JPH04342806A - Steam turbine control device for combined power plant - Google Patents

Abstract

PURPOSE:To protect turbine blades by detecting an opening degree of an exhaust heat inlet damper and by calculating a limited opening degree for a steam adjusting valve in accordance with the result of the detection so as to rapidly close the steam adjusting valve when the exhaust heat damper is closed. CONSTITUTION:A low value selector 20 receives an output signal which is obtained by adding an output signal from a speed controller 16 to an output signal from a load controller 17, and an output signal from a load limiter 18 and an output signal from a steam controller 19. Further, the selector 10 selects a signal having a lowest value among these signals and delivers the same as a man steam control value opening degree setting signal. In this arrangement, a function generator 21 and a variation rate limiter 22 are further provided. When an opening degree signal from an exhaust heat inlet damper is, for example, decreased, an abrupt decrease command is delivered from the function generator 21 which receives the opening degree signal, to the low value selector 20 by way of the variation rate limiter 22. Accordingly, the main steam control valve is closed to prevent the steam pressure of the inlet port of the steam turbine from abrupt decrease.

Description

[Detailed description of the invention]

[Object of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine control system for a combined power plant in which a gas turbine cycle and a steam turbine cycle are coupled via an exhaust heat recovery boiler.

0002

2. Description of the Related Art FIG. 5 shows a general system of a combined power generation plant.

[0003] The gas turbine 1 is driven by combustion gas,
This causes the gas turbine generator 2 to rotate and generate electricity. The high-temperature, high-pressure exhaust gas discharged from the gas turbine 1 passes through the exhaust heat inlet damper 3 and is transferred to the exhaust heat recovery boiler 4.
The gas is guided to the exhaust heat recovery boiler 4 for heat exchange and becomes a low-temperature gas, which is released into the atmosphere.

[0004] Steam that has become high temperature and high pressure through heat exchange with high temperature gas in the exhaust heat recovery boiler 4 is supplied to a steam turbine 5.
The steam turbine 5 is rotationally driven by the energy of the steam. The steam turbine generator 6 is driven by the steam turbine 5 to generate electricity.

Specifically, steam generated 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 a high pressure steam control valve 9 and a low pressure steam control valve 10, respectively. . The steam before passing through the high pressure steam control valve 9 at the time of startup is
The steam before passing through the low pressure steam control valve 10 is bypassed to the condenser 13 through the low pressure steam bypass valve 12, respectively.

[0006] The condenser 13 cools the bypassed steam and the steam that has worked in the steam turbine 5 and converts it into water. Water in the condenser 13 is supplied to the high-pressure drum 7 by a high-pressure water supply pump 14, and is supplied to the low-pressure drum 8 by a low-pressure water supply pump 15, respectively.

[0007] The exhaust heat inlet damper 3 switches whether the exhaust gas from the gas turbine 1 is directly discharged to the atmosphere or inputted into the exhaust heat recovery boiler 4. In this case, if the exhaust gas is released directly into the atmosphere, the gas turbine will operate alone. If the exhaust gas is input to the exhaust heat recovery boiler 4, it will operate as a combined cycle. This exhaust heat inlet damper 3 is
Because of their large size, they are typically hydraulically driven and open and close at a constant rate or in stages.

FIG. 6 shows a control block configuration of a conventional steam turbine control device provided in the above-described combined power generation plant.

[0009] Since the configuration is the same for both high-pressure steam and low-pressure steam, one of them will be explained, but in reality, two systems are provided, one for high-pressure steam and one for low-pressure steam.

As shown in the figure, an output signal obtained by adding the output signal of the speed controller 16 and the output signal of the load controller 17, the output signal of the load limiter 18, and the steam pressure controller 19
The output signals of each of the output signals are input to the low value selector 20. The low value selector 20 selects the low value signal from among the output signals and outputs it as the steam control valve opening setting signal PB.

Here, the steam pressure controller 19 inputs the steam pressure actual measurement signal PA, and outputs the deviation between the steam pressure actual measurement signal PA and the steam pressure setting signal PS, which is the output signal of the integrator 19a, to the limiter 19b. input. The output signal from the limiter 19b is input to the integrator 19a via a switch 19c. Further, the deviation between the steam pressure setting signal PS and the steam pressure actual measurement signal PA is input to the function generator 19d, and the output signal from the function generator 19d is made to become the steam pressure control signal PM via the switch 19e. There is.

On the other hand, when the switch 19c is operated, the value of the setter 19f, which is set to zero, is input to the integrator 19a. Moreover, when the switch 19e is operated, the setting device 1
The set value of 100% of 9g is set as the steam pressure control signal PM.

The steam pressure actual measurement signal PA is generally the steam turbine header pressure, and the high pressure steam header pressure signal is used to control the high pressure steam regulating valve 9, and the low pressure steam header pressure signal is used to control the low pressure steam regulating valve 10. A pressure signal is used.

[0014] With the above configuration, at startup, either individual operation or combined operation of the gas turbine is selected. At this time, the position of the exhaust heat inlet damper 3 is determined and the gas turbine 1 is started. Note that the switching between the individual operation and the combined operation of the gas turbine may be performed during plant operation.

When combined operation is selected, after the gas turbine 1 is started, the exhaust gas of the gas turbine 1 is supplied to the exhaust heat recovery boiler 4 through the exhaust heat inlet damper 3. As a result, water in the high pressure drum 7 and the low pressure drum 8 in the exhaust heat recovery boiler 4 evaporates. Thereafter, the outlet steam pressures of the high pressure drum 7 and the low pressure drum 8 are maintained at a predetermined pressure by the high pressure steam bypass valve 11 and the low pressure steam bypass valve 12 until the steam turbine 5 is started.

When the high pressure steam state reaches a state where the steam turbine 5 is started, the output signal of the speed controller 16 selected by the low value selector 20 is increased, the high pressure steam control valve 9 is opened, and the steam turbine 5 is started. Activate it. When the steam turbine 5 reaches the rated speed, the steam turbine generator 6 is connected to the power system and activated until the initial load is secured. During this time, the high pressure steam control valve 9 opens and the exhaust heat recovery boiler 4
The high pressure steam pressure at the outlet of is reduced. Therefore, by closing the high-pressure steam bypass valve 11, the high-pressure steam pressure at the outlet of the exhaust heat recovery boiler 4 is maintained at a predetermined value.

Thereafter, the output signal of the load controller 17 is increased to fully open the high pressure steam control valve 9 and the low pressure steam control valve 10. Accordingly, the high pressure steam bypass valve 11 and the low pressure steam bypass valve 12 are fully closed. During this time, the load limiter 18 follows a signal obtained by adding a positive bias to the output signal of the load controller 17 (not shown), and is not selected by the low value selector 20 in normal operation.

By the way, the steam pressure controller 19 operates until the steam turbine 5 is completely started, that is, until the high pressure steam control valve 9 and the low pressure steam control valve 10 are fully opened.
Switch 19e is operating. Therefore, the steam pressure control signal PM is 100% and is not selected by the low value selector 20. This steam pressure controller 19
The low value selector 20 selects the steam pressure control signal P only when the steam pressure actual measurement signal PA suddenly decreases after the steam turbine 5 has been started and the switch 19e has become inactive.
M is selected.

High pressure steam control valve 9 and low pressure steam control valve 1
0 is designed to hold this position once it is fully opened. Similarly, once the bypass valve is fully closed, it is maintained. The reason is that the output of the gas turbine 1 responds to changes in the generator load relative to the overall output, and the output of the steam turbine generator 6 is determined by the steam condition at the exit of the heat recovery boiler 4. This is because I try to do so. This is because the output of the steam turbine 5 depends on the outlet steam temperature of the exhaust heat recovery boiler 4, and the outlet steam state of the exhaust heat recovery boiler 4 depends on the exhaust gas temperature of the gas turbine 1. Further, the exhaust gas temperature of the gas turbine 1 is determined by the output of the gas turbine 1. Therefore, since the output of the combined cycle depends on the output of the gas turbine 1, the output steam state of the exhaust heat recovery boiler 4 is also controlled by controlling the output of the gas turbine 1.

[0020] The output of the steam turbine 5 is operated under variable pressure operation in which the output steam pressure of the exhaust heat recovery boiler 4 is changed.

In the above-described combined cycle steam cycle, the high pressure steam control valve 9 and the low pressure steam control valve 10
The steam turbine 5 is operated at variable pressure with the high-pressure steam bypass valve 11 and the low-pressure steam bypass valve 12 fully closed. During this variable pressure operation, if a malfunction in the level control of the high-pressure drum 7 and low-pressure drum 8 or a failure of auxiliary equipment such as the high-pressure water supply pump 14 and low-pressure water supply pump 15 occurs, the outlet steam pressure of the high-pressure drum 7 and low-pressure drum 8 That is, the inlet steam pressure of the steam turbine may drop suddenly.

In such a case, if the high-pressure steam control valve 9 and the low-pressure steam control valve 10 are kept fully open, the water in the drum mixes with steam and enters the steam turbine 5. To prevent this, the steam pressure controller 19 detects a sudden drop in steam pressure, and depending on the degree of the sudden drop, quickly closes the high pressure steam control valve 9 and the low pressure steam control valve 10 to prevent the drop in steam pressure. I'm trying to suppress it.

The operation of the steam pressure controller 19 will now be explained in detail.

When the steam pressure actual measurement signal PA suddenly decreases, the steam pressure setting signal PS changes to the limiter 19b and the integrator 19a.
The robot descends at a predetermined slow rate. Therefore, the steam pressure control deviation between the steam pressure setting signal PS and the steam pressure actual measurement signal PA becomes a negative signal. And function generator 19
When reaching the value set for d, that is, the value D1 as shown in FIG. 7, the steam pressure opening degree command starts to gradually decrease. The value of D1 is set to about 10% of the normal rated steam pressure in order to prevent malfunction. Furthermore, the steam control valve opening degree command gradually decreases until the steam pressure control deviation reaches D2. This steam control valve opening command, that is, the steam pressure control signal PM is selected by the low value selector 20. Then, the switch 19c is activated. The setting device 19f is set to zero, so that the steam pressure setting signal PS is held and works to promote a decrease in the steam pressure control signal PM. That is, FIG.
As shown in , when the steam pressure setting signal PS and the steam pressure actual measurement signal PA gradually decrease at time t1, and the steam pressure control deviation becomes D1 at time t2, the steam pressure control signal PM decreases to 10.
It suddenly decreases from 0%.

[0025]

However, the above steam turbine control device has the following problems.

When the steam turbine 5 is operating under variable pressure, the exhaust heat inlet damper 3 may be closed due to an erroneous operation, or due to a failure of the exhaust heat inlet damper 3 or a failure of the controller. In this case, the exhaust gas of the gas turbine 1 is directly discharged to the atmosphere, and the heat input to the waste heat recovery boiler 4 suddenly decreases, so that the steam pressure at the exits of the high pressure drum 7 and the low pressure drum 8, that is,
The steam pressure at the steam turbine inlet suddenly drops. In such a case, similarly to the above, the steam pressure controller 19 closes the high pressure steam control valve 9 and the low pressure steam control valve 10 to suppress the drop in steam pressure.

However, since the reaction of the reduction in the outlet steam pressure of the high pressure drum 7 and the low pressure drum 8 to the decrease in the heat input of the exhaust heat recovery boiler 4 is quick, the inlet steam pressure of the steam turbine 5 decreases rapidly. Therefore, in the operation of the steam pressure controller 19, which detects a decrease in steam pressure and closes the steam control valve, the steam pressure decrease is delayed and the steam turbine 5
There is a problem in that wet steam enters the steam turbine 5 and damages the blades of the steam turbine 5.

For example, as shown in FIG. 9, when the opening degree L of the exhaust heat inlet damper 3 changes stepwise from 100% to 50% at time t1, the steam pressure setting signal P changes accordingly.
S, steam pressure actual measurement signal PA and steam pressure control signal PM
changes as shown. At this time, at time t2, the difference between the steam pressure setting signal PS and the steam pressure actual measurement signal PA produces a steam pressure control deviation D1, so the steam pressure control signal PM is T.
It will operate with a time delay.

Therefore, the present invention provides a steam turbine for a combine power generation plant that can promptly close the steam control valve to prevent wet steam from entering the steam turbine when the exhaust heat inlet damper is closed due to an erroneous operation or the like. The purpose is to provide a control device.

[Configuration of the invention]

[Means for Solving the Problems] The present invention provides a gas turbine, a waste heat recovery boiler for exchanging heat with exhaust gas supplied from the gas turbine via a waste heat inlet damper, and a Input the steam control valve that leads to the steam turbine, the sum of the speed control signal and the load control signal, and the steam pressure control signal to control the opening and closing of the steam control valve. A steam turbine control device for a combined power generation plant comprising a low value selector that selects a control signal and uses it as a steam control valve opening setting signal, the exhaust heat inlet detecting the opening value of the exhaust heat inlet damper or an equivalent value thereof. a damper opening detection means; and a damper opening detecting means for controlling the steam in accordance with a detected value of the exhaust heat inlet damper opening detection means in order to maintain the steam pressure to the steam turbine at a predetermined value when the exhaust heat inlet damper is in a closing operation. The opening limit value calculating means calculates the opening limit value of the control valve or its equivalent value and inputs this calculated value to the low value selector.

[0031]

[Operation] With the above configuration, the steam control valve can be directly controlled by the opening limit value or equivalent value of the steam control valve calculated based on the opening value or equivalent value of the exhaust heat inlet damper, so the exhaust heat Even if the inlet damper closes due to incorrect operation or failure, the steam control valve can be closed without any time delay. This suppresses the drop in steam pressure, prevents wet steam from entering the steam turbine, and protects the blades of the steam turbine.

[0032]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a control block diagram of a steam turbine control device for a combined power generation plant showing one embodiment of the present invention. The same reference numerals as in FIG. 6 indicate the same or equivalent parts. The difference from FIG. 6 is that a function generator 21 and a change rate limiter 22 are newly provided. In this embodiment, the opening signal L of the exhaust heat inlet damper 3 is input to the function generator 21, and the signal output from the function generator 21 is input to the low value selector 20 via the rate of change limiter 22. I try to do that.

The function generator 21 inputs the opening degree signal L of the exhaust heat inlet damper 3, converts this input signal into a signal of a set function as shown in FIG. 2, and outputs it. The function of the function generator 21 is calculated from the flow rate characteristics of the exhaust heat inlet damper 3, the thermal characteristics of the exhaust heat recovery boiler 4, the flow rate characteristics of the steam control valve, etc.

The rate of change limiter 22 limits the output signal of the function generator 21 to a predetermined rate of change and outputs it. The value set in this rate of change limiter 22 is calculated from the maximum rate of change in the steam flow rate of the steam turbine 5.

Next, when the exhaust heat inlet damper 3 is closed due to an erroneous operation or a failure while the steam turbine 5 is in variable pressure operation, the following action occurs.

When the opening signal L of the exhaust heat inlet damper 3 decreases, the function generator 21 to which the opening signal L of the exhaust heat inlet damper 3 is inputted, controls the steam control valve whose function is set as shown in FIG. Outputs the opening limit value. That is, the function generator 21
outputs a command to the rate of change limiter 22 to abruptly close the steam control valve. As a result, the signal through the rate of change limiter 22 is selected by the low value selector 20, closing the steam control valve. Thereby, it is possible to prevent the steam turbine inlet steam pressure from dropping suddenly.

For example, as shown in FIG. 3, when the opening degree signal L of the exhaust heat inlet damper 3 changes stepwise from 100% to 50% at time t1, the output signal of the rate of change limiter 22 is changed to the steam control valve. Immediately, the opening setting signal PB suddenly drops from time t1 and reaches a constant value at time t2. Accordingly, the steam pressure actual measurement signal PA also drops, but it quickly follows this and maintains the predetermined pressure before the change in the opening degree of the exhaust heat inlet damper 3. In this way, when the exhaust heat inlet damper 3 is closed,
The steam control valve closes quickly, and a sudden drop in steam pressure can be suppressed.

If the setting of the function generator 21 differs from the expected characteristics and the steam regulating valve is not sufficiently closed, the steam regulating valve is further closed by the action of the conventional steam pressure controller 19.

Furthermore, in normal operation, from the start of the steam turbine 5 until the stop operation is performed, the exhaust heat inlet damper 3 is fully open, so this implementation will not affect the normal operation. do not have.

Furthermore, when compared with FIG. 9 showing the conventional operating characteristics, it is clear that according to this embodiment, not only a sudden drop in steam pressure is suppressed, but also fluctuations in steam pressure itself are stabilized. It can be done.

FIG. 4 is a control block configuration diagram of a steam turbine control device for a combined power generation plant showing another embodiment of the present invention.

In this embodiment, the passing gas flow rate and the bypass flow rate of the exhaust heat inlet damper 3 are input, and the ratio of the passing gas flow rate to the total exhaust gas flow rate, which is the sum of both signals, is calculated as follows:
The virtual opening degree of the exhaust heat inlet damper 3 is calculated by the divider 23. The function generator 24 calculates a load limit signal for the steam turbine 5 based on the signal calculated by the divider 23. The load limiter 18 operates based on this load limit signal, and the low value selector 20 selects the signal from the load limiter 18.
Controls the steam control valve.

Note that the flow rate of gas passing through the exhaust heat inlet damper 3 is the flow rate input to the exhaust heat recovery boiler 4. Moreover, the bypass flow rate is the flow rate discharged to the atmosphere. The setting function of the function generator 24 is the function shown in FIG. 2 in which the steam control valve opening limit value is changed to a load limit value, and is an equivalent function. This embodiment can also be implemented in the same manner as the embodiment shown in FIG.

[0045]

As described above, according to the present invention, when the exhaust heat inlet damper is closed due to an erroneous operation, the steam control valve can be quickly closed before the steam pressure at the steam turbine inlet suddenly decreases. Suppresses sudden drop in steam pressure. This prevents moisture from being contained in the steam from the high-pressure drum and low-pressure drum. This prevents wet steam from entering the steam turbine and prevents the blades of the steam turbine from being damaged.

[Brief explanation of drawings]

FIG. 1 is a control block configuration diagram of a steam turbine control device for a combined power generation plant showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of characteristics of a function generator of the device.

FIG. 3 is an explanatory diagram showing an example of the operation of the device.

FIG. 4 is a control block configuration diagram of a steam turbine control device for a combined power generation plant showing another embodiment of the present invention.

FIG. 5 is a system diagram showing a combined power generation plant.

FIG. 6 is a control block configuration diagram of a steam turbine control device for a combine power generation plant showing a conventional example.

FIG. 7 is an explanatory diagram showing an example of characteristics of a function generator of the same device.

FIG. 8 is an explanatory diagram showing an example of the operation of the device.

FIG. 9 is an explanatory diagram showing an example of the operation of the device.

[Explanation of symbols]

1 Gas turbine ３　　　　　Exhaust heat inlet damper 4. Exhaust heat recovery boiler 5 Steam turbine 9 High pressure steam control valve 10 Low pressure steam control valve 16 Speed controller 17 Load controller 19 Steam pressure controller 20 Low value selector 21 Function generator 22 Rate of change limiter

Claims (1)

[Claims] Claim 1: A gas turbine, an exhaust heat recovery boiler that exchanges heat with exhaust gas supplied from the gas turbine via an exhaust heat inlet damper, and a steam control valve that guides steam from the exhaust heat recovery gas boiler to a steam turbine. In order to control the opening and closing of this steam regulator, the sum of the speed control signal and the load control signal and the steam pressure control signal are input, and the one with the lowest value among these control signals is selected to open and close the steam regulator. A steam turbine control device for a combined power generation plant comprising a low value selector as an opening setting signal; In order to maintain the steam pressure to the steam turbine at a predetermined value when the exhaust heat inlet damper is in a closing operation, an opening limit value of the steam control valve according to a detected value of the exhaust heat inlet damper opening detection means; A steam turbine control device for a combined power generation plant, comprising an opening limit value calculating means for calculating this equivalent value and inputting this calculated value to the low value selector.