JPH01114797A - Speed controller for steam turbine - Google Patents

Abstract

PURPOSE:To enable the continuous operation of a nuclear reactor without shutdown at the time of an increase in sea water temp. or decrease in the vacuum degree of a condenser by maintaining a desired bias value at all times between a speed request signal and the output of a pressure controller for controlling a regulating valve. CONSTITUTION:A turbine speed governor 27 corrects the change in a turbine speed deviation signal 26a in association to a load set value and outputs the same as a turbine speed governor output signal 27a to an adder 28. The adder 28 adds the signal 27a and the load set signal 29a of a load setter 29 and outputs the result thereof as the speed request signal 28a to an adder 34. The correction output signal 39b from a speed request corrector 30 is inputted to the adder 34 and is computed. The corrected speed request signal 30a is then inputted to a low value preferential circuit 31. The pressure request signal 32a from a pressure setter 32 for controlling the pressure of the reactor to the constant pressure is also inputted to the circuit 31. The circuit 31 outputs the low value signal of these two signals 30a, 32a as a regulating valve opening degree request signal 31a to the steam regulating valve. The corrector 30 functions to maintain the constant and adequate bias value at all times between the output 32a and the signal 30a.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) TECHNICAL FIELD This invention relates to steam turbine speed control systems.

(Prior Art) Generally, in a steam turbine plant such as a boiling water atomic coupler plant, a generator directly connected to a steam turbine is electrically connected directly to a power system via a circuit breaker. Therefore, when frequency fluctuations occur in the power system,
The rotational speed of the generator fluctuates as a result of this.

In other words, when a failure such as a transmission line accident occurs in the power system, the balance between the total power generation of the generators connected to the power system and the power consumption of the users is disrupted, resulting in frequency fluctuations. This causes fluctuations in the rotational speed of generators that are electrically connected directly to the power grid. Therefore, the steam turbine speed control device operates in accordance with this variation in rotational speed to control the opening degree of the steam control valve, thereby controlling the amount of steam flowing into the steam turbine. As a result, the steam generated in the reactor is not consumed smoothly, and the pressure in the reactor fluctuates.

However, this pressure fluctuation in the reactor is undesirable for boiling water reactors because it causes fluctuations in the reactor output.In particular, as the pressure increases, the reactor output increases, and if the limit value is exceeded, the reactor The operation of the power station will be automatically stopped, and the operation of the power plant will be stopped.

Therefore, conventionally, a bypass conduit has been branched from the main steam conduit for guiding a part of the main steam to the condenser by bypassing the turbine from the middle of the main steam conduit.

That is, as shown in FIG. 5, steam generated in the nuclear reactor 11 passes through the main steam pipe 12 and is guided to the steam turbine 14 while its flow rate is controlled by the steam control valve 13, where it is rotated by the steam turbine 14. Ru. A generator 15 directly connected to the steam turbine 14 is driven, and the generated power is sent to the power system via a circuit breaker 16. On the other hand, the steam that has done work in the steam turbine 14 is sent to the condenser 17,
There, the water is condensed.

In addition, a bypass conduit 19 having a bypass valve 18 is branched out from the upstream side of the steam control valve 13 in the main steam pipe 12, and a part of the main steam is routed to the steam turbine 14 as necessary.
is formed so as to bypass and lead to the condenser 17.

On the other hand, a frequency detector 20 for measuring the power system frequency is provided at the outlet of the circuit breaker 16 to the power system, and a frequency signal 20a detected by this frequency detector 20 is input to a comparator 21, where It is compared with a preset frequency setting value. When the frequency signal 20a exceeds the frequency setting value, the comparator 21 transfers the output signal 21a to the adder 2.
Issued on 2. This adder 22 outputs a deviation signal 22a between the output signal 21a and the output signal 23a of the load setting device 23 to decelerate the recirculation pump 24, reduce the output of the reactor 11, and reduce the amount of steam generated. It is formed. The setting value of this load setting device 23 has the purpose of eliminating disturbances to the plant due to minute changes in the system frequency, and is normally set to a value 10% higher than the required load. Further, the opening degree of the steam control valve 13 is controlled by a steam turbine speed control device (not shown) so that the deviation between the actual turbine speed and the set speed is within a certain range. The amount of steam flowing into the steam turbine 14 is adjusted.

In addition, in response to the control of the steam control valve 13 in the closing direction, the bypass valve 18 is controlled in the opening direction, and excess steam is transferred to the condenser 17.
guided by.

However, generally the steam capacity that can flow through the bypass valve 18 is
It is about 25% of the volume tloO% of the steam control valve 13. Therefore, when the frequency of the power system increases significantly, when the opening degree of the steam regulating valve 13 is significantly reduced to prevent the rotation speed from increasing, even if the opening degree of the steam regulating valve 13 is within 25%. For example, excess steam can be absorbed by a bypass valve 18 with a capacity of 25%,
A rise in reactor pressure can be prevented. However, if a frequency increase occurs that causes the steam control valve 13 to be throttled by 25% or more, the steam control valve 13 will be throttled beyond the capacity of the bypass valve 18, causing an increase in reactor pressure and reducing the reactor output. There are problems such as the nuclear reactor 11 automatically stopping due to the rise.

The amount of increase in frequency and the amount of throttling of the steam control valve 13 are determined by the speed adjustment rate in the steam turbine speed control device, and currently the speed adjustment amount is 5%. That is, when the actual turbine speed increases by 5%, the steam control valve 13 increases by 10%.
It is supposed to be throttled down by 0%, and a 5% increase in the actual turbine speed becomes 52.5Hz when converted to 507.

FIG. 6 is a diagram showing the relationship between the frequency and the opening degree of the steam control valve at a speed regulation rate of 5%. Here, if the limit of increase in frequency that can be absorbed by the bypass valve 18 is determined, the above-mentioned load setting bias 10 Considering the percentage, it becomes 50.8757.

On the other hand, the opening degree of the regulating valve during rated output operation is not necessarily constant at 100%, but fluctuates by several percentage points due to changes in seawater temperature and condenser vacuum level, so it is not recommended to maintain the load setting bias at 10%. It becomes better.

For this reason, for example, if the bias becomes less than 10%, the 50.87
When a frequency increase of 5 Hz occurs, the control valve is throttled by 25% or more, and the reactor pressure increases due to a mismatch with the bypass capacity, potentially leading to high reactor pressure or high neutron flux scram.

(Problems to be solved by the invention) The present invention has been made in consideration of these points,
While using the current bypass valve, by providing a circuit that generates a constant correction signal for the control valve opening request signal of the reactor power control device, it is possible to reduce the frequency of the power system when the seawater temperature rises or the condenser vacuum level decreases. An object of the present invention is to provide a steam turbine speed control device that allows a nuclear reactor to operate continuously without stopping even if the frequency increases to about 50,875 Hz.

[Structure of the invention]

(Means for Solving the Problems) A steam turbine control device of the present invention provides a turbine speed governor that corrects a change in an input turbine speed deviation signal in relation to a load setting value and outputs it as a turbine speed governor output signal. The vessel and
A load setter that outputs a load setting signal, an adder that calculates the deviation between the turbine governor output signal and the load setting signal and outputs a speed request signal, and a pressure that controls the speed request signal and the control valve. It is characterized by the provision of a speed request signal compensator to ensure that a constant and appropriate bias value is always maintained between the controller output and the frequency rise up to a specified frequency that is considered in the design. This prevents scrums from occurring unnecessarily.

(Example) FIG. 1 is a block diagram according to the present invention.

The speed setter 25 is configured to output a speed setting signal 25a to an adder 26. This adder 26 is configured to compare the speed setting signal 25a and the actual speed signal a of the steam turbine, and output a turbine speed deviation signal 26a, which is a deviation signal thereof, to the turbine speed governor 27. This turbine speed governor 27 receives a turbine speed deviation signal 26a.
The speed regulation rate is corrected so that a 5% change in the load setting value corresponds to a 100% change in the load setting value, and the corrected value is output to the adder 28 as the turbine governor output signal 27a.

This adder 28 is configured to add the turbine governor output signal 27a and the load setting signal 29a of the load setting device 29 and output the result to the adder 34 as a speed request signal 28a. This adder 34 includes a speed request signal corrector 3.
The corrected output signal 30b from 0 is input and calculated, and the corrected speed request signal 30a is input to the low value priority circuit 31.

A pressure request signal 32a output from a pressure controller 32 for controlling the pressure of the nuclear reactor 11 to be constant is also input to the low value priority circuit 31.

This low value priority circuit 31 connects the two signals 30a and 32
The low value signal of a is output as a control valve opening request signal 31a for the steam control valve 13.

The opening degree of the steam control valve I3 is controlled by this signal 31a. Further, the pressure request signal 32a output from the pressure controller 32 is also applied to the adder 33.

This adder 33 is configured to compare the pressure request signal 32a and the adjustment valve opening request signal 31a and output the difference signal as a bypass valve opening request signal 33a. The opening degree of the bypass valve 18 is controlled by this bypass valve opening degree request signal 33a.

The speed request signal corrector 30 inputs the speed request signal 28a and the pressure regulator output 32a, and outputs a signal 30c obtained by further subtracting the load setting bias 30d from the deviation to the hold circuit 30A (for example, with a large time constant of 1000 seconds or more). The bias portion of the pressure controller output 32a, which normally controls the castle valve, and the corrected speed request signal 30a is input to the load setting bias value 30d (usually 10%).
), the corrected output signal 30b is output.

FIG. 2, FIG. 3, and FIG. 4 are explanatory diagrams of transient response of the steam control valve, etc. when the system frequency increases in the apparatus of the present invention.

FIG. 2 shows the frequency of the power system, FIG. 3 shows the opening degrees of the steam control valve and bypass valve, and FIG. 4 shows the time changes in the reactor output.

As shown in Figure 2, if the frequency rises from the set frequency of 50° to 50°, 8751° in about 1 second and then maintains that value, as the frequency rises, the actual speed of the bin increases and the speed demand increases. Since the signal 28a becomes smaller and the pressure request signal 32a remains almost constant at 100%,
The speed request signal 28a becomes the control valve opening request signal 31a through the low value priority circuit 31, and the steam control valve gradually becomes quiet as shown in FIG. (The degree of opening is % of the flow rate.) Then, when the frequency reaches 50.875 Hz, the steam control valve 13 is in a state where it is narrowed down by 25%. On the contrary, the bypass valve 18 opens in accordance with the amount of restriction of the steam adjustment valve 13, and since the capacity of the bypass valve 18 is 25% of the capacity of the steam adjustment valve 13, when the steam adjustment valve 13 is restricted by 25%. It will be fully opened. Operation will continue in this state.

In the above explanation, it is assumed that the load setting bias is 10% as designed, but this bias is caused by changes in the adjustment valve opening degree (changes in pressure regulator output) due to changes in seawater temperature and condenser vacuum level.
Therefore, if it is less than 10%, for example about 5%, the behavior will be as shown by the broken line in FIG.

That is, in this case, the throttle valve starts narrowing down a little earlier as shown in FIG. 3, and the throttle amount at 50.875 Hz also increases by 5% to about 30%. As a result, a mismatch with the bypass capacity occurs, and as shown by the broken line in FIG. 4, the reactor output increases as the reactor pressure increases, causing the reactor to scram.

However, in the present invention, this load setting bias is always corrected to be 10%, so a scram does not occur.

〔Effect of the invention〕

Since the steam turbine speed control device of the present invention is configured and operates in this way, when the frequency of the power system increases, in a steam turbine plant having a partial capacity bypass valve, the speed control device of the present invention can absorb Even if the seawater temperature, condenser vacuum level, etc. fluctuate due to the frequency increase, it is possible to prevent the plant from immediately shutting down. As a result, even if the frequency rises to the extent that occurs when an accident occurs in a normal power system, the plant will not have to stop, and the plant can continue to operate while waiting for the frequency to recover with the bypass valve fully open. This has effects such as being able to improve the rate.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the steam turbine speed control device according to the present invention, FIG. 1 is a block diagram showing the whole, FIG. 2 is a frequency characteristic diagram when the frequency increases, and FIG. is a characteristic diagram of the opening degrees of the control valve and bypass valve, Figure 4 is a characteristic diagram showing temporal changes in reactor output, Figure 5 is a system diagram of a conventional nuclear turbine plant, and Figure 6 is a diagram of a conventional steam FIG. 3 is a diagram showing the relationship between frequency change and steam control valve opening degree in a turbine speed control device. 13...Steam control valve, 14...Steam turbine, 1
8... Bypass valve, 26a... Turbine speed deviation signal, 27... Turbine governor, 27a...
Turbine governor output signal, 28... adder,
28a...Speed request signal. 29a... Load setting signal, 30a... Correction speed request signal (operation signal), 30b... Correction output signal (operation signal), 3OA... Hold circuit, 31
...Low value priority circuit, 31a...Adjustment valve opening request signal. Agent Patent Attorney Noriyuki Ken Chika Daishimaru (Seconds) Figure 2: Time (Seconds) Figure 3: Time (#) Figure 5: Frequency (Hz)

Claims (3)

[Claims] (1) a turbine governor that corrects a change in an input turbine speed deviation signal in relation to a load setting value and outputs it as a turbine governor output signal; and a load setter that outputs a load setting signal; an adder that calculates the deviation between the turbine speed governor output signal and the load setting signal and outputs a speed request signal; and a speed so that the content of the speed request signal is equal to the pressure controller output and always maintains an appropriate bias value. A steam turbine speed control apparatus having a demand signal corrector. (2) The steam turbine speed according to claim 1, wherein the speed request signal corrector is capable of always maintaining a constant bias value between the speed request signal and the pressure controller output in a steady state. Control device. (3) The output signal of the speed request signal corrector does not follow short-term fluctuations in the speed request signal or pressure controller output;
2. The steam turbine speed control device according to claim 1, further comprising a hold circuit so as to follow only slow, long-term fluctuations due to changes in condenser vacuum level, etc.