JPS62248902A - Controller for temperature of steam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a steam temperature control device.

[Prior Art] For example, in a boiler of a fire-fired power plant, when changing the boiler steam temperature, the flow rate of fuel supplied to the boiler is adjusted, but after changing the amount of fuel'a, the steam temperature is affected. Until then, there is a response delay (hereinafter referred to as dead time), and to deal with this dead time, a Smith predictor has conventionally been used.

[Problems to be Solved by the Invention] However, when using the Smith predictor, it is good if there is no variation in the dead time, but if the dead time varies, there is a limit to the adjustment of the controller parameters. The steam temperature may diverge and become unstable.

The present invention has been made in view of the above-mentioned circumstances, with the object of making it possible to easily adjust the parameters of the controller and to stabilize the steam temperature.

[Means for Solving the Problems] The present invention provides a boiler controlled system equipped with a control valve that controls the flow rate of fuel supplied to the boiler, and a boiler controlled system including a control valve that controls the flow rate of fuel supplied to the boiler. A Smith predictor outputs a correction signal to eliminate dead time until the temperature reaches and a dead time adjusting means for adjusting the dead time of the transfer function of the boiler controlled system modeled in the Smith predictor when the dead time of the boiler controlled system changes. There is.

[Operation] A command signal to be given to the control valve is obtained in the control device based on the measured steam temperature, the preset steam temperature, and the correction signal from the Smith predictor, and the control valve receives the command signal from the control device. The opening degree is adjusted by the command signal to control the fuel flow rate supplied to the boiler, and when the dead time of the boiler controlled system changes, the transfer function of the boiler controlled system modeled by the Smith predictor The dead time is adjusted.

[Example] Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which 1 is a boiler, 2 is a fuel supply pipe to the boiler 1, 3 is a steam pipe for sending steam from the boiler 1, and 4 is a midway part of the fuel supply pipe 2. 5 is a steam temperature detector for detecting the temperature of steam flowing through the steam pipe 3; 6 is a conventionally known control device including a controller, an adder, etc.; and 7 is a conventionally known Smith predictor. , 8
Delay time measuring device, 9 steam humidity setting device, io, i
1 is an adder, and the steam temperature signal y (k) detected by the steam temperature detector 5 can be added to the adder 10 and the dead time measuring device 8; The steam temperature signal y (k) from 5 and the dead time correction signal from the Smith predictor 7 can be added and applied to the control device 6. Further, the output from the control device 6 and the minute input signal (random noise) u(k) from the dead time measuring device 8 are added to the adder 11, and the signal from the adder 11 is used as a control signal. The signal is fed to the control valve 4 as a signal and can also be fed back to the Smith predictor 7. Furthermore, the dead time measuring device 8 can send a dead time correction signal to the Smith predictor 7.

The Smith predictor 7 is for performing control to eliminate dead time when there is dead time in the boiler controlled system, and the details are shown in FIG. 2. Therefore, the Smith predictor 7 has a model G' (S) of the transfer function of the boiler controlled system that does not include dead time, and a model G' (S) of the transfer function of the boiler controlled system that includes dead time. )
e −”” is given.

The dead time measuring device 8 measures the time (dead time) until the control valve 4 opens and closes according to the command from the adder 11 and the temperature of the steam flowing through the steam pipe 3 settles to a fuel flow rate corresponding to the degree of opening and closing of the control valve 4. The details are shown in Figure 3.

The dead time measuring device 8 includes a random noise generating device 12 that generates disturbance, and a parameter calculating device 1 for an autoregressive model.
3. It is composed of a parameter comparison device 14, a dead time display device @15, etc., and a random noise generation device 12 generates random noise u(
k) (see FIG. 5) to the control valve 4 and the parameter calculation device 13, and the parameter calculation device 13 adds the random noise u (k) and the steam temperature signal from the steam temperature detector 5@ y(k) (see Figure 6) and calculates each coefficient from the autoregressive model. It is for calculating the dead time by comparing the magnitude relationship of parameters from each coefficient, and the dead time display device 15 is for displaying the determined dead time, and the determined dead time is as described above. can be given to the Smith predictor −〇−7.

The boiler steam temperature is set in advance to the control device 6 by the setting device 9, and the signal y(k) of the steam temperature in the steam pipe 3 detected by the steam temperature detector 5 is sent to the adder 10 and the dead time measuring device 8. , and the Smith predictor 7 generates a model G of the transfer function in the case where there is no dead time of the boiler control system.
The deviation between the signal multiplied by (S) and the signal multiplied by the transfer function model G'(S)e''°8 when there is a dead time is calculated, and the signal of the deviation is added to the adder 10. , in the adder 10, the deviation signal and the signal y(k) are added and given to the control device 6, and the control device 6 combines the signal from the adder 10 and the steam temperature set by the setting device 9. The deviation is determined, and the controller in the control device 6 adjusts it to an adjustment signal proportional to the size of the deviation, and then sends it to the adder 1.
1, and on the other hand, the adder 11 receives arbitrary random noise u (k
) is given, and a signal to which the adjustment signal and random noise u (k) are added is output from the adder 11 as a command signal and given to the control valve 4, the immediacy of the control valve 4 is adjusted, and the signal is added to the fuel supply pipe. 2 to the boiler is adjusted, and finally the steam temperature in the steam pipe 3 is controlled.

The output signal from the adder 11 is also applied to the Smith predictor 7, and as described above, the Smith predictor 7 calculates a model G' of the transfer function in the case of no dead time of the boiler controlled system.
The deviation of the signal multiplied by (S) and the transfer function model G' (S) e-"3 when there is a dead time is determined and added to the adder 10, and the same process as described above is performed. Control takes place.

The dead time measuring device 8 calculates the dead time, and when the dead time changes, the dead time L of the transfer function model G'(S)e-"8 of the Smith predictor 7 is adjusted. For example, if the fuel flow rate supplied to the boiler is
When the steam temperature changes as shown in Figure (A), the steam temperature in the steam pipe 2 changes as shown by the curve Δ in Figure 3<D) due to the dead time, but by providing the Smith predictor 7, the steam temperature can be As shown by curve B in Figure 3 (b), it is possible to change the dead time without any dead time, and even if the dead time fluctuates, stable control is possible by having the dead time measuring function.

Next, to explain in detail the operation of the dead time measuring device 8, random noise u (k) is given to the boiler controlled system from the random noise generator 12 to the adder 11 and the parameter calculating device 13, and the steam Temperature detector 5
The steam temperature in the steam pipe 3 is then applied to the parameter calculation device 13 as a signal '1/(k). Here, the object to be measured of the signal V(k) (one human power and one output) corresponding to the time rung noise u (k) can be expressed as follows using an autoregressive model.

Here, m: the order of the autoregressive model; discrete time e(k); noise or error aI #bi: If the sampling period of each m coefficients or data is At, then the elapsed time t=1, 6
It is represented by t. Then, the parameter calculation device 13 converts the coefficients ai and bl of equation (1), and calculates the coefficients ai and bl using the recursive least squares method expressed as such that the noise or error e (k) is minimized. It is determined. Here, J
is the evaluation function. However, the order m of the autoregressive model is set in advance in the parameter calculation device 13 to a number as large as the measuring person (a number sufficiently larger than the dead time and expressed as m>>L/At).

After the coefficients ai * b t of the autoregressive model are determined, each coefficient ai e bi is added to the parameter comparison device 14, and the parameter comparison device 14 compares the magnitude relationship of each coefficient, and calculates the dead time from this magnitude relationship. is calculated. In other words, if there is a dead time, b u(k−i
), bl, b2 . ... is small, and bl becomes sufficiently larger than bl from the time when the dead time is exceeded.

Therefore, lb+ l << lb+ 1...
・Find i for which 0 holds true, and calculate the dead time from L = (i-1) half A t ・(v). The obtained dead time is given from the dead time display device 15 to the Smith predictor 7, and when the dead time changes, the transfer function model G' of the Smith predictor 7 is applied.
(S) The L of O-”8 is adjusted.

Note that the present invention is not limited to the above-mentioned embodiments, and that the dead time may be determined in advance by a test and the dead time may be adjusted based on the result, within the scope of the water saturation invention. Of course, various changes can be made.

[Effects of the Invention] According to the steam temperature control device of the present invention, it is possible to easily adjust the controller parameters for adjusting the dead time until the steam temperature changes to a predetermined temperature after changing the fuel system. Various excellent effects can be achieved, such as stable control without temperature divergence and the ability to reduce the range of steam temperature fluctuations.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the steam temperature control device of the present invention, FIG. 2 is an explanatory diagram of the Smith predictor in the device of FIG. 1, and FIG.
A) is a graph when the fuel flow rate is changed using the device in Figure 1, Figure 3 (B) is a graph showing how the steam temperature changes when the fuel flow rate is changed, and Figure 4 is a graph showing the change in steam temperature when the fuel flow rate is changed. An explanatory diagram of the dead time measuring device in the device shown in the figure. Figure 5 is a graph showing the relationship between the input signal input to the controlled system and the parameter calculation device and time. Figure 6 is the flow from the controlled system to the parameter calculation device. 3 is a graph showing a relationship between an applied output signal and time. In the figure, 1 is the boiler, 2 is the fuel supply pipe, 3 is the steam pipe, 4
is a control valve, 5 is a steam temperature detector, 6 is a control device, 7 is a Smith predictor, 8 is a dead time measuring device, 9 is a setting device, 10
．． 11 indicates an adder.

Claims (1)

[Claims] 1) A boiler controlled system equipped with a control valve that controls the fuel flow rate supplied to the boiler, and a correction signal that eliminates dead time until the steam generated in the boiler reaches a predetermined temperature after changing the fuel flow rate. The dead time of the output Smith predictor, the control device that obtains the command signal to be given to the control valve from the measured steam temperature, the correction signal from the Smith predictor, and the preset steam temperature, and the dead time of the boiler controlled system. 1. A steam temperature control device comprising a dead time adjustment means for adjusting dead time of a transfer function of a boiler controlled system modeled by the Smith predictor when the temperature changes.