CN111384843A - MMC maintenance period determination method and system based on submodule state monitoring - Google Patents

MMC maintenance period determination method and system based on submodule state monitoring Download PDF

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CN111384843A
CN111384843A CN202010252854.4A CN202010252854A CN111384843A CN 111384843 A CN111384843 A CN 111384843A CN 202010252854 A CN202010252854 A CN 202010252854A CN 111384843 A CN111384843 A CN 111384843A
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袁敞
邱俊卿
戴笃猛
陈璐
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North China Electric Power University
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Abstract

The invention relates to a method and a system for determining an MMC maintenance period based on submodule state monitoring, which comprises the following steps: determining the fault rate and the number of first fault submodules of a first submodule according to a preset maintenance period, the number of submodules and the fault probability density of the preset submodules, and determining the fault probability density of a first correction submodule according to the data and the number of the first actual fault submodules; determining corresponding second data according to the method; determining the fault rate of the current submodule according to the reliability index; then determining the current maintenance period; maintaining the number of the current actual fault sub-modules according to the current maintenance period; then determining the number of the current pre-estimated fault sub-modules; finally, determining the fault probability density of the sub-module in the next period; and updating the fault probability density of the current sub-module to the fault probability density of the current sub-module, returning to re-determine the fault rate of the current sub-module, and adjusting the maintenance period of the next period. The method can solve the problem of unreliable maintenance period.

Description

MMC maintenance period determination method and system based on submodule state monitoring
Technical Field
The invention relates to the technical field of power conversion and transmission, in particular to a method and a system for determining an MMC maintenance period based on submodule state monitoring.
Background
In recent years, Modular Multilevel Converters (MMC) are widely used in a high-voltage direct-current transmission system, a main circuit of the MMC is composed of three phase units, namely a phase unit, a phase unit and a phase unit, each phase unit is composed of an upper bridge arm and a lower bridge arm, each bridge arm is formed by connecting a certain number of submodules in series, in addition, a plurality of redundant submodules are arranged in each bridge arm, and as shown in fig. 2, the MMC can normally operate only when the submodule normally working in each bridge arm is not lower than a certain numerical value. In order to ensure the operational reliability of the MMC and reduce the probability of failure, the MMC needs to be maintained. The existing maintenance method is mostly based on the constant sub-module fault rate, or the fault rate of the sub-module is corrected by introducing a voltage factor, and then the constant period T is used for correcting the fault ratePShutdown maintenance, namely, regular maintenance (PM) is performed on the MMC, and a maintenance cycle acquisition flow in the regular maintenance method is shown in fig. 3.
The maintenance period of the periodic maintenance method is estimated by the sub-module fault probability density lambda, which is determined by the fault probability density of each component constituting the sub-module. However, the actual operating conditions are complex, the sub-module failure probability density λ estimated by the failure probability density of each component is inaccurate, and the estimated maintenance period is unreasonable, so that the following technical problems exist:
when the fault probability density lambda of the sub-module is larger than the actual value, the estimated maintenance period is smaller, the maintenance cost is increased, and the economy of MMC maintenance is poor.
When the failure probability density λ of the sub-module is smaller than the actual value, the estimated maintenance period is larger, which may cause the operation of the MMC not to have sufficient reliability margin, and even may cause the shutdown due to the excessive number of the sub-modules without reaching the maintenance node.
Disclosure of Invention
The invention aims to provide a method and a system for determining an MMC maintenance period based on submodule state monitoring, which can solve the problem of unreliable maintenance period.
In order to achieve the purpose, the invention provides the following scheme:
a MMC maintenance cycle determination method based on sub-module state monitoring comprises the following steps:
acquiring a preset maintenance period, a preset sub-module fault probability density and the number of sub-modules;
determining the fault rate of the first sub-module according to the preset maintenance period and the fault probability density of the preset sub-module;
determining the number of first fault submodules according to the number of the submodules and the fault rate of the first submodule;
acquiring the number of first actual fault submodules;
determining the fault probability density of a first correction submodule according to the number of submodules, the preset maintenance period, the number of first fault submodules and the number of first actual fault submodules;
determining the fault rate of a second submodule according to the fault probability density of the first correction submodule and the preset maintenance period;
determining the number of second fault submodules according to the number of the submodules and the fault rate of the second submodule;
acquiring the number of second actual fault submodules;
determining a second correction submodule fault probability density according to the submodule quantity, a preset maintenance period, the second fault submodule quantity and the second actual fault submodule quantity, and taking the second correction submodule fault probability density as a current submodule fault probability density;
obtaining an MMC operation reliability index;
determining the fault rate of the current sub-module according to the reliability index;
determining a current maintenance period according to the fault rate of the current sub-module and the fault probability density of the current sub-module;
maintaining the MMC according to the current maintenance period to obtain the number of current actual fault sub-modules;
determining the number of the current pre-estimated fault sub-modules according to the number of the sub-modules and the fault rate of the current sub-module;
determining the failure probability density of the sub-module in the next period according to the number of the current pre-estimated failure sub-modules, the number of the current failure sub-modules, the number of the sub-modules and the current maintenance period;
and updating the fault probability density of the current sub-module to the fault probability density of the current sub-module, and returning to the step of determining the fault rate of the current sub-module according to the reliability index.
Optionally, the determining the failure rate of the first sub-module according to the preset maintenance period and the preset sub-module failure probability density specifically includes:
according to the formula q1＝X1×λ1Determining a failure rate of the first sub-module; wherein q is1Is the failure rate of the first submodule, X1For a predetermined maintenance period, λ1And presetting sub-module fault probability density.
Optionally, the determining the number of the first sub-modules with faults according to the number of the sub-modules and the fault rate of the first sub-module specifically includes:
according to the formula n1＝(Y+Z)×q1Determining the number of first fault submodules; wherein q is1Is the failure rate of the first submodule, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
Optionally, the determining the failure probability density of the first revision sub-module according to the number of the sub-modules, the preset maintenance period, the number of the first failure sub-modules, and the number of the first actual failure sub-modules specifically includes:
according to the formula
Figure BDA0002436111990000031
Determining the fault probability density of a first correction submodule; wherein, X1For a predetermined maintenance period, m1For the first actual number of fault submodules, λ2For the first correction submodule failure probability density, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
Optionally, the determining the failure rate of the current sub-module according to the reliability index specifically includes:
according to the formula
Figure BDA0002436111990000032
Determining the fault rate of the current sub-module; wherein q is3Is the failure rate of the current sub-module, a is the reliability index, Y is the number of sub-modules in normal operation, Z is the number of sub-modules in redundancy,
Figure BDA0002436111990000033
the probability of a non-faulty sub-module,
Figure BDA0002436111990000034
the probability of i faulty sub-modules, i 0,1,2.. Z,
Figure BDA0002436111990000035
the probability of Z failed sub-modules.
Optionally, the determining a current maintenance cycle according to the fault rate of the current sub-module and the fault probability density of the current sub-module specifically includes:
according to the formula
Figure BDA0002436111990000041
Determining a current maintenance period; wherein q is3For the failure rate of the current submodule, λ3Current sub-module failure probability density, X3The current maintenance cycle.
An MMC maintenance cycle determination system based on sub-module status monitoring, the MMC maintenance cycle determination system comprising:
the data acquisition module is used for acquiring a preset maintenance period, a preset sub-module fault probability density and the number of sub-modules;
the fault rate determining module of the first sub-module is used for determining the fault rate of the first sub-module according to the preset maintenance period and the preset sub-module fault probability density;
the first fault submodule quantity determining module is used for determining the quantity of first fault submodules according to the quantity of the submodules and the fault rate of the first submodule;
the first actual fault submodule quantity obtaining module is used for obtaining the first actual fault submodule quantity;
the first correction submodule fault probability density determining module is used for determining the first correction submodule fault probability density according to the submodule quantity, the preset maintenance period, the first fault submodule quantity and the first actual fault submodule quantity;
the fault rate determining module of the second submodule is used for determining the fault rate of the second submodule according to the fault probability density of the first correction submodule and the preset maintenance period;
the second fault submodule quantity determining module is used for determining the quantity of second fault submodules according to the quantity of the submodules and the fault rate of the second submodules;
the second actual fault submodule quantity obtaining module is used for obtaining the second actual fault submodule quantity;
a current sub-module fault probability density determining module, configured to determine a second modified sub-module fault probability density according to the number of sub-modules, a preset maintenance period, the number of second fault sub-modules, and the number of second actual fault sub-modules, and use the second modified sub-module fault probability density as a current sub-module fault probability density;
the reliability index acquisition module is used for acquiring the MMC operation reliability index;
the fault rate determining module of the current sub-module is used for determining the fault rate of the current sub-module according to the reliability index;
a current maintenance period determining module, configured to determine a current maintenance period according to the fault rate of the current sub-module and the fault probability density of the current sub-module;
a current actual fault submodule quantity obtaining module, configured to maintain the MMC according to the current maintenance period, and obtain a current actual fault submodule quantity;
the current estimated fault submodule quantity determining module is used for determining the current estimated fault submodule quantity according to the submodule quantity and the fault rate of the current submodule;
a next cycle sub-module fault probability density determining module, configured to determine a next cycle sub-module fault probability density according to the current estimated number of fault sub-modules, the current number of fault sub-modules, the number of sub-modules, and the current maintenance cycle;
and the updating module is used for updating the fault probability density of the current sub-module into the fault probability density of the current sub-module and returning the fault probability density of the current sub-module to the fault rate determining module of the current sub-module.
Optionally, the failure rate determining module of the first sub-module specifically includes:
a failure rate determination unit of a first submodule for determining a failure rate according to the formula q1＝X1×λ1Determining a failure rate of the first sub-module; wherein q is1Is the failure rate of the first submodule, X1For a predetermined maintenance period, λ1And presetting sub-module fault probability density.
Optionally, the first fault sub-module number determining module specifically includes:
a first failure submodule quantity determining unit for determining the quantity of the failure submodules according to the formula n1＝(Y+Z)×q1Determining the number of first fault submodules; wherein q is1Is the failure rate of the first submodule, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
Optionally, the determining module for the probability density of failure of the first sub-module specifically includes:
a first correction submodule fault probability density determination unit for determining the first correction submodule fault probability density according to a formula
Figure BDA0002436111990000051
Determining the fault probability density of a first correction submodule; wherein, X1For a predetermined maintenance period, m1For the first actual number of fault submodules, λ2For the first correction submodule failure probability density, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention relates to a method and a system for determining an MMC maintenance period based on submodule state monitoring, which comprises the following steps: determining the fault rate and the number of first fault submodules of a first submodule according to a preset maintenance period, the number of submodules and the fault probability density of the preset submodules, and determining the fault probability density of a first correction submodule according to the data and the number of the first actual fault submodules; determining corresponding second data according to the method; determining the fault rate of the current submodule according to the reliability index; then determining the current maintenance period; maintaining the number of the current actual fault sub-modules according to the current maintenance period; then determining the number of the current pre-estimated fault sub-modules; finally, determining the fault probability density of the sub-module in the next period; and updating the fault probability density of the current sub-module to the fault probability density of the current sub-module, returning to re-determine the fault rate of the current sub-module, and adjusting the maintenance period of the next period. The method can solve the problem of unreliable maintenance period, and further coordinate the relationship between the operation reliability and the maintenance economy of the MMC, so that the maintenance cost is reduced on the premise of ensuring enough operation reliability.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a flowchart of an MMC maintenance cycle determining method based on sub-module status monitoring according to an embodiment of the present invention;
FIG. 2 is a diagram of an MMC topology;
FIG. 3 is a flow of acquisition of a maintenance cycle;
FIG. 4 is a graph of sub-module failure probability density provided by an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an MMC maintenance cycle determining system based on sub-module status monitoring according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a method and a system for determining an MMC maintenance period based on submodule state monitoring, which can solve the problem of unreliable maintenance period.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a flowchart of an MMC maintenance cycle determining method based on sub-module status monitoring according to an embodiment of the present invention, and as shown in fig. 1, the MMC maintenance cycle determining method according to the present invention includes:
s101, acquiring a preset maintenance period, a preset sub-module fault probability density and the number of sub-modules.
In the actual engineering, the index for measuring the operation reliability of the MMC is that the shutdown probability of the MMC system in a maintenance period cannot exceed a fixed value a, a fault probability density curve of the submodule is shown in figure 4 and comprises two stages which are respectively a normal service period and a fault rate sharply increased period.
Specifically, the probability density of the failure of the preset sub-module in the maintenance period 1 is λ1The number of years of the preset maintenance period is X1In the year, the number of the submodules is (Y + Z), and the MMC operation reliability index is a.
S102, determining the fault rate of the first sub-module according to the preset maintenance period and the preset sub-module fault probability density, and specifically comprising the following steps:
and (3) a fault rate calculation process of the sub-modules in the maintenance period 1: according to the formula q1＝X1×λ1Determining a failure rate of the first sub-module; wherein q is1Is the failure rate of the first submodule, X1For a predetermined maintenance period, λ1And presetting sub-module fault probability density.
And q is1Satisfy MMC operational reliability, i.e.
Figure BDA0002436111990000071
S103, determining the number of first fault sub-modules according to the number of sub-modules and the fault rate of the first sub-module, and specifically comprising the following steps:
from inaccurate lambda1Number of failure submodules estimated, estimated in maintenance cycle 1The number of the fault sub-modules, namely the number of the first fault sub-modules, is calculated: according to the formula n1＝(Y+Z)×q1Determining the number of first fault submodules; wherein q is1Is the failure rate of the first submodule, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundancy submodules is (Z).
And S104, acquiring the number of the first actual fault submodules.
Maintaining the MMC, and counting to obtain the number of actual fault sub-modules in the maintenance period 1, namely the number m of first actual fault sub-modules1And replacing the failed sub-module.
S105, determining the fault probability density of a first correction submodule according to the number of submodules, the preset maintenance period, the number of first fault submodules and the number of first actual fault submodules, and specifically comprising the following steps:
by the number n of first faulty submodules in maintenance cycle 11And a first actual number m of faulty submodules1Correcting lambda1The method is as follows and the next maintenance cycle, maintenance cycle 2, is entered.
According to the formula
Figure BDA0002436111990000081
Determining the fault probability density of a first correction submodule; wherein, X1For a predetermined maintenance period, m1For the first actual number of fault submodules, λ2For the first correction submodule failure probability density, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
Sub-module failure probability density in maintenance cycle 2 is λ2The number of years of the maintenance period is X1And (5) year.
And S106, determining the fault rate of the second submodule according to the fault probability density of the first correction submodule and the preset maintenance period.
Failure rate of the submodule in maintenance cycle 2, i.e. failure rate of the second submodule, q2＝X1×λ2Wherein q is2Is the failure rate of the second submodule, lambda2The first modified submodule fault probability density.
And q is2Satisfy MMC operational reliability, i.e.
Figure BDA0002436111990000082
And S107, determining the number of second fault sub-modules according to the number of sub-modules and the fault rate of the second sub-modules.
From inaccurate lambda2And (3) estimating the number of the fault sub-modules, wherein the estimated number of the fault sub-modules in the maintenance period 2 is the calculation process of the number of the second fault sub-modules: according to the formula n2＝(Y+Z)×q2Determining the number of second fault submodules; wherein q is2Is the failure rate of the second submodule, n2And the number of the second fault submodules is (Y + Z), the number of the submodules is Y, the number of the normal working submodules is Y, and the number of the redundant submodules is Z.
And S108, acquiring the number of the second actual fault submodules.
Maintaining the MMC, and counting to obtain the number of actual fault sub-modules in the maintenance period 2, namely the number m of second actual fault sub-modules2And replacing the failed sub-module.
S109, determining the fault probability density of a second correction submodule according to the number of the submodules, the preset maintenance period, the number of the second fault submodules and the number of the second actual fault submodules, and taking the fault probability density of the second correction submodule as the fault probability density of the current submodule.
By the number n of second faulty submodules in maintenance cycle 22And a second number m of actual fault submodules2Correcting lambda2To obtain lambda3The method is as follows and the next maintenance cycle, maintenance cycle 3, is entered.
According to the formula
Figure BDA0002436111990000091
Determining a second modifier submoduleA failure probability density; wherein, X1For a predetermined maintenance period, m2For the second actual number of fault submodules, λ3Is the current sub-module failure probability density.
And S110, obtaining the MMC operation reliability index.
S111, determining the fault rate of the current sub-module according to the reliability index, specifically comprising:
lambda corrected by actual values of maintenance cycle 1 and maintenance cycle 23Adjusting maintenance period according to formula
Figure BDA0002436111990000092
Determining the fault rate of the current sub-module; wherein q is3Is the failure rate of the current sub-module, a is the reliability index, Y is the number of sub-modules in normal operation, Z is the number of sub-modules in redundancy,
Figure BDA0002436111990000093
the probability of a non-faulty sub-module,
Figure BDA0002436111990000094
the probability of i faulty sub-modules, i 0,1,2.. Z,
Figure BDA0002436111990000095
the probability of Z failed sub-modules.
Solving the fault rate q of the current sub-module according to the reliability index formula3And according to q3Determining a suitable maintenance period X3。
And S112, determining the current maintenance cycle according to the fault rate of the current sub-module and the fault probability density of the current sub-module.
According to the formula
Figure BDA0002436111990000096
Determining a current maintenance period; wherein q is3For the failure rate of the current submodule, λ3Current sub-module failure probability density, X3The time of the current maintenance cycle, maintenance cycle 3, is adjusted toMore reasonable X3
S113, maintaining the MMC according to the current maintenance period, and obtaining the number of the current actual fault submodules.
According to a more reasonable maintenance period X3Maintaining the MMC, and counting to obtain the number of actual fault sub-modules in a maintenance period 3, namely the number m of the current actual fault sub-modules3And updating the failed sub-module to a new sub-module, and entering the next maintenance cycle, namely the maintenance cycle 4.
S114, determining the number of the current estimated fault sub-modules according to the number of the sub-modules and the fault rate of the current sub-module, and specifically comprising the following steps:
according to corrected lambda3The number of the fault sub-modules is estimated, the number of the estimated fault sub-modules in the maintenance period 4, namely the current estimated number of the fault sub-modules, is calculated: according to the formula n3＝(Y+Z)×q3Determining the number of current pre-estimated fault submodules; wherein q is3For the failure rate of the current submodule, n3For the number of the current predicted fault sub-modules, (Y + Z) is the number of sub-modules, Y is the number of normal working sub-modules, and Z is the number of redundant sub-modules.
And S115, determining the sub-module fault probability density of the next period according to the current estimated fault sub-module number, the current fault sub-module number, the sub-module number and the current maintenance period.
According to the formula
Figure BDA0002436111990000101
Determining the fault probability density of the sub-module in the next period; wherein, X3For the current maintenance cycle, n3For the current estimated number of fault submodules, m3The current actual number of fault submodules.
And S116, updating the fault probability density of the current sub-module to the fault probability density of the current sub-module, returning to S111, and calculating the fault rate of the sub-module in the maintenance period 4.
In particular, according to the formula
Figure BDA0002436111990000102
Determining the failure rate of the sub-modules in the maintenance period 4; wherein q is4To maintain the failure rate of the sub-modules in cycle 4, a is the reliability index.
According to the formula
Figure BDA0002436111990000103
And determining a maintenance period of the maintenance period 4, wherein the maintenance period 4 can be regarded as the current maintenance period, maintaining the MMC again according to the current maintenance period, and then calculating the sub-module fault probability density of the next period, namely the sub-module fault probability density of the maintenance period 5, by adopting the same method.
In the invention, the preset data in the maintenance period 1 and the maintenance period 2 are utilized to correct the lambda in the maintenance period 33According to corrected lambda3Calculating X3Because of the use of modified lambda3X thus calculated3More reasonable according to X3Maintaining the MMC to replace the fault submodule and then according to reasonable X3Readjusting λ of maintenance period 44Further obtain X4According to X4Maintaining MMC to replace fault submodule according to X4Readjusting λ of maintenance period 55Further obtain X5The maintenance period 3 is followed by adjusting the maintenance period of the next maintenance period according to the current period data, thereby adjusting the time of each maintenance period in turn.
By way of example, the following are illustrated:
the sub-module fault probability density lambda is inaccurate, two conditions are listed, namely how to adjust the maintenance period when the lambda is larger and the lambda is smaller, and the operation reliability and the maintenance economy are improved, wherein the sub-module number (Y + Z) is 432, the normal working sub-module number Y is 400, and the redundant sub-module number Z is 32.
(1) Case of large lambda
Maintenance cycle 1:
the fault probability density of a preset submodule is taken as lambda10.015, preset maintenance period X1After 3 years, the index for ensuring the operation reliability of the MMC is a ═ 4 ‰, thenIn this maintenance cycle, the failure probability q of the submodule1＝X1×λ 13 × 0.015 0.045, and this probability satisfies
Figure BDA0002436111990000111
The number of the predicted faulty submodules in the maintenance cycle 1 is the number of the first faulty submodules, n1＝(Y+Z)×q1432 × 0.045 ≈ 19.44 ≈ 20.
The number of actual fault submodules obtained by statistics in the maintenance period 1 is the number m of first actual fault submodules 110, using maintenance period 1 to estimate the number of fault sub-modules n1And the actual value m1Correcting lambda1And enters the next maintenance cycle.
Figure BDA0002436111990000112
Maintenance period 2:
λ2if the maintenance period is still 3 years, the failure rate q of the submodule in the maintenance period is 0.01162＝X1×λ 23 × 0.0116 0.0347, and this failure rate satisfies MMC operational reliability
Figure RE-GDA0002495597760000113
The number of the predicted fault submodules in the maintenance period 2, namely the number n of the second fault submodules2＝(Y+Z)×q2432 × 0.0347 14.9904 ≈ 15, and the number m of actual faulty submodules statistically obtained in maintenance cycle 22Using the estimated value n of the number of sub-modules with the number of faults in maintenance period 2 as 122And the actual value m2Correcting lambda2And enters the next maintenance cycle.
Figure BDA0002436111990000114
Maintenance period 3:
the fault probability density lambda of the submodule is closer to an actual value after the actual data of two maintenance periods are corrected, and the corrected lambda is utilized3Adjusting maintenance period according to the reliability index formula
Figure BDA0002436111990000115
Calculating the suitable sub-module failure rate q3The time for maintenance cycle 3 was determined at 0.046
Figure BDA0002436111990000121
About 4 years.
The maintenance period estimated by the larger fault probability density is 3 years, the maintenance period is smaller, the economy of MMC maintenance is poor, after the actual data of the two maintenance periods are corrected, lambda is closer to an actual value, the maintenance period is adjusted to be 4 years by using the corrected lambda, the maintenance frequency within a certain time is reduced, the economy of maintenance is improved, the MMC is maintained according to the maintenance period of the maintenance period 3, the fault probability density of the maintenance period 4 is adjusted according to the data of the maintenance period 3 and the data obtained by maintenance, the maintenance period is determined, and the maintenance period 5, the maintenance period 6 and the like are solved by analogy.
(2) Case of small lambda
Maintenance cycle 1:
the fault probability density of a preset submodule is taken as lambda10.0125, preset maintenance period is X1In 3 years, the index for ensuring the operation reliability of the MMC is a ═ 4 ‰, and the fault probability q of the submodule in the maintenance period is determined1＝X1×λ 13 × 0.0125.0125 0.0375, and this probability satisfies
Figure BDA0002436111990000122
The number of the predicted faulty submodules in the maintenance cycle 1 is the number of the first faulty submodules, n1＝(Y+Z)×q1432 × 0.0375-17.
The number of actual fault submodules obtained by statistics in the maintenance period 1 is the number m of first actual fault submodules120, using the estimated value n of the number of fault sub-modules in maintenance period 11And the actual value m1Correcting lambda1And enters the next maintenance cycle.
Figure BDA0002436111990000123
Maintenance period 2:
λ2if the maintenance period is 0.0147 and the maintenance period is still 3 years, the failure rate q of the submodule is measured in the maintenance period2＝X1×λ 23 × 0.0147 0.0439 and this failure rate satisfies MMC operational reliability
Figure BDA0002436111990000124
The number of the predicted fault submodules in the maintenance period 2, namely the number n of the second fault submodules2＝432×q2432 × 0.0439, 19, the number m of the actual faulty submodules counted in the maintenance cycle 22Using the estimated value n of the number of faulty submodules in maintenance cycle 2, which is 222And the actual value m2Correcting lambda2And enters the next maintenance cycle.
Figure BDA0002436111990000131
Maintenance period 3:
the fault probability density lambda of the submodule is closer to an actual value after the actual data of two maintenance periods are corrected, and the corrected lambda is utilized3Adjusting maintenance period according to the reliability index formula
Figure BDA0002436111990000132
Calculating the suitable sub-module failure rate q3The time for maintenance cycle 3 was determined at 0.046
Figure BDA0002436111990000133
About 2.5 years.
The estimated maintenance period of the smaller fault probability density is 3 years, the maintenance period is larger, the MMC does not have enough reliability margin in operation, after the actual data of the two maintenance periods are corrected, lambda is closer to an actual value, the maintenance period is adjusted to be 2.5 years by using the corrected lambda, the reliability margin in operation of the MMC is increased, the MMC is maintained according to the maintenance period of the maintenance period 3, the fault probability density of the maintenance period 4 is adjusted according to the data of the maintenance period 3 and the data obtained in maintenance, the maintenance period is determined, and the maintenance period 5, the maintenance period 6 and the like are solved in the same way.
The present invention also provides an MMC maintenance cycle determining system based on sub-module status monitoring, as shown in fig. 5, the MMC maintenance cycle determining system includes:
and the data acquisition module 1 is used for acquiring a preset maintenance period, a preset sub-module fault probability density and the number of sub-modules.
And the failure rate determining module 2 of the first sub-module is used for determining the failure rate of the first sub-module according to the preset maintenance period and the preset sub-module failure probability density.
And the first sub-module number of faults determining module 3 is used for determining the number of the first sub-modules of faults according to the number of the sub-modules and the fault rate of the first sub-module.
And a first actual failure submodule quantity obtaining module 4, configured to obtain a first actual failure submodule quantity.
And the first correction submodule fault probability density determining module 5 is used for determining the first correction submodule fault probability density according to the submodule quantity, the preset maintenance period, the first fault submodule quantity and the first actual fault submodule quantity.
And the failure rate determining module 6 of the second submodule is used for determining the failure rate of the second submodule according to the failure probability density of the first correction submodule and the preset maintenance period.
And the second fault submodule quantity determining module 7 is used for determining the quantity of the second fault submodules according to the quantity of the submodules and the fault rate of the second submodule.
And a second actual failure submodule quantity obtaining module 8, configured to obtain a second actual failure submodule quantity.
And a current sub-module fault probability density determining module 9, configured to determine a second modified sub-module fault probability density according to the number of sub-modules, the preset maintenance period, the number of second fault sub-modules, and the number of second actual fault sub-modules, and use the second modified sub-module fault probability density as the current sub-module fault probability density.
And the reliability index obtaining module 10 is used for obtaining the reliability index of the MMC operation.
And the fault rate determining module 11 of the current sub-module is used for determining the fault rate of the current sub-module according to the reliability index.
And a current maintenance period determining module 12, configured to determine a current maintenance period according to the failure rate of the current sub-module and the failure probability density of the current sub-module.
And a current actual fault sub-module quantity obtaining module 13, configured to maintain the MMC according to the current maintenance period, and obtain the current actual fault sub-module quantity.
And a current estimated fault submodule quantity determining module 14, configured to determine the current estimated fault submodule quantity according to the submodule quantity and the fault rate of the current submodule.
And a next cycle sub-module fault probability density determining module 15, configured to determine the next cycle sub-module fault probability density according to the current estimated number of fault sub-modules, the current number of fault sub-modules, the number of sub-modules, and the current maintenance cycle.
And the updating module 16 is configured to update the current sub-module failure probability density to the current sub-module failure probability density, and return to the failure rate determining module 11 of the current sub-module.
Preferably, the failure rate determining module 2 of the first sub-module specifically includes:
a failure rate determination unit of a first submodule for determining a failure rate according to the formula q1＝X1×λ1Determining a failure rate of the first sub-module; wherein q is1Is the failure rate of the first submodule, X1For a predetermined maintenance period, λ1And presetting sub-module fault probability density.
Preferably, the first fault submodule quantity determining module 3 specifically includes:
a first failure submodule quantity determining unit for determining the quantity of the failure submodules according to the formula n1＝(Y+Z)×q1Determining the number of first fault submodules; wherein q is1Is the failure rate of the first submodule, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
Preferably, the first correction submodule fault probability density determination module specifically includes:
a first correction submodule fault probability density determination unit for determining the first correction submodule fault probability density according to a formula
Figure BDA0002436111990000151
Determining the fault probability density of a first correction submodule; wherein, X1For a predetermined maintenance period, m1For the first actual number of fault submodules, λ2For the first correction submodule failure probability density, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
In the invention, the sub-module fault probability density lambda is corrected by comparing the number of the estimated fault sub-modules in each maintenance period with the number of the fault sub-modules appearing in actual operation, the lambda is closer to an actual value after the correction of actual data in a historical maintenance period, and the maintenance period is adjusted by using the corrected lambda, so that the maintenance period is more reasonable.
According to the method, the estimated maintenance period is smaller when the fault probability density lambda of the sub-module is larger, the economy of MMC maintenance is poorer, and after the correction of the method, more accurate lambda can be obtained, so that a reasonable maintenance period is obtained, and the economy of maintenance is improved on the premise of not losing the running reliability of the MMC. When the fault probability density lambda of the sub-module is smaller, the estimated maintenance period is larger, the MMC does not have enough reliability margin during operation, after the correction of the method, the maintenance period can be reduced to a reasonable value, so that the reliability margin during operation of the MMC is increased.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (10)

1. The MMC maintenance cycle determination method based on submodule state monitoring is characterized by comprising the following steps of:
acquiring a preset maintenance period, a preset sub-module fault probability density and the number of sub-modules;
determining the fault rate of the first sub-module according to the preset maintenance period and the fault probability density of the preset sub-module;
determining the number of first fault submodules according to the number of the submodules and the fault rate of the first submodule;
acquiring the number of first actual fault submodules;
determining the fault probability density of a first correction submodule according to the number of submodules, the preset maintenance period, the number of first fault submodules and the number of first actual fault submodules;
determining the fault rate of a second submodule according to the fault probability density of the first correction submodule and the preset maintenance period;
determining the number of second fault submodules according to the number of the submodules and the fault rate of the second submodule;
acquiring the number of second actual fault submodules;
determining a second correction submodule fault probability density according to the submodule quantity, a preset maintenance period, the second fault submodule quantity and the second actual fault submodule quantity, and taking the second correction submodule fault probability density as a current submodule fault probability density;
obtaining an MMC operation reliability index;
determining the fault rate of the current sub-module according to the reliability index;
determining a current maintenance period according to the fault rate of the current sub-module and the fault probability density of the current sub-module;
maintaining the MMC according to the current maintenance period to obtain the number of current actual fault sub-modules;
determining the number of the current pre-estimated fault sub-modules according to the number of the sub-modules and the fault rate of the current sub-module;
determining the failure probability density of the sub-module in the next period according to the number of the current pre-estimated failure sub-modules, the number of the current failure sub-modules, the number of the sub-modules and the current maintenance period;
and updating the fault probability density of the current sub-module to the fault probability density of the current sub-module, and returning to the step of determining the fault rate of the current sub-module according to the reliability index.
2. The method for determining the MMC maintenance cycle based on sub-module status monitoring according to claim 1, wherein the determining the failure rate of the first sub-module according to the preset maintenance cycle and the preset sub-module failure probability density specifically includes:
according to the formula q1＝X1×λ1Determining a failure rate of the first sub-module; wherein q is1Is the failure rate of the first submodule, X1For a predetermined maintenance period, λ1And presetting sub-module fault probability density.
3. The submodule state monitoring-based MMC maintenance cycle determination method of claim 1, wherein said determining a first number of faulty submodules according to said number of submodules and a fault rate of said first submodule specifically comprises:
according to the formula n1＝(Y+Z)×q1Determining the number of first fault submodules; wherein q is1Is the failure rate of the first submodule, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
4. The submodule state monitoring-based MMC maintenance cycle determination method of claim 1, wherein said determining a first modified submodule failure probability density according to said submodule number, said preset maintenance cycle, said first failure submodule number and said first actual failure submodule number specifically comprises:
according to the formula
Figure FDA0002436111980000021
Determining the fault probability density of a first correction submodule; wherein, X1For a predetermined maintenance period, m1For the first actual number of fault submodules, λ2For the first correction submodule failure probability density, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
5. The method for determining the MMC maintenance cycle based on sub-module status monitoring as claimed in claim 1, wherein the determining the failure rate of the current sub-module according to the reliability index specifically comprises:
according to the formula
Figure FDA0002436111980000022
Determining the fault rate of the current sub-module; wherein q is3Is the failure rate of the current sub-module, a is the reliability index, Y is the number of sub-modules in normal operation, Z is the number of sub-modules in redundancy,
Figure FDA0002436111980000023
the probability of a non-faulty sub-module,
Figure FDA0002436111980000031
the probability of i faulty sub-modules, i 0,1,2.. Z,
Figure FDA0002436111980000032
the probability of Z failed sub-modules.
6. The method for determining the MMC maintenance cycle based on sub-module status monitoring according to claim 1, wherein the determining the current maintenance cycle according to the failure rate of the current sub-module and the failure probability density of the current sub-module specifically includes:
according to the formula
Figure FDA0002436111980000033
Determining a current maintenance period; wherein q is3For the failure rate of the current submodule, λ3Current sub-module failure probability density, X3The current maintenance cycle.
7. An MMC maintenance cycle determination system based on submodule status monitoring, the MMC maintenance cycle determination system comprising:
the data acquisition module is used for acquiring a preset maintenance period, a preset sub-module fault probability density and the number of sub-modules;
the fault rate determining module of the first sub-module is used for determining the fault rate of the first sub-module according to the preset maintenance period and the preset sub-module fault probability density;
the first fault submodule quantity determining module is used for determining the quantity of first fault submodules according to the quantity of the submodules and the fault rate of the first submodule;
the first actual fault submodule quantity obtaining module is used for obtaining the first actual fault submodule quantity;
the first correction submodule fault probability density determining module is used for determining the first correction submodule fault probability density according to the submodule quantity, the preset maintenance period, the first fault submodule quantity and the first actual fault submodule quantity;
the fault rate determining module of the second submodule is used for determining the fault rate of the second submodule according to the fault probability density of the first correction submodule and the preset maintenance period;
the second fault submodule quantity determining module is used for determining the quantity of second fault submodules according to the quantity of the submodules and the fault rate of the second submodules;
the second actual fault submodule quantity obtaining module is used for obtaining the second actual fault submodule quantity;
a current sub-module fault probability density determining module, configured to determine a second modified sub-module fault probability density according to the number of sub-modules, a preset maintenance period, the number of second fault sub-modules, and the number of second actual fault sub-modules, and use the second modified sub-module fault probability density as a current sub-module fault probability density;
the reliability index acquisition module is used for acquiring the MMC operation reliability index;
the fault rate determining module of the current sub-module is used for determining the fault rate of the current sub-module according to the reliability index;
a current maintenance period determining module, configured to determine a current maintenance period according to the fault rate of the current sub-module and the fault probability density of the current sub-module;
a current actual fault submodule quantity obtaining module, configured to maintain the MMC according to the current maintenance period, and obtain a current actual fault submodule quantity;
the current estimated fault submodule quantity determining module is used for determining the current estimated fault submodule quantity according to the submodule quantity and the fault rate of the current submodule;
a next cycle sub-module fault probability density determining module, configured to determine a next cycle sub-module fault probability density according to the current estimated number of fault sub-modules, the current number of fault sub-modules, the number of sub-modules, and the current maintenance cycle;
and the updating module is used for updating the fault probability density of the current sub-module into the fault probability density of the current sub-module and returning the fault probability density of the current sub-module to the fault rate determining module of the current sub-module.
8. The submodule state monitoring-based MMC maintenance cycle determination system of claim 7, wherein the failure rate determination module of the first submodule specifically comprises:
a failure rate determination unit of a first submodule for determining a failure rate according to the formula q1＝X1×λ1Determining a failure rate of the first sub-module; wherein q is1Is the failure rate of the first submodule, X1For a predetermined maintenance period, λ1And presetting sub-module fault probability density.
9. The submodule state monitoring-based MMC maintenance cycle determination system of claim 7, wherein, the module for determining the number of the first sub-module with fault specifically comprises:
a first failure submodule quantity determining unit for determining the quantity of the failure submodules according to the formula n1＝(Y+Z)×q1Determining the number of first fault submodules; wherein q is1Is the failure rate of the first submodule, n1The number of the first fault submodules, (Y + Z) is the number of submodules, Y is the number of normal working submodules, and Z is the redundancy submodulesThe number of blocks.
10. The submodule state monitoring-based MMC maintenance cycle determination system of claim 7, wherein the first revision submodule failure probability density determination module specifically comprises:
a first correction submodule fault probability density determination unit for determining the first correction submodule fault probability density according to a formula
Figure FDA0002436111980000041
Determining the fault probability density of a first correction submodule; wherein, X1For a predetermined maintenance period, m1For the first actual number of fault submodules, λ2For the first correction submodule failure probability density, n1The number of the first fault submodules is (Y + Z), the number of the normal working submodules is (Y), and the number of the redundant submodules is (Z).
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