JP3628884B2 - Steam header pressure controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steam header pressure control device for appropriately controlling steam header pressure in a power plant that is a concentrated supply source of steam to each plant in a complex composed of a plurality of plants.
[0002]
[Prior art]
As a control method of the steam header pressure, conventionally, (1) a method in which the steam pressure sent out in the power plant is always constant, and (2) steam sent out in the power plant manually by the operator by communication from another plant. There are a method of adjusting the pressure, and (3) a method of controlling the steam pressure of the delivery in the power plant by applying a control calculation with the input of a certain plant pressure considered to be important.
[0003]
However, in the methods (1) and (2), since the pressure loss in the steam piping actually changes due to changes in the plant operating conditions, etc., the steam header pressure is always kept at an appropriate level considering the steam pressure at the end plant. It was difficult to hold. Even in the method of (3), there are actually several plants that need to be focused on due to changes in the operating conditions of the plant, etc., and the constraint value of the steam pressure may change with the progress of equipment contamination over time. For this reason, if the steam header pressure is too low, the operation of the plant is hindered, so the steam header pressure has been increased.
[0004]
[Problems to be solved by the invention]
In the prior art, in a complex consisting of a plurality of plants, the steam demand of each plant and the operation status of each plant change from moment to moment, whereas if the steam header pressure in the power plant is kept constant, inefficient operation It was a factor that hindered stable operation of the plant. In addition, it is not realistic that the operator frequently adjusts the steam header pressure while arranging operators in plural plants and communicating with each other because mental fatigue is too great. In addition, even in the method of controlling the steam header pressure by applying a control calculation with the pressure of one plant as an input, the state quantity of other plants may actually be restricted due to changes in the operating status of each plant. In addition, even when focusing on a single plant, the steam pressure constraint value may change with the progress of equipment contamination over time. It was.
[0005]
The present invention has been made paying attention to such problems, and maintains the steam header pressure in a complex composed of a plurality of plants at a value that does not hinder the safe and stable operation of each plant, and as a whole efficiently operates. It aims at providing the control apparatus of the steam header pressure for performing.
[0006]
[Means for Solving the Problems]
The present invention for solving the above problems is a steam header pressure control device in a complex composed of a plurality of plants,
A process input unit for inputting the state quantity of each plant that changes every moment such as the steam pressure and steam valve opening of a plurality of plants;
The preset fixed constraints on constraint conditions of each plant, also the constraint condition setting unit that sets entered variable constraints,
A variable constraint value that calculates a constraint value of the variable constraint condition and supplies the constraint value to the constraint condition setting unit based on the state quantity of each plant that is input to the process input unit every moment and the fixed constraint condition An arithmetic unit;
Using the state quantity of each plant and the fixed and variable constraint conditions as inputs, an appropriate steam header pressure set value is calculated by predictive control using a multivariable model so that the entire complex is in an efficient operation state. A multivariable model predictive control unit ;
A steam header pressure set value output unit for outputting the set value of the steam header pressure as a calculation result to a lower control device that controls the steam header pressure;
With
The variable constraint value calculation unit determines whether there is a margin in the control of the state quantity based on the state quantity of each plant that is input to the process input unit every moment and the fixed constraint condition, When it is determined that there is a margin in the amount control, the constraint value of the above variable constraint condition is calculated in a direction to reduce the state amount control margin, and it is determined that there is no margin in the state amount control. Is a steam header pressure control device that calculates the constraint value of the variable constraint condition in a direction to increase the margin of state quantity control , wherein MV is the valve opening of the steam control valve, and MVH is the valve opening The upper limit constraint value of MV, ΔP is a margin of state quantity control, K is a coefficient for calculating the margin ΔP, and the margin ΔP is expressed by the following equation:
ΔP = K × (MVH−MV)
VPL is a variable lower limit constraint value for the steam acceptance pressure of the plant, and subscripts t and t + 1 of VPL are a current value and a value to be calculated next time,
The variable constraint value calculation unit calculates the margin ΔP according to the above equation, and if ΔP is a positive number, the value of VPL _{t + 1} is set to either the value of (VPL _t −ΔP) or the value of PL. If the larger value is used and ΔP is negative, the value of VPL _{t + 1} is calculated to be the value of (VPL _t −ΔP) and supplied to the constraint condition setting unit. A gist of the steam header pressure control device characterized by the above.
[0007]
[Action]
In the present invention, since the state quantities of a plurality of plants that change from moment to moment are taken online and automatically controlled, the optimum steam header pressure according to the operation state of the plant is not affected by the ability of the operator. Operation becomes possible.
[0008]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a steam header pressure control apparatus showing an embodiment of the present invention. In the figure, a steam header pressure control apparatus 1 includes a process input unit 2, a variable constraint value calculation unit 3, a constraint condition setting unit. 4, a control calculation unit 5 and a set value output unit 6 are provided. In addition, a plurality of plants including an A plant 7a, a B plant 7b, a C plant 7c, and a power plant 7d constitute a complex. In the illustrated example, each of the A, B, and C plants 7a to 7c is changed from the power plant 7d. On the other hand, steam is supplied. The steam header pressure of the power plant 7 d is controlled by the steam header pressure control device 1 via the lower control device 8.
[0009]
The process input unit 2 is for inputting state quantities such as the steam acceptance pressure and valve opening degree of each plant from the input group 7, and is supplied to the variable constraint value calculation unit 3 and the control calculation unit 5.
The variable constraint value calculation unit 3 is for calculating a constraint value when the constraint value of the steam reception pressure changes due to a change in the operation state of the plant. The constraint value setting unit 4 calculates the constraint value of the fixed constraint condition. The variable constraint value is input, and the calculation result is supplied to the constraint condition setting unit 4.
[0010]
The constraint condition setting unit 4 is for setting a constraint condition such as a steam receiving pressure and a valve opening degree in each plant 7a, 7b, 7c. It consists of what is supplied from the constraint value calculation unit 3 and is supplied to the control calculation unit 5.
The control calculation unit 5 is for calculating an appropriate set value of the steam header pressure based on the data supplied from the process input unit 2 and the constraint condition setting unit 4, and is obtained by the control calculation unit 5. The calculation result is supplied to the set value output unit 6.
[0011]
Here, as the fixed constraint conditions, there are a valve opening upper limit constraint value for each plant, a lower limit constraint value for each plant acceptance pressure, and the like. The variable constraint condition is obtained from the plant operating status such as valve opening and pressure and the constraint value of the fixed constraint condition.
The set value output unit 6 receives an output signal from the control calculation unit 5 and changes the setting of the lower control device 8.
[0012]
FIG. 2 is a diagram showing a detailed configuration when the steam header pressure control device 1 shown in FIG. 1 is applied to a complex composed of a power plant and a plurality of plants (here, A plant, B plant, C plant). In the figure, 9 is a pressure detector in a power plant, 10 is a pressure adjustment operation end, 11a to 11c are pressure detectors in each plant, 12 is a steam adjustment valve in the A plant, 13 is a valve opening detector, 14 Is a steam header pipe.
[0013]
Next, the operation of this embodiment configured as described above will be described.
According to the configuration shown in FIG. 2, the steam pressure of the power plant that supplies steam to each plant in the complex is detected by the pressure detector 9, and the detected signal is input to the lower control device 8. The control calculation for maintaining the steam pressure at the set value is performed by the control device 8. The calculation result is output to the pressure adjusting operation end 10 to control the steam pressure.
The steam acceptance pressure of each plant is detected by the pressure detectors 11a to 11c, and as an example, the valve opening degree of the steam regulating valve 12 used in the A plant is detected by the valve opening degree detector 13, and these are detected. The signals detected by the devices 11a to 11c and 13 are supplied to the process input unit 2 of the steam header pressure control device 1.
[0014]
The process state quantity in the process input unit 2 is input to the control calculation unit 5, and the state quantity related to the constraint value that needs to be automatically changed according to changes in the plant operating conditions is input to the variable constraint value calculation unit 3. Then, the constraint value is calculated in the variable constraint value calculation unit 3.
As an example, when the valve opening degree of the steam regulating valve 12 is almost fully open and becomes uncontrollable as the equipment in the A plant progresses over time, it is necessary to increase the steam header pressure. That is, for example, the variable constraint value is calculated as follows.
[0015]
First, a margin ΔP expressed by the following equation is defined for the valve opening of the steam control valve.
ΔP = K × (MVH−MV)
Here, MV is the valve opening, MVH is the upper limit constraint value of the valve opening, and K is a coefficient for calculating the margin ΔP.
The variable lower limit constraint value for the steam acceptance pressure of the plant is calculated by the following equation.
If ΔP is a positive number,
VPL _{t + 1} = max {(VPL _t −ΔP), PL}
If ΔP is negative or zero,
VPL _{t + 1} = VPL _t −ΔP
However, VPL is a variable lower limit constraint value for the steam acceptance pressure of the plant, and the subscripts t and t + 1 indicate the current value and the value calculated next time, respectively. PL is a fixed lower limit constraint value for the steam acceptance pressure of the plant.
Further, max {Z1, Z2} is a function for selecting the larger value of the numerical values Z1 and Z2.
[0016]
The variable constraint value calculated in this way is supplied to the constraint condition setting unit 4.
The constraint condition setting unit 4 supplies the fixed constraint condition and the variable constraint condition calculated by the variable constraint value calculation unit 3 to the control calculation unit 5.
The control calculation unit 5 takes in the process state quantity from the process input unit 2, takes in the constraint conditions from the constraint condition setting unit 4, calculates the set value of the steam pressure delivered in the power plant by the control calculation, and sets the set value output unit 6 is supplied. Multivariable model predictive control was used for the control calculation.
[0017]
The set value output unit 6 receives an output signal from the control calculation unit 5 and changes the setting of the lower control device.
As described above, in this embodiment, the state quantities of a plurality of plants that change from moment to moment are taken online and controlled, so the steam header pressure corresponding to the operation state of the plant is not affected by the ability of the operator. Optimal operation is possible.
[0018]
FIG. 3 is a flowchart showing the variable constraint value calculation processing based on the above-described equation regarding the valve opening degree in the steam header pressure control apparatus of the present invention applied to the complex of FIG.
In the configuration of the example in FIG. 2, the valve opening is detected only in the A plant, but may be detected in any plant. First, a margin ΔP is calculated by the equation ΔP = K (MVH−MV) using the detected valve opening MV of the plant and the valve opening upper limit value MVH of the fixed constraint.
[0019]
Next, according to whether the margin ΔP is positive or negative, the current variable lower limit constraint value VPL _t , the fixed lower limit constraint value PL, and the margin ΔP in each plant are used to correct the variable lower limit constraint value VPL. _{t + 1} is obtained as follows.
(1) When ΔP> 0, (VPL _t −ΔP) is compared with PL, and the larger _one is output as a corrected value VPL _{t + 1} .
(2) When ΔP ≦ 0, (VPL _t −ΔP) is calculated and output as a corrected value VPL _{t + 1} .
[0020]
(1) is a case where there is a margin in the plant acceptance pressure as judged from the valve opening, and the steam header pressure is further reduced by the margin ΔP (positive number) from the previous variable constraint value. Control is performed so as not to lower the lower limit of the steam receiving pressure.
(2) is a case where there is no margin in the plant acceptance pressure as judged from the valve opening, and the margin ΔP (negative number or zero) is further subtracted from the previous variable constraint value. That is, control is performed so as to increase the pressure.
[0021]
Note that the steam header pressure control device of the present invention can be applied to other than the plant shown in FIG. 2 and generally has various steam levels such as high pressure, medium pressure, and low pressure in a complex. Of course, it is applicable. Moreover, although an example was described about the variable constraint value of the steam pressure, the factors that cause the constraint value to change are various according to the circumstances of the plant, and the present invention can be applied to other examples.
[0022]
【The invention's effect】
As described above, the present invention performs on-line capture control of the state quantities of a plurality of plants that change from moment to moment, so that the steam header pressure corresponding to the operation state of the plant is not affected by the ability of the operator. Optimum operation is possible, and energy saving can be achieved under the safe and stable operation of the plant.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a steam header pressure control apparatus showing an embodiment of the present invention.
FIG. 2 is a detailed configuration diagram of a complex to which the steam header pressure control device of the present invention is applied.
FIG. 3 is a flow of variable constraint value calculation processing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steam header pressure control apparatus 2 Process input part 3 Variable constraint value calculating part 4 Restriction condition setting part 5 Control calculating part 6 Set value output part 7a-7d Plant 8 Subordinate control apparatus

Claims (1)

A steam header pressure control device in a complex consisting of a plurality of plants,
A process input unit for inputting the state quantity of each plant that changes every moment such as the steam pressure and steam valve opening of a plurality of plants;
The preset fixed constraints on constraint conditions of each plant, also the constraint condition setting unit that sets entered variable constraints,
A variable constraint value that calculates a constraint value of the variable constraint condition and supplies the constraint value to the constraint condition setting unit based on the state quantity of each plant that is input to the process input unit every moment and the fixed constraint condition An arithmetic unit;
Using the state quantity of each plant and the fixed and variable constraint conditions as inputs, an appropriate steam header pressure set value is calculated by predictive control using a multivariable model so that the entire complex is in an efficient operation state. A multivariable model predictive control unit ;
A steam header pressure set value output unit for outputting the set value of the steam header pressure as a calculation result to a lower control device that controls the steam header pressure;
With
The variable constraint value calculation unit determines whether there is a margin in the control of the state quantity based on the state quantity of each plant that is input to the process input unit every moment and the fixed constraint condition, When it is determined that there is a margin in the amount control, the constraint value of the above variable constraint condition is calculated in a direction to reduce the state amount control margin, and it is determined that there is no margin in the state amount control. Is a steam header pressure control device that calculates the constraint value of the variable constraint condition in a direction to increase the margin of state quantity control , wherein MV is the valve opening of the steam control valve, and MVH is the valve opening The upper limit constraint value of MV, ΔP is a margin of state quantity control, K is a coefficient for calculating the margin ΔP, and the margin ΔP is expressed by the following equation:
ΔP = K × (MVH−MV)
VPL is a variable lower limit constraint value for the steam acceptance pressure of the plant, and subscripts t and t + 1 of VPL are a current value and a value to be calculated next time,
The variable constraint value calculation unit calculates the margin ΔP according to the above equation, and if ΔP is a positive number, the value of VPL _{t + 1} is set to either the value of (VPL _t −ΔP) or the value of PL. If the larger value is used and ΔP is negative, the value of VPL _{t + 1} is calculated to be the value of (VPL _t −ΔP) and supplied to the constraint condition setting unit. Steam header pressure control device characterized by.

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