JP2918650B2 - Boiler plant automatic control device and control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic boiler control device, and more particularly to an automatic control device for a boiler plant suitable for instantaneously shifting to a partial load motion due to a sudden decrease in load.

[Prior Art] FIG. 4 shows an example of a control system diagram of a once-through boiler.

In the conventional automatic boiler control device, even if there is a sudden change in load, the only option is to use a normal control circuit. Above all, there is a case where the load drops instantaneously from the high load to the in-house load and the operation shifts to the islanding operation. A circuit has been used which switches to a fixed set value to follow a load and returns to a normal control system after a certain period of time.

[Problems to be Solved by the Invention] In these conventional control systems, when a part of a power supply system is cut off in a power generation boiler plant or the like, an operation system with a low load is required to handle a local load. However, the boiler plant had to be shut down once and then operated alone in the plant, and then the supply power system had to be gradually expanded as the load increased. In addition, when the variation width of the sudden decrease in load is small, the local load alone operation for transmitting power to a reduced area can be performed by following the normal control, and the power failure range can be minimized in some cases. However, if the settling load is uncertain and a significant load change occurs, load reduction will not be performed stably for loads separated as regional loads, and the change in state quantity will increase. It often led to trips.
If the operation of the power generation unit cannot be continued, the entire area will be blackout.

In addition, in the method of once increasing the load after narrowing down to the in-house load, it is inevitable that a power failure occurs for a certain period of time.

Therefore, it has been desired to avoid such a situation and to improve the success rate of the local load independent operation so that the power transmission of the power generation unit is not stopped when the operation load of the power generation unit is high.

SUMMARY OF THE INVENTION An object of the present invention is to provide a boiler plant automatic control device that allows any load from any load to any load to rapidly drop and settle in any load zone.

Another object of the present invention is to provide a boiler plant automatic control device that responds to an instantaneous load change in a full load zone.

[Means for Solving the Problems] The above object of the present invention is achieved by the following constitutions. That is, in a boiler plant automatic control device provided with a normal control system that controls each operation terminal provided for each boiler control input amount by a load request signal, a means for detecting a sudden change in load based on a boiler load change corresponding signal, Each characteristic relay is provided so as to proportionally follow the boiler load change corresponding signal, and further, when there is an output of a sudden load change signal from the sudden load change detecting means, the normal control system from the normal control system to each of the operation terminals is provided. An automatic boiler plant control device provided with each switching means for switching a load request signal to a boiler load change corresponding signal via each of the characteristic relays.

In the boiler plant automatic control device of the present invention, when the operation end is a main steam output, when there is an output of a sudden load change signal from the sudden load change detecting means, the load request signal from the normal control system is output. Switching means for switching to a boiler load change corresponding signal without using a characteristic relay can be provided. Further, in each of the characteristic relays, a time for completing the reduction of the load is set in advance in accordance with the boiler control input amount, the output of the sudden load change signal from the sudden load change detecting means is stopped, and the set time elapses. After doing
The boiler load change corresponding signal to each operation terminal via each of the characteristic relays may be output to each of the switching means so as to switch to a load request signal from the normal control system.

[Operation] When the sudden load change detection signal is output, each operation terminal signal for controlling the boiler control input amount of the main steam control valve, the main water supply pump, the fuel control valve, the push-in fan drive unit, the spray control valve, etc. Since it changes simultaneously with the boiler load change corresponding signal via each characteristic relay which tends to be proportional to the boiler load change corresponding signal such as an output signal, the load changes toward the settling load at the maximum operation speed of each operation terminal. . If each operating end returns to the normal control system after waiting for a specific operation completion time, the correction operation is performed until the proportional / integral control operates and the deviation disappears.

What kind of load can be obtained by accurately setting the operating end opening in the set state in each load of the boiler to the characteristic relay based on the stable target signal necessary for changing the load of the boiler such as the generator output signal Can also be settled.

When the number of ignition burners is reduced in parallel with the detection of the sudden decrease in the load and the narrowing of the operation end of the boiler control input amount, the number of burners and the movement of the fuel operation end can be controlled in association with each other.

Embodiment FIG. 1 shows an automatic control system diagram of a once-through boiler according to the present invention. First, during a normal load operation, the boiler operation terminals (not shown) such as a main steam control valve, a main feed water pump, a fuel control valve, a push-in fan drive unit, a spray control valve, and the like are normally operated by the boiler load request signal 1. Is controlled by the control system. Next, when a sudden load change is detected, the switch 3 outputs a generator output signal 2 instead of the boiler load request signal 1. In addition, the main water pump,
The control system for each operating end of the boiler, such as the fuel control valve, the push-in fan drive unit, and the spray control valve, is provided with switches 4, 5, 6, 7, and 8, respectively. At the same time, switches 4, 5,
6, 7, and 8 are switched from the normal control system to the sudden load change control system. That is, for each operation end of the main feed water pump, fuel control valve, push-in fan drive unit, and spray control valve except for the main steam control valve, each operation in which the load characteristic corresponding to the generator output signal 2 is set. The characteristic relays 9, 10, 11, 12, and 13 at the end are respectively switched.
The signals switched simultaneously by the switches 3, 4, 5, 6, 7, and 8 at the time of a sudden change in the load are shown in FIG.
The main water supply pump is (b), the fuel control valve is (c), the push-in fan drive unit is (d), and the spray control valve is (e) and (f). After the set return time, the switching is performed again, and the control is sequentially returned to the normal control system.

Although related to the operation speed of the operation end, the return time is determined for each operation end in consideration of the time required for stabilizing the state due to a sudden change in load, that is, the time constant of the boiler. For example, it has been experimentally found that the following speed of the fuel supply system is relatively high, and that of the water supply system and the air supply system is slightly lower. Therefore, the compressed fluid air is narrowed down slowly, and the following speed of the operation end is made slower than that of the fuel, thereby narrowing down the air while maintaining the air-rich state. In addition, since the control system of the turbine drive BFP will be operated for water supply, if the narrowing is too early and the width of undershoot is large, it is expected that MFT (master fuel trip) due to a decrease in water supply flow rate will occur. . Therefore, the following speed of the operation end of the water supply system is slightly reduced.

FIG. 2 shows an embodiment of a circuit for detecting a sudden change in load.
A deviation calculation relay 20 calculates a 1-second load change width output from the generator output signal 2 from the switches 16 and 17 and the analog memories 18 and 19 for signal storage. The calculated value of the deviation calculation relay 20 is converted into analog / digital signal converters 21 and 22 for the deviation signal.
, The load change width set in advance, for example, -25% to +25
% Is detected. The operation of this circuit will be described in detail as follows.

The generator output signal 2 indicates that the switch 16 is a side and the switch 17 is c
The switch 17 is designed to output d when the switch 16 is outputting a, and the switch 17 is outputting a. Therefore, the deviation calculation relay 20 sequentially outputs (ad) → (bc)
→ (ad) is input. In the state of (bc), the output b (a one second before) of the analog memory 18 is switched to the switch 16
Is output to the deviation calculation relay 20 via the
The output c, which is the current generator output signal 2, is transmitted to the deviation calculation relay 20 via. Thus, the deviation calculation relay 20
In (2), the output (bc) is subjected to a deviation calculation, so that a change in load for one second can be detected in this state. Next one
In the second, (ad) is input to the deviation calculation relay 20. Thus, a change in load every one second can be detected. A 25% load change per second indicates that an extreme load change has occurred, i.e., deviating from a normal load change.

FIG. 3 shows an explanatory diagram of a procedure for detecting a sudden change in load. Third
As shown in FIG. 7A, when the generator output 2 sequentially changes from A to E each time one second elapses, the generator output 2, the analog memories 18 and 19, and the deviation calculation relay 20 are respectively the third one. A signal as shown in FIG.

The outputs (BA), (BC),
When (D−C) and (D−E) correspond to a load change of 25% or more in absolute value, one of the A / D converters 21 and 22 is output, and the switches 23 and 24 are closed. If a load change of 25% or more occurs even in normal circumstances, adjustment such as setting the load to 30% will be determined in light of the usage conditions of the unit.

When one of the switches 23, 24 is closed, the relay 26 is activated to close the switch 29. The switch 29 is a characteristic relay 9 to a switch 4 to 8 at each operating end of the boiler such as a main steam control valve, a main water supply pump, a fuel control valve, a push-in fan drive unit, a spray control valve, etc. shown in the automatic control system diagram of FIG. Thirteen operations are connected in series to the circuit. However, the switching device 3 does not need to consider a time delay between the generator output and the main steam output, so that no characteristic relay is provided.

In FIG. 2, when the switch 29 is closed, the relays 32, 36,... Start operating, and the switch 4 of the main feed pump and the switch 5 of the fuel control valve switch from the contact a to the contact b, respectively. . At this time, since the characteristics of the operation end are different for each system, the respective reset times are set by timers 31, 35,. For example, since the control valve of the fuel control valve is also small, the switch 5 is reset in about 15 seconds, and the switch 4 is reset in about 25 seconds in consideration of the time until the main water supply pump is stabilized. I do. Here, the combination of the relay and the timer at each operation end in FIG. 2 corresponds to the characteristic relays 9 to 13 in FIG. The switches 25, 28, 30, 33,... In FIG. 2 are manual switches.

In this way, when a sudden change in load is detected by the circuit shown in FIG. 2, the switch 3 switches the signal from the boiler load request signal 1 to the generator output signal 2, and the switches 4, 5, 6, 7, and 8 simultaneously operate normally. Switch from the control system to the sudden load change control system.
By detecting a sudden change in the load in the circuit in FIG. 2 and operating the circuit in FIG. 1, the boiler can follow any load from any load.

In practicing the present invention, a signal indicating a load instead of the generator output signal, for example, a signal corresponding to the main steam flow rate and the turbine first-stage steam pressure can be used to perform the same function. is there. Further, as a method of detecting a sudden change in load, a circuit configuration is possible even if it is detected from the movement of a turbine control valve, an intermediate check valve, or the like. The turbine control valve and the intermediate check valve are largely moved when the load suddenly decreases, have a characteristic of once narrowing down to near no load, and then return, so that they are effective for detecting a sudden change in load.

FIG. 1 illustrates an example in which the signal switches 4, 5, 6, 7, and 8 are provided on the upstream side of the automatic / manual switches 40 to 44. It is also possible to install it between the ends (not shown), and even if some of the operation ends do not switch signals, the object is achieved, so this is not different from the present invention.

Further, for a large and rapid load change, in a boiler having a plurality of burners, it may be necessary to reduce the number of burners. For this reason, the sudden decrease in load
When the signals are detected by the digital converters 21 and 22, this signal is transmitted to an automatic burner control device (not shown), and the burners are sequentially extinguished. In an automatic burner control device, a point fire is usually performed so that the number of burners matches the load, or the burner pressure falls within the upper and lower limit values. Is effective in the case of.

[Effects of the Invention] According to the present invention, as a method of following a sudden load change exceeding the response limit of the boiler, normal proportional / integral / differential control can be separated and proportional control can cope with a sudden load change. Even if the load suddenly changes, for example, by shutting down a part of the power supply system, it is possible to follow the load without a power failure. This greatly contributes to ensuring stable power supply.

In addition, when the number of ignition burners is reduced in parallel with detecting the sudden decrease in the load and narrowing down the operation end of the boiler control input amount, the number of burners and the movement of the fuel operation end can be controlled in association with each other. There is an advantage that the ability to follow a sudden change in is further improved.

[Brief description of the drawings]

1 is a control system diagram of a once-through boiler embodying the present invention, FIG. 2 is a circuit diagram for detecting a sudden change in load, FIG. 3 is an explanatory diagram showing a procedure for detecting a sudden change in load, and FIG. It is a control system diagram. 1 ... load request signal, 2 ... generator output (load corresponding signal), 3-8 ... switch, 9-13 ... characteristic relay, 16,
17: Switch, 18, 19: Analog memory (storage means), 21, 22: A / D converter (change width setting means)

Claims (3)

(57) [Claims] 1. A boiler plant automatic control device having a normal control system for controlling each operation terminal provided for each boiler control input amount by a load request signal, means for detecting a sudden load change based on a boiler load change correspondence signal. And each characteristic relay is provided so as to proportionally follow the boiler load change corresponding signal. Further, when there is an output of a sudden load change signal from the sudden load change detecting means, the normal control to each of the operation terminals is performed. An automatic boiler plant control device, comprising: a switching means for switching a load request signal from a system to a boiler load change corresponding signal via each of the characteristic relays. 2. When the operation end is a main steam output, when a sudden load change signal is output from the sudden load change detecting means, a load request signal from the normal control system is output without passing through the characteristic relay. 2. The boiler plant automatic control device according to claim 1, wherein the switching means switches to a boiler load change correspondence signal. 3. The characteristic relay has a preset time for completing the load narrowing in accordance with the boiler control input amount, and there is no output of a sudden load change signal from the sudden load change detecting means. After a lapse of time, the boiler load change corresponding signal to each operation terminal via the characteristic relay is output to the switching means so as to switch to a load request signal from the normal control system. The boiler plant automatic control device according to claim 1 or 2, wherein: