JPH03290007A - Combined cycle control unit - Google Patents

Abstract

PURPOSE:To restrain steam flow rate from making a sudden change and keep drum water level from causing abnormality by switching valve opening positions of a steam governor and a steam bypass valve from a variable pressure operation control to a constant pressure operation control when the drum water level has caused abnormality while operating a steam cycle under the variable pressure. CONSTITUTION:A generator 6 is driven in a multi-shaft type combined power plant by supplying to a steam turbine 5 a high temperature and high pressure steam generated at an exhaust heat recovery boiler 4 to where a high temperature gas exhausted from a gas turbine unit 1 is delivered. The valve opening positions of steam governors 9, 10 and steam bypass valves 11, 12 are controlled by a steam cycle control unit 20A where a steam turbine constant pressure operation command signal formation circuit 40 is equipped and which is made to generate a constant pressure operation command signal that will change the steam turbine operation from the variable operation to the constant operation when at least one of the value or the rate of change thereof of the drum water level of the exhaust heat boiler or the water supply flow rate of the exhaust heat recovery boiler or the like has exceeded the prescribed value while the steam turbine is operated under the variable pressure.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention is directed to a combined power generation plant in which a gas turbine cycle and a steam turbine cycle are coupled via a heat recovery boiler. It relates to a cycle control device.

(Prior art) A combined power generation plant is a system in which a gas turbine cycle and a steam turbine cycle are combined via an exhaust heat recovery boiler, and the gas turbine cycle consists of an air compressor, a combustor, a gas turbine, etc. In addition, the steam turbine cycle is used for exhaust heat recovery boilers, steam turbines, ascites,
Consists of water supply pumps, etc. There are two types of such combined power generation plants: an axle type in which the gas turbine, generator, and steam turbine are connected by a -shaft, and a multi-shaft type in which the gas turbine and steam turbine have separate shafts and are each equipped with a generator. be.

Here, a multi-shaft combined power generation plant will be explained, but the details of the steam turbine cycle are the same for the axle-shaft type and the multi-shaft type.

In a multi-shaft combined power generation plant, a gas turbine device is driven by combustion gas obtained by burning fuel to rotationally drive a gas turbine generator to generate electricity. High-temperature, high-pressure exhaust gas discharged from the gas turbine device is led to an exhaust heat recovery boiler, where heat is exchanged and the low-temperature gas is released into the atmosphere. Steam that exchanges heat with high-temperature gas in the exhaust heat recovery boiler and becomes high-temperature and high-pressure is supplied to a steam turbine, and the steam energy drives the steam turbine to rotate. A steam turbine generator is driven by a steam turbine to generate electricity.

Further, the steam evaporated in the high-pressure drum and the low-pressure drum in the exhaust heat recovery boiler is supplied to the steam turbine via the high-pressure steam control valve and the low-pressure steam control valve, respectively. The steam before passing through the high pressure steam control valve is bypassed to the condenser via the high pressure steam bypass valve, and the steam before passing through the low pressure steam control valve is bypassed to the condenser via the low pressure steam bypass valve. The condenser cools the bypassed steam or the steam that has done work in the steam turbine and converts it into water. Water in the condenser is supplied to the high-pressure drum by a high-pressure water supply pump and to the low-pressure drum by a low-pressure water supply pump.

The valve opening degrees of the high pressure steam control valve, the low pressure steam control valve, the high pressure steam bypass valve, and the low pressure steam bypass valve are controlled by the steam cycle control device 20. The steam cycle controller W20 forms a steam control valve opening setting signal and a steam bypass valve opening setting signal based on the steam pressure actual measurement signal S from the sensor and the command from the setting device.

FIGS. 6 and 7 show a conventional steam cycle control device 20.
FIG. 6 is a block diagram showing the configuration of the steam control valve control circuit, and FIG. 7 is a steam control valve control circuit. Note that both Figures 6 and 7 have the same configuration for high-pressure steam and low-pressure steam, so one system is shown as a representative, but in reality, each diagram has two systems, one for high-pressure steam and one for low-pressure steam. It is provided.

The steam control valve control circuit shown in FIG. 6 includes a speed setting device 21.
It includes a load controller 22, an adder 23, and a steam pressure controller 24. The steam pressure controller 24 also includes a switch 24
0, steam pressure setting @241. It includes a PID calculator 243, a biaser 244, and a subtracter 245. here,
The signal obtained by adding the output signal from the speed setter 21 and the output signal from the load controller 22 in the adder 23 and the signal formed by the steam pressure controller 24 are input to the low value selector 25. Ru. The low value selector 25 selects whichever signal has the lowest value and outputs it as the steam control valve opening setting signal.

In addition, in the steam pressure controller 24, when the switch 240 is inactive, the steam pressure setting device 24 receives the steam pressure actual measurement signal S.
The output signal from 1 is subtracted by a subtracter 242, and the subtraction result is input to a PID calculator 243. PID calculator 24
3 outputs a control signal. Further, in the steam pressure controller 24, when the switch 240 is operating, the output signal of the bias device 244 is subtracted from the steam pressure actual measurement signal S by the subtractor 245, and the steam pressure actual measurement signal S is obtained from the subtraction result signal. Subtraction @ 242 performs subtraction, and the subtraction result signal is input to the PID calculator 243 to obtain a control signal from the PID calculator 243 . Note that this steam pressure controller 24 is
This is a circuit that controls the high-pressure steam regulator valve to close when the high-pressure steam pressure drops abnormally and the high-pressure steam bypass valve closes in an attempt to maintain the steam pressure, and even after it is fully open, the steam pressure decreases. During normal operation, a value that is not selected by the low value selector 25 is output. The steam pressure controller 24 also operates the low pressure steam control valve in the same manner.

The speed setting device 21 outputs a negative signal to cut off steam when the speed exceeds a predetermined speed so that the steam turbine does not trip overspeed, and is set to zero during normal operation.

The steam bypass valve control circuit shown in FIG.
, steam pressure setting device 27, subtractor 28, PID calculator 29
, a bias device 30, and an adder 31.

Here, when the switch 26 is inactive, the steam pressure actual measurement signal S is obtained by subtracting the output signal from the steam pressure setting device 26 by the subtractor 28, and inputting the subtraction result to the PID calculator 29. The output signal of the PID calculator 29 is output as a steam bypass valve opening setting signal.

Thereby, the steam pressure is maintained at the value set by the steam pressure setting device 27. When the switch 26 is in operation, the output signal from the bias device 30 is added to the steam pressure actual measurement signal S, and the steam pressure actual measurement signal S is subtracted from this by the subtractor 28, and the subtraction result is used to set the steam bypass opening degree. It becomes a signal.

In addition, the steam pressure actual measurement signal S used for steam control valve control
is generally the ladder pressure to the steam turbine, and the steam pressure actual measurement signal S used for the steam bypass valve is generally the outlet pressure of the exhaust heat recovery boiler 4 or the pressure immediately before the steam bypass valve. However, the steam control valve and the steam bypass valve use the steam pressure on the same piping for control. However, high pressure and low pressure are separated on the piping. Such a steam pressure actual measurement signal S is detected by a sensor.

Here, when the exhaust gas from the gas turbine device introduced into the waste heat recovery boiler is gradually increased, the water in the high pressure drum and the low pressure drum in the waste heat recovery boiler evaporates. Thereafter, until the steam turbine is started, the output signals of the speed setter 21 and the load controller 22 are set to zero, and the high-pressure steam control valve and the low-pressure steam control valve are kept fully closed. The high pressure steam bypass valve and the low pressure steam bypass valve maintain the outlet pressure of the exhaust heat recovery boiler at a predetermined pressure based on the output signal of the steam pressure setting device 27 when the switch 26 is inoperative. When the high-pressure steam condition reaches a state where the steam turbine can be started, the output signal of the speed setting device 21 is increased to open the high-pressure steam control valve to start the steam turbine, and after reaching the rated speed, the steam Turbi〉 Generator is added to the power system,
Start up until the initial load is secured. During this time, the high pressure steam pressure at the exhaust heat recovery boiler outlet decreases due to the opening of the high pressure steam control valve, so the high pressure steam pressure at the exhaust heat recovery boiler outlet is maintained at a predetermined value by closing the high pressure steam bypass valve.

Moreover, the setting value of the steam pressure setting device 27 is set so that the high pressure steam bypass valve is fully closed before the high pressure steam control valve is fully opened. The steam bypass valve control circuit is similar to the steam pressure setting device 27 for the low pressure steam control valve. After the high-pressure steam control valve and the low-pressure steam control valve are fully opened, the switch 240 of the steam pressure controller 24 is operated, and the output signal of the bias device 244 is used to input a signal for always opening the valve to the PID calculator 243. As a result, the high-pressure steam control valve or low-pressure steam control valve is kept fully open at all times.

The switch 240 is operated until a command to stop the steam turbine is received.
This behavior is maintained.

After the high-pressure steam bypass valve and the low-pressure steam bypass valve are also fully closed, the switch 26 is operated and the bias device 3
The high pressure steam bypass valve and the low pressure steam bypass valve are always fully closed by inputting a signal for normally closing the valves to the PID calculator 29 with an output signal of 0. This switch 26 maintains this operation until a command to stop the steam turbine is received.

In this way, once each valve is fully open or fully open, it is maintained. The reason for this is that the gas turbine output responds first to changes in the generator load relative to the overall output, and the output of the steam turbine generator is determined by the steam state at the exhaust heat recovery boiler outlet. be. This is because the output of the steam turbine depends on the steam temperature at the exit of the heat recovery boiler, the steam condition at the exit of the heat recovery boiler depends on the temperature of the gas turbine exhaust gas, and the temperature of the gas turbine exhaust gas depends on the output of the gas turbine. It is determined.

Therefore, since the output of the combined cycle depends on the gas turbine output, the output steam state of the exhaust heat recovery boiler is also controlled by controlling the output of the gas turbine.

A variable pressure operation is performed in which the steam turbine output is changed by changing the steam pressure at the outlet of the exhaust heat recovery boiler.

In the combined cycle steam cycle control device as described above, when the steam turbine is operated at variable pressure with the high pressure steam control valve and the low pressure steam control valve fully open and the high pressure steam bypass valve and the low pressure steam bypass valve fully open. In addition, when the gas turbine generator load changes suddenly, the gas turbine exhaust gas temperature changes suddenly, the heat input to the waste heat recovery boiler changes suddenly, and the steam flow rates of the high-pressure drum and the low-pressure drum change suddenly.

Further, if one water supply pump stops while water is being supplied by a plurality of water supply pumps, the amount of water supplied to the high-pressure drum and the low-pressure drum will suddenly change. In such a case, the amount of water supplied is usually adjusted by controlling the water levels in the high-pressure drum and the low-pressure drum so that the water level in the drums remains constant.

(Problem to be Solved by the Invention) However, when the above-mentioned variable pressure operation is performed, the exhaust heat recovery boiler outlet steam pressure and outlet steam flow rate are not controlled, so when the above-mentioned fluctuations occur, The steam flow rate becomes unstable. In particular, since the drum water level changes based on the integral of the deviation between the steam flow rate and the feed water flow rate, the drum water level will not become stable even if the feed water flow rate is adjusted in a state where the steam flow rate is unstable. Therefore, there is a problem in that the water level in the high-pressure drum or the low-pressure drum becomes abnormally high or low.

Here, if the drum water level becomes abnormally high, the steam tends to become wet and the blades of the steam turbine may be damaged, so it is necessary to bring the steam turbine to an emergency stop. On the other hand, if the drum water level becomes abnormally low, the high-pressure drum and the low-pressure drum will be in a dry state, so it is necessary to cut off the heat input to the waste heat recovery boiler. When such problems occurred, it was necessary to stop the steam cycle urgently.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a combined cycle control device that can maintain a constant drum water level of an exhaust heat recovery boiler to continue operating a steam cycle. do.

[Structure of the Invention (Means for Solving the Problems) In order to achieve the above object, the present invention provides a steam turbine of a combined cycle plant in which a gas turbine cycle and a steam turbine cycle are connected via an exhaust heat recovery boiler. In a combined cycle control device that controls the steam control valve and the exhaust heat recovery boiler outlet steam bypass valve, the exhaust heat recovery boiler drum water level, the exhaust heat recovery boiler feed water flow rate, the exhaust heat recovery boiler steam flow rate, and the gas Steam that outputs a command to switch from variable pressure operation control to constant pressure steam pressure control when at least one of the turbine exhaust gas temperature, the gas turbine generator load value, their equivalent value, or their respective rate of change exceeds a predetermined value. It is equipped with a turbine constant pressure operation command signal formation circuit, and a control means for controlling the opening and closing of a steam turbine control valve and an exhaust heat recovery boiler outlet steam bypass valve based on the commands from the steam turbine constant pressure operation command signal formation circuit. .

(Function) The present invention is capable of suppressing sudden changes in the steam pressure at the outlet of the exhaust heat recovery boiler by switching from variable pressure operation to low pressure operation when the water level in the drum of the exhaust heat recovery boiler fluctuates or fluctuates. By focusing on this, we suppressed sudden changes in the steam flow rate at the exhaust heat recovery boiler outlet, thereby suppressing changes in the drum water level. Fluctuations in the drum water level occur due to the integration of the deviation between the steam flow rate and the feedwater flow rate, but if the fluctuation is a steady one without fluctuations in the steam flow rate, it is possible to prevent the drum water level from fluctuating significantly by adjusting the feedwater flow rate. .

(Example) The present invention will be explained in detail below.

FIG. 1 shows a general example of a multi-shaft compound power plant to which an embodiment of the present invention is applied. Note that a multi-shaft combined power generation plant generally has several steam turbines installed in place of several gas turbines, but the first
In the figure, a gas turbine is used to simplify the explanation.

In the multi-shaft combined power generation plant shown in FIG. 1, a gas turbine device 1 includes an air compressor 1a, a combustor 1b
, a gas turbine 1c, and the gas turbine device 1 and the gas turbine generator 2 are connected by a single shaft. The high temperature gas discharged from the gas turbine device 1 is
After passing through the exhaust heat recovery boiler inlet damper 3, it is led to the exhaust heat recovery boiler 4. The gas, which has undergone heat exchange in the exhaust heat recovery boiler 4 and has become low temperature, is released into the atmosphere. Exhaust heat recovery boiler 4
The steam that has become high temperature and high pressure through heat exchange with the high temperature gas is supplied to the steam turbine 5, and the steam turbine 5 is driven to rotate by the energy of the steam.

The steam turbine 5 is uniaxially connected to a steam turbine generator 6, and the steam turbine generator 6 is driven by the steam turbine 5 to generate electricity. Further, the steam evaporated in the high pressure drum 7 and low pressure drum 8 in the exhaust heat recovery boiler 4 is supplied to the steam turbine 5 via the high pressure steam control valve 9 and the low pressure steam control valve 10, respectively. Said high pressure steam control valve 9
The steam before passing through passes through a high pressure steam bypass valve 11,
Further, the steam before passing through the low pressure steam control valve 10 is bypassed to the condenser 13 via the low pressure steam bypass valve 12.

a (Water 813 is the bypassed steam or steam turbine 5
The steam that has done the work is cooled and converted into water. Condenser 13
The water is supplied to the high-pressure drum 7 by the high-pressure water supply pump 14 and to the low-pressure drum 8 by the low-pressure water supply pump 15, respectively.

The valve opening degrees of the high pressure steam control valve 9, the low pressure steam control valve 10, the high pressure steam bypass valve 11, and the low pressure steam bypass valve 12 are controlled by the steam cycle control device 20A. The steam cycle control device 20A includes a sensor 18
．． Steam pressure actual measurement signal SH from 19.

A steam control valve opening setting signal and a steam bypass valve opening setting signal are generated based on commands from the SL and the setting device. The steam cycle control device 20A includes a high pressure steam control valve control circuit CVHC1 and a high pressure steam bypass valve control circuit BVH.
C1 low pressure steam regulator control circuit CVLC1 low pressure steam bypass valve control circuit BVLC1 includes a steam turbine constant pressure operation command signal forming circuit 40. This steam cycle control device 120A includes a steam turbine constant pressure operation command signal forming circuit 4
It will operate based on a constant pressure operation command signal from 0.

The steam turbine constant pressure operation command signal forming circuit 40 generates the values of the exhaust heat recovery boiler drum water level, the exhaust heat recovery boiler feed water flow rate, the exhaust heat recovery boiler steam flow rate, the gas turbine exhaust gas temperature, and the gas turbine generator load during the steam turbine variable pressure operation. , their equivalent values, or their respective rates of change exceed a predetermined value, a constant pressure operation command signal is generated so that variable pressure operation changes to constant pressure operation. When a command from the steam turbine constant pressure operation command signal forming circuit is input, the high pressure steam regulator control circuit CVHC1 high pressure steam bypass valve control circuit BVHC1 the low pressure steam regulator control circuit CVL
A control means consisting of C1 and a low pressure steam bypass valve control circuit BVLC controls opening and closing of the steam turbine control valve (9, 10) and the exhaust heat recovery boiler outlet steam bypass valve (11, 12).

Now, details of the elements constituting the steam cycle control device 20A will be explained below with reference to FIGS. 2 to 4.

FIG. 2 is a block diagram showing the high pressure steam regulator control circuit CVHC or the low pressure steam regulator control circuit CVLC.

Since these have the same configuration, only one will be shown. In addition, the same components as those in the prior art are denoted by the same reference numerals, and the description thereof will be omitted.

The difference between the steam control valve control circuit in FIG. 2 and the circuit in FIG. 6 is that a memory 246 and switches 247 and 248 are added to configure the steam pressure controller 24A; is unchanged. And the steam pressure actual measurement signal S is
The data is input to the storage device 26 via the switch 248 and stored. The output signal from the memory 26 and the output signal from the subtracter 245 are switched and selected by a switch 247 and supplied to the switch 240.

FIG. 3 is a block diagram showing the high pressure steam bypass valve control circuit BV)IC or the low pressure steam bypass valve control circuit BVLC. Since these have the same configuration, only one will be shown. In addition, the same components as those in the prior art are denoted by the same reference numerals, and the description thereof will be omitted.

The steam bypass valve control circuit shown in FIG. 3 differs from the circuit shown in FIG. 7 in that a memory 32 and switches 33 and 34 are added, and the other components are unchanged. and,
The steam pressure actual measurement signal is sent to the memory 32 via the switch 34.
This allows it to be entered and stored. The output signal of the memory 32 and the output signal of the adder 31 are selectively switched by a switch 33 and supplied to the switch 26.

FIG. 4 is a circuit diagram showing a steam turbine constant pressure operation command signal forming circuit.

In FIG. 4, the steam turbine constant pressure operation command signal forming circuit 40 includes logical sum circuits 41, 42, and logical product circuits 43.
44.45 and an off-delay timer 46. In the logical sum circuit 41, during the sudden increase in gas turbine load, I
a, large change in gas turbine exhaust gas temperature Ib, large decrease in high-pressure drum water supply flow rate Ic, large decrease in low-pressure drum water supply flow rate Id,
A high pressure drum steam flow rate change large Ie, a low pressure drum steam flow rate large change If, a high pressure drum water level change Ig, and a low pressure drum water level large change Ih are input to form a steam turbine constant pressure operation start signal Sl. This steam turbine constant pressure operation start signal S
1 is supplied to AND circuits 44 and 45. In addition, the AND circuit 43 is input with the high pressure steam regulator fully open Ja, the low pressure steam regulator fully open Jb, the high pressure steam bypass valve fully closed Je, the low pressure steam bypass valve fully closed Jd, and the steam turbine generator output above a predetermined value Je. to form a steam turbine variable pressure operation signal S2.

The steam turbine variable pressure operating signal S2 is input to the AND circuit 45. The AND circuit 45 outputs an output based on the steam turbine constant pressure operation start signal Sl and the steam turbine variable pressure operation signal S2. This signal is output from the OR circuit 42, becomes a latch signal S3, and is supplied to the AND circuit 44. As a result, the constant pressure operation start signal continues to be output from the AND circuit 44. This signal is output via the off-delay timer 46 as a steam turbine constant pressure operation command signal S4. This steam turbine constant pressure operation command signal S4
operates switches 247 and 248 in FIG. 2 and opens switches 33 and 34 in FIG.

The operation of the embodiment having such a configuration will be explained.

During steam turbine variable pressure operation, when a condition occurs that causes the water level of the high pressure drum 7 or the low pressure drum 8 to fluctuate, or a condition in which the water level fluctuates occurs, the steam turbine constant pressure operation command signal forming circuit 40 shown in FIG. A constant pressure operation command signal S4 is output.

As a result, the steam turbine switches from variable pressure operation to constant pressure operation, and the steam turbine variable pressure operation signal S2 is not established, but while the steam turbine constant pressure operation start command S1 is established due to the latch signal S3, the steam turbine is in constant pressure operation. Command signal S4 continues to be output.

In addition, the off-delay timer 46 is used for a predetermined period of time after the steam turbine constant pressure operation start command Sl is not established.
A steam turbine constant pressure operation command signal S4 is held.

The constant pressure operation command signal S4 output in this way causes switches 247 and 248 in FIG. 2 to switch to the memory 246 side, and similarly switches 33 and 34 in FIG.
Switch to side 2. As a result, the storage device 246 and the storage device 32 store the steam pressure actual measurement signal immediately before the command signal S4 is input, and steam pressure control is executed using this value as the set value.

While this constant pressure control is being performed, the amount of heat input to the waste heat recovery boiler 4 increases, and even if the steam flow rate and steam pressure increase and the drum water level attempts to decrease, the steam bypass valve opening setting signal increases. and open the steam bypass valve to suppress the rise in steam pressure. As a result, although the steam flow rate does not change much, it is possible to suppress a drop in the drum water level due to an increase in pressure.

At this time, the valve opening degree of the steam control valve increases, but since the steam control valve is fully open, there is no problem.

On the other hand, while this constant pressure control is being performed, when the drum water level decreases due to a decrease in the feed water flow rate and the steam pressure also decreases,
The steam control valve opening setting signal decreases, the steam control valve closes, and works to suppress a drop in steam pressure, and also reduces the steam flow rate, thereby suppressing a drop in the tram water level. At this time, an attempt is made to lower the steam bypass valve opening setting signal, but since the steam bypass valve is fully closed, no further drop occurs.

As described above, fluctuations in steam pressure can be suppressed by operating the steam bypass valve or the steam control valve in response to increases and decreases in steam pressure.

Further, when the fluctuation in the water level of the drum becomes stable after the constant pressure control, the steam turbine constant pressure operation command signal S4 becomes invalid, the switch 247 in FIG. 2 is switched to the adder 245 side, and the switch 248 is opened.

Similarly, the switch 33 in FIG. 3 is switched to the adder 31 side, and the switch 34 is opened. This causes the steam turbine to shift to variable pressure operation.

FIGS. 5(I) and 5(IF) are block diagrams showing other configuration examples of the steam turbine constant pressure operation command signal forming circuit 40 used in the present invention.

This circuit differs from the one in Figure 4.

The circuit of FIG. 5(1) forms a steam turbine high-pressure steam operation command signal, and the circuit of FIG. 5(II) forms a steam turbine low-pressure steam operation command signal. Fifth
The circuit shown in FIG. 1(I) is composed of OR circuits 51 and 52, AND circuits 53, 54, and 55, and an off-delay timer 56. And S5 is a constant pressure operation start signal,
S6 is a variable pressure operation signal, S9 is a latch signal, and S11 is a constant pressure operation command signal.

The circuit shown in FIG.
It consists of 6. And on the constant pressure steam side, S
7 is a constant pressure operation start signal, S8 is a constant pressure operation signal, S10
is a latch signal, and Sll is a constant pressure operation command signal.

According to such a method, the high pressure steam control valve 9 and the high pressure steam bypass valve 11, and the low pressure steam control valve 10 and the low pressure steam bypass valve 12 can independently switch between variable pressure operation and constant pressure operation. . The operation of this circuit also produces the same effects as those of the above embodiment.

Although not shown, the function of the memory device 246.32 is replaced by the pressure setting device 24L27, and the switch 247
．． 33 may be replaced by a switch 240.26.

As explained above, in the embodiment of the present invention, when the drum water level fluctuates during variable pressure operation of the steam turbine, the control of the steam control valve and the steam bypass valve is switched from variable pressure operation control to constant pressure operation control.

Sudden changes in steam pressure at the exhaust heat recovery boiler outlet can be suppressed. This suppresses sudden changes in the steam flow rate of the drum,
Abnormalities in the water level of the drum can be suppressed, and emergency stoppage of the steam cycle that occurs when the drum water level is abnormal can be prevented.

[Effects of the Invention] As explained above, according to the present invention, when an abnormality in the drum water level occurs during variable pressure operation of the steam cycle, the valve openings of the steam control valve and the steam bypass valve can be adjusted from the variable pressure operation control. Since constant pressure operation can be controlled, it is possible to suppress sudden changes in the steam flow rate, suppress abnormalities in the water level of the drum, and prevent an emergency stop of the steam cycle that occurs when the drum water level is abnormal.

[Brief Description of the Drawings] Fig. 1 is a diagram showing a combined cycle to which an embodiment of the present invention is applied, Figs. 2 to 4 are diagrams showing an embodiment of the present invention, and Fig. 5 is a diagram showing an embodiment of the present invention. Block diagrams showing other embodiments, and FIGS. 6 and 7 are diagrams showing conventional examples. 20A... Steam cycle control device, 40... Steam turbine constant pressure operation command signal forming circuit. (7317) Agent Patent Attorney Rules Noriyuki Chika Figure 2 (1) Figure Figure Figure Figure

Claims (1)

[Claims] Combined cycle control that controls a steam turbine steam control valve and an exhaust heat recovery boiler outlet steam bypass valve in a combined cycle plant in which a gas turbine cycle and a steam turbine cycle are coupled via an exhaust heat recovery boiler. In the equipment, the water level of the exhaust heat recovery boiler drum during steam turbine variable pressure operation,
Exhaust heat recovery boiler feed water flow rate, exhaust heat recovery boiler steam flow rate, gas turbine exhaust gas temperature, gas turbine generator load value,
a steam turbine constant pressure operation command signal forming circuit that outputs a command to switch from variable pressure operation control to constant pressure steam pressure control when at least one of the corresponding values or the rate of change of each of them exceeds a predetermined value; A combined cycle control device comprising: control means for controlling the opening and closing of a steam turbine control valve and an exhaust heat recovery boiler outlet steam bypass valve based on commands from a constant pressure operation command signal formation circuit.