CN111983997B - A method and system for monitoring control loop performance based on coupling analysis - Google Patents

Abstract

The invention discloses a control loop performance monitoring method and system based on coupling analysis. The method includes: according to the actual measured value, preset value and control mode of the current control loop, using a minimum variance control method to evaluate the loop performance, and obtaining the performance evaluation result of the current control loop; Meet the preset performance requirements; if it does not meet the preset performance requirements, according to the coupling relationship table, determine whether the source loop that causes the current control loop to fail to meet the preset performance requirements is the current control loop or the upstream control loop. Using the method and system of the present invention, the upstream and downstream correlation between serial loops can be found through coupling analysis, so as to find the root loop that causes poor performance of the control loop, and it is convenient for users to find and solve problems.

Description

A method and system for monitoring control loop performance based on coupling analysis

technical field

The invention relates to the technical field of control loop performance monitoring, in particular to a control loop performance monitoring method and system based on coupling analysis.

Background technique

In the process of petroleum refining, the proportional integral derivative control (PID control) strategy is the most widely used. The advantages of PID control are: simple structure, convenient adjustment and strong robustness. However, the performance of the control loop will degrade with the increase of the continuous operation time of the production equipment. Up to 60% of the control loops in the equipment have different degrees of performance defects. If the important control loops are not maintained in time and effectively, the control performance will not only deteriorate. It will affect the stability of device operation, product quality, product yield, material consumption, energy consumption, etc., and even endanger the safety of device operation in severe cases.

The traditional control loop performance monitoring method can only judge the operation performance of a single loop. However, when the loop performance monitoring shows that the performance of a loop is poor, it is often not necessarily the problem of the current control loop itself, but may be affected by its upstream control loop. Therefore, the traditional method cannot find the root cause of the poor loop performance, which brings inconvenience for users to find and solve the problem.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a control loop performance monitoring method and system based on coupling analysis. Through coupling analysis, the upstream and downstream correlation between serial loops can be found, so as to find the root loop that causes poor performance of the control loop, which is convenient for users Find and fix problems.

For achieving the above object, the present invention provides the following scheme:

A control loop performance monitoring method, comprising:

Obtain the actual measured value, preset value and control mode of the current control loop; the control mode includes manual control and automatic control;

According to the actual measured value of the current control loop, the preset value and the control mode, a minimum variance control method is used to evaluate the loop performance, and the current control loop performance evaluation result is obtained;

Determine whether the current control loop meets the preset performance requirements according to the performance evaluation result of the current control loop; if it does not meet the preset performance requirements, then determine according to the coupling relationship table that the source loop that causes the current control loop to fail to meet the preset performance requirements is: The current control loop is still the upstream control loop; the coupling relationship table is a table established by the coupling analysis method to reflect the degree of correlation between the current control loop and the upstream control loop.

Optionally, according to the actual measurement value of the current control loop, the preset value and the control mode, the loop performance evaluation is performed using a minimum variance control method, which specifically includes:

Calculate the deviation standard deviation according to the actual measured value of the current control loop and the preset value of the current control loop;

Calculate the control loop oscillation index according to the actual measured value of the current control loop, the preset value and the control mode;

Obtaining the expected steady state time and the actual steady state time of the control loop, and calculating the relative performance index of the control loop according to the expected steady state time and the actual steady state time of the control loop;

Loop performance evaluation is performed according to the standard deviation of the deviation, the control loop oscillation index and the control loop relative performance index.

Optionally, performing the loop performance evaluation according to the deviation standard deviation, the control loop oscillation index and the control loop relative performance index specifically includes:

Obtain the preset value of deviation standard deviation, preset value of control loop oscillation index and preset interval of relative performance index of control loop;

At the same time, the deviation standard deviation is less than the deviation standard deviation preset value, the control loop oscillatory index is less than the control loop oscillatory index preset value, and the control loop relative performance index in the control loop relative performance index When the index is within the preset interval, the current control loop meets the preset performance requirements; otherwise, the current control loop does not meet the preset performance requirements.

Optionally, the method for establishing the coupling relationship table specifically includes:

obtaining actual measurements of all upstream control loops in series with the current control loop;

According to the actual measurement value of each upstream control loop and the actual measurement value of the current control loop, a coupling analysis method is used to determine the degree of correlation between each upstream control loop and the current control loop;

A coupling relationship table is established according to the correlation degree.

Optionally, determining whether the source loop that causes the current control loop to fail to meet the preset performance requirements is the current control loop or the upstream control loop according to the coupling relationship table, specifically including:

Get the preset value of correlation degree;

According to the coupling relationship table, filter out the upstream control loops corresponding to the preset value of the correlation degree to obtain an upstream control loop set; the upstream control loops in the upstream control loop set are adjacent to each other;

Numbering each upstream control loop in the set of upstream control loops in order from downstream to upstream;

Find out whether there is an upstream control loop adjacent to the current control loop in the set of upstream control loops; if not, determine that the current control loop is the source loop that causes the current control loop to fail to meet the preset performance requirements; if If there is, the upstream control loop corresponding to the maximum number in the upstream control loop set is determined as the source loop that causes the current control loop to fail to meet the preset performance requirement.

The present invention also provides a control loop performance monitoring system, comprising:

a data acquisition module for acquiring the actual measured value, preset value and control mode of the current control loop; the control mode includes manual control and automatic control;

a loop performance monitoring module, configured to perform loop performance evaluation using a minimum variance control method according to the actual measured value of the current control loop, the preset value and the control mode, and obtain the current control loop performance evaluation result;

The coupling analysis module is used to judge whether the current control loop meets the preset performance requirements according to the performance evaluation result of the current control loop; if it does not meet the preset performance requirements, it is determined according to the coupling relationship table that the current control loop does not meet the preset performance requirements. It is assumed that the source loop of the performance requirement is the current control loop or the upstream control loop; the coupling relationship table is a table established by coupling analysis method to reflect the degree of correlation between the current control loop and the upstream control loop.

Optionally, the loop performance monitoring module specifically includes:

a deviation standard deviation calculation unit, configured to calculate the deviation standard deviation according to the actual measured value of the current control loop and the preset value of the current control loop;

a control loop oscillation index calculation unit, configured to calculate a control loop oscillation index according to the actual measured value of the current control loop, the preset value and the control mode;

a control loop relative performance index calculation unit, configured to obtain the expected steady state time and the actual steady state time of the control loop, and calculate the control loop relative performance index according to the control loop expected steady state time and the actual steady state time;

A loop performance evaluation unit, configured to perform loop performance evaluation according to the deviation standard deviation, the control loop oscillation index and the control loop relative performance index.

Optionally, the loop performance evaluation unit specifically includes:

a data acquisition sub-unit, used for acquiring the preset value of the deviation standard deviation, the preset value of the control loop oscillation index and the preset interval of the relative performance index of the control loop;

A loop performance evaluation subunit, configured to simultaneously satisfy that the standard deviation of the deviation is less than the preset value of the standard deviation of the deviation, the oscillation index of the control loop is smaller than the preset value of the oscillation index of the control loop, and the relative performance of the control loop is satisfied When the index is within the preset range of the relative performance index of the control loop, the current control loop meets the preset performance requirements; otherwise, the current control loop does not meet the preset performance requirements.

Optionally, the coupling analysis module specifically includes:

A coupling relationship table establishment unit is used to obtain the actual measured values of all upstream control loops in series with the current control loop; according to the actual measured value of each upstream control loop and the actual measured value of the current control loop, the The correlation analysis method determines the degree of correlation between each upstream control loop and the current control loop; establishes a coupling relationship table according to the degree of correlation.

Optionally, the coupling analysis module further includes:

a root loop determination unit, configured to obtain a preset value of the correlation degree; according to the coupling relationship table, filter out the upstream control loops corresponding to the preset value of the correlation degree, and obtain an upstream control loop set; in the upstream control loop set The upstream control loops are adjacent to each other; number each upstream control loop in the set of upstream control loops in the order from downstream to upstream; find out whether there is a loop similar to the current control loop in the set of upstream control loops The adjacent upstream control loop; if it does not exist, it is determined that the current control loop is the source loop that causes the current control loop to fail to meet the preset performance requirements; if it exists, the upstream control loop set corresponding to the maximum number is determined A control loop is identified as the root loop that causes the current control loop to fail to meet preset performance requirements.

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

The invention proposes a method and system for monitoring the performance of a control loop based on coupling analysis. According to the actual measured value, preset value and control mode of the current control loop, the minimum variance control method is used to evaluate the loop performance, and the current control loop performance is obtained. Evaluation results; according to the current control loop performance evaluation results, determine whether the current control loop meets the preset performance requirements; if it does not meet the preset performance requirements, then determine according to the coupling relationship table that the root loop that causes the current control loop to fail to meet the preset performance requirements is the current Whether the control loop is still the upstream control loop, the correlation between the upstream and downstream of the serial loops can be found through coupling analysis, so as to find the root loop that causes the poor performance of the control loop, and it is convenient for users to find and solve the problem.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

1 is a flowchart of a method for monitoring performance of a control loop based on coupling analysis in an embodiment of the present invention;

2 is a structural diagram of a control loop performance monitoring system based on coupling analysis in an embodiment of the present invention;

3 is a schematic diagram of a control loop performance monitoring system in an embodiment of the present invention;

4 is a flow chart of system data processing in an embodiment of the present invention;

FIG. 5 is a flowchart of a method for finding a root loop in an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a control loop performance monitoring method and system based on coupling analysis. Through coupling analysis, the upstream and downstream correlation between serial loops can be found, so as to find the root loop that causes poor performance of the control loop, which is convenient for users Find and fix problems.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Example

FIG. 1 is a flowchart of a method for monitoring performance of a control loop based on coupling analysis in an embodiment of the present invention. As shown in FIG. 1 , a method for monitoring performance of a control loop based on coupling analysis includes:

Step 101: Acquire the actual measured value, preset value and control mode of the current control loop; the control mode includes manual control and automatic control.

Step 102 : According to the actual measurement value, preset value and control mode of the current control loop, use the minimum variance control method to evaluate the loop performance, and obtain the current control loop performance evaluation result.

Step 102 specifically includes:

Calculate the deviation standard deviation according to the actual measured value of the current control loop and the preset value of the current control loop;

Calculate the control loop oscillation index according to the actual measured value, preset value and control mode of the current control loop;

Obtain the expected steady state time and actual steady state time of the control loop, and calculate the relative performance index of the control loop according to the expected steady state time and actual steady state time of the control loop;

The loop performance is evaluated according to the standard deviation of the deviation, the oscillation index of the control loop and the relative performance index of the control loop, including:

Obtain the preset value of deviation standard deviation, preset value of control loop oscillation index and preset interval of relative performance index of control loop;

When the standard deviation of the deviation is less than the preset value of the standard deviation of the deviation, the oscillation index of the control loop is less than the preset value of the oscillation index of the control loop, and the relative performance index of the control loop is within the preset range of the relative performance index of the control loop, the current control loop meets the preset value. set performance requirements; otherwise, the current control loop does not meet the preset performance requirements.

Step 103: Determine whether the current control loop meets the preset performance requirements according to the performance evaluation result of the current control loop; if it does not meet the preset performance requirements, determine according to the coupling relationship table that the source loop that causes the current control loop to fail to meet the preset performance requirements is the current control loop. The control loop is still the upstream control loop; the coupling relationship table is a table established by the coupling analysis method to reflect the degree of correlation between the current control loop and the upstream control loop.

Among them, the specific establishment method of the coupling relationship table includes:

Get actual measurements of all upstream control loops in series with the current control loop;

According to the actual measured value of each upstream control loop and the actual measured value of the current control loop, the coupling analysis method is used to determine the degree of correlation between each upstream control loop and the current control loop;

Create a coupling relationship table according to the degree of correlation.

According to the coupling relationship table, determine whether the source loop that causes the current control loop to fail to meet the preset performance requirements is the current control loop or the upstream control loop, including:

Get the preset value of correlation degree;

According to the coupling relationship table, filter out the upstream control loops corresponding to the preset value of the correlation degree, and obtain the upstream control loop set; the upstream control loops in the upstream control loop set are adjacent to each other;

Numbering each upstream control loop in the set of upstream control loops in order from downstream to upstream;

Find out whether there is an upstream control loop adjacent to the current control loop in the upstream control loop set; if not, determine that the current control loop is the source loop that causes the current control loop to fail to meet the preset performance requirements; The upstream control loop corresponding to the maximum number in the loop set is determined as the root loop that causes the current control loop to fail to meet the preset performance requirements.

FIG. 2 is a structural diagram of a control loop performance monitoring system based on coupling analysis in an embodiment of the present invention. As shown in Figure 2, a control loop performance monitoring system based on coupling analysis includes:

The data acquisition module 201 is used to acquire the actual measured value, preset value and control mode of the current control loop; the control mode includes manual control and automatic control.

The loop performance monitoring module 202 is configured to use the minimum variance control method to evaluate the loop performance according to the actual measured value, preset value and control mode of the current control loop, and obtain the current control loop performance evaluation result.

The loop performance monitoring module 202 specifically includes:

a deviation standard deviation calculation unit, used for calculating the deviation standard deviation according to the actual measured value of the current control loop and the preset value of the current control loop;

The control loop oscillation index calculation unit is used to calculate the control loop oscillation index according to the actual measured value, preset value and control mode of the current control loop;

The control loop relative performance index calculation unit is used to obtain the expected steady state time and the actual steady state time of the control loop, and calculate the relative performance index of the control loop according to the expected steady state time and the actual steady state time of the control loop;

The loop performance evaluation unit is used to evaluate the loop performance according to the deviation standard deviation, the control loop oscillation index and the control loop relative performance index.

Loop performance evaluation unit, including:

a data acquisition sub-unit, used for acquiring the preset value of the deviation standard deviation, the preset value of the control loop oscillation index and the preset interval of the relative performance index of the control loop;

The loop performance evaluation subunit is used to satisfy the requirements that the standard deviation of the deviation is less than the preset value of the standard deviation of the deviation, the oscillation index of the control loop is less than the preset value of the oscillation index of the control loop, and the relative performance index of the control loop is within the preset range of the relative performance index of the control loop. When the current control loop meets the preset performance requirements; otherwise, the current control loop does not meet the preset performance requirements.

The coupling analysis module 203 is used to judge whether the current control loop meets the preset performance requirements according to the performance evaluation result of the current control loop; if it does not meet the preset performance requirements, it is determined according to the coupling relationship table that the current control loop does not meet the preset performance requirements. The source loop is the current control loop or the upstream control loop; the coupling relationship table is a table established by the coupling analysis method to reflect the degree of correlation between the current control loop and the upstream control loop.

The coupling analysis module 203 specifically includes:

The coupling relationship table establishment unit is used to obtain the actual measured values of all upstream control loops in series with the current control loop; according to the actual measured value of each upstream control loop and the actual measured value of the current control loop, the coupling analysis method is used to determine The degree of correlation between each upstream control loop and the current control loop; establish a coupling relationship table according to the degree of correlation.

The coupling analysis module 203 further includes:

The source loop determination unit is used to obtain the preset value of the correlation degree; according to the coupling relationship table, filter out the upstream control loops corresponding to the preset value of the correlation degree, and obtain the set of upstream control loops; the upstream control loops in the set of upstream control loops are two by two Adjacent; number each upstream control loop in the upstream control loop set in the order from downstream to upstream; find out whether there is an upstream control loop adjacent to the current control loop in the upstream control loop set; if not, determine The current control loop is the source loop that causes the current control loop to fail to meet the preset performance requirements; if it exists, the upstream control loop corresponding to the maximum number in the set of upstream control loops is determined as the root cause that causes the current control loop to fail to meet the preset performance requirements loop.

As shown in Figure 3, the control loop performance monitoring system includes six modules: data acquisition, loop overview, loop performance monitoring, coupling analysis, statistical query, and historical data storage.

As shown in Figure 4, the system data processing flow is: loop overview (loop information management) transmits the edited loop information to the loop performance monitoring module and coupling analysis module; the data acquisition module collects data in real time and transmits it to the loop performance monitoring module and the coupling analysis module The coupling analysis module; the loop performance monitoring module and the coupling analysis module transmit the calculation results to the historical data storage module to save the data; the statistical query module reads the data through the historical data storage module for statistical and query operations.

The data acquisition module is used to collect the real-time data required by the loop calculation, mainly the real-time measured value (PV), set value (SV), output value (MV), and MODE mode (manual/automatic) of the loop. Among them, PV, SV, MV, and MODE are provided to the "loop performance monitoring module" for calculating the loop performance, and PV is provided to the "coupling analysis module" for calculating the coupling between loops. The data acquisition module supports OPC communication specification and MODBUS RTU protocol.

The loop overview is mainly used to manage and edit the loop information monitored by the system, including the addition, modification, deletion of single loop information, and editing of PV, SV, MV, and MODE tags (the point number must be the same as the data point on the OPC server). Real-time data can be obtained only if they are consistent with each other); and batch data import of loop information (the file format is CSV).

The loop performance monitoring mainly calculates the control loop performance in real time. By collecting the real-time measured value (PV), set value (SV), output value (MV), and MODE mode (manual/automatic) of a circuit within a period of time. The average deviation value, Deviation standard deviation, actual steady state time, relative performance index and other indicators.

Deviation mean AvgDiff calculation formula:

In the formula, i is the ith sample, t is the total number of samples, SP[i] is the set value of the ith sample, PV[i] is the actual measured value of the ith sample, when Mode is 1, it means automatic, 0 is manual.

Deviation standard deviation StdDiff formula:

In the formula, n is the total number of samples when mode is 1 (automatic), and MODE[i] is the mode of the ith sample.

Relative performance index = ideal steady state time/actual steady state time.

The ideal steady-state time is artificially set based on experience, and the actual steady-state time is statistically derived from the smoothness of the sample data.

Combined with the characteristics of the collected PV, SV, and MODE real-time data in the time domain and frequency domain, the oscillation index is calculated to help understand the loop oscillation.

The Oscillator is calculated as follows:

in,

In the formula, Osc is the oscillation index, n is the total number of samples when the mode is 1 (automatic), the samples calculated here are all the samples when the mode is 1, and x ₁ , x ₂ , y ₁ , y ₂ , and y ₃ are all Intermediate variables.

Finally, the loop is comprehensively evaluated by relative performance index, shock index and standard deviation of deviation, and four grades of excellent, good, medium and poor are obtained.

When the relative performance index is between 0.4 and 2.5, it means that the relative performance index is better, and vice versa.

The smaller the oscillator, the better; the smaller the standard deviation of the deviation, the better.

Comprehensive three indicators, if they are at a good level, the loop performance evaluation is excellent.

If only one indicator is good, or all indicators are poor, the loop performance is evaluated as poor.

The system calculates in a certain period, and saves the calculation results such as deviation mean, deviation standard deviation, actual steady-state time, relative performance index, shock index, and comprehensive evaluation to the data file of the system.

Coupling analysis is to obtain PV data within a certain period of time as a data source through the data acquisition module, and calculate the coupling degree (correlation coefficient) between each loop in a certain period of time. Coupling analysis algorithms, namely correlation analysis, can be used to discover correlations between different variables. Correlation refers to the similarity of changes between data, which can be described by the correlation coefficient. Correlation coefficient is one of the most widely used correlation coefficients, and is mainly used to analyze the degree of coupling of the linear correlation between two continuous variables. The coupling analysis calculation results are saved in the system data file, and the historical coupling degree query function is provided.

Different coupling degrees are distinguished by color in the system, as shown in Table 1.

Table 1 Corresponding relationship between coupling degree and color

Absolute value of coupling color 0.8-1 red 0.5-0.8 orange 0.3-0.5 yellow 0-0.3 no color

Statistical query mainly calculates the average value of a control loop performance index by day, week, month, year, etc., and displays the distribution of grade evaluation within a specified time in the form of a pie chart. Display in the form of a histogram comparison.

Historical data storage is used to store calculation results such as deviation mean, deviation standard deviation, actual steady-state time, relative performance index, shock index, comprehensive evaluation, and loop coupling.

The present invention mainly applies the coupling analysis algorithm to the performance evaluation of the control loop. When the control loop performance is evaluated as poor, the root loop can be accurately found by coupling analysis. Collect real-time measured values (PV) for all the loops that need to be monitored for a period of time. After the collection is completed, the correlation coefficients of the upstream and downstream loops are calculated separately.

In actual operation, the control performance of the current loop needs to be obtained first. If the loop performance is poor, the coupling degree (correlation) between the upstream loop and the current loop can be checked through the coupling analysis module. If the coupling degree is above 0.8 and the upstream loop is The performance evaluation is also poor, and it can be considered that the main reason for the poor performance of the current loop is due to the influence of the upstream loop. And so on, until the last loop with high coupling and poor control performance is found, this loop can be identified as the root loop, and the user can find the cause according to the root loop and formulate a control scheme related to this loop. Table 2 shows the corresponding relationship between coupling degree and correlation, and FIG. 5 is a flow chart of the method for finding the source loop.

Table 2 Correspondence between coupling degree and correlation

Coupling analysis algorithm, namely correlation analysis, is a statistical analysis method. It can be used to find correlations between different variables. Correlation refers to the similarity of changes between data, which can be described by the correlation coefficient. Correlation coefficient is one of the most widely used correlation coefficients. It is mainly used to analyze the degree of linear correlation between two continuous variables. The calculation formula is:

为当前控制回路的PV均值。X_i为上游控制回路的第i个PV样本数值。

为上游控制回路的PV均值。In the formula, n is the total number of samples, and X and Y have n samples respectively. The value of i is 1 to n. Y _i is the i-th PV sample value of the current control loop.

is the PV mean value of the current control loop. Xi is the _ith PV sample value of the upstream control loop.

is the PV mean value of the upstream control loop.

The calculation process is as follows (X and Y represent the PV value of the upstream loop and the PV value of the current loop, respectively): First calculate the average value of the sample data X and Y:

Then calculate the sample data variance temp_X and temp_Y:

Compute the covariance Cov(X, Y) of the sample data X and Y:

Bring into the calculation formula of the correlation coefficient:

Finally, the coupling calculation formula is obtained:

Among them, r is the correlation coefficient, and the value range of the correlation coefficient r is: -1≤r≤1, and its characteristics are as follows:

r>0 means positive correlation, r<0 means negative correlation;

r=0 means that there is no linear relationship;

r=-1 or r=1 means that there is a complete linear relationship.

Indicates that there are different degrees of linear relationship between variables, and the usual convention rules are as follows:

|r|＞0.8: High coupling, it is considered that there is a strong linear relationship;

0.5＜|r|≤0.8: significant linear correlation, it is considered that there is a strong linear correlation, and there is an obvious linear relationship;

0.3＜|r|≤0.5: low degree of linear correlation, it is considered that there is a linear correlation, but the linear correlation is not obvious;

|r|≤0.3: Weak linear correlation or no linear relationship exists.

The invention applies the coupling analysis algorithm to the performance evaluation of the control loop, and assists the user to find out the root loop that causes the poor performance evaluation of a certain loop in the serial loop.

The present invention is specifically described below through three cases:

Case number one

The liquid level of the feed tank of an atmospheric and vacuum unit in an oil refinery is controlled by a cascade loop, the main loop is the tank liquid level, and the secondary loop is the discharge flow. The loop performance monitoring system collects the measured value (PV), set value (SV), output value (MV), MODE mode (manual/automatic) of each loop in real time with a 10-second sampling period. For the main loop, PV is the tank The current liquid level measurement value, SV is the liquid level setting value of the tank, MV is the output of the liquid level circuit, and MODE is the control mode; for the secondary loop, PV is the measured value of the discharge flow, and SV is the set value of the discharge flow. Fixed value, MV is the control valve position of the discharge flow, and MODE is the control mode. The calculation period of the loop performance of the system is 1 hour, and the calculation period of the coupling degree between each loop is 1 hour. In the actual operation process, the evaluation result of the discharge flow control performance is poor, and there is no improvement after adjusting the parameters. Through coupling analysis and calculation, it is found that it is highly coupled with the liquid level circuit. After adjusting the liquid level parameters, the control performance of the discharge flow improves.

Case 2

In a catalytic cracking unit of an oil refinery, the loop performance monitoring system collects the measured value (PV), set value (SV), output value (MV), and MODE mode (manual/automatic) of each control loop in real time with a 10-second sampling period. The feed preheating temperature control loop and the fractionation column top temperature control loop in the device are two separate control loops, and the feed preheat temperature control loop is the upstream loop of the fractionation column top temperature control loop. The PV of the feed preheating temperature control loop is the measured value of the feed temperature, SV is the set value of the feed temperature, MV is the heat exchange three-way valve position, and MODE is the control mode; the PV of the fractionation tower top temperature control loop is The measured value of the tower top temperature, SV is the set value of the tower top temperature, MV is the heat exchange three-way valve position, and MODE is the control mode.

The calculation period of the loop performance of the system is 1 hour, and the calculation period of the coupling degree between each loop is 1 hour. After 1 hour of operation, it was found that the performance diagnosis of the top temperature circuit of the fractionation tower was poor, and the performance diagnosis of the feed preheating temperature circuit was also poor. Due to the large deviation between the measured value of the column top temperature and the temperature set value, the control parameters of the top temperature of the fractionation column were adjusted first, but the control performance was not improved. Through coupling analysis and calculation, the top temperature loop and the feed preheating temperature loop are highly coupled. By adjusting the control parameters of the feed preheating temperature loop, the performance of the feed preheating temperature loop is improved, and the evaluation performance is good, and the performance of the top temperature control loop is also turned to be good.

Case 3

A hydrocracking unit in a refinery is equipped with two rectifying towers connected in series, each with its own pressure control loop. The loop performance monitoring system collects the measured value (PV), set value (SV), output value (MV), and MODE mode (manual/automatic) of each control loop in real time with a sampling period of 10 seconds. The PV of the rectifying tower pressure control loop is the pressure measurement value, the SV is the pressure setting value, the MV is the heat exchange three-way valve position, and the MODE is the control mode.

The calculation period of the loop performance of the system is 1 hour, and the calculation period of the coupling degree between each loop is 1 hour. After 1 hour of operation, it was found that the performance of the pressure control loops of both rectification towers was poor. According to the coupling analysis and calculation, the pressure control loops of the two series-connected rectification towers belong to a low degree of coupling. By adjusting the control parameters of the pressure loop of the upstream rectification tower, the performance of the pressure loop of the upstream rectification tower has been improved and turned to be good. The performance of the downstream distillation column pressure control loop remains poor. After individual adjustment, the performance of the pressure control loop of the downstream distillation column turned to good.

In this paper, specific examples are used to illustrate the principles and implementations of the present invention. The descriptions of the above embodiments are only used to help understand the methods and core ideas of the present invention; meanwhile, for those skilled in the art, according to the present invention There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (4)

1. a control loop performance monitoring method, is characterized in that, comprises: Obtain the actual measured value, preset value and control mode of the current control loop; the control mode includes manual control and automatic control; According to the actual measured value of the current control loop, the preset value and the control mode, a minimum variance control method is used to evaluate the loop performance, and the current control loop performance evaluation result is obtained; Determine whether the current control loop meets the preset performance requirements according to the performance evaluation result of the current control loop; if it does not meet the preset performance requirements, then determine according to the coupling relationship table that the source loop that causes the current control loop to fail to meet the preset performance requirements is: The current control loop is still the upstream control loop; the coupling relationship table is a table established by the coupling analysis method to reflect the correlation degree between the current control loop and the upstream control loop; The performing loop performance evaluation using the minimum variance control method according to the actual measurement value of the current control loop, the preset value and the control mode, specifically includes: according to the actual measurement value of the current control loop and the control mode. Calculate the deviation standard deviation from the preset value of the current control loop; calculate the control loop oscillation index according to the actual measured value of the current control loop, the preset value and the control mode; obtain the expected steady state time and actual steady state of the control loop time, and calculate the relative performance index of the control loop according to the expected steady state time and the actual steady state time of the control loop; according to the standard deviation of the deviation, the oscillation index of the control loop and the relative performance index of the control loop, loop performance evaluation is performed; The method for establishing the coupling relationship table specifically includes: acquiring actual measurement values of all upstream control loops that are serial with the current control loop; value, use the coupling analysis method to determine the degree of correlation between each upstream control loop and the current control loop; establish a coupling relationship table according to the degree of correlation; The determining according to the coupling relationship table whether the source loop that causes the current control loop to fail to meet the preset performance requirements is the current control loop or the upstream control loop specifically includes: acquiring a preset value of the correlation degree; greater than the upstream control loop corresponding to the preset correlation degree value, to obtain a set of upstream control loops; the upstream control loops in the set of upstream control loops are adjacent to each other; for each upstream control loop in the set of upstream control loops Numbering is performed from downstream to upstream; find out whether there is an upstream control loop adjacent to the current control loop in the upstream control loop set; if not, determine that the current control loop is the one that causes the current control loop to not The source loop that meets the preset performance requirement; if there is, the upstream control loop corresponding to the maximum number in the upstream control loop set is determined as the source loop that causes the current control loop to fail to meet the preset performance requirement. 2 . The control loop performance monitoring method according to claim 1 , wherein the evaluating the loop performance according to the standard deviation of the deviation, the control loop oscillation index and the control loop relative performance index specifically includes: 2 . Obtain the preset value of deviation standard deviation, preset value of control loop oscillation index and preset interval of relative performance index of control loop; At the same time, the deviation standard deviation is less than the deviation standard deviation preset value, the control loop oscillatory index is less than the control loop oscillatory index preset value, and the control loop relative performance index in the control loop relative performance index When the index is within the preset interval, the current control loop meets the preset performance requirements; otherwise, the current control loop does not meet the preset performance requirements. 3. A control loop performance monitoring system, comprising: a data acquisition module for acquiring the actual measured value, preset value and control mode of the current control loop; the control mode includes manual control and automatic control; a loop performance monitoring module, configured to perform loop performance evaluation using a minimum variance control method according to the actual measured value of the current control loop, the preset value and the control mode, and obtain the current control loop performance evaluation result; The loop performance monitoring module specifically includes: a deviation standard deviation calculation unit, configured to calculate the deviation standard deviation according to the actual measured value of the current control loop and the preset value of the current control loop; a control loop oscillation index calculation unit, configured to calculate a control loop oscillation index according to the actual measured value of the current control loop, the preset value and the control mode; a control loop relative performance index calculation unit, configured to obtain the expected steady state time and the actual steady state time of the control loop, and calculate the control loop relative performance index according to the control loop expected steady state time and the actual steady state time; a loop performance evaluation unit, configured to evaluate the loop performance according to the standard deviation of the deviation, the control loop oscillation index and the control loop relative performance index; The coupling analysis module is used to judge whether the current control loop meets the preset performance requirements according to the performance evaluation result of the current control loop; if it does not meet the preset performance requirements, it is determined according to the coupling relationship table that the current control loop does not meet the preset performance requirements. Let the source loop of the performance requirement be the current control loop or the upstream control loop; the coupling relationship table is a table established by the coupling analysis method to reflect the degree of correlation between the current control loop and the upstream control loop; The coupling analysis module specifically includes: a coupling relationship table establishment unit for acquiring actual measured values of all upstream control loops in series with the current control loop; according to the actual measured value of each upstream control loop and the For the actual measured value of the current control loop, use the coupling analysis method to determine the degree of correlation between each upstream control loop and the current control loop; establish a coupling relationship table according to the degree of correlation; The coupling analysis module further includes: a source loop determination unit for obtaining a preset value of the correlation degree; according to the coupling relationship table, filtering out the upstream control loop corresponding to the preset value of the correlation degree, and obtaining the upstream control loop Loop set; upstream control loops in the upstream control loop set are adjacent to each other; number each upstream control loop in the upstream control loop set in the order from downstream to upstream; search the upstream control loop set Whether there is an upstream control loop adjacent to the current control loop in the The upstream control loop corresponding to the maximum number in the control loop set is determined as the source loop that causes the current control loop to fail to meet the preset performance requirement. 4. The control loop performance monitoring system according to claim 3, wherein the loop performance evaluation unit specifically comprises: a data acquisition sub-unit, used for acquiring the preset value of the deviation standard deviation, the preset value of the control loop oscillation index and the preset interval of the relative performance index of the control loop; A loop performance evaluation subunit, configured to simultaneously satisfy that the standard deviation of the deviation is less than the preset value of the standard deviation of the deviation, the oscillation index of the control loop is smaller than the preset value of the oscillation index of the control loop, and the relative performance of the control loop is satisfied When the index is within the preset range of the relative performance index of the control loop, the current control loop meets the preset performance requirements; otherwise, the current control loop does not meet the preset performance requirements.

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