JP2892427B2 - Steam turbine controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a steam installed in a combined power plant in which a gas turbine cycle and a steam turbine cycle are connected via an exhaust heat recovery boiler. The present invention relates to a turbine control device.

(Prior Art) The steam cycle of a combined power plant is as shown in FIG. The exhaust heat recovery boiler 1 generates steam by the exhaust heat energy from the gas turbine. The steam generated in the high-pressure drum 2 and the low-pressure drum 3 in the exhaust heat recovery boiler 1 is supplied to the high-pressure steam control valve 5 of the steam turbine 4. And a low-pressure steam control valve 6 to supply the steam to the steam turbine 4. The steam energy is converted into rotational energy of the steam turbine 4, and electricity is output from a generator 7 connected to the steam turbine 4 on the same shaft.

The steam generated by the high-pressure drum 2 and the low-pressure drum 3 is directly condensed by a high-pressure steam bypass valve 8 and a low-pressure steam bypass valve 9 provided before the high-pressure steam control valve 5 and the low-pressure steam control valve 6. It is configured so that it can be supplied to FIG. 5 is a control block diagram of the high-pressure steam control valve 5 and the low-pressure steam control valve 6 of such a steam cycle. The contents of the high and low pressure control blocks are as follows:
Since they are substantially equivalent, they are expressed as control blocks of the steam control valve in FIG. 5 for convenience. Actually, high pressure and low pressure are provided. The control block of the steam control valve is composed of the output signal of the speed controller 11 and the load controller as shown in FIG.
A signal obtained by adding the twelve output signals and an output signal of the load limiter 13 are respectively input to the bottom value selector 14, and the selected signal is used as a steam control valve opening degree setting signal. The load controller 12 passes the deviation between the output signal of the setter 15 and the output signal of the integrator 16 through the rate-of-change limiter 17, inputs the output signal to the integrator 16, and outputs the output signal of the load controller 12. It is configured to be an output signal. The load limiter 13 follows a value obtained by adding a bias signal having a positive polarity to the output signal of the load controller 12, and is not normally selected by the low value selector 14.

The operation of the steam turbine 4 configured as described above is such that, after the gas turbine is started, the inlet damper of the exhaust heat recovery boiler 1 is gradually opened to increase the amount of gas turbine exhaust heat gas entering the exhaust heat recovery boiler 1 and the high pressure drum 2 And the water in the low-pressure drum 3 is gradually evaporated. Thereafter, when the state of the high-pressure steam output from the high-pressure drum 2 becomes a state in which the steam turbine 4 can be started, the output of the speed controller 11 of the high-pressure steam control valve 5 is increased. Thus, when the rated speed is reached,
The generator 7 is incorporated into the power system, and the load controller 12 starts up until the initial load is secured. During the start-up of the steam turbine 4, the high-pressure steam bypass valve 8 and the low-pressure steam bypass valve 9 are controlled so that the outlet pressures of the high-pressure drum 2 and the low-pressure drum 3 are maintained at predetermined values, although not shown. ing. This predetermined value is a value slightly higher than the rated pressure value of the high-pressure drum 2 and the low-pressure drum 3 to ensure that the high-pressure steam bypass valve 8 and the low-pressure steam bypass valve 9 are fully closed after the start of the steam turbine 4. Is set to That is, as the high-pressure steam control valve 5 opens, the outlet steam pressure of the high-pressure drum 2 tends to decrease, and the high-pressure steam bypass valve 8 closes to compensate for this.

When the initial load holding of the steam turbine 4 is completed, the setting device 15 in the load controller 12 of the high-pressure steam control 5 and the low-pressure steam control valve 6 is set to fully open. Then, the output signal of the load controller 12 increases at the change rate set by the change rate limiter 17, and the high-pressure steam control valve 5 and the low-pressure steam control valve 6 gradually open. And when it reaches the full open or equivalent value,
The activation of the steam turbine 4 is completed.

During the load increase of the steam turbine 4, the high-pressure steam bypass valve 8 and the low-pressure steam bypass valve 9 are connected to the outlet steam of the high-pressure drum 2 and the low-pressure drum 3 with the high-pressure steam control valve and the low-pressure steam control valve 6 being opened. It gradually closes to compensate for the pressure drop. And
The high-pressure steam control valve 5 and the low-pressure steam control valve 6 are fully opened or fully closed before reaching a corresponding value.

(Problems to be Solved by the Invention) However, in such a steam turbine control device, the high-pressure steam control valve 5 and the low-pressure steam control valve 6 are fully opened after the high-pressure steam bypass valve 8 and the low-pressure steam bypass valve 9 are fully closed. Alternatively, the outlet steam pressure of the high-pressure drum 2 and the low-pressure drum 3 is not controlled from anywhere until the pressure reaches the equivalent value, so that the high-pressure steam control valve 5 and the low-pressure steam control valve 6 are not controlled.
With the opening, the pressure gradually decreased from a value slightly higher than the rated pressure value. The timing at which the high-pressure steam bypass valve 8 and the low-pressure steam bypass valve 9 are fully closed depends on the start-up progress state of the exhaust heat recovery boiler 1.
Since the outlets of the high-pressure drum 2 and the low-pressure drum 3 are fully closed early in order to maintain the steam pressure, uncontrolled time is long.

That is, depending on the state of the exhaust heat recovery boiler 1, the outlet pressure of the high-pressure drum 2 or the low-pressure drum 3 may drop abnormally or suddenly. When such a state occurs, disturbance of the water level control of the high-pressure drum 2 and the low-pressure drum 3 that controls the water levels of the high-pressure drum 2 and the low-pressure drum 3 by adjusting the supply water flow rate (not shown) may occur. The water level becomes abnormally high,
There was a problem that it became abnormally low. If the drum water level becomes abnormally high, the steam tends to become wet, and the blades of the steam turbine 4 may be damaged. Therefore, it is necessary to stop the steam turbine 4 urgently. If the drum water level becomes abnormally low, Since the high-pressure drum 2 or the low-pressure drum 3 is empty, it is necessary to shut off the heat input to the exhaust heat recovery boiler 1 and stop the steam turbine 4.

According to the present invention, after the high-pressure steam bypass valve 8 or the low-pressure steam bypass valve 9 is fully closed, the load of the steam turbine 4 is increased in accordance with the start-up progress state of the exhaust heat recovery boiler 1, and
It is an object of the present invention to provide a steam turbine control device capable of performing a stable operation of a steam cycle by suppressing when the state of the exhaust heat recovery boiler 1 becomes abnormal.

[Structure of the Invention] (Means for Solving the Problems) The steam turbine control device of the present invention operates the steam control valves 5 and 6 such that the steam turbine 4 has a rated rotation speed when the steam turbine 4 is started. Speed control means 11 for adjusting the opening,
When the steam turbine 4 is started, steam bypass valve control means for adjusting the opening of the steam bypass valves 8, 9 so as to maintain the steam pressure from the exhaust heat recovery boiler 1 at a predetermined value, and the steam turbine 4 After that, the generator 7 is inserted into the power system and the opening of the steam control valves 5 and 6 is adjusted to secure the initial load. After the initial load is secured, the steam control valves 5 and 6 are opened. The first load control means 12A for controlling the opening so that the degree is fully opened or equivalent to the fully opened state, and after the steam bypass valves 8 and 9 are fully closed, a predetermined increase or decrease according to the increase or decrease of the steam pressure from the exhaust heat recovery boiler 1. A second load control means 12B for adjusting the opening of the steam control valve by increasing or decreasing the opening set value at a predetermined rate.

Further, in the steam turbine control device, when the rate of change of steam pressure from the exhaust heat recovery boiler exceeds a predetermined value,
The predetermined change rate of the second load control means is set to be larger than the predetermined change rate.

(Operation) When the steam bypass valves 8 and 9 are fully closed before the steam control valves 5 and 6 reach full open under the control of the first load control means 12A after the start of the steam turbine 4, the first Load control means 1
In place of the control by step 2, the second load control means 12B increases or decreases the opening set value at a predetermined rate of increase or decrease according to the increase or decrease of the steam pressure from the exhaust heat recovery boiler 1 to adjust the opening of the steam control valve. Switch to the next control.

As a result, after the steam bypass valve is fully closed, the steam opening / closing valve is controlled by increasing / decreasing the opening degree at a predetermined increase / decrease rate in accordance with an increase or decrease in the steam pressure from the exhaust heat recovery boiler.
Stable control can be performed according to the start-up progress state of the exhaust heat recovery boiler.

Example An example of the present invention will be described below. FIG. 1 is a block diagram showing a steam control valve control block according to the present invention. In FIG. 1, the same reference numerals are given to the same or corresponding parts as those in the conventional example shown in FIG. 5, and description thereof will be omitted. The difference from the conventional example is that the function of the conventional load controller 12 is used as a first load control means 12A and a second load control means 12B is newly provided. That is, the second load control means 12B is provided, an actual measurement signal of the steam pressure at the exhaust heat recovery boiler outlet is input, and a deviation between this value and the output signal of the integrator 18 is input to the change rate limiter 19 and output. The signal is input to the integrator 18, and the output signal is set as a pressure set value, a deviation signal between the pressure set value and an actual measurement signal of the exhaust heat recovery boiler outlet steam pressure, and output from the change rate controller 17. And the signal to be performed is switched by the switch 20. This configuration is substantially the same for the high-pressure steam control valve 5 and the low-pressure steam control valve 6, and is actually provided for each. The outlet steam pressure of the exhaust heat recovery boiler 1 is a high pressure drum outlet steam pressure in the case of the high pressure steam control valve 5, and is a low pressure boiler outlet steam pressure in the case of the low pressure steam control valve 6.

With the above configuration, if the high-pressure steam bypass valve 8 or the low-pressure steam bypass valve 9 is fully closed before the high-pressure steam control valve 5 or the low-pressure steam control valve 6 reaches the full open after the steam turbine is started, the switch 20 is turned on. Is switched from the output signal of the change rate limiter 17 to a deviation signal between the pressure set value and the actually measured pressure signal. As a result, the second load control means 12
The function of B is utilized. Now, when the steam pressure at the exhaust heat recovery boiler outlet gradually increases with the start-up of the exhaust heat recovery boiler 1, the output signal of the integrator 18 which is the pressure set value increases by the delay time of the integrator 18. The delay and the deviation signal from the measured pressure signal become a plus signal. For this reason, the plus signal is input to the integrator 16, the output signal of the integrator 16 increases, and the opening / closing valve opening also increases. When this state continues, the high-pressure steam control valve 5 or the low-pressure steam control valve 6 reaches the full open state, and the startup of the steam turbine is completed.

On the other hand, assuming that the steam pressure at the exhaust heat recovery boiler outlet suddenly drops after the high-pressure steam bypass valve 8 or the low-pressure steam bypass valve 9 is fully closed, the input signal of the rate-of-change limiter 19 becomes a large value on the minus side. Therefore, the negative limit value of the change rate limiter 19 is exceeded. In this case, the input signal of the integrator 18 becomes the negative limit value of the change rate limiter 19,
The decrease of the output signal of the integrator 18 is greatly delayed as compared with the decrease of the measured pressure signal. For this reason, the integrator 18
The deviation between the output signal and the measured pressure signal becomes a large value on the negative side, and the output signal of the integrator 16 is rapidly lowered to rapidly close the control valve. Thereby, it is possible to suppress a sudden decrease in the steam pressure at the exhaust heat recovery boiler outlet. When the steam pressure at the exhaust heat recovery boiler outlet suddenly rises, the reverse action is taken, and the sudden rise can be achieved.

As described above, after the high-pressure steam bypass valve 8 or the low-pressure steam bypass valve 9 is fully closed, the steam turbine can be controlled according to the start-up progress state of the exhaust heat recovery boiler 1,
Further, even when the startup state of the exhaust heat recovery boiler 1 becomes abnormal and the outlet steam pressure changes suddenly, it is possible to suppress the sudden change. Next, FIG. 2 is a block diagram showing a steam control valve control block showing another embodiment of the present invention. The difference from FIG. 1 is that the measured signal of the steam pressure at the exhaust heat recovery boiler outlet is input to the differentiator 21, the output signal is input to the function generator 22, and the output signal and the rate-of-change limiter The difference is that the output signal of 17 is switched by the switch 20. FIG. 3 shows a function characteristic indicating the relationship between the input and output of the function generator 22. With this configuration, the rate of change of the measured signal of the steam pressure at the outlet of the exhaust heat recovery boiler is changed to the point A or B in FIG.
If it does not exceed the point, the control valve is slowly moved, and if it exceeds the point A or B, the control valve is rapidly moved. In this embodiment, the same effects as those of the embodiment shown in FIG. 1 can be obtained.

[Effects of the Invention] As described above, according to the present invention, after the start of the steam turbine, the high-pressure steam bypass valve or the low-pressure steam bypass valve is fully closed before the high-pressure steam control valve or the low-pressure steam control valve reaches full open. In this case, since the load of the steam turbine is increased in accordance with the state of the subsequent start signal of the exhaust heat recovery boiler 1, stable control can be performed. In addition, when the startup state of the exhaust heat recovery boiler becomes abnormal and the outlet steam pressure changes suddenly, the second load control means operates to suppress the sudden change, so that a stable operation of the steam cycle is performed. be able to. That is, it is possible to prevent the steam turbine from being stopped due to an abnormally high or low water level of the high-pressure drum or the low-pressure drum.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing one embodiment of the present invention,
FIG. 2 is a control block configuration diagram showing another embodiment of the present invention, FIG. 3 is a characteristic diagram showing characteristics of the function generator of the present invention, and FIG. 4 is a configuration diagram showing a configuration of a combined power plant. FIG. 5 is a block diagram showing a conventional example. 1 ... waste heat recovery boiler, 2 ... high pressure drum, 3 ... low pressure drum, 4 ... steam turbine, 5 ... high pressure steam control valve,
6 Low pressure steam control valve, 7 Generator, 8 High pressure steam bypass valve, 9 Low pressure steam bypass valve, 10 Condenser, 11 Speed controller, 12 Load controller , 13 ... Load limiter, 14 ... Low value selector, 15 ... Setter, 16 ... Integrator, 17 ... Change rate limiter, 18 ... Integrator, 19 ... Change rate limiter 20 switches, 21 differentiators, 22 function generators.

Claims (2)

(57) [Claims] 1. A gas turbine cycle and a steam turbine cycle are connected via a heat recovery steam generator, a steam control valve for guiding steam from the heat recovery steam generator to a steam turbine, and steam from the heat recovery steam generator. In a steam turbine control device that controls the steam turbine to which a generator is connected by adjusting a steam bypass valve for bypassing the steam turbine to a condenser, when the steam turbine is started, the steam turbine has a rated speed and Speed control means for adjusting the opening degree of the steam control valve so that the steam pressure from the exhaust heat recovery boiler is maintained at a predetermined value when the steam turbine is started. Steam bypass valve control means for adjusting the steam turbine, and after the steam turbine reaches the rated speed, the generator is incorporated into a power system to secure an initial load. A first load control unit that adjusts the opening of the steam control valve and, after securing the initial load, controls the opening of the steam control valve to be fully opened or equivalent to fully opened; A second load control means for adjusting the opening of the steam control valve by increasing or decreasing the opening degree at a predetermined rate according to the increase or decrease of the steam pressure from the exhaust heat recovery boiler after closing. A steam turbine control device, characterized in that: 2. When the rate of change in steam pressure from the exhaust heat recovery boiler exceeds a predetermined value, the predetermined rate of change of the second load control means is set to be greater than the predetermined rate of change. The steam turbine control device according to claim 1, wherein: