Rapid commutation failure identification method and system for anticipated fault set example

Abstract

The invention discloses a rapid commutation failure identification method and system for an anticipated fault set example, and the method comprises the steps: employing a rapid classification commutation failure identification method integrating analysis and numerical simulation, carrying out the recognition and analysis of a first-level rapid commutation failure, and carrying out the analysis of a direct current of which the extinction angle or critical voltage does not meet the commutation failure requirement, but the subsequent commutation failure risk exists; if yes, further numerical simulation is carried out, second-layer grading fast commutation failure identification analysis is carried out according to the change of the extinction angle and the voltage, at most four-stage fast commutation failure identification analysis is carried out, the coupling influence of direct current control protection and an alternating current network is considered under the electromechanical simulation scale, and less numerical simulation iteration is adopted, so that the identification accuracy is improved. The direct current which may have the commutation failure within four cycles of the anticipated fault is quickly recognized stage by stage, so that the recognition robustness is effectively considered on the basis of quick commutation failure recognition analysis.

Description

Technical Field

[0001] The invention relates to a fast commutation failure identification and analysis method and related devices for fusion analysis and numerical simulation of expected fault set calculation examples, belonging to the technical field of power system and automation thereof. Background Art

[0002] With the vigorous development of large-scale renewable energy, the capacity of multi-feed-in and multi-feed-out systems for large-scale renewable energy grid connection and long-distance transmission via ultra-high voltage direct current is increasing. The control and protection systems of renewable energy are complex and changeable, with wide control time scales, strong nonlinear and time-varying factors, which has led to a sharp increase in the impact of commutation failure in AC and DC multi-feed systems, seriously restricting the operation of the power system. It is urgent to quickly identify whether there is a commutation failure under the expected fault set calculation example, and which DC may have a commutation failure.

[0003] The commutation failure identification and analysis method of the traditional expected fault set case mainly obtains the arc extinction angle curve of the DC converter station based on a complete numerical simulation, and then analyzes whether it exists (usually set to 7 degrees). Since the DC arc extinction angle curve after the expected fault is disturbed by a complete numerical simulation is obtained, it takes a long time to obtain the commutation failure identification and analysis method in large-scale AC / DC interconnected systems dominated by large-scale power electronic equipment. The simple static analytical commutation failure identification and analysis method does not consider the subsequent commutation failure after the nonlinear DC control characteristics and the interaction coupling of multiple DCs, so the accuracy and robustness of the analysis method cannot be guaranteed. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a fast commutation failure identification and analysis method and related device based on the fusion analysis and numerical simulation of expected fault set calculation examples, which takes into account both rapidity and accuracy and solves the problems disclosed in the background technology.

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

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

[0007] For each case j, two-layer fast commutation failure identification analysis is used to traverse all DC subsystems to determine whether commutation failure will occur in DC subsystem i, j∈[1,M],i∈[1,N];

[0008] In the first-level fast commutation failure identification analysis, the commutation failure critical voltage obtained by analysis and the arc extinction angle, voltage and current simulated to the set time are used to identify and analyze whether there is a commutation failure in the 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 the DC subsystem i for the case j is terminated; if it is not yet determined that 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. In each level, the arc extinction angle of the simulation to the set time is used to identify and analyze whether the DC subsystem i has a commutation failure. If the conclusion is that there is a commutation failure, the commutation failure identification analysis of the DC subsystem i for the calculation case j is terminated; otherwise, the arc extinction angle, voltage, and current of the simulation to the set time are continued to be used to identify and analyze whether the DC subsystem i is determined to have no commutation failure. If it is determined that there is no commutation failure, the commutation failure identification analysis of the DC subsystem i for the calculation case j is terminated, 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 concludes whether the DC subsystem i has a commutation failure or does not have a commutation failure according to the relationship between the simulated DC arc extinction angle and the critical arc extinction angle.

[0010] Preferably, in the first-layer fast commutation failure identification analysis, the short-circuit voltage of the converter station of the DC subsystem i under the expected fault of the example j is obtained based on the numerical simulation time 0+, and the arc extinction angle of the converter station of the DC subsystem i at the time 0+ of the numerical simulation is obtained, and it is determined by the judgment 1 or the judgment 2 whether the DC subsystem i has a commutation failure or not;

[0011] Criteria 1: If the critical voltage of 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 determines that there is a commutation failure, otherwise it is not determined that there is a commutation failure;

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

[0013] Preferably, in the first-layer fast commutation failure identification analysis, the short-circuit voltage of the DC subsystem i converter station under the expected fault of the example j is obtained based on the numerical simulation time 0+, the arc extinction angle, current and voltage of the converter station of the DC subsystem i at the time 0+ of the numerical simulation, and it is determined by criterion 3, criterion 4 or criterion 5 that the DC subsystem i does not have a commutation failure or is not sure to have a commutation failure;

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

[0015] Criterion 4: If the DC arc extinction angle simulated 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 , it is not certain whether there is a commutation failure, but the arc extinction angle of the DC subsystem i is less than the first set value ε1, and there is a risk of commutation failure in the future. It is necessary to enter the second layer of fast commutation failure identification analysis. Otherwise, it is determined that there is no commutation failure in the subsequent 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 the DC subsystem i exceeds the steady-state current setting ratio ε3, then the DC subsystem i is not sure whether there is a commutation failure, but there is a risk of commutation failure in the future, and it is necessary to enter the second-level 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, and if the high valve and the low valve simultaneously satisfy criterion 1 or criterion 2, the DC subsystem i determines that there is a commutation failure, otherwise it is not certain that there is a commutation failure; if at least one of the high valve or the low valve satisfies any one of criterion 3 to criterion 5, the DC subsystem i is not certain that there is a commutation failure, and needs to enter the second layer of fast commutation failure identification analysis, otherwise it is determined that there is no commutation failure.

[0018] Preferably, in the second-level fast commutation failure identification analysis, based on the arc extinction angle of the converter station obtained at the kth level of the numerical simulation and the minimum arc extinction angle within the DC integral step obtained by simulating the DC subsystem i at the 0+ time of the numerical simulation, it is determined by criterion 6 or criterion 7 whether the DC subsystem i has a commutation failure or not.

[0019] Criterion 6: If the arc extinction angle of the converter station obtained at the kth level of numerical simulation is less than the critical arc extinction angle, the DC subsystem i is determined to have a commutation failure, otherwise it is not determined to have a commutation failure;

[0020] Criterion 7: If the minimum arc extinction angle within the DC integral step obtained by simulating the DC subsystem i at time 0+ of the numerical simulation is less than the critical arc extinction angle, then the DC subsystem i is determined to have a commutation failure, otherwise it is not determined to have a commutation failure;

[0021] where k∈[1,K].

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

[0023] The first level analyzes whether the commutation failure will continue within 1 cycle after the fault occurs. The second level analyzes whether the commutation failure will continue after 1.5 cycles after the fault occurs. The third level analyzes whether the commutation failure will continue within 1.5 to 2.5 cycles. The fourth level analyzes whether the commutation failure will continue within 3 to 4 cycles.

[0024] If there are still DCs with unidentified commutation failures after the fourth level analysis of the second layer, it is deemed that the DC will not have commutation failures after the expected 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 obtained at the k-th level of the numerical simulation and the DC current of the DC subsystem i, it is determined by criterion 8, criterion 9 or criterion 10 that the DC subsystem i does not have a commutation failure or does not know whether there is a commutation failure, 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 kth level of numerical simulation is less than the first constant 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 about the existence of commutation failure and needs to enter the next level of identification analysis, otherwise it is determined that there is no commutation failure;

[0027] Criterion 9: If the arc extinction angle γ of the DC subsystem i converter station obtained at the kth level of the numerical simulation is less than the second set value ε2, and the DC current of the DC subsystem i exceeds the steady-state current setting ratio ε3, then the DC subsystem i is not sure whether there is a commutation failure and needs to enter the next level of identification analysis, otherwise it is determined that there is no commutation failure;

[0028] Criterion 10: If the difference between the arc extinction angle of the DC subsystem i converter station obtained at the kth level of numerical simulation and the arc extinction angle of the DC subsystem i converter station obtained at the (k-1)th level of numerical simulation is greater than the set value, it is uncertain whether the DC subsystem i has a commutation failure and needs to enter the next level of identification 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, and if the high valve and the low valve simultaneously satisfy criterion 6 or criterion 7, the DC subsystem i determines that there is a commutation failure, otherwise it is uncertain whether there is a commutation failure; 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 determines that there is no commutation failure or is uncertain whether there is a commutation failure, and needs to enter the next level of identification analysis.

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

[0032] The second setting 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 for a predicted fault set calculation example. According to the fast commutation failure identification method for a predicted fault set calculation example, the method comprises:

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

[0036] In the second-level hierarchical analysis module, if there is no commutation failure in the first-level fast commutation failure identification analysis, it is necessary to further perform partial numerical simulation for the next-level 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, based on the disturbed trajectory of the previous level operation, a small numerical integration method is further added to obtain the arc extinction angle trajectory after the disturbance.

[0037] The third aspect of the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is loaded into the processor, a method for quickly identifying phase switching failures according to an anticipated fault set calculation example described in any one of claims 1 to 9 is implemented.

[0038] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements a method for fast commutation failure identification of an anticipated fault set calculation example according to any one of claims 1 to 9.

[0039] Compared with the prior art, the beneficial effects of the present invention include at least: taking into account the coupling effects of DC control protection and AC network at the electromechanical simulation scale through two-layer multi-level fusion analysis and a numerical integration method based on the actual model of the power system, using fewer numerical simulation iterations, and quickly identifying DC that may have commutation failure within 4 cycles of the expected fault in a hierarchical and graded manner, which can take into account the strong nonlinear action response of the DC controller, and at the same time consider tracking the strong coupling effects of the hierarchical DC high and low valves and the possible commutation failure phenomenon after the γ0 control action during the inverter side fault, thereby effectively taking into account the robustness of the identification on the basis of fast commutation failure identification analysis.

[0040] Specifically, the present invention adopts a fast commutation failure identification and analysis method that integrates analysis and numerical simulation to perform the first-level fast commutation failure identification and analysis, and uses the arc extinction angle γ of the DC converter station at the time of simulation to 0+ (simulated fault action) to check γ<γ set To supplement the analysis of voltage U i，f <U ir The first layer also satisfies U i，f <U ir And γ<γ set (Usually γ set At the same time, according to the deviation of the DC arc extinction angle from the normal value (the second level is based on the deviation of the previous and next stages) and the change control of the DC current, it is determined whether the second level of rapid commutation failure identification analysis is required.

[0041] If the second-level hierarchical rapid commutation failure identification analysis needs to be integrated with some numerical simulation, in multi-level operation, the disturbed trajectory of each level of operation is further integrated with some numerical integration to obtain the disturbed arc extinction angle trajectory of the subsequent segment, and the disturbed arc extinction angle trajectory of the subsequent segment is verified step by step to determine whether there is a commutation failure, that is, γ < γ set (Usually γ set Set to 7 degrees), and determine whether to perform the next stage of rapid commutation failure identification analysis based on the deviation size of the previous and next stages and the change control of the DC current, while ensuring the correctness of the rapid commutation failure identification analysis of the expected fault, taking into account both rapidity and robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Flow chart of the fast commutation failure identification and analysis method integrating analysis and numerical simulation for the expected fault set example;

[0043] Figure 2 This is the flow chart of the fast commutation failure identification and analysis method for the DC subsystem in Example j. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0045] like Figure 1As shown, embodiment 1 of the present invention provides a fast commutation failure identification and analysis method for an expected fault set example, which is applicable to a multi-infeed DC power transmission system, and is applicable to both a DC single-layer access mode and a DC layered access mode. The multi-infeed DC power transmission system includes N DC subsystems, and DC subsystem i represents the i-th DC subsystem of the multi-infeed DC power transmission system, i=1, 2, ..., N. The expected fault set includes M expected fault examples, and example j represents the j-th expected fault example therein, j=1, 2, ..., M.

[0046] The fast commutation failure identification and analysis method is a fast commutation failure identification and analysis method that integrates analysis and numerical simulation, including: a first-level fast commutation failure identification and analysis that integrates analysis and numerical simulation, and a second-level hierarchical fast commutation failure identification and analysis that integrates partial numerical simulation according to changes in arc extinction angle and voltage. Figure 2 As shown, starting from example 1, in each example j, it starts from DC subsystem 1. If the first-level fast commutation failure identification analysis can determine that the DC subsystem i has a commutation failure or that there is no commutation failure, the judgment of the DC subsystem i ends and enters the judgment of the DC subsystem (i+1); if the first-level fast commutation failure identification analysis is still uncertain whether a commutation failure occurs, the second-level hierarchical fast commutation failure identification analysis is entered. After obtaining the conclusion that there is a commutation failure or there is no commutation failure, the judgment of the DC subsystem i ends and enters the judgment of the DC subsystem (i+1). In each example j, until the DC subsystem N completes the judgment, enter the example (j+1), and finally complete all the judgments of the M expected fault examples in the expected fault set.

[0047] Specifically, first, the critical voltage of commutation failure is obtained based on the approximate analytical method considering the dynamic characteristics of DC current, and the short-circuit voltage of each DC converter station under any expected fault is obtained through numerical simulation 0+. According to the critical voltage of commutation failure and the short-circuit voltage of each DC converter station, and combined with the arc extinction angle of each DC converter station at the time of numerical simulation 0+ (simulated fault action), the first-level rapid commutation failure identification analysis is performed. If the arc extinction angle or voltage does not meet the requirements of the first-level rapid commutation failure identification analysis, further numerical simulation is performed, and according to the changes in the arc extinction angle and voltage, the second-level hierarchical rapid commutation failure identification analysis is performed, and at most four-level rapid commutation failure identification analysis is performed. The first level of the second layer mainly analyzes whether the commutation failure will continue within 1 cycle after the fault occurs. The second level mainly analyzes whether the commutation failure will continue after 1.5 cycles after the fault occurs. The third level mainly analyzes whether the commutation failure will continue within 1.5 to 2.5 cycles. The fourth level mainly analyzes whether the commutation failure will continue within 3 to 4 cycles. If there is still DC with unidentified commutation failure after the second-level hierarchical analysis, it is considered that the DC will not have commutation failure after the expected fault disturbance. Since each level not only determines the commutation failure based on the voltage, but also strictly determines the commutation failure based on the arc extinction angle, checks whether the arc extinction angle of each DC converter station meets the commutation failure conditions, and improves the accuracy of the commutation failure identification and analysis. Whether to perform the second-level hierarchical commutation failure identification analysis must meet the conditions that the arc extinction angle is decreasing, the DC current is slightly increasing, or the AC voltage is slightly recovering, avoiding scanning to find whether γ < γ during the entire fault period. set , improving the rapidity of commutation failure identification.

[0048] In each level of fast commutation failure identification and analysis, a fusion analysis and numerical integration method based on the actual model of the power system are used. The coupling effect of DC control protection and AC network is taken into account at the electromechanical simulation scale. Smaller numerical simulation iterations are used to quickly identify DC that may have commutation failure within 4 cycles of the expected fault, thereby effectively taking into account the robustness of identification on the basis of fast commutation failure identification and analysis. The second level sets four levels of tracking to 4 cycles of possible commutation failure, mainly considering the strong coupling effect of tracking the hierarchical DC high and low valves and the possible commutation failure after γ0 control action during the inverter side fault.

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

[0050] The critical voltage U of commutation failure of each DC subsystem i ir The short-circuit voltage U of each DC subsystem i is obtained by approximating the DC dynamic process. i，fBased on the existing electromechanical simulation program, numerical simulation is performed for case j to obtain the critical voltage U of the commutation failure of the DC subsystem i. ir , short circuit voltage U i，f And the fast commutation failure identification analysis is performed on the arc extinction angle γ of the DC converter station from the expected fault numerical simulation to the 0+ moment (simulated fault action moment) specified in the case j. The first level of fast commutation failure identification analysis uses the following criteria: the commutation failure identification criteria that integrates analysis and numerical simulation, as well as the uncertain criteria.

[0051] The commutation failure identification criteria integrating analysis and numerical simulation include: if the commutation failure identification conditions of analysis and numerical simulation are met at the same time, then the commutation failure identification criteria integrating analysis and numerical simulation are met, and the first layer directly outputs that there is a commutation failure in the DC subsystem, and the fast commutation failure identification analysis of case j of the DC subsystem is completed, and the fast commutation failure identification analysis of case j of the next DC subsystem is entered.

[0052] If the commutation failure identification criteria of the integrated analysis and numerical simulation are not met, it is further determined whether the uncertain criteria are met; the uncertain criteria include: tracking the arc extinction angle γ, the DC current I i Size and its changes, for example but not limited to, taking into account the decrease in the arc extinction angle, a slight increase in the DC current or a slight rise in the AC voltage, 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 analysis of the example j of the DC subsystem is completed, and the fast commutation failure identification analysis of the example j of the next DC subsystem is entered; if the uncertain criterion is met, the first layer of fast commutation failure identification analysis of the example j of the DC subsystem is completed, and the second layer of hierarchical fast commutation failure identification analysis of the fusion part of the numerical simulation based on the change of the arc extinction angle and the voltage is entered.

[0053] It can be understood that for a multi-infeed DC transmission system, the first-level rapid commutation failure identification analysis ends the rapid identification of a certain example, including two situations: one is that all N DC subsystems meet the commutation failure identification criteria, and N DC subsystems are determined to have commutation failures; the other is that all N DC subsystems do not meet the uncertain criteria, and N DC subsystems are determined not to have commutation failures. Otherwise, for this example, the second-level hierarchical rapid commutation failure identification analysis is performed on the DC subsystems that may have commutation failures, and the simulation continues to track possible commutation failure phenomena until the DC current change or the arc extinction angle change is small or the maximum number of levels is reached, then the example is terminated.

[0054] It is worth noting that for layered DC, the high valve and low valve are analyzed separately. If both the high valve and the low valve meet the commutation failure criteria, it is determined that there is a commutation failure. If at least one of the high valve or the low valve meets any of the uncertain criteria, the DC subsystem i is uncertain whether there will be a commutation failure in the future, and needs to enter the second-level fast commutation failure identification analysis, otherwise it is determined that there will be no commutation failure in the next 4 cycles.

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

[0056] Step 1: First, consider the DC dynamic process approximately and analytically calculate the commutation failure critical voltage U of each DC subsystem i. ir A person skilled in the art can calculate the commutation failure critical voltage U by any known method. ir Values, for example, but not limited to, the calculation method disclosed in Chinese patent application No. CN202210481264.8.

[0057] Step 2: Based on the existing electromechanical simulation program, the short-circuit voltage U of the DC converter station under any expected fault of each DC subsystem i is obtained through numerical simulation at time 0+. i，f .

[0058] Step 3: The expected fault set contains any specified expected faults. The fault action is simulated by numerical simulation to obtain the arc extinction angle γ of the DC converter station at time 0+. ir and the short-circuit voltage U of the DC converter station i，f Perform fast commutation failure identification analysis.

[0059] Step 4: If the commutation failure identification conditions of both analysis and numerical simulation are met, the commutation failure identification criterion of fusion analysis and numerical simulation is met. The first layer directly outputs that the DC subsystem has commutation failure. The calculation example of DC subsystem i is quickly identified. The commutation failure identification criterion of fusion analysis and numerical simulation is expressed by the following formula:

[0060] U i，f <U ir And γ<γ set (1)

[0061] Where:

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

[0063] U i，f is the short-circuit voltage of the DC converter station;

[0064] γ is the arc extinction angle;

[0065] γ set is the critical arc extinction angle, preferably 7 degrees.

[0066] It is worth noting that for stratified DC, if the high valve and low valve are analyzed separately, both the high valve and the low valve must meet the above constraints at the same time, otherwise there will be commutation failure.

[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 formula (2) or formula (3) criteria are met, it is still uncertain whether the DC commutation failure has occurred, and further second-level rapid commutation failure identification analysis is required, and the minimum arc extinction angle within the DC integral step obtained by the DC simulation at the 0+ moment of the simulated fault action is saved; if the following formula (2) or formula (3) criteria are not met, there is no commutation failure in the subsequent 4 cycles, and the rapid identification of the example for the DC subsystem i is completed. The uncertain criterion is expressed as follows:

[0068] γ<ε1 and U i >U i，f (2)

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

[0070] Where:

[0071] ε1 is a first setting 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 is the voltage of commutation bus i, U i，f is the short-circuit voltage of the DC converter station;

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

[0076] It can be understood that the specific meaning of the above steps is that if the arc extinction angle is decreasing, the DC current is slightly increasing, or the AC voltage is slightly rising, it is still uncertain, so the arc extinction angle γ, the DC current I i If the DC extinction angle γ is less than the second set value ε2 (such as 13 degrees) and the DC current exceeds the third set ratio ε3 (such as 5%) of the steady-state current, or the DC extinction angle γ is less than the first set value ε1 (such as 12 degrees) and the converter station voltage is greater than Ui，f , Considering that the subsequent DC arc extinction angle of DC control may be further reduced, it is still uncertain whether the DC commutation failure occurs. However, the DC subsystem i arc extinction angle is significantly reduced, and there is a greater risk of commutation failure in the future. Further second-level fast commutation failure identification analysis is required.

[0077] Step 6: If all DC subsystems i of the multi-infeed DC transmission system do not require the second-level fast commutation failure identification analysis, then all DC subsystems i in this example do not have DC commutation failure or all have commutation failure, and the fast commutation failure identification analysis of the example ends.

[0078] It can be understood that for a certain example, for all N DC subsystems of the multi-infeed DC transmission system, a clear conclusion is obtained in the first layer, and there is a commutation failure or the DC current change (arc extinction angle) is small and the commutation failure is highly unlikely to exist, which is equivalent to the rapid commutation failure identification of the example has been completed. If a clear conclusion is not obtained for some DC subsystems in the first layer, the part of the DC subsystems in the example that has not been clearly concluded needs to be further identified in the second layer.

[0079] The second-level hierarchical fast commutation failure identification analysis, which integrates some numerical simulations, adopts a multi-level fast commutation failure identification analysis with a step-by-step increase in simulation time periods. In each level, the arc extinction angle γ is used as a criterion for determining commutation failure, and it is determined whether to further perform the next level of fast commutation failure identification analysis. If there are still DCs that have not been identified for commutation failure after the last level of analysis in the second layer, it is considered that the DC will not experience commutation failure after the expected fault disturbance, and the fast commutation failure identification analysis process of the example is terminated.

[0080] Specifically, in the multi-level fast commutation failure identification operation, the process of each level of operation is: numerical simulation to the corresponding test time set in advance at each level, obtaining the disturbed trajectory of the DC arc extinction angle of the power system in this period under the expected fault, and performing the second-level commutation failure identification analysis on the expected fault according to the disturbed trajectory of the arc extinction angle. If the second-level DC arc extinction angle does not meet the commutation failure condition, but meets the conditions for further performing the next-level fast commutation failure identification analysis, then perform the next-level operation. If the multi-level operation reaches the preset maximum number of levels, or the arc extinction angle of a certain level in the second level meets the commutation failure condition, then exit the multi-level operation.

[0081] Preferably, as one of the outstanding essential features of the present invention, considering the strong coupling effect of the hierarchical DC high and low valves and the possible commutation failure after the γ0 control action during the inverter side fault, at most four levels of fast commutation failure identification analysis are performed. The first level mainly analyzes whether the commutation failure will continue within 1 cycle after the fault occurs, the second level mainly analyzes whether the commutation failure will continue within 1.5 cycles after the fault occurs, the third level mainly analyzes whether the commutation failure will continue within 1.5 to 2.5 cycles, and the fourth level mainly analyzes whether the commutation failure will continue within 3 to 4 cycles. For the DC that has not yet experienced commutation failure in the first three levels, it should also be determined whether it is necessary to continue partial numerical simulation to perform the next level of fast commutation failure identification analysis. Simulate to the corresponding examination time of each level. If the DC arc extinction angle simulated at this time is less than the critical arc extinction angle, the DC has a commutation failure. If there is still a DC that has not been identified for commutation failure after the second level of four-level analysis, it is considered that the DC will not experience commutation failure after the expected fault disturbance, and the example fast commutation failure identification analysis process ends.

[0082] Preferably, each level is based on the DC arc extinction angle γ and γ set (Usually γ set For DC without commutation failure, the arc extinction angle γ and the change of arc extinction angle between the previous and next layers are used to determine whether it is necessary to further perform partial numerical simulation for the next level of commutation failure identification analysis.

[0083] In addition to judging commutation failure based on voltage, the first level also strictly judges commutation failure based on the arc extinction angle standard, and verifies whether the arc extinction angle of each DC converter station meets the commutation failure conditions, which improves the accuracy of commutation failure identification and analysis. Whether to conduct the second-level hierarchical commutation failure identification and analysis must meet the conditions of arc extinction angle reduction, slight increase in DC current or slight rise in AC voltage, avoiding scanning to find whether γ < γ during the entire fault period. set , improving the rapidity of commutation failure identification.

[0084] At each level of the fast commutation failure identification and analysis, a fusion analysis and a numerical integration method based on the actual model of the power system are adopted. The coupling effects of DC control protection and AC network are taken into account at the electromechanical simulation scale. Smaller numerical simulation iterations are used to quickly identify DC lines that may experience commutation failure within 4 cycles of the expected fault, thereby effectively taking into account the robustness of the identification on the basis of the fast commutation failure identification and analysis.

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

[0086] For the DC that has not experienced commutation failure, according to the DC arc extinction angle γ at the simulation time of 1 cycle (including the minimum DC arc extinction angle under the electromechanical scale and the DC integral step scale) and γ set (Usually γ set Set to 7 degrees) for commutation failure identification.

[0087] For conventional DC:

[0088] If γ<γ set (Usually γ set Set to 7 degrees), the DC second layer first stage has a commutation failure. Specifically, if the simulation reaches 1 cycle, the DC arc extinction angle at this time is less than the critical arc extinction angle, or the DC arc extinction angle simulated in the DC integral step is less than the critical arc extinction angle and the DC saved at time 0+ is less than the critical arc extinction angle, then the DC has a commutation failure. It is worth noting that due to the small DC time scale, different simulation steps are used for AC and DC in electromechanical simulation. When tracking the arc extinction angle, the changes in the DC arc extinction angle at the electromechanical scale and the DC integral step scale, especially the minimum value of the DC scale, should be tracked.

[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 (such as 5%) of the steady-state current, or the arc extinction angle is less than a certain set value ε2 (such as 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 level of fast commutation failure identification analysis.

[0090] For layered DC:

[0091] If the DC arc extinction angles of the high valve and the low valve both satisfy γ<γ set (Usually γ set If the DC voltage is set to 7 degrees, there is a commutation failure in the first stage of the second layer of the DC.

[0092] 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 (such as 5%) of the steady-state current, the DC second layer needs to continue partial simulation to perform the next level of fast commutation failure identification analysis.

[0093] If the DC that has not experienced commutation failure in this stage does not need to perform the next stage of rapid commutation failure identification analysis, the rapid commutation failure identification analysis process of the example ends. Otherwise, the number of AC iterations is set to 7 times, and the next stage of rapid commutation failure identification analysis is performed. It is worth noting that the number of AC iterations is set to 7 times, and the approximate simulation iteration convergence solution is used as the identification basis to improve the rapidity. The differential algebraic equations at the electromechanical scale of AC iteration processing are iteratively solved.

[0094] The second level of the second layer mainly analyzes whether the 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 fast commutation failure identification analysis for the DC subsystem that has not yet experienced commutation failure.

[0095] For the DC that has not experienced commutation failure, according to the DC arc extinction angle γ at the simulation time of 1.5 cycles (including the minimum DC arc extinction angle under the electromechanical scale and the DC integral step scale) and γ set (Usually γ set Set to 7 degrees) for commutation failure identification.

[0096] For conventional DC:

[0097] If γ<γ set (Usually γ set If the DC voltage is set to 7 degrees, there is a commutation failure in the second stage of the second layer of the DC.

[0098] Otherwise, if the DC extinction angle is less than a certain set value ε2 or the difference in the arc extinction angle between the front and rear levels is greater than the set value, the DC needs to continue partial simulation to perform the next level of fast commutation failure identification analysis.

[0099] For layered DC:

[0100] If the DC arc extinction angles of the high valve and the low valve both satisfy γ<γ set (Usually γ set If the DC voltage is set to 7 degrees, there is a commutation failure in the second stage of the second layer of the DC.

[0101] If the DC that has not experienced commutation failure in this stage does not need to perform the next stage of rapid commutation failure identification analysis, the rapid commutation failure identification analysis process of the example ends. Otherwise, the number of AC iterations is set to 7 times, and the next stage of rapid commutation failure identification analysis is performed.

[0102] The third level of the second layer mainly analyzes whether commutation failure will continue within 1.5 to 2.5 cycles, and determines whether it is necessary to continue partial numerical simulation for the next level of fast commutation failure identification analysis for the DC subsystem that has not yet experienced commutation failure.

[0103] For the DC that has not experienced commutation failure, according to the DC arc extinction angle γ at the time of simulation to 2.5 cycles (including the minimum DC arc extinction angle under the electromechanical scale and the DC integral step scale) and γ set (Usually γ set Set to 7 degrees) for commutation failure identification.

[0104] For conventional DC:

[0105] If γ<γ set (Usually γ setIf the DC voltage is set to 7 degrees, there is a commutation failure in the third stage of the second layer of the DC.

[0106] Otherwise, if the DC extinction angle is less than a certain set value ε2 or the difference in the arc extinction angle between the front and rear levels is greater than the set value, the DC needs to continue partial simulation to perform the next level of fast commutation failure identification analysis.

[0107] For layered DC:

[0108] If the DC arc extinction angles of the high valve and the low valve both satisfy γ<γ set (Usually γ set If the DC voltage is set to 7 degrees, there is a commutation failure in the third stage of the second layer of the DC.

[0109] If the difference in arc extinction angle between the layers before and after the high valve or low valve is greater than the set value, the DC second layer needs to continue partial simulation to perform the next level of fast commutation failure identification analysis.

[0110] If the DC that has not experienced commutation failure in this stage does not need to perform the next stage of rapid commutation failure identification analysis, the rapid commutation failure identification analysis process of the example ends. Otherwise, the number of AC iterations is set to 7 times, and the next stage of rapid commutation failure identification analysis is performed.

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

[0112] For the DC that has not experienced commutation failure, according to the DC arc extinction angle γ at the time of simulation to 4 cycles (including the minimum DC arc extinction angle under the electromechanical scale and the DC integral step scale) and γ set (Usually γ set Set to 7 degrees) for commutation failure identification.

[0113] For conventional DC:

[0114] If γ<γ set (Usually γ set If the DC voltage is set to 7 degrees, there is a commutation failure in the fourth stage of the second layer of the DC.

[0115] For layered DC:

[0116] If the DC arc extinction angles of the high valve and the low valve both satisfy γ<γ set (Usually γ set If the DC voltage is set to 7 degrees, there is a commutation failure in the fourth stage of the second layer of the DC.

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

[0118] Step 7, enter the second level of fusion part of the numerical simulation of rapid commutation failure identification analysis. Each level is based on the DC arc extinction angle γ and γ set (Usually γ set The commutation failure identification is performed at 7 degrees. For the DC without commutation failure, it is determined whether it is necessary to further perform partial numerical simulation for the next level of commutation failure identification analysis based on the arc extinction angle γ and the change of the arc extinction angle between the previous and next layers. Considering the strong coupling effect of the high and low valves of the layered DC and the commutation failure phenomenon that may occur after the γ0 control action during the inverter side fault, at most four levels of fast commutation failure identification analysis are performed.

[0119] Step 8, initially k=1, and the kth level fast commutation failure identification analysis with k=1 is performed. The kth level mainly analyzes whether the commutation failure will continue for a period of time 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 the partial numerical simulation of the DC that has not yet failed to commutate to perform the next level of fast commutation failure identification analysis. First, simulate a short section according to 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), and obtain the DC arc extinction angle γ at the simulation time (including the minimum value of the DC arc extinction angle under the electromechanical scale and the DC integral step scale).

[0120] Step 9: For conventional DC, if γ<γ set (Usually γ set Set to 7 degrees), or for stratified DC, if the DC arc extinction angles of the high valve and the low valve both satisfy γ<γ set (Usually γ set If the DC power supply is set to 7 degrees, the DC power supply has a commutation failure in the second layer kth stage. If all DC power supply in this stage has been determined to have commutation failure, the fast commutation failure identification and analysis process of the example ends.

[0121] Step 10: If the DC current that has not yet experienced commutation failure satisfies the following conditions: the DC arc extinction angle is less than the set value ε1 and the simulated converter station voltage is greater than U i,f And the DC current exceeds a certain ratio ε3 (such as 5%) of the steady-state current, or 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, 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 (such as 5%) of the steady-state current, the DC current needs to continue partial simulation to perform the next level of fast commutation failure identification analysis and enter step 11.

[0122] Step 11, if k is less than 4, go to step 12, otherwise k=4. If there is still no DC with commutation failure identified after the k=4-level analysis, it is considered that the DC will not have commutation failure after the expected fault disturbance, and the example fast commutation failure identification and analysis process ends.

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

[0124] Embodiment 2 of the present invention provides a device for identifying and analyzing a fast commutation failure due to an anticipated fault, which is characterized by comprising:

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

[0126] The second-level hierarchical analysis module, if there is no commutation failure in the first-level rapid commutation failure identification analysis for the DC, it is determined that it is necessary to further perform partial numerical simulation to perform the next-level commutation failure identification analysis based on the arc extinction angle and the change of the arc extinction angle between the previous and next levels. Then the second-level hierarchical multi-level analysis operation is adopted, and the process of each level of operation is: perform commutation failure identification based on the DC arc extinction angle at the simulation time (usually set to 7 degrees). For the DC that has not experienced commutation failure, it is determined whether it is necessary to further perform partial numerical simulation to perform the next-level commutation failure identification analysis based on the arc extinction angle and the change of the arc extinction angle between the previous and next levels. Considering the strong coupling effect of the hierarchical DC high and low valves and the possible commutation failure after the control action during the inverter side fault, at most four levels of rapid commutation failure identification analysis are performed. In each level of operation, based on the disturbed trajectory of the previous level of operation, a small numerical integration method is further added to obtain the arc extinction angle trajectory after the disturbance.

[0127] Embodiment 3 of the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is loaded into the processor, a method for fast phase switching failure identification and analysis of an anticipated fault set calculation example according to embodiment 1 is implemented.

[0128] Embodiment 4 of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for identifying and analyzing fast commutation failures of a predicted fault set calculation example according to embodiment 1 is implemented.

[0129] The data processing flow and method of each module in the device are consistent and will not be repeated here.

[0130] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fast commutation failure identification method for an expected fault set example, wherein the expected fault set includes M expected 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 is characterized in that it includes the following steps: For each case j, two-layer fast commutation failure identification analysis is used to traverse all DC subsystems to determine whether commutation failure will occur in DC subsystem i, j∈[1,M], i∈[1,N]; In the first-level fast commutation failure identification analysis, the commutation failure critical voltage obtained by analysis and the arc extinction angle, voltage and current simulated to the set time are used to identify and analyze whether there is a commutation failure in the 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 the DC subsystem i for the case j is terminated; if it is not yet determined that there is a commutation failure, there is a risk of commutation failure in the future, and 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. In each level, the relationship between the arc extinction angle and the critical arc extinction angle of the simulation to the set time is used to identify and analyze whether the DC subsystem i is determined to have a commutation failure. If the conclusion is that the commutation failure is determined, the commutation failure identification analysis of the DC subsystem i for the calculation case j is terminated; otherwise, the arc extinction angle, voltage, and current of the simulation to the set time are continued to be used to identify and analyze whether the DC subsystem i is determined to not have a commutation failure. If it is determined that there is no commutation failure, the commutation failure identification analysis of the DC subsystem i for the calculation case j is terminated, otherwise, the simulation time period is increased for the DC with the risk of commutation failure in the future, and the next level of identification analysis is entered until the last level is reached. According to the relationship between the simulated DC arc extinction angle and the critical arc extinction angle, it is concluded that the DC subsystem i is determined to have a commutation failure or is determined not to have a commutation failure.

2. The method for fast commutation failure identification of a predicted fault set example according to claim 1 is 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 case j is obtained based on the numerical simulation time 0+, and the arc extinction angle of the DC subsystem i converter station at the numerical simulation time 0+. It is determined by judgment 1 or judgment 2 whether the DC subsystem i has a commutation failure or not. Criteria 1: If the critical voltage of 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 determines that there is a commutation failure, otherwise it is not determined that there is a commutation failure; Criterion 2: If the short-circuit voltage is less than the AC voltage when the arc extinction angle calculated based on the DC current of the DC subsystem i converter station simulated at time 0+ and the DC control angle is equal to the critical arc extinction angle, then the DC subsystem i is determined to have a commutation failure, otherwise it is not determined to have a commutation failure.

3. The method for fast commutation failure identification of a predicted fault set calculation example according to claim 2 is 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 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+ of the numerical simulation, and the DC subsystem i is judged to have no commutation failure or not to have commutation failure through criterion 3, criterion 4 or criterion 5; Criterion 3: If the short-circuit voltage is greater than the voltage of the DC subsystem i converter station simulated at time 0+, and the converter station arc extinction angle is greater than the critical arc extinction angle, then the DC subsystem i is determined to have no commutation failure, and there is no need to enter the second-level fast commutation failure identification analysis; Criterion 4: If the DC arc extinction angle simulated 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 , it is not yet certain whether there is a commutation failure, but the arc extinction angle of the DC subsystem i is less than the first set value, and there is a risk of commutation failure in the future. It is necessary to enter the second layer of fast commutation failure identification analysis, otherwise it is determined that there is no commutation failure in the subsequent 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 the DC subsystem i exceeds the steady-state current setting ratio ε3, it is temporarily uncertain whether there will be a commutation failure in the future, but there is a risk of commutation failure in the future, and it is necessary to enter the second-level fast commutation failure identification analysis, otherwise it is determined that there will be no commutation failure in the subsequent 4 cycles.

4. The method for fast commutation failure identification of a predicted fault set calculation example according to claim 3 is characterized in that: The multi-infeed DC transmission system is a layered DC. If the high valve and the low valve meet criterion 1 or criterion 2 at the same time, the DC subsystem i determines that there is a commutation failure, otherwise it is uncertain whether there is a commutation failure; if at least one of the high valve or the low valve meets any one of criterion 3 to criterion 5, the DC subsystem i is uncertain whether there will be a commutation failure in the future, and needs to enter the second layer of fast commutation failure identification analysis, otherwise it is determined that there will be no commutation failure in the subsequent 4 cycles.

5. The method for fast commutation failure identification of a predicted fault set calculation example according to claim 1 is characterized in that: In the second-level fast commutation failure identification analysis, based on the converter station extinction angle obtained at the kth level of numerical simulation and the minimum extinction angle within the DC integral step obtained by simulating the DC subsystem i at the 0+ time of numerical simulation, it is determined by criterion 6 or criterion 7 whether the DC subsystem i has a commutation failure or not. Criterion 6: If the arc extinction angle of the converter station obtained at the kth level of numerical simulation is less than the critical arc extinction angle, the DC subsystem i is determined to have a commutation failure, otherwise it is not determined to have a commutation failure; Criterion 7: If the minimum arc extinction angle within the DC integral step obtained by simulating the DC subsystem i at the kth level of the numerical simulation is less than the critical arc extinction angle, then the DC subsystem i is determined to have a commutation failure, otherwise it is not determined to have a commutation failure; where k∈[1,K].

6. The method for fast commutation failure identification of a predicted fault set calculation example according to claim 5 is characterized in that: K = 4, the second layer fast commutation failure identification analysis is performed at most four levels; The first level analyzes whether the commutation failure will continue within 1 cycle after the fault occurs. The second level analyzes whether the commutation failure will continue after 1.5 cycles after the fault occurs. The third level analyzes whether the commutation failure will continue within 1.5 to 2.5 cycles. The fourth level analyzes whether the commutation failure will continue within 3 to 4 cycles. If there are still DCs with unidentified commutation failures after the fourth level analysis of the second layer, it is deemed that the DC will not have commutation failures after the expected fault disturbance.

7. The method for fast commutation failure identification of a predicted fault set calculation example according to claim 5 is characterized in that: 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 the DC subsystem i obtained at the k-th level of the numerical simulation, it is determined by criterion 8, criterion 9 or criterion 10 that the DC subsystem i does not have a commutation failure or does not have a commutation failure, 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 kth level of the numerical simulation is less than the first constant ε 1 If the DC arc extinction angle under the DC integral step scale is less than the critical arc extinction angle, the DC subsystem i is not sure whether there is a commutation failure, but there is a risk of commutation failure in the future, and it is necessary to enter the next level of identification 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 kth level of the numerical simulation is less than the second set value ε 2 , and the DC current of DC subsystem i exceeds the steady-state current setting ratio ε 3 , then the DC subsystem i is not sure whether there is a commutation failure yet, and needs to enter the next level of identification analysis, otherwise it is determined that there is no commutation failure; Criterion 10: If the difference between the arc extinction angle of the DC subsystem i converter station obtained at the kth level of numerical simulation and the arc extinction angle of the DC subsystem i converter station obtained at the (k-1)th level of numerical simulation is greater than the set value, it is not determined that there is a commutation failure in the DC subsystem i and it is necessary to enter the next level of identification analysis. Otherwise, it is determined that there is no commutation failure. where k∈[1,K].

8. The method for fast commutation failure identification of a predicted fault set calculation example according to claim 7 is characterized in that: The multi-infeed DC transmission system is a layered DC. If the high valve and the low valve simultaneously meet criterion 6 or criterion 7, the DC subsystem i determines that there is a commutation failure, otherwise it is uncertain whether there is a commutation failure; if at least one of the high valve or the low valve meets any one of criterion 8 to criterion 10, it is determined that the DC subsystem i does not have a commutation failure or is uncertain whether there is a commutation failure, and needs to enter the next level of identification analysis.

9. The method for fast commutation failure identification of a predicted fault set calculation example according to claim 3 is characterized by: The first setting value ε1 = 12 degrees; The second setting value ε2 = 13 degrees; Set the ratio ε3 = 5%.

10. A fast commutation failure identification system for an expected fault set calculation example, running a fast commutation failure identification method for an expected fault set calculation example according to any one of claims 1 to 9, characterized in that: include: The first-level analysis module adopts a fast hierarchical commutation failure identification method that integrates analysis and numerical simulation. The critical voltage of commutation failure is obtained based on an approximate analytical method that considers the dynamic characteristics of DC current. The short-circuit voltage of each DC converter station under any expected fault is obtained through numerical simulation at time 0+. Based on the critical voltage of commutation failure and the size of short-circuit voltage of each DC converter station, and combined with the arc extinction angle of each DC converter station at time 0+ of numerical simulation, the first-level fast commutation failure identification analysis is performed on the example. In the second-level hierarchical analysis module, if there is no commutation failure in the first-level fast commutation failure identification analysis, it is necessary to further perform partial numerical simulation for the next-level 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, based on the disturbed trajectory of the previous level operation, a small numerical integration method is further added to obtain the arc extinction angle trajectory after the disturbance.

11. 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 a processor, a fast commutation failure identification method according to a predicted fault set calculation example according to any one of claims 1 to 9 is implemented.

12. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a fast commutation failure identification method of a predicted fault set calculation example according to any one of claims 1 to 9 is implemented.

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