value by subtracting the location time risk coefficient from the location time risk coefficient. Determine whether the location risk coefficient fluctuation value of all grid-connected risk lines is less than 0. If the location risk coefficient fluctuation value of a grid-connected risk line is less than 0, mark the grid-connected risk line as a level 4 risk. If the location risk coefficient fluctuation value of a grid-connected risk line is equal to 0, mark the grid-connected risk line as a level 3 risk. If the location risk coefficient fluctuation value of a grid-connected risk line is greater than 0, proceed to Step 3. Step 3: Set a preset threshold for the risk coefficient fluctuation value, and determine whether the location risk coefficient fluctuation value of the grid-connected risk line is less than the preset threshold. If the location risk coefficient fluctuation value of the grid-connected risk line is less than or equal to the preset threshold, then the grid-connected risk line is marked as a level 2 risk. If the location risk coefficient fluctuation value of the grid-connected risk line is greater than the preset threshold, then the grid-connected risk line is marked as a level 1 risk.

6. The optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices according to claim 1, characterized in that: In the grid-connected line perception and assessment module, the system determines whether the off-grid islanding data adjustment module should be executed for grid-connected lines at risk based on the risk level. Specifically: Step 1: Determine whether the grid-connected risk line is a Level 1 or Level 2 risk. If the grid-connected risk line is a Level 1 or Level 2 risk, immediately execute the off-grid islanding data adjustment module on that line. If the grid-connected risk line is not a Level 1 or Level 2 risk, proceed to Step 2. Step 2: Obtain the current risk coefficient of the grid-connected risk line, obtain the risk coefficient of the fault location time of the grid-connected risk line, and determine whether the current risk coefficient is higher than the risk coefficient of the fault location time. If the current risk coefficient is higher than the risk coefficient of the fault location time, then increase the risk level of the grid-connected risk line by one level in the direction of high risk, and repeat Step 1. If the current risk coefficient is lower than or equal to the risk coefficient of the fault location time, then repeat Step 2.

7. The optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices according to claim 1, characterized in that: In the off-grid island data adjustment module, the adjustment difference is obtained based on the voltage, phase, and frequency of the main grid and the current off-grid island. Specifically, fault-risk lines and grid-connected risk lines are marked as lines to be adjusted. The voltage, phase, and frequency of the line to be adjusted in the main grid are obtained, as well as the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located. The voltage difference to be adjusted is obtained by subtracting the voltage of the line to be adjusted in the main grid from the voltage of the off-grid island in the area where the line to be adjusted is located. The phase difference to be adjusted is obtained by subtracting the phase of the line to be adjusted in the main grid from the phase of the off-grid island in the area where the line to be adjusted is located. The frequency difference to be adjusted is obtained by subtracting the frequency of the line to be adjusted in the main grid from the frequency of the off-grid island in the area where the line to be adjusted is located. The adjustment difference of the line to be adjusted is obtained by combining the voltage difference, phase difference, and frequency difference of the same line to be adjusted.

8. The optimized control system for rapid fault recovery in distribution networks based on low-voltage flexible interconnection devices according to claim 7, characterized in that: In the off-grid island data conditioning module, a conditioning strategy for the conditioning difference is formulated based on the risk level, and the voltage, phase, and frequency in the corresponding off-grid island are adjusted according to the conditioning strategy, specifically as follows: Step 1: Determine if the line to be adjusted is a fault-risk line. If it is, immediately adjust the adjustment differential of the line to make the voltage, phase, and frequency of the off-grid island in the area where the line is located consistent with the voltage, phase, and frequency of the line in the main grid. If the line to be adjusted is a grid-connected risk line, proceed to Step 2. Step 2: Determine the risk level of the line to be adjusted. If the risk level of the line to be adjusted is Level 1, immediately adjust the adjustment difference of the line to be adjusted so that the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located are consistent with the voltage, phase, and frequency of the line to be adjusted in the main grid. If the risk level of the line to be adjusted is Level 2, set an adjustment buffer interval time, immediately adjust the adjustment difference of the line to be adjusted by half, and after the adjustment buffer interval time ends, adjust the remaining adjustment difference of the line to be adjusted until the voltage, phase, and frequency of the off-grid island in the area where the line to be adjusted is located are consistent with the voltage, phase, and frequency of the line to be adjusted in the main grid.

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