Method for determining the number of occurrences of maintenance types of a hybrid converter station system

Abstract

The application provides a method for determining the number of occurrences of maintenance types of a hybrid converter station system, comprising the following steps: S101, acquiring initial operation life of each element in the system; S102, determining an initial life matrix based on the initial operation life of each element; S103, determining a residual life matrix based on the initial life matrix; S104, determining comprehensive residual life of the converter system based on the residual life matrix; S105, determining a maintenance type in a current operation cycle of the system based on the comprehensive residual life of the converter system; and S106, determining the number of occurrences of each maintenance type in a simulation iteration cycle of the system based on the maintenance type in the current operation cycle of the system. The prediction accuracy of the maintenance number model is improved through multiple simulation iterations, and a more accurate quantitative theoretical basis is provided for formulating an optimal maintenance strategy under the premise of ensuring reliable operation of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power systems, in particular to a method for determining the number of occurrences of maintenance types of a hybrid converter station system. BACKGROUND

[0002] The installed capacity of new energy represented by wind power and photovoltaic power continues to grow rapidly, while technical problems such as insufficient grid strength and transient overvoltage have also become prominent, which puts forward higher requirements for high-voltage, large-capacity and long-distance DC power transmission technology. At present, the mainstream technical solutions for DC power transmission are based on two topologies of line commutated converter (LCC) and modular multilevel converter (MMC). Although LCC has large capacity and low loss, it is prone to commutation failure risk; while MMC has flexible power regulation and low harmonic content, it is limited by the performance of IGBT devices, resulting in limited transmission capacity. Therefore, considering the advantages of the two converter topologies, building an LCC-MMC hybrid DC power transmission system has become a current research hotspot, which solves the problem that a single topology cannot meet the demand of new energy transmission, and promotes the diversification of DC power transmission topology structure.

[0003] The hybrid converter station meets the multiple needs of new energy transmission, but also brings complex power system design and operation requirements. In order to ensure the long-term operation of the converter station, not only the electrical performance of the converter station itself is challenged, but also higher requirements are put forward for the optimization of the later operation and maintenance strategy. The number of maintenance times is a key indicator in the optimization of the operation and maintenance strategy, and its accurate quantitative analysis can provide scientific decision basis for optimizing the strategy cost while ensuring the reliability of the equipment in actual engineering. However, the traditional calculation of the number of maintenance times is often based on ideal operating conditions, for example, the coupling relationship between the converter station equipment is ignored, and different fault modes in different life cycle stages of the same equipment are not considered, which may cause some differences from the actual engineering maintenance, and then affect the operation reliability and cost benefit of the converter station. SUMMARY

[0004] In order to overcome the above technical defects, the present application provides a method for determining the number of occurrences of maintenance types of a hybrid converter station system, in order to achieve the above purpose, the present application is realized according to the following technical scheme:

[0005] The present application provides a method for determining the number of occurrences of maintenance types of a hybrid converter station system, comprising:

[0006] Step S101: obtaining the initial operating life of each element in the system;

[0007] Step S102: determining an initial life matrix based on the initial operating life of each element;

[0008] Step S103: determining a residual life matrix based on the initial life matrix, the residual life matrix being a matrix of elements that are detected and not replaced in the current operation cycle;

[0009] Step S104: determining a comprehensive residual life of the converter system based on the residual life matrix;

[0010] Step S105: determining a maintenance type in the current operation cycle of the system based on the comprehensive residual life of the converter system;

[0011] Step S106: determining a number of occurrences of each maintenance type in a simulation iteration cycle of the system based on the maintenance type in the current operation cycle of the system.

[0012] Optionally, the initial operation life of each element in the system is determined in the following manner:

[0013] The initial operation life of each element in the system is determined by using a probability sampling method.

[0014] Optionally, the initial life matrix is determined based on the initial operation life of each element, including:

[0015] After the initial operation life of each element is classified according to a preset element type, the initial life matrix is formed by block storage.

[0016] Optionally, the residual life matrix is determined based on the initial life matrix, including:

[0017] A unit matrix of the same dimension and a current operation cycle working duration are obtained, the current operation cycle working duration being a working duration determined in a previous operation cycle;

[0018] The residual life matrix is determined based on the initial life matrix, the current operation cycle working duration and the unit matrix.

[0019] Optionally, the comprehensive residual life of the converter system is determined based on the residual life matrix, including:

[0020] The residual life matrix is sorted in ascending order according to the initial operation life of the elements in each block to obtain a block life matrix after sorting;

[0021] A redundant configuration of elements in the system topology is obtained;

[0022] The comprehensive residual life of the converter system is determined based on the redundant configuration of elements in the system topology and the block life matrix.

[0023] Optionally, the determining the maintenance type in the current operation cycle of the system based on the comprehensive residual life of the converter system comprises:

[0024] determining whether the comprehensive residual life of the converter system is less than a preset maintenance cycle;

[0025] if yes, determining that the maintenance type in the current operation cycle of the system is failure maintenance;

[0026] if no, determining that the maintenance type in the current operation cycle of the system is preventive maintenance.

[0027] Optionally, the determining the number of occurrences of each maintenance type in the simulation iteration cycle based on the maintenance type in the current operation cycle of the system comprises:

[0028] performing failure maintenance;

[0029] determining a working duration of a next operation cycle based on the comprehensive residual life of the converter system and the preset maintenance cycle;

[0030] sampling and replacing elements in the block life matrix that are less than the working duration of the current operation cycle, and taking the block life matrix after the sampling and replacing as an initial life matrix of the next operation cycle;

[0031] determining whether the total system operation time reaches a first preset duration;

[0032] if yes, determining the number of occurrences of each maintenance type in the total system operation time;

[0033] determining whether the current simulation iteration number reaches a first preset iteration number;

[0034] if yes, determining the number of occurrences of each maintenance type in the simulation iteration cycle;

[0035] if no, performing steps S101-S106 for next simulation iteration calculation.

[0036] Optionally, when the determination result of whether the total system operation time reaches the first preset duration is no, the subsequent steps are:

[0037] performing steps S103-S105.

[0038] Optionally, the determining the number of occurrences of each maintenance type in the simulation iteration cycle based on the maintenance type in the current operation cycle of the system further comprises:

[0039] performing preventive maintenance;

[0040] determining a working duration of a next operation cycle based on the comprehensive residual life of the converter system and the preset maintenance cycle;

[0041] sampling replacement is performed on the elements in the block life matrix whose working time is less than the current operation cycle, and the block life matrix after the sampling replacement is taken as the initial life matrix of the next operation cycle;

[0042] determining whether the current total system running time reaches a first preset time length;

[0043] if yes, determining the occurrence number of each maintenance type within the current total system running time;

[0044] determining whether the current simulation iteration number reaches a first preset iteration number;

[0045] if yes, determining the occurrence number of each maintenance type within the simulation iteration cycle;

[0046] if no, performing steps S101-S106 to perform next simulation iteration calculation.

[0047] Optionally, when the determination result of whether the current total system running time reaches the first preset time length is no, the subsequent steps are:

[0048] performing steps S103-S105.

[0049] The present application has the following beneficial effects:

[0050] The method provided by the present application introduces the converter station reliability index to predict the failure rate required in the sampling process, so as to ensure the credibility of the life prediction result, in view of the influence of dynamic factors such as equipment aging and the mutual influence mechanism among modules on the operation and maintenance process; the initial life of the operation cycle is updated by positioning and replacing the faulty elements, so as to reflect the "local life updating" characteristics in engineering practice, and realize accurate analytical calculation of the occurrence number of each type of maintenance in the hybrid converter station; at the same time, the prediction accuracy of the maintenance number model is improved through multiple simulation iterations, so as to provide more accurate quantitative theoretical basis for formulating an optimal maintenance strategy under the premise of ensuring the reliable operation of the system.

[0051] In addition to the purposes, features and advantages described above, the present application has other purposes, features and advantages. The present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0052] The accompanying drawings, which form a part of the present application, are included to provide a further understanding of the present application, and are incorporated herein for purposes of illustrating the illustrative embodiments of the present application and the explanations provided herein. In the drawings:

[0053] Figure 1 is a flowchart of a method for determining the occurrence number of maintenance types in a hybrid converter station system provided by an embodiment of the present application.

[0054] Figure 2 is a schematic diagram of a main circuit of a modular multilevel converter provided by an embodiment of the present application;

[0055] Figure 3 is a schematic diagram of a main circuit of a line-commutated converter system provided by an embodiment of the present application;

[0056] Figure 4 is a schematic diagram of the relationship between a maintenance trigger mechanism and a preset period provided by an embodiment of the present application, Figure 4 (a) is a schematic diagram of a batch replacement strategy, Figure 4 (b) is a schematic diagram of an age replacement strategy. DETAILED DESCRIPTION

[0057] The embodiments of the present application are described in detail below with reference to the accompanying drawings, but the present application can be implemented in various different ways as limited and covered by the claims.

[0058] Therefore, in order to solve the above problems, as shown in the present application, a method for determining the number of occurrences of a maintenance type of a hybrid converter station system is provided, comprising: Figure 1

[0059] Step S101: obtaining the initial operating life of each element in the system;

[0060] The hybrid converter station system of the present application mainly includes a modular multilevel converter and a line-commutated converter system, as shown in the present application, the main circuit of the modular multilevel converter is composed of six bridge arms, and the upper and lower bridge arms constitute a phase unit, each bridge arm is composed of a bridge arm reactor and k sub-modules in series, and the same number of half-bridge and full-bridge sub-modules are selected here. In order to improve the reliability of the MMC, each bridge arm is configured with n-k sub-modules as redundant modules (where n is the total number of bridge arm sub-modules). As shown in the present application, the main circuit of the line-commutated converter system is composed of two groups of 6-pulse converter bridges, and a 30° phase difference is realized through a star and a delta connected transformer, and each group of bridges contains 6 thyristor valve arms, and each valve arm is composed of a plurality of series-connected thyristors. Figure 2 Figure 3 As can be seen, the converter station includes a plurality of elements, and the present application is based on the relationship between the system operating life and the reliability, i.e. as shown in the present application, the calculation expression of the system operating life and the reliability of the converter station, which can also be understood as the life calculation expression of the converter station before maintenance, i.e.:

[0061] Figure 2 and Figure 3

[0062] (1)

[0063] wherein, t ​​​​To system operating life, R To reliability, Lambda To system failure rate.

[0064] To quantify the interaction between modules in the sampling process system, the failure rate should be predicted based on the reliability index of the mixed system, so the initial operating life of each element is determined by probability sampling (uniform distribution random number sampling):

[0065] (2)

[0066] Wherein, is the initial operating life of the element, is a random number subject to a standard uniform distribution, and EENS is the expected value of power shortage, T is the downtime when the device fails, P is the power shortage.

[0067] Step S102: determining an initial life matrix based on the initial operating life of each element;

[0068] The initial operating life of each element calculated in the foregoing step S101 can be understood as the random life of all elements in the converter station. Then, after classifying the initial operating life of each element according to a preset element type, the initial operating life is stored in blocks, thereby forming an initial life matrix. A m-1 The preset element type generally includes sub-modules, thyristors, and reactors.

[0069] Step S103: determining a residual life matrix based on the initial life matrix, the residual life matrix being a matrix of elements that have been detected and repaired but not replaced;

[0070] Due to the characteristics of "local life updating" of the system in engineering practice, that is, maintenance operation can only restore part of the performance of the element rather than completely reset the life. Then the current operating cycle working time is obtained T U_m-1 The residual life matrix is determined by combining the unit matrix of the same dimension as the correction matrix The residual life matrix is a matrix of elements that have been detected and repaired but not replaced in the current operating cycle:

[0071] (3)

[0072] Wherein, J is a unit matrix of the same dimension as the life matrix, and n is the dimension of the unit matrix.

[0073] It should be noted that the current operating cycle working time is the working time determined in the last operating cycle, and the specific calculation method will be described in detail later, which will not be mentioned here.

[0074] Step S104: determining the comprehensive remaining life of the converter system based on the remaining life matrix;

[0075] First, the remaining life matrix is divided into blocks according to the component category, and then the components in each block are sorted in ascending order of initial operating life to obtain the sorted block life matrix, and then the Figure 1 、 Figure 2 The redundant configuration of the components (sub-modules, thyristors) in the system topology is analyzed, and then the minimum redundancy constraint condition of each stable operation is used to determine the system operating state. The specific determination method will be described in detail later, which will not be described here.

[0076] Due to the different redundant designs of the converter station, the minimum redundancy constraint condition of the system operating state is different. Among them, the MMC relies on the redundant support of the sub-module to replace the faulty module online, while the LCC needs to rely on the system-level redundancy. When repairing, it usually needs to be partially or completely shut down, and cannot maintain operation like MMC by bypassing the faulty sub-module, so the comprehensive remaining life of the converter system can be determined according to the redundant configuration of the components in the system topology and the block life matrix as follows:

[0077] (4)

[0078] In the formula, is the comprehensive remaining life of the converter system of the MMC, is the comprehensive remaining life of the converter system of the LCC, is the sorted block life matrix; i 、 j s and p represent the series and parallel relationship of the system.

[0079] Step S105: determining the maintenance type in the current operating cycle of the system based on the comprehensive remaining life of the converter system;

[0080] Set the system maintenance period, then analyze and determine the relationship between the comprehensive remaining life of the converter system and the preset maintenance period, record the number of maintenance times after failure N f and the number of preventive maintenance times N p .

[0081] Figure 4 is the relationship between the two maintenance trigger mechanisms of preventive maintenance and failure maintenance and the preset period. Among them, the preventive maintenance strictly follows the preset period for maintenance, and the Tis fixed; while corrective maintenance depends on the real-time operation state assessment result, and is triggered when the equipment is confirmed to be in failure.

[0082] determines whether the comprehensive residual life of the converter system is less than the preset maintenance period, and when the residual life of the system is less than the preset maintenance period Tau s_m , it is determined that the maintenance type in the current operation period of the system is corrective maintenance, and when the determination result is no, it is determined that the maintenance type in the current operation period of the system is preventive maintenance, as shown in the following formula: T p

[0083] (5)

[0084] In the formula, f is the failure rate of the system, and T is the preset maintenance period. N f is corrective maintenance, N p is preventive maintenance.

[0085] Step S106: Based on the maintenance type in the current operation period of the system, the occurrence number of each maintenance type in the simulation iteration period of the system is determined.

[0086] After the maintenance type is determined, corresponding maintenance is performed according to the corresponding maintenance type, that is, when the maintenance type is failure type, corrective maintenance is performed, and then the working time length of the next operation period is determined according to the comprehensive residual life of the converter system and the preset maintenance period, as shown in the following formula:

[0087] (6)

[0088] During maintenance, due to the "local life updating" characteristics of the system, the system will only update the replaced part. In order to ensure that the system successfully completes the work within the working time length of the current operation period, the elements in the block life matrix that are less than the working time length of the current operation period are sampled and replaced, and the initial operation life of the replaced element is determined, that is:

[0089] (7)

[0090] In the formula, is the initial operation life of the replaced element, is the repair rate, and is a random number subject to a standard uniform distribution.

[0091] ​​​​After the element is replaced, the initial operation life corresponding to the replaced element is determined, and then the block life matrix after the sampling replacement is taken as the initial life matrix in the next operation period. Since the total system operation time includes multiple operation periods, the next step is to determine whether the current total system operation time reaches the first preset time length. If it does, the occurrence frequency of each maintenance type in the current total system operation time is determined, that is, the occurrence frequency of failure maintenance and preventive maintenance is determined. If the result of the determination does not reach the first preset time length, steps S103-S105 are executed to perform calculation and iteration in the next operation period.

[0092] In order to improve the prediction accuracy of the maintenance frequency model, multiple simulation simulations need to be performed. Therefore, after the occurrence frequency of failure maintenance and preventive maintenance is determined, it is necessary to determine whether the current simulation iteration frequency reaches the first preset frequency. If it does, the occurrence frequency of each maintenance type in the simulation iteration period is determined. If the first preset frequency is not reached, steps S101-S106 are repeatedly executed to perform the next simulation iteration calculation.

[0093] After determining that the type of failure is preventive maintenance, preventive maintenance can be performed. Since the processing procedures after maintenance and after failure maintenance are similar, only the subsequent processing flow is simply described, and the specific processing is not described in detail:

[0094] After performing preventive maintenance, the next operation period working time is determined according to the comprehensive residual life of the converter station system, and then the elements in the block life matrix that are less than the current operation period working time are sampled and replaced. The block life matrix after the sampling replacement is taken as the initial life matrix in the next operation period, and then it is determined whether the current total system operation time reaches the first preset time length. If it does, the occurrence frequency of each maintenance type in the current total system operation time is determined. If the first preset time length is not reached, steps S103-S105 are executed to perform calculation and iteration in the next operation period. When the first preset time length is reached, it is determined whether the current simulation iteration frequency reaches the first preset iteration frequency. If it does, the occurrence frequency of each maintenance type in the simulation iteration period is determined. If the first preset iteration frequency is not reached, steps S101-106 are executed to perform the next simulation iteration calculation.

[0095] It should be noted that the first preset time length and the first preset iteration frequency can be set as needed, and specific descriptions are not provided here.

[0096] After the first preset iteration frequency is reached, the occurrence frequency of each maintenance type in the system simulation iteration period is counted, and then the occurrence frequency of each maintenance type can be divided by the first preset iteration frequency to determine the average occurrence frequency of each maintenance type.

[0097] To sum up, the method of the present application introduces the reliability index of the converter station to predict the failure rate required in the sampling process, aiming at the influence of dynamic factors such as equipment aging and the mutual influence mechanism between modules on the operation and maintenance process, to ensure the credibility of the life prediction results; and the initial life of the running cycle is updated by locating and replacing the faulty components to reflect the "local life updating" characteristics in engineering practice, so as to realize accurate analysis and calculation of the number of various types of maintenance in the mixed converter station; at the same time, the prediction accuracy of the maintenance frequency model is improved through multiple simulation iterations, providing more accurate quantitative theoretical basis for formulating the optimal maintenance strategy under the premise of ensuring the reliable operation of the system.

[0098] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for determining the frequency of maintenance types in a hybrid converter station system, characterized in that, include: Step S101: Obtain the initial operating life of each component in the system; Step S102: Determine the initial lifetime matrix based on the initial operating lifetime of each component; Step S103: Based on the initial lifetime matrix, determine the remaining lifetime matrix, which is the matrix of components that have undergone maintenance and inspection and have not had faulty components replaced within the current operating cycle; Step S104: Determine the overall remaining lifetime of the converter system based on the remaining lifetime matrix; Step S105: Based on the overall remaining lifespan of the converter system, determine the maintenance type within the current operating cycle of the system; Step S106: Based on the maintenance types within the current operating cycle of the system, determine the number of occurrences of each maintenance type within the system simulation iteration cycle; The step of determining the initial lifetime matrix based on the initial operating lifetime of each component includes: The initial operating life of each component is categorized according to a preset component type, and then stored in blocks to form an initial life matrix; Determining the remaining lifetime matrix based on the initial lifetime matrix includes: Obtain the current running cycle duration and the identity matrix of the same dimension, wherein the current running cycle duration is the duration determined in the previous running cycle; The remaining lifetime matrix is ​​determined based on the initial lifetime matrix, the current operating cycle duration, and the identity matrix; The determination of the overall remaining lifetime of the converter system based on the remaining lifetime matrix includes: The remaining lifetime matrix is ​​divided into blocks according to component category, and the initial operating lifetime of the components in each block is sorted in ascending order to obtain the sorted block lifetime matrix. Obtain the redundancy configuration of components within the system topology; Based on the redundant configuration of components within the system topology and the segmented lifetime matrix, the overall remaining lifetime of the converter system is determined, specifically as follows: ； In the formula, For the overall remaining lifespan of the MMC converter system, For the LCC converter system's overall remaining lifetime, This is the block lifetime matrix after sorting. , These represent the number of bridge arms and components in the system, respectively; k represents the number of sub-modules; and s and p represent the series and parallel connections of the system.

2. The method according to claim 1, characterized in that, The initial operating life of each component in the system is determined as follows: The initial operating life of each component in the system is determined by using a probability sampling method.

3. The method according to claim 1, characterized in that, The determination of maintenance types within the current operating cycle of the converter system based on its overall remaining lifespan includes: Determine whether the overall remaining lifespan of the converter system is less than the preset maintenance cycle; If so, then the maintenance type within the current system operating cycle is determined to be fault maintenance; If not, then the maintenance type for the current system operating cycle is determined to be preventative maintenance.

4. The method according to claim 3, characterized in that, The determination of the occurrence frequency of each maintenance type within the simulation iteration cycle based on the maintenance types within the current operating cycle of the system includes: Perform fault repair; Based on the overall remaining lifespan of the converter system and the preset maintenance cycle, the working duration of the next operating cycle is determined. For components in the segmented lifetime matrix that are shorter than the current operating cycle duration, a sampling replacement is performed, and the segmented lifetime matrix after the sampling replacement is used as the initial lifetime matrix for the next operating cycle. Determine whether the current total system runtime has reached the first preset duration; If so, determine the number of times each type of maintenance occurs during the current total system uptime; Determine whether the current simulation iteration count has reached the first preset iteration count; If so, determine the number of times each maintenance type occurs within the simulation iteration cycle; If not, proceed to steps S101-S106 to perform the next simulation iteration calculation.

5. The method according to claim 4, characterized in that, If the result of determining whether the total running time of the current system has reached the first preset duration is negative, the subsequent steps are as follows: Perform steps S103-S105.

6. The method according to claim 3, characterized in that, The step of determining the occurrence frequency of each maintenance type within the simulation iteration cycle based on the maintenance types within the current operating cycle of the system also includes: Perform preventative maintenance; Based on the overall remaining lifespan of the converter system and the preset maintenance cycle, the working duration of the next operating cycle is determined. For components in the segmented lifetime matrix that are shorter than the current operating cycle duration, a sampling replacement is performed, and the segmented lifetime matrix after the sampling replacement is used as the initial lifetime matrix for the next operating cycle. Determine whether the current total system runtime has reached the first preset duration; If so, determine the number of times each type of maintenance occurs during the current total system uptime; Determine whether the current simulation iteration count has reached the first preset iteration count; If so, then determine the number of occurrences of each maintenance type within the simulation iteration cycle; If not, proceed to steps S101-S106 to perform the next simulation iteration calculation.

7. The method according to claim 6, characterized in that, If the result of determining whether the current total system running time has reached the first preset duration is negative, the subsequent steps are as follows: Perform steps S103-S105.

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