JPH06102903A - Control system for plant - Google Patents

Abstract

PURPOSE:To control a plant with the high degree of freedom and to manage the life of the whole plant by evaluating the life consumption of an auxiliary machine, variably altering the adjustment parameter of a controller by means of a remaining life and operating an operation terminal in accordance with the controller output. CONSTITUTION:A process amount operation permission limit allowance value calculation control part 4 calculates an allowance value 100c as against the limit of a process amount and changes the strength of control in accordance with the size of the allowance value. Namely, control from the viewpoint of the allowance value 100c against the restriction condition of the real measurement value of the process amount is executed by using a plant control transmission function 5 (G(S)). Then, the process amount operation permission limit allowance value 100c is varied in accordance with a situation for the respective units and the setting of an allowed operation upper limit value considering the life consumption situation of respective units and 8 subsequent operation schedule is detected from the viewpoint of the whole plant life. Thus, the plant can rationally be operated without waste by making the lives of the respective units to be exhausted when the life of the plant expires.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for various plants, and more particularly to a control system for a plant in consideration of the margins of individual operation control values of equipment constituting the plant.

[0002]

2. Description of the Related Art As various plants, for example, in a thermal power plant, as shown in JP-A-62-207200, a load change rate or a permissible load is allowed for a turbine or a generator as a main device (main engine). The load change range is set and these devices are operated according to these. That is, the operation is performed so as to match the set load change rate, and the operation state is limited within the set allowable load change range.

[0003]

In the conventional example, the reason for adopting such control and limitation is that the life consumption of the turbine or the generator as a single unit is taken into consideration. In other words, it has been required in recent years to operate these devices with the intention of replacing them after the planned expiration date, and for this purpose, it is determined how many times the load should be changed at the planned rate of change. Therefore, the operation is performed in compliance with the load change rate, and the operation in the load change width of an unnecessary size is prohibited.

According to this method, the main engine can wear out as much as the estimated life at the time when the service life of the plant has passed. However, looking at many other plant devices that are not subject to such management, they are operated under fixed fixed operation limits, and are not sufficient in terms of life management.

Therefore, if the plant equipment is considered in terms of the durability performance in terms of hardware determined by the specifications of the plant equipment, the degree of wear and tear due to operation, the margin of operation from the aspect of plant operation, or the tolerance from the aspect of facility capacity. Then, not only is it possible to realize plant control with a higher degree of freedom than before, but it is also possible to manage the life of the entire plant.

From the above, the present invention is characterized by providing a plant control system capable of realizing plant control with a higher degree of freedom than ever before and managing the life of the entire plant. To do.

[0007]

SUMMARY OF THE INVENTION In the present invention, the margin of the process state quantity operation control value is determined from the relationship between the range of the process state quantity as an element constituting individual process control and the actual operating point. Focusing attention, the strength of control is dynamically changed according to the value of the margin, or the control order is prioritized to quickly match the control amount to the target value,
In addition, a cooperative control system that does not deviate from the management limit value of the individual process amount is realized.

[0008]

The process state quantity of the plant or system is actually measured or observed, and is compared with the target value inside the control device. If there is a deviation, the operation end is moved within the control device in the direction to make the deviation zero. Create the operation amount to operate. In the process of creating this manipulated variable, a control function with a margin value up to the operation allowable limit value is added,
The control system operation in which the above deviation is set to 0 is strengthened. As a way of strengthening the operation of this control system, when the process state quantity moves away from the target value and the margin value up to the inherent limit value of the process itself decreases at that time, the reduced margin value is returned to the originally expected value. As described above, the size of the parameter is determined, and the operation of superimposing or multiplying the operation amount is performed. In the application to the control system, the smaller the margin value, the greater the influence on the original control system operation amount, and the stronger the control.

[0009]

FIG. 1 is a diagram showing an embodiment of the concept of the present invention. The transfer function characteristic of the process part 1 of the plant is expressed by a plant process quantity transfer function 6 (H (S)) and a disturbance 7 to the plant. The plant control unit 2 includes a process amount target value setting unit 3, a process amount operation allowable limit margin value calculation unit 4, and a plant control transfer function 5 (G (S)).

In this figure, a process amount target value is set as necessary based on the plant process amount measured value 100a. The process amount target value or the deviation 100b between the process amount target value and the actually measured value is transmitted to the process unit 1 of the plant as an operation signal 100d by the plant control transfer function 5 (G (S)). The plant process quantity transfer function 6 (H (S)) receives the operation signal 100d and the plant disturbance 100e and outputs a process quantity measurement value 100a. Normally, the process amount 100a of the plant is subject to a limit value due to the constraint condition of the hardware equipment constituting the process unit 1. Conventionally, the plant control transfer function G is used.
The process amount was controlled by a number of subtle control logics in (S).

According to the present invention, the newly provided process amount operation allowable limit margin value calculation control unit 4 calculates a margin value 100c for the limitation of the process amount, and the control strength is changed according to the magnitude of this margin value. It is a thing. That is, the plant control transfer function 5 (G (S)) is used to perform control from a new point of view, that is, a margin value for the constraint condition of the actual measured value of the process amount. In the following, as an example, an object controlled by the minor loop in the plant process amount will be described as an example.

FIG. 2 shows an example of conventionally known heat exchanger outlet temperature control for performing heat exchange between gas and gas. In the figure, 31a is a heated gas (low temperature gas) pipe, 31b is a heated gas bypass pipe, and 31c is a heated gas (high temperature gas) pipe. The gas to be heated in the pipe 31a is heated through the gas / gas heat exchanger 32 by receiving heat from the heating gas pipe 31c. By the way, the gas to be heated is often set to an upper temperature limit for the purpose of preventing thermal decomposition due to overheating, preventing gas flashback, or the like. Therefore, the gas flow rate is distributed through the heated gas bypass pipe 31b, and the outlet gas temperature control valve 33 performs constant control of the outlet gas temperature.

This control is performed as follows. First, the temperature measurement end 34 detects the heated temperature signal 101a, and the deviation 36 from the set value signal 101b of the temperature setter 35 is detected.
Is taken. In the normal minor loop, PI control is applied to the deviation signal 102. That is, the signal 103a multiplied by the control proportional gain K _C in the controller 37
Is integrated at 38, the output of which becomes a fluid signal 105 by the electric / fluid converter 39, and the outlet gas temperature control valve 33 is operated.

By the way, generally, the change of gas composition is small, the specific heat is approximately constant, and the flow rate of heated / heated gas and the pattern of enthalpy change are properly recognized as the dynamic characteristics of the plant. If so, a sufficient control result can be expected with the minor loop of FIG. However,
When the gas composition changes greatly and the change in gas enthalpy is significant and includes an uncertain factor, a single PI control constant may break the limiting condition. In this case, if there is no restriction on the cost, means such as predictive control can be taken by providing another measuring end, etc. However, if it is desired to use minor loop control, more flexible control is required.

FIG. 3 shows that flexible follow-up control is possible by changing the control constant according to the margin up to the allowable temperature limit value. The part surrounded by the broken line 40 is
This is a calculation unit for a control proportional gain correction factor based on the added allowable temperature limit margin value, and is multiplied by the original control proportional gain K _C in the multiplication unit 45, for example. In the broken line portion 40, the upper limit value / lower limit value of the temperature is first set by the allowable limit value setters 41a, 41b, respectively, and the margins with respect to the upper limit value / lower limit value are set by the difference calculating sections 42a, 42b from the actual measured value 101a. The value is calculated. The low selector 43 selects the margin value having the smaller margin value, and the value 44 of the margin value / proportional gain correction function f (Δ) in the function unit 44 becomes the control proportional gain 103b in the multiplier 45. It is multiplied and sent to the integrator 38 as the margin correction control proportional gain 103c. The margin correction proportional gain K _a is expressed here as follows.

K _a = f (min (X ₁ −X (t), X (t) −X ₂ )) × K _c where X ₁ and X ₂ are the allowable upper limit set value and the allowable lower limit of the control process amount, respectively. It is a set value, and X (t) is an actual process amount.

The function form of the margin value-proportional gain correction function f must satisfy at least the following conditions. First, f of the control process amount X (t) is approximately "1" in the vicinity of the control target value. That is, the proportional gain is substantially equal to the set value as long as it is near the control target value. Secondly,
The margin value correction proportional gain newly set is such that the operating speed of the operating end does not exceed the maximum operating speed (however, the control valve and the like are normally limited by the electric / fluid converter).

The above two conditions are shown in the graph of the process amount 101a and the operation signal 104 as shown in FIG. Straight line 46
Is the operation signal 104 when the proportional gain K _{c is} constant,
Dashed line 47 is an operation signal when the margin value correction coefficient gain K _a, 48a through 48c, respectively, the process amount allowable upper limit X _1, process variable control target value X _0, the process amount allowable lower limit value X _2. In the example of FIG. 4, the characteristic 47 of the margin correction proportional gain K _a is the allowable limit values 48 a, 48 of the process amount.
relatively large with respect to the original proportional gain K _c characteristics 46 closer to the c, limit value 48a, and the operation signal reaches 48c is set so as to be a maximum operation signal by the original proportional gain K _c is there. In FIG. 4, the integration time T = 0 is set to simplify the explanation, and the process amount limit values 48a and 48b are separated from the process amount control target value X ₀ by the same deviation.

FIG. 5 shows a characteristic 49 of the margin value-proportional gain correction function f at this time. When the process amount is close to the control target value, f is almost 1 and approaches the maximum value as the process amount margin value Δ approaches 0, and when Δ < 0, falls linearly based on the operating limit of the operating end. .

Next, the result of using the margin correction control based on the characteristics of FIGS. 4 and 5 will be described with reference to FIG.
FIG. 6-a qualitatively shows the temporal change of the process amount X (t) when the margin value-proportional gain correction control of FIGS. 3 to 5 is applied.

The solid line 50 shows the case where the control proportional gain K _{c is} constant, and shows the change over time in the process amount X (t) when a process amount disturbance that cannot be controlled occurs within the limit value at the set K _c. Is. On the other hand, the wavy line 51 is the result of applying the margin value-proportional gain correction control, and the process amount X
As (t) approaches the process amount lower limit value X ₂ , high-order feedback is applied to prevent (t) from falling below X ₂ .

FIG. 6-b shows the change over time of the operation signal Y (t) when the margin value-proportional gain correction control is applied, and the solid line 52 indicates the operation signal before the application of the correction control. The wavy line 53 indicates the operation signal after the correction control is applied.

FIG. 6-c shows a temporal change of the operating end state quantity Z (t) when the margin value-proportional gain correction control is applied. Here, the operating end state quantity corresponds to the valve opening degree if the operating end is a valve. The solid line 54 is the result without correction control, and the broken line 55 is the result with correction control.

The control parameters that can reflect the allowance value are gain parameters, bias values, PID control constants, and compressor super surge prevention control as in the above embodiment. All of the parameters corresponding to the function f, the parameters for changing the control target value, and other parameters in the control logic diagram can be targets.

The target of the margin value is the margin value for the change rate limit value of the process state quantity, including the margin value for the limit value of the process constituent equipment as in the above embodiment.
Margin value to the permissible life consumption rate of process components, margin value to the permissible consumption amount due to restrictions on the amount of makeup water, margin value to the permissible operating area such as control valves and compressors, equipment or plant start-up, etc. A margin value or the like until the target value arrival time is considered.

A specific application example is shown below.

1) Limit Value of Process Constituent Equipment FIG. 7 considers an example in which the steam temperature limit value is variable as an example of the limit value of the process constituent equipment. In a typical steam turbine, the limiting target value for the inflow steam temperature is set at 566 ° C. An alarm is output when the temperature is 8 ° C higher than the target limit value. Although this alarm is related to turbine heat resistance limitation, transient overshooting to some extent is not a problem as long as the integrated thermal fatigue allows. At this time, if the limit value is fixed to 566 + 8 ° C., an alarm will be output even when the steam temperature overshoots to an allowable level, and an alarm response that is not necessarily required is required.

On the other hand, a method is conceivable in which the limit set value of the high steam temperature is made variable, for example, by using the operation integrated time in the high steam temperature state as an evaluation scale. FIG. 7 shows an example of variable limit values (steam turbine temperature) of process components.
Conventionally, when the process state 80a occurs, the limit value is 8
Only the 0e (566 + 8 ° C) alarm is output.

However, regarding the thermal fatigue of the steam turbine, it is possible to design so that if the integrated value of the transient response overshoot time is less than a certain time, the limit value of 80e (566 + 8 ° C.) or more is allowed. In the example of FIG.
The temperature from the steam temperature rating is 4 ranks, ie 566
≦ T ≦ 566 + 8, 566 + 8 ≦ T ≦ 566 + 14,5
66 + 14 ≦ T ≦ 566 + 28, 566 + 28ST, and if the annual operating time is less than a certain value (condition 8
0c, 80d), new limit values 80f, 80h that exceed the original limit value 80e are adopted, and if the conditions 80c, 80d are not cleared, the original limit value 80e is adopted. As a result, control without wasteful handling becomes possible.

2) Example of change rate limit value of process state quantity (boiler heat transfer section tube) FIG. 8 shows an example of change rate limit value of process state quantity.
Consider an example in which the temperature change rate limit value of the boiler heat transfer section tube is made variable. Conventionally, the limit value of the temperature change rate of a typical boiler heat transfer section tube is 110 ° C./hr. Usually, the temperature change width of the boiler heat transfer tube is determined by the boiler operation schedule, but if the operation schedule is uncertain, it cannot be said that there is a basis for fixing the temperature change rate limit value. .

That is, the limit value of the temperature change rate is set so that the thermal stress fatigue of the equipment does not exceed the limit value in the operation below the limit value. When the boundary temperature of the boiler heat transfer tube changes stepwise, this thermal stress has a larger transient thermal stress as the temperature change width increases.

In this example, when the temperature change width is small,
The limit value of the rate of temperature change is increased, and if the range of temperature change is increased, the limit value of the conventional rate of temperature change is set to approach.

For example, if the temperature change width (see the horizontal axis in FIG. 8) is 10 [° C.] or less, the temperature rate limit value (∂
T _B / ∂t) res is 220 [° C.] (region 82b in FIG. 8),
If the temperature change width is 10 [° C.] or more, the temperature rate limit value (∂T _B / ∂t) res at this time is exponentially reduced from 220 [° C.] (region 82c in FIG. 8). ).

By adopting this method, it is possible to maximize the capacity of the boiler and to expect unnecessary reduction of alarm output.

3) Allowable Life Consumption (Rate) of Process Components For example, the life consumption rate of the steam turbine rotor needs to be optimally managed according to the turbine operation record and future operation plan. Conventionally, the life consumption amount for one load change is set and limited, but this is a rational life period for utilizing the life consumption amount and remaining life based on past operation results for future operation. By changing the limit value depending on the distribution, the life of the steam turbine plant can be effectively utilized.

FIG. 9 shows an example of the variable limit value of the permissible life consumption of the process components. In this example, the cumulative life consumption value 83a and the total life value 83b of the steam turbine plant up to the present
The remaining life value 83d is calculated from the difference between
e is allocated, and the allowable life consumption value 83m during normal operation and the allowable life consumption value 83n during start and stop are calculated from the future total operation time 83h and the future plant start / stop count 83g, respectively. , The variable limit value of the allowable life consumption of the plant.

As a result, the target time of the start / stop time is fixed by the schedule control in the past, but the start / stop time is reset according to the remaining life value to make the life of the steam turbine plant effective. Can be used for.

4) Allowable Consumption (Energy Loss, Amount of Supplementary Water Used, etc.) FIG. 10-a shows an example of a variable limit value of the allowable consumption of the supplementary water tank. Conventionally, there is no limit value for the amount of makeup water consumed in the makeup water tank, only an alarm is output when the tank water level is low, and there is no action for the low water level. In this example, a limit value for the amount of makeup water used is set according to the tank water level, such as 85a. This transiently suppresses the amount of makeup water used and suppresses unnecessary alarm output.

FIG. 10-b shows an example of the variable limit value of the allowable consumption amount of the coal mill. Conventionally, the allowable upper limit value and the allowable lower limit value of the coal supply amount have been set according to the upper and lower limit values of the coal mill and the number of operating coal mills. On the other hand, the limit value of the coal supply amount according to the speed of the coal feeder is set as 85b, and the lower limit is selected as the total coal mill upper limit values 86d and 86a for the allowable upper limit value 85k. For the allowable lower limit value of 85 liters, the highest value is selected as the total coal mill lower limit value 86i and 86b. As a result, the allowable upper and lower limits are set in consideration of the case where the coal feeder speed is transiently low, and the pulverized coal supplied to the boiler is limited depending on the case, allowing flexible coal feeding and monitoring of the coal feeding amount. Is possible.

5) Allowable operating range of valves, control valves, devices, etc. Operation of conventional control valves with a low opening is not allowed. This is because the use of the valve at a low opening causes erosion, and conventionally, this area is controlled to be ON / OFF.
FIG. 11-a shows the allowable operating region of the control valve. However, the transient control in the low opening region may contribute to the stability of the system. FIG. 11-b shows an example of setting the variable operation region of the control valve.

In this example, if the total operation accumulated time in the valve opening range of 5 to 10% is 100 HR or less (87d), the allowable valve opening is set to 5% or more, and if the condition 87d is not satisfied, the allowable valve opening is set. The opening is 10% or more. As a result, control can be performed in the case where the operation in the region where the valve opening degree is 5% to 10% is transiently required, and more flexible suppression is possible.
The set value of the maximum operation accumulated time 100HR of the control valve that allows the low opening operation is defined as the maximum operation time in which erosion does not matter. In addition, it is easy to change the soft logic of the controller when applying this method.

FIG. 12 shows an embodiment of control gain adjustment based on the margin value of the cooperative control system. In a normal control system,
The cooperative control unit 60 of a plurality of processes sets the target values 113a to 113c for the PI control units 68a to 68c of the operation ends 67a to 67c of the respective process amounts, and cooperates in the process amount minor control. I am trying. Normally, each control constant is set so as to follow the expected process quantity fluctuation, but in an actual plant, unexpected disturbance, fluctuation of the process quantity dynamic characteristics due to aging deterioration of equipment,
At the time of special operation, there is a possibility that the process amount will exceed the constraint condition of the equipment.

Therefore, in the present embodiment, the operation allowable limit margin value adjusting section 61 is provided, and the gains 62a to 62 corresponding to the margin values are set to the target values 110a to 110c from the cooperative control section 60.
By controlling the direction of increasing the margin value by multiplying by c, it is possible to prevent in advance from exceeding the constraint condition against accidental disturbance or the like.

The margin value adjuster 61 receives the measured values 112a to 112c of the process quantities detected by the detection ends 66a to 66c, and the deviation Δ from the process quantity limit value X set in the margin value adjuster 61. Is calculated and the gain K as a function of the deviation Δ is set to the target set value 110a from the cooperative control unit 60.
Take ~ 110c.

According to this method, since it is possible to control while maintaining the conventional cooperative control as a base, the minor control and the cooperative control unit of each process amount have an advantage that the design adjustment can be performed in the same way as the conventional one. To have.

The concept of the gain K is basically the same as that of the gas / gas heat exchanger embodiment, and the expected disturbance of 3
It is considered that the practically satisfactory margin value adjustment is achieved by setting the gain K that can follow the disturbance having the double standard deviation.

FIG. 13 shows the process amount time evolution of the margin value-proportional gain adjustment coordinated control. The process amount upper / lower limit values 72a to 72c are respectively included in the process amounts 1 to N.
Is set. If there is a disturbance 73a that cannot be covered by the cooperation control unit 60, the gain 62a in FIG.
By multiplying by ~ 62c, the time evolution can be improved as from 73a to 74a.

As described above, in a plant composed of a plurality of processes (it may not be composed of a plurality of processes), it is important to match the process state quantity with the target value. From a plant operation perspective, it is possible to perform control that reflects the durability performance in terms of hardware determined by the specifications of the equipment, the degree of wear and tear, the operational margin from the plant operation aspect, or the tolerance from the facility capability aspect. More importantly.

Focusing on this point, the present invention dynamically changes the control strength according to the margin for the process state quantity allowable limit value that changes according to the operating state in controlling the process state quantity. .

For this reason, in the present invention, in the control system for controlling the process state quantity (plurality) to the target value determined by the corresponding operating end, the actually measured value of the process state quantity is the permissible value permitted by the process. In addition, the control parameter of the process control is dynamically changed according to the margin value with respect to the optimum allowable value according to the operating state.

With reference to FIG. 14, the signal flow to the control system for each individual operating end and the control effect thereof will be described by making the margin value variable.

The margin values in the individual control processes created by 61a to 61d are used to determine the corresponding process for the new operation request 61g and how to change the setting of the control parameters. It is necessary to synthesize according to the procedure. Specifically, 61a (3
Extra charge), 61b (additional charge of 50%), 61c (additional charge of 30%), 6
1d (80% increase is possible) If the allowance value is increased as compared to the conventional value, and the process is allowed, adjust to the smallest allowable values 61a and 61c after the change. The control parameter 61f, that is, the control set value may be changed. This is from 61e to 61
This is the content of the signal processing to f. In FIG. 12, the values of the conventional control set values 110a, 110b, 110c, etc. are added to the signal 111 from the operation allowable margin value adjusting unit 61.
a, 111b, 111c, the final control set values 113a, 113b, 1 are added or multiplied by the set values.
13c is created.

By the above-mentioned operation, the valves at the respective operating ends of the boiler fuel flow rate control, the steam temperature control, the steam turbine control valve control, the boiler feed water flow rate control, and the load increase command to the electric motor are created, and these auxiliary machines are made to have a longer life. This leads to driving to the consumer side. As a result, an increase in load according to a new request can be achieved earlier than in the case where only the conventional circuit 60 is used, and the life and consumption coordination of the entire plant is also achieved.

[0054]

EFFECTS OF THE INVENTION According to the present invention, the durability in terms of hardware determined by the specifications of each device constituting the plant, the degree of life loss, the operational margin in plant operation, or the tolerance in terms of facility capacity. In this way, it is possible to construct a coordinated control system for the entire plant because wrinkling in part is eliminated, and a margin reflecting the constantly changing plant operating state is rationalized for improving controllability. Can be used effectively and contributes greatly to preventive maintenance of each device.

[Brief description of drawings]

FIG. 1 is a diagram showing a concept of plant control based on a margin value.

FIG. 2 is a diagram showing an example of conventional plant control.

FIG. 3 is a diagram in which the margin value control of the present invention is adopted in the plant control of FIG.

FIG. 4 is a diagram showing a relationship between a process amount and an operation signal when performing margin value control.

FIG. 5 is a diagram showing a relationship between a margin value and a gain correction value when margin value control is performed.

FIG. 6 is a diagram showing a temporal change of a process amount, an operation signal, and an operation end state amount when performing margin value control.

FIG. 7 is a diagram showing an example in which a limit value of a process constituent device is variable for margin value control.

FIG. 8 is a diagram showing an example in which a change rate limit value of a process state quantity is variable for margin value control.

FIG. 9 is a diagram showing an example in which the permissible lifetime consumption of process constituent devices is variable for margin value control.

FIG. 10 is a diagram showing an example in which a permissible consumption amount of process constituent devices is variable for margin value control.

FIG. 11 is a diagram showing an example of an allowable operating region and a variable operating region of a control valve.

FIG. 12 is a diagram showing an example in which the margin value control system of the present invention is applied to a cooperative control system.

FIG. 13 is a diagram showing a temporal change in the process amount when the margin value control system of the present invention is applied to the cooperative control system.

FIG. 14 is a diagram showing a specific example when the margin value control system of the present invention is applied to a thermal power plant.

[Explanation of symbols]

1 ... Plant process unit, 2 ... Plant control unit, 3
... Process amount target value setting unit, 4 ... Process amount operation allowable limit margin value calculation unit.

Claims (5)

[Claims] Claim: What is claimed is: 1. A main machine that gives a final output of a plant, an auxiliary machine that is attached to the main machine to maintain the final output of the main machine, and has an operating end, and that operates the operating end of the auxiliary machine. In a plant control system consisting of a controller for controlling the process amount of the auxiliary machine to a predetermined value, the life consumption of the auxiliary machine is evaluated, and the adjustment parameter of the controller is variably changed depending on the remaining life, A control system for a plant, wherein a control end is operated according to an output of a controller. 2. A main machine for giving a final output of a plant, a plurality of auxiliary machines provided with the main machine to maintain the final output of the main machine, and having an operating end, and an operating end of the auxiliary machine. Then, in a plant control system comprising a controller for controlling the process amount of the auxiliary device to a predetermined value, a permissible operating amount per unit period in the subsequent operation of the plurality of auxiliary devices, and per unit number of times is calculated, A plant control system characterized in that the adjustment parameter of each controller is variably changed according to the remaining life until the value is exhausted, and the operating end is operated according to the controller output. 3. In claim 2, the calculation of the permissible amount of operation per unit period and number of times in the subsequent operation means that the equipment is renewed during regular inspection based on the remaining life of the equipment within the safe operation range. The control system of the plant is characterized in that the remaining lifespan is the same except for the above. 4. A main machine for giving a final output of a plant, an auxiliary machine provided with the main machine to maintain the final output of the main machine, and having an operating end, and an operating end of the auxiliary machine for operating. In a plant control system consisting of a controller that controls the process amount of auxiliary equipment to a predetermined value, in order to set the final output of the plant given by the main machine to a predetermined value, the control target values of the plurality of auxiliary equipment are obtained and supplemented. Coordinated control unit given to the controller for each machine, a margin value control unit that calculates the operating margin value of the auxiliary machine for each auxiliary machine, and corrects and controls the controller parameter of each auxiliary machine according to the operating margin value. A control system for a plant, comprising: 5. A main machine for giving a final output of a plant, an auxiliary machine provided for the main machine to maintain the final output of the main machine, and having an operating end, and an operating end of the auxiliary machine for operating. In a plant control system consisting of a controller that controls the process amount of auxiliary equipment to a predetermined value, in order to set the final output of the plant given by the main machine to a predetermined value, the control target values of the plurality of auxiliary equipment are obtained and supplemented. A coordinated control unit given to the controller for each machine and the operation margin value of the auxiliary machine are calculated for each auxiliary machine, and a specific operation margin value is selected from the obtained plural operation margin values, and the selected operation is performed. A control system for a plant, comprising a margin value control section for correcting and controlling a controller parameter of each auxiliary machine according to a margin value.