A maintenance plan adjustment method for converter valves and optical CT based on dynamic alarm function

Abstract

The present invention relates to the field of flexible direct current transmission technology, and specifically discloses a method for adjusting the maintenance plan of a converter valve and an optical CT based on a dynamic alarm function, comprising the following steps: first, establishing a state assessment model for the converter valve bridge arm and the optical CT; then formulating a state opportunity maintenance strategy; establishing an alarm maintenance function, an opportunity maintenance function, and a replacement threshold for each of the converter valve bridge arm and the optical CT; solving the alarm maintenance threshold function and the opportunity maintenance threshold function; replacing the component when the current monitoring value suddenly increases and the state monitoring value exceeds the replacement threshold; comparing the calculated maintenance threshold function in each cycle with the state monitoring value, and finally formulating a suitable combined maintenance strategy. The present invention adopts the above-mentioned method for adjusting the maintenance plan of a converter valve and an optical CT based on a dynamic alarm function, and adjusts the maintenance threshold function according to different maintenance effects and maintenance times, so that it corresponds to the real-time state of the component, thereby ensuring the effectiveness of the maintenance strategy.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible direct current transmission, and in particular to a method for adjusting a converter valve and an optical CT maintenance plan based on a dynamic alarm function. Background Art

[0002] Due to the characteristics of renewable energy generation, such as small generating capacity, unstable output power, and wide distribution areas far from load centers, previous AC transmission technologies and more traditional DC transmission technologies have certain limitations in addressing these issues. Against this backdrop, Flexible DC transmission technology can effectively address these issues. Compared to conventional thyristor-based DC transmission systems, Flexible DC transmission systems offer more flexible operating modes and better system control. The output of renewable energy is significantly affected by external environmental factors, resulting in extremely unstable output power. Through its precise control capabilities, Flexible DC transmission systems can better integrate with this unstable energy source and improve energy efficiency. After the Flexible DC project went into operation, it faced a severe challenge: failures in converter valves and pure optical CTs (current transformers) have repeatedly caused unexpected system outages, posing a serious threat to the safe and stable operation of the Flexible DC grid. Due to the long-term operating characteristics of Flexible DC equipment, unclear fault mechanisms, and inefficient fault analysis and location, maintenance costs are high, and maintenance strategies must be adjusted according to changing operating conditions.

[0003] Current converter valve maintenance strategies often employ a condition-based maintenance approach. This approach bases maintenance decisions on the real-time operating status of components, performing preventive maintenance on degraded components. However, this approach fails to consider the impact of maintenance on subsequent operation. Decisions are made using a fixed maintenance threshold function. As the number of maintenance attempts increases, the misjudgment rate of component degradation increases, compromising the reliability of these decisions. Therefore, a dynamic maintenance schedule adjustment technique based on the Weibull proportional intensity model is urgently needed. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for adjusting the maintenance plan of converter valves and optical CTs based on a dynamic alarm function. This method takes into account the impact of each maintenance on the health status of the components, and different maintenance methods have different degrees of impact on the health status of the components. At the same time, the maintenance threshold function determined based on economic efficiency will also change accordingly and be continuously adjusted. This makes the real-time status assessment more accurate, improves the reliability and economy of decision-making, and ensures the stable and safe operation of the converter station.

[0005] To achieve the above objectives, the present invention provides a method for adjusting the maintenance plan of converter valves and optical CTs based on a dynamic alarm function, comprising the following steps:

[0006] S1. Establish a state assessment model for the converter valve bridge arm and optical CT;

[0007] S2, formulate state opportunity maintenance strategy;

[0008] Establish the alarm maintenance function M of the converter valve bridge arm and optical CT respectively c k , opportunity maintenance function M o k and the replacement threshold M(max). In a converter valve, there are six converter valve bridge arms and two optical CTs, that is, these eight components are divided into a group to formulate a combined maintenance strategy;

[0009] S3, solving the alarm maintenance threshold function and the opportunity maintenance threshold function;

[0010] S4. When the current monitoring value suddenly increases and the status monitoring value exceeds the replacement threshold, the component is replaced;

[0011] S5. Compare the calculated maintenance threshold function in each cycle with the condition monitoring value, and finally formulate a suitable combined maintenance strategy.

[0012] Preferably, in step S1, the specific process of establishing the state assessment model for the converter valve bridge arm and the optical CT is as follows:

[0013] Considering the impact of maintenance effects on the real-time health status of components, a component status assessment model is established as the Weibull proportional strength model. This model considers equipment life, maintenance activities, and status information while calculating the failure rate. Its expression is as follows:

[0014]

[0015] Where β is the shape parameter, η is the life parameter, γ is the p-dimensional vector of the regression coefficients of Z arranged in the corresponding order, Z represents the real-time monitoring value of the covariate, and in the status evaluation of the converter valve and optical CT, the covariate is the current value at each location, T n is the time required for maintenance, ε n is the improvement factor, the value range is [0, 1]. If the minimum maintenance is adopted, ε n =1, if the replacement method is adopted, then ε n =0, β, η, γ are solved by maximum likelihood estimation based on historical fault data and current monitoring values;

[0016] ε n The calculation formula is as follows:

[0017]

[0018] Among them, u is the cost adjustment coefficient, C jxThe cost of maintenance, C gh is the cost of replacement, v is the time coefficient, t is consistent with t in the Weibull proportional strength model, is the component operation time, n is the number of maintenance times, and w is the maintenance coefficient.

[0019] Preferably, in step S2, when the status monitoring value of one component exceeds the alarm maintenance function, the real-time status of other components is monitored, and the components whose real-time status exceeds the alarm maintenance threshold function are overhauled, and the components whose real-time status exceeds the opportunity maintenance threshold function are minor repaired;

[0020] Considering the sudden serious failure of components, a replacement threshold is set. When the component status representation value exceeds the replacement threshold, replacement maintenance measures are taken. Considering that the number of repairs of a component should not be too many, when the number of repairs of the component exceeds the set value, replacement maintenance measures are also taken.

[0021] Preferably, in step S3, the goal of solving the alarm maintenance threshold function is:

[0022] The cost-effectiveness index of preventive overhaul per unit time in a maintenance cycle is the largest. The variable is the overhaul time. The corresponding optimal preventive overhaul time and the current value at the corresponding time are obtained and substituted into the alarm maintenance function.

[0023] The goal of solving the opportunity maintenance threshold function is:

[0024] The maintenance cost of preventive minor repairs per unit time in a maintenance cycle is the lowest. The variable is the minor repair time. The corresponding optimal preventive minor repair time and the current value at the corresponding time are obtained and substituted into the solution to solve the opportunity maintenance function.

[0025] The cost-effectiveness index is the ratio of the difference between the economic benefits brought by maintenance and the cost required for maintenance to the maintenance cycle.

[0026] Preferably, in step S3, the alarm maintenance threshold function M is obtained by rewriting the proportional strength model c (t) and the opportunity maintenance threshold function M o (t) is expressed as follows:

[0027]

[0028] Among them, β and η are known, ε n T n Solve according to the maintenance situation, so the unknown quantity in the maintenance threshold function is H c and H o , H c and H o The two unknowns are expressed as:

[0029]

[0030] For any component i, in the two maintenance threshold expressions of the alarm maintenance threshold and the opportunity maintenance threshold, the unknown quantities are the optimal overhaul time, the optimal minor repair time and the current value at the corresponding time. Substitute them into the expression to find H c and H o , and then solve to obtain the alarm maintenance threshold function and opportunity maintenance threshold function of component i.

[0031] Preferably, in step S3, in the first maintenance cycle, since all components are not repaired, ε0T0=0, and the failure function expression in this cycle is:

[0032]

[0033] The process of solving the alarm maintenance threshold function is as follows: Based on the relevant knowledge of reliability theory, let the reliability function of the component life X be R(x), the time interval from the last preventive maintenance moment to the next preventive maintenance moment be called the maintenance cycle, let the preventive maintenance cycle be T, and E(Y) represent the average length of the state maintenance cycle, then:

[0034]

[0035] Maintenance costs within the cycle C c It consists of two parts: the cost of maintenance implementation C m and decision misjudgment costs C n ;

[0036] Cost of repair implementation C m : Let the breakdown repair cost be C1, which includes downtime loss, fixed repair cost and equipment breakdown repair fee; let the preventive overhaul cost be C2, which includes downtime loss, fixed repair cost and equipment overhaul fee, then:

[0037] C m =C1N1+C2R(x)

[0038] Where N is the predicted number of failures in one cycle, expressed as follows:

[0039]

[0040] Costs incurred due to misjudgment of decision-making C n : Decision misjudgment includes two situations: fault misjudgment and fault omission. Let the subsequent cost caused by fault misjudgment be C4, the loss caused by fault omission be C5, the probability of misjudgment be P1, and the probability of omission be P2:

[0041] C n=P1·E(Y)·C4+P2·E(Y)·C5

[0042] C c =C m +C n

[0043] Assume that the economic benefit generated by maintenance during the period is W c , which is the benefit brought by the reduced downtime. Assuming the loss caused by the shutdown of the converter valve system per unit time is Q1, we have:

[0044] Q c =(TE(Y))·Q1

[0045] Assume that the cost-effectiveness index is k1:

[0046]

[0047] Derivative T of the above formula and set it to zero to solve the optimal overhaul time T1. The current value at the corresponding moment is the optimal overhaul state value Z. c , T1 and Z c Substitute it into the state maintenance threshold expression to calculate the alarm maintenance threshold function with the lowest cost.

[0048] Preferably, in step S3, the process of solving the opportunity maintenance threshold function is:

[0049] Assume that the minimum maintenance cost after a failure is C3, which includes downtime loss, fixed maintenance costs and equipment minor repair costs. Minimum maintenance means that the component is restored to normal operation through maintenance, but the failure rate within the component has the same trend as before the maintenance. The cost of preventive overhaul is C2; since the failure rate of the component after the minimum maintenance has the same trend as before the maintenance, the average length of the component's opportunity maintenance cycle is constant, T; the maintenance cost within the cycle is C u It also consists of two parts, namely the cost of maintenance implementation C s and decision misjudgment costs C g ;

[0050] The cost C required for maintenance implementation within period T s for:

[0051]

[0052] Assume that the subsequent cost caused by fault misjudgment is C6, the loss caused by fault omission is C7, the probability of misjudgment is P3, and the probability of omission is P4, then the cost of decision misjudgment is C q for:

[0053] C q=P3·T·C6+P4·T·C7

[0054] C u =C s +C q

[0055] The cost per unit time for preventive minor repairs is k2:

[0056]

[0057] Derivative the above formula with respect to T and set it to zero to solve the optimal opportunity maintenance time T o , find the current value at the corresponding moment, which is the optimal minor repair state value Z o ; T o and Z o Substitute it into the calculation formula of the threshold function to solve the opportunity maintenance threshold function;

[0058] After the first combined maintenance, considering the maintenance effect ε n T n is not 0; then the failure function expression in the second maintenance cycle is:

[0059]

[0060] Where T1 is the time required for the first maintenance, ε1 determines the maintenance cost based on the first maintenance method, and ε1 is considered as a function of the running time t. The maintenance threshold function of the second cycle is:

[0061]

[0062] Using the above method to solve, we can get the maintenance threshold function of the second cycle;

[0063] After each component maintenance, the correlation coefficient of the improvement factor ε is determined according to the maintenance method, and it is iterated on the failure function of the previous maintenance cycle. Then, the maintenance threshold function is updated using the method that minimizes the maintenance cost per unit time.

[0064] Therefore, the present invention adopts the above-mentioned method for adjusting the maintenance plan of the converter valve and optical CT based on the dynamic alarm function, and the beneficial effects are as follows:

[0065] (1) Compared with the conventional fixed maintenance threshold function, the present invention can continuously adjust the maintenance threshold function as the maintenance progresses, thereby making a more accurate judgment on whether the component status has deteriorated.

[0066] (2) The present invention takes into account that different types of maintenance methods generate different maintenance costs and maintenance times, which causes the value of the improvement factor to fluctuate accordingly. The improvement factor expression is used to accurately describe the maintenance effect, thereby accurately calculating the degree of state regression.

[0067] (3) The present invention takes into account sudden serious faults and sets a replacement threshold to ensure safe and reliable operation of the system; considers the impact of maintenance on component performance and sets a maximum number of component maintenance times. Components that reach the maximum number of maintenance times are replaced to ensure efficient operation of each component; at the same time, the maintenance threshold function is updated after the component is replaced, and it is iterated again with the maintenance, thereby obtaining a more complete dynamic adjustment system.

[0068] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is an overall flow chart of an embodiment of a method for adjusting a converter valve and optical CT maintenance plan based on a dynamic alarm function according to the present invention;

[0070] Figure 2 This is a topological diagram of a flexible DC converter valve according to an embodiment of a method for adjusting a converter valve and an optical CT maintenance plan based on a dynamic alarm function of the present invention;

[0071] Figure 3 It is a maintenance decision diagram of each component in an embodiment of a method for adjusting a maintenance plan of a converter valve and an optical CT based on a dynamic alarm function of the present invention. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0073] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0074] After a component undergoes preventive overhaul or minor repair, its health status changes to a certain extent. The repair effect is somewhere between replacement ("restored to like-new") and minimal repair ("restored to like-new"). Therefore, as the number of component repairs increases, the initially set maintenance threshold function will begin to mismatch the component's real-time status. This increases the misjudgment rate of component degradation, affecting the reliability of maintenance decisions. Therefore, a dynamic adjustment technology is needed. This technology adjusts the maintenance threshold function based on the repair effect and number of repairs as the component undergoes repair, ensuring that it corresponds to the component's real-time status and ensuring the effectiveness of the maintenance strategy.

[0075] like Figure 1 As shown, a method for adjusting the maintenance plan of a converter valve and an optical CT based on a dynamic alarm function includes the following steps:

[0076] In the combined operation and maintenance of the converter valve and optical CT, the six bridge arms of the converter valve are regarded as six independent research objects, and the optical CTs in the two DC lines are regarded as two research objects, that is, a combined maintenance strategy for these eight components is considered.

[0077] S1. Establish a condition assessment model for the converter valve bridge arm and optical CT, i.e., a proportional intensity model that considers the impact of maintenance effects on real-time conditions. The specific process is as follows:

[0078] The flexible DC converter valve is the core component of the flexible DC transmission system, used to achieve AC / DC conversion and control. The flexible DC converter valve usually adopts a multi-stage rectifier bridge or inverter bridge topology, equipped with a control circuit and power switching devices to achieve AC to DC and DC to AC conversion. The topology of the flexible DC converter valve is as follows: Figure 2 shown.

[0079] SM1, SM2, ..., SMN are half-bridge sub-modules used to build full-bridge or multi-level converter topologies. In these topologies, multiple half-bridge sub-modules can be combined in series or parallel to achieve higher power AC to DC or DC to AC conversion.

[0080] In the maintenance strategy, the bridge arm of one phase of the converter valve is treated as an integrated maintenance component. If its operating condition deteriorates, the bridge arm is repaired. A converter valve consists of six bridge arms, which means it is divided into six independent components.

[0081] A photocurrent transformer (photoCT) is a sensor device used to measure current. It uses optical principles to achieve non-contact current measurement. Compared with traditional current transformers (CTs), photocurrent transformers have higher accuracy and lower losses. Therefore, they are widely used when high-precision current measurement is required and in power system status monitoring.

[0082] In the flexible DC converter valve, each converter valve corresponds to two optical CTs, which are installed in the two DC lines leading out of the converter valve respectively. They can cooperate with the hybrid circuit breaker to protect the circuit and control the circulation of the converter valve.

[0083] Considering the impact of maintenance effects on the real-time health status of components, a component status assessment model is established, which is the Weibull proportional strength model. This model considers equipment life, maintenance activities, and status information while calculating the failure rate, thereby providing a more comprehensive assessment of the equipment status. Its expression is as follows:

[0084]

[0085] Where β is the shape parameter, η is the life parameter, γ is the p-dimensional vector of the regression coefficients of Z arranged in the corresponding order, Z represents the real-time monitoring value of the covariate, and in the status evaluation of the converter valve and optical CT, the covariate is the current value at each location, T n is the time required for maintenance, ε n is the improvement factor, the value range is [0, 1]. If the minimum maintenance is adopted, ε n =1, if the replacement method is adopted, then ε n =0, β, η, γ are solved by maximum likelihood estimation based on historical fault data and current monitoring values.

[0086] ε n The calculation formula is as follows:

[0087]

[0088] Among them, u is the cost adjustment coefficient, C jx The cost of maintenance, C gh is the replacement cost, v is the time coefficient, t (which corresponds to t in the Weibull proportional intensity model) is the component operating time, n is the number of maintenance cycles, and w is the maintenance coefficient. Based on this, a condition assessment model for the converter valve bridge arm and optical CT can be established.

[0089] S2, formulate state opportunity maintenance strategy;

[0090] Establish the alarm maintenance function M of the converter valve bridge arm and optical CT respectively k , opportunity maintenance function M o k And the replacement threshold M(max), in a converter valve, including six converter valve bridge arms and two optical CTs, that is, these eight components are divided into a group to formulate a combined maintenance strategy. When the status monitoring value of one component exceeds the alarm maintenance function M c k When the real-time status of other components exceeds the alarm maintenance threshold function M c k The components are overhauled, and the real-time status of other components exceeds the opportunity maintenance threshold function M o k Minor repairs are performed on the components; and maintenance measures are taken only when the status representation values of other components exceed the alarm maintenance function.

[0091] At the same time, considering the sudden serious failure of the component, a replacement threshold is set. When the component status representation value exceeds the replacement threshold M(max), the replacement maintenance measure is immediately taken to prevent further impact on the normal operation of other components. In addition, considering that the number of repairs of a component should not be too many, when the number of repairs of the component exceeds the set value N, the replacement maintenance measure is also taken. The maintenance decision of each component is as follows: Figure 3 shown.

[0092] S3, solving the alarm maintenance threshold function and the opportunity maintenance threshold function;

[0093] Given the economic efficiency, the goal of solving the alarm maintenance threshold function is:

[0094] Maximize the cost-effectiveness index of preventive overhaul within a maintenance cycle unit time. The variable is overhaul time. Obtain the corresponding optimal preventive overhaul time and the state representation value (current value) under the corresponding time. Substitute them to solve the alarm maintenance function.

[0095] The goal of solving the opportunity maintenance threshold function is:

[0096] The maintenance cost per unit time of preventive minor repairs within a maintenance cycle is minimized. The variable is the minor repair time. The corresponding optimal preventive minor repair time and the state representation value (current value) at the corresponding time are obtained and substituted into the solution to solve the opportunity maintenance function.

[0097] The cost-effectiveness index is the ratio of the difference between the economic benefits brought by maintenance and the cost required for maintenance to the maintenance cycle. The larger the index value, the better the maintenance effect.

[0098] However, due to the existence of the improvement factor, the optimal maintenance time after each maintenance changes, and the maintenance threshold function also changes. The main factors causing fluctuations are the changes in the improvement factor over time and the number of maintenance times, as well as the differences in the maintenance time required under different maintenance methods. In the first maintenance cycle, ε n and T n are both 0, and the two maintenance threshold functions are calculated on this basis; but after taking maintenance action, ε n and T n If the value of changes, the corresponding two maintenance threshold functions change accordingly. Each subsequent maintenance action will cause the maintenance threshold function to change. Therefore, the algorithm iterates the maintenance threshold function until the component is replaced, restoring the component to like-new condition, and then recalculates the maintenance threshold function. Furthermore, when the component's condition representation value exceeds the replacement threshold, the maintenance action of replacement is immediately taken, and the component's condition is also restored to like-new condition.

[0099] Specifically, the alarm maintenance threshold function M is obtained by rewriting the proportional intensity model c (t) and the opportunity maintenance threshold function M o (t) is expressed as follows:

[0100]

[0101] Among them, β and η are known, ε n T nIt can be solved according to the maintenance situation, so the unknown quantity in the maintenance threshold function is H c and H o , H c and H o The two unknowns are expressed as:

[0102]

[0103] For any component i, in the two maintenance threshold expressions of the alarm maintenance threshold and the opportunity maintenance threshold, the unknown quantities are the optimal overhaul time, the optimal minor repair time and the current value at the corresponding time. Substitute them into the expression to find H c and H o , and then solve to obtain the alarm maintenance threshold function and opportunity maintenance threshold function of component i.

[0104] In the first maintenance cycle, since all components are not repaired, ε0T0=0, and the failure function expression in this cycle is:

[0105]

[0106] First, the process of solving the alarm maintenance threshold function is as follows: According to the relevant knowledge of reliability theory, let the reliability function of component life X be R(x), the time interval from the last preventive maintenance moment to the next preventive maintenance moment is called the maintenance cycle, let the preventive maintenance cycle be T, and E(Y) represent the average length of the condition maintenance cycle, then:

[0107]

[0108] Maintenance costs within the cycle C c It consists of two parts: the cost of maintenance implementation C m and decision misjudgment costs C n ;

[0109] Cost of repair implementation C m : Let the breakdown repair cost be C1, which includes downtime loss, fixed repair cost and equipment breakdown repair fee; let the preventive overhaul cost be C2, which includes downtime loss, fixed repair cost and equipment overhaul fee, then:

[0110] C m =C1N1+C2R(x)

[0111] Where N is the predicted number of failures in one cycle, expressed as follows:

[0112]

[0113] Costs incurred due to misjudgment of decision-making C n: Decision misjudgment includes two situations: fault misjudgment and fault omission. Let the subsequent cost caused by fault misjudgment be C4, the loss caused by fault omission be C5, the probability of misjudgment be P1, and the probability of omission be P2:

[0114] C n =P1·E(Y)·C4+P2·E(Y)·C5

[0115] C c =C m +C n

[0116] Assume that the economic benefit generated by maintenance during the period is W c , which is the benefit brought by the reduced downtime. Assuming the loss caused by the shutdown of the converter valve system per unit time is Q1, we have:

[0117] W c =(TE(Y))·Q1

[0118] Assume that the cost-effectiveness index is k1:

[0119]

[0120] In order to maximize the cost-effectiveness index per unit time, the above formula is differentiated with respect to T and set to zero to solve the optimal overhaul time T1. The current value at the corresponding moment is the optimal overhaul state value Z. c , T1 and Z c Substitute it into the state maintenance threshold expression to calculate the alarm maintenance threshold function with the lowest cost.

[0121] Secondly, the process of solving the opportunity maintenance threshold function is:

[0122] Assume that the minimum maintenance cost after a failure is C3, which includes downtime losses, fixed maintenance costs, and equipment minor repair costs. Minimum maintenance means that the component is restored to normal operation through maintenance, but the failure rate within the component has the same trend as before the maintenance. The cost of preventive overhaul is C2; since the failure rate of the component after the minimum maintenance has the same trend as before the maintenance, the average length of the component's opportunity maintenance cycle is constant, T; the cost of maintenance within the cycle is C u It also consists of two parts, namely the cost of maintenance implementation C s and decision misjudgment costs C q ;

[0123] The cost C required for maintenance implementation within period T s for:

[0124]

[0125] Assume that the subsequent cost caused by fault misjudgment is C6, the loss caused by fault omission is C7, the probability of misjudgment is P3, and the probability of omission is P4, then the cost of decision misjudgment is C q for:

[0126] C q =P3·T·C6+P4·T·C7

[0127] C u =C s +C q

[0128] The cost per unit time for preventive minor repairs is k2:

[0129]

[0130] Derivative the above formula with respect to T and set it to zero to solve the optimal opportunity maintenance time T o , find the current value at the corresponding moment, which is the optimal minor repair state value Z o ; T o and Z o Substituting this into the calculation formula of the threshold function, the opportunity maintenance threshold function can be solved.

[0131] After the first combined maintenance, considering the maintenance effect ε n T n is not 0; then the failure function expression in the second maintenance cycle is:

[0132]

[0133] Where T1 is the time required for the first maintenance, ε1 can determine the maintenance cost based on the first maintenance method, and ε1 can be regarded as a function of the running time t. The maintenance threshold function of the second cycle is:

[0134]

[0135] Similarly, the above method is used to solve and obtain the maintenance threshold function of the second cycle;

[0136] Similarly, after each component maintenance, the correlation coefficient of the improvement factor ε is determined according to the maintenance method, and it is iterated on the failure function of the previous maintenance cycle. Then, the maintenance threshold function is updated using the method that minimizes the maintenance cost per unit time to ensure the effectiveness of the threshold function setting.

[0137] S4. Considering the emergency fault situation, when the current monitoring value suddenly increases and the status monitoring value exceeds the replacement threshold, in order to ensure the safe operation of the converter valve, the component is replaced, that is, the status is restored to be as good as new, ∑ε n T nBack off to 0, and the repair threshold function iterates again.

[0138] In addition, considering that the number of maintenance times of a component should not be too many, when the number of maintenance times of the component exceeds the set value N, the maintenance measure of replacement is also taken, and the maintenance threshold function is also updated accordingly.

[0139] S5. Compare the calculated maintenance threshold function in each cycle with the condition monitoring value, and finally formulate a suitable combined maintenance strategy.

[0140] Therefore, the present invention adopts the above-mentioned method for adjusting the maintenance plan of the converter valve and optical CT based on the dynamic alarm function. As the components are maintained, the maintenance threshold function is adjusted according to different maintenance effects and maintenance times to make it correspond to the real-time status of the components, thereby ensuring the effectiveness of the maintenance strategy.

[0141] 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 the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for adjusting the maintenance plan of converter valves and optical CTs based on a dynamic alarm function, characterized in that: The following steps are involved: S1. Establish a state assessment model for the converter valve bridge arm and optical CT; S2, formulate state opportunity maintenance strategy; Establish the alarm maintenance function M of the converter valve bridge arm and optical CT respectively c k , opportunity maintenance function M o k and the replacement threshold M(max). In a converter valve, there are six converter valve bridge arms and two optical CTs, that is, these eight components are divided into a group to formulate a combined maintenance strategy; S3, solving the alarm maintenance threshold function and the opportunity maintenance threshold function; S4. When the current monitoring value suddenly increases and the status monitoring value exceeds the replacement threshold, the component is replaced; S5. Compare the calculated maintenance threshold function in each cycle with the condition monitoring value and ultimately formulate an appropriate combined maintenance strategy; In step S1, the specific process of establishing the state assessment model for the converter valve bridge arm and the optical CT is as follows: Considering the impact of maintenance effects on the real-time health status of components, a component status assessment model is established as the Weibull proportional strength model. This model considers equipment life, maintenance activities, and status information while calculating the failure rate. Its expression is as follows: Where β is the shape parameter, η is the life parameter, γ is the p-dimensional vector of the regression coefficients of Z arranged in the corresponding order, Z represents the real-time monitoring value of the covariate, and in the status evaluation of the converter valve and optical CT, the covariate is the current value at each location, T n is the time required for maintenance, ε n is the improvement factor, the value range is [0,1]. If the minimum maintenance is adopted, ε n =1, if the replacement method is adopted, then ε n =0, β, η, γ are solved by maximum likelihood estimation based on historical fault data and current monitoring values; ε n The calculation formula is as follows: Among them, u is the cost adjustment coefficient, C jx The cost of maintenance, C gh is the cost required for replacement, v is the time coefficient, t is consistent with t in the Weibull proportional strength model, is the component operation time, n is the number of maintenance times, and w is the maintenance coefficient; In step S3, the alarm maintenance threshold function M is obtained by rewriting the proportional strength model c (t) and the opportunity maintenance threshold function M o (t) is expressed as follows: Among them, β and η are known, ε n T n Solve according to the maintenance situation, so the unknown quantity in the maintenance threshold function is H c and H o , H c and H o The two unknowns are expressed as: For any component i, in the two maintenance threshold expressions of the alarm maintenance threshold and the opportunity maintenance threshold, the unknown quantities are the optimal overhaul time, the optimal minor repair time and the current value at the corresponding time. Substitute them into the expression to find H c and H o , and then solve to obtain the alarm maintenance threshold function and opportunity maintenance threshold function of component i.

2. The method for adjusting the maintenance plan of converter valves and optical CTs based on a dynamic alarm function according to claim 1, characterized in that: In step S2, when the status monitoring value of one component exceeds the alarm maintenance function, the real-time status of other components is monitored, and the components whose real-time status exceeds the alarm maintenance threshold function are overhauled, and the components whose real-time status exceeds the opportunity maintenance threshold function are minor repaired; Considering the sudden serious failure of components, a replacement threshold is set. When the component status representation value exceeds the replacement threshold, replacement maintenance measures are taken. Considering that the number of repairs of a component should not be too many, when the number of repairs of the component exceeds the set value, replacement maintenance measures are also taken.

3. The method for adjusting the maintenance plan of converter valves and optical CTs based on dynamic alarm functions according to claim 2, characterized in that: In step S3, the goal of solving the alarm maintenance threshold function is: The cost-effectiveness index of preventive overhaul per unit time in a maintenance cycle is the largest. The variable is the overhaul time. The corresponding optimal preventive overhaul time and the current value at the corresponding time are obtained and substituted into the alarm maintenance function. The goal of solving the opportunity maintenance threshold function is: The maintenance cost of preventive minor repairs per unit time in a maintenance cycle is the lowest. The variable is the minor repair time. The corresponding optimal preventive minor repair time and the current value at the corresponding time are obtained and substituted into the solution to solve the opportunity maintenance function. The cost-effectiveness index is the ratio of the difference between the economic benefits brought by maintenance and the cost required for maintenance to the maintenance cycle.

4. The method for adjusting the maintenance plan of converter valves and optical CTs based on dynamic alarm functions according to claim 3, characterized in that: In step S3, in the first maintenance cycle, since all components are not repaired, ε0T0=0, and the failure function expression in this cycle is: The process of solving the alarm maintenance threshold function is as follows: Based on the relevant knowledge of reliability theory, let the reliability function of the component life X be R(x), the time interval from the last preventive maintenance moment to the next preventive maintenance moment be called the maintenance cycle, let the preventive maintenance cycle be T, and E(Y) represent the average length of the state maintenance cycle, then: Maintenance costs within the cycle C c It consists of two parts: the cost of maintenance implementation C m and decision misjudgment costs C n ; Cost of repair implementationc m : Let the breakdown repair cost be C1, which includes downtime loss, fixed repair cost and equipment breakdown repair fee; let the preventive overhaul cost be c2, which includes downtime loss, fixed repair cost and equipment overhaul fee, then: C m =C1N1+C2R(x) Where N is the predicted number of failures in one cycle, expressed as follows: Costs incurred due to misjudgment of decision-making C n : Decision misjudgment includes two situations: fault misjudgment and fault omission. Let the subsequent cost caused by fault misjudgment be C4, the loss caused by fault omission be C5, the probability of misjudgment be P1, and the probability of omission be P2: C n =P1·E(Y)·C4+P2·E(Y)·C5 C c =C m +C n Assume that the economic benefit generated by maintenance during the period is W c , which is the benefit brought by the reduced downtime. Assuming the loss caused by the shutdown of the converter valve system per unit time is Q1, we have: W c =(T-E(Y))·Q1 Assume that the cost-effectiveness index is k1: Derivative T of the above formula and set it to zero to solve the optimal overhaul time T1. The current value at the corresponding moment is the optimal overhaul state value Z. c , T1 and Z c Substitute it into the state maintenance threshold expression to calculate the alarm maintenance threshold function with the lowest cost.

5. The method for adjusting the maintenance plan of converter valves and optical CTs based on dynamic alarm functions according to claim 4, characterized in that: In step S3, the process of solving the opportunity maintenance threshold function is: Assume that the minimum maintenance cost after a failure is C3, which includes downtime loss, fixed maintenance costs and equipment minor repair costs. Minimum maintenance means that the component is restored to normal operation through maintenance, but the failure rate within the component has the same trend as before the maintenance. The cost of preventive overhaul is C2; since the failure rate of the component after the minimum maintenance has the same trend as before the maintenance, the average length of the component's opportunity maintenance cycle is constant, T; the maintenance cost within the cycle is C u It also consists of two parts, namely the cost of maintenance implementation C s and decision misjudgment costs C q ; The cost C required for maintenance implementation within period T s for: Assume that the subsequent cost of fault misjudgment is C6, the loss caused by fault omission is C7, the probability of misjudgment is P3, and the probability of omission is P4, then the cost of decision misjudgment is C q for: C q =P3·T·C6+P4·T·C7 C u =C s +C q The cost per unit time for preventive minor repairs is l2: Derivative the above formula with respect to T and set it to zero to solve the optimal opportunity maintenance time T o , find the current value at the corresponding moment, which is the optimal minor repair state value Z o ; T o and Z o Substitute it into the calculation formula of the threshold function to solve the opportunity maintenance threshold function; After the first combined maintenance, considering the maintenance effect ε n T n is not 0; then the failure function expression in the second maintenance cycle is: Where T1 is the time required for the first maintenance, ε1 determines the maintenance cost based on the first maintenance method, and ε1 is considered as a function of the running time t. The maintenance threshold function of the second cycle is: Using the above method to solve, we can get the maintenance threshold function of the second cycle; After each component maintenance, the correlation coefficient of the improvement factor ε is determined according to the maintenance method, and it is iterated on the failure function of the previous maintenance cycle. Then, the maintenance threshold function is updated using the method that minimizes the maintenance cost per unit time.

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