JP2016206793A - Integrated system process dynamics automatic identification device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To identify dynamics of a process by finding out data approximate to a step response test from the past operation data of the process represented by the transfer function including an integration element.SOLUTION: A change amount ΔMV of an input value every time is calculated from the input actual data determining the relationship between the time and the input value of a predetermined interval among data of some periods extracted from past input and output actual data of a process, and such a determination is made that the input actual data is a step input when the change width of the input value in a predetermined time range just before a time Mt when the maximum ΔMV is obtained and a predetermined time range just after that is equal to or less than a permissible change width smaller than the maximum ΔMV. When determined to be the step input, the period output change amount changing in the transition period is acquired from the output actual data, and parameters of a transfer function are calculated.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an integral system process dynamic characteristic automatic identification device for identifying a dynamic characteristic of a process represented by a transfer function including an integral element.

  In recent years, in process control, optimization of control performance has been pursued from various viewpoints such as cost reduction, production efficiency, and environmental load reduction. As a method for realizing optimal process control, a new control algorithm IMC (internal model controller) and MD-PID (model drive PID) for optimizing PID parameter tuning are attracting attention.

  In order to control a process correctly, it is necessary to have correct knowledge about the dynamic characteristics of the process. Therefore, the problem of estimating process dynamics is an important field in automatic control. The dynamic characteristics of a process refers to the relationship between input and output to / from the process, that is, the relationship between two variables that change with time. In order to examine this characteristic, a step input that changes stepwise as an input is added to the process, and an output, that is, a step response is obtained.

JP 2001-255932 A

  In the past, determining the dynamic characteristics of a process has relied on a specialist in the control system, and conducted a step response test in the field. In the step response test, an operation value MV (Manipulate Value) that is an input value is changed, a change in a response value PV (Process Value) that is an output value is measured, and a transfer function parameter (gain) that expresses the dynamic characteristics of the process. K, dead time L, time constant T).

  Further, the operation state of the plant is not unchanged, and the dynamic characteristics of the process change with time. In order to keep the plant control optimal, it is necessary to perform step response tests frequently.

However, acquisition of step response data and determination of process dynamics have the following problems.
From an operational point of view,
(1) Since the step response test affects the operation of the plant, it is difficult to perform the test frequently.
(2) In a process control system with a long dead time and settling time (time until the output reaches within the allowable error range of the steady value), it takes time to obtain response data, which affects the operation of the plant.
(3) In many cases, the step response test cannot be performed due to the problem of safe operation of the plant.
From a human point of view,
(4) It is not realistic to capture data that a human visually approximates to a step response from past driving data of 24-hour continuous operation.
(5) When determining the parameters (process constants) from the response data of the step response test, the accuracy varies depending on the individual skill.

  The present invention has been made in order to solve the above-described problems, and it is possible to search for data that approximates a step response test from past operation data of a process, and to identify the dynamic characteristics of the process. An object is to provide an automatic characteristic identification apparatus.

  In order to achieve the above object, an integrated system process dynamic characteristic automatic identification device according to the present invention is configured as follows.

  An integrated system process dynamic characteristic automatic identification device according to the present invention is configured to identify a dynamic characteristic of a process represented by a transfer function including an integral element.

  An integrated system process dynamic characteristic automatic identification apparatus according to the present invention includes a step input determination means, a step response acquisition means, and a dynamic characteristic automatic calculation means.

  The step input determination means is configured to calculate the input value for each time from the input actual data that defines the relationship between the time at the predetermined interval and the input value out of the partial period data extracted from the past input / output actual data of the process. A change amount ΔMV is calculated. Further, the step input determination means has an allowable change width in which the change width of the input value in the predetermined time range immediately before and after the time Mt at which the maximum input change amount ΔMVmax is obtained is smaller than the maximum input change amount ΔMVmax. In the case of the following, the actual input data is determined as the step input.

  Preferably, when the input actual data is not determined to be step input by the step input determining means, data of a partial period different from the above-described partial period data is extracted from past input / output actual data, and step input is performed again. The determination unit is executed.

  Preferably, the above-described allowable change width is set to a predetermined width between 20% and 40% of the maximum input value in the input actual data.

  The step response obtaining means obtains the output value for each time from the output actual data that defines the relationship between the time at the predetermined interval and the output value among the data of the partial period when the input actual data is determined as the step input. A change amount ΔPV is calculated. Further, the step response acquisition means includes a transient period Δt that is a period immediately before and immediately after the time when the maximum output change amount ΔPVmax is obtained and in which the change amount ΔPV is equal to or greater than a reference amount smaller than the maximum output change amount ΔPVmax, A period output change amount ΔPV (V) that has changed during the period Δt is acquired.

  Preferably, the above-described reference amount is set to a predetermined amount between one-quarter or more and half or less of the maximum output change amount ΔPVmax.

  The dynamic characteristic automatic calculation means calculates transfer function parameters based on the maximum input change amount ΔMVmax, the period output change amount ΔPV (V), the transient period Δt, the start time Pt of the transient period Δt, and the time Mt.

  Preferably, the transfer function is represented by the following transfer function G (s) including gain K, dead time L, and integration time T as parameters, where gain K is K = ΔPV (V) / ΔMVmax, wasted Time L is L = Pt−Mt, and integration time T is T = ΔPV (V) / Δt.

  According to the integrated system process dynamic characteristic automatic identification device according to the present invention, the actual input data and the actual output data that approximate the step response test are searched from the past operation data of the process, and the dynamic characteristic of the process is automatically identified. Can do. Since the dynamic characteristics of the process can be automatically identified using past operation data stored sequentially, it is not necessary to perform a step response test.

It is a figure for demonstrating the processing flow of the integral system process dynamic characteristic identification apparatus which concerns on Embodiment 1 of this invention. It is a figure for demonstrating an example of operation | movement of the step signal search filter 3 which concerns on Embodiment 1 of this invention. It is a figure for demonstrating an example of operation | movement of the response signal search filter 4 which concerns on Embodiment 1 of this invention. It is an example of the standardized input / output actual data regarding the step signal search filter 3 and the response signal search filter 4.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
Although the plant and process which concern on this Embodiment are not limited, as one specific example, a plant is a thermal power plant. The process is a thermal power plant boiler, the process input is the coal flow rate, and the process output is the main steam pressure.

  In the following description, the dynamic characteristics of the process are expressed by a transfer function G (s) including an integral element shown in Expression (1). Here, K is a gain, L is a dead time, and T is an integration time.

  FIG. 1 is a diagram for explaining the processing flow of the integral system process dynamic characteristic identification device according to Embodiment 1 of the present invention.

  The integration system process dynamic characteristic identification device includes, for example, a memory including a ROM, a RAM, an input / output interface for inputting / outputting various information, and a processor for executing various arithmetic processes based on the various information and a program stored in the memory. . As shown in FIG. 1, the integral system process dynamic characteristic identification apparatus mainly has six processing units (operation data input unit 1, data standardization processing unit 2, step signal search filter 3, response signal search filter 4, dynamic characteristic automatic calculation. Part 5 and dynamic characteristic determination part 6). The memory stores a program corresponding to each processing unit in advance, and each processing unit is realized by the processor reading and executing the program. Hereinafter, each processing unit will be described.

(Operation data input part)
The operation data input unit 1 inputs past operation data as a file. The past operation data is past input / output actual data of the process, and new past operation data is sequentially added. The operation data input unit 1 extracts data (input actual data, output actual data) for a partial period from past operation data. The actual input data is data that has been input to the process in the past, and is operation data that defines the relationship between the time at a predetermined interval and the input value (operation value). The actual output data corresponding to the actual input data is data output from the process in the past, and is response data that defines the relationship between the time at a predetermined interval and the output value (response value). The file format is not limited to general CSV, and may be DATA format text. The storage location of this file is not limited, and data is automatically loaded if a path is specified.

(Data standardization processing department)
The data standardization processing unit 2 inputs input actual data (operation data) and output actual data (response data). The data standardization processing unit 2 standardizes (normalizes and makes no dimension) both operation data and response data in a range of 0 to 100. By standardization, the processing according to the present invention can be applied without depending on the process to be applied.

  In different fields, the change ranges of input values (operation values) and output values (response values) are quite different. For example, in the power system control, the operation range of the fuel amount that is an input value is 0 to 300 [t / h], and the response range of the pressure that is an output value is 0 to 20 [MPa]. On the other hand, in the liquid concentration control, the operation range of the operation flow rate that is an input value is 0 to 0.02 [g / s], and the response range of the concentration that is an output value is 0 to 100,000 [mol / kg].

  By performing the standardization process, the step signal search filter 3 and the response signal search filter 4 can be applied without depending on the process, so that the versatility of the present invention can be enhanced.

(Step signal search filter)
The step signal search filter 3 has a function of searching operation data that approximates a step signal from actual input data (operation data) standardized by the data standardization processing unit 2. FIG. 2 is a diagram for explaining an example of the operation of the step signal search filter 3. The step signal search filter 3 inputs actual input data (operation data) obtained by standardizing the coal flow rate in the “1: 50-2: 01” time zone at the pulverized coal power plant.

  First, the step signal search filter 3 calculates the amount of change ΔMV of the input value (operation value) MV at each time from the operation data. ΔMV is an absolute value of the difference between the operation values MV per unit time, and is also referred to as an operation change value ΔMV (FIG. 2).

  Next, the step signal search filter 3 sorts the variation ΔMV in unit time in descending order.

  Next, the step signal search filter 3 determines whether or not the operation data in the predetermined time range immediately before and after the time Mt at which the maximum input change amount ΔMVmax is obtained is in a calm state (equilibrium state). As a criterion for determining the calm state, if ΔMV is continuously within a certain number of tolerances, the calm state is determined.

  In the example shown in FIG. 2, the maximum input change amount ΔMVmax = 53.7 is detected at time Mt = 1: 54. Further, the determination constant “5” is employed as a fixed number of times, and the allowable change range (tolerance) of the input value is an empirical range [−15, 15], just before “1:54”. Since the change amounts ΔMV are all within the allowable range in the time zone “1:50 to 1:53” and the time zone “1:55 to 2:01” after “1:54”, these times The operation data in the belt is in a calm state.

  The step signal search filter 3 determines that the actual input data (operation data) is a step input when satisfying the criteria for determining a calm state.

  Note that the number of determinations and the tolerance described above are not limited. For example, the tolerance may be between 20% and 40% of the maximum input value of the operation data, that is, [−10, 10] or [−20, 20].

  If the input actual data (operation data) is not determined to be step input, the operation data input unit 1 again extracts data for a different partial period from the past operation data. Thereby, operation data that approximates the step signal can be found from the past operation data. For example, data of a partial period in the next time range (time range after 2:02) in FIG.

(Response signal search filter)
The response signal search filter 4 has a function of searching for output actual data (response data) that responds to the input actual data (operation data) determined as step input by the step signal search filter 3. FIG. 3 is a diagram for explaining an example of the operation of the response signal search filter 4.

  The step change time Mt is detected from the operation data approximate to the step input found by the step signal search filter 3. The processing target of the response signal search filter 4 is response data from the time Mt to the end of the step response.

  First, the response signal search filter 4 calculates the change amount ΔPV of the output value (response value) PV at each time after the time Mt from the response data. ΔPV is an absolute value of the difference between the response values PV per unit time, and is also referred to as a response change value ΔPV (FIG. 3). The response signal search filter 4 extracts the maximum output change amount ΔPVmax.

  Next, the response signal search filter 4 determines whether the state of the change amount ΔPV in the period immediately before and after the time when the maximum output change amount ΔPVmax is obtained is a rapid change state or a calm state. The response signal search filter 4 determines that the transient period Δt in which the change amount ΔPV in the period immediately before and after the time when the maximum output change amount ΔPVmax is obtained is equal to or larger than the reference amount smaller than the maximum output change amount ΔPVmax is a sudden change state. To do. Further, a period that is less than the reference amount is determined to be a calm state.

As an example, the determination criteria for the calm state are defined as follows.
(1) First, the calm state reference value PVst is calculated as the reference amount. Here, PVst = 1/3 × ΔPVmax. This formula is empirical.
(2) The absolute value of the ΔPV data list is calculated and compared with PVst.
(3) If | ΔPV | <PVst, the state of ΔPV at that time is determined to be a calm state.
(4) If | ΔPV | ≧ PVst, it is determined that the state of ΔPV at that time is a sudden change state.

  The response signal search filter 4 outputs response data in the time zone “1:57 to 2:04”. From this response data, the transition period Δt and the period output change amount ΔPV (V) that has changed during the transition period Δt can be acquired.

  FIG. 3 is a diagram for explaining an example of the operation of the response signal search filter 4. As shown in FIG. 3, time Mt = 1: 54. In FIG. 3, ΔPV of the main steam pressure after time Mt is calculated. Here, ΔPVmax = 10.8. PVst = 3.6 from (1) of the determination criterion of the calm state mentioned above. Accordingly, the response data in the time zone “1:54 to 1:56” and the time zone “2:05 to 2:10” are determined to be in a calm state.

  The above-described calm state reference value PVst is not limited. For example, the calm state reference value PVst may be a predetermined amount between a quarter or more and a half or less of the maximum output change amount ΔPVmax.

(Dynamic characteristics automatic calculation section)
The dynamic characteristic automatic calculation unit 5 has a function of automatically calculating dynamic characteristics (K, T, L) based on the outputs of the step signal search filter 3 and the response signal search filter 4. The step signal search filter 3 and the response signal search filter 4 extract data approximate to the step response test from the data of a part of the past driving data, and the dynamic characteristic automatic calculation unit 5 determines the dynamic characteristic based on this data. Calculate automatically.

The flow of calculation is as follows.
(1) The dead time L is calculated based on the rapid operation value change time Mt and the response change start time Pt (FIG. 3). Specifically, L = Pt−Mt. In the example shown in FIGS. 2 and 3, Mt = 1: 54, Pt = 1: 57, and L = 3 minutes.
(2) The gain K is calculated by K = ΔPV (V) / ΔMV (V). Here, ΔMV (V) is the difference between the final value and the start value of the sudden change state of the MV value data (ΔMVmax). ΔPV (V) is the difference between the final value and the start value of the sudden change state of the PV value data. In the example shown in FIGS. 2 and 3, ΔPV (V) = 69.4, ΔMV (V) = 46.3, and K = 1.5.
(3) The integration time T is T = ΔPV (V) / Δt, and Δt is the elapsed time (transient period) of the sudden change state of the response value data. In the example of FIG. 3, since the time zone of the rapid change state is “1:57 to 2:04”, Δt = 8 minutes and T = 8.7.

(Dynamic characteristic determination part)
The dynamic characteristic determination unit 6 outputs the dynamic characteristics (K, L, T) calculated by the dynamic characteristic automatic calculation unit 5. The output dynamic characteristics are substituted into the transfer function parameters shown in equation (1).

  According to the integrated system process dynamic characteristic identification device in the present embodiment, data that approximates a step response test is searched from past operation data, and the process dynamic characteristics are calculated as needed, so that the dynamic characteristics of the process are always followed. It becomes possible to do. Thereby, the effect equivalent to a step response test is acquired, without affecting the operation of a plant. Further, by using the newly accumulated past operation data, the dynamic characteristics of the process can be quickly grasped even if the operation environment, for example, the boiler operation environment such as fuel quality changes. Furthermore, more stable control is possible by interlocking with IMC or MD-PID parameter tuning. Energy saving effect can be expected by appropriate process control.

  In the first embodiment described above, the step signal search filter 3 is the “step input determination means” in the present invention, and the response signal search filter 4 is the “step response acquisition means” in the present invention. 5 corresponds to “dynamic characteristic automatic calculation means” in the present invention.

DESCRIPTION OF SYMBOLS 1 Operation data input part 2 Data standardization process part 3 Step signal search filter 4 Response signal search filter 5 Dynamic characteristic automatic calculation part 6 Dynamic characteristic determination part K Gain L Dead time Mt Operation value change time MV Input value (operation value)
Pt Response change start time PV output value (response value)
T integration time ΔMV operation change value ΔPV response change value Δt transient period

Claims (5)

An integral system process dynamic characteristic automatic identification device for identifying a dynamic characteristic of a process represented by a transfer function including an integral element,
Of the partial period data extracted from the past input / output actual data of the process, the input value change amount ΔMV for each time is calculated from the input actual data defining the relationship between the time at the predetermined interval and the input value. When the change range of the input value in the predetermined time range immediately before and after the time Mt at which the maximum input change amount ΔMVmax is obtained is equal to or smaller than the allowable change width smaller than the maximum input change amount ΔMVmax. Step input determination means for determining the input actual data as step input;
When the input actual data is determined to be a step input, from the output actual data that defines the relationship between the time at the predetermined interval and the output value among the data of the partial period, the change amount ΔPV of the output value for each time A transition period Δt that is a period immediately before and immediately after the time when the maximum output change amount ΔPVmax is obtained, and in which the change amount ΔPV is equal to or greater than a reference amount smaller than the maximum output change amount ΔPVmax, and the transient period Δt Step response acquisition means for acquiring a period output change amount ΔPV (V) changed during
Automatic dynamic characteristic calculation for calculating parameters of the transfer function based on the maximum input change amount ΔMVmax, the period output change amount ΔPV (V), the transient period Δt, the start time Pt of the transient period Δt, and the time Mt. Means,
An apparatus for automatically identifying the process dynamic characteristics of an integral system, comprising: The transfer function is represented by the following transfer function G (s) including a gain K, a dead time L, and an integration time T as parameters, where the gain K is K = ΔPV (V) / ΔMVmax, 2. The integrated system process dynamic characteristic automatic identification device according to claim 1, wherein the time L is L = Pt−Mt, and the integration time T is T = ΔPV (V) / Δt.

If the input actual data is not determined to be step input by the step input determination means, data of a partial period different from the partial period data is extracted from the past input / output actual data, and the step input determination is performed again. Means for performing the means,
The integrated system process dynamic characteristic automatic identification device according to claim 1 or 2, further comprising:   4. The integration system process according to claim 1, wherein the allowable change width is a predetermined width between 20% and 40% of a maximum input value in the input actual data. 5. Dynamic characteristic automatic identification device.   5. The integral system process operation according to claim 1, wherein the reference amount is a predetermined amount between a quarter and a half of the maximum output change amount ΔPVmax. Automatic characteristic identification device.

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