JPH06159091A - Steam injection control equipment - Google Patents

Abstract

PURPOSE:To provide steam injection control equipment having superior following-up to changed set values, inhibiting overshoot or undershoot, and performing good control. CONSTITUTION:A feedback arithmetic circuit 23 computes feedback-wise operation amt. based on steam flow, deflection from a substracter 22 and the control parameter obtd. from plant data in a control gain generator 24. A leading operation amt. arithmetic circuit 25 leading-computes operation at. corresponding to the rate of change in set value based on the set value from a set value arithmetic circuit 21 and the control parameter from the control gain generator 24. These control amounts are added by means of an adder 26 to output as the operation amt. in normal running. An operation amt. switching device 30 selects a signal from a starting-stage operation amt. generator 27 in plant starting-stage state, from the adder 26 in normal running state and from a suspending-stage operation amt. generator 28 in suspending state corresponding to decision result from a state decision device 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam injection control device used for denitration control for reducing nitrogen oxides generated in a gas turbine combustor of a combined cycle power plant.

[0002]

2. Description of the Related Art In recent years, combined cycle power plants combining a gas turbine and a steam turbine using the exhaust gas of the plant have improved the efficiency of the entire plant and, by changing the gas turbine side, use a fuel other than natural gas. Since it can be adopted, it is becoming the mainstream of thermal power plants. This is to drive a gas turbine by burning fuel such as natural gas to generate electricity, recover exhaust heat from the exhaust gas, and generate steam in a boiler called an exhaust heat recovery boiler by this exhaust heat. This steam is used to drive a steam turbine to drive a generator and generate electricity.

Generally, combined cycle power plants include
There are various combinations, but here the simplest example is a combined cycle power plant consisting of one gas turbine generator, one exhaust heat recovery boiler, and one steam turbine generator. , Its operating principle will be explained.

FIG. 4 shows the structure of the above-mentioned combined cycle power plant. In the figure, reference numeral 1 denotes a combustor, in which a fuel such as natural gas is burned. The combustion gas, which has become high temperature and high pressure by this combustion, drives the gas turbine 2 and then becomes exhaust gas and is discharged from the chimney 3 to the outside air. An exhaust heat recovery boiler 4 is installed in the chimney 3, recovers heat from the exhaust gas, and heats water in the boiler to generate steam. The steam generated in the exhaust heat recovery boiler 4 drives the steam turbine 6 through the regulator valve 5 to generate electric power, and then is condensed in the condenser 7 to become water. In the figure, reference numeral 8 is a bypass valve for bypassing the steam turbine 6 and guiding steam to the condenser 7.

Further, since the exhaust gas discharged from the chimney 3 to the outside air contains nitrogen oxides, steam is injected into the combustor 1 in order to reduce the emission amount of the nitrogen oxides. It is being appreciated. As the injected steam, the outlet steam of the exhaust heat recovery boiler 4 or the extracted steam of the steam turbine 6 is used, and these steams are injected into the combustor 1 while controlling the steam flow rate by the steam injection control valve 9, This suppresses the generation of nitrogen oxides in the combustor 1. The control of the steam injection control valve 9 is required to have good followability with respect to the set value in order to suppress the generation of nitrogen oxides, and the flame in the combustor 1 is misfired by causing too much steam to flow. In order to prevent this, it is required that there be no overshoot.

FIG. 5 shows the structure of a conventional steam injection control device for controlling the opening of the steam injection control valve 9 as described above. As shown in the figure, the gas turbine fuel flow rate signal is input to the set value calculator 11, and the set value of the steam flow rate to be flown at that time is calculated based on the gas turbine fuel flow rate. The set value of the steam flow rate is sent to the subtractor 12, and the subtractor 12 calculates the deviation between the set value of the steam flow rate and the actual injected steam flow rate. Then, the deviation of the manipulated variable is calculated in the function generator 13 from the deviation of the steam flow rate, and the manipulated variable calculator 14 is calculated from the deviation of the manipulated variable.
The actual valve operation amount is calculated at.

[0007]

As described above, the following two matters are required in the above steam injection control.

That is, first of all, there is the ability to follow changes in the set value of the steam flow rate into the combustor. Since the emission amount of nitrogen oxides contained in the exhaust gas is regulated, followability to changes in the vapor flow rate set value is very important in order to strictly comply with this.

The second is to prevent overshoot. If overshoot occurs and steam is excessively supplied to the combustor, misfire is caused and a plant trip occurs. In order to prevent this, it is necessary to control so as not to cause overshoot.

However, it is difficult for the above-described conventional steam injection control device to satisfy both of the above two requirements. Further, even if emphasis is placed on suppressing overshoot, there is a problem in that overshoot and undershoot are likely to occur because the set value suddenly changes when the plant is started and stopped. Furthermore, when the operating conditions of the plant differ, the dynamic characteristics and valve characteristics also differ, so even if the same manipulated variable deviation is given, the fluctuation of the actual process value will be different and the controllability will also deteriorate. there were.

The present invention has been made in consideration of such a conventional situation, and has excellent followability with respect to a change in set value, can suppress overshoot and undershoot, and can perform good control. The present invention is intended to provide a steam injection control device capable of performing the same.

[0012]

That is, a steam injection control device of the present invention utilizes a gas turbine driven by combustion gas generated by burning fuel in a combustor and exhaust gas from this gas turbine. In a steam injection control device that controls the opening of a steam injection control valve that adjusts the injection amount of steam injected into the combustor of the combined cycle power plant that combines a steam turbine driven by the generated steam, the plant By inputting data, the combined cycle power plant is in a starting state, is in a stopped state, a state determination means for determining whether a normal operating state,
A startup operation amount generation means for outputting an operation amount at the start of the combined cycle power plant, a stop operation amount generation means for outputting an operation amount at the stop of the combined cycle power plant, and a fuel flow rate of the combustor From the steam flow deviation between the injection steam set value and the actual injection steam flow rate obtained from the operation amount generating means for outputting the operation amount during the normal operation of the combined cycle power plant according to the plant data, and the state An operation amount switching for switching and outputting a signal from the operation amount generating device for starting operation, a signal from the operation amount generating device for stop, and a signal from the operation amount generating device according to the determination result of the determination device. And a manipulated variable calculating unit for generating a valve operating signal of the steam injection control valve based on a signal from the manipulated variable switching unit.

[0013]

In the steam injection control device of the present invention having the above-described structure, at the time of starting and stopping where overshoot or undershoot is likely to occur, the operation amount generating section is automatically switched from the operation amount generation section during normal operation to generate the valve operation signal. Therefore, safe control without overshoot or undershoot is possible.

Further, during normal operation, stable and good followability control is performed by changing the control parameter based on the plant data in consideration of the dynamic characteristics and valve characteristics that change according to the operating state of the plant. It can be performed.

As a result, it is possible to perform control that satisfies both of the two requirements, that is, the followability with respect to the change in the set value required for the steam injection control of the combined cycle power plant and the overshoot does not occur.

[0016]

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

FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, reference numeral 20 indicates a steam injection control device.

Further, as shown in FIG. 2, the steam injection control device 20 controls the valve based on the gas turbine fuel flow rate, the injection steam flow rate, and plant data such as load, steam flow rate, differential pressure, and steam pressure. The operation signal is output as a current signal, and this current signal is converted into air pressure by the current / air pressure converter 50 to open / close the steam injection control valve 9 using the air pressure actuator.

As shown in FIG. 1, the steam injection control device 20
Is a set value calculator 21, a subtractor 22, a feedback calculator 23, a control gain generator 24, a preceding manipulated variable calculator 25, an adder 26, and a startup manipulated variable generator 27.
The operation amount generator 28 at the time of stop, the state determination device 29, the operation amount switching device 30, and the operation amount calculator 31.

The set value calculator 21 receives the gas turbine fuel flow rate signal, calculates the set value of the injected steam flow rate based on the gas turbine fuel flow rate, and subtracts the set value of the injected steam flow rate from the subtractor 22 and the preceding unit. It is sent to the manipulated variable calculator 25.

The subtractor 22 calculates a steam flow rate deviation from the set value of the injected steam flow rate sent from the set value calculator 21 and the actual injected steam flow rate, and the calculated steam flow rate deviation is fed back to the feedback calculator 23. And sent to the state determiner 29.

On the other hand, plant data such as load, steam flow rate, differential pressure, steam pressure and the like are input to the control gain generator 24 and the state determiner 29. In the control gain generator 24, a control parameter used for calculating the manipulated variable in the feedback computing unit 23 and the preceding manipulated variable computing unit 25 is obtained from the input plant data, and this control parameter is calculated in the feedback computing unit 23 and the preceding computing unit. It is sent to the manipulated variable calculator 25.

In the feedback calculator 23, the subtractor 2
A feedback manipulated variable is calculated based on the steam flow rate deviation from 2 and the control parameter from the control gain generator 24. At the same time, in the preceding manipulated variable calculator 25, based on the set value of the injection steam flow rate from the set value calculator 21 and the control parameter from the control gain generator 24, the manipulated variable corresponding to the set value change rate is set in advance. Calculate to.

Then, these feedback calculators 23
And the manipulated variables calculated by the preceding manipulated variable calculator 25 are added by the adder 26 and output to the manipulated variable switching unit 30 as the manipulated variables during normal operation.

On the other hand, the starting operation amount generator 27 and the stopping operation amount generator 28 generate the operation amount signals used when starting and stopping the plant. These signals are
For example, the signal is set to increase or decrease the operation amount at a constant rate.

The state determiner 29 determines whether the plant is in a start, normal operation, or stop state based on the plant data such as load, steam flow rate, differential pressure, and steam pressure, and the steam flow rate deviation from the subtractor 22. Is always determined, and the determination result is output to the manipulated variable selector 30.

In the manipulated variable switching unit 30, the state determining unit 2
According to the determination result of 9, when the plant is in the starting state, the signal from the startup manipulated variable generator 27, when the plant is in the normal operating state, the signal from the adder 26, and when the plant is in the stopped state A signal from the manipulated variable generator during stop 28 is selected and output to the manipulated variable calculator 31.

Then, the manipulated variable calculator 31 integrates the manipulated variable deviation based on these signals from the manipulated variable switch 30 and outputs a current signal (for example, 4 to 20 m) as a valve operating signal.
The current signal of A) is output. This valve operation signal is converted into air pressure by the current / air pressure converter 50 shown in FIG. 2, and the opening / closing control of the steam injection control valve 9 using the air pressure actuator is performed.

As described above, in the steam injection control device 20 of this embodiment, the change rate of the set value of the injection steam flow rate calculated by the set value calculator 21 is changed to the set value change rate in the preceding manipulated variable calculator 25. Tracking performance can be improved by calculating the corresponding operation amount in advance and adding this signal to the control value. Further, by changing the control parameter in consideration of the dynamic characteristic and the valve characteristic that change according to the operating state of the plant, it is possible to prevent overshoot and undershoot and perform stable and favorable control. Furthermore, since the set value changes when starting and stopping, overshoot and undershoot easily occur,
At the time of such start and stop, an overshoot or undershoot occurs by increasing or decreasing the operation amount at a constant rate based on the signals from the startup operation amount generator 27 and the stop operation amount generator 28. There is no safe control possible.

As a result, it is possible to perform control that satisfies both of the two requirements, that is, followability with respect to a change in set value required for steam injection control of a combined cycle power plant, and that overshoot does not occur.

In the above embodiment, the output of the steam injection control device 20 is used as a current signal, and the steam / injection control valve 9 is opened / closed by using the current / air pressure converter 50. The output of the injection control device 20 may be a pulse signal, and the steam / injection control valve 9 may be opened / closed using a pulse / pneumatic pressure converter. In this case, since the integration function is included in the pulse / pneumatic pressure converter, the manipulated variable selector 30 serves as a pulse generator that outputs a pulse signal corresponding to the manipulated variable deviation. Furthermore, if an electric actuator is used instead of the pneumatic actuator, the pulse signal can be directly input to the electric actuator.

In the above embodiment, the advance manipulated variable calculator 25 is used in order to improve the followability with respect to the change in the set value. However, by adding the precedent manipulated variable calculator for a sudden change in the injection steam flow rate, It is also possible to safely control the injection steam flow rate against sudden changes in the plant.

Further, the steam injection control device 20 shown in FIG.
Like a, plant data such as load, steam flow rate, steam pressure, etc. is input to the preceding manipulated variable calculator 25a, and a manipulated variable deviation is obtained by using necessary one of these plant data according to the purpose of control. And adder 2 as the control value
6 can be added to further improve the controllability.

[0034]

As described above, according to the steam injection control device of the present invention, the followability with respect to the set value change is excellent,
Moreover, overshoot and undershoot can be suppressed, and good control can be performed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a steam injection control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a main configuration of a plant in which the steam injection control device of FIG. 1 is arranged.

FIG. 3 shows a configuration of a steam injection control device according to another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a combined cycle power plant.

FIG. 5 is a diagram showing a configuration of a conventional steam injection control device.

[Explanation of symbols]

 20 Steam injection control device 21 Set value calculator 22 Subtractor 23 Feedback calculator 24 Control gain generator 25 Preceding manipulated variable calculator 26 Adder 27 Startup manipulated variable generator 28 Stop manipulated variable generator 29 State determiner 30 Operation amount switching device 31 Operation amount calculator

Claims (2)

[Claims] 1. A composite system in which a gas turbine driven by combustion gas generated by burning fuel in a combustor and a steam turbine driven by steam generated by using exhaust gas of the gas turbine are combined. In the steam injection control device that controls the opening degree of the steam injection control valve that adjusts the injection amount of the steam injected into the combustor of the cycle power plant, input plant data, and the combined cycle power plant is in the start state. There is, a state determination means for determining whether it is in a stopped state or a normal operation state, a startup operation amount generation means for outputting an operation amount at startup of the combined cycle power plant, and the combined cycle power plant Stop manipulated variable generation means for outputting the manipulated variable at the time of stop, and the injection steam set value obtained from the fuel flow rate of the combustor and the actual injection Deviation of steam flow rate from air flow rate, operation amount generation means for outputting the operation amount at the time of normal operation of the combined cycle power plant according to the plant data, and depending on the determination result of the state determination means, the start A signal from the operation amount switching means, a signal from the stop operation amount generating means, and a signal from the operation amount generating means for switching and outputting the signal, and a signal from the operation amount switching means And a manipulated variable calculating means for generating a valve operation signal of the steam injection control valve based on the above. 2. The steam injection control device according to claim 1, wherein the manipulated variable generating means for outputting the manipulated variable during the normal operation of the combined cycle power plant is calculated according to the steam flow rate deviation and the plant data. A steam injection control device, wherein a manipulated variable calculated according to the rate of change of the injection steam set value and the plant data is added to the manipulated variable.