JPH033041B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a steam turbine pressure control system that controls a steam turbine inlet steam pressure and its back pressure by adjusting a steam control valve provided between a boiler and a steam turbine. Regarding a control device.

[Technical background of the invention]

The inlet steam pressure of steam turbines used in large-scale plants such as thermal power plants and the degree of vacuum in the condenser as back pressure must be maintained approximately constant even when the generator load fluctuates. .

For this reason, when the generator load increases, the turbine governor in this system detects the increase in load and opens the steam control valve wide, while the boiler detects a decrease in steam pressure and reduces the amount of fuel and water feed. increase

However, although the steam control valve opens instantaneously in response to an increase in load, it is difficult to instantaneously increase the amount of steam in the boiler, and due to the difference in response speed, the inlet steam pressure of the steam turbine and its There were fluctuations in back pressure.

As is well known, when the steam pressure at the steam turbine inlet decreases, this causes drain generation, which adversely affects the turbine impeller and shortens the life of the plant, increasing the back pressure of the steam turbine. In this case, the windage loss of the long turbine blades increases, the life of the turbine blades is shortened due to thermal stress caused by frictional heat, and the condenser is also adversely affected.

In order to solve this problem, for example, a pressure control device is used that detects the steam pressure upstream of the main steam stop valve and the pressure of the condenser and controls the steam control valve based on these detected values.

FIG. 1 is a block diagram showing the configuration of a pressure control device together with a system diagram of a general power generation plant. Here, the steam generated from the boiler 1 is sent to the high-pressure turbine 4 via the main steam stop valve 2 and the steam control valve 3, and after giving a part of the energy contained in this steam to the turbine blades, the steam is returned to the boiler 1. is sent to the reheater 1A.

The steam sent to the reheater 1A is reheated here, and then supplied to the intermediate pressure turbine 6 via the intercept valve 5, and then the low pressure turbine 7.
The thermal energy of the steam is supplied to the turbine blades.

Next, the steam flowing out of the low-pressure turbine 7 is sucked into the vacuum condenser 8, where it is condensed by heat exchange with cooling water, and then sent to the boiler 1 by the feed water pump 9. repeat the cycle.

On the other hand, the steam pressure upstream of the main steam stop valve 2, which is assumed to be approximately proportional to the steam pressure at the steam turbine inlet, is detected by the pressure detector 15, and the internal pressure of the condenser 8 is detected by the pressure detector 16. The detected pressure signal is taken into the pressure control section 10, and a control signal processed there is applied to the steam control valve 3 via the signal amplifier 17.

Thus, the pressure detectors 15 and 16, the pressure control section 10, and the signal amplifier 17 constitute a pressure control device.

FIG. 2 is a block diagram showing the configuration of the pressure control section 10 described above, which includes a pressure setting device 11A that outputs a signal of a type matching the output signal of the pressure detector 15 in order to set the steam pressure at the steam turbine inlet; A pressure displacement converter 12A that compares the output signals of the pressure detector 15 and the pressure setting device 11A with each other and converts them into a displacement request signal according to the pressure deviation, and a displacement width amplification cylinder 13A that amplifies this displacement request signal. a pressure setting device 11B that outputs a type of signal commensurate with the output signal of the pressure detector 16 in order to set the internal pressure of the condenser, a pressure detector 16, and a pressure setting unit. Vessel 11
A pressure displacement converter 12 that compares the output signals of B with each other and converts them into a displacement request signal according to the pressure deviation.
B, and a second control amount calculation section consisting of a displacement width amplification cylinder 13B for amplifying this displacement request signal, and the output signals of these first and second control amount calculation sections, that is, the displacement amplification cylinder 13A.
and a high value priority circuit 14 which compares the output signals of the output signals 13B and 13B and outputs one of the signals having a higher level. Therefore, when the steam pressure at the steam turbine inlet and the pressure in the condenser differ from the set pressure, the displacement request signal with the larger deviation is output from the pressure control section 10 and is applied to the signal amplifier 17.

In this case, the signal amplifier 17 is a hydraulic pilot, a relay, or the like, and controls the lift value of the steam control valve 3 in response to the displacement request signal.

Thus, the steam pressure at the steam turbine inlet and its back pressure are controlled to the set pressure.

[Problems with background technology]

In such conventional steam turbine pressure control devices, since a hydraulic cylinder is used in the pressure control section, even if faster response is required, this cannot be met. If either the inlet steam pressure or the condenser pressure deviates significantly from the set value, the deviation is directly applied to the steam control valve, causing a temporary large disturbance in the control system. There was a drawback.

[Purpose of the invention]

The present invention was made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a pressure control device for a steam turbine that can improve responsiveness and stabilize the control system.

[Summary of the invention]

In order to achieve the above object, the steam turbine pressure control device of the present invention includes a first differential pressure calculation unit that compares a detected value and a set value of the inlet steam pressure of the steam turbine and outputs a pressure deviation signal; a second differential pressure calculation section that compares the detected value and the set value of the back pressure of the steam turbine and outputs a pressure deviation signal; It is equipped with a high value priority circuit that outputs a signal, and a level limiting circuit that maintains the output signal level of this high value priority circuit within a predetermined level range, and is configured to control a steam regulating valve based on the output signal of this level limiting circuit. It is characterized by its composition.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 3 shows a schematic configuration of a steam turbine pressure control device according to the present invention, together with a system diagram of a power generation plant to which this pressure control device is applied, and shows the elements shown in FIG. The same elements are given the same reference numerals and their explanations will be omitted.
Further, in place of the pressure control section 10 shown in FIG. This embodiment differs from FIG. 1 in that a signal amplifier 18 having the following characteristics is used.

Next, FIG. 4 is a block diagram showing the detailed configuration of the arithmetic unit 20, which includes an A/D converter 21A that converts the output signal of the pressure detector 15 into a digital signal, and an A/D converter 21A that sets the steam pressure at the steam turbine inlet. a pressure setting device 22A that outputs a digital signal by;
A differential pressure calculation unit 20a includes a comparison circuit 23A that compares the outputs of the A/D converter 21A and the pressure setting device 22A and outputs a signal according to the deviation, and converts the output signal of the pressure detector 16 into a digital signal. A/D converter 21B that outputs a digital signal by setting the back pressure of the steam turbine, a pressure setter 22B that outputs a digital signal by setting the back pressure of the steam turbine, and compares the outputs of the A/D converter 21B and pressure setter 22B and calculates the deviation. a differential pressure calculation section 20b comprising a comparison circuit 23B that outputs a corresponding signal; a high value priority circuit 24 that compares the output signal levels of the differential pressure calculation sections 20a and 20b and outputs a signal with a higher level; It is comprised of a level limiting circuit 25 that maintains the output signal level of the high value priority circuit within a predetermined range. The level limiting circuit 25 includes an upper limit setting device 25a and a lower limit setting device 25b, as shown in FIG. 5, and is capable of arbitrarily determining the output fluctuation range of the high value priority circuit 24.

The operation of the steam turbine pressure control device of the present invention configured as described above will be explained below.

First, the pressure detector 15 detects the pressure on the upstream side of the main steam stop valve 2 and sends an analog signal substantially corresponding to the inlet steam pressure of the steam turbine to the arithmetic unit 2.
Add to 0. The pressure detector 16 detects the internal pressure of the condenser 8 and applies an analog signal corresponding to the back pressure of the steam turbine to the arithmetic unit 20.

Next, the output signal of the pressure detector 15 is converted into a digital signal by the A/D converter 21A, and then compared with the output signal of the pressure setting device 22A by the comparison circuit 23A, and the deviation is determined as a high value. The signal is input to the priority circuit 24. That is, the differential pressure calculation section 20a
compares the detected value and set value of the steam turbine inlet steam pressure and outputs a pressure deviation signal.

Similarly, the output signal of the pressure detector 16 is converted into a digital signal by the A/D converter 21B, and then compared with the output signal of the pressure setting device 22B by the comparator circuit 23B, and the deviation is determined as a high value. The signal is input to the priority circuit 24. That is, the differential pressure calculation section 20b
compares the detected value and set value of steam turbine back pressure and outputs a pressure deviation signal.

Next, the high value priority circuit 24 applies the higher level pressure deviation signal among these pressure deviation signals to the level limiting circuit 25 .

Here, the level limiter circuit 25 includes the upper limit enactor 2
5a and a lower limit setter 25b to suppress the level of the pressure deviation signal within a range determined by the lower limit setter 25b,
The level range is appropriately determined so as not to disturb the control system even if the signal level rapidly changes from the upper limit to the lower limit or from the lower limit to the upper limit.

Next, the digital signal output from the level limiting circuit 25 is converted into an analog signal within the signal amplifier 18, and a control signal obtained by amplifying this analog signal is applied to the steam control valve 3.

Since the lift value of the steam control valve 3 is determined, control to bring the steam turbine inlet steam pressure and back pressure close to the set values is performed quickly and stably.

In the above embodiment, the arithmetic unit 20 constructed of integrated circuit components and the like has been described, but the same control as described above can be performed using a computer or a microcomputer.

Alternatively, the configuration is not limited to processing digital signals, but it is also possible to perform the same control as described above by processing all analog signals.

〔Effect of the invention〕

As is clear from the above description, in the steam turbine pressure control device of the present invention, the system for controlling the steam control valve based on the signal from the pressure detector is composed of an integrated circuit component or a microcomputer, and, Since it is equipped with a level limiting circuit, it has superior responsiveness compared to conventional devices that drive hydraulic cylinders, and also allows for accurate and stable pressure control without the risk of disturbing the control system. Therefore, reliability can be improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of a conventional steam turbine pressure control system together with a system diagram of a power generation plant to which it is applied, and Figure 2 is a block diagram showing the detailed configuration of this pressure control system. , FIG. 3 is a block diagram showing the configuration of one embodiment of the steam turbine pressure control device according to the present invention, together with a system diagram of a power generation plant to which it is applied, and FIGS. FIG. 2 is a block diagram showing the detailed configuration of a pressure control device. 1...Boiler, 2...Main steam stop valve, 3...Steam control valve, 4...High pressure turbine, 5...Intercept valve, 6...Intermediate pressure turbine, 7...Low pressure turbine, 8...Condensing water Container, 9...Water pump, 10...
...Pressure control section, 11A, 11B, 22A, 22B
...Pressure setting device, 12A, 12B...Pressure displacement converter, 13A, 13B...Displacement amplification cylinder,
14, 24... High value priority circuit, 15, 16... Pressure detector, 17, 18... Signal amplifier, 20...
Arithmetic device, 20a, 20b...Differential pressure computing section, 21
A, 21B...A/D converter, 23A, 23B...
... Comparison circuit, 25 ... Level limit circuit.

Claims (1)

[Claims] 1. In a steam turbine pressure control device that controls an inlet steam pressure of the steam turbine and its back pressure by adjusting a steam control valve provided between a boiler and a steam turbine, a detected value of the inlet steam pressure of the steam turbine and a first differential pressure calculation unit that compares a set value and outputs a pressure deviation signal, and a second differential pressure calculation unit that compares the detected value of the back pressure of the steam turbine and the set value and outputs a pressure deviation signal. and a high value priority circuit that compares the pressure deviation signals of these differential pressure calculation units and outputs a signal with a higher level, and a level limiting circuit that maintains the output signal level of this high value priority circuit within a predetermined level range. A pressure control device for a steam turbine, characterized in that the steam turbine control valve is controlled based on an output signal of the level limiting circuit.