JPS606448B2 - Calorie correction method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an automatic plant control system (AP) for a supercritical pressure boiler.
The present invention relates to a calorie correction method and device when changing fuel in C).

Since supercritical pressure boilers do not have drums, the process response is far greater than that of drum-shaped boilers.

Therefore, when controlling a thermal power plant using a supercritical pressure boiler, a turbine control device and a boiler control device (ABC) are used.
) is used in conjunction with an automatic plant controller (APC). The conceptual structure of APC is as shown in FIG. 1, and the generator output command becomes the master signal for all control loops while being subjected to various corrections. ABC of drum type boiler
In a supercritical pressure boiler, the feedwater control loop has almost no interference with steam pressure or steam temperature, so it can be treated as an independent loop.However, in a supercritical pressure boiler, there is strong interference between the feedwater amount and steam pressure to steam temperature, and the feedwater control loop and the fuel control loop cannot be separated. The water supply control loop and the fuel control loop are linked through a water-fuel ratio controller that corrects the water-fuel ratio, and when the process is stabilized, the ratio of the water supply flow rate to the fuel flow rate, that is, the water-fuel ratio, is always constant. The plant is designed so that the water-fuel ratio at this time is 1. When coal is used as fuel, a value obtained by multiplying the amount of coal supplied by the calorie value of coal is used as the fuel flow rate signal.

If the quality of coal changes during plant operation, its calorie value will match the initial setting value, and the operating point of the water-fuel ratio controller will become biased in an attempt to absorb this error, resulting in poor APC controllability. Problems arise in maintaining the In order to avoid biasing the operating point of the water-fuel ratio controller,
It is possible to correct the calorie value according to changes in the quality of the coal, but ``If the calorie value is suddenly changed, the output of the fuel control loop will suddenly change and cause a disturbance to the process. It takes a long time to change the value.An object of the present invention is to provide a method and apparatus for quickly correcting the calorie value without disturbing the process.

According to the present invention, the outputs of the water-fuel ratio controller and the oxygen amount controller are changed in accordance with the calorie value correction.

The present invention will be explained below with reference to the drawings.

FIG. 2 is a conceptual block diagram of an apparatus to which the method of the present invention is applied. In Fig. 2, M is a water-fuel ratio controller;
2 is an oxygen amount controller, M3 is a fuel flow controller, and M4 is an air flow controller. These controllers have proportional/integral functions, manual/automatic cutting functions, and output tracking functions. The calorie setting device on the side is composed of, for example, an analog memory (integrator), and its contents can be changed in accordance with increase/decrease command signals A and B. Hato~M8 is a chicken calculation. The water-fuel ratio controller M outputs a water-fuel ratio correction signal k based on the difference between the steam temperature detection signal and the set value.

The water-fuel ratio correction signal k is multiplied by the master signal Z applied from the previous stage in a multiplier M6. The master signal Z is the same as the master signal, that is, the water supply command, given to the water supply flow rate control loop at the previous stage. The output signals k and Z of the cockpit are given to the fuel flow controller M3 as a fuel command signal FFD. The fuel flow rate controller M3 receives the coal supply amount x and the calorie setting value k2 from the chicken calculator M7.
x is given as the fuel flow signal FF. The fuel flow controller M3 outputs a fuel flow control signal based on the difference between these two signals. The fuel command signal FFD and the fuel flow rate signal FP are given to the water-fuel ratio controller M as correction signals. When the tracking function is activated, the water-fuel ratio controller M converts the fuel command signal FFD into the fuel flow rate signal FF.
The oxygen amount controller M2 outputs an oxygen amount correction signal k3 based on the difference between the signal detecting the oxygen amount in the fuel gas and the set value.

The chicken calculator M8 inputs the oxygen amount correction signal k3 to the fuel amount command signal FFD.
Find the air command signal AFD (;k, k3Z) by multiplying by
This is given to the air flow controller M4 as a master signal. The air flow rate detection signal y is given to the air flow controller M4 as the air flow rate signal AF. The air flow controller M4 outputs an air flow control signal based on the difference between these two signals. Air command signal AFD and air signal A
F is also given as a correction signal to the oxygen amount controller M2. The oxygen amount control M2 operates to match the air command signal AFD with the air signal AF when the tracking function is activated. The operation of the device configured in this way is as follows.

Normally, each controller performs proportional/integral operations in an automatic state, and controls the fuel flow rate and air flow rate in accordance with the master signal. If coal having the calorie set in the calorie setter M5 is supplied to the boiler and the process is stabilized in that state, the water-fuel ratio becomes 1 and the water-fuel ratio controller M. The output signal will be 50% of the rated output. When the quality of the coal changes and its calorie differs from the set value k2, the energy added to the water changes and the steam temperature changes, so the output signal of the water-fuel ratio controller M changes, which causes the output signal of the fuel flow controller M3 to change. The output signal changes to change the amount of coal fed, canceling out energy changes due to calorie changes.

When the process settles again by this operation, the output signal of the water-fuel ratio controller M has changed from the previous settling state (50%) by the amount that the calorie of the coal has changed. The output signal of the water/fuel ratio controller M becomes smaller than 50% when the calorie increases, and becomes larger than 50% when the calorie decreases. Also, the output signals of the oxygen amount controller M2 and the air flow controller M4 have new values. At this time, the following relationship holds on the input side of the fuel flow controller M3 and the input side of the air flow controller M4, respectively: k, Z: k2×
{1) k, k3Z=y
(2) In this state, the setting value k2 of the calorie setting device M5 is corrected according to the quality of the coal.

At this time, the output signal of the water/fuel controller M is corrected at the same rate, and the output signal of the oxygen amount controller M is corrected at the opposite rate. That is, when k2 is k'2, k
, to k.・k'2/k2 and k3 as k3・k2/k'
Set it to 2. Then, FFD: k basket Z ■ FF=k'2x{41
(4) side=k. basket. It becomes k score 2z (5).

Fuel flow control.

The air flow controller M3 operates based on the difference between FFD and FF, and the air flow controller M4 operates based on the difference between AFD and y, but these differences are determined by k. Kago Z-k'2X = Pure k Z-
Ship = o (6lk. basket, k3 horse Z-y: k, k3Z-y
=o (7). That is, the deviation input signals of both controllers are both zero. Therefore, the output signals of both controllers do not change and no disturbance is applied to the process. That is, even if the calorie correction is performed quickly, no disturbance is caused to the process. , The output signal of the water-fuel ratio controller MI increases or decreases in response to the increase or decrease in the calorie set value, but before correction, this is smaller than 50% when the calorie is high and larger than 50% when the calorie is low. Therefore, the above correction returns the output signal of the water/fuel controller to 50%.

Therefore, the operating point of the water-fuel ratio controller M is returned to its original state and good controllability is maintained. Water fuel ratio controller M
, and the correction of the output signal of the oxygen amount controller M2 is as follows:
This can be easily done by using the tracking function.

That is, when the water-fuel ratio controller M is placed in the tracking mode, the output signal k is changed so that the fuel command signal FFD matches the fuel flow rate signal FF, so if the output signal when they match is k', then k ′, Z=k′2
× (8), but '
1} From formula, Z=various X (9) k′・=k. q■ Similarly, if the output signal of the oxygen amount controller M2 is k'3 and the tracking is completed, k', k
'3Z=yOU, but from equations '2, [9', and '1■, k'3=k3 point o2.

Such correction can be automated by the following means.

FIG. 3 shows an example of a sequence control circuit for automatically performing calorie correction. In Figure 3, Ro, R2, R
5 is an OR circuit, R1, R3, and R4 are AND circuits, and T is an off-delay timer. The calorie correction command is given to the AND circuit R when the water-fuel ratio, that is, the output signal of the water-fuel ratio controller M, exceeds a predetermined upper or lower limit, or when an operator presses a button. AND circuit R,
is opened when the calorie correction permission condition is satisfied, that is, when the process is in a stable state, and provides a calorie correction command to the AND circuits R3 and R4 through the OR circuit R2. Since one of the AND circuits R3 and R4 is open depending on whether the water-fuel ratio is greater than or less than 1, the calorie increase command A or the calorie decrease command is output through the open AND circuit. AND circuit R3 or R
The output signal of 4 is the OR circuit R5 and the off-delay timer T.
tracking commands C, D and manual switching command E
, F and is fed back to the OR circuit R2. Due to this feedback, the output signal of OR circuit R2 is self-maintained. Calorie increase command A and force. The calorie reduction command B is given to the calorie setting device M5 to change its set value. This causes the output signal of the calorie setter pigeon to change, and therefore the output signal FF of the multiplier M7 to change. Tracking commands C and D are given to the water-fuel ratio controller M and the oxygen amount controller M2, respectively, and are tracked.

mode. As a result, the water/fuel ratio controller M changes its output signal k so that the fuel command signal FFD matches the fuel flow signal FF, and the oxygen amount controller changes the output signal k so that the air command signal AFD matches the air flow signal AF'. Change the output signal k3. Manual switching commands E and F
'are respectively given to the fuel flow controller M3 and the air flow controller M4' to put them into manual control mode.

In the manual control mode at this time, the operator does not perform any output adjustment operation, so the output signals of both controllers are kept unchanged. This makes it possible for both controllers to be insensitive to deviations in the human input signals that occur during tracking. Water fuel ratio controller M by tracking
, that is, the water-fuel ratio approaches 1, but until it falls within 1±Δ, the calorie increase (decrease) command A (B) continues to be generated, so the calorie set value continues to be corrected.

Following this, the output signal of the water-fuel ratio controller M further approaches and eventually becomes within 1±Δ, the calorie increase (decrease) command A (B) disappears, and the change in the calorie set value stops. When the calorie increase (decrease) command A (B) disappears, tracking commands C, D and manual switching commands E, F are issued after a certain period of time due to the function of off-delay timer T.
disappears and each controller is returned to the automatic control state.The time limit value of the off-delay timer T is set to be sufficient to complete tracking, but it may be omitted if the tracking speed is far. When the apparatus shown in FIG. 2 is combined with the apparatus shown in FIG. 3, calorie correction can be performed automatically and quickly without causing any disturbance to the process.

Note that the multiplier M8 may be replaced by an adder. Furthermore, there are various means for implementing sequence control, such as by using a program. Also, during tracking, the fuel flow controller M3
Although the manual control mode was used to maintain the output signal of the air flow controller M4 unchanged, any output holding function may be used. As described above, the present invention provides a method and apparatus that can quickly perform calorie correction without causing any disturbance to the process.

By using the method and apparatus of the present invention, a thermal power plant using a coal-fired supercritical pressure boiler can be effectively controlled.

[Brief explanation of the drawing]

Fig. 1 is a conceptual block diagram of a thermal power generation control system using a supercritical pressure boiler, and Fig. 2 is a conceptual block diagram of an embodiment of the present invention.
FIG. 3 is a block diagram of a sequence control circuit combined with the device of FIG. 2. M. ...Water-fuel ratio controller, M2...
・Oxygen amount control port -A, pond...Fuel flow rate control port -A, M4...Air flow controller, M5...
...Calorie setting device, ground to M8... Multiplier. Younger brother’ figure 2 Younger brother J figure

Claims (1)

[Scope of Claims] 1. A fuel command signal obtained by correcting the water-fuel ratio of the master signal of the water supply flow rate control loop by the output of the water-fuel ratio controller and a fuel flow signal including a calorie setting value term are given, and based on the difference between the two signals. A fuel flow rate controller that controls the fuel flow rate, and an air command signal obtained by correcting the oxygen amount of the fuel command by the output of the oxygen amount controller, and an air flow rate signal are provided, and the air flow rate is controlled based on the difference between the two signals. In an automatic plant control system for a supercritical pressure boiler having a controller, the output of the water-fuel ratio controller is adjusted such that the difference between the input signals of the fuel flow controller and the difference between the input signals of the air flow controller becomes zero when the calorie set value is corrected. A calorie correction method for correcting the signal and the output signal of the oxygen content controller. 2. A fuel system that is given a fuel command signal obtained by correcting the water-fuel ratio of the master signal of the water supply flow rate control loop using the output of the water-fuel ratio controller and a fuel flow signal that includes a calorie setting value term, and performs fuel flow rate control based on the difference between the two signals. A supercritical system having a flow rate controller, and an air flow controller that is given an air command signal and an air flow rate signal in which the fuel command index is corrected for the amount of oxygen by the output of the oxygen amount controller, and controls the air flow rate based on the difference between the two signals. In automatic plant control equipment for pressure boilers, controllers with tracking functions are used as the water-fuel ratio controller and oxygen amount controller, respectively, and when correcting the calorie setting value, the water-fuel ratio controller outputs a fuel command signal so that it matches the fuel flow signal. A signal tracking operation is performed, and the oxygen amount controller is made to perform an output signal tracking operation so that the air command signal matches the air flow rate signal, and a controller with an output holding function is used as a fuel flow controller and an air flow controller, respectively. The calorie correction device is configured to hold both controllers in an output holding state when correcting the calorie set value. 3. A fuel system that is given a fuel command signal obtained by correcting the water-fuel ratio of the master signal of the water supply flow rate control loop using the output of the water-fuel ratio controller and a fuel flow signal that includes a calorie setting value term, and performs fuel flow rate control based on the difference between the two signals. A supercritical pressure system having a flow rate controller, and an air flow controller that is given an air command signal in which the fuel command is corrected for the amount of oxygen by the output of the oxygen amount controller and an air flow rate signal, and controls the air flow rate based on the difference between the two signals. In an automatic plant control device for a boiler, a controller with a tracking function is used as a water-fuel ratio controller and an oxygen amount controller, a controller with an output holding function is used as a fuel flow controller and an air flow controller, and a sequence control device is used, During calorie correction, this sequence control device gives a setting value correction command to the calorie setting device, and gives a tracking command to the water-fuel ratio controller and oxygen amount controller, so that the water-fuel ratio controller can adjust the fuel command signal to match the fuel flow signal. The oxygen amount controller performs a tracking operation on the output signal so that the air command signal matches the air flow rate signal, and an output holding command is given to the fuel flow controller and the air flow controller. A calorie correction device that maintains a state until an output signal of a water-fuel ratio controller reaches a predetermined value.