JP2000008809A - Steam pressure control method and its device for steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the control responsiveness by selecting the control by a main steam pressure controller in the case when a measured value of the main steam pressure is lower than a predetermined value, and controlling the opening with a constant rate of change to achieve the optimum opening as a target value in the case when a measured value of the opening of a speed governing valve is larger than the optimum opening. SOLUTION: A generator 16 is operated, a speed governing valve 5 is fully opened and the steady operation is performed by a controller 6 when the steam is supplied from a steam supply tube 15 to a steam turbine 4, and then a breaker 17 is closed to energize an electric power system 18. On this occasion, the pressure of the steam is measured by a pressure sensor 9, a measured value is compared with a predetermined value by a main steam pressure controller 7, and the control by the main steam pressure controller 7 is selected by a low selector 8 when the measured value is lower than the predetermined value. Further the opening of a speed governing valve 5 is measured by an opening sensor 14, a measured value is compared with the optimum opening by a speed governing valve controller 12, and the opening of the speed governing valve 5 is changed (reduced) by a constant rate of change to achieve the optimum opening as a target value.

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 and a control device used for controlling the steam pressure.

[0002]

2. Description of the Related Art FIG. 4 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. 4, 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 a steam supply pipe 15, and reference numeral 16 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;
17 is a breaker for the generator 16, and 18 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. The steam G is sent to the steam turbine 4 through the steam supply pipe 15 and the governing valve 5, and drives the steam turbine 4 to obtain the power of the generator 16. Then, the steam supply pipe 15
The 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. 5 shows an example of a prior art steam turbine operation control system for controlling the opening of the governing valve 5. As shown in FIG. In FIG. 5, 7 is a main steam pressure control device, 6
Is a control device for controlling other elements, and 8 is a low selector. Reference numeral 9 denotes a pressure sensor,
The steam pressure on the upstream side of the speed control valve 5 is detected and input to the main steam pressure control device 7. Other configurations are the same as those in FIG. 4, and the same members are denoted by the same reference numerals.

In the operation control system shown in FIG. 5, when the breaker 17 is turned on in synchronization with the power system 18, the generator 16 starts generating power at the same time. Thereafter, the steam turbine 4 which normally operates with the governor valve 5 fully opened is subjected to a pressure changing operation. However, the main steam pressure in the steam supply pipe 15 decreases, and the measured value P ₁ of the main steam pressure by the pressure sensor 9 is obtained. Becomes smaller, and the governing valve opening degree output f _{1 of the} main steam pressure controller 7 is reduced.
Is smaller than the output f ₂ from the control device 6,
The low selector 8 operates to connect the speed regulating valve 5 to the main steam pressure control device 7. As a result, the opening of the governing valve 5 becomes
The steam pressure is adjusted by constant steam pressure control by PID (proportional, integral, differential) control performed by the main steam pressure control device 7.

[0006]

However, in the conventional steam turbine operation control method and apparatus as shown in FIG. 5, the control from the control unit 6 to the main steam pressure control unit 7 is switched. Since the control of the governing valve 5 until the main steam pressure is established is PID (proportional, integral, differential) control, it takes time to stop after the control is switched as described above, and good response is obtained. There is a problem that it is difficult to operate the plant.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention controls the opening of the governing valve from another control device by a main steam pressure control device based on a comparison result between a measured value and a set value of the main steam pressure. Responsiveness of steam turbine control by shortening the settling time when switching to
An object of the present invention is to provide a method and a device for controlling a steam pressure of a steam turbine in which adjustment of control elements is simplified.

[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.
Steam pressure control of a steam turbine with regulated power.
In the method, the main steam pressure measurement (P₁ ) And settings
Value (P₀ ), And the measured value (P ₁ ) Is the set value (P
₀ ), Control by the main steam pressure controller
Move to the step of selecting the selection, in which the set value
(P₀ ) Can be maintained at the optimum opening (K₀ )When
The measured value of the opening of the governing valve (K₁ Measurement)
Value (K₁ ) Is the optimal opening (K₀ ) Is greater than
Suitable opening (K₀ Constant rate of change of governor opening with target value
And the opening measurement value (K₁ ) Is the optimal opening
(K₀ ) When the ratio becomes less than the above, the constant rate of change control is released.
It is in.

According to a second aspect of the present invention, in the first aspect of the present invention, a main steam flow rate (Q ₁ ) in the steam supply pipe is measured, and the optimum opening degree (Q ₁ ) is determined based on the flow rate measurement value (Q ₁ ). K ₀ ) is calculated.

According to a third aspect of the present invention, in the first aspect of the present invention, when the measured value (K ₁ ) of the opening of the governing valve falls below the optimum opening (K ₀ ), The opening of the governing valve output from the steam pressure control device is tracked to the optimum opening (K ₀ ) so that switching can be performed without a sudden change to the valve opening. .

[0011] The invention according to claims 4 and 5 is an invention for an apparatus for suitably implementing the method according to claims 1 to 3, and the invention according to claim 4 is directed to a steam for supplying main steam to a steam turbine. In a steam pressure control device for a steam turbine configured to adjust a main steam pressure of the steam turbine by changing an opening of a speed regulating valve provided in a supply pipe, a pressure for measuring the main steam pressure is used. A sensor, a main steam pressure control device for comparing the measured value of the main steam pressure with a set value and outputting a control signal of the governing valve opening, and an opening sensor for measuring the opening of the regulating valve And comparing the optimal opening of the governing valve with the measured value of the opening, and while the measured value of the opening is larger than the optimal opening, the regulating valve opening having the optimal opening as a target value Control valve that controls the rate of change of air temperature, and main control A selector for switching the control of the governing valve to the governing valve control device while the governing valve opening is larger than the optimal opening after the control of the governing valve is switched to the pressure control device. That is.

According to a fifth aspect of the present invention, in the fourth aspect, a flow sensor for measuring a flow rate of the main steam and an opening calculator for calculating the optimum opening based on a flow rate measured by the flow sensor are provided. Be prepared.

According to this invention, when the result of comparison between the measured value (P ₁ ) of the main steam pressure and the set value (P ₀ ) in the main steam pressure control device becomes P ₁ <P ₀ , the selector is set to the above-mentioned condition. The control by the main steam pressure control device, that is, the measurement value (P
₁ ) and control of the governing valve opening by PID control by comparing the set value (P ₀ ). At the same time, the control of the governing valve control device is performed, and the measured value (K ₁ ) of the governing valve opening measured by the opening sensor is input to the governing valve control device. In the governing valve control device, the optimal opening (K ₀ ) of the governing valve calculated based on the measured value of the main steam flow rate or the like is compared with the measured opening degree (K ₁ ), and K ₁ > K _{During 0} , control is performed with a constant rate of change of the governing valve opening with the optimal opening (K ₀ ) as a target value.

The measured value of the opening (K₁ ) Is optimal
Opening (K₀ ) When the following is input to the governing valve controller
The output from the main steam pressure controller is
(K ₀ ) And tracked by the selector
From the control by the governing valve control device to the main steam pressure control device.
No sudden change in the governing valve opening during PID control
Can be switched to

Therefore, according to the invention, when switching from the control by another control device to the control by the main steam control device, the control valve opening is adjusted at a constant rate by the control valve control device. By controlling so as to shift to the opening, the settling time is significantly shortened compared to the prior art, and the responsiveness is improved.

[0016]

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 unless otherwise specified, and are merely illustrative examples. Only.

The present invention is applied to a combined gas turbine / steam turbine power generation system as shown in FIG.

In FIG. 4, 1 is a gas turbine, 2 is a generator driven by the gas turbine 1, and 3 is a steam G by the heat of the waste gas H introduced from the gas turbine 1 through the gas pipe 25. 4 is a steam turbine driven by steam G generated in the waste gas boiler 3 and introduced through the steam supply pipe 15, and 16 is a generator driven by the steam turbine 4. 5 is a speed regulating valve for adjusting steam G introduced into the steam turbine 4;
7 is a breaker for the generator 16, and 18 is a power system.

In such a combined cycle power plant, the exhaust gas H discharged from the gas turbine 1 is sent to the waste gas boiler 3 through the exhaust gas pipe 25, where the feed water is heated to generate steam G. The steam G is sent to the steam turbine 4 through the steam supply pipe 15 and the governing valve 5, and drives the steam turbine 4 to obtain the power of the generator 16. The pressure (main steam pressure) of the main steam supplied to the steam turbine 4 is controlled by adjusting the opening of the speed control valve 5.

The present invention relates to an improvement in the 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.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, 7 is a main steam pressure control device, 6 is a control device for controlling other elements, 8 is a low selector, The control of the governing valve 5 is switched between the control by the main steam pressure control device 7 and the control by another control device 6. Reference numeral 9 denotes a pressure sensor which measures (detects) a steam pressure on the upstream side of the speed regulating valve 5 of the steam supply pipe 15 and inputs the measured pressure to the main steam pressure control device 7. Reference numeral 10 denotes a flow rate sensor for measuring the main steam flow rate of the steam supply pipe 15, and the measured value of the main steam flow rate of the flow rate sensor 10 is input to the main steam pressure control device 7.

Reference numeral 12 denotes a governing valve control device, and reference numeral 11 denotes an opening calculator, the functions of which will be described later. Reference numeral 14 denotes an opening sensor for measuring (detecting) the opening of the governing valve 5. Has become. 13 is the row selector 8
, That is, a selector for switching between the control output from the main steam pressure control device 7 or the control device 6 and the output from the governing valve control device 12. Other configurations are the same as those in FIG. 4, and the same members are denoted by the same reference numerals.

Next, the operation of this embodiment will be described with reference to FIGS. When the steam turbine 4 is started,
Steam G is supplied from the waste gas boiler 3 to the steam turbine 4 through the steam supply pipe 15 (step (1)). Thereafter, when the breaker 17 is synchronously turned on and the power system 18 is connected to the power system 18, the generator 16 starts power generation at the same time (step (2)). Operation is performed (step (3)).

During the above-mentioned steady operation, the steam supply pipe 15
Of the steam G flowing through the pipe, that is, the main steam pressure P₁ Is the pressure sensor 9
And input to the main steam pressure control device 7
(Step (4)). In the main steam pressure control device 7,
Is the measured value P of the main steam pressure inputted every moment₁And main steam
Pressure set value P₀ Compare with And this comparison result is
Input to the low selector 8 and the low selector 8
Is P₁≧ P₀  That is, the measured value P of the main steam pressure₁ Is the set value P₀ Higher than
In some cases, another control device 6 operates as in the case of the steady operation.
Select to perform control and control by the other control device 6
Is performed (step (5)).

The main steam pressure P₁ Is the set value P₀ than
Drop, P₁<P₀  , The low selector 8 controls the main steam pressure control.
The control by the device 7 is selected, and the control of the governing valve 5 is
Speed control valve control from the control by the row selector 8
The control is switched to the control by the device 12 (step
(6)).

On the other hand, the main steam amount Q in the steam supply pipe 15
₁ is an opening degree calculator 1 which is measured by the flow rate sensor 10 every moment.
1 (step (7)). The opening calculator 11
In, the optimal opening K _{0 of the} governing valve 5 that can maintain the main steam pressure P ₁ at the set value P ₀ at the measured flow rate Q ₁ is calculated, and this optimal opening K ₀ is transmitted to the governing valve control device 12. It is input (step (8)).

The opening K ₁ of the speed control valve 5 is measured every moment by the opening sensor 14 and input to the speed control valve controller 12 (step (10)). Control valve control device 12
In compares the measured value K ₁ with optimal opening K ₀ of the opening, which receives the output results of control for a constant rate of change in the valve opening selector 13.

Then, as described above, P₁<P₀Become low
The control by the main steam pressure control device 7 is selected by the selector 8.
When selected, the selector 13 is switched to the governing valve control device 12 side.
The opening of the governing valve 5 is transmitted to the governing valve controller 12.
Therefore, the optimal opening K₀ At a constant rate of change with the
(Step (9)). Such tone
The opening control at a constant rate of change by the speed control device 12 is controlled.
The opening of the speed valve 5 is K₁> K₀  (Step (11)).

The measured value of the opening K₁ Is the optimal opening
K₀ When:₁≤K₀  , The output of the main steam pressure control device 7 becomes the maximum at that time.
Suitable opening K₀ (Step (1
2)).

At the same time, the selector 13 is switched to the original position, and this time, from the control by the governing valve control device 12 to the PID control by the main steam pressure control device 7, without a sudden change of the governing valve opening. Transfer (Step (1)
3)). Thus, 5 governor valve, PID control of the main-steam pressure control device 7 which is tracked to the optimum degree of opening K ₀ is made (step (14)).

FIG. 3 shows a comparison of control characteristics of the governing valve opening between the case according to the embodiment of the present invention and the prior art shown in FIG. 5. In FIG. 3, the solid line (A) indicates the case of the present invention. The broken line (B) is the case of the prior art.

As shown in FIG. 3A, the present invention (A)
In line (1), the regulating valve opening degree control at a constant rate of change in the regulating valve control device 12 causes the settling time T ₁ of the regulating valve 5 to be set.
Is significantly shorter than the settling time T ₂ in the prior art, and as a result, as shown in FIG.
The settling time T ₁ ′ of the main steam pressure P ₁ is significantly shorter than the settling time T ₂ ′ in the prior art.

In the above-described embodiment, the optimum opening K ₀ of the governing valve 5 is calculated using the measured value of the main steam flow rate Q ₁ from the flow rate sensor 10. The main steam amount calculated from the subsequent pressure may be used.

[0034]

As described above, according to the present invention, at the time of switching of the governing valve opening control, the governing valve controller shifts the governing valve opening to the optimal opening at a constant rate of change. By performing such control, the settling time is significantly reduced as compared with the related art, and the responsiveness of the steam turbine control can be improved. Further, regarding the adjustment of the control,
Since only adjustment of the rate of change of the governing valve control device needs to be performed, parameter adjustment can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main 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 a comparison diagram of control performance between the embodiment and the conventional technology.

FIG. 4 is a system diagram of a combined gas turbine / steam turbine plant.

FIG. 5 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 6 other control device 7 main steam pressure control device 8 low (LOW) selector 9 pressure sensor 10 flow rate sensor 11 opening calculator 12 speed control valve control device 13 selector 14 opening sensor 15 steam supply Pipe 16 Generator 18 Power system

Claims (5)

[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 method for controlling the steam pressure of a gas turbine, the measurement value (P₁ ) And set value (P₀ ) And
Compare the measured values (P ₁ ) Is the set value (P₀ Less than)
To select the control by the main steam pressure controller.
In the process, the set value (P₀ Said governing that can maintain)
Optimal valve opening (K₀ ) And the measured value of the opening of the governing valve (K₁ )
And the measured value of the opening (K₁ ) Is the optimal opening (K₀ )
While the maximum opening degree is larger than the optimum opening degree (K₀ ) As the target value
Control the rate of change of the governing valve opening to a constant value.
Measured value (K₁ ) Is the optimal opening (K₀ ) The change when
A steam turbine characterized by releasing the constant rate control
Steam pressure control method. 2. The main steam flow rate (Q ₁ ) in the steam supply pipe.
2. The steam pressure control method for a steam turbine according to claim 1, wherein the optimum opening degree (K ₀ ) is calculated based on the flow rate measurement value (Q ₁ ). 3. When the measured value (K ₁ ) of the opening of the governing valve falls below the optimal opening (K ₀ ), the opening of the governing valve output from the main steam pressure control device is controlled. 2. The method according to claim 1, wherein the degree is tracked to the optimum opening (K ₀ ).
The steam pressure control method of the steam turbine according to the above. 4. A steam turbine according to claim 1, wherein said steam turbine is configured to adjust a main steam pressure of said steam turbine by changing an opening of a speed regulating valve provided in a steam supply pipe for supplying main steam to the steam turbine. In the main steam pressure control device, a pressure sensor that measures the main steam pressure, a main steam pressure control device that compares the measured value of the main steam pressure with a set value and outputs a control signal of the governing valve opening degree And, an opening sensor for measuring the opening of the governing valve, and comparing the measured value of the optimal opening and the opening of the governing valve,
While the measured value of the opening degree is larger than the optimal opening degree, a governing valve control apparatus for controlling a constant rate of change of the governing valve opening degree with the optimal opening degree as a target value; A selector for switching the control of the governing valve to the governing valve control device while the governing valve opening is larger than the optimal opening after the control of the governing valve is switched to the pressure control device. A steam pressure control device for a steam turbine. 5. The steam turbine according to claim 4, further comprising: a flow sensor for measuring a flow rate of the main steam; and an opening calculator for calculating the optimum opening based on a flow rate measured by the flow sensor. Steam pressure control device.