JPH0484001A - Automatically controlling device and method for boiler plant - Google Patents

Abstract

PURPOSE:To cope with instantaneous load variation in the whole load band by providing a normal control system with switching means installed to respective operation terminals which sends to respective operation terminals the output of a characteristic relay following proportionally the output after a sudden change in load from a normal control system when there is the output of signal of a load sudden change detection by a load sudden change detection means. CONSTITUTION:When a load sudden change is detected, a switching device 3 which is ready for the boiler load request signal 1 outputs generator output signal 2 as the boiler load request signal. Switching devices 4-8 switch from a normal control system to a load sudden change control system simultaneously. For respective operation terminals of main supply water pump, fuel control valve, positive fan drive unit, and spray control valve except a main steam heating valve a load characteristics which correspond to generator output signal are set respectively at characteristics relay terminals 9-13. With the time until finishing operation for signals that are switched simultaneously by a load sudden change the return times for respective operational terminals are set at respective operation terminals and they are returned by and by to the normal control systems.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic boiler control system, and particularly to an automatic control system for a boiler plant suitable for instantaneously shifting to partial load operation due to a sudden load reduction.

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

In conventional boiler automatic control devices, even if there is a sudden load change, the only way to deal with it is to use a normal control circuit. Among these, there are cases where the load drops instantly from a high load to the station load and transitions to isolated operation.For this reason, a fixed setting value for isolated operation within the station is established, and at the same time an accident on the outside line is detected, the load for isolated operation within the station is set. Circuits have been used that switch to a fixed set value, follow the load, and return to the 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 the power supply system is cut off in a power generation boiler plant, etc., the local load is taken over and the system is operated at low load. Although it is necessary,
- After the entire boiler plant was shut down and operated independently within the plant, it was necessary to gradually expand the power supply system as the load increased. In addition, when the range of sudden changes in load is small, following normal control enables local load isolated operation to transmit power to the reduced area, thereby minimizing the scope of the power outage.

However, when the stable load is uncertain and a large load change occurs, load narrowing is not performed stably in the range of loads separated as regional loads, and changes in state quantities increase, causing the unit to If the 0 generation unit, which often resulted in a trip, cannot continue operating, a power outage will occur throughout the area.

However, with the method of increasing the load after reducing the load within the plant, it was inevitable that the power would be cut off for a certain period of time.

Therefore, it has been desired to avoid such a situation and improve the success rate of local load independent operation so that there is no power transmission stoppage of the power generation unit when the operating load of the power generation unit is high.

An object of the present invention is to provide an automatic boiler plant control device that can freely rapidly drop the load from any load to any load in all load bands and stabilize the load.

Another object of the present invention is to provide an automatic boiler plant control device that can respond to instantaneous load changes in all load bands.

[Means to solve the problem] The above object of the present invention is achieved by the following configuration.

In other words, in a boiler plant automatic control system equipped with a normal control system that controls an operating terminal provided for each boiler control input amount using a load request signal, the boiler load change corresponding signal is proportionally followed, and each boiler A characteristic relay capable of setting characteristics according to the amount of control input is provided for each operating terminal, and there is a means for detecting a sudden load change based on a signal corresponding to a boiler load change, and an output of a sudden load change detection signal from the sudden load change detection means. A boiler in which the normal control system is provided with a switching means provided for each operating end, which sends the output of the characteristic relay that proportionally follows the output after a load change from the normal control system to each operating end. In a plant automatic control device or a boiler plant automatic control method equipped with a normal control system that controls an operating end provided for each boiler control input amount using a load request signal, sudden load changes are detected based on a boiler load change response signal. Then, the control target value of each boiler control input amount is switched to the current output, and the turbine control valve functions to control the rotation speed, and the proportional, integral, and differential control circuits that control each boiler control input amount are switched to the integral and derivative values. A boiler plant automatic control method that switches the circuit so that it does not function, makes it follow only proportional control, waits for the operating end of the boiler control input amount, and then returns to the normal control system, or controls multiple burners using a load request signal. In an automatic boiler plant control method that is equipped with a normal control system that controls each operating terminal for multiple boiler control inputs, including a fuel system operating terminal that controls output, a sudden decrease in load is detected based on a boiler load change response signal, and at the same time This is an automatic boiler plant control method in which the number of ignition burners is reduced in parallel with narrowing down the operating end of the boiler control input amount, and the number of burners and the movement of the fuel operating end are controlled in association with each other.

[Function] When the sudden load change detection signal is output, the main steam control valve, main water supply pump, fuel control valve, forced fan drive unit,
Each operating end signal that controls the boiler control input amount such as a spray control valve changes simultaneously with the boiler load change response signal via each characteristic relay that tends to be proportional to the boiler load change response signal such as the generator output signal. Therefore, the load will change toward the settling load at the maximum operating speed of each operating end. If each operation end waits its own operation completion time and returns to the normal control system, the proportional/integral control will operate and correction operations will be performed until the deviation disappears.

Based on the stable target signal necessary to change the load on the boiler, such as the generator output signal, by setting the operating end opening in the stable state for each boiler load to the characteristic relay accurately, it is possible to It is also possible to stabilize the

Further, by reducing the number of ignition burners in parallel with the narrowing down of the operating end of the boiler control input amount at the same time as detecting a sudden decrease in load, the number of burners and the movement of the fuel operating end can be controlled in association with each other.

[Example] Fig. 1 shows an automatic control system diagram of a once-through boiler according to the present invention. In response to boiler load request signal 1, the main steam control valve, main water supply pump, fuel control valve, forced fan drive unit,
Each boiler operating end (not shown), such as a spray control valve, is controlled in the conventional manner. When a sudden load change is detected, the switch 3 outputs the generator output signal 2 as the boiler load request signal instead of the boiler load request signal 1. Switcher 4.5
．． 6.7.8 also switches from the normal control system to the sudden load change control system at the same time. Main water pump excluding main steam control valve,
For each operating end of the fuel control valve, forced fan drive unit throat, and spray control valve, the load characteristic corresponding to the generator output signal is transmitted to each operating end's characteristic relay 9.10.11.1
Set each to 2.13. Due to a sudden change in load, -
The main steam control valve (
A), main water pump (B), fuel control valve (C), forced fan drive unit (D), spray control valve (E), (F) are set for each operating end, and then Return to normal control system.

Although it is related to the operation speed of the operating end, the return time for each operating end is determined by taking into consideration the time required for the state to stabilize due to a sudden load change, that is, the time constant of the boiler. For example, it has been experimentally found that the follow-up speed of the fuel supply system is relatively fast, while that of the water supply system and air supply system is slightly slower. Therefore, air, which is a compressed fluid, is slowly throttled and the following speed of the operating end is made slower than that of fuel, thereby performing the throttle while maintaining a near-rich state. Additionally, in order to supply water, the control system of the turbine-driven RFP must be operated, and if the narrowing down is too early and the width of undershoot is large, it is expected that an MFT (master fuel trip) will occur due to a decrease in the water supply flow rate. Ru. Therefore, the follow-up speed of the operating end of the water supply system is slightly delayed.

FIG. 2 shows an embodiment of a circuit for detecting sudden changes in load. The deviation calculation relay 20 calculates the load change width for one second, which is output from the generator output signal 2 from the switch 16.17 and the signal storage analog memory 18.19. The calculated value of the deviation calculation relay 20 is used to detect a deviation of a preset load change range, for example, -25% to +25%, by the analog/digital signal converter 21.22 of the deviation signal.

The details of the operation of this circuit are as follows.

The generator output signal 2 is on the a side of the switch 16, and the a side of the switch 17
The switch 17 is designed to be switched from the side , to the b side and dlll every second, respectively, and when the switch 16 is outputting a, the switch 17 outputs d. Therefore, the deviation calculation relay 20 sequentially (a-d)=(
b-c)=(a-d) is input. (b-c)
In the state of , the output b of the analog memory 18 (a from 1 second ago)
) is output to the deviation calculation relay 20 via the switch 16, while the output C, which is the current generator output signal 2, is transmitted to the deviation calculation relay 20 via the switch 17. In this way, the output (b-c) is subjected to a deviation calculation in the deviation calculation relay 2o, so that a load change for one second can be detected in this state. During the next one second, (a-d) is input to the deviation calculation relay 20. In this way, load changes every one second can be detected. A load change of 25% in 1 second indicates that an extreme load change has occurred, deviating from normal load changes.

FIG. 3 shows an explanatory diagram of the procedure for detecting sudden changes in load.

As shown in FIG. 3(a), when the generator output 2 changes sequentially from A to E every 1 second, its output 2, analog memory 18, 19 and deviation calculation relay 20 are respectively A signal as shown in FIG. 3(b) is output or input.

Outputs of deviation calculation relay 20 (B-A), (B-C), (
When D-C) and (D-E) correspond to a load change of 25% or more in absolute value, one of the signals from the A/D converter 21.22 is output and the switch 23.24 is closed. If a load change of 25% or more occurs under normal conditions, change the load setting to 3.
Adjustments such as setting it to 0% will be determined in light of the usage conditions of the unit.

When either switch 23, 24 closes, relay 26
is activated and closes the switch 29. Switch 29 is the first
The circuit operates the characteristic relays 9 to 13 of the switching devices 4 to 8 at each operation end of the boiler, such as the main steam control valve, main water pump, fuel control valve, forced fan drive unit, and spray control valve, shown in the automatic control system diagram in the figure. are connected in series. however,
As for the switching device 3, there is no need to consider the time delay between the generator output and the main steam output, so no characteristic relay is provided.

In Fig. 2, when the two switches close, the relay 32.36,
... starts operating, and the main water pump switch 4, fuel control valve switch 5, etc. respectively switch from their contact a to their contact s. At this time, since the characteristics of the operating end are different for each system, the timer 31 sets the reset time for each system.
．． Set with 35,... For example, since the fuel control valve and adjustment valve are small, the switch 5 should be reset in about 15 seconds, and the main water pump should be reset in about 25 seconds, taking into consideration the time it takes for the main water supply pump to stabilize. do. Here, the second
The combination of relays and timers at each operating end in the figure corresponds to characteristic relays 9 to 13 in FIG. Further, the switches 25, 28, 30, 33, . . . in FIG. 2 are manual switches.

In this way, when a sudden load change is detected by the circuit shown in Figure 2, the generator output 2 is used as the boiler load request signal to switch the signal at the switch 3, and at the same time, the switch 4, 5, 6, 7, 8 also changes the normal control system. Switch to sudden load change control system. By detecting a sudden load change using the circuit shown in FIG. 2 and activating the circuit shown in FIG. 1, it becomes possible to make the boiler follow any load.

In carrying out the present invention, it is possible to achieve the same function by using a signal indicating the load that changes to the generator output, for example, a signal corresponding to the main steam flow rate or the turbine first stage steam pressure. be. In addition, as a method for detecting sudden changes in load,
Even if detected from the movement of turbine control valves, intermediate check valves, etc.
The circuit configuration is possible. Turbine control valves and intermediate check valves have the characteristic of moving significantly when the load suddenly decreases, reducing the load to near no load, and then returning to normal, so they are effective in detecting sudden changes in load.

In Fig. 1, an example is explained in which the signal switch 4.5.6.7.8 is provided upstream of the automatic/manual switch 40 to 44; It is also possible to install it between the terminals (not shown), and even if there are some operating terminals that do not switch signals, the purpose can be achieved and this is not different from the present invention.

For large and rapid load changes, it may be necessary to reduce the number of burners in boilers with multiple burners. For this reason, when a sudden decrease in load is detected by the analog/digital converter 21.22, this signal is sent to an automatic burner control device (not shown), which sequentially controls the burners.
Operate the fire extinguisher. In an automatic burner control device, normally the burner is extinguished so that the number of burners matches the load or the burner pressure is within the upper and lower limits, but the sudden load change signal described above is used as the first extinguishing signal. It is valid in the case of

[Effects of the Invention] According to the present invention, as a method for following sudden changes in load that exceed the response limit of the boiler, it is possible to separate the usual proportional, integral, and differential control and use proportional control to respond to sudden changes in load.
Part of the power supply system from the generator is cut off, etc.
It is now possible to follow sudden changes in load without causing a power outage. This greatly contributes to ensuring a stable power supply.

In addition, if a sudden decrease in load is detected and the number of ignition burners is reduced in parallel with narrowing down the operating end of the boiler control input amount, it is possible to control the number of burners in association with the movement of the fuel operating end, and the load This has the advantage that the ability to follow sudden changes in is further improved.

[Brief explanation of the drawing]

Fig. 1 is a control system diagram of a once-through boiler in which the present invention is implemented, Fig. 2 is a circuit diagram for detecting a sudden load change, Fig. 3 is an explanatory diagram showing a sudden load change detection procedure, and Fig. 4 is a diagram of a once-through boiler according to the prior art. It is a control system diagram. 1...Load request signal, 2...Generator output (load corresponding signal), 3-8...Switcher, 9-13...Characteristic relay 16.17...Switcher, 18.1 1...Analog memory (storage means), 21.22...A/D converter (variation range setting means) Applicant Babcock Hitachi Co., Ltd. Agent Patent attorney Takayoshi Matsunaga (and 1 other person) Time (a)

Claims (5)

[Claims] (1) In a boiler plant automatic control system equipped with a normal control system that controls operating terminals provided for each boiler control input amount using a load request signal, the system proportionally follows the boiler load change response signal, and A characteristic relay capable of setting characteristics according to the amount of boiler control input is provided for each operating terminal, and there is a means for detecting a sudden change in load based on a signal corresponding to a boiler load change, and an output of a sudden load change detection signal from the sudden load change detection means. and sending from the normal control system to each operating end the output of the characteristic relay that proportionally follows the output after the load changes;
A boiler plant automatic control device characterized in that a switching means provided for each operating end is provided in a normal control system. (2) The characteristic relay returns the output after the load change of each boiler control input amount to the normal control system after a preset time according to the boiler control input amount completes narrowing down of the load. The boiler plant automatic control device according to claim 1. (3) The sudden load change detection means includes two switching devices connected in parallel that switch and output a signal corresponding to the current boiler load change and a signal corresponding to the boiler load change a certain period of time ago, and each switching device. A storage circuit that stores the boiler load change corresponding signal that was connected in series with each switch a certain time ago, and the current boiler load change corresponding signal that is output from one switch and a certain time ago that is output from the other switch. a deviation calculating means for calculating the deviation from the boiler load change corresponding signal; and outputting a sudden load change signal to the switching means provided at each of the operating terminals when the calculated deviation value calculated by the deviation calculating means is greater than or equal to a set value. 3. The boiler plant automatic control system according to claim 1, further comprising load change range setting means for setting a load change range. (4) In a boiler plant automatic control method equipped with a normal control system that controls an operating end provided for each boiler control input amount using a load request signal, when a sudden load change is detected based on a boiler load change response signal, each boiler At the same time as switching the control target value of the control input amount to the current output, the turbine control valve functions the rotation speed control, and among the proportional, integral, and differential control circuits that control each boiler control input amount, the integral and differential circuits do not function. An automatic boiler plant control method characterized in that the control system is switched to a normal control system, followed by only proportional control, and returns to a normal control system after waiting for operation time of an operating end of a boiler control input amount. (5) In an automatic boiler plant control method equipped with a normal control system that controls each operating end of a plurality of boiler control input quantities, including a fuel system operating end that controls the output of multiple burners based on a load request signal, boiler load change It is characterized by detecting a sudden decrease in load based on a corresponding signal, simultaneously reducing the number of ignited burners in parallel with narrowing down the operating end of the boiler control input amount, and controlling the number of burners in relation to the movement of the fuel operating end. Boiler plant automatic control method.