A method, apparatus, equipment and medium for analyzing commutation failure in a DC transmission system.

Abstract

This invention discloses a method, apparatus, equipment, and medium for analyzing commutation failure in a DC transmission system, relating to the field of DC transmission technology. The method includes the following steps: determining converter valve fault parameters; analyzing whether a fault type will lead to commutation failure of the faulty converter valve within the fault duration according to the converter valve conduction sequence during normal operation of the converter transformer, based on different fault types; if commutation failure is caused by the faulty converter valve, obtaining the operating parameters of the DC transmission system after the commutation failure; obtaining the shut-off angle under the current operating condition; and analyzing whether non-faulty converter valves will experience continuous commutation failures based on the shut-off angle under the current operating condition and the converter valve conduction sequence during normal operation of the converter transformer. The analysis method of this invention starts from the perspective of converter valve faults, analyzing the problem of excessively small shut-off angles caused by different influencing factors, greatly improving the accuracy of commutation failure analysis results.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission technology, and in particular to a method, apparatus, equipment and medium for analyzing commutation failure in DC power transmission systems. Background Technology

[0002] DC transmission systems have advantages such as large transmission power, fast and controllable power, and low transmission loss, and are widely used in long-distance power transmission across large regions and asynchronous power grid interconnection.

[0003] The commutation process in a DC transmission system involves sequentially switching the current path on and off via the converter valve arms, thereby converting alternating current (AC) to direct current (DC). When valves are commutating, if, for various reasons, a valve intended to be closed fails to close, or if it is closed but then re-energized under positive voltage, commutation failure occurs. Commutation failure is one of the most common faults in DC transmission systems and is related to many factors, primarily including commutation voltage, converter transformer turns ratio, DC current, commutation reactance, and leading firing angle.

[0004] Traditional commutation failure analysis typically starts with AC system faults, analyzing changes in the commutation voltage of the AC transmission system, and then calculating whether the operating turn-off angle is less than the minimum turn-off angle, ultimately determining whether commutation failure has occurred. Existing commutation failure analysis methods only start with AC system faults, obtaining the relationship between commutation voltage and operating turn-off angle, and thus the connection between commutation voltage and commutation failure, without considering the influence of other factors on the operating turn-off angle. This ultimately leads to lower accuracy in the analysis results regarding commutation failure. Summary of the Invention

[0005] This invention provides a method, apparatus, equipment, and medium for analyzing commutation failure in DC transmission systems. It solves the problem that existing analysis methods only start from AC system faults, obtaining only the relationship between the operating turn-off angle and the commutation voltage, and cannot analyze other influencing factors, ultimately leading to low accuracy in the analysis results of commutation failure.

[0006] This invention provides a method for analyzing commutation failure in a DC transmission system, using converter valve failure as an analytical factor for commutation failure in the DC transmission system, and includes the following steps:

[0007] Determine the fault parameters of the converter valve, which include the faulty converter valve number, fault type and fault duration. The fault type includes control system fault, DC side short circuit fault of converter valve, AC side short circuit fault of converter valve and short circuit fault of converter valve.

[0008] Based on different fault types, the conduction sequence of the converter valves during normal operation of the converter transformer is analyzed during the fault duration to determine whether the fault type will lead to the failure of the faulty converter valve to switch phases.

[0009] If the failure of the converter valve leads to commutation failure, the operating parameters of the DC transmission system after the commutation failure are obtained. The operating parameters include the converter voltage and DC current of the DC transmission system. The shut-off angle under the current operating condition is obtained based on the operating parameters.

[0010] Based on the shut-off angle under the current operating conditions, and according to the conduction sequence of the converter valves during normal operation of the converter transformer, it is analyzed whether the converter valves that have not experienced faults will experience continuous commutation failures.

[0011] Preferably, based on different fault types, during the fault duration, analysis is performed to determine whether the fault type will lead to commutation failure of the faulty converter valve according to the normal operating sequence of the converter valves. This includes:

[0012] When the fault type is a control system fault, that is, the trigger pulse of the faulty switching valve is lost. When the trigger pulse is lost at the commutation time, the faulty switching valve does not receive the trigger pulse and cannot conduct, resulting in the failure of the switching valve to commutate. When the trigger pulse is lost but does not occur at the commutation time, it will not cause the switching valve to commutate.

[0013] When the fault type is a short circuit fault on the DC side of the converter valve, the converter valve on the inverter side cannot maintain conduction, the DC voltage on the inverter side drops, and normal commutation cannot be performed. Once this fault occurs, it will lead to commutation failure.

[0014] When the fault type is a short circuit fault on the AC side of the converter valve, that is, a short circuit at the AC side outlet of the converter valve, the commutation voltage drops, causing the faulty converter valve to not bear the positive voltage during commutation, thus leading to commutation failure; when the fault does not occur at the commutation time, it will not cause the faulty converter valve to fail to commutate.

[0015] When the fault type is a short circuit fault in the converter valve, the faulty converter valve is short-circuited and continues to conduct, preventing the faulty converter valve from completing the commutation.

[0016] Preferably, based on the shut-off angle under the current operating conditions, the analysis considers whether the converter valves that have not experienced a fault will experience continuous commutation failures according to the converter valve conduction sequence during normal operation of the converter transformer, including:

[0017] If the shut-off angle under the current operating conditions is less than the minimum shut-off angle of the DC transmission system, then the converter valve that has not experienced a fault is determined to have suffered continuous commutation failure.

[0018] If the shut-off angle under the current operating conditions is greater than the minimum shut-off angle of the DC transmission system, it is determined that the converter valve that has not experienced a fault has not experienced continuous commutation failure.

[0019] Preferably, the shut-off angle under the operating condition is shown in the following formula:

[0020]

[0021] In the formula, g is the shut-off angle under operating conditions, and U L I is the effective value of the line voltage of the commutation voltage. d X is the system DC current. c b is the commutation reactance, and b is the inverter-side lead trigger angle;

[0022] The minimum shut-off angle is shown in the following formula:

[0023]

[0024] In the formula, g min For the minimum shut-off angle, t q The time required for the converter valve to restore its forward blocking capability is T, where T is the commutation period.

[0025] Preferred options also include:

[0026] After the converter valve fault is cleared, analyze whether the clearing of the fault will still lead to the failure of commutation of the faulty converter valve and the converter valve that has not failed, based on the conduction sequence of the converter valve during normal operation of the converter transformer.

[0027] A commutation failure analysis device for a DC transmission system includes: using converter valve failure as an analysis factor for commutation failure in the DC transmission system, including:

[0028] The determination module is used to determine the fault parameters of the converter valve. The fault parameters include the faulty converter valve number, the fault type and the fault duration. The fault type includes control system fault, DC side short circuit fault of converter valve, AC side short circuit fault of converter valve and short circuit fault of converter valve.

[0029] The analysis module is used to analyze whether a fault type will lead to commutation failure of the faulty converter valve based on the conduction sequence of the converter valve during normal operation of the converter transformer, according to different fault types and the duration of the fault.

[0030] The acquisition module is used to acquire the operating parameters of the DC transmission system after the commutation failure if the faulty converter valve fails to commutate. The operating parameters include the converter voltage and DC current of the DC transmission system. Based on the operating parameters, the shut-off angle under the current operating condition is acquired.

[0031] The derivation module is used to analyze whether a non-faulty converter valve will experience continuous commutation failure based on the shut-off angle under the current operating conditions and the conduction sequence of the converter valves during normal operation of the converter transformer.

[0032] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described method for analyzing commutation failures in a DC transmission system.

[0033] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for analyzing commutation failures in a DC transmission system.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] This invention uses converter valve failure as an analytical factor for commutation failure in DC transmission systems. First, it determines the converter valve failure parameters. Then, following the normal operating sequence of the converter valves in the converter transformer, it analyzes the commutation of the faulty converter valves under different failure parameters. Simultaneously, it analyzes various system operating parameters under commutation failure conditions and whether consecutive commutation failures occurred in non-faulty converter valves. This invention's analytical method, starting from the perspective of converter valve failure, obtains the commutation voltage and DC current of the DC transmission system after commutation failure in the case of a faulty valve, and analyzes the problem of excessively small turn-off angles caused by different influencing factors, greatly improving the accuracy of commutation failure analysis results. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a commutation failure analysis method for a DC transmission system according to the present invention;

[0038] Figure 2 This is a structural diagram of a DC transmission system using a twelve-pulse converter, as per the present invention.

[0039] Figure 3 This is a diagram illustrating the valve short-circuit fault types involved in this invention;

[0040] Figure 4 The waveform diagram is for the faulty switching valve V1.

[0041] Wherein, (a): current waveform, (b): voltage waveform;

[0042] Figure 5 The voltage waveform diagrams of each converter valve in the six-pulse converter where the faulty converter valve V1 is located are shown.

[0043] Wherein, (a): voltage waveform of valve V1, (b): voltage waveform of valve V3, (c): voltage waveform of valve V5, (d): voltage waveform of valve V7, (e): voltage waveform of valve V9, (f): voltage waveform of valve V11;

[0044] Figure 6 The current waveforms of each converter valve in the six-pulse converter where the faulty converter valve V1 is located are shown.

[0045] Among them, (a): current waveform of valve V1, (b): current waveform of valve V3, (c): current waveform of valve V5, (d): current waveform of valve V7, (e): current waveform of valve V9, (f): current waveform of valve V11.

[0046] Figure 7 The voltage waveforms of each converter valve in another six-pulse converter are shown.

[0047] Wherein, (a): voltage waveform of valve V2, (b): voltage waveform of valve V4, (c): voltage waveform of valve V6, (d): voltage waveform of valve V8, (e): voltage waveform of valve V10, (f): voltage waveform of valve V12;

[0048] Figure 8 The current waveforms of each converter valve in another six-pulse converter are shown.

[0049] Among them, (a): valve V2 current waveform, (b): valve V4 current waveform, (c): valve V6 current waveform, (d): valve V8 current waveform, (e): valve V10 current waveform, (f): valve V12 current waveform;

[0050] Figure 9 The DC voltage waveform of the DC transmission system under valve V1 failure is shown.

[0051] Figure 10 The DC current waveform of the DC transmission system under valve V1 failure is shown.

[0052] Figure 11 The waveform diagram of the minimum shut-off angle under valve V1 failure;

[0053] Figure 12 The power waveform diagram is shown under the short-circuit fault of valve V1. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] This invention provides a method for analyzing commutation failure in a DC transmission system, specifically a method for analyzing continuous commutation failure under converter valve failure. This invention uses converter valve failure as an analytical factor for commutation failure in the DC transmission system. The causes of commutation failure include two types: commutation failure caused by converter valve failure affecting the normal operation of the converter valve, and insufficient turn-off angle caused by changes in system operating parameters. The converter valve failure affects the normal operation of the converter valve, which may lead to changes in the lead-out angle and a surge in DC current, ultimately potentially causing other converter valves to experience continuous commutation failure due to insufficient turn-off angles. (Refer to...) Figure 1 This includes the following steps:

[0056] Step 1: Determine the fault parameters of the converter valve, including the faulty converter valve number, fault type, and fault duration. Analyze whether the converter valve fault will cause a surge in DC current or a drop in DC voltage, thereby leading to continuous commutation failure. In particular, converter valve faults affect the normal operation of the converter valve, which may lead to changes in the lead firing angle, a surge in DC current, and ultimately cause other converter valves to experience continuous commutation failure due to excessively small shut-off angles.

[0057] Based on fault cases in DC transmission systems, the main fault types of converter valves can be divided into two categories: control system faults and converter valve short-circuit faults. Converter valve short-circuit faults are further divided into AC side short-circuit faults, DC side short-circuit faults, and AC side short-circuit faults. Figure 3 In the diagram, 1-4 represent short circuit faults on the AC side of the converter valve, 5-6 represent short circuit faults on the converter valve, and 7-13 represent short circuit faults on the DC side of the converter valve.

[0058] Based on the actual operation of the converter valve failure, the faulty valve conduction number, fault type, and fault duration are determined. In this example, the failure of the valve V1 bridge arm control system caused the trigger pulse to be lost. The failure time was 0.5s and the failure duration was 0.05s.

[0059] Step 2: Based on different fault types, analyze whether the fault type will lead to the failure of commutation of the faulty commutator valve during the fault duration according to the commutator valve conduction sequence during normal operation of the converter transformer.

[0060] When the fault type is a control system fault, that is, the trigger pulse of the faulty switching valve is lost, if the trigger pulse is lost at the commutation time, the faulty switching valve does not receive the trigger pulse and cannot conduct, resulting in the failure of the switching valve to commutate; if the trigger pulse is lost but does not occur at the commutation time, it will not cause the switching valve to commutate to fail.

[0061] When the fault type is a short circuit fault on the DC side of the converter valve, the converter valve on the inverter side cannot maintain conduction, the DC voltage on the inverter side drops, the DC current jumps, and normal commutation fails. After the fault is cleared, the system can gradually return to normal operation. This fault, once it occurs, will lead to commutation failure; after the fault is cleared, the system can gradually return to normal operation.

[0062] When the fault type is a short circuit fault on the AC side of the converter valve, i.e., a short circuit at the AC outlet of the converter valve, the commutation voltage will drop, causing the faulty converter valve to not bear positive voltage during commutation, thus leading to commutation failure. If the fault does not occur at the commutation time, it will not cause the faulty converter valve to fail to commutate.

[0063] When the fault type is a short circuit fault of the converter valve, the faulty converter valve is short-circuited and continues to conduct, causing a surge in DC current. The faulty converter valve cannot complete the commutation process. If this occurs before commutation to the faulty converter valve, and the short circuit has been cleared when the faulty converter valve commutates to another converter valve, it will not affect the system operation. Otherwise, it will lead to commutation failure.

[0064] Reference Figure 3 When the twelve-pulse converter valve is operating normally, the converter valves will sequentially turn on to achieve mutual conversion between AC and DC. The normal operating sequence is as follows: valves V1, V2, V3, and V4 are initially on; then, valve V1 switches to valve V5, resulting in valves V2, V3, V4, and V5 being on; the next switching process involves valve V2 switching to valve V6, resulting in valves V3, V4, V5, and V6 being on, and so on, until after one cycle, valves V1, V2, V3, and V4 are on again. Throughout the entire valve operating cycle, valves V1, V5, and V9 will sequentially switch phases; valves V2, V6, and V10 will sequentially switch phases; valves V3, V7, and V11 will sequentially switch phases; and valves V4, V8, and V12 will sequentially switch phases.

[0065] In this example, the fault in the converter valve is the loss of the trigger pulse for converter valve V1. The voltage, current, and voltage waveforms of valve V1 are as follows. Figure 4 As shown, trigger pulse loss can occur at any time, but only when the converter valve V9 switches to converter valve V1 will the trigger pulse of converter valve V1 be lost. This will result in converter valve V1 not receiving a trigger pulse during the switchover, preventing it from conducting and thus hindering the commutation process. If the trigger pulse loss occurs at other times, it will not affect the normal operation of the converter valves.

[0066] Step 3: If a converter valve failure leads to a single commutation failure, the DC voltage in the DC transmission system will drop and the DC current will surge, resulting in a decrease in the turn-off angle. If the turn-off angle is too small, the commutation process of the converter valve that did not fail may not be completed. Based on the conduction sequence, the converter valve that caused the change in DC system parameters due to the converter valve failure and thus the commutation failure can be identified.

[0067] Common high-voltage direct current transmission systems such as Figure 2 As shown, the system includes the rectifier-inverter side AC system and its internal impedance, converter transformer, converter valve, smoothing reactor, AC filter, DC filter, reactive power compensation device, etc. In the analysis and calculation of this patent, the AC side system can be treated as equivalent, and the control system of the AC filter is also simplified, assuming that the AC filter is always fully engaged.

[0068] The system's turn-off angle under rated operating conditions is determined by using the system's rated operating parameters. This is because an insufficient turn-off angle will directly cause commutation failure. Under rated conditions, the system's DC voltage U... d =400kV, the effective value of the commutation voltage line voltage is U L =230kV, DC current I d =3000A, the commutation reactance is determined by the parameters of the converter transformer, and the commutation reactance X is measured during the factory test. c =13.838Ω, under rated operating conditions, the inverter-side lead firing angle b = 36°, based on the turn-off angle formula. The system shut-off angle under rated operating conditions can be calculated as g = 17.1°.

[0069] Based on the relevant parameters of the converter valve in the DC transmission system, determine the boundary condition g for commutation failure in the DC transmission system. min g min The time t required for the converter valve to restore its forward blocking capability q This refers to the deionization time of the thyristor carriers in the converter valve. The deionization time of the thyristor used in the system is 850ms, corresponding to a minimum turn-off angle of... T is one commutation cycle, which is the same as the inverter-side AC system cycle of 0.02s. Therefore, the minimum turn-off angle g min =15.3°, and the system's operating turn-off angle under rated operating conditions is g=17.1°. Therefore, when the DC current rises significantly and the DC voltage drops significantly, the operating turn-off angle will be less than the minimum turn-off angle, which will result in commutation failure.

[0070] Because V1 is not conducting properly, when valve V5 receives the trigger pulse, it will experience reverse voltage and will not be able to conduct, thus failing to complete the commutation process. In other words, the loss of the trigger pulse for valve V1 will cause commutation failure for valve V9. Only after the trigger pulse is restored can the valve resume normal operation, resulting in a significant drop in DC voltage and a surge in DC current. Based on... A significant drop in DC voltage and a surge in DC current will cause a sharp decrease in the shut-off angle of the converter valves, exceeding the regulation capacity of the DC transmission control system. This will lead to commutation failure even for converter valves that are not currently experiencing a fault. Based on the conduction sequence of the twelve-pulse converter, it is known that when valve V5 receives the trigger pulse, it cannot conduct due to the reverse voltage, thus failing to complete the commutation process. At this time, the shut-off angles will decrease significantly, therefore converter valves V2 and V4 will experience commutation failure. Figures 7-8 As shown; commutation failure will also occur in converter valve V7, as... Figures 5-6 As shown.

[0071] The analysis examines whether the faulty converter valve can switch phases normally during the next phase switching.

[0072] After one commutation cycle T, i.e., 0.02s, when converter valve V9 commutates to converter valve V1 again, commutation failure will still occur because the trigger pulse has not yet recovered. At this time, because the shut-off angle is still small, commutation failure will also occur between converter valves V2 and V4. Figures 7-8 As shown; the commutation failure also occurred in the converter valve V7, such as Figures 5-6 As shown. After another commutation cycle, the fault is cleared. At this time, although the converter valves V2, V4, and V7 are still in a commutation failure state and the shut-off angle is still small, there is still a risk of commutation failure. If the converter valve V9 successfully commutates to the converter valve V1 at this time, the DC voltage and DC current will gradually begin to recover, and the converter valves V2, V4, and V7 will also gradually return to normal working conditions.

[0073] When the control system of valve V1 malfunctions, it remains closed and cannot conduct normally during the fault period. After the commutation of the converter valve V1 is restored, the converter valves V2 and V4 resume normal operation. However, after the commutation of the converter valve V1 is restored, the converter valve V7 still fails to commutate.

[0074] The changes in system operating parameters caused by the fault were analyzed, and the changes in the operating parameters of each valve under valve failure were determined. Based on this, the operating parameters of the DC transmission system, such as DC voltage, current, and power, were deduced. After the trigger pulse of valve V1 is lost, valve V1 cannot conduct, the valve current remains at 0, and the voltage it withstands is sinusoidal. The loss of the trigger pulse of valve V1 will lead to continuous commutation failure of valve V9, and the duration of continuous commutation failure is related to the duration of the fault. At this time, the DC current will surge, causing the shut-off angle of the other converter valves to be too small, resulting in continuous commutation failure. Ultimately, this will lead to a significant and prolonged drop in DC voltage, which will also reduce the DC transmission power. Finally, the impact of the fault on system operation was determined, such as... Figures 9-12 As shown.

[0075] Based on the same concept, the present invention also provides a commutation failure analysis device for DC transmission systems, including a determination module, an analysis module, an acquisition module, and a derivation module.

[0076] The determination module is used to determine the fault parameters of the converter valve. The fault parameters include the faulty converter valve number, the fault type, and the fault duration. The fault type includes control system fault, DC side short circuit fault of the converter valve, AC side short circuit fault of the converter valve, and short circuit fault of the converter valve.

[0077] The analysis module is used to analyze whether a fault type will lead to commutation failure of the faulty converter valve based on the normal operating sequence of the converter valve during the fault duration, according to different fault types.

[0078] The acquisition module is used to acquire the operating parameters of the DC transmission system after the commutation failure if the faulty converter valve fails to commutate. The operating parameters include the converter voltage and DC current of the DC transmission system; and to acquire the shut-off angle under the current operating condition based on the operating parameters.

[0079] The derivation module is used to analyze whether a non-faulty converter valve will experience continuous commutation failure based on the shut-off angle under the current operating conditions and the conduction sequence of the converter valves during normal operation of the converter transformer.

[0080] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described method for analyzing commutation failures in a DC transmission system.

[0081] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-described method for analyzing commutation failures in a DC transmission system.

[0082] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0083] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for analyzing commutation failure in a DC transmission system, characterized in that, Using converter valve failure as an analytical factor for commutation failure in DC transmission systems includes the following steps: Determine the fault parameters of the converter valve, which include the faulty converter valve number, fault type and fault duration. The fault type includes control system fault, DC side short circuit fault of converter valve, AC side short circuit fault of converter valve and short circuit fault of converter valve. Based on different fault types, during the fault duration, the conduction sequence of the converter valves during normal operation of the converter transformer is analyzed to determine whether the fault type will lead to the failure of the faulty converter valve to switch phases. If the failure of the converter valve leads to commutation failure, the operating parameters of the DC transmission system after the commutation failure are obtained. The operating parameters include the converter voltage and DC current of the DC transmission system. The shut-off angle under the current operating condition is obtained based on the operating parameters. Based on the shut-off angle under the current operating conditions, and according to the conduction sequence of the converter valves during normal operation of the converter transformer, we analyze whether the converter valves that have not experienced faults will experience continuous commutation failures. Based on different fault types, during the fault duration, the analysis considers whether the fault type will lead to commutation failure of the faulty converter valve according to the normal operating sequence of the converter transformer. This includes: When the fault type is a control system fault, that is, the trigger pulse of the faulty switching valve is lost. When the trigger pulse is lost at the commutation time, the faulty switching valve does not receive the trigger pulse and cannot conduct, resulting in the failure of the switching valve to commutate. When the trigger pulse is lost but does not occur at the commutation time, it will not cause the switching valve to commutate. When the fault type is a short circuit fault on the DC side of the converter valve, the converter valve on the inverter side cannot maintain conduction, the DC voltage on the inverter side drops, and normal commutation cannot be performed. Once this fault occurs, it will lead to commutation failure. When the fault type is a short circuit fault on the AC side of the converter valve, that is, a short circuit at the AC side outlet of the converter valve, the commutation voltage drops, causing the faulty converter valve to not bear the positive voltage during commutation, thus leading to commutation failure; when the fault does not occur at the commutation time, it will not cause the faulty converter valve to fail to commutate. When the fault type is a short circuit fault in the converter valve, the faulty converter valve is short-circuited and continues to conduct, preventing the faulty converter valve from completing the commutation.

2. The method for analyzing commutation failure in a DC transmission system as described in claim 1, characterized in that, Based on the shut-off angle under the current operating conditions, and according to the conduction sequence of the converter valves during normal operation of the converter transformer, we analyze whether the converter valves that have not experienced faults will experience continuous commutation failures, including: If the shut-off angle under the current operating conditions is less than the minimum shut-off angle of the DC transmission system, then the converter valve that has not experienced a fault is determined to have suffered continuous commutation failure. If the shut-off angle under the current operating conditions is greater than the minimum shut-off angle of the DC transmission system, it is determined that the converter valve that has not experienced a fault has not experienced continuous commutation failure.

3. The method for analyzing commutation failure in a DC transmission system as described in claim 2, characterized in that, The shut-off angle under the specified operating conditions is shown in the following formula: In the formula, g The shut-off angle under operating conditions. U L This is the effective value of the line voltage of the commutation voltage. I d The system DC current, X c For commutation reactance, b The inverter-side leading trigger angle; The minimum shut-off angle is shown in the following formula: In the formula, The minimum shut-off angle, t q The time required for the converter valve to restore its forward blocking capability. T This is the commutation period.

4. The method for analyzing commutation failure in a DC transmission system as described in claim 1, characterized in that, Also includes: After the converter valve fault is cleared, analyze whether the clearing of the fault will still lead to the failure of commutation of the faulty converter valve and the converter valve that has not failed, based on the conduction sequence of the converter valve during normal operation of the converter transformer.

5. A commutation failure analysis device for a DC transmission system, characterized in that, Using converter valve failure as an analytical factor for commutation failure in DC transmission systems includes: The determination module is used to determine the fault parameters of the converter valve. The fault parameters include the faulty converter valve number, the fault type and the fault duration. The fault type includes control system fault, DC side short circuit fault of converter valve, AC side short circuit fault of converter valve and short circuit fault of converter valve. The analysis module is used to analyze whether a fault type will lead to commutation failure of the faulty converter valve based on the conduction sequence of the converter valve during normal operation of the converter transformer, according to different fault types and the duration of the fault. The acquisition module is used to acquire the operating parameters of the DC transmission system after the commutation failure if the faulty converter valve fails to commutate. The operating parameters include the DC voltage, DC current and lead firing angle of the DC transmission system; and to acquire the turn-off angle under the current operating condition based on the operating parameters. The derivation module is used to analyze whether a non-faulty converter valve will experience continuous commutation failure based on the shut-off angle under the current operating conditions and the conduction sequence of the converter valves during normal operation of the converter transformer. Based on different fault types, during the fault duration, the analysis considers whether the fault type will lead to commutation failure of the faulty converter valve according to the normal operating sequence of the converter transformer. This includes: When the fault type is a control system fault, that is, the trigger pulse of the faulty switching valve is lost. When the trigger pulse is lost at the commutation time, the faulty switching valve does not receive the trigger pulse and cannot conduct, resulting in the failure of the switching valve to commutate. When the trigger pulse is lost but does not occur at the commutation time, it will not cause the switching valve to commutate. When the fault type is a short circuit fault on the DC side of the converter valve, the converter valve on the inverter side cannot maintain conduction, the DC voltage on the inverter side drops, and normal commutation cannot be performed. Once this fault occurs, it will lead to commutation failure. When the fault type is a short circuit fault on the AC side of the converter valve, that is, a short circuit at the AC side outlet of the converter valve, the commutation voltage drops, causing the faulty converter valve to not bear the positive voltage during commutation, thus leading to commutation failure; when the fault does not occur at the commutation time, it will not cause the faulty converter valve to fail to commutate. When the fault type is a short circuit fault in the converter valve, the faulty converter valve is short-circuited and continues to conduct, preventing the faulty converter valve from completing the commutation.

6. A computer device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the DC transmission system commutation failure analysis method according to any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the DC transmission system commutation failure analysis method according to any one of claims 1-4.

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