JPH10103020A - Controller and control method for turbine bypass valve in combined plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an abnormal rise in steam pressure as well as suppress a variation in the water level of a steam drum to the minimum level in a combined plant. SOLUTION: A set value for a command to open a turbine bypass valve 6 in a combined plant is calculated on the basis of a detected value of the pressure of steam generated from an exhaust gas boiler 3, and the calculated set value is subtracted from the detected value of the steam pressure to obtain a subtracted value, based on which a command is issued to open the turbine bypass valve 6. If a sudden rise in pressure is caused in the combined plant by cutoff of steam, the set value is fixed at the value at the cutoff of steam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine bypass valve control device and a control method applied to a combined plant when steam is cut off.

[0002]

2. Description of the Related Art Power generation in a combined plant in which a gas turbine and a steam turbine are combined is remarkably superior in thermal efficiency to conventional thermal power generation. As a method of combining a gas turbine and a steam turbine, the following two methods are mainly employed.

(1) A single-shaft combined plant in which a gas turbine and a steam turbine are connected to the same shaft. (2) A multi-shaft combined plant in which a gas turbine and a steam turbine are individually arranged.

The present invention is applied to the control system of both of these combined plants. In the following prior art, a multi-axis combined plant will be described as an example. The same applies to a single-shaft combined plant.

FIG. 2 is a schematic system diagram showing a multi-shaft combined plant. The combined plant includes a gas turbine 1 and a steam turbine 4. A generator 2 is connected to the gas turbine 1. The exhaust gas of the gas turbine 1 is guided to an exhaust gas boiler 3, and steam is generated by the exhaust gas boiler 3.

In the exhaust gas boiler 3, feed water is heated by a flue evaporator 3a, and steam is separated by a steam drum 3b. This steam is sent to the steam turbine 4. The steam turbine 4 is driven by the steam sent from the exhaust gas boiler 3, and power is generated by a generator 5 connected to the steam turbine 4.

Here, in the single-shaft combined plant, since the gas turbine 1 and the steam turbine 4 are connected to the same shaft, a single generator is used, so that at least two generators are used. Although different from a multi-shaft combined plant, the control method of the turbine bypass valve described below is exactly the same for a single-shaft combined plant.

The combined plant is provided with a turbine bypass line 6a connected between the condenser 4a and the steam line 7a on the upstream side of the steam turbine 4 and used when starting and stopping the plant. A bypass valve 6 is provided. Turbine bypass valve 6
, During the operation of the plant, for some reason the exhaust gas boiler 3
It also has a role in reducing the pressure when the steam pressure of the gas suddenly rises. The steam line 7a is provided with a pressure detector 7 for detecting a steam pressure.

Normally, the pressure set value of the turbine bypass valve 6 is set to a value obtained by adding a predetermined value to the actual pressure during operation. That is, as shown in FIG. 3, the set value is set to a value obtained by adding a specified value to the detected actual steam pressure. FIG. 3 is a block diagram showing a conventional control device for a turbine bypass valve.

In FIG. 3, reference numeral 8 denotes a specified value setter for setting a specified value, and 9 is connected to the specified value setter 8 and connected to a pressure detector 7 (FIG. 2) to detect the detected steam pressure. An adder 10 for adding the specified value and a change rate limiter connected to the output side of the adder 9, and an adder 11 is connected to the output side of the change rate limiter 10 and connected to the pressure detector 7. , A subtractor for subtracting the set value which is the output of the rate-of-change limiter 10 from the steam pressure,
A controller that is an I regulator.

In this block configuration, a value obtained by limiting the rate of change by the rate-of-change limiter 10 is set as a set value, and the actual steam pressure is compared with a subtractor 11 to obtain a deviation. Adjust valve 6.

The operation of the prior art in the above configuration will be described below with reference to FIG. FIG. 4 is a diagram showing a steam pressure, a pressure set value, and a turbine bypass valve opening, respectively. In a normal state, the output of the subtractor 11 is negative, so that the turbine bypass valve 6 is fully closed (A). The specified value set in the specified value setting unit 8 is set to a value that does not cause the turbine bypass valve 6 to open during normal operation of the plant. At this time, when the turbine bypass valve 6 is opened, the steam is not fed into the steam turbine 4 to prevent the plant efficiency from remarkably lowering (B).

Next, when a steam shut-off phenomenon such as a load cut-off or an emergency stop occurs in the steam turbine 4, the steam pressure of the exhaust gas boiler 3 rises rapidly and exceeds a set value as shown in FIG. Therefore, the turbine bypass valve 6 operates in the opening direction (A-1). Through a series of these operations, the steam pressure 7 is once increased, and then returned to the set value of the turbine bypass valve 6.

Thus, since the steam pressure is controlled to the set value, the operation of the pressure relief safety valve (not shown) attached to the exhaust gas boiler 3 can be avoided.
On the other hand, due to the fluctuation of the steam pressure of the exhaust gas boiler 3, the water level of the steam drum 3b fluctuates greatly.
Drum water may carry over.

This is because of the fluctuation of the steam pressure and the steam drum 3b.
This is because there is the following relationship with the fluctuation of the water level. That is, when the steam pressure increases, the steam drum 3b
Then, the steam in the flue evaporator 3a is crushed and the steam drum water level temporarily drops, and then the steam pressure rises, so that the saturation temperature rises and the steam drum 3b and the flue evaporator 3a Of steam in the steam drum 3b
Because the water level will rise.

Therefore, in order to properly control the water level of the steam drum 3b, it is important to suppress fluctuations in the steam pressure. However, such a control device and control method for a turbine bypass valve in a conventional combined plant require such measures. Is not provided at all.

[0017]

As described above, in the conventional control apparatus and control method of the turbine bypass valve in the combined plant, the phenomenon that the steam is shut off on the steam turbine side, such as load shut-off or emergency stop, is applied to the plant. When this occurs, the steam pressure rise is suppressed by the turbine bypass valve, and the pressure relief safety valve of the exhaust gas boiler is controlled so that it does not operate, and the pressure rise can be suppressed. There is a problem that the water level fluctuates.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems, and a turbine bypass in a combined plant capable of minimizing fluctuations in the steam drum water level while suppressing an abnormal increase in steam pressure. It is an object to provide a control device and a control method for a valve.

[0019]

In order to solve the above-mentioned problems, a control device for a turbine bypass valve in a combined plant according to the present invention comprises: a steam pressure detecting means for detecting a steam pressure generated by an exhaust gas boiler; A set value setting unit that determines a set value of the opening degree command of the turbine bypass valve based on a detection value of the steam pressure detection unit; and a setting value set in the set value setting unit based on a detection value of the steam pressure detection unit. A control device for a turbine bypass valve in a combined plant, comprising: a subtraction unit that performs subtraction, and a controller that issues an opening degree command of the turbine bypass valve based on the subtraction value subtracted by the subtraction unit.
A steam cutoff detecting means for detecting a case where a sudden pressure rise due to steam cutoff occurs in the plant, and a steam cutoff detecting means provided between the set value setting means and the subtracting means, wherein the steam cutoff by the steam cutoff detecting means is not detected. While the output of the set value setting means is output to the subtractor, if the steam cutoff is detected, the detection value of the steam pressure detection means when the steam cutoff is detected is stored and held. Vapor pressure holding means for outputting to the subtractor.

The control method of the turbine bypass valve in the combined plant according to the present invention determines the set value of the opening command of the turbine bypass valve based on the detected value of the steam pressure generated by the exhaust gas boiler. In the control method of the turbine bypass valve in the combined plant in which the opening degree command of the turbine bypass valve is performed based on a subtraction value obtained by subtracting the set value from the detection value of the above, a sudden pressure increase due to steam shutoff in the plant is In the case of occurrence, the set value is fixed to the value at the time when the steam cutoff occurs.

[0021]

According to the above configuration, when steam (load) interruption occurs, the pressure set value of the turbine bypass valve is immediately switched to the actual pressure and fixed, so that the timing of opening the turbine bypass valve is earlier. Thus, an increase in steam pressure can be suppressed. Since the fluctuation of the steam pressure is reduced, the fluctuation of the water level of the steam drum can also be suppressed.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a control device of a turbine bypass valve in a combined plant according to the present invention. 1, the same reference numerals as those in FIG. 3 denote the same objects. Note that the configuration of the combined plant in the embodiment of the present invention has the configuration of the multi-axis combined plant shown in FIG.

In FIG. 1, reference numeral 14 is provided on the output side of the rate-of-change limiter 10, and selectively switches between the output of the rate-of-change limiter 10 and the steam pressure actually measured by the pressure detector 7, thereby providing a subsequent analog. The changeover switch 14 is a changeover switch for inputting to the memory 15. The changeover switch 14 is a state signal 1 representing information of a sudden pressure increase or emergency stop such as steam cutoff.
3, the input of the analog memory 15 is changed to the change rate limiter 1
Switching from the output side of 0 to the pressure detector 7 side.

In the above configuration, during the normal (normal) operation of the plant, the set value which is the input value of the subtractor 11 is a value obtained by adding a predetermined value to the measured steam pressure, and a change rate limiter. Although the rate of change is limited by 10, if a steam cutoff due to a load cut-off or an emergency stop of the steam turbine 4 is detected by an external circuit (detector) (not shown), the state indicates the steam cut-off. The signal 13 immediately switches the changeover switch 14 to the pressure detector 7 side, and the detected pressure value at that time is held and output by the analog memory 15. That is, the analog memory 15 holds and fixes the value immediately after the steam pressure is input from the pressure detector 7 after the changeover switch 14 is switched. Thus,
The changeover switch 14 and the analog memory 15 constitute the vapor pressure holding means of the present invention.

According to such a configuration, as shown in FIG. 4D, when a steam cutoff occurs, the steam pressure rises due to the effect of the steam cutoff, while the output of the analog memory 15 increases. Is fixed to the pressure at the time when the steam cutoff occurs, as shown in FIG.
The pressure control deviation, which is an output value of 0, becomes a positive value. At this point, the turbine bypass valve 6 opens as shown in FIG. Therefore, the fluctuation of the steam drum water level affected by the fluctuation of the steam pressure can be reduced.

After the steam cutoff is eliminated, control according to the operation of the plant is performed, such as gradually decreasing the steam pressure to reach the starting pressure in order to restart the plant. Further, although the embodiment described above has been described with respect to a multi-shaft combined plant, it is apparent that the embodiment can be similarly applied to a single-shaft combined plant.

[0027]

As described above in detail, according to the present invention, a steam pressure detecting means for detecting a steam pressure generated by an exhaust gas boiler, and a turbine bypass valve based on a detected value of the steam pressure detecting means. Setting value setting means for determining the setting value of the opening degree command of the above, subtraction means for subtracting the setting value set in the setting value setting means from the detection value of the vapor pressure detection means, and subtraction by the subtraction means A controller for performing a command for opening the turbine bypass valve based on the value, in a control device for the turbine bypass valve in a combined plant, a steam cutoff detection for detecting a case where a sudden pressure increase due to a steam cutoff occurs in the plant. Means, provided between the set value setting means and the subtraction means, and when the steam cutoff by the steam cutoff detection means is not detected, the setting is performed. While the output of the setting means is output to the subtractor, when the steam cutoff is detected, the detection value of the steam pressure detecting means when the steam cutoff is detected is stored and output to the subtractor. And a setting value of an opening degree command of the turbine bypass valve is determined based on a detected value of the steam pressure generated by the exhaust gas boiler, and the set value is determined from the detected value of the steam pressure. In the control method of the turbine bypass valve in the combined plant in which the opening degree command of the turbine bypass valve is performed based on the subtracted value of the above, when a rapid pressure increase due to steam cutoff occurs in the plant,
Since the set value is fixed to the value at the time when the steam cutoff occurs, when the steam (load) cutoff occurs,
By immediately switching and fixing the pressure set value of the turbine bypass valve to the actual pressure, the timing at which the turbine bypass valve opens becomes earlier, and a rise in steam pressure can be suppressed. Since the fluctuation of the steam pressure is reduced, the fluctuation of the water level of the steam drum can also be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a control device for a turbine bypass valve according to an embodiment of the present invention.

FIG. 2 is a schematic system diagram showing a multi-shaft combined plant.

FIG. 3 is a block diagram showing a conventional control device for a turbine bypass valve.

FIG. 4 is a diagram showing changes in steam pressure, pressure set value, and valve opening.

[Explanation of symbols]

1 gas turbine, 2 and 5 generator, 3 exhaust gas boiler, 4 steam turbine, 6 turbine bypass valve, 7
Pressure detector, 8 specified value setter, 9 adder, 10 rate-of-change limiter, 11 subtractor, 12 controller.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI F22B 1/18 F22B 1/18 CE

Claims (2)

[Claims] 1. A steam pressure detecting means for detecting a steam pressure generated by an exhaust gas boiler; and a set value setting means for determining a set value of an opening degree command of a turbine bypass valve based on a detected value of the steam pressure detecting means. Subtraction means for subtracting the set value set in the set value setting means from the detected value of the steam pressure detection means, and issuing an opening degree command for the turbine bypass valve based on the subtraction value subtracted by the subtraction means. In a control device for a turbine bypass valve in a combined plant comprising a controller, a steam cutoff detecting means for detecting a case where a sudden pressure rise due to steam cutoff occurs in the plant; and a steam cutoff detecting means between the set value setting means and the subtraction means. And when the steam cutoff by the steam cutoff detecting means is not detected, outputs the output of the set value setting means to the subtractor. On the other hand, when the steam cutoff is detected, a turbine comprising: a steam pressure holding means for storing and holding a detection value of the steam pressure detecting means when the steam cutoff is detected and outputting the detected value to the subtractor. Control device for bypass valve. 2. A setting value of an opening command of a turbine bypass valve is determined based on a detected value of a steam pressure generated by an exhaust gas boiler, and based on a subtraction value obtained by subtracting the set value from the detected value of the steam pressure. In the control method of the turbine bypass valve in the combined plant in which the opening degree command of the turbine bypass valve is performed, in a case where a sudden pressure increase due to the steam shutoff occurs in the plant, the steam shutoff occurs with the set value. A method for controlling a turbine bypass valve in a combined plant, characterized in that the control value is fixed to a value at the time.