Medium and low voltage flexible direct current interconnection scheduling method and system

Abstract

The invention provides a medium and low voltage flexible direct current interconnection scheduling method, and relates to the technical field of power distribution network scheduling, and the method comprises the steps: carrying out the feature weight correction of a first fault judgment result and a second fault judgment result according to a transient feature quantity, and obtaining the corrected fault positioning information; specific fault equipment is determined according to the corrected fault positioning information, and a fault token containing the available capacity of the specific fault equipment is generated; and obtaining a dynamic capacity boundary of the thermoelectric coupling constraint of the specific fault equipment, constructing a dynamic scheduling optimization model, and performing optimization scheduling on the specific fault equipment according to the dynamic scheduling optimization model. According to the method, the fault information is obtained through coupling backstepping and spectral decomposition, weight correction is carried out in combination with the transient characteristics in the current limiting mode, the fault token containing the available capacity is generated and participates in scheduling, unavailable equipment can be eliminated in time or participated in derating, and the power supply continuity of key loads is guaranteed.

Description

Technical Field

[0001] This application relates to the field of power distribution network dispatching technology, specifically to a medium- and low-voltage flexible DC interconnection dispatching method and system. Background Technology

[0002] With the increasing application of distributed power sources and flexible interconnection devices, medium and low voltage AC / DC hybrid systems are gradually adopting flexible DC interconnection and hierarchical scheduling. Existing solutions typically follow the main line of measurement to prediction and from prediction to rolling optimization, allocating power to low-voltage side energy storage, adjustable loads and converter devices, and feeding back power to the medium-voltage side through interconnection points when necessary to support local power supply and new energy consumption.

[0003] In actual operation, three types of phenomena still occur: First, after a short circuit or protection action occurs at the DC output, the dispatch results may still refer to equipment that is no longer available or whose status is uncertain for a period of time. This can lead to inconsistencies between the issued power commands and the actual execution on site, resulting in control deviations and affecting the continuity of local power supply.

[0004] Second, when the power is fed back from the connection point, it fails to synchronize with the voltage margin of the medium-voltage node, which can easily lead to the voltage on the medium-voltage side approaching the operating boundary or individual lines approaching heavy load, while the power generation of new energy sources on the low-voltage side is forced to be reduced.

[0005] Third, equipment capacity constraints are often handled as constant rated values. During emergency phases, the overload capacity that can be tolerated cannot be released within a short window. Subsequently, there is a lack of arrangements to match the load reduction and rollback, resulting in insufficient available scheduling margin or unstable recovery rhythm. Summary of the Invention

[0006] This application provides a method and system for scheduling medium and low voltage flexible DC interconnection, which aims to solve the problem of local power supply continuity being affected by short circuits or protection actions at the DC output in related technologies, solve the problem of failure to synchronize and coordinate with the voltage margin of medium voltage nodes, and avoid the problem of failing to release the tolerable overload capacity within a short time window during emergency phases.

[0007] To achieve the above objectives, this application provides a method for scheduling medium- and low-voltage flexible DC interconnection, comprising: The electrical parameters of the DC outlet and associated AC nodes are obtained. Coupled back-calculation is performed on the electrical parameters to obtain the first fault determination result. The electrical parameters are then subjected to spectral decomposition to obtain the second fault determination result. The difference between the first fault determination result and the second fault determination result is corrected to obtain preliminary fault location information.

[0008] Based on the preliminary fault location information, the device with the preliminary fault is identified. The device with the preliminary fault is then subjected to a current limiting mode. The transient characteristic quantities of the corresponding parameters under the current limiting mode are obtained. The first fault determination result and the second fault determination result are then corrected based on the transient characteristic quantities to obtain the corrected fault location information.

[0009] The specific faulty device is determined based on the corrected fault location information, and a fault token containing the available capacity of the specific faulty device is generated; the dynamic capacity boundary of the thermoelectric coupling constraint of the specific faulty device is obtained, a dynamic scheduling optimization model is constructed, and optimized scheduling is performed on the specific faulty device according to the dynamic scheduling optimization model.

[0010] The upper limit of the reverse power transmission at each flexible DC interconnection point is adjusted according to the dynamic capacity boundary and the voltage margin of the medium-voltage node. The DC voltage and power droop coefficient are optimized in conjunction with the controllable power flow. The instruction set is generated and issued synchronously to execute the coordinated transmission of controllable power flow.

[0011] Preferably, the electrical parameters of the DC outlet and associated AC nodes are obtained, and a coupled back-calculation is performed on the electrical parameters to obtain the first fault determination result, specifically including: The electrical parameters include: DC side voltage, DC side current, DC bus voltage, DC bus current, and phase voltage, phase current, phase angle, frequency, active power and reactive power of the associated AC nodes.

[0012] Based on electrical parameters, a set of node branch coupling equations is constructed from the DC outlet to the associated AC node. The set of node branch coupling equations includes DC-side power balance equations, AC-side power balance equations, and AC / DC power coupling constraint equations.

[0013] Substituting the electrical parameters into the node branch coupling equations, the power deviation vector and voltage deviation vector of each branch are obtained through least squares inversion and sensitivity matrix solution. The equivalent impedance change rate and equivalent conductance change rate of each branch are then calculated by combining the branch impedance matrix.

[0014] Based on the power deviation vector, voltage deviation vector, equivalent impedance change rate, and equivalent conductance change rate, the abnormal judgment conditions of the matching branch are determined, and combined with the time series characteristics of the deviation, the first fault judgment result is output. The first fault judgment result includes the fault branch number, the time of fault occurrence, the magnitude and direction of change of the fault electrical quantity, which is used to correct the difference with the second fault judgment result to obtain preliminary fault location information.

[0015] Preferably, the electrical parameters are subjected to spectral decomposition to obtain a second fault determination result, and the difference between the first fault determination result and the second fault determination result is corrected to obtain preliminary fault location information, specifically including: A time-domain signal sequence is constructed based on the DC-side voltage, DC-side current, DC bus voltage, DC bus current, and the phase voltage, phase current, phase angle, frequency, active power, and reactive power of the associated AC nodes. The time-domain signal sequence is then analyzed in the frequency domain and time-frequency domain using Fast Fourier Transform to extract the amplitude, phase, and energy distribution of harmonic components containing fault characteristics. A spectral feature vector is then constructed based on the extracted data.

[0016] The extracted spectral feature vector is compared component by component with the preset normal operating spectral reference vector to identify branches and nodes with abnormal spectral features. It is then determined whether the amplitude change rate, phase jump variable and harmonic energy threshold corresponding to the abnormal component meet the fault judgment conditions, thereby outputting a second fault judgment result. The second fault judgment result includes the suspected fault branch number, the corresponding spectral abnormality index and the time interval of the abnormality.

[0017] The difference correction includes: matching the results for the same branch number; when the branch numbers are consistent and the time difference of the fault occurrence does not exceed the preset time deviation threshold, the amplitude change direction and magnitude of the two judgment results are fused to form a weighted confidence level; when the branch numbers are inconsistent or the time difference exceeds the preset time deviation threshold, the larger product of the spectrum abnormal amplitude and the power deviation amplitude is selected as the dominant judgment result.

[0018] Preliminary fault location information is generated based on the difference correction results. The preliminary fault location information includes: fault branch number, electrical area to which the fault belongs, timestamp of the fault occurrence, confidence score, and information of adjacent nodes directly electrically coupled to the fault branch. This information is used to identify the initially faulty equipment and trigger the current limiting mode.

[0019] Preferably, the device with the initial fault is determined based on the preliminary fault location information, specifically including: Based on the fault branch number, electrical region to which the fault belongs, timestamp of the fault occurrence, confidence score, and adjacent node information in the preliminary fault location information, the equipment that is directly electrically coupled to the fault branch and has a confidence score not lower than the preset confidence threshold is matched in the preset electrical topology mapping table. The equipment includes the voltage source converter of the DC outlet, the DC bus, the DC branch, and the bus node on one side of the connected AC transformer. The equipment that meets the conditions is marked as the preliminary fault equipment.

[0020] Preferably, the device with the initial fault is subjected to a current-limiting mode, and the transient characteristic quantities of the corresponding parameters under the current-limiting mode are obtained, specifically including: A current-limiting control command is issued to the device with the initial fault, causing it to switch from a constant current output mode to a current-limiting mode. The current-limiting mode is an operating mode that limits the output current of the DC outlet to no more than the rated value, and simultaneously limits the active power output of the AC side of the device with the initial fault to no more than a certain percentage of the rated power, while keeping the reactive power reference value unchanged to maintain the stability of the AC side voltage. The current-limiting mode remains effective within a preset duration window to isolate fault impacts and collect dynamic response data during the current-limiting process.

[0021] In the current limiting mode, corresponding parameters are collected in real time. These parameters include the DC side current of the device with initial fault during the current limiting period, the DC bus voltage, the DC branch current, the phase current of the AC side, the phase voltage of the AC side, and the voltage imbalance of the DC bus relative to ground.

[0022] Transient features are extracted based on the corresponding parameters. These transient features include the decay time constant of the DC-side current, the recovery slope of the DC bus voltage, the distribution rate of change of the DC branch current, the change in the unbalance of the current in each phase of the AC side, the rate of change of the voltage unbalance of the DC bus relative to ground, and the drop amplitude of the AC-side voltage. These transient features are used to characterize the dynamic response characteristics of the device with the initial fault and its adjacent nodes under the current limiting mode after the fault impact, and provide input basis for subsequent feature weight correction of the first fault determination result and the second fault determination result.

[0023] Preferably, the first fault determination result and the second fault determination result are corrected by feature weighting based on transient feature quantities to obtain corrected fault location information, specifically including: A feature weight mapping relationship is established to correspond transient feature quantities with fault location tendency. The transient feature quantities include the decay time constant of DC side current, the recovery slope of DC bus voltage, the distribution change rate of DC branch current, the change in unbalance of AC side phase current, the change rate of DC bus voltage imbalance relative to ground, and the drop amplitude of AC side voltage. Each transient feature quantity is associated with three types of location tendency, namely converter outlet side tendency, DC branch middle tendency, and AC side near end tendency. The preset weights are then normalized.

[0024] Based on the timestamp of the preliminary fault location information, a time alignment window is set. The consistency coefficients of the first fault determination result and the second fault determination result with each transient characteristic quantity are calculated within the time alignment window. The consistency coefficients are determined according to the following rules: when the change direction and change amplitude of the transient characteristic quantity are completely consistent with the power deviation direction and amplitude level indicated by the corresponding determination result or exceed the preset consistency threshold, it is recorded as consistent; when only some characteristics meet or are insufficient to reach the consistency threshold, it is recorded as partially consistent; and all other cases are recorded as inconsistent.

[0025] Based on the feature weight mapping relationship and consistency coefficient, weighted confidence scores are calculated for the first fault determination result and the second fault determination result, respectively. The weighted confidence score is obtained by combining the preset benchmark confidence score, feature weights and consistency coefficients. When the two determination results point to the same branch or the same electrical area and the time difference does not exceed the preset time deviation threshold, they are fused to generate a fused confidence score by weighted averaging. When the two determination results point to different branches or different electrical areas or the time difference exceeds the preset time deviation threshold, the one with the higher weighted confidence score is selected as the dominant determination result, and its adjacent electrical connection relationship is used to supplement and form a candidate result set.

[0026] Conflict judgment is performed between the dominant judgment result and the candidate result set, and the target result that meets the following conditions is given priority: first, the highest fusion confidence; second, it is consistent with the combination of the shortest DC side current decay time constant, the largest DC bus voltage recovery slope, and the largest AC side voltage drop amplitude among transient characteristics; and third, it has the shortest path length directly connected to the fault branch in the electrical topology. If there are still ties, the one with the highest severity level is given priority.

[0027] Based on the target result, corrected fault location information is generated. The corrected fault location information includes: target fault branch number or target electrical area identifier, fault start time, fault type classification, severity level, final confidence score after fusion, list of adjacent nodes directly electrically connected to the target fault branch, suggested duration window for triggering current limiting, and available capacity estimation parameters for generating fault tokens. The corrected fault location information is used in subsequent steps to determine the specific faulty device and generate a fault token containing available capacity.

[0028] Preferably, the specific faulty device is determined based on the corrected fault location information, and a fault token containing the available capacity of the specific faulty device is generated, specifically including: The DC-side current decay time constant, DC bus voltage recovery slope, branch current distribution change rate, AC-side phase current imbalance change, DC bus-to-ground voltage imbalance change rate, and AC-side voltage drop amplitude are weighted and fused with their respective judgment features, and the corrected confidence value is calculated in combination with their original confidence values.

[0029] Based on the corrected confidence value, branches with confidence values ​​higher than the preset confidence threshold are selected, and corrected fault location information is generated, which includes the corrected fault branch number, the electrical area to which the fault belongs, the time of the fault occurrence, the corrected confidence score, and the information of adjacent nodes. This information is then used to determine the specific faulty device.

[0030] Preferably, the dynamic capacity boundary of the thermoelectric coupling constraint of the specific faulty equipment is obtained, a dynamic scheduling optimization model is constructed, and optimized scheduling is performed on the specific faulty equipment according to the dynamic scheduling optimization model, specifically including: Based on the specific type and operating status of the faulty equipment, and combined with thermoelectric coupling constraints, information on equipment temperature, load level, and operating duration is collected. The available capacity and allowable duration within different time windows are calculated to form a dynamic capacity boundary that changes over time, which is used to represent the capacity change pattern of the specific faulty equipment during short-term overload operation and subsequent load reduction and rollback.

[0031] Based on dynamic capacity boundaries, a dynamic scheduling optimization model is constructed that includes power balance constraints, voltage margin constraints, equipment thermoelectric coupling constraints, and power flow safety constraints. The joint optimization objectives are to reduce the risk of equipment thermal failure, maintain AC and DC voltage stability, and ensure continuous power transmission.

[0032] During the joint optimization solution process, the available capacity and operating time of specific faulty equipment, the reverse power transmission capability of adjacent flexible DC interconnection points, and the voltage margin of medium-voltage nodes are considered. The output allocation, power droop coefficient, and reactive power support strategy are adjusted iteratively.

[0033] Preferably, the upper limit of the reverse power transmission at each flexible DC interconnection point is adjusted according to the dynamic capacity boundary and the voltage margin of the medium-voltage node, and the DC voltage and power droop coefficient are optimized in conjunction with the adjustment. An instruction set is generated and issued synchronously to execute the coordinated transmission of controllable power flow, specifically including: The available reverse transmission capacity of each flexible DC interconnection point within the current time window is determined based on the dynamic capacity boundary, and verified according to the voltage margin of the medium-voltage node: if the voltage of any medium-voltage node is close to or exceeds the operating range under the predicted power flow, the reverse transmission capacity of the corresponding interconnection point is reduced by a preset ratio according to the voltage margin to obtain the corrected upper limit of reverse transmission power.

[0034] Under the aforementioned upper limit constraint, the target DC voltage value and power droop coefficient of each flexible DC interconnection point are optimized in a coordinated manner to ensure that the power allocation is consistent with the corrected upper limit of reverse power, and that the power flow is preferentially directed to the direction with sufficient voltage margin; an instruction set containing the corrected upper limit of reverse power, target DC voltage value, power droop coefficient, effective time and ramp limit is generated and issued synchronously.

[0035] After the data is distributed, closed-loop correction is performed based on the deviation between the measured value and the target. When the deviation exceeds the preset tolerance, the DC voltage target value and power droop coefficient are automatically adjusted according to the preset step size until the deviation returns to within the tolerance, and the coordinated transmission of controllable power flow is executed.

[0036] This application also provides a medium- and low-voltage flexible DC interconnection scheduling system, wherein the system is applied to the aforementioned medium- and low-voltage flexible DC interconnection scheduling method, comprising: The preliminary fault location unit is used to acquire the electrical parameters of the DC outlet and associated AC nodes, perform coupled back-calculation on the electrical parameters to obtain the first fault determination result, perform spectral decomposition on the electrical parameters to obtain the second fault determination result, and perform difference correction between the first fault determination result and the second fault determination result to obtain preliminary fault location information.

[0037] The correction positioning unit is used to determine the initially faulty device based on the initial fault positioning information, execute the initial faulty device in a current limiting mode, obtain the transient characteristic quantity of the corresponding parameter in the current limiting mode, and perform feature weight correction on the first fault judgment result and the second fault judgment result based on the transient characteristic quantity to obtain the corrected fault positioning information.

[0038] The optimization scheduling unit is used to determine the specific faulty device based on the corrected fault location information and generate a fault token containing the available capacity of the specific faulty device; obtain the dynamic capacity boundary of the thermoelectric coupling constraint of the specific faulty device, construct a dynamic scheduling optimization model, and perform optimized scheduling on the specific faulty device according to the dynamic scheduling optimization model.

[0039] The collaborative execution unit is used to adjust the upper limit of the reverse power transmission of each flexible DC interconnection point according to the dynamic capacity boundary and the voltage margin of the medium-voltage node, optimize the DC voltage and power droop coefficient in conjunction, generate instruction sets and issue them synchronously, and execute the collaborative transmission of controllable power flow.

[0040] The beneficial effects of this application are as follows: 1. This application obtains fault information through coupled back-reasoning and spectrum decomposition, combines it with transient characteristics under current limiting mode for weight correction, generates fault tokens containing available capacity and participates in scheduling, which enables unavailable equipment to be removed in time or participate in reduced capacity, the scheduling and field status to be quickly consistent, the control deviation to be significantly converged, and the power supply continuity of critical loads to be guaranteed.

[0041] 2. This application uses dynamic capacity boundary and medium-voltage node voltage margin to jointly correct the upper limit of reverse power of each flexible DC interconnection point, and optimizes DC voltage and power droop coefficient in conjunction, so that power flow prioritizes to the path with sufficient margin, which can suppress the medium-voltage side voltage approaching the boundary and the line approaching heavy load, while reducing unnecessary downsampling of low-voltage side renewable energy and increasing the acceptable power.

[0042] 3. This method introduces a dynamic capacity boundary based on thermoelectric coupling. In short-term emergency scenarios, it releases a moderate overload capacity according to the allowable duration and arranges load reduction and ramp-up restrictions in subsequent scheduling to achieve a short-term boost to a smooth fall-off operation trajectory. This improves the availability of scheduling and recovery stability without exceeding the equipment's load-bearing limits.

[0043] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 A flowchart of a medium- and low-voltage flexible DC interconnection scheduling method provided in this application embodiment.

[0046] Figure 2 This is an overall framework diagram of a medium- and low-voltage flexible DC interconnection scheduling system provided in an embodiment of this application. Detailed Implementation

[0047] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0048] Please refer to Figure 1 , Figure 1 A flowchart of a medium- and low-voltage flexible DC interconnection scheduling method provided in this application embodiment.

[0049] In this embodiment, a medium- and low-voltage flexible DC interconnection scheduling method includes steps S10, S20, S30 and S40, specifically including: Thus, a medium- and low-voltage flexible DC interconnection scheduling method is completed.

[0050] Step S10: Obtain the electrical parameters of the DC outlet and associated AC nodes; perform coupled back-calculation on the electrical parameters to obtain the first fault determination result; perform spectral decomposition on the electrical parameters to obtain the second fault determination result; and perform difference correction between the first and second fault determination results to obtain preliminary fault location information, specifically including: The electrical parameters include: DC side voltage, DC side current, DC bus voltage, DC bus current, and phase voltage, phase current, phase angle, frequency, active power and reactive power of the associated AC nodes.

[0051] It should be noted that the electrical parameters are synchronously acquired and output through DC voltage sensors and DC current sensors installed in the DC output circuit, and AC voltage transformers, AC current transformers, and phase measuring devices installed in the associated AC nodes.

[0052] Based on electrical parameters, a set of node branch coupling equations is constructed from the DC outlet to the associated AC node. The set of node branch coupling equations includes DC-side power balance equations, AC-side power balance equations, and AC / DC power coupling constraint equations.

[0053] It should be noted that the DC-side power balance equation is obtained by reading the DC bus voltage and DC-side current at the same sampling time, multiplying the two to obtain the DC-side active power at that time; the calculation result is used to check the energy conservation together with the subsequent AC / DC coupling constraints.

[0054] It should be noted that the AC power balance equation is to process the three phases of the associated AC node separately: take the voltage amplitude of each phase, the current amplitude of each phase, and the phase angle difference between the two, and take "voltage amplitude × current amplitude × cosine of phase angle difference" as the active power. The three phases are summed to obtain the AC active power; similarly, the reactive power can be obtained, which is used for network power balance and voltage verification.

[0055] It should be noted that the AC / DC power coupling constraint equation treats the converter as an energy channel that transfers DC power to the AC side. The transfer follows the equivalent efficiency coefficient: the active power on the AC side is equal to the active power on the DC side multiplied by the efficiency coefficient. The efficiency can be given according to the nominal range of the equipment and fine-tuned by online estimation. It is used to bind the power relationship between the DC side and the AC side together, while the reactive power is only independently controlled by capacity and voltage constraints.

[0056] Substituting the electrical parameters into the node branch coupling equations, the power deviation vector and voltage deviation vector of each branch are obtained through least squares inversion and sensitivity matrix solution. The equivalent impedance change rate and equivalent conductance change rate of each branch are then calculated by combining the branch impedance matrix.

[0057] Based on the power deviation vector, voltage deviation vector, equivalent impedance change rate, and equivalent conductance change rate, the abnormal judgment conditions of the matching branch are determined, and combined with the time series characteristics of the deviation, the first fault judgment result is output. The first fault judgment result includes the fault branch number, the time of fault occurrence, the magnitude and direction of change of the fault electrical quantity, which is used to correct the difference with the second fault judgment result to obtain preliminary fault location information.

[0058] A time-domain signal sequence is constructed based on the DC-side voltage, DC-side current, DC bus voltage, DC bus current, and the phase voltage, phase current, phase angle, frequency, active power, and reactive power of the associated AC nodes. The time-domain signal sequence is then analyzed in the frequency domain and time-frequency domain using Fast Fourier Transform to extract the amplitude, phase, and energy distribution of harmonic components containing fault characteristics. A spectral feature vector is then constructed based on the extracted data.

[0059] The extracted spectral feature vector is compared component by component with the preset normal operating spectral reference vector to identify branches and nodes with abnormal spectral features. It is then determined whether the amplitude change rate, phase jump variable and harmonic energy threshold corresponding to the abnormal component meet the fault judgment conditions, thereby outputting a second fault judgment result. The second fault judgment result includes the suspected fault branch number, the corresponding spectral abnormality index and the time interval of the abnormality.

[0060] It should be noted that, under normal operating conditions and with stable power flow, the preset normal operating frequency reference vector is collected for no less than 15 minutes, with a 1-second analysis window, excluding abnormal fluctuation windows; the frequency band conditions are set as follows: fundamental frequency and low harmonics (2nd–13th harmonics aggregated), intermediate frequency (100Hz–2kHz aggregated), and high frequency (2kHz–10kHz aggregated); each dimension is normalized to the fundamental frequency amplitude of this signal; and the mean of each dimension is taken as the "reference vector", with the standard deviation used for reference; the mean of high frequency DC is ≤3%, and the mean of low harmonic AC is ≤5%; the reference is updated regularly.

[0061] It should be noted that if two of the following three conditions are met, the current window spectrum is considered abnormal: The rate of change of amplitude is ≥50% higher than the benchmark in a certain dimension, and exceeds the benchmark plus three times the standard deviation.

[0062] Phase jump: The fundamental wave or lower harmonic changes by ≥10 degrees within two power frequency cycles.

[0063] Energy percentage: The energy percentage of medium frequency or high frequency reaches or exceeds 5%.

[0064] If the current window meets two of the above three conditions, the suspected fault branch number, abnormal indicators, and time interval will be output.

[0065] The difference correction includes: matching the results for the same branch number; when the branch numbers are consistent and the time difference of the fault occurrence does not exceed the preset time deviation threshold, the amplitude change direction and magnitude of the two judgment results are fused to form a weighted confidence level; when the branch numbers are inconsistent or the time difference exceeds the preset time deviation threshold, the larger product of the spectrum abnormal amplitude and the power deviation amplitude is selected as the dominant judgment result.

[0066] It should be noted that when the preset time deviation threshold setting window is 1 second and synchronization is at the millisecond level, the threshold is 20 milliseconds; 10–20 milliseconds on the DC side and 20–40 milliseconds on the AC side.

[0067] Preliminary fault location information is generated based on the difference correction results. The preliminary fault location information includes: fault branch number, electrical area to which the fault belongs, timestamp of the fault occurrence, confidence score, and information of adjacent nodes directly electrically coupled to the fault branch. This information is used to identify the initially faulty equipment and trigger the current limiting mode.

[0068] Step S20: Based on the preliminary fault location information, determine the initially faulty device, implement a current limiting mode on the initially faulty device, obtain the transient characteristic quantities of the corresponding parameters under the current limiting mode, and perform feature weight correction on the first fault determination result and the second fault determination result based on the transient characteristic quantities to obtain the corrected fault location information, specifically including: Based on the fault branch number, electrical region to which the fault belongs, timestamp of the fault occurrence, confidence score, and adjacent node information in the preliminary fault location information, the equipment that is directly electrically coupled to the fault branch and has a confidence score not lower than the preset confidence threshold is matched in the preset electrical topology mapping table. The equipment includes the voltage source converter of the DC outlet, the DC bus, the DC branch, and the bus node on one side of the connected AC transformer. The equipment that meets the conditions is marked as the preliminary fault equipment.

[0069] It should be noted that the preset electrical topology mapping table is a database of device-to-node and node-to-branch correspondences generated based on the current primary wiring and online switch configuration of the distribution network. It records the electrical area, connection terminals, adjacent nodes, connection direction, voltage level, and correspondence with converter ports and busbars according to the unique identifier of the equipment, and includes timestamps and consistency verification marks. This mapping table is jointly updated by the dispatching side model and field measurements and is used to quickly map faulty branches to the set of directly electrically coupled equipment.

[0070] It should be noted that the preset reliability threshold is the lower limit of the score used to screen for preliminary faulty devices. The value range is a dimensionless number between 0 and 1, with 0.7 as the default value. When the measurement noise is high or there are too many candidate devices, it is increased to 0.8. When the measurement redundancy is sufficient and the historical consistency is good, it is reduced to 0.6 to achieve a balance between stability and sensitivity between false alarms and false negatives.

[0071] A current-limiting control command is issued to the device with the initial fault, causing it to switch from a constant current output mode to a current-limiting mode. The current-limiting mode is an operating mode that limits the output current of the DC outlet to no more than the rated value, and simultaneously limits the active power output of the AC side of the device with the initial fault to no more than a certain percentage of the rated power, while keeping the reactive power reference value unchanged to maintain the stability of the AC side voltage. The current-limiting mode remains effective within a preset duration window to isolate fault impacts and collect dynamic response data during the current-limiting process.

[0072] It should be noted that the rated power limit ratio is the upper limit coefficient of the active power output on the AC side under current limiting mode. It is set as a percentage relative to the rated active power of the equipment, with a recommended range of 70% to 90% and a default value of 80%. When the voltage margin of the medium voltage node is insufficient, it will be automatically adjusted downward. When the voltage margin is sufficient and the dynamic capacity boundary allows, it will be adjusted upward appropriately, but it must not exceed the dynamic capacity boundary.

[0073] It should be noted that the reactive power reference value is a reactive power setting that remains unchanged during the current limiting mode. The value that is more conducive to maintaining the bus voltage within 95% to 105% of the rated value is taken from the average reactive power value in the analysis window before the fault occurs and the reactive power demand corresponding to the bus voltage target. This value does not change with active power adjustment during the current limiting duration.

[0074] It should be noted that the preset time window is a fixed duration for the rate limiting mode to maintain and collect data, used to fully capture the transient response after a fault. The range is set to 20 milliseconds to 50 milliseconds, with a default value of 30 milliseconds. The sampling period is aligned with an integer multiple of the sampling period and covers the minimum time length required for feature extraction.

[0075] In the current limiting mode, corresponding parameters are collected in real time. These parameters include the DC side current of the device with initial fault during the current limiting period, the DC bus voltage, the DC branch current, the phase current of the AC side, the phase voltage of the AC side, and the voltage imbalance of the DC bus relative to ground.

[0076] Transient features are extracted based on the corresponding parameters. These transient features include the decay time constant of the DC-side current, the recovery slope of the DC bus voltage, the distribution rate of change of the DC branch current, the change in the unbalance of the current in each phase of the AC side, the rate of change of the voltage unbalance of the DC bus relative to ground, and the drop amplitude of the AC-side voltage. These transient features are used to characterize the dynamic response characteristics of the device with the initial fault and its adjacent nodes under the current limiting mode after the fault impact, and provide input basis for subsequent feature weight correction of the first fault determination result and the second fault determination result.

[0077] A feature weight mapping relationship is established to correspond transient feature quantities with fault location tendency. The transient feature quantities include the decay time constant of DC side current, the recovery slope of DC bus voltage, the distribution change rate of DC branch current, the change in unbalance of AC side phase current, the change rate of DC bus voltage imbalance relative to ground, and the drop amplitude of AC side voltage. Each transient feature quantity is associated with three types of location tendency, namely converter outlet side tendency, DC branch middle tendency, and AC side near end tendency. The preset weights are then normalized.

[0078] Based on the timestamp of the preliminary fault location information, a time alignment window is set. The consistency coefficients of the first fault determination result and the second fault determination result with each transient characteristic quantity are calculated within the time alignment window. The consistency coefficients are determined according to the following rules: when the change direction and change amplitude of the transient characteristic quantity are completely consistent with the power deviation direction and amplitude level indicated by the corresponding determination result or exceed the preset consistency threshold, it is recorded as consistent; when only some characteristics meet or are insufficient to reach the consistency threshold, it is recorded as partially consistent; and all other cases are recorded as inconsistent.

[0079] Based on the feature weight mapping relationship and consistency coefficient, weighted confidence scores are calculated for the first fault determination result and the second fault determination result, respectively. The weighted confidence score is obtained by combining the preset benchmark confidence score, feature weights and consistency coefficients. When the two determination results point to the same branch or the same electrical area and the time difference does not exceed the preset time deviation threshold, they are fused to generate a fused confidence score by weighted averaging. When the two determination results point to different branches or different electrical areas or the time difference exceeds the preset time deviation threshold, the one with the higher weighted confidence score is selected as the dominant determination result, and its adjacent electrical connection relationship is used to supplement and form a candidate result set.

[0080] Conflict judgment is performed between the dominant judgment result and the candidate result set, and the target result that meets the following conditions is given priority: first, the highest fusion confidence; second, it is consistent with the combination of the shortest DC side current decay time constant, the largest DC bus voltage recovery slope, and the largest AC side voltage drop amplitude among transient characteristics; and third, it has the shortest path length directly connected to the fault branch in the electrical topology. If there are still ties, the one with the highest severity level is given priority.

[0081] It should be noted that the severity level is a classification result based on the corrected fault location information, and is scored by comprehensively considering the final confidence level, the number and magnitude of key transient features exceeding the limit, and the proportion of dynamic capacity boundary occupancy. When the final confidence level is not lower than 0.85 and at least two key features significantly exceed the limit or the expected derating exceeds 30% of the rated power, it is judged as a high level. When the final confidence level is between 0.7 and 0.85 or only one key feature exceeds the limit and the expected derating is between 10% and 30%, it is judged as a medium level. All other cases are judged as low level, which is used to determine the subsequent flow limiting duration and scheduling priority.

[0082] Based on the target result, corrected fault location information is generated. The corrected fault location information includes: target fault branch number or target electrical area identifier, fault start time, fault type classification, severity level, final confidence score after fusion, list of adjacent nodes directly electrically connected to the target fault branch, suggested duration window for triggering current limiting, and available capacity estimation parameters for generating fault tokens. The corrected fault location information is used in subsequent steps to determine the specific faulty device and generate a fault token containing available capacity.

[0083] Step S30: Determine the specific faulty device based on the corrected fault location information and generate a fault token containing the available capacity of the specific faulty device; obtain the dynamic capacity boundary of the thermoelectric coupling constraint of the specific faulty device, construct a dynamic scheduling optimization model, and perform optimized scheduling on the specific faulty device according to the dynamic scheduling optimization model, specifically including: The DC-side current decay time constant, DC bus voltage recovery slope, branch current distribution change rate, AC-side phase current imbalance change, DC bus-to-ground voltage imbalance change rate, and AC-side voltage drop amplitude are weighted and fused with their respective judgment features, and the corrected confidence value is calculated in combination with their original confidence values.

[0084] Based on the corrected confidence value, branches with confidence values ​​higher than the preset confidence threshold are selected, and corrected fault location information is generated, which includes the corrected fault branch number, the electrical area to which the fault belongs, the time of the fault occurrence, the corrected confidence score, and the information of adjacent nodes. This information is then used to determine the specific faulty device.

[0085] Based on the specific type and operating status of the faulty equipment, and combined with thermoelectric coupling constraints, information on equipment temperature, load level, and operating duration is collected. The available capacity and allowable duration within different time windows are calculated to form a dynamic capacity boundary that changes over time, which is used to represent the capacity change pattern of the specific faulty equipment during short-term overload operation and subsequent load reduction and rollback.

[0086] Based on dynamic capacity boundaries, a dynamic scheduling optimization model is constructed that includes power balance constraints, voltage margin constraints, equipment thermoelectric coupling constraints, and power flow safety constraints. The joint optimization objectives are to reduce the risk of equipment thermal failure, maintain AC and DC voltage stability, and ensure continuous power transmission.

[0087] During the joint optimization solution process, the available capacity and operating time of specific faulty equipment, the reverse power transmission capability of adjacent flexible DC interconnection points, and the voltage margin of medium-voltage nodes are considered. The output allocation, power droop coefficient, and reactive power support strategy are adjusted iteratively.

[0088] It should be noted that, based on the corrected fault location information, specific faulty devices are determined sequentially according to final confidence level, severity level, and electrical topology distance: priority is given to the converter or its DC branch that is directly electrically connected to the target faulty branch and has the highest confidence level; if there are ties, the one with the higher severity level and shorter path is selected; after determination, a fault token is generated, which specifies the device identifier, fault type, start time, available capacity and allowed duration, suggested derating ratio, whether current limiting needs to be maintained, a list and priority of adjacent cooperating devices, validity period, and refresh cycle. Available capacity is jointly given by the transient characteristics of current limiting and the dynamic capacity boundary: when the dynamic capacity boundary is insufficient to support the current power, the token will indicate that only derating is required and a recovery suggestion time will be given; when the boundary is below the safety threshold, isolation priority will be indicated for subsequent scheduling removal.

[0089] It should be noted that after obtaining the dynamic capacity boundary of a specific faulty device, a dynamic scheduling optimization model is constructed and optimized scheduling is executed: under constraints such as power balance, voltage margin, dynamic capacity boundary and power flow safety, the available capacity and duration of the specific faulty device, the reverse transmission capability of adjacent flexible DC interconnection points and the voltage margin of medium-voltage nodes are comprehensively considered to determine the active power, reactive power and DC voltage targets, power droop coefficient and output ramp-up limit; at the same time, support output and recovery time are allocated to adjacent cooperative devices to form an executable instruction set consistent with the fault token; the scheduling results are updated on a rolling basis and checked in a closed loop. If the measured deviation exceeds the tolerance or the thermal risk is still higher than the threshold, the output is automatically reduced and the recovery time is extended to ensure safe, continuous and controllable power flow transmission in medium and low voltage flexible DC interconnection scenarios.

[0090] Step S40: Based on the dynamic capacity boundary and the voltage margin of the medium-voltage node, adjust the upper limit of the reverse power transmission at each flexible DC interconnection point, optimize the DC voltage and power droop coefficient in a coordinated manner, generate an instruction set and issue it synchronously, and execute the coordinated transmission of controllable power flow, specifically including: The available reverse transmission capacity of each flexible DC interconnection point within the current time window is determined based on the dynamic capacity boundary, and verified according to the voltage margin of the medium-voltage node: if the voltage of any medium-voltage node is close to or exceeds the operating range under the predicted power flow, the reverse transmission capacity of the corresponding interconnection point is reduced by a preset ratio according to the voltage margin to obtain the corrected upper limit of reverse transmission power.

[0091] It should be noted that the preset ratio is set based on the voltage margin of the medium-voltage node: the allowable operating range of the rated voltage is 95% to 105%, and the voltage margin is defined as the percentage of the node voltage from the smaller of the above upper and lower limits. When the voltage margin is not less than 3%, no reduction is implemented, and the preset ratio is 0; when the voltage margin is between 1% and 3%, it is gradually reduced from 30% to 0 in a linear manner; when the voltage margin is not higher than 1%, enhanced reduction is implemented, with the preset ratio ranging from 50% to 80%, and the default being 70%; if an over-limit is predicted, the upper limit of the reverse power of the interconnection point is reduced to the emergency value, not exceeding 30% of its dynamic capacity boundary and not lower than the minimum output required for supply guarantee; to avoid oscillation, the upper limit adjustment range of a single cycle does not exceed 20% of the upper limit of the previous cycle.

[0092] Under the aforementioned upper limit constraint, the target DC voltage value and power droop coefficient of each flexible DC interconnection point are optimized in a coordinated manner to ensure that the power allocation is consistent with the corrected upper limit of reverse power, and that the power flow is preferentially directed to the direction with sufficient voltage margin; an instruction set containing the corrected upper limit of reverse power, target DC voltage value, power droop coefficient, effective time and ramp limit is generated and issued synchronously. After the data is distributed, closed-loop correction is performed based on the deviation between the measured value and the target. When the deviation exceeds the preset tolerance, the DC voltage target value and power droop coefficient are automatically adjusted according to the preset step size until the deviation returns to within the tolerance, and the coordinated transmission of controllable power flow is executed.

[0093] This completes a scheduling method for medium- and low-voltage flexible DC interconnection.

[0094] Please refer to Figure 2 , Figure 2 This is an overall framework diagram of a medium- and low-voltage flexible DC interconnection scheduling system provided in an embodiment of this application.

[0095] In this embodiment, a medium- and low-voltage flexible DC interconnection scheduling system includes: The preliminary fault location unit is used to acquire the electrical parameters of the DC outlet and associated AC nodes, perform coupled back-calculation on the electrical parameters to obtain the first fault determination result, perform spectral decomposition on the electrical parameters to obtain the second fault determination result, and perform difference correction between the first fault determination result and the second fault determination result to obtain preliminary fault location information.

[0096] The correction positioning unit is used to determine the initially faulty device based on the initial fault positioning information, execute the initial faulty device in a current limiting mode, obtain the transient characteristic quantity of the corresponding parameter in the current limiting mode, and perform feature weight correction on the first fault judgment result and the second fault judgment result based on the transient characteristic quantity to obtain the corrected fault positioning information.

[0097] The optimization scheduling unit is used to determine the specific faulty device based on the corrected fault location information and generate a fault token containing the available capacity of the specific faulty device; obtain the dynamic capacity boundary of the thermoelectric coupling constraint of the specific faulty device, construct a dynamic scheduling optimization model, and perform optimized scheduling on the specific faulty device according to the dynamic scheduling optimization model.

[0098] The collaborative execution unit is used to adjust the upper limit of the reverse power transmission of each flexible DC interconnection point according to the dynamic capacity boundary and the voltage margin of the medium-voltage node, optimize the DC voltage and power droop coefficient in conjunction, generate instruction sets and issue them synchronously, and execute the collaborative transmission of controllable power flow.

[0099] Thus, a medium- and low-voltage flexible DC interconnection and scheduling system has been completed.

[0100] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0101] Those skilled in the art will recognize that the algorithms or steps 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. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this application.

[0102] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations 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. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for scheduling of medium and low voltage flexible direct current interconnection, characterized in that, The method comprises the following steps: obtaining electrical parameters of a direct current outlet and associated alternating current nodes, performing coupled backstepping calculation on the electrical parameters to obtain a first fault determination result, performing frequency spectrum decomposition on the electrical parameters to obtain a second fault determination result, and correcting differences between the first fault determination result and the second fault determination result to obtain preliminary fault positioning information; determining a preliminary fault device according to the preliminary fault positioning information, executing a current limiting mode on the preliminary fault device, obtaining transient characteristic quantities of corresponding parameters in the current limiting mode, and correcting feature weights of the first fault determination result and the second fault determination result according to the transient characteristic quantities to obtain corrected fault positioning information; determining a specific fault device according to the corrected fault positioning information, and generating a fault token containing available capacity of the specific fault device; obtaining a dynamic capacity boundary of a thermal-electric coupling constraint of the specific fault device, constructing a dynamic scheduling optimization model, and executing optimized scheduling on the specific fault device according to the dynamic scheduling optimization model; correcting upper limits of reverse sending power of each flexible direct current interconnection point according to the dynamic capacity boundary and voltage margin of a medium voltage node, linking and optimizing direct current voltage and power droop coefficients, generating an instruction set for synchronous issuance, and executing coordinated transmission of controllable power flow.

2. The medium and low voltage VSC interconnection scheduling method of claim 1, wherein, obtaining electrical parameters of a direct current outlet and associated alternating current nodes, performing coupled backstepping calculation on the electrical parameters to obtain a first fault determination result, specifically comprising: the electrical parameters include direct current side voltage, direct current side current, direct current bus voltage, direct current bus current, and phase voltage, phase current, phase angle, frequency, active power and reactive power of the associated alternating current nodes; constructing a node branch coupling equation set from the direct current outlet to the associated alternating current nodes based on the electrical parameters, the node branch coupling equation set including a direct current side power balance equation, an alternating current side power balance equation, and an alternating current-direct current power coupling constraint equation; substituting the electrical parameters into the node branch coupling equation set, obtaining power deviation vectors and voltage deviation vectors of each branch through least square inversion and sensitivity matrix solving, and calculating equivalent impedance change rate and equivalent conductance change rate of each branch in combination with a branch impedance matrix; matching abnormal determination conditions of the branch according to the power deviation vectors, the voltage deviation vectors, the equivalent impedance change rate and the equivalent conductance change rate, and outputting the first fault determination result in combination with time sequence characteristics of the deviations; the first fault determination result includes fault branch number, fault occurrence time, fault electrical quantity change amplitude and change direction, and is used for subsequent difference correction with the second fault determination result to obtain preliminary fault positioning information.

3. The medium and low voltage VSC interconnection dispatching method of claim 2, wherein, performing frequency spectrum decomposition on the electrical parameters to obtain a second fault determination result, and correcting differences between the first fault determination result and the second fault determination result to obtain preliminary fault positioning information, specifically comprising: constructing a time domain signal sequence according to the direct current side voltage, the direct current side current, the direct current bus voltage, the direct current bus current, and the phase voltage, the phase current, the phase angle, the frequency, the active power and the reactive power of the associated alternating current nodes, performing frequency domain and time-frequency domain analysis on the time domain signal sequence by using fast Fourier transform, extracting harmonic component amplitude, phase and energy distribution containing fault characteristics, and constructing a frequency spectrum feature vector according to the extraction; The extracted spectrum feature vector is compared with a preset normal operation spectrum benchmark vector in each component, a branch and a node with spectrum feature anomaly are identified, whether the amplitude change rate, the phase jump amount and the harmonic energy threshold corresponding to the abnormal component meet the fault determination condition is judged, and a second fault determination result is output, the second fault determination result includes a suspected fault branch number, a corresponding spectrum anomaly index and a time interval of anomaly occurrence; The difference correction includes: matching the results of the same branch number, when the branch numbers are consistent and the fault occurrence time difference does not exceed a preset time deviation threshold, the amplitude change direction and the amplitude of the two determination results are fused to form a weighted confidence; when the branch numbers are inconsistent or the time difference exceeds the preset time deviation threshold, the product of the spectrum abnormal amplitude and the power deviation amplitude is selected as the dominant determination result; According to the difference correction result, preliminary fault positioning information is generated, the preliminary fault positioning information includes: fault branch number, fault belonging to electrical area, fault occurrence time stamp, confidence score and adjacent node information directly electrically coupled with the fault branch, which is used to determine the preliminary fault equipment and trigger the current limiting mode.

4. The medium and low voltage VSC interconnection dispatching method of claim 1, wherein, According to the preliminary fault positioning information, the preliminary fault equipment is determined, specifically including: According to the fault branch number, the fault belonging to electrical area, the fault occurrence time stamp, the confidence score and the adjacent node information in the preliminary fault positioning information, the devices directly electrically coupled with the fault branch and having a confidence score not lower than a preset confidence threshold are matched in a preset electrical topology mapping table, the devices include voltage source converters of direct current outlets, direct current buses, direct current branches and bus nodes on one side of alternating current transformers connected with the direct current branches, and the devices meeting the conditions are marked as preliminary fault equipment.

5. The medium and low voltage VSC interconnection dispatching method of claim 4, wherein, The preliminary fault equipment executes the current limiting mode to obtain transient characteristic quantities of corresponding parameters in the current limiting mode, specifically including: The current limiting control instruction is issued to the preliminary fault equipment to switch the preliminary fault equipment from the constant current output mode to the current limiting mode, the current limiting mode is an operation mode for limiting the output current of the direct current outlet to be not more than the rated value, and simultaneously limiting the active power output of the alternating current side of the preliminary fault equipment to be not more than the limited proportion of the rated power, while keeping the reactive power reference value unchanged to maintain the stability of the alternating current side voltage; the current limiting mode is valid within a preset duration window, which is used to isolate the fault impact and collect dynamic response data in the current limiting process; In the current limiting mode, the corresponding parameters are collected in real time, the corresponding parameters include the direct current side current, the direct current bus voltage, the direct current branch current, the alternating current side current, the alternating current side voltage and the voltage imbalance of the direct current bus relative to the ground of the preliminary fault equipment during the current limiting period; The transient characteristic quantity includes a decay time constant of a direct current side current, a recovery slope of a direct current bus voltage, a distribution change rate of a direct current branch current, an unbalance degree change amount of each phase current on an alternating current side, a voltage unbalance change rate of the direct current bus relative to the ground, and a drop amplitude of the alternating current side voltage; the transient characteristic quantity is used to depict dynamic response characteristics of the preliminary fault equipment and its adjacent nodes after a fault impact in the current limiting mode, and provides an input basis for subsequent feature weight correction of the first fault determination result and the second fault determination result.

6. The medium and low voltage VSC interconnection dispatching method of claim 5, wherein, The first fault determination result and the second fault determination result are corrected in feature weight according to the transient characteristic quantity, to obtain corrected fault positioning information, and the correction specifically includes: A feature weight mapping relationship is established to correspond the transient characteristic quantity and a fault position tendency relationship, the transient characteristic quantity includes a decay time constant of a direct current side current, a recovery slope of a direct current bus voltage, a distribution change rate of a direct current branch current, an unbalance degree change amount of each phase current on an alternating current side, a voltage unbalance change rate of the direct current bus relative to the ground, and a drop amplitude of the alternating current side voltage; wherein each item of the transient characteristic quantity is preset with a weight for each of three types of position tendencies, the three types of position tendencies include a converter outlet side tendency, a direct current branch middle part tendency, and an alternating current side near end tendency, and each preset weight is normalized; A time alignment window is set based on a time stamp of the preliminary fault positioning information, and a consistency coefficient of the first fault determination result and the second fault determination result with each transient characteristic quantity in the time alignment window is calculated, the consistency coefficient is determined according to the following rules: when the change direction and change amplitude of the transient characteristic quantity are completely consistent with or exceed a preset consistency threshold of the power deviation direction and amplitude level indicated by the corresponding determination result, it is recorded as consistent; when only part of the characteristics meet or are insufficient to meet the consistency threshold, it is recorded as partially consistent; otherwise, it is recorded as inconsistent; According to the feature weight mapping relationship and the consistency coefficient, a weighted confidence of the first fault determination result and the second fault determination result is calculated, the weighted confidence is obtained by combining a preset reference confidence, a feature weight and a consistency coefficient; when the two types of determination results point to the same branch or the same electrical region and the time difference does not exceed a preset time deviation threshold, a fusion confidence is generated by fusing in a weighted average manner; when the two types of determination results point to different branches or different electrical regions or the time difference exceeds the preset time deviation threshold, the one with a higher weighted confidence is selected as a dominant determination result, and a candidate result set is formed by supplementing the adjacent electrical connection relationship thereof; Conflict judgment is performed between the dominant determination result and the candidate result set, and a target result meeting the following conditions is preferentially selected: first, the fusion confidence is the highest; second, the combination of the shortest decay time constant of the direct current side current, the largest recovery slope of the direct current bus voltage, and the largest drop amplitude of the alternating current side voltage is consistent; third, the path length directly connected with the fault branch in the electrical topology is the shortest; if there are still parallel results, the one with the highest severity level is preferentially selected. The corrected fault location information includes a target fault branch number or a target electrical area identifier, a fault start time, a fault type classification, a severity level, a fused final confidence score, a list of adjacent nodes directly electrically connected to the target fault branch, a recommended duration window for triggering current limiting, and an available capacity estimation parameter for generating a fault token.

7. The medium and low voltage VSC interconnection dispatching method of claim 6, wherein, According to the corrected fault location information, a specific fault device is determined, and a fault token containing the available capacity of the specific fault device is generated, specifically including: The DC side current decay time constant, the DC bus voltage recovery slope, the branch current distribution change rate, the AC side phase current imbalance change amount, the DC bus voltage imbalance change rate, and the AC side voltage drop amplitude are respectively weighted and fused with the corresponding judgment characteristics, and the corrected confidence value is calculated in combination with the original confidence. According to the corrected confidence value, the branch with a confidence value higher than a preset confidence threshold is selected, and corrected fault location information containing the corrected fault branch number, the fault electrical area, the fault occurrence time, the corrected confidence score and the adjacent node information is generated, which is used for subsequent determination of the specific fault device.

8. The medium and low voltage VSC interconnection dispatching method of claim 7, wherein, The dynamic capacity boundary of the specific fault device thermal-electric coupling constraint is obtained, and a dynamic scheduling optimization model is constructed, and the specific fault device is executed according to the dynamic scheduling optimization model, specifically including: According to the type and operating state of the specific fault device, the device temperature, load level and running duration information are collected in combination with the thermal-electric coupling constraint condition, the available capacity and allowable duration in different time windows are calculated, and the dynamic capacity boundary changing with time is formed, which is used to represent the capacity change law of the specific fault device in the process of short-time overload operation and subsequent load reduction rollback; Based on the dynamic capacity boundary, a dynamic scheduling optimization model containing power balance constraint, voltage margin constraint, device thermal-electric coupling constraint and power flow safety constraint is constructed, and reducing the risk of device thermal failure, maintaining AC and DC voltage stability, and ensuring continuous power transmission are taken as joint optimization objectives; In the joint optimization solving process, the available capacity and running time of the specific fault device, the reverse power transmission capability of the adjacent flexible DC interconnection point and the voltage margin of the medium voltage node are considered, and the output distribution, power droop coefficient and reactive power support strategy are adjusted iteratively.

9. The medium and low voltage VSC interconnection dispatching method of claim 8, wherein, According to the dynamic capacity boundary and the medium voltage node voltage margin, the upper limit of the reverse power transmission of each flexible DC interconnection point is corrected, the DC voltage and the power droop coefficient are optimized in linkage, the instruction set is synchronously issued, and the coordinated transmission of controllable power flow is executed, specifically including: According to the dynamic capacity boundary, the available reverse power transmission capacity of each flexible DC interconnection point in the current time window is determined, and is verified according to the medium voltage node voltage margin: if the voltage of any medium voltage node is close to or exceeds the operating range under the predicted power flow, the reverse power transmission capacity of the corresponding interconnection point is reduced by a preset proportion according to the voltage margin, and the corrected reverse power transmission upper limit is obtained. Under the upper limit constraint, the DC voltage target value and the power droop coefficient of each HVDC interconnection point are optimized to make the power distribution consistent with the corrected upper limit of the reverse power flow, and the power flow preferentially flows to the direction with sufficient voltage margin; a command set containing the corrected upper limit of the reverse power flow, the DC voltage target value, the power droop coefficient, the effective time and the slope limit is generated and synchronously issued; After issuance, closed-loop correction is performed according to the deviation between the measured value and the target value, and when the deviation exceeds the preset tolerance, the DC voltage target value and the power droop coefficient are automatically adjusted by a preset step until the deviation is within the tolerance, and the coordinated transmission of controllable power flow is performed.

10. A medium and low voltage flexible direct current interconnection dispatching system, characterized in that, The system applies the medium and low voltage HVDC interconnection scheduling method in any one of claims 1-9, comprising: A preliminary fault location unit is configured to obtain electrical parameters of a DC outlet and associated AC nodes, perform coupling backstepping calculation on the electrical parameters to obtain a first fault determination result, perform frequency spectrum decomposition on the electrical parameters to obtain a second fault determination result, and correct the first fault determination result and the second fault determination result for differences to obtain preliminary fault location information; A correction location unit is configured to determine a preliminary fault device according to the preliminary fault location information, execute current limiting mode on the preliminary fault device, obtain transient characteristic quantities of corresponding parameters in the current limiting mode, and correct the first fault determination result and the second fault determination result for feature weights according to the transient characteristic quantities to obtain corrected fault location information; An optimization scheduling unit is configured to determine a specific fault device according to the corrected fault location information, and generate a fault token containing available capacity of the specific fault device; obtain a dynamic capacity boundary of a thermal-electric coupling constraint of the specific fault device, construct a dynamic scheduling optimization model, and execute optimization scheduling on the specific fault device according to the dynamic scheduling optimization model; A cooperative execution unit is configured to correct the upper limit of the reverse power flow of each HVDC interconnection point according to the dynamic capacity boundary and the voltage margin of the medium voltage node, to link and optimize the DC voltage and the power droop coefficient, to generate a command set and synchronously issue it, and to perform coordinated transmission of controllable power flow.

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