JP2001263003A - Steam pressure control method of steam turbine and controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam pressure controlling method of a steam turbine and a controller capable of reducing throttle loss in a speed regulating valve 5 and capable of improving turbine performance by switching opening control of the speed regulating valve from the other controller to constantly control main steam pressure by a main steam pressure controller while holding an all opening period of the speed regulating valve in a long period. SOLUTION: In the steam pressure control method of the steam turbine and the device, a multi-valve type speed regulating valve composed of a plurality of valves is used as a speed regulating valve for regulating main steam pressure. When a detecting value of main steam pressure is larger than the minimum main steam pressure which is set beforehand, a plurality of valves are fully closed in order, and an opening of the speed regulating valve is reduced. When only one valve is fully opened and the main steam pressure detecting value is smaller than the minimum main steam pressure, valve opening control is changed into main steam pressure control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a steam pressure of a steam turbine used in a combined power generation system equipped with a gas turbine and a control device used for the steam pressure control.

[0002]

2. Description of the Related Art FIG. 5 is a system diagram showing an example of a combined cycle power plant that drives a steam turbine using waste heat of a gas turbine. In FIG. 5, 1 is a gas turbine, 2 is a generator driven by the gas turbine 1, and 3 is a waste gas boiler that generates steam G by heat of exhaust gas H introduced from the gas turbine 1 through an exhaust gas pipe 25. Reference numeral 4 denotes a steam turbine driven by steam G generated in the waste gas boiler 3 and introduced through the steam supply pipe 11, and reference numeral 12 denotes a generator driven by the steam turbine 4. 5 is a speed regulating valve for adjusting steam G introduced into the steam turbine 4;
13 is a breaker for the generator 12, and 14 is a power system.

[0003] In such a combined cycle power plant, exhaust gas H discharged from the gas turbine 1 is sent to a waste gas boiler 3 through an exhaust gas pipe 25, where water is heated to generate steam G. This steam G is sent to the steam turbine 4 through the steam supply pipe 11 and the speed regulating valve 5, and drives the steam turbine 4 to obtain the power of the generator 12. And the steam supply pipe 11
The main steam pressure of the steam G sent to the steam turbine 4 through is controlled by controlling the opening of the speed control valve 5.

FIG. 6 shows an example of a prior art operation control system for a steam turbine in which the opening of the governing valve 5 is controlled. In FIG. 6, 6 is a main steam pressure control device, 10 is a control device for controlling other elements, and 8 is low (L
ow) It is a selector. Reference numeral 9 denotes a pressure sensor which detects the steam pressure of the steam supply pipe 11 on the upstream side of the speed regulating valve 5 and inputs the detected steam pressure to the main steam pressure control device 6. Other configurations are the same as those in FIG. 5, and the same members are denoted by the same reference numerals.

In the operation control system shown in FIG. 6, the governor 5 is opened to operate the steam turbine 4, and the breaker 1
3 and the generator 12 is operated in parallel with the power system 14, and at the same time, the generator 12 starts power generation. Thereafter, normally, the governing valve 5 is fully opened and the steam turbine 4
To perform variable pressure operation in which the main steam pressure changes to Main steam pressure is reduced in the steam supply pipe 11, the smaller the measured value P ₁ of the main steam pressure by the pressure sensor 9, governor valve opening output f ₁ of the main steam pressure control device 6 is the other becomes smaller than the output f ₂ from the control unit 10 of, said row selector 8 is operated, thereby to control the 5 speed governor valve selects the output of the main steam pressure control device 6,該調speed valve 5 Is controlled by switching to the constant steam pressure control by PID (proportional, integral, differential) control by the main steam pressure control device 6 for performing PID (proportional, integral, differential) control.

[0006]

However, as shown in FIG. 6, in the prior art method or apparatus for controlling the opening of the governing valve 5 by the steam turbine operation control method and apparatus, the governing valve is not used. 5 has a problem that the throttle opening in the governing valve 5 is increased due to the relatively short full opening period.

In view of the above-mentioned problems of the prior art, the present invention switches the control of the opening of the speed control valve from another control device to the constant control of the main steam pressure by the main steam pressure control device during the full opening of the speed control valve. It is an object of the present invention to provide a steam pressure control method and a control device for a steam turbine in which the throttle loss in the governing valve 5 is reduced and the turbine performance is improved.

[0008]

The present invention solves this problem.
The invention described in claim 1 is applied to a steam turbine.
The opening of the governing valve provided in the steam supply pipe that supplies the main steam
By changing the main steam pressure of the steam turbine.
Pressure Control Method of Steam Turbine Adjusting Pressure
, Wherein the speed regulating valve is a multi-valve comprising a plurality of valves.
The main steam pressure in the steam supply pipe using a speed control valve of the type
Force measurement P₁And minimum main steam pressure set value P _MINCompare with
Then P₁≧ P_MIN  In the case of, the plurality of valves are sequentially closed fully, and one valve
Only when it is open, P₁<P_MIN  When the main steam pressure is controlled by controlling the opening of the valve.
Steam pressure control for steam turbine characterized by transition
Suggest a method.

According to a fourth aspect of the present invention, there is provided an apparatus for carrying out the first aspect of the present invention, wherein an opening of a governing valve provided in a steam supply pipe for supplying main steam to a steam turbine is changed. In the steam pressure control device for a steam turbine configured to adjust the main steam pressure of the steam turbine, the speed control valve uses a multi-valve type speed control valve including a plurality of valves; A pressure sensor for detecting a main steam pressure of the pipe; and a plurality of valves when a detected value of the main steam pressure from the pressure sensor is input and the detected main steam pressure value is larger than a preset minimum main steam pressure. Are sequentially closed to reduce the governing valve opening, and when only one valve is fully opened and the main steam pressure detection value is smaller than the minimum main steam pressure, the main control by the valve opening control is performed. Shift to steam pressure control Characterized by comprising the occupied governor valve control means.

According to a second aspect of the present invention, in the first aspect, at least one of the plurality of valves is provided before transition to main steam pressure control based on opening control of only one of the valves.
It is characterized in that the two valves are kept in a fully open state. Also,
A third aspect of the present invention is characterized in that, in the first aspect, when the plurality of valves shift to the fully closed state, the opening degree of each of the valves is controlled to decrease at a constant rate of change.

According to this invention, a multi-valve type regulating valve having a plurality of valves is provided, and when the opening degree of the regulating valve is reduced, the regulating valve is controlled by the regulating valve control means. By fully closing one valve at a time from full open of a plurality of valves constituting one, and leaving one valve in a fully open state,
In the governing valve opening before the throttle control of the one valve is started,
At least one valve may be fully open. As a result, the period (time) during which the governing valve is fully opened is significantly extended as compared with the conventional one, and the throttle loss of the governing valve is reduced.

According to the third aspect of the present invention, in the process of closing each of the plurality of valves constituting the governing valve, the opening degree of the valve is controlled by the regulating valve control means. Since it is controlled to decrease at a constant rate of change,
The time until the valve is fully closed is shortened, the throttle loss in the valve is minimized, and the generation of noise when the valve is closed is also suppressed. Further, the plurality of valves constituting the governing valve are individually closed, and the plurality of valves are not simultaneously closed, so that the throttle loss or noise is minimized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, unless otherwise specified. It is only an example.

FIG. 1 is a control block diagram of a steam pressure control device for a steam turbine according to an embodiment of the present invention, FIG. 2 is a control flowchart, FIG. 3 is an explanatory diagram of a speed control valve control method, and FIG. FIG. 4 is a diagram for explaining the operation of the method.

The present invention is applied to a combined gas turbine / steam turbine power generation system as shown in FIG. In FIG. 5, 1 is a gas turbine, 2 is a generator driven by the gas turbine 1, and 3 is a waste gas boiler that generates steam G by heat of exhaust gas H introduced from the gas turbine 1 through an exhaust gas pipe 25. Reference numeral 4 denotes a steam turbine driven by steam G generated in the waste gas boiler 3 and introduced through the steam supply pipe 11, and reference numeral 12 denotes a generator driven by the steam turbine 4. Reference numeral 5 denotes a speed regulating valve for adjusting the steam G introduced into the steam turbine 4, reference numeral 13 denotes a breaker for the generator 12, and reference numeral 14 denotes a power system.

In such a combined cycle power plant, exhaust gas H discharged from the gas turbine 1 is sent to a waste gas boiler 3 through an exhaust gas pipe 25, where the feedwater is heated to generate steam G. This steam G is sent to the steam turbine 4 through the steam supply pipe 11 and the speed regulating valve 5, and drives the steam turbine 4 to obtain the power of the generator 12. And the steam supply pipe 11
The main steam pressure of the steam G sent to the steam turbine 4 through is controlled by controlling the opening of the speed control valve 5.

The present invention relates to an improvement in an opening control system of the governing valve 5 for adjusting the main steam pressure to the steam turbine 4 of the combined power generation system. In FIG. 1, which shows a control block diagram of a steam pressure control device according to an embodiment of the present invention, 6 is a main steam pressure control device, 10 is a control device for controlling other elements, and 7 is a speed control forming the gist of the present invention. It is a valve fully open control device. A low selector 8 switches the control of the governing valve 5 between the control by the main steam pressure control device 6 and the control by another control device 10 and the control device 7 for fully opening the governing valve. Reference numeral 9 denotes a pressure sensor,
5, the steam pressure on the upstream side of the speed control valve 5 is measured (detected), and the main steam pressure control device 6 and the speed control valve fully open control device 7 are measured.
Is to be entered.

In the present invention, as shown in FIG. 3, the speed regulating valve 5 is composed of a plurality of valves (three in this example), that is, one valve 5a, two valves 5b and three valves 5c. It is a so-called multi-valve type speed regulating valve. The regulating valve fully open control device 7 keeps the measured value of the main steam pressure by the pressure sensor 9 equal to or more than P _MIN , and always opens one valve (5a) fully, two valves (5b) fully open, or three valves. (5c)
One of the fully opened positions is set, and the opening control of the governing valve 5 is performed at a constant opening change rate between these fully opened positions. Other configurations are the same as those of FIG. 6, and the same members are denoted by the same reference numerals.

Next, the operation of this embodiment will be described with reference to FIGS. In the control block diagram shown in FIG. 1, the governor 5 is opened, the steam turbine 4 is operated, the breaker 13 is turned on synchronously, and the generator 12 is connected to the power system 1.
4 and the generator 12 starts power generation at the same time. Thereafter, normally, the governing valve 5 is fully opened, and a variable pressure operation in which the main steam pressure to the steam turbine 4 changes is performed. Main steam pressure is reduced in the steam supply pipe 11, the smaller the measured value P ₁ of the main steam pressure by the pressure sensor 9, governor valve opening output f ₁ of the main steam pressure control device 6 is the other becomes smaller than the output f ₂ from the control unit 10 of, said row selector 8 is operated, thereby to control the 5 speed governor valve selects the output of the main steam pressure control device 6,該調speed valve 5 Is controlled by switching to the constant steam pressure control by PID (proportional, integral, differential) control by the main steam pressure control device 6 for performing PID (proportional, integral, differential) control. The above operation is the same as that of the conventional technique shown in FIG.

Next, the opening / closing control operation of the multi-valve type regulating valve 5 which forms the gist of the present invention will be described with reference to FIGS. In the control flowchart of FIG. 2, when the steam turbine 4 is started, the main steam G is sent from the waste gas boiler 3 to the steam turbine 4.
Is supplied through the steam supply pipe 11 (step (1)). After that, when the breaker 13 is turned on synchronously and put into the power system 14, the generator 12 starts power generation at the same time (steps (2) and (3)), and the governing valve 5 is fully opened to perform other control. The steady operation by the device 10 is performed, and the load increases (step (4)). In this state, all the valves (one valve 5a, two valves 5b, and three valves 5c) shown in FIG. 3D are fully opened (step (5)).

During the steady operation, the steam supply pipe 1
1, the pressure of the steam G, ie, the main steam pressure P₁Is a pressure sensor
9 (step (6)), and the control valve
Is input to the opening control device 7 and the minimum main steam pressure set value P_MIN
Is compared every moment. (Step (7)). And this ratio
The comparison result is P₁≧ P_MIN  During the period, the regulating valve 5 is opened by the regulating valve full-open control device 7.
Maintain full open state of all valves, reduce main steam pressure, P₁<P_MIN  In the case of, one valve (3 valves) as shown in FIG.
5c) is fully closed, and the remaining two valves (1 valve 5a, 2 valve 5
Continue valve full-open control with b) fully open (step
(9)).

In this process, the full valve is fully opened (FIG. 3).
When changing from (d)) to two valves fully open (FIG. 3 (c)), a three-valve 5c fully closed process shown in FIG. 3 (g) is performed. , The regulating valve fully open control device 7
Is controlled so as to decrease at a constant rate of change (step (8)).

The three valves 5c are closed and two valves (one valve 5) are closed.
a, 2 valve 5b) When the governing valve opening decreases due to full opening,
Vapor pressure P₁Rises. And the main steam pressure P₁And most
Low main steam pressure set value P_MINIs related to P₁≧ P_MIN  Between the two, the control valve full-open control device 7
The state where the valve is fully opened (FIG. 3 (c)) continues, but the pressure
(Step (10)) Measured by the sensor 9
Main steam pressure P input to speed-control valve fully open control device 7₁Decreases
And P₁<P_MIN  (Step (11)), the state shown in FIG.
Thus, the other one valve (two valves 5b) is fully closed,
Valve full-open control with the remaining one valve (one valve 5a) fully opened
Continue (step (13)).

In this process, when changing from the full opening of the two valves (FIG. 3C) to the full opening of one valve (FIG. 3B), the two valves 5b shown in FIG. After a full closing process, the opening of the two-valve 5b is controlled by the control valve full-open control device 7 so as to decrease at a constant rate of change (step (12)).

The three valves 5c and the two valves 5b are closed, and one
Valve (1 valve 5a) is fully opened and the governing valve opening is further reduced
Then, the main steam pressure P₁Rises. And the main steam
Pressure P ₁And minimum main steam pressure set value P_MINIs related to P₁≧ P_MIN  During the period, the control valve full-open control device 7
The state where the valve is fully opened (FIG. 3B) continues. And said
Before being measured by the pressure sensor 9 (step (14))
Main steam pressure P input to the governing valve fully open control device 7₁Is low
Down, P₁<P_MIN  (Step (15)), the main steam pressure
The output of the control device 6 is higher than the output of the governing valve
When it becomes smaller, the low selector 8 operates and the speed regulating valve 5
Control is switched to constant steam pressure control by the main steam pressure controller 6.
(Step (16)). This state is shown in FIG.
As shown in the figure, by squeezing one valve, that is, one valve 5a
This is a constant vapor pressure control.

As described above, according to this embodiment, the multi-valve type speed regulating valve 5 having a plurality of valves is provided. The fully-open valve control device 7 changes the fully-opened valve shown in FIG.
After fully opening the two valves shown in (c), 1 shown in FIG.
By switching to full open of two valves,
In the opening of the governing valve (5) before the throttle control of one valve is started as shown in (e), at least one valve can be fully opened, and thus, the period during which the governing valve 5 is fully opened (Time) is significantly increased as compared with the conventional one, and the throttle loss of the valve is reduced.

In the process of closing individual valves constituting a plurality of valves constituting the speed regulating valve 5, FIG.
As shown in (e), (f) and (g), the opening degree of the valve is controlled by the control valve full-open control device 7 so as to decrease at a constant rate of change. Abrupt area change in the flow path is avoided, so that the flow path area changes smoothly, whereby the throttle loss in the valve is minimized and the generation of noise when the valve is closed is also suppressed. In addition, the plurality of valves constituting the governing valve 5 are individually closed, and the plurality of valves are not simultaneously closed, so that the throttle loss or noise is minimized.

FIG. 4 shows the case of the above-described steam pressure control method and control apparatus according to the embodiment of the present invention (A in FIG. 4).
A comparison of the main steam flow rate (a), the main steam pressure (b), and the valve opening period (c) of the governing valve 5 is shown for the case of the prior art (B in the figure). As shown in FIG. 4C, in the case (A) of the present invention, the fully open period (hour) of the governing valve 5
Are greatly enlarged from a1, a2, and a3 as compared with the prior art (B), and the aperture loss is significantly reduced.

[0029]

As described above, according to the present invention, the opening degree of the multi-valve type regulating valve having a plurality of valves is increased by one degree from the full opening of the plurality of valves constituting the regulating valve. By sequentially closing the two valves until they are fully opened, at least one valve can be kept fully open at the governing valve opening before the throttle control of the one valve is started. As a result, the period (time) during which the governing valve is fully opened is significantly increased as compared with the conventional one, the throttle loss of the governing valve is reduced, and the turbine performance is improved.

Further, according to the present invention, the opening degree of each of the plurality of valves when the valve is closed is controlled so as to decrease at a constant rate of change. Therefore, the time until the valve is fully closed is shortened, the throttle loss in the valve is minimized, and the generation of noise when the valve is closed is also suppressed. Further, the plurality of valves constituting the speed regulating valve are individually closed, and the plurality of valves are not simultaneously closed, so that the throttle loss or the generation of noise can be minimized.

[Brief description of the drawings]

FIG. 1 is a control block diagram of a steam pressure control device for a steam turbine according to an embodiment of the present invention.

FIG. 2 is a control flowchart of the main steam pressure control device.

FIG. 3 is an explanatory diagram of a governing valve control method.

FIG. 4 is a diagram for explaining the operation of the governing valve control method.

FIG. 5 is a system diagram of a combined cycle power plant to which the present invention is applied.

FIG. 6 is a block diagram of a main steam pressure control device for a steam turbine according to the related art.

[Explanation of symbols]

 Reference Signs List 4 steam turbine 5 speed control valve 5a 1 valve 5b 2 valve 5c 3 valve 6 main steam pressure control device 7 speed control valve fully open control device 8 LOW selector 9 pressure sensor 10 other control device 11 steam supply pipe 12 generator 13 Breaker 14 Power system

Claims (4)

[Claims] 1. A steam supply for supplying main steam to a steam turbine.
By changing the opening of the governing valve provided on the supply pipe
A steam having a main steam pressure of the steam turbine adjusted.
In the steam turbine pressure control method,
Use a multi-valve type governor consisting of multiple valves
The measured value P of the main steam pressure in the steam supply pipe₁And the lowest Lord
Steam pressure set value P_MINAnd P₁≧ P_MIN  In the case of, the plurality of valves are sequentially closed fully, and one valve
Only when it is open, P₁<P_MIN  When the main steam pressure is controlled by controlling the opening of the valve.
Steam pressure control for steam turbine characterized by transition
Method. 2. The method according to claim 1, wherein at least one of the plurality of valves is held in a fully open state before a shift to the main steam pressure control by the opening control of only one of the valves. Item 3. A method for controlling steam pressure of a steam turbine according to Item 1. 3. The steam pressure control of a steam turbine according to claim 1, wherein when the plurality of valves are shifted to the fully closed state, the opening degree of each of the valves is controlled to decrease at a constant rate of change. Method. 4. The steam of a steam turbine configured to adjust a main steam pressure of the steam turbine by changing an opening of a governing valve provided in a steam supply pipe for supplying main steam to the steam turbine. In the pressure control device, the speed control valve uses a multi-valve type speed control valve including a plurality of valves, and detects a main steam pressure of the steam supply pipe and a main steam pressure of the main steam pressure from the pressure sensor. When the detected value is input and the detected value of the main steam pressure is larger than the preset minimum main steam pressure, the plurality of valves are sequentially fully closed to reduce the governing valve opening, and only one valve is fully opened. A steam turbine provided with a governing valve control means for shifting to main steam pressure control by controlling the opening degree of the valve when the detected value of the main steam pressure becomes smaller than the minimum main steam pressure. Steam pressure Control device.