CN111880090A - Distribution layered online fault detection method for million-kilowatt ultra-supercritical unit - Google Patents
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Abstract
The invention discloses a distribution layering type online fault detection method for a million kilowatt ultra-supercritical unit. Aiming at the problems of numerous process variables and complex changing conditions of a million-kilowatt ultra-supercritical unit, comprehensively considering the correlation among the variables and the distribution condition of the variables in the sample direction, blocking the variables by using a multi-layer information theory decomposition method, and establishing a multi-layer distributed monitoring algorithm facing the million-kilowatt ultra-supercritical unit based on a blocking result and combining a Gaussian mixture model method and a Bayesian theory. The method fully explores relevant information among process variables, is beneficial to understanding the complex process characteristics of the million kilowatt ultra-supercritical unit, can effectively excavate local information of the process, can analyze the relevant relation among different variable subblocks, and greatly improves the fault detection performance of the million kilowatt ultra-supercritical unit in the complex process, thereby ensuring the safe and reliable operation of a large coal-fired generator set.
Description
Technical Field
The invention belongs to the field of thermal power process fault detection, and particularly relates to a distributed layered online process monitoring method for a million-kilowatt ultra-supercritical unit with a plurality of heavy-faced variables and frequent fluctuation of working conditions.
Background
The power industry is an important basic industry of national economy and is a key project in the national economic development strategy. With the rapid development of economy, the demand for electricity is also rapidly increasing. Coal resources are the main energy in China, so that the energy structure mainly based on coal is difficult to change fundamentally in a long period in the future. As a main power source in China, the installed capacity of coal-fired power generation is always over 70 percent. According to statistics, under the promotion of vigorous electricity demand, the total electricity consumption of the whole society in 1-8 months in 2018 is up to 45296 hundred million kilowatt hours, and the electricity consumption is increased by 9.0 percent on a same scale. Wherein, the accumulated power generation amount of the thermal power is 33103 hundred million kilowatts, which accounts for 73.1 percent of the total power generation amount of the whole country and is increased by 7.2 percent on a par. In recent years, in order to realize sustainable development of electric power, structural adjustment is actively carried out in the thermal power generation industry, the upper large pressure is small, a high-energy-consumption small thermal power generating unit is replaced by a high-capacity and low-energy-consumption supercritical (supercritical) unit, and an electric power energy structure mainly comprising a large coal-fired generating unit such as a million-kilowatt supercritical unit is basically formed. Therefore, the method has great practical significance and application value for the analysis and research of the million-kilowatt ultra-supercritical unit.
Compared with the traditional generator set, the million kilowatt ultra-supercritical generator set has the advantages of large scale, various devices, numerous parameters and mutual influence, long industrial process, multiple unit devices, wide spatial distribution and high safety requirement in the whole power generation process, and brings difficulty to state monitoring and fault diagnosis of the million kilowatt ultra-supercritical generator set. In addition, due to different reasons such as environmental conditions, fuel characteristics and load, the million kilowatt ultra-supercritical unit can operate under different working conditions. Especially, in recent years, due to the fact that new energy such as wind power, photoelectricity and the like are connected to the power grid, the load fluctuation of the power grid, the peak-valley difference is increased, and the requirement of a user side changes, the unit is in a full-working-condition operation mode with different working conditions switched frequently due to new normality such as frequent deep peak regulation and the like. And the large coal-fired power generation process has complex environment and long industrial process, and a plurality of variables still present different data distribution characteristics even under the same working condition. These all present significant challenges to fault detection and diagnosis for large coal-fired power generating units.
For the problem of fault detection of the thermal generator set, the predecessors have made corresponding research and discussion from different angles, and a corresponding online process monitoring method is provided. However, most of the existing methods are mainly centralized single-working-condition monitoring methods. The centralized single-working-condition monitoring method cannot obtain a good monitoring effect in the face of the characteristics of long flow, numerous variables, complex correlation and dynamic working conditions of the million-kilowatt ultra-supercritical unit. The invention further considers the complex correlation among a plurality of variables of the million kilowatt ultra-supercritical unit and the multi-distribution condition of the variables in the sample direction, and provides a novel multi-layer distributed online fault detection method for the million kilowatt ultra-supercritical unit.
Disclosure of Invention
The invention aims to provide a multi-layer distributed monitoring algorithm for million-kilowatt ultra-supercritical units, aiming at the problem that the existing fault detection method for the million-kilowatt ultra-supercritical units cannot accurately describe local information. The method comprehensively considers the correlation among the variables and the distribution condition of the variables in the sample direction, blocks the variables by using a multi-layer information theory decomposition method, fully explores the process information among the process variables, and is beneficial to understanding the complex process characteristics of the million kilowatt ultra-supercritical unit. The multilayer distributed monitoring method can effectively mine local information of the process, can analyze the correlation among different variable subblocks, and greatly improves the fault detection performance of the million-kilowatt ultra-supercritical unit in the complex process, thereby ensuring the safe and reliable operation of the large coal-fired generator set.
The purpose of the invention is realized by the following technical scheme: a distribution layered online fault detection method for a million kilowatt ultra-supercritical unit comprises the following steps:
(1) acquiring normal data to be analyzed: a million-kilowatt ultra-supercritical unit is provided with J measurement variables and operation variables, a vector of 1 XJ can be obtained by sampling every time, and data acquired after sampling N times is expressed as a two-dimensional matrix X ═ X1,X2,...,XJ]∈RN×JThe measured variables are state parameters which can be measured in the normal operation process of the unit, and comprise flow, voltage, current, temperature, speed and the like; the operation variables comprise air intake, feeding amount, valve opening and the like;
(2) the process variable is divided into different sub-blocks by using a spectral clustering method based on mutual information, the variable in the same sub-block has stronger correlation, and the correlation between different sub-blocks is weaker. This step is realized by the following substeps:
(2.1) obtaining mutual information among variables:
I(Xi,Xj)=H(Xi)+H(Xj)-H(Xi,Xj) (1)
wherein, Xi(i ═ 1, 2.., J) denotes the ith variable, H (X)i) Is a variable XiThe information entropy of (2):
H(Xi)=-∫xp(Xi)logp(Xi)dx (2)
H(Xi,Xj) Is a variable XiAnd XjJoint information entropy of (a):
p(Xi) And p (X)j) Represents variable XiAnd XjP (X) is a probability density function ofi,Xj) Is a joint probability density function.
(2.2) solving the generalized correlation coefficient between every two variables based on the mutual information solved by the formula (1):
wherein r isij∈[0,1]。
(2.3) based on equation (4), a correlation matrix of the variables is found:
(2.4) solving a diagonal matrix D based on the correlation matrix R defined by the formula (5):
D=diag{Dii} (6)
wherein D isiiIs the sum of all elements in row i in equation (5):
(2.5) solving Laplace matrix of diagonal matrix D
L=D-1/2RD-1/2(8)
(2.6) spectral decomposition of Laplace matrix
L=PΛPT(9)
Wherein, P ═ P1,P2,...,PJ]Are orthogonal eigenvectors.
(2.7) selecting the eigenvectors corresponding to the k maximum eigenvalues to form a matrix E ═ P1,P2,...,Pk]∈RJ×kNormalizing each row in the matrix E to obtain a matrix Y
(2.8) clustering Y by using a kmeans clustering algorithm, and if the ith row belongs to the b-th class, carrying out variable XiDivision into sub-block b Xb. Thus, a plurality of operation variables of the million-kilowatt ultra-supercritical unit are divided into B variable blocks according to the degree of correlation.
X=[X1X2… XB](11)
Wherein,is the (B ═ 1, 2.., B) th variable block, JbRepresents XbThe number of variables contained in (1).
(3) Further decomposing the variables in the variable block according to the distribution situation in the sample direction by using an information theory decomposition method based on a Gaussian mixture model, wherein the step is realized by the following sub-steps:
(3.1) randomly dividing the variable block into WbIndividual block:
(3.2) using gaussian mixture model method to obtain W (W1, 2.., W)b) Probability density of individual variable subblocks:
wherein,is the number of sub-gaussian components;is the prior probability of the mth sub-Gaussian component, satisfiesAndis a mean value containing sub-Gaussian componentsSum covariance matrixOf the parameter set (c).Is a multivariate gaussian probability density:
(3.3) solving probability density distribution functions of all variables in the sub-blocks:
wherein the variableJb,wIs a variable blockThe number of the medium variables is equal to or greater than the total number of the medium variables,represents Xb,iBelonging to sub-blocksWhen Xb,iThe conditional probability density of (2).
Wherein,andare respectivelyAndthe probability density function of (2) can be calculated by using the formula (13).
(3.5) optimizing the random partitions of step (3.1) using an ant colony algorithm such that the following objective function is maximized:
(3.6) each variable block (B ═ 1, 2.., B) is further divided into sub-blocks by repeating steps (3.2) - (3.5). The original data set X is divided into different sub-blocks:
wherein, the variable blockAll variables in the system have strong correlation, and variable sub-blocksThe variables in (a) have both strong correlations and similar data distributions.
(4) Based on the variable block result obtained in the steps (2) and (3), firstly, describing the variable sub-block by using a Principal Component Analysis (PCA)Correlation of each variable in the
Wherein, Pb,wIs a load matrix, Tb,wIs a principal component matrix.
(5) Principal component matrix T established by Gaussian Mixture Model (GMM) methodb,wThe distribution of (c):
wherein,is the number of gaussian components;the weight of the m-th component is represented,is a mean value containing sub-Gaussian componentsSum covariance matrixOf the parameter set (c).
Wherein,to representBelonging to the m-th componentThe probability of (a) of (b) being,as a principal component matrix Tb,wAn nth (N ═ 1, 2.., N) row vector.Is based on the probability of local Mahalanobis distance, which is defined as
Wherein,is composed ofMahalanobis distance to mth gaussian component, T being Tb,wAny one of the rows.
(7) The relationship between each sub-block in each variable block is monitored by a Gaussian Mixture Model (GMM) method, which is implemented by the following sub-steps.
(7.1) blocking each variable block XbThe first columns of the pivot matrices of the respective sub-blocks are combined together:
wherein, tb,w(w=1,2,...,Wb) As a principal component matrix Tb,wThe 1 st column vector.
wherein,the number of Gaussian components in the b variable sub-block is shown;the weight of the m-th component is represented,is a mean value containing sub-Gaussian componentsSum covariance matrixOf the parameter set (c).
wherein,as a principal component matrixAn nth (N ═ 1, 2.., N) row vector.Is based on the probability of the local mahalanobis distance.Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to the mth gaussian component,is composed ofAny one of the rows.
(8) During online fault detection, the process is monitored from three levels of variable subblocks, variable blocks and the whole unit. This step is realized by the following substeps.
(8.1) acquiring new data: and (4) collecting the variable values of the measuring points according to the step (1) and recording as z (1 multiplied by J).
(8.2) according to the variable blocking results obtained in the step (2) and the step (3), carrying out sub-block decomposition on the new data:
z=[z1z2… zb… zB](26)
wherein z isb(B ═ 1, 2.., B) is the B variable sub-block.
(8.3) at the bottom layer, i.e., variable sub-block layer, each sub-block The data of (2) are projected to the principal element direction of the corresponding sub-block:
wherein, the meaning of each parameter in the above formula is similar to that in the formula (22).To representBelonging to the m-th componentThe probability of (c).Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to mth gaussian component, T being Tb,wAny one of the rows.
(8.5) at the variable block level, z is first putbThe main elements of each variable sub-block are combined together:
(8.6) obtaining each variable block zbThe online statistic index of (1):
wherein, the meaning of each parameter of the above formula is similar to that in the formula (25).To representBelonging to the m-th componentThe probability of (c).Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to the mth gaussian component,is composed ofAny one of the rows.
(8.7) in order to analyze the relation between different variable subblocks, the operation condition of the million kilowatt ultra-supercritical unit is monitored from the whole unit level, and the BIP index of each variable block is firstly converted into the probability of normal (marked as 'N') and fault (marked as 'F'):
wherein BIPb,lmtA control limit for the statistical BIP indicator;representing the normal conditional probability of the b variable block;indicating the conditional probability of the failure of the b-th variable block.
(8.8) calculating the posterior probability of the b variable block failing by the Bayes rule
Wherein, Pb(F)=α;Pb(N) ═ 1-alpha, respectively, for significanceThe level is the prior probability of a process failing or being normal at alpha.
(8.9) comprehensively considering the fault probability of all variable blocks and calculating the global monitoring statistic
(9) Judging the running state of the process: and analyzing the process state from three levels of the variable subblocks, the variable blocks and the whole unit. Three levels of statistics are compared with the control limits in real time:
(a) at each variable sub-blockIn, if BIPb,w1-alpha, in sub-blocksThe variable in (b) fails, otherwise the variable in the sub-block is considered to be operating within the normal range.
(b) At the variable block level, if BIPbIf the value is more than 1-alpha, the related relation of each variable sub-block in the variable block is abnormal, otherwise, all the variables in the b-th sub-block are normally operated.
(c) At the unit level, if PFzIf the measured value is more than alpha, the abnormal condition or the fault occurs in the running process of the million kilowatt ultra-supercritical unit, otherwise, the whole unit runs normally.
Compared with the prior art, the invention has the beneficial effects that: the invention aims to provide a multi-layer distributed monitoring algorithm for million-kilowatt ultra-supercritical units, aiming at the characteristics that million-kilowatt ultra-supercritical units are large in scale, various in equipment, numerous in parameters and mutually influenced, and the whole power generation process is long in industrial process, multiple in unit devices, wide in spatial distribution and frequent in working condition switching. The method comprehensively considers the correlation among the variables and the distribution condition of the variables in the sample direction, blocks the variables by using a multi-layer information theory decomposition method, fully explores the process information among the process variables, and is beneficial to understanding the complex process characteristics of the million kilowatt ultra-supercritical unit. The multilayer distributed monitoring method can effectively mine local information of the process, can analyze the correlation among different variable subblocks, and greatly improves the fault detection performance of the million-kilowatt ultra-supercritical unit in the complex process, thereby ensuring the safe and reliable operation of the large coal-fired generator set.
Description of the drawings:
FIG. 1 is an explanatory diagram of a distributed hierarchical online fault detection method for a million kilowatt ultra-supercritical unit according to the invention;
fig. 2 shows the monitoring results of the variable sub-blocks in the specific embodiment of the method of the present invention, (a) shows the monitoring results of two variable sub-blocks in the 5 th variable block, (b) shows the monitoring results of three variable sub-blocks in the 7 th variable block, and (c) shows the monitoring results of three variable sub-blocks in the 9 th variable block.
Fig. 3 shows the monitoring results in the variable layer of the method of the present invention in a specific embodiment, (a) is the monitoring result in the 5 th variable block, (b) is the monitoring result in the 7 th variable block, and (c) is the monitoring result in the 9 th variable block.
Fig. 4 shows the unit level monitoring result of the method according to the present invention in an embodiment.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific examples.
The invention takes the unit of Zhe energy group subordinate Jiahua power plant No. 3 as an example, the unit is a million kilowatt ultra-supercritical unit, the power of the unit is 600MW, the unit totally comprises 154 process variables, and the variables relate to pressure, temperature, flow rate and the like.
As shown in figure 1, the invention discloses an online monitoring method for the dynamic and static characteristic collaborative analysis of a million kilowatt ultra-supercritical unit, which comprises the following steps:
(1) acquiring normal data to be analyzed: setting a million kilowatt ultra-supercritical unit to have J measurement variables and operation variables, obtaining a 1 XJ vector by sampling every time, and expressing data obtained after sampling N times into twoDimension matrix X ═ X1,X2,...,XJ]∈RN×J. In this example, the sampling period is 1 minute, 2940 sample data in the normal operation process of the thermal power generating unit are collected for variable blocking and offline modeling, and 154 process variables, namely, the modeling data is X (2940 × 154). The measurement variables are state parameters which can be measured in the normal operation process of the unit, and comprise flow, voltage, current, temperature, speed and the like; the operation variables comprise air intake, feeding amount, valve opening and the like;
(2) the process variable is divided into different sub-blocks by using a spectral clustering method based on mutual information, the variable in the same sub-block has stronger correlation, and the correlation between different sub-blocks is weaker. This step is realized by the following substeps:
(2.1) obtaining mutual information among variables:
I(Xi,Xj)=H(Xi)+H(Xj)-H(Xi,Xj) (1)
wherein, Xi(i ═ 1, 2.., J) denotes the ith variable, H (X)i) Is a variable XiThe information entropy of (2):
H(Xi)=-∫xp(Xi)logp(Xi)dx (2)
H(Xi,Xj) Is a variable XiAnd XjJoint information entropy of (a):
p(Xi) And p (X)j) Represents variable XiAnd XjP (X) is a probability density function ofi,Xj) Is a joint probability density function.
(2.2) solving the generalized correlation coefficient between every two variables based on the mutual information solved by the formula (1):
wherein r isij∈[0,1]。
(2.3) based on the formula (4), obtaining a correlation matrix of the variables:
(2.4) solving a diagonal matrix D based on the correlation matrix R defined by the formula (5):
D=diag{Dii} (6)
wherein D isiiIs the sum of all elements in the ith row in formula (5)
(2.5) solving Laplace matrix of diagonal matrix D
L=D-1/2RD-1/2(8)
(2.6) spectral decomposition of Laplace matrix
L=PΛPT(9)
Wherein, P ═ P1,P2,...,PJ]Are orthogonal eigenvectors.
(2.7) selecting the eigenvectors corresponding to the k maximum eigenvalues to form a matrix E ═ P1,P2,...,Pk]∈RJ×kNormalizing each row in the matrix E to obtain a matrix Y
(2.8) clustering Y by using a kmeans clustering algorithm, and if the ith row belongs to the b-th class, carrying out variable XiDivision into sub-block b Xb. Thus, a plurality of operation variables of the million-kilowatt ultra-supercritical unit are divided into B variable blocks according to the degree of correlation.
X=[X1X2... XB](11)
Wherein,is the (B ═ 1, 2.., B) th variable block, JbRepresents XbThe number of variables contained in (1).
In this example, 154 process variables are divided into 11 sub-blocks according to the correlation, as shown in table 1, the variables in each sub-block have a strong correlation, and the correlation between different sub-blocks is weak.
TABLE 1 variable blocking in megawatt ultra supercritical units
(3) Further decomposing the variables in the 11 variable blocks according to the distribution situation in the sample direction by using an information theory decomposition method based on a Gaussian mixture model, wherein the step is realized by the following sub-steps
(3.1) randomly dividing the variable block into WbIndividual block:
(3.2) using gaussian mixture model method to obtain W (W1, 2.., W)b) Probability density of individual variable subblocks:
wherein,is the number of sub-gaussian components;is the prior probability of the mth sub-Gaussian component, satisfiesAndis composed of sub-Gaussian componentsMean value ofSum covariance matrixOf the parameter set (c).Is a multivariate gaussian probability density:
(3.3) solving probability density distribution functions of all variables in the sub-blocks:
wherein the variableJb,wIs a variable blockThe number of the medium variables is equal to or greater than the total number of the medium variables,represents Xb,iBelonging to sub-blocksWhen XbiThe conditional probability density of (2).
Wherein,andare respectivelyAndthe probability density function of (2) can be calculated by using the formula (13).
(3.5) optimizing the random partitions of step (3.1) using an ant colony algorithm such that the following objective function is maximized:
(3.6) each variable block (B ═ 1, 2.., B) is further divided into sub-blocks by repeating steps (3.2) - (3.5). The original data set X is divided into different sub-blocks:
wherein, the variable blockAll variables in the system have strong correlation, and variable sub-blocksThe variables in (a) have both strong correlations and similar data distributions.
In this example, the 11 variable blocks obtained in step (2) are further divided into 27 variable sub-blocks according to the distribution of the variables, and the variables in each sub-block have both strong correlation and the same distribution.
TABLE 2 partitioning of variable sub-blocks in megawatt-hour ultra-supercritical units
(4) Based on the variable block result obtained in the steps (2) and (3), firstly, describing the variable sub-block by using a Principal Component Analysis (PCA)Correlation of each variable in the
Wherein, Pb,wIs a load matrix, Tb,wIs a principal component matrix.
(5) Principal component matrix T established by Gaussian Mixture Model (GMM) methodb,wThe distribution of (c):
wherein,is the number of gaussian components;the weight of the m-th component is represented,is a mean value containing sub-Gaussian componentsSum covarianceMatrix arrayOf the parameter set (c).
Wherein,to representBelonging to the m-th componentThe probability of (a) of (b) being,as a principal component matrix Tb,wAn nth (N ═ 1, 2.., N) row vector.Is based on the probability of local Mahalanobis distance, which is defined as
Wherein,is composed ofMahalanobis distance to mth gaussian component, T being Tb,wAny one of the rows.
(7) The relationship between each sub-block in each variable block is monitored by a Gaussian Mixture Model (GMM) method, which is implemented by the following sub-steps.
(7.1) blocking each variable block XbThe first columns of the pivot matrices of the respective sub-blocks are combined together:
wherein, tb,w(w=1,2,...,Wb) As a principal component matrix Tb,wThe 1 st column vector.
wherein,the number of Gaussian components in the b variable sub-block is shown;the weight of the m-th component is represented,is a mean value containing sub-Gaussian componentsSum covariance matrixOf the parameter set (c).
wherein,as a principal component matrixAn nth (N ═ 1, 2.., N) row vector.Is based on the probability of the local mahalanobis distance.Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to the mth gaussian component,is composed ofAny one of the rows.
(8.1) fault data preparation: here, the collected fault data contains 460 samples in total, and the data is recorded as Z (460 × 154), the fault is the increase of the circulating water pump outlet pressure, and the fault occurs at the 121 th sampling point.
(8.2) according to the variable blocking results obtained in the steps (2) and (3), new data is recorded as z (1 × 154), and sub-block decomposition is performed, wherein in the present example, B is 11:
z=[z1z2... zb... zB](26)
wherein z isb(B ═ 1, 2.., B) is the B variable sub-block.
(8.3) at the bottom layer, i.e., variable sub-block layer, each sub-block The data of (2) are projected to the principal element direction of the corresponding sub-block:
wherein, the meaning of each parameter in the above formula is similar to that in the formula (22).To representBelonging to the m-th componentThe probability of (c).Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to mth gaussian component, T being Tb,wAny one of the rows.
(8.5) at the variable block level, z is first putbThe main elements of each variable sub-block are combined together:
(8.6) obtaining each variable block zbThe online statistic index of (1):
wherein, the meaning of each parameter of the above formula is similar to that in the formula (25).To representBelonging to the m-th componentThe probability of (c).Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to the mth gaussian component,is composed ofAny one of the rows.
(8.7) in order to analyze the relation between different variable subblocks, the operation condition of the million kilowatt ultra-supercritical unit is monitored from the whole unit level, and the BIP index of each variable block is firstly converted into the probability of normal (marked as 'N') and fault (marked as 'F'):
wherein BIPb,lmtFor the control limit of the statistic BIP, 0.5 is taken in the specific embodiment;representing the normal conditional probability of the b variable block;indicating the conditional probability of the failure of the b-th variable block.
(8.8) calculating the posterior probability of the b variable block failing by the Bayes rule
Wherein, Pb(F)=α;Pb1- α represents the prior probability of the process failing or being normal, respectively, at a significance level α, which in this example is 0.5.
(8.9) comprehensively considering the fault probability of all variable blocks and calculating the global monitoring statistic
(9) Judging the running state of the process: and analyzing the process state from three levels of the variable subblocks, the variable blocks and the whole unit. Three levels of statistics are compared with the control limits in real time:
(a) at each variable sub-blockIn, if BIPb,w1-alpha, in sub-blocksThe variable in (b) fails, otherwise the variable in the sub-block is considered to be operating within the normal range.
(b) At the variable block level, if BIPbIf the value is more than 1-alpha, the related relation of each variable sub-block in the variable block is abnormal, otherwise, all the variables in the b-th sub-block are normally operated.
(c) At the unit level, if PFzIf the measured value is more than alpha, the abnormal condition or the fault occurs in the running process of the million kilowatt ultra-supercritical unit, otherwise, the whole unit runs normally.
The thermal power process is monitored on line by using the monitoring method disclosed by the invention, and the results are shown in fig. 2-4. FIG. 2 shows the monitoring results of the method of the present invention in 8 variable sub-blocks. As can be seen from fig. 2(a), the statistics of the two variable sub-blocks of the fifth variable block are basically below the control limit, which indicates that the current fault does not affect the variables in the variable block #5, and these variables are all operating normally. As can be seen from fig. 2(b), in the first 120 samples, the statistics of the first two sub-blocks of variable block #7 are basically below the control limit, indicating that the process is operating normally. Starting from the 121 th sample, the variable sub-block statistic BIPsub7,1And BIPsub7,2The control limit is quickly exceeded and a fault occurrence is detected, indicating that the fault significantly affects the variables in both sub-blocks. Also, analyzing the monitoring results of fig. 2(c), it can be found that the variables in the first two sub-blocks of variable block #9 operate substantially normally, but BIPsub9,3The occurrence of the failure is effectively detected.
Fig. 3 shows the partial monitoring results of the method of the invention in the variable layer. As can be seen in fig. 3(a), the fifth variable block is substantially below the control limit, indicating that the correlation between the two variable sub-blocks in variable block #5 is not affected by a fault and the process variable in variable block #5 is operating normally. The monitoring results of FIG. 3(b) and FIG. 3(c) are shown separatelyThe correlation between the variable subblocks in the variable block #7 and the variable block #9 is affected by a failure, and an abnormality occurs. Fig. 4 shows the monitoring results of the inventive method at the stack level. It can be seen that the statistics of the first 120 samples are basically operated below the control limit, which indicates that the megawatt ultra-supercritical unit is operated under the normal working condition. Starting from the 121 th sample, the statistic PFzAnd immediately exceeding the control limit, and effectively detecting the occurrence of the fault. Generally speaking, the layered distributed fault detection method has excellent fault detection performance when monitoring a typical large-scale multi-working-condition process of million kilowatt ultra-supercritical, and the blocking result effectively analyzes complex correlation among a plurality of variables, so that the understanding of an operator to the process can be deepened, high-precision online process monitoring results can be provided for a technical management department on an actual industrial field of a thermal power plant, a reliable basis is provided for judging the process running state in real time and identifying whether a fault occurs, and the safety, reliability and effectiveness of running of the million kilowatt ultra-supercritical unit are further improved.
Claims (1)
1. A distribution layered online fault detection method for a million kilowatt ultra-supercritical unit is characterized by comprising the following steps:
(1) acquiring normal data to be analyzed: a million-kilowatt ultra-supercritical unit is provided with J measurement variables and operation variables, a vector of 1 XJ can be obtained by sampling every time, and data acquired after sampling N times is expressed as a two-dimensional matrix X ═ X1,X2,...,XJ]∈RN×JThe measured variables are state parameters which can be measured in the normal operation process of the unit, and comprise flow, voltage, current, temperature, speed and the like; the operation variables comprise air intake, feeding amount, valve opening and the like;
(2) the process variable is divided into different sub-blocks by using a spectral clustering method based on mutual information, the variable in the same sub-block has stronger correlation, and the correlation between different sub-blocks is weaker. This step is realized by the following substeps:
(2.1) obtaining mutual information among variables:
I(Xi,Xj)=H(Xi)+H(Xj)-H(Xi,Xj) (1)
wherein, Xi(i ═ 1, 2.., J) denotes the ith variable, H (X)i) Is a variable XiThe information entropy of (2):
H(Xi)=-∫xp(Xi)logp(Xi)dx (2)
H(Xi,Xj) Is a variable XiAnd XjJoint information entropy of (a):
p(Xi) And p (X)j) Represents variable XiAnd XjP (X) is a probability density function ofi,Xj) Is a joint probability density function.
(2.2) solving the generalized correlation coefficient between every two variables based on the mutual information solved by the formula (1):
wherein r isij∈[0,1]。
(2.3) based on equation (4), a correlation matrix of the variables is found:
(2.4) solving a diagonal matrix D based on the correlation matrix R defined by the formula (5):
D=diag{Dii} (6)
wherein D isiiIs the sum of all elements in row i in equation (5):
(2.5) solving a Laplace matrix of the diagonal matrix D:
L=D-1/2RD-1/2(8)
(2.6) performing spectral decomposition on the Laplace matrix:
L=PΛPT(9)
wherein, P ═ P1,P2,...,PJ]Are orthogonal eigenvectors.
(2.7) selecting the eigenvectors corresponding to the k maximum eigenvalues to form a matrix E ═ P1,P2,...,Pk]∈RJ×kNormalizing each row in the matrix E to obtain a matrix Y:
(2.8) clustering Y by using a kmeans clustering algorithm, and if the ith row belongs to the b-th class, carrying out variable XiDivision into sub-block b Xb. Thus, a plurality of operation variables of the million-kilowatt ultra-supercritical unit are divided into B variable blocks according to the correlation degree:
X=[X1X2… XB](11)
wherein,is the (B ═ 1, 2.., B) th variable block, JbRepresents XbThe number of variables contained in (1).
(3) The variables in the variable block are further decomposed according to the distribution situation in the sample direction by using an information theory decomposition method based on a Gaussian mixture model, and the step is realized by the following substeps.
(3.1) randomly dividing the variable block into WbIndividual block:
(3.2) using gaussian mixture model method to obtain W (W1, 2.., W)b) Probability density of individual variable subblocks:
wherein,is the number of sub-gaussian components;is the prior probability of the mth sub-Gaussian component, satisfiesAndis a mean value containing sub-Gaussian componentsSum covariance matrixOf the parameter set (c).Is a multivariate gaussian probability density:
(3.3) solving probability density distribution functions of all variables in the sub-blocks:
wherein the variableJb,wIs a variable blockThe number of the medium variables is equal to or greater than the total number of the medium variables,represents Xb,iBelonging to sub-blocksWhen Xb,iThe conditional probability density of (2).
Wherein,andare respectivelyAndthe probability density function of (2) can be calculated by using the formula (13).
(3.5) optimizing the random partitions of step (3.1) using an ant colony algorithm such that the following objective function is maximized:
(3.6) each variable block (B ═ 1, 2.., B) is further divided into sub-blocks by repeating steps (3.2) - (3.5). The original data set X is divided into different sub-blocks:
(4) Based on the variable block result obtained in the steps (2) and (3), firstly, describing the variable sub-block by using a Principal Component Analysis (PCA)The correlation relationship of each variable in (1):
wherein, Pb,wIs a load matrix, Tb,wIs a principal component matrix.
(5) Principal component matrix T established by Gaussian Mixture Model (GMM) methodb,wThe distribution of (c):
wherein,is the number of gaussian components;the weight of the m-th component is represented,is a mean value containing sub-Gaussian componentsSum covariance matrixOf the parameter set (c).
Wherein,to representBelonging to the m-th componentThe probability of (a) of (b) being,as a principal component matrix Tb,wAn nth (N ═ 1, 2.., N) row vector.Is based on the probability of local Mahalanobis distance, which is defined as
Wherein,is composed ofMahalanobis distance to mth gaussian component, T being Tb,wAny one of the rows.
(7) The relationship between each sub-block in each variable block is monitored by a Gaussian Mixture Model (GMM) method, which is implemented by the following sub-steps.
(7.1) blocking each variable block XbThe first columns of the pivot matrices of the respective sub-blocks are combined together:
wherein, tb,w(w=1,2,...,Wb) As a principal component matrix Tb,wThe 1 st column vector.
wherein,the number of Gaussian components in the b variable sub-block is shown;the weight of the m-th component is represented,is composed of sub-Gaussian componentsMean value ofSum covariance matrixOf the parameter set (c).
wherein,as a principal component matrixAn nth (N ═ 1, 2.., N) row vector.To representBelonging to the m-th componentThe probability of (c).Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to the mth gaussian component,is composed ofAny one of the rows.
(8) During online fault detection, the process is monitored from three levels of variable subblocks, variable blocks and the whole unit. This step is realized by the following substeps.
(8.1) acquiring new data: and (4) collecting the variable values of the measuring points according to the step (1) and recording as z (1 multiplied by J).
(8.2) according to the variable blocking results obtained in the step (2) and the step (3), carrying out sub-block decomposition on the new data:
z=[z1z2... zb... zB](26)
wherein z isb(B ═ 1, 2.., B) is the B variable sub-block.
(8.3) at the bottom layer, i.e., variable sub-block layer, each sub-block The data of (2) are projected to the principal element direction of the corresponding sub-block:
wherein, the meaning of each parameter in the above formula is similar to that in the formula (22).To representBelonging to the m-th componentThe probability of (c).Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to mth gaussian component, T being Tb,wAny one of the rows.
(8.5) at the variable block level, z is first putbThe main elements of each variable sub-block are combined together:
(8.6) obtaining each variable block zbThe online statistic index of (1):
wherein, the meaning of each parameter of the above formula is similar to that in the formula (25).To representBelonging to the m-th componentThe probability of (c).Is based on the probability of the local mahalanobis distance,is composed ofMahalanobis distance to the mth gaussian component,is composed ofAny one of the rows.
(8.7) converting the BIP index of each variable block into the probability of normal (labeled 'N') and fault (labeled 'F'):
wherein BIPb,lmtA control limit for the statistical BIP indicator;representing the normal conditional probability of the b variable block;indicating the conditional probability of the failure of the b-th variable block.
(8.8) calculating the posterior probability of the b variable block failing by the Bayes rule
Wherein, Pb(F)=α;Pb(N) ═ 1- α represents the prior probability of the process failing or being normal, respectively, at a level of significance α.
(8.9) comprehensively considering the fault probability of all variable blocks and calculating the global monitoring statistic
(9) Judging the running state of the process: and analyzing the process state from three levels of the variable subblocks, the variable blocks and the whole unit. Three levels of statistics are compared with the control limits in real time:
(a) at each variable sub-blockIn, if BIPb,w1-alpha, in sub-blocksThe variable in (b) fails, otherwise the variable in the sub-block is considered to be operating within the normal range.
(b) At the variable block level, if BIPbIf the value is more than 1-alpha, the related relation of each variable sub-block in the variable block is abnormal, otherwise, all the variables in the b-th sub-block are normally operated.
(c) At the unit level, if PFzIf the measured value is more than alpha, the abnormal condition or the fault occurs in the running process of the million kilowatt ultra-supercritical unit, otherwise, the whole unit runs normally.
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