JPH06147403A - Pressure-temperature controller - Google Patents

Abstract

PURPOSE:To stabilize a plant by restraining effect of variation caused by a fault. CONSTITUTION:A mode switching unit 2 for switching a control mode of a device to a boiler follow-up mode wherein respective flow rates on a governor side is taken as a boiler demand from a coodination mode according to fault information of a power transmission line from a variety of sensors 1 is provided. Moreover, a gain switching unit 4 for switching gains of a PID controller of main steam pressure for performing correction of the boiler demand by interlocking a demend instruction 6 for instructing the swithcing to a boiler performance follow-up mode by means of the mode switching unit 2 and a function generator 3 for setting the respective gains of the coodination mode and the boiler follow-up mode according to the rate of change of load in the PID controller are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure temperature controller for controlling main steam pressure and main steam temperature of a boiler used in a power plant.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional structure of a pressure temperature controller for controlling the main steam pressure and main steam temperature of a boiler used in a power plant by controlling the feed water flow rate and the fuel flow rate. In the figure, in the mode of cooperative control in the power generation plant, the required load command is given as a demand, and each part is controlled by the deviation signal between the load command of the generator output 8 and the power generation amount 7. The main steam temperature in the boiler is controlled by the fuel flow rate 22, and the main steam pressure is controlled by the feed water flow rate 21.

The feed water flow rate 21 and the fuel flow rate 22 are
Both of them are determined by the boiler demand 18, and the boiler demand 18 is determined by a preset operation state or a command from the central power feeding command center.

Correction is made by the demand and the deviation between the main steam pressure and the actual steam pressure 10 at the time of the demand command,
It becomes boiler demand 18. Based on this demand 18,
The water supply flow rate 21 is determined by the function unit 16 in which each flow rate in the load is set in advance.

The fuel flow rate 22 is determined by the function unit 17 in which the amount of fuel used in each load is set by the boiler demand 18 similarly to the feed water flow rate 21, and the adder 19 adds the correction 20 by the deviation signal of the main steam temperature. Determines the final flow rate value.

A certain control state is referred to as a control mode. In this control mode, the pressure and temperature by the feed water flow rate 21 are controlled by the fuel flow rate 22, and the control is performed while also monitoring the power generation amount on the turbine side. Such a control state is called a cooperative mode.

[0007]

In the cooperative mode as described above, when an accident such as disconnection occurs in the electric power transmission line, the amount of electric power to be transmitted because the load of the electric power system up to that point is instantly reduced. However, the amount of electricity generated by the boiler becomes unnecessary as a result. At this time, in the thermal power plant, the rotational speed of the turbine is reduced in order to reduce the generator output.
The turbine is controlled by a governor valve and controls the final outlet steam produced in the boiler. The behavior of the governor valve opening at this time is restored to a position of several seconds as shown in FIG. The opening of the governor valve is "0.9" at the steady position, but since the operation of this governor valve is fast, boiler demand 1
The change command of No. 8 is also difficult to follow, and the demand 18 continues to be in a state of a certain constant command value. Further, since the governor valve is narrowed down, the turbine side operates to reduce the load, but since the command value due to the demand is in a high state, the balance is lost during that period and the power generation amount decreases, but the water supply flow rate 21 or The fuel flow rate 22 does not decrease, especially the water supply flow rate 2
Since there is no drop of 1, the load for the amount of power generation increases, resulting in a high pressure state, which is an unfavorable state in operation. Also, a similar decrease occurs in the fuel flow rate 22,
The boiler demand 18 does not decrease and the fuel flow rate 22 does not decrease in spite of the actual suddenly reduced power generation amount, so that the steam temperature also does not decrease.

The present invention has been made in view of the above circumstances, and an object of the present invention is to stabilize the plant by suppressing the influence of the fluctuation when an accident occurs in an electric power transmission line. It is to provide a pressure temperature control device capable of performing the above.

[0009]

That is, the present invention is a pressure temperature control device for controlling the main steam pressure and main steam temperature of a boiler used in a power plant by means of the feed water flow rate and the fuel flow rate, and Depending on the accident information, the control mode of the device is switched from the cooperative mode to the boiler follow-up mode in which the above-mentioned flow rates on the governor side are boiler demands, and the mode changer is linked to the switch to the boiler performance follow-up mode. Gain switch for switching the gain of the main steam pressure PID controller that corrects boiler demand by means of function, and a function generator for setting the gain of each of the cooperative mode and boiler following mode according to the rate of change of load in the PID controller. It is equipped with and.

[0010]

With the above-mentioned structure, the control mode is switched from the cooperative mode to the boiler follow-up mode at the moment when an accident occurs in the power transmission line. With this mode switching, the boiler demand becomes each flow rate of the feed water flow and the fuel flow rate flowing to the governor side.Thus, when the turbine governor valve narrows down due to an accident, each flow rate on the governor side also decreases according to the throttled state. Demand drops. Along with this, control is performed by a gain switching device having a function generator that sets an appropriate gain in accordance with the rate of change of the load in the PID controller of the main steam pressure that corrects the boiler demand in accordance with the switching of the control mode. The system can be stabilized. Therefore, since the demand changes in accordance with the change of the accident, it is possible to change the supply water flow rate and the fuel flow rate by τ in the changed state.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic structure thereof, which is additionally provided in the structure shown in FIG.
The same parts as and are designated by the same reference numerals, and the illustration and description thereof will be omitted.

The mode switch 2 receiving the process information from the various load sensors 1 judges the occurrence of an accident from the process information and switches the control mode from the cooperative mode to the boiler follow-up mode in accordance with the judgment.

In response to the switching operation by the demand command 6 output from the mode switch 2, the PID controller 1 shown in FIG.
4 does not cause unstable operation, the function generator 3 presets appropriate parameters according to the control mode state.
The parameter 5 such as the gain is set in the gain switcher 4 having the.

FIG. 2 shows the control result in the boiler following mode. Here, it is assumed that an accident occurs in the electric power transmission line, an abnormality occurs in the system, and the governor valve narrowing-down behavior 23 occurs as shown in FIG. 7. When such an electric power transmission line accident occurs, the load on the transmission line side decreases sharply, so it is necessary to sharply reduce the amount of power generation on the power plant side.This amount of power generation depends on the amount of steam from the boiler side. Controlled. The rotation speed of the turbine and the generator is constant, but the amount of power generation is proportional to the energy of the steam, and that energy is the amount of steam. Since the turbine is rotated by the steam at the outlet of the heater of the boiler, the amount of this steam is controlled by the governor valve,
Change the amount of power generation. In this way, the governor valve suddenly changes to reduce the amount of power generation and try to control others.

At this time, when the control mode is switched from the cooperative mode to the boiler following mode by the mode switch 2 as described above, the demand command 6 becomes the governor side flow rate. Since the flow rate on the governor side at this time depends on the movement of the governor valve as described above, the demand shape is also the same. Therefore, the feed water flow rate 21 and the fuel flow rate 22 become like the feed water flow rate curve 36 and the fuel flow rate curve 37 shown in FIG. 3, and change according to the governor side flow rate. As a result, the main steam pressure after the accident becomes as shown in the main steam pressure curve 27 of FIG.
The rise in pressure is suppressed.

Further, the fuel flow rate 22 appropriately fluctuates in about 30 seconds in a behavior according to the accident fluctuation as shown by the fuel flow rate curve 37 in FIG. By this operation, the main steam pressure does not rise to its pressure limit value of 265ata, and the stability of the plant is maintained. Further, since the fuel flow rate 22 also decreases smoothly, the main steam temperature does not exceed the allowable temperature 551 ° C as shown by the main steam pressure curve 27 in FIG. From this, it becomes possible to control the boiler stably while suppressing the influence of the accident. Next, FIGS. 4 and 5 show the fluctuation results after the accident in the cooperative mode. The change in the governor valve due to the accident is represented by the governor valve opening curve shown in FIG.

Compared with the boiler follow-up mode, the boiler demand 18 cannot cope with a sudden change in an accident and does not deteriorate, which prevents the feed water flow rate 21 and the fuel flow rate 22 from being narrowed down.
The response is as shown by the feed water flow rate curve 51 and the fuel flow rate curve 52 in FIG. In particular, the main steam pressure does not drop so much as the main steam pressure curve 27 of FIG.
The safety valve is activated beyond ata. Further, when the boiler demand 18 starts to decrease, the main steam pressure also starts to decrease, which is not preferable for operation in a boiler having a slow response. In the control by the boiler tracking mode,
When the position of the governor valve is stable at a specific position, the governor flow rate is also stable, so that the feed water flow rate 21 and the fuel flow rate 22 are also stable.

When the accident recovers and the load increases again and control in the cooperative mode becomes necessary, the mode switching unit 2 switches the control mode from the boiler following mode to the cooperative mode again.

[0020]

As described above, according to the present invention, there is provided a pressure temperature control device for controlling the main steam pressure and the main steam temperature of a boiler used in a power plant by controlling the feed water flow rate and the fuel flow rate. For switching the control mode of the device from the cooperative mode to the boiler follow-up mode in which the above-mentioned flow rates on the governor side are boiler demands according to the accident information of the electric wire, and to switch to the boiler performance follow-up mode by this mode switcher. A gain switcher that switches the gain of the main steam pressure PID controller that performs boiler demand correction in conjunction with each other, and a function that sets the gains of the cooperative mode and the boiler following mode according to the rate of change of the load in the PID controller. Since it is equipped with a generator, the main steam pressure and main Suppressing the increase of air temperature, the plant by suppressing the influence of an accident variation can provide a pressure temperature control device capable of stabilizing.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration according to an embodiment of the present invention.

FIG. 2 is a view for explaining the same embodiment.

FIG. 3 is a view for explaining the same embodiment.

FIG. 4 is a view for explaining the same embodiment.

FIG. 5 is a view for explaining the same embodiment.

FIG. 6 is a diagram showing a configuration of a conventional pressure / temperature control device.

FIG. 7 is a diagram showing a behavior of the governor valve in FIG. 6 due to narrowing down.

[Explanation of symbols]

1 ... Various sensors, 2 ... Mode switcher, 3, 9 ... Function generator, 4 ... Gain switcher, 5 ... Parameter, 6 ... Demand command, 7 ... Power generation amount, 8 ... Generator output, 10 ... Actual steam pressure , 11, 14 ... PID controller, 12 ... Governor opening, 1
3 ... Subtractor, 15, 19 ... Adder, 16 ... Feed water flow rate function generator, 17 ... Fuel flow rate function generator, 18 ... Boiler demand, 20 ... Main steam temperature correction signal, 21 ... Feed water flow rate, 2
2 ... Fuel flow rate, 23 ... Governor opening behavior, 25, 45 ... Reheat steam pressure curve, 26, 44 ... Power generation amount curve, 27, 43
… Main steam pressure curve, 28, 42… Reheat steam temperature curve, 2
9,41 ... Main steam temperature curve, 30,46 ... Power generation amount, 3
1,47 ... Main steam pressure, 32,48 ... Reheat steam pressure, 3
3 ... Main steam temperature, 34 ... Reheat steam temperature, 35, 50 ... Air amount curve, 36, 51 ... Water supply flow rate curve, 37, 52 ... Fuel flow rate curve, 38, 53 ... Water supply flow rate, 39, 54 ... Fuel flow rate , 40, 55 ... Air amount, 49 ... Steam temperature.

Claims (1)

[Claims] 1. A pressure temperature control device for controlling a main steam pressure and a main steam temperature of a boiler used in a power plant according to a feed water flow rate and a fuel flow rate, the control mode of the apparatus according to accident information of a power transmission line. Is switched from the cooperative mode to the boiler follow-up mode in which each of the above-mentioned flow rates on the governor side is used as the boiler demand, and the main steam that corrects the boiler demand in conjunction with the switch to the boiler performance follow-up mode by the mode change-over means. It is characterized by further comprising: a gain switching means for switching the gain of the pressure PID controller, and a function generating means for setting the gain of each of the cooperative mode and the boiler following mode according to the load change rate in the PID controller. Pressure temperature control device.