A multi-effect evaporator group and its PLC linkage control method

Abstract

The present application relates to the technical field of PLC linkage control, and specifically to a multi-effect evaporator group and its PLC linkage control method, the method comprising: obtaining data of various evaporation parameters in various time periods during the operation of the multi-effect evaporator group to form data sequences of various parameters; obtaining the standard floating stability of the evaporation parameters in each time period, and obtaining the overshoot optimization amount and oscillation effect proximity of the evaporation parameters in each time period; based on this, optimizing the dynamic proportional parameters, dynamic integral parameters and dynamic differential parameters of each evaporation parameter in the next time period; using the optimized dynamic proportional parameters, dynamic integral parameters and dynamic differential parameters to perform PLC linkage control on the multi-effect evaporator group using the PID algorithm. The present application can accurately control the operating state of the multi-effect evaporator.

Description

Technical Field

[0001] The present application relates to the technical field of PLC linkage control, and in particular to a multi-effect evaporator group and a PLC linkage control method thereof. Background Art

[0002] Multiple Effect Evaporator (MEE) is a high-efficiency evaporation equipment that improves energy utilization by connecting multiple evaporators in series. In a multiple-effect evaporator, fresh steam is usually introduced into the first effect, while the subsequent effects use the secondary steam generated by the previous effect as a heating source. In this way, except for the first effect, no additional steam input is required for the subsequent effects, thereby reducing the overall steam demand. In addition, the operating pressure of the multiple-effect evaporator is reduced step by step, and the last effect is usually connected to a vacuum device to achieve cascade utilization of thermal energy and significantly reduce energy consumption. This equipment is widely used in many fields such as seawater desalination, wastewater treatment, food processing and pharmaceutical engineering due to its excellent energy efficiency ratio and low operating cost.

[0003] For the control of multiple-effect evaporators, traditional technologies generally use PLC built-in linkage control to adjust various parameters of the multiple-effect evaporator, including the heating temperature of the evaporator, the height of the liquid in the evaporator, and the temperature of the steam. When these parameters are regulated by PID in the actual production process, since the current effect in the multiple-effect evaporator uses the output liquid and steam of the previous effect as the raw materials of the current effect, when the control unit of the PLC built-in fixed parameter PID is used, the sensitivity of the controller may be low, the system may oscillate, and the response speed of the controller may be low, which will lead to a decrease in the accuracy of the control unit's parameter control when it is running, thereby reducing the operating efficiency and product quality of the multiple-effect evaporator group. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a multi-effect evaporator group and a PLC linkage control method thereof. The technical solutions adopted are as follows:

[0005] The embodiment of the present application provides a PLC linkage control method for a multiple-effect evaporator group, comprising the following steps:

[0006] Obtain the data of various evaporation parameters in various time periods during the operation of the multi-effect evaporator group to form a data sequence of each parameter;

[0007] For each evaporation parameter, the difference between each data in the parameter data sequence of the evaporation parameter and the preset standard value of the evaporation parameter is analyzed to obtain the standard floating stability of the evaporation parameter in each time period; according to the deviation degree of all data in the parameter data sequence of the evaporation parameter and in combination with the standard floating stability, the overshoot optimization amount of the evaporation parameter in each time period is obtained; according to the fluctuation of adjacent extreme value points in the parameter data sequence of the evaporation parameter and the standard floating stability, the adjacency of the oscillation effect of the evaporation parameter in each time period is obtained;

[0008] Analyze the difference in the degree of proximity of the oscillation effect of each evaporation parameter between the current time period and the previous time period, construct the adjustment ratio of each evaporation parameter in the current time period, and optimize the dynamic proportional parameters of each evaporation parameter in the next time period in combination with the overshoot optimization amount of the evaporation parameter in the current time period and the dynamic proportional parameters of each evaporation parameter in the current time period; optimize the dynamic integral parameters of each evaporation parameter in the next time period according to the difference in the degree of proximity of the oscillation effect of each evaporation parameter between the current time period and the previous time period, in combination with the dynamic integral parameters of each evaporation parameter in the current time period; optimize the dynamic differential parameters of each evaporation parameter in the next time period according to the deviation between the extreme value in the parameter data sequence of each evaporation parameter in the current time period and the preset standard value of each evaporation parameter, in combination with the oscillation effect proximity and the dynamic differential parameters of each evaporation parameter in the current time period;

[0009] The PID algorithm is used to perform PLC linkage control on the multi-effect evaporator group through the optimized dynamic proportional parameters, dynamic integral parameters and dynamic differential parameters.

[0010] Preferably, the expression of the standard floating stability of the evaporation parameter in each time period is: ; In the formula, X represents the standard floating stability of the current evaporation parameters in the current time period; represents the ith data in the parameter data sequence of the current evaporation parameter; n represents the number of data in the parameter data sequence; y represents the preset standard value of the current evaporation parameter.

[0011] Preferably, the calculation formula corresponding to the overshoot optimization amount of the evaporation parameter in each time period is: ; In the formula, Hd and X represent the overshoot optimization amount and standard floating stability of the current evaporation parameters in the current time period respectively; The average absolute deviation of all data in the parameter data series representing the current evaporation parameters; Represents the division by zero adjustment factor.

[0012] Preferably, the calculation formula corresponding to the adjacency of the oscillation effect of the evaporation parameter in each time period is: ; In the formula, , X represent the oscillation effect proximity and standard floating stability of the current evaporation parameter in the current time period respectively; They respectively represent the j+1th and jth extreme values ​​in the parameter data sequence of the current evaporation parameter; m represents the number of extreme values ​​in the parameter data sequence.

[0013] Preferably, the corresponding calculation formula for the adjustment ratio of each evaporation parameter in the current time period is:

[0014] ; In the formula, k and Eo represent the adjustment ratio and oscillation effect proximity of the current evaporation parameters in the current time period respectively; It indicates the proximity of the oscillation effect of the current evaporation parameters in the previous time period.

[0015] Preferably, the dynamic proportional parameter corresponding to each evaporation parameter in the next time period is calculated as follows: ; In the formula, DP represents the dynamic proportional parameter of the current evaporation parameter in the next time period; k represents the adjustment ratio of the current evaporation parameter in the current time period; Hd represents the overshoot optimization amount of the current evaporation parameter in the current time period; The dynamic proportional parameter represents the current evaporation parameter in the current time period, wherein the dynamic proportional parameter of the current evaporation parameter at the initial moment is the first preset value.

[0016] Preferably, the dynamic integral parameter corresponding to the evaporation parameter in the next time period is calculated as follows: ; In the formula, DI represents the dynamic integral parameter of the current evaporation parameter in the next time period; They represent the oscillation effect adjacency of the current evaporation parameter in the current time period and its previous time period respectively; Represents the dynamic integral parameter of the current evaporation parameter in the current time period; wherein, the dynamic integral parameter of the current evaporation parameter at the initial moment is the second preset value; sig() is the sigmoid function.

[0017] Preferably, the dynamic differential parameter of each evaporation parameter in the next time period should be calculated as follows:

[0018] ; In the formula, DD represents the dynamic differential parameter of the current evaporation parameter in the next time period; Respectively represent the overshoot reflection degree of the current evaporation parameter in the current time period and the previous time period, wherein the overshoot reflection degree is obtained according to the deviation between the extreme value in the parameter data sequence of each evaporation parameter and the preset standard value of each evaporation parameter, and the oscillation effect proximity; It represents the dynamic differential parameter of the current evaporation parameter in the current time period, and the dynamic differential parameter of each evaporation parameter at the initial moment is the third preset value.

[0019] Preferably, the overshoot reflection degree corresponding calculation formula is:

[0020] , G represents the overshoot value of the current evaporation parameter in the current time period; It represents the degree of proximity of the oscillation effect of the current evaporation parameter in the current time period; wherein, the absolute value of the difference between each extreme value in the parameter data sequence corresponding to each evaporation parameter in the current time period and the preset standard value of each evaporation parameter is analyzed, and the absolute value of the difference corresponding to all the extreme values ​​of each evaporation parameter is accumulated as the overshoot value of each evaporation parameter in the current time period.

[0021] An embodiment of the present application further provides a multiple-effect evaporator group, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0022] From the above, it can be seen that the multi-effect evaporator group and the PLC linkage control method thereof provided by the present application have at least the following beneficial effects:

[0023] The present application takes into account that the control method of the multiple-effect evaporator in the prior art often has the characteristics of nonlinearity, large inertia, hysteresis, etc., which makes it impossible to effectively improve the evaporation efficiency and stability, making it difficult to ensure the operation efficiency and product quality of the multiple-effect evaporator. Therefore, based on the real-time collected operation data of the multiple-effect evaporator, the present invention characterizes the optimal operation characteristics of the multiple-effect evaporator under different working conditions by taking advantage of the difference between the parameters of the control unit and the preset standard value, as well as the floating of the parameters in the control unit, the overshoot optimization amount of the oscillation state construction parameters, the proximity of the oscillation effect, etc., and constructs a dynamic PID parameter adjustment strategy based on this; further, the PLC linkage control system is used to accurately control the operation state of the multiple-effect evaporator through dynamic PID parameters for different effects and different parameters. Therefore, the present invention avoids the problems of low sensitivity, low response speed and oscillation of the controller caused by the output of the parameters of the current effect being the input of the parameters of the next effect in the control method of the multiple-effect evaporator in the prior art, and can effectively improve the operation efficiency and product quality of the multiple-effect evaporator, making the control of the multiple-effect evaporator more accurate and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1A flow chart of the steps of a PLC linkage control method for a multi-effect evaporator group provided in this application;

[0026] Figure 2 Schematic diagram of extreme value detection of parameter data sequence provided for this application;

[0027] Figure 3 Schematic diagram of the control effect of fixed PID control and dynamic PID control of steam parameters provided in this application. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of a multi-effect evaporator group and its PLC linkage control method proposed in the present application, its specific implementation method, structure, features and effects in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0029] Unless otherwise specified and limited, terms such as "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a circuit structure, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such articles or devices. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the article or device including the element. In addition, the term "and\or" used herein includes any and all combinations of one or more related listed items. All technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application.

[0030] The specific scheme of a multi-effect evaporator group and its PLC linkage control method provided by the present application is described in detail below with reference to the accompanying drawings.

[0031] See also Figure 1 , which shows a step flow chart of a PLC linkage control method for a multi-effect evaporator group provided by an embodiment of the present application, including the following steps:

[0032] Step 1: Obtain the data of various evaporation parameters in various time periods during the operation of the multi-effect evaporator group to form data sequences of various parameters.

[0033] The purpose of this embodiment is to accurately control various parameters of the multiple-effect evaporator through PLC linkage, avoid the reduction of the evaporation efficiency of the multiple-effect evaporator due to different initial parameters of different evaporators and different data fluctuations, and effectively reduce the nonlinearity, large inertia and hysteresis characteristics of various parameters in the control process, thereby effectively improving the evaporation efficiency of the multiple-effect evaporator.

[0034] The working principle of multiple-effect evaporation is that the solution first enters the system and is preheated by the preheater. The preheated solution enters the first evaporator, where it is heated and begins to evaporate. The steam produced is called secondary steam. The secondary steam produced in the first effect is used as the heating medium for the second effect, and the secondary steam in the second effect is used as the heating medium for the third effect, and so on. After evaporation, the solution in each effect is transported to the next effect, and continues to be heated and evaporated until the required concentration is reached. The steam produced in the last effect is introduced into the condenser, cooled with water, condensed into water and removed.

[0035] For each evaporator in the multiple-effect evaporator, the liquid level height of the liquid in the evaporator is collected by using a liquid level sensor, the vacuum pressure of the evaporator is collected by connecting the pressure sensor to the vacuum device, and the temperature sensor is installed on the secondary steam pipeline to collect the temperature of the secondary steam. The frequency of collection is 10Hz, and the length of each collection time period is 3min. The collected various parameter data are arranged in the order of collection, and the arranged data are denoised by median filtering to reduce the distortion of the data caused by the influence of the environment. After denoising, all data of each evaporation parameter in each time period constitute the parameter data sequence corresponding to each evaporation parameter in each time period. It should be noted that for each evaporation parameter, all denoised data of the evaporation parameter in each time period constitute each parameter data sequence of the evaporation parameter, that is, the evaporation parameter will correspond to a parameter data sequence in one time period.

[0036] At this point, a parameter data sequence can be obtained for each evaporation parameter in each time period.

[0037] Step 2: for each evaporation parameter, analyze the difference between each data in the parameter data sequence of the evaporation parameter and the preset standard value of the evaporation parameter to obtain the standard floating stability of the evaporation parameter in each time period; according to the deviation degree of all data in the parameter data sequence of the evaporation parameter and in combination with the standard floating stability, obtain the overshoot optimization amount of the evaporation parameter in each time period; according to the fluctuation of adjacent extreme value points in the parameter data sequence of the evaporation parameter and the standard floating stability, obtain the adjacency of the oscillation effect of the evaporation parameter in each time period.

[0038] For various parameters of the evaporator, in order to ensure the best evaporation efficiency of the multi-effect evaporator, the various parameters of the evaporator are usually kept within a numerical value with slight fluctuations. However, since each effect of the multi-effect evaporation will utilize the liquid and steam provided by the previous effect, it should be noted that, except for the first effect, the liquid of the first effect is the initial liquid, and the steam is also the initial steam. Since the speed of liquid entering the evaporation process is different, the guaranteed vacuum pressure of each evaporator is also different, and the temperature of the steam is also different, resulting in different times for the liquid to reach the height of the liquid standard line during the evaporation process in the evaporator. During the evaporation process, the total heat compensated by the evaporator heater to the steam is different, which may cause the liquid to crystallize prematurely or evaporate incompletely, resulting in problems with the product. Therefore, various parameters need to be adjusted for the evaporation process of the evaporator.

[0039] Taking the parameter data sequence of any evaporator parameter as an example, the adjustment and control process of the evaporation parameter is described in detail. In this embodiment, the vacuum pressure of the evaporator is taken as an example. For the convenience of understanding and expression, it is recorded as the current evaporation parameter. Under normal circumstances, a standard value will be set for the evaporation parameter during the control process of the control unit of the evaporator. For example, the preset standard value of the first effect pressure parameter of the multi-effect evaporator used in this embodiment is 1.1MPa. If the data value collected by the sensor is closer to the standard value of the evaporation parameter, it means that the influence of this evaporation parameter on the operating efficiency of the evaporator is smaller. Since in the actual production process, the actual parameter value fluctuates above and below the standard value, the closer the upward and downward floating amounts of the parameter are, the more stable the evaporation parameter is under the control of PID, and the standard floating stability of the evaporation parameter is calculated.

[0040] ; In the formula, X represents the standard floating stability of the current evaporation parameters in the current time period; Represents the i-th data in the parameter data sequence of the current evaporation parameter; n represents the number of data in the parameter data sequence; y represents the preset standard value of the current evaporation parameter, for example: in this embodiment, the preset standard value of the steam temperature is 95°C, and the specific preset standard value of each evaporation parameter is set by the implementer according to the actual situation in the actual application scenario; exp() represents an exponential function with a natural constant as the base; || represents an absolute value function.

[0041] For the adjustment of evaporation parameters during normal operation of a multiple-effect evaporator, the closer the adjusted evaporation parameters are to the standard values, i.e. The smaller the absolute value, the better the adjustment. In addition, during the adjustment of the evaporation parameters of the evaporator, the actual evaporation parameters fluctuate around the standard values. Therefore, the difference between the adjusted evaporation parameters and the standard values ​​of the evaporation parameters is There are positive values ​​and negative values. When the difference between the positive and negative values ​​is smaller, that is, The smaller the value, the higher the data stability. Therefore, the negative exponential function is used to process the data to ensure that the stability of the evaporation parameters is higher, and the larger the value of the standard floating stability X of the evaporation parameters.

[0042] When adjusting the evaporation parameters of the multiple-effect evaporator, the larger the standard floating stability X of the evaporation parameters, the higher the stability of the control unit of the evaporation parameters. However, if the volatility of the evaporation parameters is too large, that is, the floating range of the evaporation parameters around the standard value is wide, this may mean that there is a serious overshoot phenomenon in the control unit. Overshoot not only affects product quality, but may also cause energy waste and equipment loss. At this time, the control unit should suppress the oscillation of the evaporation parameters and reduce the overshoot phenomenon of the evaporation parameters. Thus, the overshoot optimization amount of each evaporation parameter is calculated.

[0043] ; In the formula, Hd represents the overshoot optimization amount of the current evaporation parameter in the current time period; X represents the standard floating stability of the current evaporation parameter in the current time period; The average absolute deviation of all data in the parameter data series representing the current evaporation parameters; represents the zero division adjustment factor, and in this embodiment, the value is 0.01. The calculation of the mean absolute deviation is a well-known technique, and the specific calculation process is not repeated here.

[0044] The larger the value of the standard floating stability X of the evaporation parameter in the current time period, the more effectively the control and adjustment of the evaporation parameter in the current time period can maintain the evaporation parameter close to its preset standard value, and the better the stability of the evaporation parameter change, the stronger the oscillation of the evaporation parameter is. The larger the value is, the more the overshoot oscillation phenomenon of the evaporation parameter should be suppressed, that is, the smaller the value of the overshoot optimization amount Hd of the evaporation parameter is, so as to ensure the stability of the evaporator group during the adjustment process and ensure rapid response without excessive fluctuations.

[0045] In the process of regulating the evaporation parameters of the multi-effect evaporator, when the evaporation parameters are not affected by the outside world, the evaporation parameters are constantly converging near the preset standard values, and the fluctuation characteristics of the evaporation parameter data are getting smaller and smaller. Therefore, the control unit performs the evaporation parameter adjustment process, and the overshoot phenomenon of the evaporation parameters is getting smaller and smaller. However, when the system is affected by external factors, resulting in increased vibration of the evaporation parameters, the control unit needs to suppress the vibration phenomenon.

[0046] Based on the above analysis, according to the fluctuation of adjacent extreme value points in the parameter data sequence of the evaporation parameter, combined with the standard floating stability of the evaporation parameter in each time period, the oscillation effect adjacency of the evaporation parameter in each time period is obtained. In this embodiment, the calculation formula of the oscillation effect adjacency of each evaporation parameter in each time period is:

[0047] ; In the formula, It indicates the proximity of the oscillation effect of the current evaporation parameter in the current time period; X indicates the standard floating stability of the current evaporation parameter in the current time period; Respectively represent the j+1th and jth extreme values ​​in the parameter data sequence of the current evaporation parameter; m represents the number of extreme values ​​in the parameter data sequence. In this embodiment, the parameter data sequence of each evaporation parameter is used as the input of the extreme value detection algorithm, and the extreme value of the parameter data sequence of each evaporation parameter is output. It should be noted that the process of obtaining the extreme value points of the sequence is an existing well-known technology and will not be elaborated in detail in this embodiment. Specifically, the schematic diagram of the extreme value detection of the parameter data sequence is as follows: Figure 2 As shown, Figure 2 In the figure, the horizontal axis is the parameter value of the current steam parameter, and the vertical axis is time. Figure 2 The middle dotted line is the preset standard value of the current steam parameter, and the circles are the extreme points. Figure 2 The middle curve is the parameter, that is, the waveform distribution of the current steam parameters.

[0048] Since the purpose of evaporation parameter control is to control the working parameters of the evaporator to fluctuate slightly above and below the preset standard values, the greater the standard floating stability of the evaporation parameters and the smaller the oscillation effect of the evaporation parameters, that is, The smaller the value is, the smaller the oscillation effect of the evaporation parameter is during the adjustment of the evaporation parameter, which makes the oscillation effect proximity degree Eo of the evaporation parameter in the current time period smaller.

[0049] Step three: Analyze the difference in the degree of proximity of the oscillation effect of each evaporation parameter between the current time period and the previous time period, construct the adjustment ratio of each evaporation parameter in the current time period, and optimize the dynamic proportional parameters of each evaporation parameter in the next time period in combination with the overshoot optimization amount of the evaporation parameter in the current time period and the dynamic proportional parameters of each evaporation parameter in the current time period; optimize the dynamic integral parameters of each evaporation parameter in the next time period according to the difference in the degree of proximity of the oscillation effect of each evaporation parameter between the current time period and the previous time period, combined with the dynamic integral parameters of each evaporation parameter in the current time period; optimize the dynamic differential parameters of each evaporation parameter in the next time period according to the deviation between the extreme value in the parameter data sequence of each evaporation parameter in the current time period and the preset standard value of each evaporation parameter, combined with the oscillation effect proximity and the dynamic differential parameters of each evaporation parameter in the current time period.

[0050] Based on the analysis of the above steps, when the oscillation effect of the evaporation parameters in the previous time period is much greater than the oscillation effect of the evaporation parameters in the current time period, it means that the control unit has a higher control ability for the adjustment of the evaporation parameters. The control unit can more effectively control the fluctuation of the evaporation parameters, making it more stably fluctuate slightly around the preset standard value, thereby increasing production efficiency and production quality.

[0051] In the production process of multiple-effect evaporators, PLC linkage control systems are usually used to control different positions and different types of evaporation parameters of the evaporator. In the PLC control system, PID control units are generally used to regulate various evaporation parameters. For the same evaporation parameter of the multiple-effect evaporator, when the linkage control is performed through PLC, since the output of the current effect of the multiple-effect evaporator is the input of the next effect, the PLC linkage control in the control of the multiple-effect evaporator adopts a series-parallel linkage control, that is, the same evaporation parameter of different effects in the multiple-effect evaporator is executed in series, and the different evaporation parameters of the same effect are executed in parallel.

[0052] In the process of using PID algorithm to adjust and control the evaporation parameters, the proportional parameter P of the PID control algorithm is used to control the response of the system, which affects the dynamic performance of the control system. Therefore, based on the above analysis, this embodiment will adjust the dynamic proportional parameter in the PID control process and calculate the dynamic proportional parameter DP of the parameter in the control unit. The specific process is as follows:

[0053] First, the difference in the proximity of the oscillation effect of each evaporation parameter between the current time period and the previous time period is analyzed, and the adjustment ratio of each evaporation parameter in the current time period is constructed. In this embodiment, the expression of the adjustment ratio is:

[0054] ; In the formula, k represents the adjustment ratio of the current evaporation parameter in the current time period; Indicates the oscillation effect adjacency of the current evaporation parameter in the current time period; It indicates the proximity of the oscillation effect of the current evaporation parameters in the previous time period.

[0055] Further, based on the adjustment ratio of each evaporation parameter in the current time period and the overshoot optimization amount, combined with the dynamic proportional parameter of the current time period, the dynamic proportional parameter of each evaporation parameter in the next time period is optimized, and the expression of the dynamic proportional parameter of each evaporation parameter in the next time period after optimization is:

[0056] ; In the formula, DP represents the dynamic proportional parameter of the current evaporation parameter in the next time period; Hd represents the overshoot optimization amount of the current evaporation parameter in the current time period; It represents the dynamic proportional parameter of the current evaporation parameter in the current time period. It should be noted that the dynamic proportional parameter of the current evaporation parameter at the initial moment is the first preset value, that is, the dynamic proportional parameter corresponding to each evaporation parameter in the first time period is the preset value. In this embodiment, the dynamic proportional parameter of each evaporation parameter at the initial moment, that is, the first preset value, is 13. In actual application scenarios, the implementer can set it by himself.

[0057] If the oscillation effect of the parameters in the current time period is greater than that in the previous time period, it means that the overshoot phenomenon of the parameters in the control unit is more serious. For the parameters of the control unit, the dynamic proportional parameter DP of the next time period should be reduced, that is, the adjustment ratio The value of is negative and the smaller the value is, the overshoot of the control unit parameters can be reduced, so that the control unit parameters converge to the preset standard value faster. If the oscillation effect of the parameters in the current time period is smaller than the oscillation effect of the previous time period, it means that the convergence characteristics of the parameters in the control unit are better, and the greater the difference between the two oscillation effects, the better the convergence characteristics. Therefore, the adjustment ratio that needs to be adjusted is The larger the value of , the smaller the change of the dynamic proportional parameter in the next time period, thus ensuring the convergence characteristics of the system.

[0058] Furthermore, for the static error of the adjustment parameter in the PID control unit, the integral parameter I of the PID algorithm is used to eliminate the static error. When the static error of the control unit is larger, the value of the integral parameter is larger. The static error is manifested as the difference between the parameter in the control unit and the preset standard value, and is manifested as the difference between the oscillation effect proximity of the current time period and the oscillation effect proximity of the previous time period. Therefore, according to the difference in the oscillation effect proximity of each evaporation parameter in the current time period and the previous time period, combined with the dynamic integral parameters of each evaporation parameter in the current time period, the dynamic integral parameters of each evaporation parameter in the next time period are optimized, and the dynamic integral parameter DI of the next time period is calculated. The expression in this embodiment is:

[0059] ; In the formula, DI represents the dynamic integral parameter of the current evaporation parameter in the next time period; Indicates the oscillation effect adjacency of the current evaporation parameter in the current time period; It indicates the adjacency of the oscillation effect of the current evaporation parameter in the previous time period; It represents the dynamic integral parameter of the current evaporation parameter in the current time period; it should be noted that the dynamic integral parameter of the current evaporation parameter at the initial moment is the second preset value. In this embodiment, the second preset value is 3.5; sig() represents the sigmoid function.

[0060] If the oscillation effect proximity of the evaporation parameter in the current time period is less than that in the previous time period, it means that the static error of the evaporation parameter in the current time period is less than that in the previous time period. Therefore, the dynamic integral parameter of the evaporation parameter in the current time period should be reduced as the dynamic integral parameter of the next time period.

[0061] Furthermore, considering the overshoot phenomenon of parameters in the control process, the differential parameters of the PID algorithm are used for adjustment. The more serious the overshoot phenomenon is, the larger the differential parameter is used, so that the parameters in the control process can converge to the preset standard value faster.

[0062] Therefore, for the differential parameters of the PID algorithm, this embodiment will analyze the parameter values ​​of each evaporation parameter in each time period to analyze the overshoot of each evaporation parameter, and then adaptively optimize the differential parameters of the PID algorithm. Specifically, for each extreme value in the parameter data sequence corresponding to each evaporation parameter in the current time period, the deviation of each extreme value from the preset standard value of the evaporation parameter is analyzed. In this embodiment, the absolute value of the difference between each extreme value and the preset standard value of the evaporation parameter is calculated, and all absolute values ​​are summed as the overshoot value of the corresponding evaporation parameter in the current time period.

[0063] Further, in this embodiment, according to the deviation between the extreme value in the parameter data sequence of each evaporation parameter in the current time period and the preset standard value of each evaporation parameter, combined with the dynamic differential parameter of each evaporation parameter in the current time period, the dynamic differential parameter of each evaporation parameter in the next time period is optimized, and the dynamic differential parameter of the next time period is calculated. The specific expression in this embodiment is:

[0064] ; In the formula, DD represents the dynamic differential parameter of the current evaporation parameter in the next time period; Respectively represent the overshoot reflection degree of the current evaporation parameter in the current time period and the previous time period; represents the dynamic differential parameter of the current evaporation parameter in the current time period, and the dynamic differential parameter of each evaporation parameter at the initial moment is a third preset value. In this embodiment, the dynamic differential parameter of each evaporation parameter at the initial moment is 5. , G represents the overshoot value of the current evaporation parameter in the current time period; Indicates the proximity of the oscillation effect of the current evaporation parameter in the current time period.

[0065] It should be noted that, the next time period is a time period next to the current time period, and the previous time period is a time period previous to the current time period.

[0066] When the overshoot of the evaporation parameter in the current time period is less than the overshoot of the previous time period, that is, The value of is less than 1, indicating that the stability of the control process is increasing. To ensure the stability of the system, the differential parameter is reduced, that is, value to increase the stability of the system.

[0067] Step 4: Use the PID algorithm to perform PLC linkage control on the multi-effect evaporator group through the optimized dynamic proportional parameters, dynamic integral parameters, and dynamic differential parameters.

[0068] Through the above steps, for each evaporation parameter of the same evaporator in the PLC linkage control, a dynamic proportional parameter, a dynamic integral parameter and a dynamic differential parameter are calculated, the dynamic proportional parameter, dynamic integral parameter and dynamic differential parameter of each evaporation parameter correspond to a control unit, the dynamic proportional parameter, dynamic integral parameter, dynamic differential parameter of the control unit corresponding to each evaporation parameter and the parameter data sequence of each evaporation parameter in the current time period are used as feedback, and the PID controller is used to control the evaporation parameters of the multi-effect evaporator.

[0069] Repeat the above process to realize PLC linkage control to complete the PLC linkage control process of the multi-effect evaporator group. It should be noted that the process of using a PID controller in combination with a dynamic integral parameter, a dynamic differential parameter and a dynamic proportional parameter for control is a prior art and will not be described in detail in this embodiment.

[0070] The control effect diagram of fixed PID control (i.e., using fixed values ​​for the proportional parameter, integral parameter, and differential parameter in the PID control process) and dynamic PID control (i.e., using the dynamic proportional parameter, dynamic integral parameter, and dynamic differential parameter obtained by the method and process of this embodiment for control) is shown in the figure. Figure 3 As shown, Figure 3 In the figure, the vertical axis is the parameter value of the current steam parameter, and the horizontal axis is time. Figure 3 The black solid line in the middle is the curve corresponding to dynamic PID control, and the gray dotted line is the curve corresponding to fixed PID control.

[0071] Based on the same inventive concept as the above method, an embodiment of the present application also provides a multiple-effect evaporator group, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned PLC linkage control methods for a multiple-effect evaporator group are implemented.

[0072] It is to be understood that the sequence of the embodiments of the present application described above is for description only and does not represent the advantages and disadvantages of the embodiments. The above describes specific embodiments of the present specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0073] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0074] The above content is only an implementation method of the present application and is not intended to limit the scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the protection scope of the present application.

Claims

1. A PLC linkage control method for a multiple-effect evaporator group, characterized in that: The following steps are involved: Obtain the data of various evaporation parameters in various time periods during the operation of the multi-effect evaporator group to form a data sequence of each parameter; The opposite number of the absolute value of the mean of the difference between all data in the parameter data sequence of the current evaporation parameter and the preset standard value of the current evaporation parameter is used as the exponent, and the value of the exponential function with the natural constant as the base is recorded as the standard floating stability of the current evaporation parameter in the current time period; Calculate the sum of the average absolute deviation of all data in the parameter data sequence of the current evaporation parameter and the preset zero division adjustment factor, and use the ratio of the standard floating stability of the current evaporation parameter in the current time period to the sum as the overshoot optimization amount of the current evaporation parameter in the current time period; calculate the cumulative sum of the absolute values ​​of the differences between adjacent extreme values ​​in the parameter data sequence of the current evaporation parameter, and record the ratio of the cumulative sum to the standard floating stability as the oscillation effect adjacency of the current evaporation parameter in the current time period; The difference in the degree of proximity of the oscillation effect of each evaporation parameter between the current time period and the previous time period is analyzed to construct the adjustment ratio of each evaporation parameter in the current time period. Combined with the overshoot optimization amount of the evaporation parameter in the current time period and the dynamic proportional parameters of each evaporation parameter in the current time period, the dynamic proportional parameters of each evaporation parameter in the next time period are optimized. The corresponding calculation formula for the dynamic proportional parameters of each evaporation parameter in the next time period is: ; In the formula, DP represents the dynamic proportional parameter of the current evaporation parameter in the next time period; k represents the adjustment ratio of the current evaporation parameter in the current time period; Hd represents the overshoot optimization amount of the current evaporation parameter in the current time period; It represents the dynamic proportional parameter of the current evaporation parameter in the current time period, wherein the dynamic proportional parameter of the current evaporation parameter at the initial moment is the first preset value; according to the difference in the proximity of the oscillation effect of each evaporation parameter in the current time period and the previous time period, combined with the dynamic integral parameters of each evaporation parameter in the current time period, the dynamic integral parameters of each evaporation parameter in the next time period are optimized, and the corresponding calculation formula of the dynamic integral parameters of each evaporation parameter in the next time period is: ; In the formula, DI represents the dynamic integral parameter of the current evaporation parameter in the next time period; They represent the oscillation effect adjacency of the current evaporation parameter in the current time period and its previous time period respectively; represents the dynamic integral parameter of the current evaporation parameter in the current time period; wherein, the dynamic integral parameter of the current evaporation parameter at the initial moment is the second preset value; sig() is the sigmoid function; according to the deviation between the extreme value in the parameter data sequence of each evaporation parameter in the current time period and the preset standard value of each evaporation parameter, combined with the oscillation effect proximity and the dynamic differential parameter of each evaporation parameter in the current time period, the dynamic differential parameter of each evaporation parameter in the next time period is optimized, and the corresponding calculation formula of the dynamic differential parameter of each evaporation parameter in the next time period is: ; In the formula, DD represents the dynamic differential parameter of the current evaporation parameter in the next time period; Respectively represent the overshoot reflection degree of the current evaporation parameter in the current time period and the previous time period, wherein the overshoot reflection degree is obtained according to the deviation between the extreme value in the parameter data sequence of each evaporation parameter and the preset standard value of each evaporation parameter, and the oscillation effect proximity; Indicates the dynamic differential parameter of the current evaporation parameter in the current time period, and the dynamic differential parameter of each evaporation parameter at the initial moment is a third preset value; The PID algorithm is used to perform PLC linkage control on the multi-effect evaporator group through the optimized dynamic proportional parameters, dynamic integral parameters and dynamic differential parameters.

2. A PLC linkage control method for a multiple-effect evaporator group as claimed in claim 1, characterized in that: The corresponding calculation formula for the adjustment ratio of each evaporation parameter in the current time period is: ; In the formula, k and Eo represent the adjustment ratio and oscillation effect proximity of the current evaporation parameters in the current time period respectively; It indicates the proximity of the oscillation effect of the current evaporation parameters in the previous time period.

3. A PLC linkage control method for a multiple-effect evaporator group as claimed in claim 1, characterized in that: The corresponding calculation formula of the overshoot reflection degree is: , G represents the overshoot value of the current evaporation parameter in the current time period; It represents the degree of proximity of the oscillation effect of the current evaporation parameter in the current time period; wherein, the absolute value of the difference between each extreme value in the parameter data sequence corresponding to each evaporation parameter in the current time period and the preset standard value of each evaporation parameter is analyzed, and the absolute value of the difference corresponding to all the extreme values ​​of each evaporation parameter is accumulated as the overshoot value of each evaporation parameter in the current time period.

4. A multiple-effect evaporator group, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 3 are implemented.

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