Fast commutation failure identification method and system for contingency set example

Abstract

A method and system for identifying fast commutation failure of a set of contingency cases, a fast hierarchical commutation failure identification method combining analytical and numerical simulation is adopted, for the first level fast commutation failure identification, the extinction angle or the critical voltage of the direct current which does not meet the commutation failure requirement but has subsequent commutation failure risk is analyzed, then numerical simulation is further carried out, according to the change of the extinction angle and the voltage, the second level hierarchical fast commutation failure identification analysis is carried out, at most four levels of fast commutation failure identification analysis is carried out, the coupling effect of the direct current control protection and the alternating current network is considered under the electromechanical simulation scale, the direct current which may have commutation failure within 4 cycles of the contingency occurrence is identified fast by hierarchical and segmental method with less numerical simulation iteration, so as to effectively consider the robustness of identification on the basis of fast commutation failure identification analysis.

Description

Technical Field

[0001] This invention relates to a fast commutation failure identification and analysis method and related device based on the fusion analysis of anticipated fault set examples and numerical simulation, belonging to the field of power system and its automation technology. Background Technology

[0002] With the vigorous development of large-scale renewable energy, the capacity of multi-infeed and multi-outfeed systems for large-scale renewable energy grid connection and long-distance transmission via ultra-high voltage direct current (UHVDC) is increasing daily. The complexity and variability of renewable energy control and protection systems, their wide control timescales, and the strong nonlinear and time-varying factors have led to a surge in the impact of commutation failures in AC / DC multi-infeed systems, severely restricting the operation of power systems. There is an urgent need to quickly identify whether commutation failures exist under anticipated fault set calculations, and which DC lines may experience commutation failures.

[0003] Traditional methods for identifying commutation failures using hypothetical fault sets primarily rely on obtaining the DC converter station's arc-extinguishing angle curve through complete numerical simulations, and then analyzing its presence (typically set to 7 degrees). The time-consuming nature of using complete numerical simulations to calculate the DC arc-extinguishing angle curve after a hypothetical fault disturbance limits the speed of commutation failure identification methods in large-scale AC / DC interconnected systems dominated by large-scale power electronic equipment. Furthermore, simple static analytical methods for identifying commutation failures fail to consider the nonlinear DC control characteristics and the subsequent commutation failures caused by the interaction and coupling of multiple DC circuits, thus compromising the accuracy and robustness of the analysis method. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a rapid commutation failure identification and analysis method and related apparatus that integrates analytical analysis of anticipated fault sets and numerical simulation, balancing speed and accuracy, and solving the problems disclosed in the background technology.

[0005] The present invention adopts the following technical solution.

[0006] The first aspect of the present invention provides a fast commutation failure identification method for a set of anticipated fault examples. The set of anticipated fault examples includes M anticipated fault examples of multi-infeed DC transmission systems, and the multi-infeed DC transmission systems include N DC subsystems. The fast commutation failure identification method includes the following steps:

[0007] For each example j, a two-layer fast commutation failure identification analysis is used to traverse all DC subsystems and determine whether DC subsystem i will experience commutation failure, j∈[1,M], i∈[1,N].

[0008] In the first-level fast commutation failure identification analysis, the critical voltage of commutation failure obtained by analysis, as well as the arc extinction angle, voltage and current simulated up to the set time, are used to identify and analyze whether there is a commutation failure in DC subsystem i. If the conclusion is that there is a commutation failure or there is no commutation failure, the commutation failure identification analysis of DC subsystem i for example j ends; if it is still uncertain whether there is a commutation failure, the second-level fast commutation failure identification analysis is entered.

[0009] In the second-level fast commutation failure identification analysis, based on the first-level fast commutation failure identification analysis, the simulation time period is increased step by step in K levels. Each level uses the arc extinction angle from the simulation to a set time to identify and analyze whether there is a commutation failure in DC subsystem i. If the conclusion is that there is a commutation failure, the commutation failure identification analysis of DC subsystem i for example j ends; otherwise, the arc extinction angle, voltage, and current from the simulation to the set time are used to identify and analyze whether there is a commutation failure in DC subsystem i. If there is a commutation failure, the commutation failure identification analysis of DC subsystem i for example j ends; otherwise, the simulation time period is increased, and the next level of identification analysis is entered until the last level is reached. The last level determines whether there is a commutation failure in DC subsystem i or not, based on the relationship between the simulated DC arc extinction angle and the critical arc extinction angle.

[0010] Preferably, in the first-level fast commutation failure identification analysis, the short-circuit voltage of the DC subsystem i converter station under the expected fault of the case j is obtained based on the numerical simulation at time 0+, and the arc extinction angle of the DC subsystem i converter station at time 0+ is obtained based on the numerical simulation. The DC subsystem i is determined to have commutation failure or uncertain to have commutation failure by criterion 1 or criterion 2.

[0011] Criterion 1: If the critical voltage for commutation failure is less than the short-circuit voltage and the arc extinction angle of the converter station is less than the critical arc extinction angle, then the DC subsystem i is determined to have commutation failure; otherwise, it is not yet certain that commutation failure exists.

[0012] Criterion 2: If the short-circuit voltage is less than the AC voltage when the arc extinction angle is equal to the critical arc extinction angle, calculated based on the DC current and DC control angle of the DC subsystem i converter station simulated at time 0+, then the DC subsystem i is determined to have commutation failure; otherwise, the existence of commutation failure is not yet determined.

[0013] Preferably, in the first-level fast commutation failure identification analysis, the short-circuit voltage of the DC subsystem i converter station under the expected fault of the case j is obtained based on the numerical simulation at time 0+, and the arc extinction angle, current and voltage of the DC subsystem i converter station at time 0+ are obtained based on the numerical simulation. The DC subsystem i is determined to have no commutation failure or is uncertain to have commutation failure by criteria 3, criterion 4 or criterion 5.

[0014] Criterion 3: If the short-circuit voltage is greater than the converter station voltage of DC subsystem i simulated at time 0+, and the arc extinction angle of the converter station is greater than the critical arc extinction angle, then DC subsystem i is determined to have no commutation failure and there is no need to enter the second layer of fast commutation failure identification and analysis.

[0015] Criterion 4: If the simulated DC arc extinction angle at time 0+ is less than the first set value ε1, and the voltage of the DC subsystem i converter station is greater than the short-circuit voltage U. i,f If the arc extinguishing angle of DC subsystem i is less than the first set value ε1, there is a risk of commutation failure in the future. It is necessary to enter the second layer of rapid commutation failure identification and analysis. Otherwise, it is determined that there is no commutation failure in the next 4 cycles.

[0016] Criterion 5: If the arc extinction angle γ of the DC subsystem i converter station simulated at time 0+ is less than the second set value ε2, and the DC current of DC subsystem i exceeds the steady-state current set ratio ε3, then the DC subsystem i is uncertain to have commutation failure, but there is a risk of commutation failure in the future, and it needs to enter the second layer of fast commutation failure identification analysis; otherwise, it is determined that there is no commutation failure.

[0017] Preferably, the multi-infeed DC transmission system is a layered DC system. If both the high valve and the low valve satisfy criterion 1 or criterion 2, then the DC subsystem i is determined to have a commutation failure; otherwise, the existence of a commutation failure is uncertain. If at least one of the high valve or the low valve satisfies any one of criterion 3 to criterion 5, then the existence of a commutation failure in the DC subsystem i is uncertain, and it needs to enter the second layer of fast commutation failure identification and analysis; otherwise, the existence of a commutation failure is determined to be non-existent.

[0018] Preferably, in the second-level fast commutation failure identification analysis, based on the converter station arc extinction angle obtained at the k-th level of numerical simulation and the minimum arc extinction angle within the DC integral step obtained from the DC subsystem i simulation at time 0+, the DC subsystem i is determined to have commutation failure or uncertain to have commutation failure by criterion 6 or criterion 7.

[0019] Criterion 6: If the arc extinction angle of the converter station obtained at time k in the numerical simulation is less than the critical arc extinction angle, then the DC subsystem i is determined to have commutation failure; otherwise, the existence of commutation failure is uncertain.

[0020] Criterion 7: If the minimum arc extinction angle obtained by the DC subsystem i in the DC integration step at time 0+ of the numerical simulation is less than the critical arc extinction angle, then the DC subsystem i is determined to have commutation failure; otherwise, it is uncertain whether commutation failure exists.

[0021] Where k∈[1,K].

[0022] Preferably, K=4, and the second-layer fast commutation failure identification and analysis is performed at most four levels;

[0023] The first level of analysis determines whether commutation failure will continue within one cycle after the fault occurs. The second level of analysis determines whether commutation failure will continue after 1.5 cycles after the fault occurs. The third level of analysis determines whether commutation failure will continue within 1.5 to 2.5 cycles. The fourth level of analysis determines whether commutation failure will continue within 3 to 4 cycles.

[0024] If there are still unidentified DC commutation failures after the second-level fourth-level analysis, then it is assumed that the DC will not experience commutation failure after passing through the anticipated fault disturbance.

[0025] Preferably, in the second-level fast commutation failure identification analysis, based on the arc extinction angle γ of the DC subsystem i converter station and the DC current of DC subsystem i obtained at the k-th time of the numerical simulation, the DC subsystem i is determined to have no commutation failure or to be uncertain about the existence of commutation failure by criteria 8, 9 or 10, and needs to enter the next level of identification analysis;

[0026] Criterion 8: If the arc extinction angle γ of the DC subsystem i converter station obtained at the k-th time of the numerical simulation is less than the first fixed value ε1 and the DC arc extinction angle under the DC integral step scale is less than the critical arc extinction angle, then the DC subsystem i is uncertain to have commutation failure and needs to enter the next level of identification and analysis; otherwise, it is determined that there is no commutation failure.

[0027] Criterion 9: If the arc extinction angle γ of DC subsystem i at time k of the numerical simulation is less than the second set value ε2, and the DC current of DC subsystem i exceeds the steady-state current set ratio ε3, then DC subsystem i is uncertain to have commutation failure and needs to enter the next level of identification and analysis; otherwise, it is determined that there is no commutation failure.

[0028] Criterion 10: If the difference between the arc extinction angle of DC subsystem i at time k of the numerical simulation and the arc extinction angle of DC subsystem i at time (k-1) of the numerical simulation is greater than the set value, then DC subsystem i is uncertain to have commutation failure and needs to enter the next level of identification and analysis; otherwise, it is determined that there is no commutation failure.

[0029] Where k∈[1,K].

[0030] Preferably, the multi-infeed DC transmission system is a layered DC system. If both the high valve and the low valve satisfy criterion 6 or criterion 7, then the DC subsystem i is determined to have commutation failure; otherwise, it is uncertain whether commutation failure exists. If at least one of the high valve or the low valve satisfies any one of criterion 8 to criterion 10, it is determined that the DC subsystem i is either determined not to have commutation failure or uncertain whether commutation failure exists, and it needs to proceed to the next level of identification and analysis.

[0031] Preferably, the first set value ε1 = 12 degrees;

[0032] The second set value ε2 = 13 degrees;

[0033] Set the ratio ε3 = 5%.

[0034] A second aspect of the present invention provides a fast commutation failure identification system based on a set of anticipated faults, wherein the fast commutation failure identification method based on the set of anticipated faults includes:

[0035] The first-level analysis module adopts a fast hierarchical commutation failure identification method that integrates analytical and numerical simulation. It obtains the critical voltage of commutation failure based on an approximate analytical method that considers the dynamic characteristics of DC current. It obtains the short-circuit voltage of each DC converter station under any expected fault through numerical simulation at time 0+. Based on the critical voltage of commutation failure and the magnitude of the short-circuit voltage of each DC converter station, and combined with the arc extinction angle of each DC converter station at time 0+ of the numerical simulation, the first-level fast commutation failure identification analysis is performed on the case.

[0036] The second-level hierarchical analysis module determines whether further partial numerical simulation is necessary to perform the next level of commutation failure identification analysis if no commutation failure occurred in the first-level rapid commutation failure identification analysis, based on the size of the arc extinction angle γ and the change of the arc extinction angle between the previous and next levels. In each level of operation, a small segment of numerical integration is added to obtain the arc extinction angle trajectory after the disturbance, based on the disturbed trajectory of the previous level of operation.

[0037] A third aspect of the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when loaded onto the processor, implements the aforementioned method for fast commutation failure identification of a set of anticipated faults.

[0038] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, characterized in that, when executed by a processor, the computer program implements the aforementioned method for fast commutation failure identification of a set of anticipated faults.

[0039] Compared with the prior art, the beneficial effects of the present invention include at least the following: by using a two-layer multi-level fusion analysis and a numerical integration method based on the actual power system model, the coupling effect of DC control protection and AC network is considered under the electromechanical simulation scale. With fewer numerical simulation iterations, the DC system that may fail to commutate within 4 cycles of the expected fault can be quickly identified in a hierarchical and segmented manner. This can take into account the strong nonlinear action response of the DC controller, as well as the strong coupling effect of the hierarchical DC high and low valves and the possible commutation failure phenomenon after the γ0 control action during the inverter side fault. Thus, the robustness of the identification is effectively taken into account on the basis of rapid commutation failure identification analysis.

[0040] Specifically, this invention employs a fast commutation failure identification and analysis method that integrates analytical and numerical simulation for the first layer of fast commutation failure identification and analysis. The arc extinction angle γ of the DC converter station at the simulated fault action time 0+ is used to verify γ < γ. set To supplement the analysis based solely on voltage U i,f <U ir The shortcomings of fast commutation failure identification. The first layer simultaneously satisfies U i,f <U ir And γ < γ set (usually γ) set If the angle is set to 7 degrees, then a commutation failure is determined for the DC current. Simultaneously, the deviation of the DC arc-extinguishing angle from its normal value (for the second layer, the deviation between the preceding and following stages) and the change in DC current are used to determine whether a second-level rapid commutation failure identification analysis is necessary.

[0041] If it is necessary to integrate the second-level hierarchical fast commutation failure identification analysis of some numerical simulations, in the multi-level operation, the disturbed trajectory of each level operation is further improved by adding some numerical integration to obtain the disturbed arc-extinguishing angle trajectory of the subsequent segment based on the previous level operation. The commutation failure (i.e., γ < γ) is then verified segment by segment in the disturbed arc-extinguishing angle trajectory of the subsequent segment. set (usually γ) set (Set to 7 degrees), and based on the deviation between the preceding and following stages and the change in DC current, it determines whether to perform rapid commutation failure identification analysis for the next stage. While ensuring the accuracy of the expected fault rapid commutation failure identification analysis, it also takes into account both speed and robustness. Attached Figure Description

[0042] Figure 1 Flowchart of a fast commutation failure identification and analysis method that integrates hypothetical fault set examples with numerical simulation;

[0043] Figure 2 The flowchart shows the fast commutation failure identification and analysis method for the DC subsystem in example j. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0045] like Figure 1As shown, Embodiment 1 of the present invention provides a fast commutation failure identification and analysis method for anticipated fault set examples, applicable to multi-infeed DC transmission systems. It is suitable for both single-layer and layered DC access methods. The multi-infeed DC transmission system includes N DC subsystems, where DC subsystem i represents the i-th DC subsystem of the multi-infeed DC transmission system, i = 1, 2, ..., N. The anticipated fault set includes M anticipated fault examples, where example j represents the j-th anticipated fault example, j = 1, 2, ..., M.

[0046] The fast commutation failure identification and analysis method is a fast commutation failure identification and analysis method that integrates analytical and numerical simulation methods. It includes: a first-level fast commutation failure identification and analysis that integrates analytical and numerical simulation methods, and a second-level hierarchical fast commutation failure identification and analysis that integrates partial numerical simulation based on changes in the arc extinction angle and voltage. Figure 2 As shown, starting from example 1, in each example j, the process begins with DC subsystem 1. If the first-level fast commutation failure identification analysis can determine whether DC subsystem i has a commutation failure or not, the judgment of DC subsystem i ends, and the judgment of DC subsystem (i+1) begins. If the first-level fast commutation failure identification analysis is still uncertain whether a commutation failure has occurred, the process enters the second-level hierarchical fast commutation failure identification analysis. After obtaining the conclusion that a commutation failure exists or does not exist, the judgment of DC subsystem i ends, and the judgment of DC subsystem (i+1) begins. In each example j, the process continues until DC subsystem N completes its judgment, and then the process enters example (j+1), ultimately completing all judgments for the M expected fault examples in the expected fault set.

[0047] Specifically, firstly, the critical voltage for commutation failure is obtained using an approximate analytical method considering the dynamic characteristics of DC current. Then, the short-circuit voltage of each DC converter station under any anticipated fault is obtained through numerical simulation at time 0+. Based on the critical voltage and short-circuit voltage of each DC converter station, and combined with the arc-extinguishing angle of each DC converter station at time 0+ (simulating fault action), a first-level rapid commutation failure identification analysis is performed. If the arc-extinguishing angle or voltage does not meet the requirements of the first-level rapid commutation failure identification analysis, further numerical simulation is conducted. Based on the changes in the arc-extinguishing angle and voltage, a second-level graded rapid commutation failure identification analysis is performed, up to a maximum of four levels of rapid commutation failure identification analysis. The second level primarily analyzes whether commutation failure will continue within one cycle after the fault occurs. The third level analyzes whether commutation failure will continue 1.5 cycles after the fault occurs. The fourth level analyzes whether commutation failure will continue 1.5 to 2.5 cycles after the fault occurs. If commutation failure is still not identified after the second level analysis, it is assumed that the DC will not experience commutation failure after the anticipated fault disturbance. Since each level, in addition to judging commutation failure based on voltage, also strictly adheres to the standard of judging commutation failure based on the arc extinction angle, verifying whether the arc extinction angle of each DC converter station meets the commutation failure conditions, the accuracy of commutation failure identification and analysis is improved. Whether to perform the second level of tiered commutation failure identification and analysis requires that the arc extinction angle decreases, the DC current slightly increases, or the AC voltage slightly recovers, avoiding scanning throughout the entire fault period to check if γ < γ. set This improves the speed of commutation failure identification.

[0048] In the various stages of the fast commutation failure identification analysis, a fusion analytical and numerical integration method based on the actual power system model is adopted. Under the electromechanical simulation scale, the coupling effects of DC control protection and AC network are considered. A smaller number of numerical simulation iterations are used to rapidly identify DC systems that may experience commutation failure within four cycles of the anticipated fault, thus effectively ensuring robustness in the fast commutation failure identification analysis. The second layer sets four levels of tracking up to four cycles of possible commutation failure, mainly considering the strong coupling effects of the layered DC high and low valves and the possibility of commutation failure after the γ0 control action during inverter-side faults.

[0049] More specifically, the first-level fast commutation failure identification analysis includes three parts in sequence: obtaining the critical voltage analysis value of commutation failure, the short-circuit voltage of each DC converter station, and the first-level fast commutation failure identification analysis.

[0050] Commutation failure threshold voltage U for each DC subsystem i ir The short-circuit voltage U of each DC subsystem i is obtained by approximating the DC dynamic process analytically. i,fBased on existing electromechanical simulation programs, numerical simulations were performed on example j up to time 0+; the commutation failure critical voltage U of DC subsystem i was obtained. ir Short-circuit voltage U i,f In addition, the numerical simulation of the expected fault specified in example j up to time 0+ (the time of simulated fault action) is used to perform rapid commutation failure identification analysis on the arc extinction angle γ of the DC converter station. The criteria used in the first layer of rapid commutation failure identification analysis include: commutation failure identification criteria that integrate analytical and numerical simulation results, as well as criteria that are not yet certain.

[0051] The commutation failure identification criteria that integrates analytical and numerical simulations include: if the commutation failure identification conditions of both analytical and numerical simulations are met, then the commutation failure identification criteria that integrate analytical and numerical simulations are met. The first layer directly outputs that there is a commutation failure in the DC subsystem, and the fast commutation failure identification analysis for the case j of the DC subsystem ends, and the fast commutation failure identification analysis for the next DC subsystem begins.

[0052] If the commutation failure identification criteria based on the fusion of analytical and numerical simulation are not met, the system will continue to determine whether the uncertain criteria are met. The uncertain criteria include: the tracking arc extinction angle γ and the DC current I. i The magnitude and changes of these parameters, such as, but not limited to, a decrease in the arc extinction angle, a slight increase in DC current, or a slight rebound in AC voltage, are considered. If the uncertain criterion is not met, the first layer directly outputs that there is no commutation failure in the DC subsystem, and the fast commutation failure identification and analysis for example j of the DC subsystem ends, and the process moves to the fast commutation failure identification and analysis for example j of the next DC subsystem. If the uncertain criterion is met, the first layer fast commutation failure identification and analysis for example j of the DC subsystem ends, and the process moves to the second layer graded fast commutation failure identification and analysis based on the numerical simulation of the fusion part of the arc extinction angle and voltage changes.

[0053] Understandably, for multi-infeed DC transmission systems, the fast identification of a case after the first-level fast commutation failure identification analysis includes two scenarios: first, all N DC subsystems meet the commutation failure identification criteria, and all N DC subsystems are determined to experience commutation failure; second, all N DC subsystems do not meet the uncertain criteria, and all N DC subsystems are determined not to experience commutation failure. Otherwise, for this case, a second-level hierarchical fast commutation failure identification analysis is performed on the DC subsystems that may experience commutation failure. The simulation continues to track possible commutation failure phenomena until the change in DC current or the change in arc extinction angle is small, or the maximum number of levels is reached, at which point the case ends.

[0054] It is worth noting that for layered DC, analysis is performed separately for high-valve and low-valve systems. If both the high-valve and low-valve systems simultaneously meet the commutation failure criteria, then a commutation failure is confirmed. If at least one of the high-valve or low-valve systems meets any one of the uncertain criteria, then it is uncertain whether a subsequent commutation failure will occur in DC subsystem i, and the system needs to proceed to the second-level rapid commutation failure identification analysis. Otherwise, it is determined that no commutation failure will occur within the next 4 cycles.

[0055] In a preferred but non-limiting embodiment of the present invention, the first-layer fast commutation failure identification analysis that integrates analytical and numerical simulation specifically includes:

[0056] Step 1: First, consider the DC dynamic process approximately and analytically calculate the commutation failure critical voltage U for each DC subsystem i. ir Value. Those skilled in the art can calculate the commutation failure critical voltage U using any known method. ir Values, for example, but not limited to, the calculation method disclosed in Chinese patent application CN202210481264.8.

[0057] Step 2: Based on existing electromechanical simulation programs, obtain the short-circuit voltage U of each DC subsystem i under any anticipated fault at time 0+ through numerical simulation. i,f .

[0058] Step 3: Arbitrarily selected anticipated faults from the anticipated fault set are simulated through numerical simulation to obtain the arc extinction angle γ of the DC converter station at time 0+. For all DC converters, the critical voltage U is then used as the basis for the simulation. ir The short-circuit voltage U of the DC converter station i,f Perform rapid commutation failure identification and analysis.

[0059] Step 4: If the commutation failure identification conditions of both analytical and numerical simulation are met, then the commutation failure identification criterion combining analytical and numerical simulation is satisfied. The first layer directly outputs that the DC subsystem has a commutation failure. The rapid identification of the case for DC subsystem i ends. The commutation failure identification criterion combining analytical and numerical simulation is expressed by the following formula:

[0060] U i,f <U ir And γ < γ set (1)

[0061] In the formula:

[0062] U ir This is the critical voltage for commutation failure.

[0063] U i,f This refers to the short-circuit voltage of the DC converter station.

[0064] γ is the extinguishing arc angle;

[0065] γ set The critical arc-extinguishing angle is preferably 7 degrees.

[0066] It is worth noting that, for stratified DC circuits analyzed separately according to high valve and low valve, both high valve and low valve must simultaneously meet the above constraints, otherwise commutation failure may occur.

[0067] Step 5: Track the arc extinction angle γ and DC current I. i The size and its changes determine whether to perform the second-level commutation failure identification. If the following criteria (2) or (3) are met, it is still uncertain whether the DC has failed to commutate. Further second-level fast commutation failure identification analysis is required, and the minimum arc-extinguishing angle of the DC simulation within the DC integral step obtained at time 0+ of the simulated fault action is saved. If the following criteria (2) or (3) are not met, there is no commutation failure within the subsequent 4 cycles. The fast identification of the case for DC subsystem i ends. The uncertain criteria are expressed by the following formula:

[0068] γ<ε1 and U i >U i,f (2)

[0069] γ<ε2 and I i >(1+ε3)I stable (3)

[0070] In the formula:

[0071] ε1 is a first set value, preferably but not limited to 12 degrees;

[0072] ε2 is a second set value, preferably but not limited to 13 degrees;

[0073] ε2 is a third set value, preferably but not limited to 5%;

[0074] U i For the converter bus i voltage, U i,f This refers to the short-circuit voltage of the DC converter station.

[0075] I i For the DC current of the converter bus i, I stable It is the steady-state DC current.

[0076] It is understandable that the specific meaning of the above steps is that, if it is still uncertain whether the arc extinction angle is decreasing, the DC current is slightly increasing, or the AC voltage is slightly rising, then the arc extinction angle γ and the DC current I are being monitored. i The magnitude and changes of the DC arc-extinguishing angle γ determine whether to proceed with the next stage of commutation failure identification. If the DC arc-extinguishing angle γ is less than the second set value ε2 (e.g., 13 degrees) and the DC current exceeds the third set ratio ε3 of the steady-state current (e.g., 5%), or if the DC arc-extinguishing angle γ is less than the first set value ε1 (e.g., 12 degrees) and the converter station voltage is greater than U during simulation...i,f Considering that the DC arc-extinguishing angle may be further reduced in the subsequent DC control, it is still uncertain whether the DC commutation has failed. However, the arc-extinguishing angle of the DC subsystem i has decreased significantly, and there is a large risk of subsequent commutation failure. Further analysis of the second-level rapid commutation failure identification is required.

[0077] Step 6: If none of the DC subsystems i in the multi-feed DC transmission system require the second-level fast commutation failure identification analysis, then all DC subsystems i in this example either do not have DC commutation failures or all have commutation failures, and the fast commutation failure identification analysis of the example ends.

[0078] Understandably, for a given example, if all N DC subsystems of a multi-infeed DC transmission system have reached a clear conclusion at the first level—either commutation failure exists or commutation failure is highly unlikely due to small DC current changes (arc extinction angle)—then the rapid commutation failure identification for that example is essentially complete. If no clear conclusion is reached for some DC subsystems at the first level, then those DC subsystems with unclear conclusions in the example need to undergo a second level of identification.

[0079] The second-level hierarchical fast commutation failure identification and analysis, which integrates numerical simulation, adopts a multi-level fast commutation failure identification and analysis approach with progressively increasing simulation periods. In each level, the arc-extinguishing angle γ is used as the criterion for determining commutation failure, and it is determined whether to proceed to the next level of fast commutation failure identification and analysis. If, after the last level of analysis in the second layer, there are still DC currents that have not been identified as having commutation failure, then it is assumed that the DC current will not experience commutation failure after passing through the anticipated fault disturbance, and the fast commutation failure identification and analysis process of the example ends.

[0080] Specifically, in the multi-level fast commutation failure identification operation, the process of each level is as follows: numerical simulation is performed to the corresponding examination time set in advance for each level, and the DC arc-extinguishing angle disturbance trajectory of the power system during that time period under the expected fault is obtained. Based on the arc-extinguishing angle disturbance trajectory, the second-level commutation failure identification analysis is performed on the expected fault. If the second-level DC arc-extinguishing angle does not meet the commutation failure condition, but meets the condition for further fast commutation failure identification analysis at the next level, then the next level operation is performed. If the multi-level operation reaches the preset maximum number of levels, or the arc-extinguishing angle of a certain level in the second level meets the commutation failure condition, then the multi-level operation is exited.

[0081] Preferably, as one of the prominent substantive features of this invention, considering the strong coupling effect of the layered DC high and low valves and the possibility of commutation failure after the γ0 control action during inverter-side faults, a maximum of four levels of rapid commutation failure identification analysis are performed. The first level mainly analyzes whether commutation failure will continue within one cycle after the fault occurs; the second level mainly analyzes whether commutation failure will continue 1.5 cycles after the fault occurs; the third level mainly analyzes whether commutation failure will continue within 1.5 to 2.5 cycles; and the fourth level mainly analyzes whether commutation failure will continue within 3 to 4 cycles. For DCs that have not yet experienced commutation failure in the first three levels, it should be determined whether it is necessary to continue partial numerical simulation for the next level of rapid commutation failure identification analysis. Simulation continues until the corresponding examination time of each level. If the simulated DC arc extinction angle is less than the critical arc extinction angle at this time, then commutation failure exists in the DC. If there are still DCs that have not been identified as having commutation failure after the second level of four-stage analysis, then it is assumed that the DC will not experience commutation failure after the expected fault disturbance, and the rapid commutation failure identification analysis process of the example ends.

[0082] Preferably, each stage is based on the magnitude of the DC arc extinction angle γ at the simulation time and γ set (usually γ) set Commutation failure identification is performed using a setting of 7 degrees. For DC circuits that have not experienced commutation failure, the necessity for further partial numerical simulation to identify and analyze commutation failure at the next level is determined based on the magnitude of the arc extinction angle γ and the change in the arc extinction angle between preceding and following levels.

[0083] Because the first level of analysis, in addition to judging commutation failure based on voltage, also strictly uses the arc-extinguishing angle as a criterion for judging commutation failure, it verifies whether the arc-extinguishing angle of each DC converter station meets the commutation failure conditions, thus improving the accuracy of commutation failure identification and analysis. Whether to perform the second level of tiered commutation failure identification and analysis requires that the arc-extinguishing angle decrease, the DC current slightly increase, or the AC voltage slightly recover, avoiding the need to scan and search for whether γ < γ throughout the entire fault period. set This improves the speed of commutation failure identification.

[0084] In the fast commutation failure identification and analysis, a fusion analysis and numerical integration method based on the actual power system model are adopted. The coupling effect of DC control protection and AC network is taken into account under the electromechanical simulation scale. A small number of numerical simulation iterations are used to quickly identify DC commutation failures that may occur within 4 cycles of the expected fault occurrence in stages. Thus, the robustness of the identification is effectively taken into account on the basis of fast commutation failure identification and analysis.

[0085] In a further preferred embodiment, the second layer first level mainly analyzes whether commutation failure will continue within one cycle after the fault occurs, and determines whether it is necessary for the DC subsystem that has not yet experienced commutation failure to continue partial numerical simulation for the next level of rapid commutation failure identification analysis.

[0086] For DC systems that have not yet experienced commutation failure, the magnitude of the DC extinction angle γ at the simulation up to the 1st cycle (including the minimum DC extinction angle under both electromechanical and DC integral step scales) and γ set (usually γ) set Commutation failure identification is performed by setting the degree to 7.

[0087] For conventional DC:

[0088] If γ < γ set (usually γ) set If we set the angle to 7 degrees, then the first stage of the second layer of the DC circuit exhibits commutation failure. Specifically, if the simulated DC arc-extinguishing angle is less than the critical arc-extinguishing angle at the 1st cycle of the simulation, or if the simulated DC arc-extinguishing angle within the DC integration step is less than the critical arc-extinguishing angle and the minimum simulated arc-extinguishing angle saved at time 0+ is less than the critical arc-extinguishing angle, then the DC circuit exhibits commutation failure. It is worth noting that due to the small time scale of DC, different simulation step sizes should be used for AC and DC in electromechanical simulations to track the changes in the DC arc-extinguishing angle at both the electromechanical scale and the DC integration step scale, especially the minimum value at the DC scale.

[0089] Otherwise, if the DC arc extinction angle is less than the set value ε1 and the simulated converter station voltage is greater than U... i,f If the DC current exceeds a certain ratio ε3 (e.g., 5%) of the steady-state current, or the arc extinction angle is less than a certain set value ε2 (e.g., 13 degrees) and the DC arc extinction angle under the DC integral step scale is less than a certain set value, then the DC needs to continue partial simulation to perform the next stage of fast commutation failure identification analysis.

[0090] For layered DC:

[0091] If the DC extinction angles of both the high-voltage valve and the low-voltage valve satisfy γ < γ set (usually γ) set If the degree is set to 7, then the first stage of the second layer of the DC circuit has a commutation failure.

[0092] If the DC arc-extinguishing angle of the high valve or low valve is less than the set value ε1 and the simulated converter station voltage is greater than U... i,f Furthermore, if the DC current exceeds a certain ratio ε3 (e.g., 5%) of the steady-state current, then the second layer of DC current needs to continue partial simulation to identify and analyze the failure of the next stage of rapid commutation.

[0093] If no commutation failure has occurred in the current stage of DC circuitry, there is no need to perform the next stage of fast commutation failure identification analysis; the fast commutation failure identification analysis process for the example ends. Otherwise, the AC iteration count is set to 7, and the next stage of fast commutation failure identification analysis is performed. It is worth noting that setting the AC iteration count to 7 uses the convergent solution of the approximate simulation iteration as the identification criterion to improve speed. The iterative solution of the differential-algebraic equations under the electromechanical scale is performed in the AC iteration process.

[0094] The second level of the second layer mainly analyzes whether commutation failure will continue 1.5 cycles after the fault occurs, and determines whether it is necessary to continue partial numerical simulation for the next level of rapid commutation failure identification analysis for DC subsystems that have not yet experienced commutation failure.

[0095] For DC systems that have not yet experienced commutation failure, the magnitude of the DC extinction angle γ (including the minimum DC extinction angle under both electromechanical and DC integral step scales) and γ are calculated based on the simulation up to the 1.5th cycle. set (usually γ) set Commutation failure identification is performed by setting the degree to 7.

[0096] For conventional DC:

[0097] If γ < γ set (usually γ) set If the degree is set to 7, then the second stage of the second layer of the DC circuit has a commutation failure.

[0098] Otherwise, if the DC arc extinction angle is less than a certain set value ε2 or the difference in arc extinction angle between the preceding and following levels is greater than the set value, then the DC needs to continue partial simulation to identify and analyze the failure of the next level of rapid commutation.

[0099] For layered DC:

[0100] If the DC extinction angles of both the high-voltage valve and the low-voltage valve satisfy γ < γ set (usually γ) set If the degree is set to 7, then the second stage of the second layer of the DC circuit has a commutation failure.

[0101] If no commutation failure has occurred in the current stage of DC circuitry, there is no need to perform the next stage of fast commutation failure identification analysis; the fast commutation failure identification analysis process for the example ends. Otherwise, set the AC iteration count to 7 and perform the next stage of fast commutation failure identification analysis.

[0102] The second and third levels mainly analyze whether commutation failure will continue within 1.5 to 2.5 cycles, and determine whether it is necessary to continue partial numerical simulation for the next level of rapid commutation failure identification analysis for DC subsystems that have not yet experienced commutation failure.

[0103] For DC systems that have not yet experienced commutation failure, the magnitude of the DC extinction angle γ (including the minimum DC extinction angle under both electromechanical and DC integral step scales) and γ are calculated based on the simulation up to the 2.5th cycle. set (usually γ) set Commutation failure identification is performed by setting the degree to 7.

[0104] For conventional DC:

[0105] If γ < γ set (usually γ) setIf the degree is set to 7, then the second stage of the DC second layer has a commutation failure.

[0106] Otherwise, if the DC arc extinction angle is less than a certain set value ε2 or the difference in arc extinction angle between the preceding and following levels is greater than the set value, then the DC needs to continue partial simulation to identify and analyze the failure of the next level of rapid commutation.

[0107] For layered DC:

[0108] If the DC extinction angles of both the high-voltage valve and the low-voltage valve satisfy γ < γ set (usually γ) set If the degree is set to 7, then the second stage of the DC second layer has a commutation failure.

[0109] If the difference in arc extinction angle between the high valve or low valve stages is greater than the set value, the second DC stage needs to continue partial simulation to identify and analyze the failure of the next stage of rapid commutation.

[0110] If no commutation failure has occurred in the current stage of DC circuitry, there is no need to perform the next stage of fast commutation failure identification analysis; the fast commutation failure identification analysis process for the example ends. Otherwise, set the AC iteration count to 7 and perform the next stage of fast commutation failure identification analysis.

[0111] The second layer, fourth level, mainly analyzes whether commutation failure will continue within 3 to 4 cycles; otherwise, the rapid commutation failure identification and analysis process of the case ends.

[0112] For DC systems that have not yet experienced commutation failure, the magnitude of the DC extinction angle γ at the 4th cycle simulation time (including the minimum DC extinction angle under both electromechanical and DC integral step scales) and γ set (usually γ) set Commutation failure identification is performed by setting the degree to 7.

[0113] For conventional DC:

[0114] If γ < γ set (usually γ) set If the degree is set to 7 degrees, then the fourth stage of the second layer of the DC circuit has a commutation failure.

[0115] For layered DC:

[0116] If the DC extinction angles of both the high-voltage valve and the low-voltage valve satisfy γ < γ set (usually γ) set If the degree is set to 7 degrees, then the fourth stage of the second layer of the DC circuit has a commutation failure.

[0117] In a preferred but non-limiting embodiment of the present invention, the second-layer fast commutation failure identification and analysis is performed according to the following steps:

[0118] Step 7: Proceed to the second-level fusion part of the numerical simulation for rapid commutation failure identification and analysis. Each level is based on the magnitude of the DC arc extinction angle γ at the simulation time and γ set (usually γ) set Commutation failure identification is performed at a set angle of 7 degrees. For DC circuits without commutation failure, the necessity for further partial numerical simulation to identify the next level of commutation failure is determined based on the magnitude of the arc extinction angle γ and the change in the arc extinction angle between preceding and following levels. Considering the strong coupling effect of the layered DC high and low valves and the possibility of commutation failure after the γ0 control action during inverter-side faults, a maximum of four levels of rapid commutation failure identification analysis are performed.

[0119] Step 8: Initially k=1, perform the k-th level fast commutation failure identification analysis. The k-th level mainly analyzes whether commutation failure will continue within a certain period after the fault occurs (k=1 is 1 cycle, k=2 is 1.5 cycles, k=3 is 2.5 cycles, k=4 is 4 cycles), and determines whether it is necessary to continue partial numerical simulation for the next level of fast commutation failure identification analysis for DC systems that have not yet experienced commutation failure. First, simulate a short period based on the k value (k=1 is 1 cycle, k=2 is 1.5 cycles, k=3 is 2.5 cycles, k=4 is 4 cycles) to obtain the DC arc extinction angle γ at the simulation time (including the minimum DC arc extinction angle under electromechanical scale and DC integral step scale).

[0120] Step 9, for conventional DC, if γ < γ set (usually γ) set (Set to 7 degrees), or for layered DC, if the DC extinguishing angles of both the high and low valves satisfy γ < γ set (usually γ) set If the degree is set to 7, then the kth stage of the second layer of this DC has a commutation failure. If all DCs in this stage have been confirmed to have had commutation failures, then the fast commutation failure identification and analysis process of the example ends.

[0121] Step 10: If the DC commutation failure has not yet occurred at this stage, and the following conditions are met: the DC arc extinction angle is less than the set value ε1 and the simulated converter station voltage is greater than U... i,f Furthermore, if the DC current exceeds a certain ratio ε3 (e.g., 5%) of the steady-state current, or if the arc extinction angle is less than a certain set value ε2 and the DC arc extinction angle under the DC integral step scale is less than a certain set value, and if the DC arc extinction angle of the high valve or low valve is less than the set value ε1 and the simulated converter station voltage is greater than U... i,f If the DC current exceeds a certain ratio ε3 (e.g., 5%) of the steady-state current, then the DC current needs to continue partial simulation to perform the next stage of fast commutation failure identification analysis, and proceed to step 11.

[0122] Step 11: If k is less than 4, proceed to step 12; otherwise, if k = 4, and there are still DCs that have not been identified after the second layer analysis at level k = 4, then it is assumed that the DCs will not experience commutation failure after passing the anticipated fault disturbance, and the fast commutation failure identification and analysis process of the example ends.

[0123] Step 12, then k = k + 1, proceed to step 8, and enter the next level of analysis.

[0124] Embodiment 2 of the present invention provides a device for rapid identification and analysis of anticipated fault commutation failure, characterized in that it includes:

[0125] The first-level analysis module adopts a fast hierarchical commutation failure identification method that integrates analytical and numerical simulation. It obtains the critical voltage of commutation failure based on an approximate analytical method that considers the dynamic characteristics of DC current. It obtains the short-circuit voltage of each DC converter station under any expected fault through numerical simulation at time 0+. Based on the critical voltage of commutation failure and the magnitude of the short-circuit voltage of each DC converter station, and combined with the arc extinction angle of each DC converter station at time 0+ (simulating fault action) of numerical simulation, the first-level fast commutation failure identification analysis is performed on the case.

[0126] The second-level hierarchical analysis module, if no commutation failure occurred in the first-level rapid commutation failure identification analysis for DC, determines whether further partial numerical simulation is necessary for the next level of commutation failure identification analysis based on the size of the arc-extinguishing angle and the change in the arc-extinguishing angle between preceding and following levels. In this case, a second-level hierarchical multi-level analysis operation is adopted. The process for each level is as follows: commutation failure identification is performed based on the size of the DC arc-extinguishing angle at the simulation time (usually set to 7 degrees). For DCs that did not experience commutation failure, the necessity for further partial numerical simulation for the next level of commutation failure identification analysis is determined based on the size of the arc-extinguishing angle and the change in the arc-extinguishing angle between preceding and following levels. Considering the strong coupling effect of the hierarchical DC high and low valves and the possibility of commutation failure after control actions during inverter-side faults, a maximum of four levels of rapid commutation failure identification analysis are performed. In each level, a small segment of numerical integration is added to the disturbed trajectory of the previous level to obtain the disturbed arc-extinguishing angle trajectory.

[0127] Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded onto the processor, it implements a fast commutation failure identification and analysis method for a set of anticipated faults as described in Embodiment 1.

[0128] Embodiment 4 of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements a fast commutation failure identification and analysis method for a set of anticipated faults as described in Embodiment 1.

[0129] The data processing flow and methods of each module in the device are consistent, so they will not be described again here.

[0130] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A fast commutation failure identification method for a set of anticipated fault examples, wherein the set of anticipated fault examples includes M anticipated fault examples of a multi-infeed DC transmission system, and the multi-infeed DC transmission system includes N DC subsystems, the fast commutation failure identification method being characterized by comprising the following steps: For each example j, a two-layer fast commutation failure identification analysis is used to traverse all DC subsystems and determine whether DC subsystem i will experience commutation failure, j∈[1,M], i∈[1,N]. In the first-level fast commutation failure identification analysis, the critical voltage for commutation failure obtained analytically, as well as the arc extinction angle, voltage, and current simulated up to a set time, are used to identify and analyze whether there is a commutation failure in DC subsystem i. If the conclusion is that a commutation failure definitely exists or that a commutation failure definitely does not exist, the commutation failure identification analysis of DC subsystem i for example j ends; if it is still uncertain whether a commutation failure exists, and there is a risk of subsequent commutation failure, the second-level fast commutation failure identification analysis is entered. In the second-level fast commutation failure identification analysis, based on the first-level fast commutation failure identification analysis, the simulation time period is increased step by step in K levels. At each level, the relationship between the arc extinction angle and the critical arc extinction angle at the set time in the simulation is used to identify whether DC subsystem i is determined to have a commutation failure. If the conclusion is that a commutation failure is determined to exist, the commutation failure identification analysis of DC subsystem i for example j ends; otherwise, the arc extinction angle, voltage, and current at the set time in the simulation are used to identify whether DC subsystem i is determined not to have a commutation failure. If it is determined that no commutation failure is determined to exist, the commutation failure identification analysis of DC subsystem i for example j ends; otherwise, the simulation time period is increased for subsequent DC subsystems with commutation failure risk, and the next level of identification analysis is entered until the last level is reached. Based on the relationship between the simulated DC arc extinction angle and the critical arc extinction angle, it is determined whether DC subsystem i is determined to have a commutation failure or not. In the second-level fast commutation failure identification analysis, based on the converter station arc extinction angle obtained at the k-th level of numerical simulation and the minimum arc extinction angle within the DC integral step obtained from the DC subsystem i simulation at time 0+, the DC subsystem i is determined to have commutation failure or uncertain to have commutation failure by criterion 6 or criterion 7. Criterion 6: If the arc extinction angle of the converter station obtained at time k in the numerical simulation is less than the critical arc extinction angle, then the DC subsystem i is determined to have commutation failure; otherwise, the existence of commutation failure is uncertain. Criterion 7: If the minimum arc extinction angle obtained from the DC integral step of DC subsystem i at the k-th time of the numerical simulation is less than the critical arc extinction angle, then DC subsystem i is determined to have commutation failure; otherwise, it is uncertain whether commutation failure exists; where k∈[1,K].

2. The fast commutation failure identification method based on a set of anticipated faults according to claim 1, characterized in that: In the first-level fast commutation failure identification analysis, the short-circuit voltage of the DC subsystem i converter station under the expected fault of the case j is obtained based on the numerical simulation at time 0+, and the arc extinction angle of the DC subsystem i converter station at time 0+ is obtained based on the numerical simulation. The DC subsystem i is determined to have commutation failure or uncertain commutation failure by criterion 1 or criterion 2. Criterion 1: If the short-circuit voltage is less than the critical voltage for commutation failure and the arc extinction angle of the converter station is less than the critical arc extinction angle, then the DC subsystem i is determined to have commutation failure; otherwise, it is not yet certain that commutation failure exists. Criterion 2: If the short-circuit voltage is less than the AC voltage when the arc extinction angle is equal to the critical arc extinction angle, calculated based on the DC current and DC control angle of the DC subsystem i converter station simulated at time 0+, then the DC subsystem i is determined to have commutation failure; otherwise, the existence of commutation failure is uncertain.

3. The fast commutation failure identification method based on a set of anticipated faults according to claim 2, characterized in that: In the first-level fast commutation failure identification analysis, the short-circuit voltage of the DC subsystem i converter station under the expected fault of the case j is obtained based on the numerical simulation at time 0+. The arc extinction angle, current and voltage of the DC subsystem i converter station at time 0+ are obtained based on the numerical simulation. The DC subsystem i is determined to have no commutation failure or uncertain commutation failure by criteria 3, 4 or 5. Criterion 3: If the short-circuit voltage is greater than the converter station voltage of DC subsystem i simulated at time 0+, and the arc extinction angle of the converter station is greater than the critical arc extinction angle, then DC subsystem i is determined to have no commutation failure and there is no need to enter the second layer of fast commutation failure identification and analysis. Criterion 4: If the simulated DC arc extinction angle at time 0+ is less than the first set value ε1, and the voltage of the DC subsystem i converter station is greater than the short-circuit voltage U. i,f If the commutation failure is not yet confirmed, but the arc extinction angle of the DC subsystem i is less than the first set value, there is a risk of commutation failure in the future. It is necessary to enter the second layer of rapid commutation failure identification and analysis. Otherwise, it is determined that there is no commutation failure in the next 4 cycles. Criterion 5: If the arc extinction angle γ of the DC subsystem i converter station simulated at time 0+ is less than the second set value ε2, and the DC current of DC subsystem i exceeds the steady-state current set ratio ε3, then it is uncertain whether there will be commutation failure in the future, but there is a risk of commutation failure in the future, and it is necessary to enter the second layer of rapid commutation failure identification analysis; otherwise, it is determined that there will be no commutation failure within the next 4 cycles.

4. The fast commutation failure identification method based on a set of anticipated faults according to claim 3, characterized in that: The multi-infeed DC transmission system is a layered DC system. If both the high valve and the low valve satisfy criterion 1 or criterion 2, then DC subsystem i is determined to have commutation failure; otherwise, it is uncertain whether commutation failure exists. If at least one of the high valve or the low valve satisfies any one of criterion 3 to criterion 5, then DC subsystem i is uncertain whether commutation failure will occur in the future and needs to enter the second layer of fast commutation failure identification and analysis. Otherwise, it is determined that there will be no commutation failure within the next 4 cycles.

5. The fast commutation failure identification method based on a set of anticipated faults according to claim 1, characterized in that: K=4, the second-level fast commutation failure identification and analysis can be performed at most four levels; The first level of analysis determines whether commutation failure will continue within one cycle after the fault occurs. The second level of analysis determines whether commutation failure will continue after 1.5 cycles after the fault occurs. The third level of analysis determines whether commutation failure will continue within 1.5 to 2.5 cycles. The fourth level of analysis determines whether commutation failure will continue within 3 to 4 cycles. If there are still unidentified DC commutation failures after the second-level fourth-level analysis, then it is assumed that the DC will not experience commutation failure after passing through the anticipated fault disturbance.

6. The fast commutation failure identification method based on a set of anticipated faults according to claim 1, characterized in that: In the second-level fast commutation failure identification analysis, based on the arc extinction angle γ of DC subsystem i converter station and the DC current of DC subsystem i obtained at the k-th time of numerical simulation, the DC subsystem i is determined to have no commutation failure or uncertain commutation failure by criteria 8, 9 or 10, and needs to enter the next level of identification analysis; Criterion 8: If the arc extinction angle γ of the DC subsystem i converter station obtained at the k-th time of the numerical simulation is less than the second fixed value ε2 and the DC arc extinction angle under the DC integral step scale is less than the critical arc extinction angle, then the DC subsystem i is temporarily uncertain to have commutation failure, but there is a risk of commutation failure in the future, and it is necessary to enter the next level of identification and analysis; otherwise, it is determined that there is no commutation failure. Criterion 9: If the arc extinction angle γ of the DC subsystem i converter station obtained at the k-th time of the numerical simulation is less than the first set value ε1, and the DC current of DC subsystem i exceeds the steady-state current set ratio ε3, then the DC subsystem i is temporarily uncertain to have commutation failure and needs to enter the next level of identification and analysis; otherwise, it is determined that there is no commutation failure. Criterion 10: If the difference between the arc extinction angle of DC subsystem i at time k of the numerical simulation and the arc extinction angle of DC subsystem i at time (k-1) of the numerical simulation is greater than the set value, then DC subsystem i is temporarily uncertain to have commutation failure and needs to enter the next level of identification and analysis; otherwise, it is determined that there is no commutation failure. Where k∈[1,K].

7. The fast commutation failure identification method for a set of anticipated faults according to claim 6, characterized in that: The multi-infeed DC transmission system is a hierarchical DC system. If both the high valve and the low valve satisfy criterion 6 or criterion 7, then DC subsystem i is determined to have commutation failure; otherwise, it is uncertain whether commutation failure exists. If at least one of the high valve or the low valve satisfies any one of criterion 8 to criterion 10, it is determined whether DC subsystem i has no commutation failure or is uncertain whether commutation failure exists, and it needs to proceed to the next level of identification and analysis.

8. The fast commutation failure identification method for a set of anticipated faults according to claim 3, characterized in that: The first set value ε1 = 12 degrees; The second set value ε2 = 13 degrees; Set the ratio ε3 = 5%.

9. A fast commutation failure identification system based on a set of anticipated faults, comprising a fast commutation failure identification method based on a set of anticipated faults according to any one of claims 1-8, characterized in that, include: The first-level analysis module adopts a fast hierarchical commutation failure identification method that integrates analytical and numerical simulation. It obtains the critical voltage of commutation failure based on an approximate analytical method that considers the dynamic characteristics of DC current. It obtains the short-circuit voltage of each DC converter station under any expected fault through numerical simulation at time 0+. Based on the critical voltage of commutation failure and the magnitude of the short-circuit voltage of each DC converter station, and combined with the arc extinction angle of each DC converter station at time 0+ of the numerical simulation, the first-level fast commutation failure identification analysis is performed on the case. The second-level hierarchical analysis module determines whether it is necessary to perform further numerical simulation for the next level of commutation failure identification analysis if no commutation failure occurred in the first-level fast commutation failure identification analysis, based on the size of the arc extinction angle γ and the change of the arc extinction angle between the previous and next levels. In each level of operation, a small segment of numerical integration method is added to obtain the arc extinction angle trajectory after the disturbance based on the disturbed trajectory of the previous level of operation.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is loaded into the processor, it implements a fast commutation failure identification method for a set of anticipated faults according to any one of claims 1-8.

11. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements a fast commutation failure identification method for a set of anticipated faults according to any one of claims 1-8.

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