JPH0799246B2 - Boiler start control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a boiler start-up control device for controlling the start-up of a boiler device.

[Conventional technology]

To start the boiler, after the start preparation is completed, the fuel system is operated, the burner is ignited, and pressurization and temperature rise of the boiler are started. In this case, it is necessary to perform appropriate start-up control so as not to overheat each part of the boiler device or to generate an excessive thermal stress in the thick part. The conventional starting means will be described below with reference to the drawings.

FIG. 3 is a system diagram of a conventional boiler starting control device. In the figure, 1 is a water wall constituting a boiler furnace wall, 2 is a burner,
Reference numeral 3 is a boiler water supply pump for supplying water to the water wall 1. Four
Is a steam-water separator, which separates a steam-water mixture generated by heating the feed water on the water wall 1 into steam and moisture. 5 is a superheater that superheats the steam from the steam separator 4, 6 is a economizer that preheats the feed water from the feed water pump 3, and 7 is a turbine that is connected to a generator. A turbine control valve 8 is interposed between the superheater 5 and the turbine 7 and controls the amount of steam from the superheater 5 to the turbine 7.

Reference numeral 9 is a superheater bypass valve that allows steam from the steam separator 4 to escape to a condenser or the like. The superheater bypass valve 9 has a large amount of low-temperature steam flowing into the superheater 5 at the time of start-up, so
When the temperature rise at the outlet of the superheater 5 is hindered, such low-temperature steam is released to reduce the amount of steam passing through the superheater 5,
It has the function of raising the steam temperature at the outlet of the.

Reference numeral 10 is a turbine bypass valve that allows steam generated from the outlet of the superheater 5 to escape to a condenser or the like. This turbine bypass valve
10 has a function of letting out the generated steam when the temperature is not raised or increased to such an extent that the generated steam can be ventilated to the turbine 7, and further, even after the ventilation to the turbine 7, the flow rate of the vented steam is small. In this case, since it becomes difficult to control the steam pressure by the fuel input amount, it also has a function of contributing to the steam pressure control by letting the generated steam escape in this region.

11 is a steam pressure detector that detects the pressure of steam supplied from the superheater 5 to the turbine 7, 12 is a target pressure of the steam, that is, a steam pressure setter that sets a target steam pressure, and 13 is steam pressure setting It is a subtractor that calculates the difference between the value set in the container 12 and the value detected by the vapor pressure detector 11. Reference numerals 14 and 15 denote proportional integrators that proportionally integrate the pressure deviation signal calculated and output by the subtractor 13. A function generator 16 inputs the value detected by the vapor pressure detector 11 and outputs a predetermined value corresponding to this value. This function generator 16
Is an opening command signal for commanding the opening of the turbine bypass valve 10 for adjusting the steam pressure to an appropriate pressure.
17 also inputs the value detected by the vapor pressure detector 11,
It is a function generator that outputs a value corresponding to this value. The output signal from the function generator 17 is used as a superheater bypass valve 9 for discharging a large amount of low-temperature steam that prevents the temperature rise of the superheater 5.
It becomes an opening degree instruction signal for instructing the opening degree.

Reference numeral 18 is a signal switch equipped with terminals 18a and 18b and a switching piece 18c. Terminal 18a is a proportional integrator 14 and terminal 18b is a function generator.
16, the switching piece 18c is connected to the turbine bypass valve 10, respectively. 19 is a high signal selector, proportional integrator
The output signal of 15 is compared with the output signal of the function generator 17, and the larger signal is output to the superheater bypass valve 9. 20 is a fuel flow rate control valve for controlling the fuel supply to the burner 2, 21
Is an opening degree setting device that sets the opening degree of the fuel flow rate control valve 20 according to the number of ignitions of the burner.

The operation of the above apparatus will be described with reference to the time charts shown in FIGS. 4 (a) to 4 (e). FIG. 4 (a) is a change in the amount of fuel input over time, FIG. 4 (b) is a change in the opening degree of the superheater bypass valve 5 over time, and FIG. 4 (c) is a turbine bypass valve over time. 10 shows changes in the opening degree, FIG. 4 (d) shows changes in steam pressure with time, and FIG. 4 (e) shows changes in superheater outlet steam temperature with time. Time t ₀ is ignition time, time
t ₁ is the time when the pressure rise is completed, time t ₂ is the time when the temperature rise is completed, and time t ₃ is the time when the turbine is ventilated. Further, p ₀ is the initial steam pressure value, and p ₁ is the boost target value.

After the ignition at time t _0, the number of ignitions of the burner 2 is increased stepwise, and the opening signal of the opening setting device 21 controls the opening of the fuel flow rate control valve 20 accordingly, and the fuel injection amount is It gradually increases as shown in FIG. On the other hand, the signal switch 18 is in a state in which the switching piece 18c is switched to the terminal 18b side before the steam pressure reaches the boost target value p ₁ . Therefore, the opening of the turbine bypass valve 10 is controlled by the output of the function generator 16 corresponding to the steam pressure until the steam pressure detected by the steam pressure detector 11 reaches the boost target value p _1. After all, the steam pressure is uniquely determined.

Then, as shown in FIG. 4C, the opening degree of the turbine bypass valve 10 is controlled so as to release the increasing steam pressure before the turbine ventilation time t ₃ . Further, while the steam pressure is low, the saturation temperature of the steam is low, and low-temperature steam is supplied from the steam separator 4 to the superheater 5, so the output signal of the function generator 16 is the opening of the superheater bypass valve 9. Is generated, and accordingly, the opening degree of the superheater bypass valve 9 is increased as shown in FIG. 4 (b). As a result, low-temperature steam is released, the amount of steam passing through the superheater 5 is reduced, and the outlet steam temperature of the superheater 5 is increased.

After the steam pressure reaches the boost target value p ₁ , the signal switch 18
The switching piece 18c is switched to the terminal 18a side, and thereafter, the opening degree of the turbine bypass valve 10 is the boost target value p ₁ set in the steam pressure setter 12 and the actual steam detected by the steam pressure detector 11. By the signal that is proportional and integrated the pressure deviation signal with the pressure,
The control is performed as shown in FIG. Furthermore, after the completion time of pressurization t ₁ , the steam pressure is
If you raise it so that you can not escape at 10, proportional integrator
Since the output signal of 15 also becomes large, the high signal selector 19 selects the output signal, increases the opening degree of the superheater bypass valve 9 to release steam, and suppresses the rise of steam pressure.

[Problems to be solved by the invention]

Now, such a conventional device has the following three problems, which will be described in order.

(1) In the conventional device, it is difficult to set the optimum temperature rising / boosting pattern. Here, the optimum heating / pressurizing pattern refers to a starting mode in which the heating / pressurization is performed in the shortest time while suppressing the generation of thermal stress in the thick portion of the boiler device. By the way, generally, the most important thick parts in the boiler apparatus are the outlet header of the superheater 5 and the steam separator 4 (or drum).
Therefore, the optimum temperature rising / pressurizing pattern is, in other words, the rate of change in the outlet steam temperature of the superheater 5 that affects the thermal stress of the outlet header of the superheater 5 (hereinafter referred to as the rate of temperature rise).
And a steam pressure change rate (hereinafter referred to as a pressurization rate) that affects the thermal stress of the steam separator 4 (or the drum) via a saturation temperature change, the allowable changes in suppressing the generated thermal stress. It can be said that this is a mode in which the rate limit value is maintained at a high rate.

From this point of view, when looking at the above-described conventional device, the temperature rise rate and the boost rate in the conventional device are adjusted by the settings of the function generators 16 and 17, but in order to perform these settings, It is necessary to repeat the starting test of the actual can, which requires a lot of trouble and is troublesome.

Furthermore, when the steam pressure (initial pressure) at the ignition time t ₀ is different from the steam pressure at the time of adjustment at the time of start-up, a situation occurs in which the planned temperature rising rate and the pressure rising rate deviate. In order to prevent the adverse effect of such a shift, the function generators 16 and 17 in the conventional device are able to increase the temperature rise rate and the pressure rise rate at any stage of the temperature rise and pressure rise processes, regardless of the initial pressure at which they are started. It is set as a guideline that the rate does not exceed the limit value.
As a result, the temperature rising / boosting pattern is largely deviated from the optimum temperature rising / boosting pattern, and the starting time is considerably longer than that in the case where the optimum temperature rising / boosting is performed.

(2) In the conventional device, it is difficult to reduce the starting loss. In the boiler device shown in FIG. 3, when starting at a given temperature increase rate and pressure increase rate, the amount of injected fuel that passes through the fuel flow rate control valve 20, the opening degree of the superheat amount bypass valve 9, and the turbine bypass valve 10 The combination of the opening degrees is not uniquely determined. That is, for example, a large amount of fuel is injected into the burner 2 and the superheater bypass valve 9 and the turbine bypass valve
While there are combinations that extract a large amount of steam from 10,
The reverse combination also exists. Among these combinations, the combination of three that can maintain the given rate of temperature increase and rate of pressurization and minimize the opening degree of the fuel flow rate control valve 20 has the same start-up time. It is the operation with the lowest starting loss to achieve.

However, since the conventional device does not have a function of operating the superheater bypass valve 9, the turbine bypass valve 10 and the fuel flow rate control valve 20 in cooperation with each other, in order to reduce the starting loss,
There is no other way than adjusting the opening degree setter 21 and the function generators 16 and 17 individually. In reality, it is almost impossible to adjust these so that the starting loss is optimized while maintaining the above-mentioned optimum temperature rising rate and boosting rate.

(3) In the conventional device, even if the temperature rise and the pressure rise pattern become abnormal due to disturbance or the like, the correction operation for correcting this is not performed. That is, in the conventional device, although the rate of temperature rise, the rate of pressure increase, etc. are important state quantities that control the thermal stress in the thick portion of the boiler device, they do not have a means for measuring them and control Ueno is released. Is in a state.

For this reason, even if the temperature rise rate and the pressure rise rate deviate from the patterns planned at the time of adjusting the opening degree setter 20 and the function generators 16 and 17, for example, due to disturbance or the like, these cannot be corrected. Therefore, from this aspect, the opening setting device 2
0, When adjusting the function generators 16 and 17, it is necessary to plan the temperature rise rate and the pressure rise rate to be low in consideration of the margin for suppressing the generated thermal stress, which is an obstacle to shortening the startup time.

Further, conventionally, a control method of a power plant as described in JP-A-58-15703 has been proposed. This control method constructs a plant model by a mathematical method,
In the method of controlling an electric power plant by obtaining an estimated value (predicted value) for a predetermined parameter using this plant model, the difference between the measured value and the estimated value (predicted value) of the parameter is calculated by using the Kalman filter theory. Based on the above, the elements of the plant model are corrected. The target value obtained from the plant model and the measured value are compared, and proportional / integral (PI) control is performed based on the difference to determine the manipulated variables of various valves.

This control method is a combination of the plant model modification based on the Kalman filter theory and PI control. When this control method is applied to boiler start-up control, the effect of reducing the temperature rise / boost control deviation at start-up Yes, but
The effect of minimizing the total amount of fuel input when the boiler is started cannot be obtained. In other words, under the condition that the total amount of fuel input is the minimum, it is not possible to perform control for reducing the temperature deviation / pressurization control deviation, and therefore there is a difficulty in the economical aspect of boiler operation.

The object of the present invention is to eliminate the drawbacks of the prior art,
While keeping the thermal stress of the thick part such as the outlet header of the superheater to a minimum, it can be started in a short time under the condition that the amount of fuel input is small, which is excellent in economic efficiency and operability of the boiler. It is to provide a boiler start-up control device.

[Means for solving problems]

In order to achieve the above object, the present invention provides: a superheater 5, a first valve including a superheater bypass valve 9 that bypasses steam to the superheater 5, and steam from the superheater 5 to, for example, a turbine 7 Such as a turbine bypass valve
A second valve consisting of 10 and a fuel flow control valve 20 for controlling the amount of fuel supplied to the furnace
The present invention is intended for a boiler device provided with a third valve consisting of, a temperature detector 100 for detecting the steam temperature at the outlet of the superheater 5, and a pressure detector 11 for detecting the steam pressure of the boiler.

Then, the steam temperature signal detected by the temperature detector 100 and the pressure detector 11, the steam temperature change rate signal from the steam pressure signal, respectively, to calculate the steam pressure change rate signal, for example, a change rate calculating means consisting of signal differentiators 102, 103, In the superheater, for example, a target value setting means comprising a target value setting unit 108 for setting a temperature increase rate target signal necessary for reducing thermal stress in a thick portion such as an outlet header section, a boost rate target signal, and Temperature change rate control deviation by comparing the steam temperature change rate signal and the steam pressure change rate signal calculated by the change rate calculation means with the temperature increase rate target signal and the pressure increase rate target signal set by the target value setting means. A signal, a boosting rate control deviation signal, for example, a comparison means including a vector signal calculator 109, and a temperature rising rate control deviation signal and a boosting rate control deviation signal, respectively, are integrated, for example. And integrating means consisting vector signal integrator 110, constituted by a mathematical method, the current of the first valve 9, the second valve
10, a process model means comprising a process model 106 and a process state memory 107 for applying a predictive value after a fixed time based on the opening signal of the third valve 20, for example, a linear reguulator theory, and the process model Compensating the predicted value of the process model means, for example, based on the deviation between the predicted value calculated by the means and the measured value corresponding thereto, for example, a vector signal calculator 104 applying the Kalman filter theory and a process model modifier 105 Based on the process model correction means, the optimum predicted value from the process model means corrected by the process model correction means, and the integrated value of the control deviation from the integration means, the thermal stress of the thick portion of the superheater The optimum manipulated variable calculation that calculates the opening manipulated variables of the first valve, the second valve, and the third valve that can realize startup with the minimum fuel input by limiting It is characterized by having an optimum manipulated variable calculating means composed of the output device 111.

[Action]

As described above, the present invention is, for example, a process model means applying the linear reguulator theory, a process model correcting means applying the Karman filter theory, the thermal stress of the thick portion of the superheater is limited, and the fuel injection amount is increased. By combining with the optimal operation amount calculation means for calculating the opening operation amount of each valve that can realize the start with the minimum, while keeping the thermal stress of the thick part such as the outlet header of the superheater to a minimum, It is possible to start up in a short time under the condition that the amount of fuel input is small, and it is possible to provide a boiler start-up control device excellent in both economical efficiency and operability of the boiler.

〔Example〕

FIG. 1 is a system diagram of a boiler starting control device according to an embodiment of the present invention. The same parts as those shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

100 is a steam temperature detector that detects the temperature of the steam at the outlet of the superheater 5, and 101 is the superheater 5 in the combustion gas passage in the boiler.
Gas temperature detector to detect the temperature of combustion gas at the outlet, 102,10
Reference numeral 3 is a signal differentiator that differentiates the detection signals from 11,100 and outputs a change rate signal. Below 102,103,11,100,1
01 output signal in order of signal, signal, P signal, T signal,
Called the Θ signal. Vector when you want to handle these signals together , And that part is, P, T, Θ.

108 boost rate target value _r, NoboriAtsushiritsu target value _r, boost target value P _r, heating the target value T _r, superheater 5 exit gas temperature target value theta _r
Is a target setter that sets And the components are _{r 1} , _r , P _r , T _r , and Θ _r . 109 is Control deviation vector minus Vector signal subtractor to calculate Vector of each component of Is a vector signal integrator for calculating

On the other hand, the opening degrees of the valve 20, the valve 10, and the valve 9 are sequentially operated by the operation signals u ₁ , u ₂ , u ₃ , and when these signals are handled collectively, they are vectors. , And its components are u ₁ , u ₂ and u ₃ . 106 is the process model and is the same as when operating an actual plant At the time Is the predicted value of A vector with Is output. here Indicates that each is a predicted value of the original variable. Ten
When the process model 106 calculates a predicted value, 7 is a process state memory that sequentially stores the previous variable value in order to deal with the calculation of a variable that depends on the past history such as the integral action in the process. is there. The variables stored are chosen sufficiently to uniquely represent the morphology of the system that depends on past history. Generally, it is sufficient that the number is greater than or equal to the order of the process model, and a vector having these variables as components is a state variable vector. Is the value on the model and is the predicted value of the state quantity of the actual plant. Will be treated with.

The process model 106 is a state variable vector at time k. State represented by In general, the subscripts of vectors below represent time points) Changes to Is stored in the process state memory 107, which is new at the next time point l (= k + 1). Is taken out as the process model 106. 104 is To represent the prediction error of the process model 106 Is a vector signal subtractor that outputs The components of are _ε , _ε , P _ε , T _ε , and Θ _ε , which correspond to the prediction errors of P, T, and Θ, respectively. 105 is Accordingly, the process model corrector corrects the process model 106. 111 is Received Is an optimum manipulated variable calculator for calculating. Here, the components of Z are _z , _z , P _z , T _z , and Θ _z in this order, and similarly, P,
It corresponds to the integral value of the control deviation of T and Θ.

Next, the operation of each component will be specifically described.

1) Operating ends 9,10,20 The operating ends 20,10,9 receive the operating signals u ₁ , u ₂ , u ₃ and become actual opening υ ₁ , υ ₂ , υ ₃ . For the actual opening, set the reference opening υ ₁ ⁰ , υ ₂ ⁰ , υ ₃ ⁰ when the u ₁ , u ₂ and u ₃ signals are 0,
Operate to satisfy the following relationships.

However, each vector has the following components.

here How to give will be described later.

2) Detection ends 102,103,11,100,101 Detection signals from the detection ends 102,103,11,100,101, P, T,
Θ and corresponding physical quantity of actual plant ^* , ^* , P ^* , T ^* ,
The value of Θ ^* satisfies the following relationship, where the reference physical quantities when the P, T, Θ signals are 0 are ⁰ , ⁰ , P ⁰ , T ⁰ , Θ ⁰ , respectively.

However, each vector has the following components.

here How to give will be described later.

3) Process model 106 Since a boiler plant is a physical process, phenomena can generally be described by mass balance, energy balance, and momentum balance. For example, the process that occurs inside the heat transfer tube can be expressed by a one-dimensional partial differential equation, and the mass balance is as follows.

Where S is the cross sectional area of the heat transfer tube, ρ is the fluid density in the heat transfer tube, and G is
Is the mass flow rate of the fluid in the heat transfer tube, t is the time, and x is the distance along the heat transfer tube.

In addition, the energy bunlas is the following formula.

Where u is the internal energy of the fluid in the heat transfer tube, H is the enthalpy of the fluid in the heat transfer tube, q is the amount of heat transfer per unit length that the fluid receives from the wall of the heat transfer tube, and other variable names are (5). It is similar to the formula.

And the momentum balance is

Here, p is the pressure of the fluid inside the heat transfer tube, F is the external force such as gravity or the frictional force of the tube wall, and other variable names are equation (5),
It is similar to the equation (6).

Even if the heat transfer tube of the boiler is divided into multiple sections along the fluid flow, and the internal fluid state is assumed to be uniform within the section, the behavior of the process is simulated if the number of divisions is large. Is known to be sufficient above,
Based on this assumption, equations (5), (6), and (7) can be transformed into simultaneous ordinary differential equations. This modification will be described by taking the j-th section as an example along the fluid flow of the equation (5). Here, assuming that the length of the j-th section is Δx, the equation (5) is as follows.

Here, the superscript j indicates that it is the value of the jth section, and so on. Further, the equation (8) can be modified as follows.

However, v _j is the volume in the heat transfer tube of the j-th section, and has the following relationship.

v _j = S ^j · Δx ^j (10) The steam pressure change rate ^j of the j-th section can be calculated as follows.

Equation (9) is used in this modification. Further, K depends on the physical property value of water, and can be obtained by, for example, a steam table issued by the Japan Society of Mechanical Engineers.

Similar to the space division described above, the time flow is discretized,
A method of converting a differential equation into a difference equation is also widely used, and it is known that the behavior of a process can be simulated with sufficient accuracy if the discretized time interval is small. By discretization, the vapor pressure of the j-th section is obtained as follows.

As described above, the concept of space and time division is the same (6)
It can also be applied to equations (7), and by this, all behaviors of a process can be described by a group of simultaneous algebraic equations. This group of algebraic equations is generally represented in the following form by vector representation.
symbol Indicates the value predicted by the model and is attached separately from the value on the actual plant.

here Is an input vector at the time point k, and has, for example, the value of a variable indicating the operating end opening degree, the boundary condition, etc. as a component.

Is the state vector at time k + 1 and is the input vector at time k And the state vector at time k It has a component of the class of P ^j _{k + 1 in} Eq. (13).

Is an observation vector, which has a value that can be observed by connecting the detector to the process.

Applying the above theory to the boiler device that is the subject of the present invention,
Shown in equations (2) and (4) Apply to (14) and (15) to develop the following theory.

First, in equation (2) Set the minimum position of the operating end as.

Where υ _1min is the minimum opening of the fuel flow control valve 20 due to burner turndown limitation, etc., and υ _2min and υ _3min are the opening of the turbine bypass valve 10 and the superheater bypass valve 9 considering warming and drainage. It is the lowest value.

Given by equation (16) Is applied to equation (14) to satisfy the following equation To calculate.

This is as follows And the Newton-Raphson method may be applied. That is the next development.

Suitable initial value Until the values of each component of are sufficiently small and can be regarded as 0 (zero vector) Ask for.

After the required iteration And

Here, a new state variable P _c is defined by the following equation.

Substituting equations (1) and (18) into equation (14).

When Taylor's expansion is performed and the higher-order terms are omitted, (1
Equation 9) is as follows.

Here, using the relationship of equation (17), equation (20) is expressed as follows.

Similarly, in equation (4) Is defined by the following formula.

Substituting equations (3) and (18) into equation (15), It is as follows when Taylor is expanded around.

This can be expressed as follows using the relation of Eq. (24).

The conclusions of the above discussion are equations (21) and (26), and the process model 106 results in calculating both equations of conclusions.

4) Process model modifier 105 Plant state quantity predicted value by process model 106 It must be considered that the P _ck of the actual plant is generally different. This is a process model 10
This is because it should be considered that various disturbances not considered in Eqs. (21) and (26) in 6 are added. Therefore, the characteristic of the actual plant is expressed by the following equation.

That is, assuming the same structure as the process model 106 as the behavior of the actual plant, a phenomenon that cannot be explained by the assumption is assumed to be a noise vector. It can be considered that they are added together at the stage of obtaining the observation vector. In the present invention, the purpose of the process model modifier 105 is obtained from an actual plant. Predicted value in process model 106 based on And the optimal estimate of R _ck in Eq. (28) Is calculated using the Kalman filter theory.

In order to properly control the plant, it is necessary to correctly know the state quantity P _{ck of the} process occurring in the actual plant, but of course this cannot be directly measured and is shown in equation (29). It is only possible to know through The operation of calculating is an important function.

The following form is assumed as an equation for estimating.

Less than Will be explained as follows.

The above equation is the estimation error vector Is an unbiased estimator for which the mean of is 0, and The minimum variance estimator that minimizes the variance of Ask for.

Is given by

Applying equation (29) to equation (30) gives the following.

First The condition that is an unbiased estimator of P _ck can be expanded as follows using Eqs. (31) and (33). here Is the average of, and the symbol ￣ is used below to mean the average. The operator E means an operation that takes an average over the entire distribution of the acting random variable, x is the random variable, (w) the distribution function is P (w), and the probability space is {Ω, u, p}. Then Ex = ∫ _Ω
It is defined as x (w) p (dw).

Yotsute It is shown that must be given by

Next, since it is the minimum variance estimator, And derive the condition that minimizes To decide. Equation (32) is developed below using equations (33) and (35).

However The variance is calculated as follows.

As is clear from the form of equation (36), when equation (39) holds, the first term disappears, leaving only the second term, and equation (40) takes the minimum value.

The above conclusions are given by equations (39) and (35) If you ask It means that the formula (30) for obtaining is established. Here, it can be transformed as follows by the so-called inverse matrix lemma.

Substituting Eqs. (42) and (35) into Eq. (30) gives the conclusion formula.

Next, the formula (43) of the conclusion is used to calculate sequentially. Where k =
At time 0 Is known as an initial value, Of course, it is an unspecified amount, but it is economically statistical It is possible to understand and use these values to proceed with the discussion. When k = 0, the following is obtained from equations (41) and (43) Is required.

If the same theory is performed with k = k, in this case, equations (41) and (4
3) in the formula Is unknown, but k = k-1 If is known, the knowing calculation can be performed as follows. Ie Is already known as an initial value, so that the value at k = k is also obtained.

According to the teaching of Kalman filter theory, k = k-
Optimal estimator in 1 And get It is known that can be obtained by substituting in the equation (21) forming the process model 106.

As well Then it becomes as follows. Formulas (46) and (28) are used during expansion.

It appears during the development of the above formula Are each In the case of the present invention, Is the output of the optimum manipulated variable calculator 111, as will be described later,
Since the value can always be specified, it is as follows.

Therefore Is shown below.

Calculated by equation (46) Optimal estimator to be obtained by substituting in (43) To get The variance of the error at this time is Was calculated by equation (49) Since it corresponds to, it becomes the following formula.

To summarize the above theory, the function of the process model corrector 105 is to use the equations (49) and (50) to calculate the process model
106 outputs To estimate the optimum plant state quantity Will be required.

However, there are the following relationships.

here Is calculated by the equation (21) in the process model 106.

5) Vector signal subtractor 104 The above equation (53) is calculated.

6) Process state memory 107 Calculated using process model corrector 105 and process model 106 at time point k Is stored as is until time point k + 1. In this operation, when the Z transform is represented by the calculator z, the relationship between the input r and the output s of the process state memory is expressed by the following equation.

z (s) = z (r) · Z ^-1 (54) 7) Target setter 108 Setting the boost rate to reduce the thermal stress of the steam separator 4.
_{r 1} , a temperature rise rate setting _r 1 set for reducing thermal stress at the outlet of the superheater 5, a boost target value P _r , a temperature rise target value T _r , and a furnace outlet gas temperature target value Θ _r are set. These are collectively set vectors Is output as.

8) Vector signal subtractor 109 Calculates the following formula.

9) Vector integrator 110 Diagonal matrix determined by adjustment The following formula is calculated using.

10) Optimal manipulated variable calculator 111 As described above, in the present invention, the actual plant is considered to be governed by the following equation.

But in fact, the observation vector Is the noise due to the disturbance or the deviation between Eqs. (57) and (58) and the actual plant characteristics as shown in Eq. (29). However, the process model corrector By calculating It has already been explained that it should be handled in place of.

Now, the function of the optimum manipulated variable calculator, which is the center of the present invention, will be described below. The operation of the vector signal subtractor 109 and the vector integrator 110 is represented by the following expression, which is a combination of the expressions (55) and (56).

The dimensions of each vector and matrix are as follows.

However, the embodiment of FIG. 1 corresponds to p = 1 and m = 3.

The following equation is obtained from equations (59) and (58).

Focusing on Eqs. (57) and (60), the following matrix and vector are defined.

According to the above definitions, Eqs. (57), (58), and (59) are reduced to the following two equations.

Concretely here The components of are shown below.

Consider the following evaluation function.

During the above formula Is a weight matrix shown in the following equation.

The optimum manipulated variable calculator 111 minimizes the value of J according to equation (70) under the constraint conditions of equation (67). To calculate. Here, q _{1 to} q ₅ are non-negative weighting factors with respect to the integral values of the control deviations of P, T, and Θ, respectively, and the larger the value, the smaller the corresponding deviation. In this example, the target values of P and T are
Given _{r 1} and _{r 2} , it is particularly important to control the real plant to this value, so q ₁ and q ₂ must be chosen large. Similarly, r ₁ , r ₂ and r ₃ are the fuel flow control valve 20 opening u ₁ and
Turbine bypass valve 10 opening u ₂ , superheater bypass valve 9 opening
It is a weighting coefficient with respect to deviations of the reference values υ ₀ ¹ , υ ₀ ² , and υ ₀ ³ of the respective openings of u ₃ , and in the present embodiment, since the aim is to start the fuel injection amount as low as possible, it is necessary to select r _{1 as} well. There is.

The last constraint condition of (67) Since the term of is given from the outside and has nothing to do with the process structure, from the linearity of Eq. (67), the following theory In the case of, do not lose generality as a representative. Therefore, the function of the optimum manipulated variable calculator 111 minimizes J _L in the following equation. Result in seeking.

The minimum condition of Eq. (73) is as follows.

If we use the relation of equation (68), Can be converted to P _ck , the following three equations are derived.

k = 0,1, ... N-1 (78) When k = N, only the following formula is established.

From equation (72) Is a diagonal matrix and the inverse matrix Since it is clear that there exists, the following equation is obtained from the equations (75) and (76).

Called here Rikkatsu conversion If we make the following assumptions regarding Is given in the form of a feedback back of P _ck , and can meet the purpose of the optimum manipulated variable calculator 111.

Substituting equation (81) into equation (75), the following equation is obtained.

Substituting _Eqs . (80) and (81) into (77) and solving for P _{ck + 1} , the following equation is obtained.

Substituting the equation (83) into the equation (82), the following equation is obtained.

The conditions for _{satisfying the} equation (84) for any P _ck are as follows.

From equations (79) and (80) Is required.

Therefore, after that, using equation (85), K = N-1, N-2, ... Can be calculated.

Determined above By substituting into equation (81) and substituting into equations (75) and (80), the optimum manipulated _variable to be obtained can be obtained as follows if the state quantity vector P _ck is known.

As described above, the P _ck of the actual plant is an amount that cannot be directly measured, but the process model 106 and the process model modifier 105
Optimal estimator using The optimum manipulated variable can be calculated as follows using this.

here Is given by

(87) and (88) are the conclusion formulas of the optimum manipulated variable calculator.

FIG. 2 shows the starting characteristics of the plant when the present invention is applied. The steam pressure rise, steam temperature rise, fuel injection amount, turbine bypass valve opening, superheater bypass valve opening are shown in order from the top. It shows the change. In height each time point in FIG hatched portions, respectively correspond to _{z, z, u 1, u} 2, u 3, the former two are Vector components, the latter three It is a vector component.

(70) expression of J is _{z, z,} a sum of squares of _{u 1, u 2, u 3} , since the present invention has been reduces to searching the procedure to minimize J, these hatched It is possible to set the weighting factors q _{1 to} q ₅ and r _{1 to} r ₃ in the equations (71) and (72) that act to reduce the area of the part, and which of the shaded parts is preferentially decreased. . Therefore, according to the present invention, FIG.
It is possible to perform the start control so that the shaded portions of (b) and (c) are made small, and this state is exactly the operation method of the minimum fuel injection amount that satisfies the given temperature rise rate and pressure increase rate.

Therefore, by applying the present invention, it is possible to configure the boiler start-up control device that can realize the shortest time start-up with the optimum fuel injection amount while limiting the thermal stress in the thick-walled part of the boiler.

[Brief description of drawings]

FIG. 1 is a system diagram of a control device according to an embodiment of the present invention, and FIG.
FIG. 3 is a characteristic diagram showing a starting characteristic when the present invention is applied,
FIG. 4 is a system diagram of a conventional control device, and FIG. 4 is a characteristic diagram showing start-up characteristics when the conventional technique is applied. 100 …… Steam temperature detector, 101 …… Gas temperature detector, 102,
103 ... Signal differentiator, 104 ... Vector signal subtractor, 105
…… Process model modifier, 106 …… Process model, 1
07: Process state memory, 108: Target value setter, 109
…… Vector signal subtractor, 110 …… Vector signal integrator, 111 …… Optimum manipulated variable calculator.

Claims (1)

[Claims] 1. A superheater (5), a first valve (9) for bypassing steam to the superheater (5), and the superheater (5).
Second valve (10) for extracting steam from the reactor to other than its main supply destination, and a third valve (2) for controlling the fuel supply amount to the furnace.
0), a temperature detector (100) for detecting the steam temperature at the outlet of the superheater (5), and a pressure detector (11) for detecting the steam pressure at a predetermined portion of the boiler. Change rate calculation means (102, 103) for calculating a steam temperature change rate signal and a steam pressure change rate signal from the steam temperature signal and the steam pressure signal detected by the temperature detector (100) and the pressure detector (11), respectively, and a superheater. Target value setting means (108) for setting the temperature increase rate target signal and the pressure increase rate target signal necessary for reducing the thermal stress in the thick wall portion of the steam generator, and the steam temperature calculated by the change rate calculating means (102, 103). A change rate signal, a steam pressure change rate signal, and a temperature rise rate target signal set by the target value setting means (108),
A comparing means (109) for comparing the boost rate target signal with the boost rate control deviation signal and the boost rate control deviation signal, and an integrating means for integrating the ramp rate control deviation signal and the boost rate control deviation signal. (110) and a mathematical method, and the predicted value after a certain time based on the opening signals of the current first valve (9), second valve (10), and third valve (20) Process model means (106,
107) and the process model correction means (104,105) for correcting the predicted value of the process model means (106,107) based on the deviation between the predicted value calculated by the process model means (106,107) and the corresponding actual measured value. And the superheater (5) based on the optimum predicted value from the process model means (106, 107) corrected by the process model correction means (105) and the integrated value of the control deviation from the integration means (110). ) Opening operation of the first valve (9), the second valve (10), and the third valve (20), which can limit the thermal stress in the thick part and realize the start with the minimum fuel injection amount. A boiler start-up control device comprising: an optimum manipulated variable calculating means (111) for calculating a quantity.